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Introduction to Biosensors. 2007 Mattias Rudh www.realtimebiosensor.com. Definition of a biosensor. A biosensor:

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introduction to biosensors

Introduction to Biosensors

2007 Mattias Rudh

www.realtimebiosensor.com

definition of a biosensor
Definition of a biosensor

A biosensor:

A device that uses specific biochemical reactions mediated by isolated enzymes, immunosystems, tissues, organelles or whole cells to detect chemical compounds usually by electrical, thermal or optical signals. Source:

PAC, 1992, 64, 148 (Glossary for chemists of terms used in biotechnology.)

biosensor breakdown
Biosensor breakdown

Analyte

Response

Detection

Sample handling/preparation

Analysis

Signal

the analyte
The Analyte

What do you want to detect?

MoleculeProtein, toxin, peptide, vitamin, sugar, metal ion

Cholera toxin

Glucose

sample handling
Sample handling

How to do deliver the analyte to the sensitive region?

  • (Micro) fluidics
  • Concentration (increase/decrease)
  • Filtration/selection
example biosensor application
Example: Biosensor Application

How to do deliver the analyte to the sensitive region?

Collection wand

detection recognition
Detection/Recognition

How do you specifically recognize the analyte?

Fab

Active site

Membrane receptors

Competitive binding

Fc

Antibody

Enzyme

Cell

Polymer/Hydrogel

signal
Signal

How do you know there was a detection?

Specific recognition?

Common signaling principles

Optical (SPR, ELM, IR)

Electrical (Voltammetry, Potentiometry, Conductivity)

Electromechanical (QCM)

Thermal

Magnetic

Pressure

Often the detector is immobilized on a solid support/sensor

avoiding false signals
Avoiding false signals

False specific recognition?

Specific recognition

Non specific signal

improving performance
Improving performance

Secondary signal amplifier

Highly specific detection

Magnectic bead, fluorecent dye, enzyme etc

Inert background

v

v

v

regeneration or single use
Regeneration or single use?

Break binding

Low and high pH buffers

pH~1 and pH~13

v

v

v

data analysis
Data Analysis

R

t

Response variable (R) vs time(t):Example of response variables:Refractive indexPotentialCurrentFrequencyMassPressureTemperature

baseline
Baseline

Should be stable when there is no binding

Drift baseline

Stable baseline

t

t

Quantifying DriftShift in the baseline (RMS) shown as response units per time

Quantifying NoiseRoot mean square (RMS) of a sample of data points for a given time

sensitivity
Sensitivity

Signal-to-noise ratio

Per time unit

t

Spikes

Rapid (1 datapoint!) shift in signal

Baseline shift

Rapid (1 datapoint!) shift in baseline (offset)

t

t

common signal error sources
Common signal error sources

Inhomogenous sample

Bubbles/flow artifacts

Temperature

Electromagnetic interferance

Electronic unstability

Unstable chip/detection layer

improved sensitivity
Improved sensitivity

Output signal

R=R1-R2 or R=R1/R2

The reference is exposed to the same kind of disturbances as the active sensor. These effects are cancelled out by taking the difference between the two sensors

Reference sensorCoated with inert material does not detect the analyte

Active sensordetects the analyte

R1

R2

Sample

t

R

R1

R2

t

t

signal interpretation
Signal interpretation

Visual (example pregnancy test)

Automatic (Software)

Manual (Research Biosensor)

kinetic evaluation
Kinetic evaluation

Binding / no binding

Affinity (Ka / Kd and k_on and k_off)

example of biosensors
Example of biosensors

Pregnancy test

Detects the hCG protein in urine. Interpretation and data analysis performed by the user

Glucos monitoring device (for diabetes patients)

Monitors the glucose level in the blood. Interpretation and data analysis performed by a microprocessor.

example of biosensors20
Example of biosensors

Infectous disease biosensor from RBS

Data analysis and interpretatoin performed by a microprocessor

Old time coal miners’ biosensor

Data analysis and interpretation performed by the coal miner.

research biosensors
Research Biosensors

Biacore Biosensor platform

General and flexible, good tool for development of specific biosensors

For a comprehensive list of research biosensor suppliers see:

www.realtimebiosensor.com