Q.1 Which ISO standard specifically defines the evaluation of the biocompatibility of medical devices?
ISO 9001
ISO 10993-1
ISO 14001
ISO 13485
Explanation - ISO 10993‑1 outlines the principles and guidelines for evaluating the biocompatibility of medical devices, including tests for cytotoxicity, sensitization, and irritation.
Correct answer is: ISO 10993-1
Q.2 In the context of biomaterials, what does the term "cytotoxicity" refer to?
The ability of a material to conduct electricity
The tendency of a material to cause cell death or inhibit cell growth
The mechanical strength of the material
The magnetic properties of the material
Explanation - Cytotoxicity measures the adverse effects of a material on cell viability, often assessed using assays such as MTT or Live/Dead staining.
Correct answer is: The tendency of a material to cause cell death or inhibit cell growth
Q.3 Which assay is most commonly used to assess cell metabolic activity as an indicator of cytotoxicity?
ELISA
MTT assay
Western blot
PCR
Explanation - The MTT assay measures the reduction of MTT tetrazolium salt to formazan by mitochondrial enzymes, reflecting viable metabolic activity.
Correct answer is: MTT assay
Q.4 A biomaterial that releases ions which can stimulate nerve regeneration is considered:
Bioinert
Bioactive
Biodegradable
Brittle
Explanation - Bioactive materials interact with the surrounding tissue, often releasing ions or molecules that promote specific biological responses such as nerve regeneration.
Correct answer is: Bioactive
Q.5 Which of the following is a primary cause of metal ion release from implanted electrical electrodes?
Thermal expansion
Corrosion due to body fluids
Magnetic resonance imaging
Ultrasonic cleaning
Explanation - Implanted metals are exposed to electrolytic body fluids, leading to corrosion and possible release of metal ions, which can affect biocompatibility.
Correct answer is: Corrosion due to body fluids
Q.6 The "no observed adverse effect level" (NOAEL) in toxicity testing refers to:
The highest dose at which no adverse effects are observed
The lowest dose that causes a toxic effect
The average dose used in clinical trials
The maximum safe dosage for a healthy adult
Explanation - NOAEL is the highest exposure level at which there are no statistically or biologically significant increases in adverse effects compared with a control group.
Correct answer is: The highest dose at which no adverse effects are observed
Q.7 Which electrical property of a biomaterial is most critical for neural interface electrodes?
Dielectric constant
Electrical conductivity
Magnetic permeability
Thermal conductivity
Explanation - Neural interface electrodes must have sufficient conductivity to transmit electrical signals between the nervous system and external devices.
Correct answer is: Electrical conductivity
Q.8 What is the typical threshold for acceptable cytotoxicity in an in‑vitro test according to ISO 10993‑5?
Cell viability > 70%
Cell viability > 90%
Cell viability > 50%
Cell viability > 30%
Explanation - ISO 10993‑5 states that a material is considered non‑cytotoxic if the relative cell viability is greater than 70% compared to the control.
Correct answer is: Cell viability > 70%
Q.9 Which surface modification technique is commonly used to improve the biocompatibility of metallic implants?
Anodization
Laser ablation
Plasma spraying
All of the above
Explanation - Anodization, laser ablation, and plasma spraying can all modify surface chemistry and topography, enhancing biocompatibility and reducing corrosion.
Correct answer is: All of the above
Q.10 The term "bio‑fouling" in the context of implantable devices refers to:
Accumulation of bacterial biofilm on the device surface
Electrical short‑circuiting of the device
Mechanical wear of the device
Magnetic interference with the device
Explanation - Bio‑fouling is the undesirable accumulation of proteins, cells, or microorganisms on a material surface, potentially leading to infection and device failure.
Correct answer is: Accumulation of bacterial biofilm on the device surface
Q.11 Which of the following is NOT a common method to assess the inflammatory response to an implanted biomaterial?
Histological examination of tissue sections
Measurement of cytokine levels
Electrochemical impedance spectroscopy
White blood cell count in peripheral blood
Explanation - Electrochemical impedance spectroscopy measures electrical properties; it is not a direct method for evaluating inflammation, which is assessed by histology, cytokines, and blood counts.
Correct answer is: Electrochemical impedance spectroscopy
Q.12 A material that degrades into non‑toxic by‑products over time is classified as:
Biostable
Bioactive
Biodegradable
Brittle
Explanation - Biodegradable materials are designed to break down into harmless by‑products, reducing long‑term foreign body presence.
Correct answer is: Biodegradable
Q.13 Which of the following ions released from metal implants is most associated with allergic reactions?
Sodium (Na⁺)
Calcium (Ca²⁺)
Nickel (Ni²⁺)
Potassium (K⁺)
Explanation - Nickel ions are known to elicit hypersensitivity reactions in many individuals, making nickel‑containing alloys less suitable for implants in susceptible patients.
Correct answer is: Nickel (Ni²⁺)
Q.14 What is the primary advantage of using conductive polymers (e.g., PEDOT) in neural electrodes?
Higher mechanical strength
Improved electrical conductivity while maintaining flexibility
Reduced cost compared to metals
Intrinsic antibacterial properties
Explanation - Conductive polymers combine good conductivity with mechanical flexibility, reducing tissue damage and improving chronic electrode performance.
Correct answer is: Improved electrical conductivity while maintaining flexibility
Q.15 The "contact angle" measurement of a biomaterial surface is used to assess:
Electrical resistance
Surface wettability
Magnetic susceptibility
Thermal expansion coefficient
Explanation - Contact angle quantifies how a liquid droplet spreads on a surface; low angles indicate high wettability, which influences protein adsorption and cell attachment.
Correct answer is: Surface wettability
Q.16 Which of the following best describes "hemocompatibility"?
Compatibility with bone tissue
Compatibility with blood without causing clotting or hemolysis
Compatibility with neural tissue
Compatibility with skin cells
Explanation - Hemocompatibility ensures that a material in contact with blood does not trigger thrombosis, hemolysis, or adverse immune responses.
Correct answer is: Compatibility with blood without causing clotting or hemolysis
Q.17 In toxicity testing, the term "LD50" refers to:
The dose at which 50% of the test animals die
The concentration at which 50% of cells survive
The limit dose for daily human exposure
The lethal dose for 5% of the population
Explanation - LD50 (lethal dose, 50%) is a standard measure of acute toxicity, indicating the dose required to kill half of a test population.
Correct answer is: The dose at which 50% of the test animals die
Q.18 Which of the following is a major factor influencing the electrical stimulation threshold of a neural electrode?
Electrode surface roughness
Electrode material density
Electrode impedance
Electrode color
Explanation - Higher impedance at the electrode–tissue interface raises the voltage required to achieve the same current, thus increasing stimulation thresholds.
Correct answer is: Electrode impedance
Q.19 What is the purpose of performing a "sensitization" test on a biomaterial?
To assess the material's electrical conductivity
To evaluate the potential of the material to cause allergic reactions
To measure the mechanical strength of the material
To determine the material's thermal stability
Explanation - Sensitization tests, such as the Guinea pig maximization test, assess whether a material can elicit a delayed-type hypersensitivity response.
Correct answer is: To evaluate the potential of the material to cause allergic reactions
Q.20 Which of the following polymers is widely used for its excellent biocompatibility and electrical insulation in implantable devices?
Polylactic acid (PLA)
Polyethylene terephthalate (PET)
Polydimethylsiloxane (PDMS)
Polyvinyl chloride (PVC)
Explanation - PDMS is chemically inert, biocompatible, and provides good electrical insulation, making it popular for encapsulating implantable electronics.
Correct answer is: Polydimethylsiloxane (PDMS)
Q.21 Which technique is most appropriate for measuring the corrosion rate of a metallic implant in simulated body fluid?
Scanning electron microscopy (SEM)
Electrochemical potentiodynamic polarization
Fourier‑transform infrared spectroscopy (FTIR)
X‑ray diffraction (XRD)
Explanation - Potentiodynamic polarization provides quantitative data on corrosion current density, from which corrosion rates in simulated body fluid can be derived.
Correct answer is: Electrochemical potentiodynamic polarization
Q.22 The release of which type of molecule from a biomaterial can lead to oxidative stress in surrounding cells?
Antioxidants
Free radicals
Growth factors
Hormones
Explanation - Free radicals such as reactive oxygen species can damage cellular components, leading to oxidative stress and potentially cytotoxic effects.
Correct answer is: Free radicals
Q.23 When designing a bioelectronic interface, why is it important to match the elastic modulus of the device to that of the surrounding tissue?
To improve electrical conductivity
To reduce mechanical mismatch and chronic inflammation
To increase the device’s magnetic susceptibility
To enhance optical transparency
Explanation - Mechanical mismatch can cause micromotion, leading to tissue irritation, inflammation, and eventual device failure.
Correct answer is: To reduce mechanical mismatch and chronic inflammation
Q.24 Which assay would you use to evaluate the potential of a biomaterial to cause hemolysis?
LDH release assay
Hemoglobin release assay
MTT assay
Comet assay
Explanation - Hemoglobin release from red blood cells is measured to quantify hemolysis caused by a material.
Correct answer is: Hemoglobin release assay
Q.25 A material that does not interact with biological systems and elicits no response is termed:
Bioactive
Biostable
Bioinert
Biodegradable
Explanation - Bioinert materials are chemically stable and do not provoke a significant biological response, making them suitable for certain long‑term implants.
Correct answer is: Bioinert
Q.26 Which of the following is a major advantage of using titanium over stainless steel for neural electrode shafts?
Higher magnetic susceptibility
Lower electrical conductivity
Superior biocompatibility and corrosion resistance
Greater density
Explanation - Titanium forms a stable oxide layer that resists corrosion and is well tolerated by tissues, whereas stainless steel may release corrosion products.
Correct answer is: Superior biocompatibility and corrosion resistance
Q.27 The term "dose‑response curve" in toxicology represents:
The relationship between electrical voltage and current
The relationship between the amount of a toxin and the magnitude of the biological effect
The change in temperature with varying material thickness
The variation of impedance with frequency
Explanation - A dose‑response curve plots the effect (e.g., cell death) versus the dose of a toxic agent, helping to determine toxicity thresholds.
Correct answer is: The relationship between the amount of a toxin and the magnitude of the biological effect
Q.28 Which of the following is a common indicator of oxidative stress in cells exposed to a biomaterial?
Increased ATP production
Elevated glutathione (GSH) levels
Higher levels of malondialdehyde (MDA)
Reduced intracellular calcium
Explanation - MDA is a product of lipid peroxidation and is widely used as a biomarker for oxidative damage in cells.
Correct answer is: Higher levels of malondialdehyde (MDA)
Q.29 Which of the following statements about "bio‑resorbable" electrical conductors is true?
They permanently remain in the body after implantation.
They are made from non‑conductive polymers.
They provide temporary electrical functionality and degrade harmlessly over time.
They are always made of metallic alloys.
Explanation - Bio‑resorbable conductors, such as magnesium or certain polymers doped with conductive particles, are designed to function temporarily and then safely dissolve.
Correct answer is: They provide temporary electrical functionality and degrade harmlessly over time.
Q.30 When assessing a biomaterial’s compatibility with nerve tissue, which protein’s expression is commonly monitored as an indicator of neuronal health?
Collagen I
Neurofilament protein (NF‑H)
Albumin
Keratin
Explanation - Neurofilament proteins are structural components of axons; their expression reflects neuronal integrity and health.
Correct answer is: Neurofilament protein (NF‑H)
Q.31 What is the primary purpose of coating a metallic electrode with a thin layer of silicon carbide (SiC)?
To increase the electrode’s magnetic field
To enhance biocompatibility and reduce corrosion
To make the electrode transparent
To decrease its electrical resistance
Explanation - SiC is chemically inert, providing a protective barrier that reduces ion release and improves long‑term biocompatibility of metal electrodes.
Correct answer is: To enhance biocompatibility and reduce corrosion
Q.32 A "live/dead" fluorescent staining assay typically uses which pair of dyes?
DAPI and FITC
Propidium iodide (PI) and Calcein‑AM
Rhodamine and Alexa Fluor
Hoechst and TRITC
Explanation - Calcein‑AM stains live cells (green), while PI penetrates only compromised membranes, staining dead cells (red).
Correct answer is: Propidium iodide (PI) and Calcein‑AM
Q.33 Which of the following best describes the "foreign body response" to an implanted biomaterial?
Rapid electrical signaling
Formation of a fibrous capsule around the implant
Immediate tissue regeneration
Increase in blood flow to the area
Explanation - The foreign body response often culminates in the encapsulation of the implant by a dense collagenous fibrous capsule, isolating it from surrounding tissue.
Correct answer is: Formation of a fibrous capsule around the implant
Q.34 In the context of neural prostheses, which frequency range is most commonly used for stimulation to avoid muscle activation?
0.5–5 Hz
10–20 Hz
30–200 Hz
500–1000 Hz
Explanation - Stimulation within 30–200 Hz effectively activates neural tissue while minimizing unintended muscle activation.
Correct answer is: 30–200 Hz
Q.35 Which property of a biomaterial primarily determines its ability to support cell adhesion?
Electrical resistance
Surface roughness and chemistry
Magnetic permeability
Thermal conductivity
Explanation - Cell adhesion is strongly influenced by surface topography and chemical functional groups that affect protein adsorption and integrin binding.
Correct answer is: Surface roughness and chemistry
Q.36 What does the term "electrochemical stability window" refer to in the design of bioelectronic devices?
The range of temperatures over which the device operates
The voltage range in which the electrode material does not undergo harmful electrochemical reactions
The frequency range of electrical signals that can be transmitted
The mechanical stress range tolerated by the device
Explanation - Operating within the electrochemical stability window prevents corrosion, gas evolution, or toxic by‑product formation at the electrode–tissue interface.
Correct answer is: The voltage range in which the electrode material does not undergo harmful electrochemical reactions
Q.37 Which of the following is a standard in‑vitro test to assess the potential for a biomaterial to cause genotoxic effects?
Ames test
MTT assay
ELISA for cytokines
Four‑point bending test
Explanation - The Ames test uses bacteria to detect mutagenic (genotoxic) properties of chemicals released from biomaterials.
Correct answer is: Ames test
Q.38 A high "Z-potential" on the surface of a biomaterial generally leads to:
Improved electrical conductivity
Reduced protein adsorption and better colloidal stability
Increased magnetic susceptibility
Higher thermal conductivity
Explanation - A high absolute Z-potential creates strong electrostatic repulsion, preventing aggregation and limiting protein adsorption, which can affect biocompatibility.
Correct answer is: Reduced protein adsorption and better colloidal stability
Q.39 Which material property is most critical for ensuring that an implanted electrode does not cause chronic inflammation due to micromotion?
High Young’s modulus
Low Young’s modulus (flexibility)
High density
High thermal conductivity
Explanation - A flexible electrode that matches tissue compliance reduces micromotion, thereby decreasing chronic inflammatory responses.
Correct answer is: Low Young’s modulus (flexibility)
Q.40 The "burst release" phenomenon observed in drug‑eluting implants is mainly caused by:
Rapid initial diffusion of surface‑bound drug molecules
Electrical breakdown of the polymer matrix
Thermal degradation of the device
Mechanical fatigue of the implant
Explanation - Burst release occurs when drug molecules near the surface diffuse quickly into surrounding tissue before a sustained release phase is established.
Correct answer is: Rapid initial diffusion of surface‑bound drug molecules
Q.41 In the context of implantable devices, what does the term "passivation" refer to?
Increasing the electrical conductivity of a material
Creating a thin, inert oxide layer to protect the underlying metal from corrosion
Heating the device to sterilize it
Applying a magnetic coating to improve MRI compatibility
Explanation - Passivation forms a stable, non‑reactive surface film (often oxide) that reduces corrosion and ion release.
Correct answer is: Creating a thin, inert oxide layer to protect the underlying metal from corrosion
Q.42 Which of the following is a key advantage of using graphene as a coating for neural electrodes?
It is highly magnetic
It provides excellent electrical conductivity and mechanical flexibility
It is opaque to visible light
It dissolves quickly in body fluids
Explanation - Graphene offers high conductivity, flexibility, and a large surface area, improving signal quality while conforming to tissue movements.
Correct answer is: It provides excellent electrical conductivity and mechanical flexibility
Q.43 The term "biocompatibility" encompasses which of the following aspects?
Electrical performance only
Mechanical strength only
Interaction with the host tissue without causing adverse effects
Color and aesthetic appearance
Explanation - Biocompatibility is a holistic assessment of how a material interacts with biological systems, covering cytotoxicity, immunogenicity, hemocompatibility, and more.
Correct answer is: Interaction with the host tissue without causing adverse effects
Q.44 Which of the following metals is most commonly used for its radiopacity in implantable devices?
Titanium
Gold
Aluminum
Magnesium
Explanation - Gold has high radiodensity, making devices containing it easily visible under X‑ray imaging.
Correct answer is: Gold
Q.45 A biomaterial that induces a chronic inflammatory response leading to tissue necrosis is considered:
Bioinert
Biocompatible
Toxic
Biodegradable
Explanation - Materials that cause sustained inflammation and cell death are classified as toxic and unsuitable for implantation.
Correct answer is: Toxic
Q.46 Which method can be used to quantitatively assess the amount of metal ion release from an implant after immersion in simulated body fluid?
Atomic absorption spectroscopy (AAS)
Scanning electron microscopy (SEM)
Fourier‑transform infrared spectroscopy (FTIR)
Differential scanning calorimetry (DSC)
Explanation - AAS detects and quantifies specific metal ions in solution, providing precise measurements of corrosion‑derived release.
Correct answer is: Atomic absorption spectroscopy (AAS)
Q.47 Which of the following factors most directly influences the rate of degradation of biodegradable polymeric electrodes?
Electrical conductivity
Polymer crystallinity
Magnetic permeability
Surface color
Explanation - Higher crystallinity reduces water penetration, slowing hydrolytic degradation, while amorphous regions degrade faster.
Correct answer is: Polymer crystallinity
Q.48 In a cell viability assay, an absorbance reading that is 80% of the control indicates:
Severe cytotoxicity
Mild cytotoxicity, still within acceptable limits
No effect on cells
Complete cell death
Explanation - According to ISO 10993‑5, viability >70% is generally considered non‑cytotoxic; 80% suggests mild effect but acceptable.
Correct answer is: Mild cytotoxicity, still within acceptable limits
Q.49 Which of the following best explains why flexible polymer substrates can reduce scar tissue formation around implanted electrodes?
Polymers absorb more electrical current
Flexibility allows the device to move with the tissue, reducing mechanical irritation
Polymers emit anti‑inflammatory chemicals
Polymers have higher thermal conductivity
Explanation - Matching the mechanical compliance of tissue minimizes micromotion‑induced inflammation and subsequent scar formation.
Correct answer is: Flexibility allows the device to move with the tissue, reducing mechanical irritation
Q.50 What is the primary purpose of a "sterilization validation" test for an implantable biomaterial?
To confirm that the material can conduct electricity after sterilization
To verify that the sterilization process effectively eliminates microbial contamination without compromising material properties
To measure the material’s magnetic susceptibility
To determine the optimal implantation temperature
Explanation - Sterilization validation ensures both microbial safety and that the material’s biocompatibility and functionality remain intact post‑sterilization.
Correct answer is: To verify that the sterilization process effectively eliminates microbial contamination without compromising material properties
Q.51 Which of the following statements about "electrochemical impedance spectroscopy" (EIS) in the context of neural implants is true?
EIS can directly measure the amount of metal ion release.
EIS provides information on the electrode–tissue interface impedance, which correlates with tissue health.
EIS is used to assess the mechanical strength of the implant.
EIS determines the optical transparency of the device.
Explanation - Changes in impedance over time can indicate tissue encapsulation, inflammation, or degradation of the electrode surface.
Correct answer is: EIS provides information on the electrode–tissue interface impedance, which correlates with tissue health.
Q.52 Which of the following is an example of a "smart" biomaterial used in bioelectronic applications?
A passive silicone elastomer
A polymer that releases drugs in response to an electrical stimulus
A stainless‑steel screw
A glass fiber composite
Explanation - Smart biomaterials can respond to external cues (e.g., electrical signals) to modulate drug release, providing on‑demand therapy.
Correct answer is: A polymer that releases drugs in response to an electrical stimulus
Q.53 Which of the following parameters is most directly linked to the risk of "electrochemical corrosion" of an implant when a voltage is applied?
Electrode surface roughness
Applied potential exceeding the material’s corrosion potential
Ambient temperature
Device weight
Explanation - If the applied voltage surpasses the corrosion potential, oxidation reactions accelerate, leading to material degradation.
Correct answer is: Applied potential exceeding the material’s corrosion potential
Q.54 In toxicity testing, a "sub‑lethal" dose is defined as:
A dose that kills 100% of the test organisms
A dose that does not cause death but may cause observable adverse effects
A dose that has no measurable effect whatsoever
The maximum dose that can be administered to a human
Explanation - Sub‑lethal doses are used to study non‑fatal toxic effects such as organ dysfunction, behavioral changes, or cellular stress.
Correct answer is: A dose that does not cause death but may cause observable adverse effects
Q.55 Which of the following techniques can be used to assess the mechanical durability of a flexible neural electrode under cyclic bending?
Four‑point bend test with cyclic loading
Differential scanning calorimetry (DSC)
Electrochemical impedance spectroscopy (EIS)
UV‑Vis spectroscopy
Explanation - Cyclic bending tests simulate repeated flexing in vivo, revealing fatigue life and mechanical failure points.
Correct answer is: Four‑point bend test with cyclic loading
Q.56 A biomaterial that elicits a moderate inflammatory response initially but resolves without chronic effects is considered:
Bioinert
Biodegradable
Biocompatible
Toxic
Explanation - Transient inflammation that resolves is normal; such a material is deemed biocompatible if it does not cause lasting damage.
Correct answer is: Biocompatible
Q.57 Which of the following is NOT a typical endpoint measured in chronic in‑vivo biocompatibility studies of neural implants?
Glial scar thickness
Electrode impedance over time
Blood glucose level
Neuronal density near the electrode
Explanation - Glial scar thickness, impedance, and neuronal density are directly related to implant performance; blood glucose is unrelated to local neural biocompatibility.
Correct answer is: Blood glucose level
Q.58 Which property of a polymeric coating most strongly influences its ability to prevent protein adsorption?
High surface energy
Hydrophilicity and presence of polyethylene glycol (PEG) chains
High electrical conductivity
Magnetic permeability
Explanation - PEGylated, hydrophilic surfaces resist protein adsorption due to steric repulsion and water structuring.
Correct answer is: Hydrophilicity and presence of polyethylene glycol (PEG) chains
Q.59 The "Mott‑Schottky" analysis of an electrode surface is used to determine:
Mechanical hardness
Charge carrier density and flat‑band potential
Thermal expansion coefficient
Magnetic susceptibility
Explanation - Mott‑Schottky plots provide semiconductor properties of electrode materials, useful for understanding electrochemical behavior.
Correct answer is: Charge carrier density and flat‑band potential
Q.60 Which of the following is a common cause of "delamination" in multilayered bioelectronic devices?
Excessive electrical current
Insufficient adhesion between layers due to poor surface treatment
High magnetic fields
Low temperature operation
Explanation - Improper surface preparation leads to weak interlayer bonding, causing delamination under mechanical or thermal stress.
Correct answer is: Insufficient adhesion between layers due to poor surface treatment
Q.61 A material that exhibits a rapid initial release of a drug followed by a sustained release is said to have:
Zero‑order kinetics
Biphasic release profile
First‑order kinetics
Constant release rate
Explanation - Biphasic release combines an early burst (fast) phase and a later sustained (slow) phase.
Correct answer is: Biphasic release profile
Q.62 Which of the following is the most appropriate method to evaluate the long‑term stability of an electrode’s electrical performance in vivo?
Weekly impedance spectroscopy measurements
One‑time visual inspection after explantation
Measuring the device’s weight before and after implantation
Testing the device’s magnetic field strength
Explanation - Regular EIS tracking captures changes in interface properties, indicating degradation or tissue encapsulation over time.
Correct answer is: Weekly impedance spectroscopy measurements
Q.63 Which of the following cellular markers is commonly used to identify activated macrophages in a foreign body response?
CD68
GFAP
Myosin
Collagen I
Explanation - CD68 is a lysosomal marker expressed by activated macrophages during inflammation and foreign body reaction.
Correct answer is: CD68
Q.64 A biomaterial that releases nitric oxide (NO) at low levels is intended to:
Increase electrical resistance
Promote vasodilation and inhibit platelet aggregation
Cause rapid tissue necrosis
Increase magnetic susceptibility
Explanation - NO has anti‑thrombotic and vasodilatory properties, improving hemocompatibility of blood‑contacting devices.
Correct answer is: Promote vasodilation and inhibit platelet aggregation
Q.65 Which of the following is an example of a "non‑invasive" method to monitor the function of an implanted neural electrode?
Electroencephalography (EEG) recorded from scalp electrodes
Direct histological analysis of the implanted tissue
Explantation and bench testing
In‑vivo optical microscopy requiring craniotomy
Explanation - EEG provides indirect information about neural activity without accessing the implant site.
Correct answer is: Electroencephalography (EEG) recorded from scalp electrodes
Q.66 What does the term "biofunctionalization" refer to in the context of biomaterials?
Increasing the material’s electrical conductivity
Adding biological ligands or molecules to a material surface to confer specific cellular interactions
Heating the material to high temperatures
Painting the material with bright colors
Explanation - Biofunctionalization tailors surface chemistry to promote desired cell adhesion, signaling, or tissue integration.
Correct answer is: Adding biological ligands or molecules to a material surface to confer specific cellular interactions
Q.67 Which of the following best describes the purpose of a "control group" in an in‑vitro cytotoxicity assay?
To provide a baseline measurement of cell viability without exposure to the test material
To increase the overall cost of the experiment
To test a different material simultaneously
To calibrate the microscope
Explanation - Controls establish the normal response of cells, allowing comparison against the test samples.
Correct answer is: To provide a baseline measurement of cell viability without exposure to the test material
Q.68 Which of the following statements about “electroactive” biomaterials is correct?
They are always metallic.
They can transduce electrical signals into biochemical cues for cells.
They are never used in neural applications.
They are completely inert to the body.
Explanation - Electroactive biomaterials interact with cells via electrical stimulation, influencing processes such as proliferation and differentiation.
Correct answer is: They can transduce electrical signals into biochemical cues for cells.
Q.69 In the context of implantable devices, the "water uptake" property of a polymer mainly affects:
Electrical conductivity only
Mechanical stiffness and degradation rate
Magnetic properties
Optical transparency
Explanation - Higher water absorption softens polymers and accelerates hydrolytic degradation, influencing device performance.
Correct answer is: Mechanical stiffness and degradation rate
Q.70 Which of the following is a primary reason for using "thin‑film" deposition techniques (e.g., sputtering) for neural electrode fabrication?
To increase the bulk weight of the electrode
To achieve precise control over thickness and surface roughness, which impacts impedance and biocompatibility
To make the electrode magnetic
To create a porous structure for drug loading
Explanation - Thin‑film methods allow fine tuning of electrode dimensions and surface features, essential for reliable electrical performance and tissue interaction.
Correct answer is: To achieve precise control over thickness and surface roughness, which impacts impedance and biocompatibility
Q.71 A device that is labeled as "MRI‑compatible" must satisfy which of the following criteria?
Zero electrical conductivity
Non‑ferromagnetic composition and minimal heating under RF fields
High magnetic susceptibility
Ability to generate strong magnetic fields
Explanation - MRI compatibility requires that the device does not move or heat significantly in the magnetic field, avoiding patient risk.
Correct answer is: Non‑ferromagnetic composition and minimal heating under RF fields
Q.72 Which of the following best describes the role of "glial scar" formation around implanted neural electrodes?
It enhances electrical conductivity of the electrode.
It isolates the electrode, increasing impedance and reducing signal quality.
It promotes rapid neuronal regeneration.
It has no effect on electrode performance.
Explanation - Glial scarring creates a barrier that raises impedance and attenuates recorded/stimulated signals, degrading device performance over time.
Correct answer is: It isolates the electrode, increasing impedance and reducing signal quality.
Q.73 Which of the following is a common approach to mitigate the inflammatory response to an implanted electrode?
Increasing the electrode’s stiffness
Coating the electrode with anti‑inflammatory drug‑eluting polymers
Using a larger electrode size
Applying a high-voltage pulse immediately after implantation
Explanation - Localized drug release can suppress inflammation and improve integration of the electrode with neural tissue.
Correct answer is: Coating the electrode with anti‑inflammatory drug‑eluting polymers
Q.74 The "Raman spectroscopy" technique is most useful for:
Measuring electrical impedance
Identifying chemical composition and molecular structure of biomaterial surfaces
Assessing mechanical strength
Quantifying ion release
Explanation - Raman spectroscopy provides vibrational spectra that reveal molecular bonds and material composition, helpful for surface analysis.
Correct answer is: Identifying chemical composition and molecular structure of biomaterial surfaces
Q.75 Which of the following statements about “ionic conductivity” in hydrogels used for bioelectronic interfaces is correct?
Ionic conductivity is unrelated to water content.
Higher water content generally leads to higher ionic conductivity.
Ionic conductivity decreases with increasing temperature.
Ionic conductivity makes the hydrogel magnetic.
Explanation - Water provides pathways for ion movement; more water yields higher ionic conductivity in hydrogels.
Correct answer is: Higher water content generally leads to higher ionic conductivity.
Q.76 Which of the following is a major limitation of using silver (Ag) as a material for chronic neural electrodes?
Low electrical conductivity
Rapid dissolution and release of Ag⁺ ions causing cytotoxicity
Excessive mechanical rigidity
Incompatibility with MRI
Explanation - Silver can corrode in physiological environments, releasing toxic ions that jeopardize long‑term biocompatibility.
Correct answer is: Rapid dissolution and release of Ag⁺ ions causing cytotoxicity
Q.77 The “Miller index” is used in material science to describe:
Crystallographic planes and orientations
Electrical resistance
Magnetic permeability
Thermal conductivity
Explanation - Miller indices denote the orientation of lattice planes, influencing surface reactivity and corrosion behavior.
Correct answer is: Crystallographic planes and orientations
Q.78 Which of the following is an advantage of using a "wireless power transfer" system for implanted bioelectronic devices?
Eliminates the need for battery replacement surgeries
Increases the device’s size dramatically
Reduces the device’s biocompatibility
Prevents any electromagnetic interference
Explanation - Wireless power allows continuous operation without invasive battery changes, improving patient comfort and reducing surgical risk.
Correct answer is: Eliminates the need for battery replacement surgeries
Q.79 Which of the following best explains why “hydrogel” based electrodes can improve signal-to-noise ratio in neural recordings?
Hydrogels are highly conductive like metals.
Their softness conforms to tissue, reducing the electrode‑tissue gap and improving coupling.
Hydrogels block all electrical activity.
Hydrogels increase the temperature of the tissue.
Explanation - Close contact reduces impedance and noise, enhancing the fidelity of recorded neural signals.
Correct answer is: Their softness conforms to tissue, reducing the electrode‑tissue gap and improving coupling.
Q.80 Which of the following assays is specifically designed to evaluate the potential for a biomaterial to cause allergic skin reactions?
Patch test
MTT assay
Hemolysis assay
Comet assay
Explanation - The patch test assesses contact sensitization by applying the material to the skin and observing allergic reactions.
Correct answer is: Patch test
Q.81 In the context of bioelectronic implants, “electrochemical corrosion” is most directly mitigated by:
Increasing the applied voltage
Applying a stable, inert coating such as TiO₂
Reducing the device’s size
Operating the device at high frequencies
Explanation - Inert coatings act as barriers to ion exchange, limiting corrosion reactions at the electrode surface.
Correct answer is: Applying a stable, inert coating such as TiO₂
Q.82 Which of the following is a typical sign of acute toxicity observed in an animal study after implantation of a new biomaterial?
Gradual weight gain
Localized swelling, erythema, and necrosis
Improved motor function
Enhanced learning ability
Explanation - Acute toxicity often manifests as inflammation, tissue damage, and necrotic lesions near the implant site.
Correct answer is: Localized swelling, erythema, and necrosis
Q.83 Which of the following best describes the purpose of a "burst mode" in electrical stimulation protocols for neural prostheses?
To deliver a continuous high‑frequency signal
To provide short, high‑amplitude pulses that can reduce charge accumulation and tissue damage
To increase the temperature of the implant
To permanently deactivate the device
Explanation - Burst mode delivers brief high‑intensity pulses, minimizing overall charge while achieving effective stimulation.
Correct answer is: To provide short, high‑amplitude pulses that can reduce charge accumulation and tissue damage
Q.84 The primary reason for using “polyimide” as a substrate in flexible neural electrodes is:
Its high magnetic permeability
Excellent thermal conductivity
High flexibility, chemical stability, and suitable dielectric properties
Its ability to dissolve in body fluids
Explanation - Polyimide combines mechanical flexibility with chemical resistance, making it ideal for conformal neural interfaces.
Correct answer is: High flexibility, chemical stability, and suitable dielectric properties
Q.85 Which of the following is the most direct indicator of oxidative stress in cells exposed to a leachate from a biomaterial?
Increased ATP production
Elevated levels of reactive oxygen species (ROS)
Decreased cell membrane potential
Increased cell proliferation
Explanation - ROS accumulation is a hallmark of oxidative stress, often measured with fluorescent probes like DCFDA.
Correct answer is: Elevated levels of reactive oxygen species (ROS)
Q.86 When a biomaterial is described as "bio‑transparent," this means:
It allows visible light to pass through, facilitating optical monitoring of underlying tissue.
It has zero electrical conductivity.
It completely blocks all electromagnetic radiation.
It is invisible to MRI.
Explanation - Bio‑transparent materials enable optical imaging (e.g., fluorescence microscopy) of tissue while the device remains in place.
Correct answer is: It allows visible light to pass through, facilitating optical monitoring of underlying tissue.
Q.87 Which of the following phenomena can cause a sudden increase in electrode impedance during chronic implantation?
Formation of a protein‑rich fouling layer and glial scar
Improved tissue integration
Decrease in temperature
Reduction of surrounding fluid volume
Explanation - Bio‑fouling and scar tissue create insulating barriers that raise the interface impedance.
Correct answer is: Formation of a protein‑rich fouling layer and glial scar
Q.88 Which of the following is NOT a typical characteristic of a “self‑healing” polymer used in bioelectronics?
Ability to restore mechanical integrity after damage
Permanent increase in electrical resistance after healing
Reversible covalent or supramolecular bonding mechanisms
Potential to extend device lifetime
Explanation - Self‑healing polymers aim to recover both mechanical and electrical properties, not degrade them.
Correct answer is: Permanent increase in electrical resistance after healing
Q.89 In a chronic animal study, a neural electrode showed a 30% increase in impedance after 6 months but maintained stable signal amplitudes. This suggests:
Complete device failure
Effective encapsulation without functional loss
Severe tissue necrosis
Device migration
Explanation - A moderate impedance rise can be compensated by device design; stable signals indicate functional performance despite encapsulation.
Correct answer is: Effective encapsulation without functional loss
Q.90 Which of the following factors most directly influences the rate of ion diffusion through a polymeric coating on an electrode?
Polymer crystallinity and cross‑link density
Color of the polymer
Magnetic susceptibility
Electrical resistance of the underlying metal
Explanation - Higher crystallinity and cross‑linking reduce free volume, slowing ion diffusion and enhancing barrier properties.
Correct answer is: Polymer crystallinity and cross‑link density
Q.91 Which of the following is a common method to evaluate the long‑term mechanical stability of a stretchable electrode under physiological conditions?
Cyclic tensile testing in a saline bath
Measuring optical absorption spectra
Performing X‑ray diffraction
Using a thermal camera
Explanation - Cyclic loading in a physiological medium simulates mechanical fatigue and corrosion simultaneously.
Correct answer is: Cyclic tensile testing in a saline bath
Q.92 A biomaterial that induces the expression of interleukin‑10 (IL‑10) in surrounding tissue is likely to be:
Pro‑inflammatory
Anti‑inflammatory
Neurotoxic
Hemolytic
Explanation - IL‑10 is an anti‑inflammatory cytokine; its up‑regulation suggests a material that mitigates inflammation.
Correct answer is: Anti‑inflammatory
Q.93 Which of the following best describes the purpose of "accelerated aging" tests for implantable bioelectronics?
To instantly increase the device's performance
To simulate long‑term degradation in a short time by exposing the device to elevated temperature/humidity
To reduce the device's size
To change the device's color
Explanation - Accelerated aging predicts lifetime performance by speeding up chemical and physical degradation mechanisms.
Correct answer is: To simulate long‑term degradation in a short time by exposing the device to elevated temperature/humidity
Q.94 Which of the following is a major advantage of using "conductive hydrogel" interfaces for neural stimulation?
They are completely non‑conductive to ions.
They combine high ionic conductivity with tissue‑like softness, improving charge transfer and reducing mechanical mismatch.
They permanently bond to the tissue, preventing any movement.
They are magnetic and can be moved with external fields.
Explanation - Conductive hydrogels provide a soft, ionically conductive interface, enhancing stimulation efficiency while matching tissue mechanics.
Correct answer is: They combine high ionic conductivity with tissue‑like softness, improving charge transfer and reducing mechanical mismatch.
Q.95 In the context of bioelectronic implants, the "charge injection limit" refers to:
The maximum amount of charge that can be safely delivered per phase without causing irreversible electrochemical reactions
The maximum mechanical strain the electrode can sustain
The highest temperature the device can reach
The largest magnetic field the device can generate
Explanation - Exceeding the charge injection limit can lead to irreversible faradaic reactions, electrode degradation, and tissue damage.
Correct answer is: The maximum amount of charge that can be safely delivered per phase without causing irreversible electrochemical reactions
Q.96 Which of the following is a typical sign that a polymeric coating on an electrode is beginning to fail in vivo?
Decrease in device weight
Sudden increase in ion release and rise in electrode impedance
Improved signal amplitude
Change in device color to blue
Explanation - Coating degradation exposes the underlying metal, leading to corrosion (ion release) and higher impedance at the interface.
Correct answer is: Sudden increase in ion release and rise in electrode impedance
Q.97 Which of the following cellular assays is most suitable for detecting DNA damage caused by a biomaterial’s leachates?
Comet assay
MTT assay
Live/Dead staining
LDH release assay
Explanation - The comet assay (single‑cell gel electrophoresis) detects DNA strand breaks and is sensitive to genotoxic effects.
Correct answer is: Comet assay
Q.98 A neural electrode coated with a thin layer of "PEDOT:PSS" is expected to show:
Higher impedance and lower charge storage capacity
Reduced impedance and higher charge storage capacity
Increased magnetic susceptibility
Decreased flexibility
Explanation - PEDOT:PSS is a conductive polymer that lowers impedance and enhances charge transfer capabilities of electrodes.
Correct answer is: Reduced impedance and higher charge storage capacity
Q.99 Which of the following best describes the function of a "reference electrode" in an implantable stimulation system?
It provides a stable baseline potential for accurate control of stimulation currents
It generates the stimulation pulses
It measures temperature
It serves as a mechanical support
Explanation - A reference electrode maintains a known, constant potential, allowing precise current regulation during stimulation.
Correct answer is: It provides a stable baseline potential for accurate control of stimulation currents
Q.100 Which of the following is a primary factor that can cause “electrode drift” in chronic neural recordings?
Stable tissue‑electrode interface
Micromotion and gradual tissue remodeling around the electrode
Constant temperature
Absence of electrical stimulation
Explanation - Micromotion and remodeling can shift electrode position relative to neurons, causing signal drift over time.
Correct answer is: Micromotion and gradual tissue remodeling around the electrode
Q.101 Which of the following techniques is most appropriate for visualizing the three‑dimensional architecture of a fibrous capsule surrounding an implant?
Scanning electron microscopy (SEM)
Confocal laser scanning microscopy (CLSM)
X‑ray diffraction (XRD)
Fourier‑transform infrared spectroscopy (FTIR)
Explanation - CLSM can image thick, fluorescently labeled tissue sections in 3D, revealing capsule thickness and cell distribution.
Correct answer is: Confocal laser scanning microscopy (CLSM)
Q.102 Which of the following statements about the "blood‑brain barrier" (BBB) is true in the context of implanted neuro‑electronic devices?
The BBB prevents any electrical signals from reaching the brain.
Implantation can locally disrupt the BBB, potentially increasing immune cell infiltration.
The BBB is irrelevant for chronic implants.
The BBB enhances the conductivity of neural tissue.
Explanation - Surgical implantation may breach the BBB, leading to localized inflammation and altered immune responses.
Correct answer is: Implantation can locally disrupt the BBB, potentially increasing immune cell infiltration.
Q.103 Which of the following is the most common method to sterilize polymer‑based neural electrodes without damaging the polymer?
Autoclaving at 121 °C
Gamma irradiation
Dry heat at 250 °C
Plasma (hydrogen peroxide) sterilization
Explanation - Low‑temperature plasma sterilization effectively kills microbes while preserving polymer integrity.
Correct answer is: Plasma (hydrogen peroxide) sterilization
Q.104 A device that is designed to be fully resorbed by the body within 12 months would be classified as:
Permanent
Biodegradable
Bioinert
Non‑resorbable
Explanation - Biodegradable devices are intended to break down into harmless products within a predefined time frame.
Correct answer is: Biodegradable
Q.105 Which of the following is a primary advantage of using "nano‑structured" surfaces on neural electrodes?
They increase the electrode’s weight.
They enhance surface area, reducing impedance and promoting better cell adhesion.
They make the electrode magnetic.
They reduce the electrode’s electrical conductivity.
Explanation - Nano‑structuring increases effective surface area, lowering impedance and facilitating favorable cellular interactions.
Correct answer is: They enhance surface area, reducing impedance and promoting better cell adhesion.
Q.106 The "Hertzian contact model" is used to describe:
Electrical resistance of a material
Mechanical contact stresses between two elastic bodies
Thermal conductivity of polymers
Magnetic field distribution
Explanation - The Hertzian model predicts stress distribution at the contact point, relevant for evaluating mechanical interactions of implants.
Correct answer is: Mechanical contact stresses between two elastic bodies
Q.107 Which of the following is the most direct indicator of a material’s hemocompatibility when in contact with blood?
Measurement of platelet adhesion and activation on the material surface
Determination of the material’s Young’s modulus
Assessment of its optical transparency
Measurement of its magnetic susceptibility
Explanation - Platelet adhesion/activation assays directly assess thrombogenic potential, a key aspect of hemocompatibility.
Correct answer is: Measurement of platelet adhesion and activation on the material surface
Q.108 In the design of a bioelectronic device, “passive” components refer to:
Elements that do not require external power (e.g., resistors, capacitors)
Active amplifiers
Battery packs
Wireless transmitters
Explanation - Passive components function without an external power source, influencing signal conditioning and filtering.
Correct answer is: Elements that do not require external power (e.g., resistors, capacitors)
Q.109 Which of the following best explains why “low‑frequency” electrical stimulation (≤ 10 Hz) is often used for promoting nerve regeneration?
Low‑frequency signals are less likely to cause muscle fatigue and can encourage axonal outgrowth.
Low‑frequency signals generate higher temperatures.
Low‑frequency signals increase blood clotting.
Low‑frequency signals are more painful for patients.
Explanation - Low‑frequency stimulation mimics natural nerve firing patterns, supporting regeneration without inducing fatigue.
Correct answer is: Low‑frequency signals are less likely to cause muscle fatigue and can encourage axonal outgrowth.
Q.110 Which of the following statements about “bio‑resorbable" metallic alloys such as Mg‑Zn‑Ca is true?
They never corrode in the body.
They gradually dissolve, releasing benign ions that can support bone healing.
They are magnetically active and interfere with MRI.
They are completely inert and remain forever.
Explanation - Mg‑based alloys corrode safely, releasing magnesium and other ions that can promote bone regeneration.
Correct answer is: They gradually dissolve, releasing benign ions that can support bone healing.
Q.111 In a chronic neural implant study, an observed increase in the expression of the protein "GFAP" around the electrode indicates:
Neuronal proliferation
Activation of astrocytes and formation of glial scar
Decreased inflammation
Improved electrical conductivity
Explanation - Glial fibrillary acidic protein (GFAP) is a marker of astrocyte activation, a hallmark of glial scarring.
Correct answer is: Activation of astrocytes and formation of glial scar
Q.112 Which of the following is a typical advantage of using "thin‑film" microfabrication for creating high‑density electrode arrays?
Enables precise control over electrode size and spacing, increasing channel count while maintaining small footprint
Increases the weight of the device significantly
Makes the device more rigid
Reduces the number of possible recording sites
Explanation - Thin‑film processes allow sub‑micron patterning, facilitating dense electrode arrays for high‑resolution recordings.
Correct answer is: Enables precise control over electrode size and spacing, increasing channel count while maintaining small footprint
Q.113 Which of the following is an appropriate method for assessing the long‑term stability of a conductive polymer coating under physiological conditions?
Cyclic voltammetry in phosphate‑buffered saline over weeks
Measuring the device’s color change under UV light
Testing its magnetic susceptibility in air
Weighing the device before and after implantation
Explanation - Cyclic voltammetry tracks changes in electrochemical behavior, indicating degradation or loss of conductivity over time.
Correct answer is: Cyclic voltammetry in phosphate‑buffered saline over weeks
Q.114 A biomaterial that shows a high degree of "hydrophobicity" is likely to:
Promote rapid protein adsorption and cell adhesion
Resist protein adsorption, potentially reducing cell attachment
Increase water uptake
Become magnetic
Explanation - Hydrophobic surfaces tend to repel water and proteins, which can limit cell adhesion unless modified.
Correct answer is: Resist protein adsorption, potentially reducing cell attachment
Q.115 Which of the following best defines the term "bioelectronic interface"?
A device that converts chemical signals into optical signals
A system that enables bidirectional communication between electronic circuits and biological tissue
A purely mechanical connector
A magnetic resonance imaging component
Explanation - Bioelectronic interfaces translate electrical signals to/from biological systems, enabling sensing, stimulation, or modulation.
Correct answer is: A system that enables bidirectional communication between electronic circuits and biological tissue
Q.116 Which of the following is a common cause of "electrolysis" at the electrode–tissue interface during high‑frequency stimulation?
Low current density
Excessive voltage exceeding the water electrolysis threshold
Use of inert materials like gold
Operating at body temperature
Explanation - High voltages can split water into H₂ and O₂ gases, leading to bubble formation and possible tissue damage.
Correct answer is: Excessive voltage exceeding the water electrolysis threshold
Q.117 Which of the following assays can be used to evaluate the potential of a biomaterial to cause oxidative DNA damage?
8‑oxo‑dG ELISA
MTT assay
Live/Dead staining
Hemolysis test
Explanation - 8‑oxo‑deoxyguanosine (8‑oxo‑dG) is a marker of oxidative DNA damage; ELISA quantifies its levels.
Correct answer is: 8‑oxo‑dG ELISA
Q.118 In the context of implantable neural devices, a "cathodic-first" stimulation waveform is often preferred because:
It reduces the risk of irreversible electrochemical reactions at the electrode surface
It increases the magnetic field generated
It makes the device heavier
It eliminates the need for a reference electrode
Explanation - Cathodic-first pulses tend to be more charge‑balanced and less likely to cause anodic oxidation and tissue damage.
Correct answer is: It reduces the risk of irreversible electrochemical reactions at the electrode surface
Q.119 Which of the following is a key benefit of using “micro‑electromechanical systems” (MEMS) technology for fabricating neural probes?
Ability to create large, rigid structures
High precision, miniaturization, and integration of sensing/stimulation elements
Increased magnetic susceptibility
Reduced electrical conductivity
Explanation - MEMS enables batch fabrication of tiny, complex devices with integrated electronics suitable for neural interfacing.
Correct answer is: High precision, miniaturization, and integration of sensing/stimulation elements
Q.120 The term "chronaxie" in neurophysiology refers to:
The minimum current required to elicit a response
The pulse duration needed for double the rheobase current to evoke a response
The impedance of the electrode
The voltage required for electrode corrosion
Explanation - Chronaxie is a time constant that, together with rheobase, characterizes excitability of nerve tissue.
Correct answer is: The pulse duration needed for double the rheobase current to evoke a response
Q.121 Which of the following is a primary reason for using "hydrogel" coatings on microelectrodes intended for chronic brain implants?
Hydrogels increase the electrode's weight significantly
Hydrogels provide a soft, water‑rich environment that matches brain tissue mechanics, reducing chronic inflammation
Hydrogels make the electrode magnetic
Hydrogels permanently seal the electrode, preventing any electrical activity
Explanation - Mechanical compliance and high water content of hydrogels help minimize tissue irritation and improve long‑term stability.
Correct answer is: Hydrogels provide a soft, water‑rich environment that matches brain tissue mechanics, reducing chronic inflammation