BIOELECTRONICS AND SAFETY/SECURITY
Common aim of much biological/medical diagnostic research and security research
• detection of biological organisms and organic molecules • detection of drugs and explosives at ports and airports;• detection of drugs in general;
Other areas of medical research, e.g. epidemiology, may also play a role in wider considerations of chemical and biological
defence strategies.
BIOSENSOR TECHNIQUESMAY BE USEFUL
PHYSICALTRANSDUCER
Electronic, e.g. FET
Electrochemical, e.g Graphite/Ag-AgCl electrodes
Optical, e.g. fibre or planar waveguides
BIOLOGICAL MOLECULE:
ENZYMES
ANTIBODIES
Gives the sensor specificity to complex organic molecules
Most efforts at developing PCR technology have been aimed at the HTS laboratory where parallelism and automation are used to maximise throughput. For point-of-care or field testing, new approaches are required to allow the rapid processing of single or low numbers of discrete samples. Remote testing often requires that the test has to be carried out by unskilled operators and it may not be possible, in the field, to utilise the control measures used routinely within the lab to minimise contamination.
Martin A Lee, Identification Group, Dstl Porton Down
Flow through Evanescent Field Immunosensor
Thick (multimode)optical fibre
Immobilised captureantibody on the
surface of the fibre
Light out to opticalprocessing
Chemiluminescentimmunoassay
reagentsflow through
Succesfully developed at Dstl
Porton Down
but need extensive support to collect, concentrate and
measure the analyte
CycloneConcentrator
Airsampler
AqueousBuffer
AssayReagents
BiosensorArray
DisplaySensorOutputs
Controlcircuitry
Airbornethreat
Detection of air-borne agents at low concentrations
Best suited to a large vehicle
Combined Water Filter and Optical Immunosensor
MULTI-ANALYTE TESTING COMMONTO BOTH AREAS
EXAMPLE, DRUGS OF ABUSE
Acetaminophen
Amphetamine/ Methamphetamine
Barbiturates
Benzodiazepines
Benzodiazepines-Serum
Cannabinoids
Cocaine Metabolite
Ethanol
Methadone
Opiates
Phencyclidine II
Propoxyphene
Salicylate
Tricyclic Antidepressants
CHEMICALLY SENSITIVE FET CHIP:A technique with potential in multi-gate sensing
ENCAPSULATEDAREA
METALCONTACT PADS
BARE GATE:OVERLAY WITH THIN FILMCONTAINING ORGANIC ORBIOMOLECULE, e.g.IONOPHORE: VALINOMYCINENZYME: PENICILLINASE
BARE GATE FETs
FET (conventional)
50 m
RESPONSE OF A POTASSIUM SENSITIVE FETGate membrane - Valinomycin : Dioctyl phthalate : PVC 1:64:35
This success has not been carried through to more relevant analytes
Gat
e co
mp
ensa
tion
vol
tage
con
stan
t I d
s
Penicillin concentration / M
Gat
e co
mp
ensa
tion
vol
tage
con
stan
t I d
s
Vg / m
V
RESPONSE OF A PENICILLIN SENSITIVE FETGate membrane - Penicillinase entrapped in polyacrylamide
Extension from enzyme-based to antibody based FETs is desirable
FLUORESCENT SANDWICH IMMUNOASSAY
UNBOUND LABELLED ANTIBODY
BOUND LABELLED ANTIBODY
ANALYTECAPTURE ANTIBODY
SUBSTRATE (e.g. glass or plastic)
FLUOROPHORE
A standard immunoassay procedure
Metabolites
Therapeutic drugs
Small hormones
Protein hormones
Antibodies
Cellular antigens
Viral antigens
Tumour antigens
Analyte concn
moles / litre10-12 10-210-10 10-8 10-410-6
GlucoseTheophyllineDigoxin
Oxytocin Aldesterone Cortisol
Insulin hCGIgM
Rh
Hepatitis
Influenza (elderly) Influenza (Paediatric)
- foetoprotein
106 1016108 1010 10141012Analyte molecules per cm3
Water = 3.3x1022
Low concentration detection essential in both areas
CAPILLARY FILL FLUORESCENCE IMMUNOSENSOR (Manufacture based on LCD cell fabrication)
BUFFERLAYER
UPPER GLASS FACE
THIN FILM WAVEGUIDE
LOWER GLASS FACE
EQUILIBRIUM RESPONSE CURVESensitivity lost on incorporation into CFFD sensor
CAPILLARY FILL FLUORESCENCE IMMUNOSENSOR Internal Standards – important in both remote sensing and
in medical sensing (to meet FDA requirements)
BIOSENSORS AND SAFETY/SECURITY
• Sensitivity - sacrificed - major problemMicrofluidics looks hopeful but yet to deliver
• Multigate devices Several analytes High specificity – several epitopes
Lack of a single detector moleculearray processing e.g. neural net
Internal calibration