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

Biosensor Definition Surface Chemistry Biology Physics Photonics etc Electrochemistry Microelectronics

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.

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

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

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.

A microarray is a set of probes printed onto a solid support Solid support is usually a glass slide with surface chemistry modifications Printing can be done in contact and non-contact modes. Microarrays can also be fabricated using photolithography (Affymetryx)

Biomedical Profiling

HCMV Genome Study

What is RLS and why do we need it? The Problem Arrays have previously required >25ug 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. Clinical advantages of alternative labelling methods

Intense Scattered Monochromatic Light nm-sized Particle Oscillating Electrons Scattered light is a function of particle size, composition, and shape Incident Polychromatic Light

RLS principle White light gets scattered by the oscillating gold particles, causing a quantitative colour light signature.

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,

Biosite ‘Triage’ System Diagnostic for Congestive Heart Failure (CHF) Cardiac Markers in Blood Antibody Array Microfluidics Capillary Fill

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

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.

Multiplexed viral detection (DeRisi et al 2002, PNAS 99, 15687) Long oligonucleotide DNA arrray –1600 unique viral oligos from 140 distinct viral genomes