In medical diagnostics, rapid detection of pathogenic bacteria from body fluids is
one of the basic issues. Most state-of-the-art methods require optical labeling, increasing
the complexity, duration and cost of the analysis. Therefore, there is a strong need
for developing selective sensory devices based on label-free techniques, in order
to increase the speed, and reduce the cost of detection. In a recent paper, we have
shown that an integrated optical Mach-Zehnder interferometer, a highly sensitive all-optical
device made of a cheap photopolymer, can be used as a powerful lab-on-a-chip tool
for specific, labelfree detection of proteins. By proper modifications of this technique,
our interferometric biosensor was combined with a microfluidic system allowing the
rapid and specific detection of bacteria from solutions, having the surface of the
sensor functionalized by bacterium-specific antibodies. The experiments proved that
the biosensor was able to detect Escherichia coli bacteria at concentrations of 106
cfu/ml within a few minutes, that makes our device an appropriate tool for fast, label-free
detection of bacteria from body fluids such as urine or sputum. On the other hand,
possible applications of the device may not be restricted to medical microbiology,
since bacterial identification is an important task in microbial forensics, criminal
investigations, bio-terrorism threats and in environmental studies, as well.
