BG3105 Biomedical Instrumentation PDF

BG3105 Biomedical Instrumentation Faculty : Prof Chen Peng School : School of Chemistry, Chemical Engineering and Biotechnology (CCEB) Email : [email protected] Office : N1.3-B3-08 Biosensors  Biosensors Topic Objectiv...

BG3105 Biomedical Instrumentation Faculty : Prof Chen Peng School : School of Chemistry, Chemical Engineering and Biotechnology (CCEB) Email : [email protected] Office : N1.3-B3-08 Biosensors  Biosensors Topic Objectives At the end of this topic, you should be able to: Define a biosensor Identify the components of a biosensor Describe different types of biosensors and their biomedical applications Explain the working principles of these biosensors Explain nanotechnology for biosensing Introduce the new frontiers of biosensing 2  Biosensors Definition of Biosensor Biosensor is a device that converts a clinically or biologically relevant compound or signal to a measurable signal (electrical, optical, etc.), and provides quantitative or semi-quantitative analytical information (e.g., concentration, magnitude, kinetics). Click here to watch ‘Biosensors – An Introduction by Anthony Turner’. 3  Biosensors Commercial Examples of Biosensors Glucose meter: Monitors the glucose level in the blood. Pregnancy test: Detects the hCG protein in urine based on enzyme-linked immunosorbent assay (ELISA). Breathalyer Detect ethanol, virus, or biomarkers from a breath, e.g., a breathalyzer for screening tuberculosis in a few minutes at the Point-of- Care. Click here to view ‘Pregnancy Test’. 4  Biosensors Functions of a Biosensor A biosensor may detect: Chemicals or ions related to bio-functions. Small biomolecules (e.g., glucose, hormones). Macromolecules (e.g., proteins or DNAs). Mammalian cells or Microorganisms. A biological function or activity (e.g., bioelectricity, enzymatic reaction). At: molecular, cellular, tissue, or body level. In vitro: Measuring from, e.g., blood samples or other bio-fluids (e.g., urine, saliva, sweat), cell culture, tissue slices. Or in vivo: Measuring from or in human or animal bodies. 5  Biosensors Components of a Typical Biosensor Recognition Element: Immobilized on (or integrated in) sensor and specifically interact with the target analyte. Sensing Element (or Transducer): Translate the interaction (binding, reaction, etc) between recognition element and analyte into a measurable and quantifiable signal (e.g., electrical, electrochemical, optical, mass, and heat). Output Component: Output signal in user-friendly manner; often with associated electronics. 6  Biosensors Components of a Typical Biosensor Antibody DNA Biological Microorganism Recognition Element Enzyme Receptor Interface Chemistry Signal Transducer Sensing Material Optical Electrical Physical Chemical Process & Display 7  Biosensors Components of a Typical Biosensor Electrical signal: current, voltage Optical signal: fluorescence, color, absorbance, reflection, Raman Physical signal: temperature, weight, displace, vibration Chemical signal: pH, chemicals Usually, the last 3 types of signals are converted into electrical signal for easy processing and display. 8  Biosensors Components of a Typical Biosensor Analyte Receptor Transducer Charge Electrode Biological Transfer Receptors pH pH Meter Change Electric Heat Thermistor Signal Light Photon Artificial Counter Receptors Mass Piezoelectric Change Device Molecularly Signal Transducer Recognizing Materials 9  Biosensors Analytes in Blood Critical-Care Analytes and Their Normal Ranges in Blood Blood Gases and Electrolytes Metabolites Related Parameters PO2 80-104mm Hg Na+ 135-155mmol/l Glucose 70-110mg/ 100ml PCO2 33-48mm Hg K+ 3.6-5.5mmol/l Lactate 3-7mg/ 100ml pH 7.31-7.45 Ca2+ 1.14-1.31mmol/l Creatinine 0.9-1.4mg 100ml Hematocrit 40-54% Cl- 98-109mmol/l Urea 8-26mg/ 100ml Total 13-18g/ 100ml Hemoglobin O2-saturation 95-100% Collison, M. E. and Meyerhoff, M. E. (1990). Chemical Sensors for Bedside Monitoring of Critically Ill Patients. Analytical Chemistry, 62, 425A-437A. Important analytes and their normal ranges in blood, which indicate the physiological status of the body: gas pressure and related parameters, electrolytes and metabolites. 10  Biosensors Analytes in Blood Examples of Arterial Blood Gases in Different Clinical Situations Nickerson, B. G. and Monaco, F. (1988). Carbon Dioxide Electrodes, Arterial and Transcutaneous. In Webster, J. G. (ed.). Encyclopedia of Medical Devices and Instrumentation. New York: Wiley. 564-569. 11  Biosensors Father of Biosensors Professor Leland C Clark Jr. (1918–2005) The inventor of the Clark electrode, a device used for measuring oxygen in blood, water and other liquids. Developed the first and now the most widespreadly used commercial biosensor: the blood glucose biosensor in 1962. 12  Biosensors History of Biosensors 1916 First report on immobilization of proteins: adsorption of invertase on activated charcoal 1922 First glass pH electrode 1956 Clark published his definitive paper on the oxygen electrode 1962 First description of a biosensor: an amperometric enzyme electrode for glucose (Clark) 1969 Guilbault and Montalvo – First potentiometric biosensor: urease immobilized on an ammonia electrode to detect urea 1970 Bergveld – Ion Selective Field Effect Transistor (ISFET) 13  Biosensors History of Biosensors 1975 Lubbers and Opitz described a fibre-optic sensor with immobilised indicator to measure carbon dioxide or oxygen 1975 First commercial biosensor (yellow springs instruments glucose biosensor) 1975 First microbe-based biosensor, first immunosensor 1980 First fibre optic pH sensor for in vivo blood gases (Peterson) 1982 First fibre optic-based biosensor for glucose 1983 First Surface Plasmon Resonance (SPR) immunosensor 1984 First mediated amperometric biosensor: ferrocene used with glucose oxidase for glucose detection 14  Biosensors History of Biosensors 1987 Blood-glucose biosensor launched by MediSense ExacTech 1990 Surface Plasmon Resonance (SPR) based biosensor by Pharmacia BIACore 1992 Hand held blood biosensor by i-STAT 1996 Launching of Glucocard 1998 Blood glucose biosensor launched by LifeScan FastTake Current Sensors based on nanotechnologies enabled by nanomaterials or nanostructures 15  Biosensors Electrochemical Sensors Operation of electrochemical sensors is based on charge transfer or charge accumulation occurring at the electrode surface. Amperometric sensors measure the current between the working electrode and the reference electrode while a constant voltage is applied. The applied voltage can also be a defined time-varying waveform. Potentiometric sensors measure the potential difference between the working electrode and the reference electrode while a constant current (e.g., 0) is applied. The applied current can also be a defined time-varying waveform. 16  Biosensors Electrochemical Sensors Clark-type O2 Electrode Semipermeable Membrane Exit e– Cathode Voltage Source 0.7V For blood or + - calibrating Anode gas O2 – AgCl-Ag0 O2 (Dissolved) e Entrance Ammeter Sample Chamber At platinum cathode: O2+2H2O+4e- - 2H2O2+4e- 4OH- 4OH-+4KCl 4KOH+4Cl- (O2 is reduced) At Ag/ AgCl anode: 4Ag+4Cl- 4AgCl+4e- (Ag is oxidized) 17  Biosensors Electrochemical Sensors Clark-type O2 Electrode It is an amperometric sensor The measured current is proportional to O2 concentration For an amperometric sensor: At cathode: Reduction reaction occurs: electrons are given from the electrode to the reaction (current flows into the electrode). At anode: Oxidation reaction occurs: electrons are given from the reaction to the electrode (current flows out of the electrode) 18  Biosensors Electrochemical Sensors Glucose sensor: Use of enzyme (glucose oxidase - GOx) and its co-factor (flavin adenine dinucleotide - FAD), and mediator (e.g., ferrocene -Fe(cp)). Oxidation Reduction GOx (FAD) Enzyme GOx (FADH2) Oxidation Reduction 2 Fe(cp) Mediator 2 Fe(cp)+ Oxidation Electrode 2e- Click here to watch ‘Glucose Sensors for Diabetes’. 19  Biosensors Electrochemical Sensors Glucose sensor: reaction chain (electron transfer route) 1. Oxidation of glucose catalyzed by GOx Glucose + O2 GOx Gluconic acid + H2O2 Glucose + GOx(FAD) Gluconic acid + GOx(FADH2) Actually: and GOx(FADH2) + O2 GOx(FAD) + H2O2 2. Reaction of mediator (M = e.g., ferrocene) GOx(FADH2) + Mox GOx(FAD) + Mred + 2H+ and Mred+ e– anode Mox 20  Biosensors Electrochemical Sensors Potentiometric pH sensor Potentiometric ion sensor (Na+, K+, Ca2+, Cl-,…) 21  Biosensors Electrochemical Sensors For a potentiometric sensor: At working Charges accumulate due to selective passage electrode: through a selective membrane or generation by an electrochemical reaction occurring at the electrode surface, or combination of the above. Potential Theoretically, the measured voltage difference signal: between the working and reference electrodes linearly scales with (RT/zF)ln(C), where z and C are the valence and concentration of the analyte, respectively. For example, H+ concentration increases by 10 folds (i.e., pH value decreases by 1) at 25 ˚C, the potential signal increases by 59.16 mV (theoretical maximum) 22  Biosensors Optical Sensors A pulse oximeter is a medical device that indirectly monitors the oxygen saturation of blood: The principle of pulse oximetry is 99 82 based on the red (R) and infrared (IR) light absorption characteristics of oxygenated and deoxygenated hemoglobin. R IR Oxygenated hemoglobin absorbs more infrared light and allows more red light to pass through. Conventional Emitter/Detector Deoxygenated (or reduced) hemoglobin absorbs more red Photodetector light and allows more infrared light to pass through. Click here to read ‘Principles of Pulse Oximetry Technology’. Click here to watch ‘Pulse Oximetry’. 23  Biosensors Sensors Based on SPR Surface plasmonic resonance (SPR) based sensors detect refractive index changes on a surface upon analyte binding. Principle of SPR used in Biacore™ Systems Optical Light- Detection Resonance Source Unit Signal Polarized Reflected Time Light Light Prism Sensorgram Sensor Surface with Gold Film Sample Flow Channel Click here to watch ‘Surface Plasmon Resonance Explained’. 24  Biosensors Sensors Based on SPR Working principle of SPR sensor: At metal-dielectric interface, surface plasmon forms (periodic oscillation of electrons on metal surface). When the incident light beam has the right incidence angle, surface plasmon resonance occur. At this so-called ‘resonance angle’, θ, optical energy is coupled into the metal (usually, Au) surface. As a result, reflection is decreased at this resonance angle. Molecular binding at the interface changes θ Advantages of SPR sensor: Sensitive, fast Without need to label the targeted molecule Real-time monitoring binding / dissociation kinetics Only require a small amount of sample 25  Biosensors Ion-Sensitive Field-Effect Transistor Working principle of Ion- Reference Sensitive Field-Effect Transistor (ISFET): Sample Target ions, which pass Ion-Selective Membrane Si3N4 through the ion- Insulator (Gate) selective membrane Layer SiO2 Source Drain and accumulate at the Vgs n-Si n-Si gate, change the conductance of the FET Substrate p-Si due to field-effect hence leading to measurable electrical Vds signal. Recall FET concept in year 2 electronics course Note the difference to electrochemical ion detection Click here to watch ‘How MOSFETs and Field-Effect Transistors Work’. 26  Biosensors Piezoelectric Biosensors Piezoelectric devices: Utilize crystals, such as quartz, which vibrate under the influence of an electric field. The frequency of this vibration changes upon binding of target biomolecules due to mass increase. Non-Specific Antigen Antigen Quartz Crystal Antibody Microbalance Protein Gold Electrode Crystal Substrate Gold Electrode Click here to watch ‘QCM Biosensor (Immunosensor)’. 27  Biosensors Characterizing a Biosensor 1. Selectivity (or specificity): Interference from other chemicals or molecules must be minimized. 2. Lower detection limit (LDL): Minimal detectable target concentration (signal to noise ratio >3). 3. Sensitivity: Ratio of change between response and concentration. 4. Dynamic range of detection: LDT to the threshold concentration that causes saturation of response (or higher detection limit – HDL). 28  Biosensors Characterizing a Biosensor 5. Response time: Time necessary for achieving 95% of the stable response. 6. Linearity: Response is linearly scaled with concentration. 7. Reproducibility: Consistency of response to a given sample. 8. Cost: For both raw materials and fabrication. 9. Convenience of measurement 29  Biosensors Nano-Biosensors Offering new sensing possibilities: Because new phenomena arise at nanoscale. Better sensitive and selectivity: Because of larger surface-volume ratio, ability to intimately interact with molecular targets, taking advantage of new phenomena. Faster response, less power and sample consumption: Because they are miniaturized. Normal Scale Nanoscale Nanotechnology: Plays by different rules Detects at nanoscale Uses molecular-sized nanomaterials or fabricated nanostructures 30  Biosensors Nanotechnology for Biology Nanotechnology provides unprecedented opportunities for biomedicine because you need small tools to probe small targets. Nanomaterials and Bio-Entities Share Similar Length Scale 0D Graphene QD 2D Graphene Sheet 0D Nanopore 1D NW 1D NW 1D CNT 0D Semi-QD 1D CNT 0.1nm 1nm 10nm 100nm 1µm 10µm 100µm Ions Small Molecules Proteins Virus Cell Organelles Bacteria Animal Cells 31  Biosensors Electrochemical Nano-sensors Nanomaterials to modify the electrode, whereby enhancing the electrochemical signals by Increasing active surface area Anchoring and stabilizing the biocomponents (e.g. enzymes) Facilitating charge transfer between electrochemical reaction(s) and electrode Catalyzing the electrochemical reaction(s) Electroanalysis, 31:1925, 2019 32  Biosensors Nanoelectronic FET Sensors Field-Effect Transistor (FET) sensors based on silicon nanowires (SiNW) or carbon nanotubes(CNTs): As the current carriers flow completely (as for CNT) or largely (as for SiNW) on the surface, their conductance is extremely sensitive to the minute electrical or electrochemical perturbation at the vicinity. SiO2 Si 10-50 nm 1-2 nm SiNW CNT 33  Biosensors Nanoelectronic FET Sensors Immunosensor based on SiNW- or CNT-FET: Binding of electrically charged antigens onto immobilized antibodies alters the FET conductance due to electrostatic gating (field-effect), whereby leading to measurable electrical current change from the voltage biased (between D and S) FET sensor. Buffer Target Receptor Passivation Source Drain Electrode Electrode (S) (D) SiNW/ CNT Dielectric Gate Electrode Substrate 34  Biosensors Nanoelectronic FET Sensors PH sensor based on SiNW-FET: De-protonation of APTES groups functionalized on p-type SiNW increase nanowire conductance. nanoFET nanosensor S D S D NW NW backgate SiNW SiNW SiNW SCIENCE, 293:1289, 2001 35  Biosensors Nanoelectronic FET Sensors Protein sensor based on SiNW-FET: Negatively-charged streptavidin increases the conductance of biotin-functionalized p-type SiNW. 36  Biosensors Nanoelectronic FET Sensors Detecting biopotentials using SiNW-FET Extracellular biopotential caused by an action potential in a neuron is translated into SiNW current signal. The ionic current flowing through the resistive nanogap between SiNW and cell membrane changes the extracellular potential at the gap (∆V =R*∆I) which, in turn, gates the SiNW current (field-effect). Refer to the figure in the next slide. 37  Biosensors Nanoelectronic FET Sensors A B 1 5 36nS NW1 10 15 NW49 4.3msec 20 25 30 90nS 35 40 20msec 45 50 Science, 313:1100, 2006 38  Biosensors Nanoelectronic FET Sensors Vertical nanowire electrode array for intracellular recording of biopotential in neuronal circuits Nature Nanotechnology, 7:180, 2012 39  Biosensors Nanoelectronic FET Sensors Intracellular recording of action potentials and biomolecular sensing using kinked SiNW-FET probe Science, 329:830, 2010; Nanotoday, 38:101135, 2021 40  Biosensors Nano-Cantilever Based Biosensors Cantilever is coated with a chemically selective layer (e.g., antibodies). Deflection of cantilever can be measured precisely by deflecting a light beam from the surface. Cantilever bends upon molecular binding due to surface stress. Click here to watch ‘Cantilever Animations’. 41  Biosensors Nanopore Technology Translocation of a molecule (e.g., DNA) produces a characteristic ionic blockage current. I(t) V Ag/AgCI+ CI- K+ Membrane K+ CI- ultrafast DNA sequencing Ag/AgCI+ solid-state nanopore 42  Biosensors Nanopore Technology protein nanopore Click here to watch ‘Oxford Nanopore Technologies’. 43  Biosensors Colorimetric Biosensors Colorimetric biosensors based on gold nanoparticles: A DNase I Gold nanoparticles (AuNPs) are colored, due to localized surface plasma resonance. B S1 The color depends on the S2 particle size and the distance between particles. C -DNase I +DNase I Aggregated blue AuNPs (crosslinked by DNAs) turn to red as they separate apart after DNase cleaves the linking DNA strands. 44  Biosensors Wearable Biosensors Home-based long-term monitoring based on wearable biosensors is instrumental to: management of chronic diseases Care for senior and disabled Wearable biosensors are also useful for Wearable sensors can be printed directly human-machine onto skin. interface https://newatlas.com/wearables/wearable- sensors-printed-skin-room-temperature/ 45  Biosensors Implantable Biosensors Advantages: long-term monitoring accurate, high signal-to- noise ratio can access internal sites immune to environmental disturbances operate unconsciously Challenges: invasive adverse biological reactions powering data transmission 46  Biosensors Organic Electrochemical Transistors Working principle of Organic Electrochemical Transistor Off (OECT): Channel of OECT is made by conducting polymer (CP), whose conductivity depends on its reduction/oxidation state When target analyte is oxidized at gate, CP is On reduced. The channel current decreases in analyte concentration dependent manner. Example: OECT-based H2O2 sensor H2O2 is oxidized at gate, CP (PEDOT:PSS) is reduced, leading to current decrease. 47  Biosensors Organic Electrochemical Transistors Advantages Flexibility: wearable sensors Biocompatibility: implantable sensors Much more sensitive than the conventional FETs OECT-based sweat sensor for uric acid detection Science advances 4.7 (2018): eaar2904. OECT-based sweat sensor for cortisol detection Adv. Mater 27.4 (2015): 676-681. 48  Biosensors Volatile Organic Compound Sensors Human breath contains >1000 volatile organic compounds (VOCs). Some can serve as biomarkers for diseases. Metabolic pathways for generation of VOCs Diseases VOCs in breath Diabetes Acetone 2-methylheptane, styrene, Lung Cancer propylbenzene, decane, and undecane Chronic kidney disease 4-heptanone Trends in Analytical Chemistry 33 (2012): 1-8. 49  Biosensors Volatile Organic Compound Sensor FET-based electronic noses (e-noses): Semi-conductive material, that serves as the FET channel, absorbs VOC molecules, leading to changes in surface charge and thus the channel conductance. Semi-conductive materials used in e-nose Metal oxides Conducting polymer MoS2 Reduced graphene oxide (rGO) Advantages of e-noses rGO based e-nose for hexanol detection. Very high sensitivity Matter 4.7 (2021): 2553-2570. Rapid response Fast recovery 50  Biosensors Biosensor Development Biosensor development require multi-disciplinary fusion. AI Bioengineers are trained to take such challenges. 51  Biosensors Commercialization Commercialization of a Biosensor or Biodevice 52  Biosensors Commercialization Commercialization of a Biosensor or Biodevice 53  Biosensors End of Lecture 54