Question 1

What is a biosensor and how does it work?

Accepted Answer

A biosensor is a device that uses a biological receptor molecule, such as an enzyme, antibody, or nucleic acid, to detect a specific compound in complex biological fluids. The bioreceptor captures the target molecule, causing a measurable event like a pH change or redox reaction. A transducer then converts this binding information into a quantifiable signal, allowing users to determine concentration or confirm molecular presence.

Question 2

How do optical biosensors detect target molecules?

Accepted Answer

Optical biosensors use light to detect binding between probe and target molecules. In fluorescence-based sensors, a polymer-coated surface is functionalized with probe molecules like single-stranded DNA. When complementary target DNA binds, fluorescence intensity changes, enabling users to determine the quantity and location of binding based on optical biosensing surface plasmon resonance principles and fluorescence measurements.

Question 3

What role do electrodes play in electrochemical biosensors?

Accepted Answer

Electrochemical biosensors use electrodes to sense redox reactions between probe and target molecules. An enzyme is typically bound to the electrode surface. When the target molecule binds under a specific applied potential, reduction or oxidation of the complex occurs, creating a surplus or deficit of electrons directly proportional to the amount of bound target molecule.

Question 4

What is biofouling and how does it affect biosensor performance?

Accepted Answer

Biofouling is the contamination of a biosensor surface by other molecules in complex samples, which can block probe molecules from sensing target molecules and greatly diminish detection ability. This challenge limits biosensor lifetime, requiring regeneration or disposal. To mitigate biofouling, researchers develop anti-biofouling coatings or design sensors with improved surface resistance to unwanted molecular binding.

Question 5

Why is detection limit important in biosensor design?

Accepted Answer

Detection limit refers to the lowest quantity of substance that can be reliably distinguished from its absence. A low detection limit is advantageous for detecting trace amounts with certainty, with single molecule detection being ideal. However, low concentrations produce weak signals below noise levels, making quantification difficult. Current research focuses on improving detection limits by enhancing binding efficiency and reducing noise.

Question 6

How does a quartz crystal microbalance detect molecular binding?

Accepted Answer

A quartz crystal microbalance (QCM) consists of two gold electrodes separated by a piezoelectric quartz crystal. When alternating current is applied, oscillations at a specific resonant frequency are induced. When molecules bind to the surface, this resonant frequency changes, allowing detection of target molecule binding and quantification of the amount bound.

Question 7

How do cantilever biosensors measure target molecule binding?

Accepted Answer

Specialized cantilevers are functionalized with probe molecules and exposed to target molecules. Upon binding, the cantilever deflects due to changes in surface stress. This deflection is measured using a laser, enabling detection of target molecule binding through mechanical property changes rather than optical or electrochemical signals.

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