Biosensing

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Biosensing

• What does it mean?
• How do you do it?

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Biosensor Definition
Physics Photonics etc
Biology
Surface Chemistry
Electrochemistry Microelectronics
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• The feasibility of biosensing was first
  demonstrated by Leland Clark in the mid-1960s,
  when he measured glucose concentration in
  solution using what has since become known as the
  Clark oxygen electrode.
• Cooperation with industry goes back to the late
  seventies and resulted in the first biosensor
  based glucose analyzer in Europe in 1982
• Later that year the company licensed biosensor
  technology from Oxford University. Further
  developed at Cranfield University, the technology
  was patented worldwide in 1984.

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Optical biosensor

• Binding event leads to a measurable change in
  light emitted, absorbed or scattered.
• Easily read and multiplexed
• eg microarrays

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Electrochemical Sensor

• Binding event leads to a change in either
  current, potential or impedance.
• Easily miniaturised and integrated with
  microelectronics
• eg Glucose biosensor

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Introduction to microarrays

• Sets of probe molecules most commonly DNA or
  protein - immobilised on a solid substrate.
• Incubate with a complex mixture of target
  molecules and see what sticks.
• Visualise using (most commonly) fluorescent
  spectroscopy.

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A microarray is a set of probes printed onto a
solid support
Solid support is usually a glass slide with
surface chemistry modificationsPrinting can be
done in contact and non-contact modes.
Microarrays can also be fabricated using
photolithography (Affymetryx)
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Biomedical Profiling
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HCMV Genome Study
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Clinical advantages of alternative labelling
methods
What is RLS and why do we need it? The
Problem Arrays have previously required gt25ug of
total RNA per slide For some clinical projects
25ug is not realistic since it requires too large
a tissue sample.
The solution Alternative 1
amplify the RNA. Perfectly possible, but raises
questions of bias and validity. Costly and
labour intensive, prone to user
error. Alternative 2 new detection technology.
Resonance Light Scattering.
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Intense Scattered Monochromatic Light
Oscillating Electrons
Incident Polychromatic Light
Scattered light is a function of particle size,
composition, and shape
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RLS principle White light gets scattered by
the oscillating gold particles, causing a
quantitative colour light signature.
                                                                                                       
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Sample prep and detection on-chip
Microfabricated device does PCR and an
electrochemical microarray on a chip. Performed
detection of E. coli from a blood
sample. Grodzinski, Anal Chem 2004, 76,1824-1831
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Biosite Triage System http//www.biosite.com Dia
gnostic for Congestive Heart Failure
(CHF) Cardiac Markers in Blood Antibody
Array Microfluidics Capillary Fill
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Chip details

• Filter allows complex samples
• Microfluidics controls mixing
• Engineered energy transfer dyes allow efficient
  read-out

TRIAGE SYSTEM CARDIAC PANEL BNP TEST PROFILER
SHORTNESS OF BREATH PANEL D-DIMER TEST TOX DRUG
SCREEN DRUGS OF ABUSE PANEL C. difficile PANEL
PARASITE
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AmpliChip CYP450 Test    
Now cleared for in vitro diagnostic use in the US
and EU.

The world's first pharmacogenomic microarray designed for clinical applications.

The AmpliChip CYP450 Test is powered by Affymetrix technology. Provides comprehensive coverage of gene variations for the 2D6 and 2C19 genes, which play a role in the metabolism of about 25 of all prescription drugs. It is intended to be an aid for physicians in individualizing treatment doses for patients on therapeutics metabolized through these genes.

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Multiplexed viral detection (DeRisi et al 2002,
PNAS 99, 15687)

• Long oligonucleotide DNA arrray
• 1600 unique viral oligos from 140 distinct viral
  genomes