Biomedical Instrumentation - Biosensors Quiz

Biomedical Instrumentation - BG3105

• Course Instructor: Prof Chen Peng
• School: School of Chemistry, Chemical Engineering and Biotechnology (CCEB)
• Email: [email protected]
• Office: N1.3-B3-08

Biosensors - Topic Objectives

• Define a biosensor
• Identify components of a biosensor
• Describe different types of biosensors and their biomedical applications
• Explain the working principles of biosensors
• Explain nanotechnology used in biosensing
• Introduce new frontiers in biosensing

Biosensors - Definition

• A biosensor is a device that converts a clinically or biologically relevant compound or signal into a measurable signal (electrical, optical, etc.)
• It provides quantitative or semi-quantitative analytical information (e.g., concentration, magnitude, kinetics).

Biosensors - Commercial Examples

• Glucose meter: Monitors blood glucose levels.
• Pregnancy test: Detects hCG protein in urine using ELISA.
• Breathalyzer: Detects ethanol, viruses, or biomarkers from breath. Used for tuberculosis screening.

Biosensors - Functions

• Detect chemicals or ions related to biological functions
• Detect small biomolecules (e.g., glucose, hormones)
• Detect macromolecules (e.g., proteins, DNA)
• Detect mammalian cells or microorganisms
• Detect biological functions or activities (e.g., bioelectricity, enzymatic reactions)
• Detection at molecular, cellular, tissue, or body levels
• In vitro: Measuring from/in blood samples, other biofluids (urine, saliva, sweat), cell cultures, tissue slices
• In vivo: Measuring from/in human or animal bodies

Biosensors - Components of a Typical Biosensor

• Recognition element: Immobilized or integrated into the sensor, specifically interacting with the target analyte.
• Sensing element (or transducer): Translates the interaction (binding, reaction, etc.) between the recognition element and analyte into a measurable/quantifiable signal (e.g., electrical, electrochemical, optical, mass, heat).
• Output component: Outputs the signal in a user-friendly manner, often with associated electronics.

Biosensors - Signals from Components

• Electrical signal: Current, voltage
• Optical signal: Fluorescence, color, absorbance, reflection, Raman
• Physical signal: Temperature, weight, displacement, vibration
• Chemical signal: pH, chemicals

Biosensors - Analytes in Blood

• Blood Gases: PO2 (80-104mm Hg), PCO2 (33-48mm Hg), pH (7.31-7.45)
• Electrolytes: Na+ (135-155 mmol/L), K+ (3.6-5.5 mmol/L), Ca2+ (1.14-1.31 mmol/L), Cl- (98-109mmol/L)
• Metabolites: Glucose (70-110 mg/100 mL), Lactate (3-7 mg/ 100mL), Creatinine (0.9-1.4 mg/100 mL), Urea (8-26 mg/100mL)

Biosensors - Electrochemical Sensors

• Operation: Charge transfer or accumulation at electrode surface
• Amperometric: Measures current between electrodes while a constant voltage is applied (e.g., Clark-type O2 electrode)
• Potentiometric: Measures potential difference between electrodes while a constant current is applied (e.g., pH sensor)

Biosensors - Optical Sensors

• Principle: Red (R) and infrared (IR) light absorption characteristics of oxygenated and deoxygenated hemoglobin.
• Oxygenated hemoglobin absorbs more IR light and transmits more red light.
• Deoxygenated hemoglobin absorbs more red light and transmits more IR light.

Biosensors - Sensors Based on SPR

• Principle: Detects refractive index changes on a surface upon analyte binding.
• Used in Biacore™ systems

Biosensors - Ion-Sensitive Field-Effect Transistor (ISFET)

• Principle: Target ions passing the ion-selective membrane, accumulating at the gate, change conductance due to field effect, resulting in a measurable electrical signal.

Biosensors - Piezoelectric Biosensors

• Principle: Utilizing crystals (e.g., quartz) that vibrate under an electric field.
• Vibration frequency changes upon target biomolecule binding due to mass increase

Biosensors - Nano-Biosensors

• Offer new sensing possibilities due to nanoscale phenomena. Offer better sensitivity and selectivity due to a large surface-to-volume ratio.
• Lead to faster response times and lower power consumption due to miniaturization
• Nanotechnology plays by different rules. Detects at nanoscale. Uses molecular-sized nanomaterials or fabricated nanostructures.

Biosensors - Electrochemical Nano-sensors

• Modifying electrode surfaces with nanomaterials to enhance electrochemical signals.
• Increasing active surface area
• Anchoring/stabilizing biocomponents
• Facilitating charge transfer
• Catalyzing electrochemical reactions

Biosensors - Nanoelectronic FET Sensors

• Based on silicon nanowires (SiNWs) or carbon nanotubes (CNTs).
• Conductiance extremely sensitive to minute electrical/electrochemical perturbations (SiNWs/CNTs).
• Immunosensors: Binding of electrically charged antigens to immobilized antibodies alter FET conductance
• PH sensors: De-protonation of APTES increases nanowire conductance
• Protein sensors: Negatively-charged Streptavidin increases conductance of Biotin-functionalized p-type SiNW
• Detecting biopotentials: Extracellular biopotential causes a change in SiNW current signal

Biosensors - Nano-Cantilever Based Biosensors

• Coating cantilevers with chemically selective layers (e.g., antibodies).
• Deflection measurements: Precisely measuring deflection using a light beam.
• Binding leads to cantilever bending due to surface stress.

Biosensors - Nanopore Technology

• Translocation of a molecule (e.g., DNA) creates characteristic ionic blockage current.
• Used for ultrafast DNA sequencing
• Protein nanopores

Biosensors - Colorimetric Biosensors

• Based on gold nanoparticles (AuNPs)
• Colored due to localized surface plasma resonance (LSPR).
• Color change depends on particle size/distance
• Aggregated blue AuNPs (crosslinked by DNA) become red after DNase cleaves the linking DNA strands.

Biosensors - Wearable Biosensors

• Home-based long-term monitoring
• Management of chronic diseases
• Care for seniors/disabled
• Human-Machine Interface
• Use of sensors that can be printed onto the skin

Biosensors - Implantable Biosensors

• Advantages: Long-term monitoring, accurate signal, access internal sites, immunity to environmental disturbances, operate unconsciously
• Challenges: Invasive methods, adverse biological reactions, powering, data transmission

Biosensors - Organic Electrochemical Transistors (OECTs)

• Principle: Channel conductivity (conducting polymer) is dependent on reduction/oxidation state.
• When target analyte is oxidized at gate, CP is reduced leading to channel current decrease in analyte concentration dependent manner.
• Advantages: flexibility, biocompatibility, greater sensitivity

Biosensors - Volatile Organic Compound (VOC) Sensors

• Human breath contains over 1000 VOCs. VOCs can serve as biomarkers for diseases.
• FET based electronic noses
• Semi-conductive materials (used in electron noses): Metal oxides (e.g., MoS2), Conducting Polymers (e.g., rGO).
• Advantages: high sensitivity, rapid response, fast recovery

Biosensors - Development

• Multi-disciplinary fusion required
• Bioengineers are trained to tackle the challenges

Biosensors - Commercialization

• Stages in commercialization of a biosensor/biodevice
• Customer focused market research
• Product definition
• Global market estimation
• Competition review
• Feasibility study
• Feasibility assessment
• Costing
• Development plan
• Intellectual Property
• Final product development
• Regulatory submission
• Regulatory compliance
• Global regulatory approvals
• Marketing & sales plans
• Sales forecast
• Manufacturing ramp-up
• Post-launch activities (clinical, service, marketing)

Biosensors - Commercialization Timeline

• Stages include idea submission, pre-clinical development (including 510 (k), FDA Review, and Reimbursement. Included timelines for these.

Test your understanding of biosensors with this quiz covering their definitions, components, types, and applications in biomedicine. Explore how nanotechnology enhances biosensing and learn about commercial examples like glucose meters and pregnancy tests. Prepare to delve into the captivating world of biosensors!