Additional Lecture 5 Madam Noorulnajwa Diyana Yaacob

1. Introduction to biosensors 1.1 Definition 1.2 Biosensors 1.3 Components of a biosensor 1.4 Classification of biosensors 1.5 Performance factors of a biosensor 1.6 Applications of biosensors PTT104 BioSensors 2

A sensor is defined as a measuring device that exhibits a characteristic of an electrical nature (charge, voltage or current) when it is subjected to a phenomenon that is not electric. The electrical signal it produces must carry all the necessary information about the process under investigation. ERT 419 Sensors & control 3

A sensor could be regarded as a transducer, since it is a system that transforms one physical quantity into another. (which is a function of the first definition). PTT104 BioSensors 4

Transducer:  A device that is actuated by power from one system and supplies power usually in another form to a second system (a loudspeaker is a transducer that transforms electrical signals to sound energy).  A substance or device, such as a piezoelectric crystal, that converts input energy of one form into output energy of another. PTT104 BioSensors 5

Actuator:  A mechanism for moving or controlling something indirectly instead of by hand.  One that activates, especially a device responsible for actuating a mechanical device such as one connected to a computer by a sensor link. PTT104 BioSensors 6

The processor should be viewed as a general block  Microprocessor  Amplifier  Driver, Etc. Matching: between sensor/processor and processor/actuator PTT104 BioSensors 7

Example: Temperature control  Sense the temperature of a CPU  Control the speed of the fan to keep the temperature constant PTT104 BioSensors 8

In a biosensor, the phenomenon is recognized by a biological system called a bioreceptor, which is in direct contact with the sample and forms the sensitive component of the biosensor. The bioreceptor has a particularly selective site that identifies the analyte. PTT104 BioSensors 9

A commonly cited definition is:  A biosensor is a chemical sensing device in which a biologically derived recognition entity is coupled to a transducer, to allow the quantitative development of some complex biochemical parameter. PTT104 BioSensors 10

 A biosensor is an analytical device incorporating a deliberate and intimate combination of a specific biological element (that creates a recognition event) and a physical element (that transduces the recognition event). PTT104 BioSensors 11

Current definition:  A sensor that integrates a biological element with a physiochemical transducer to produce an electronic signal proportional to a single analyte which is then conveyed to a detector. PTT104 BioSensors 12 Biological element + Sensor element

A biosensor is a special type of sensor often used in bioanalysis. Humankind has been performing bioanalysis since the dawn of time, using the sensory nerve cells of the nose to detect scents and those of the tongue to taste dissolved substances. PTT104 BioSensors 13

Analogy with the nose as a sensor (it is actually a biosensor). PTT104 BioSensors 14

PTT104 BioSensors 15 Old time coal miners’ biosensor

As time has progressed, so has our level of understanding about the function of living organisms in detecting trace amounts of biochemicals in complex systems. The abilities of biological organisms to recognize foreign substances are unparalleled and have to some extent been mimicked by researchers in the development of biosensors. PTT104 BioSensors 16

The biosensor was born over fifty years ago, when Clark and Lyons (1962) had the idea of carrying out specific glucose concentration measurements by detecting the oxygen consumed during the enzymatic oxidation of this metabolite, catalysed by glucose oxidase, using an electrochemical sensor. PTT104 BioSensors 17

The enzyme was used in solution, confined to the end of the sensor.  In parallel, during the 1960s, more & more studies were being carried out on the properties of immobilised enzymes & their use. PTT104 BioSensors 18

PTT104 BioSensors 19 Father of biosensor Professor Leland C Clark Jnr (1918–2005)

General arrangement of a biosensor PTT104 BioSensors 20

A biosensor can be generally defined as a device that consists of two basic components connected in series: (1) a biological recognition system (bioreceptor) (2) a transducer. The basic principle of a biosensor is to detect analyte (molecular recognition) and to transform it into another type of signal using a transducer. PTT104 BioSensors 21

Concept of a biosensor PTT104 BioSensors 22

1. The Analyte (What do you want to detect?) Molecule - Protein, toxin, peptide, vitamin, sugar, metal ion. 2. Sample handling (How to deliver the analyte to the sensitive region?) (Micro) fluidics – Concentration increase / decrease, Filtration/selection PTT104 BioSensors 23

3. Detection/Recognition (How do you specifically recognize the analyte?) 4. Signal (How do you know there was a detection?) PTT104 BioSensors 24 Microfluidic device

A bioreceptor is a biological molecular species (e.g., an antibody, an enzyme, a protein, or a nucleic acid) or a living biological system (e.g., cells, tissue, or whole organisms) that utilizes a biochemical mechanism for detection / recognition. The sampling component of a biosensor contains a biosensitive layer that can contain bioreceptors or be made of bioreceptors covalently attached to the transducer. PTT104 BioSensors 25

Examples of biosensor: PTT104 BioSensors 26 Pregnancy test: To detects the hCG protein in urine. Glucose monitoring device (for diabetes patients): To monitor the glucose level in the blood. Infectous disease biosensor

Examples of biosensor: PTT104 BioSensors 27 Biosensor for research works Ring Sensor Smart Shirt

Biosensors can be classified by either bioreceptor or transducer type. Transduction can be accomplished through a large variety of methods. PTT104 BioSensors 28

PTT104 BioSensors 29 Biosensor classification schemes

In this course, we focus on THREE main classes: (1) optical detection methods, (2) electrochemical detection methods, (3) mass and acoustic based detection methods. Other detection methods include voltaic, magnetic, thermal methods. PTT104 BioSensors 30

1. Selectivity:  It is rare to find a sensor which will respond to only one analyte, although some do exist.  It is more usual to find a sensor that will respond mainly to one analyte, with a limited response to other similar analytes. PTT104 BioSensors 31

2. Sensitivity:  Range, Linear Range and Detection Limits. 32 Linear range Range

3. Time Factors: While it is desirable for a sensor to have a rapid response time and to recover rapidly, ready for the next reading, this is not always the case in practice.  Most sensors, whether chemical or biological, have a limited lifetime. PTT104 BioSensors 33

i) Response time:  Many analytical devices require some ‘settling- down’ time, i.e. time to allow the system to come to equilibrium. ii) Recovery time:  the time that elapses before a sensor is ready to be used for another sample measurement. PTT104 BioSensors 34

iii) Lifetimes:  All organic material deteriorates with time, especially when taken out of its natural environment.  This means that one of the main drawbacks of biosensors is that the biological material usually has a fairly limited lifetime before it needs replacing.  Generally pure enzymes have the lowest stability, whereas tissue preparations have the highest. PTT104 BioSensors 35

4. Precision, Accuracy and Repeatability For any analytical instrument, including sensors, the analytical value must have sufficient precision for the required purpose,  i.e. the random errors must be below a certain level, so that repetitive measurements are reproducible within a certain range. The sensor must also be capable of measurements of values with an accuracy close to the expected value. 36

 This means that the systematic errors must be below certain limits.  This can be a particular problem where biological selective elements are used, as one sample can differ from another, thus giving systematic errors. Sufficient controls and standards must be used to enable repeatable results of sufficient accuracy to be obtained over an extended period. PTT104 BioSensors 37

AreaExampleRemarks Health care1.Measurement of Metabolites 2.Diabetes Blood chemistry: instant assays Insulin Therapy: glucose- insulin management Industrial Process Control 1. Bioreactor Control Real-time monitoring of carbon sources, dissolved O2, CO2 & products of metabolism: optimization, ↑ product yields, ↓processing & material cost PTT104 BioSensors 38

AreaExampleRemarks Military & Homeland Security 1. Detection of chemical and biological warfare agents Rapid analysis: monitoring hazards due to terrorist activity. Environmental Monitoring 1. Environmental Protection Agency (EPA) Air and Water Monitoring Environmental analytes: biological oxygen demand (BOD), atmospheric acidity, and river water pH, detergent, herbicides, & fertilizer concentrations in drainage and river PTT104 BioSensors 39

PTT104 BioSensors 40