We describe the use of optical coherence tomography (OCT) for high-resolution, real-time imaging of three-dimensional structure and development of a Pseudomonas aeruginosa biofilm in a standard capillary flow-cell model. As the penetration depth of OCT can reach several millimeters in scattering samples, we are able to observe complete biofilm development on all surfaces of a 1 mm×1 mm flow-cell. We find that biofilm growing at the bottom of the tube has more structural features including voids, outward projections, and microcolonies while the biofilm growing on the top of the tube is relatively flat and contains less structural features. Volume-rendered reconstructions of cross-sectional OCT images also reveal three-dimensional structural information. These three-dimensional OCT images are visually similar to biofilm images obtained with confocal laser scanning microscopy, but are obtained at greater depths. Based on the imaging capabilities of OCT and the biofilm imaging data obtained, OCT has potential to be used as a non-invasive, label-free, real-time, in-situ and/or in-vivo imaging modality for biofilm characterization.
We present the design of two efficient micromixers, a 3-D serpentine micromixer and a vortex mixer. Light and confocal microscopy and image analysis programs were used to study mixing efficiency in these two micromixers and a Y-shape straight channel. By utilizing Optical Coherence Tomography (OCT), an emerging high-resolution medical and biological imaging technology, we obtained 3-D structural data and mixing dynamics for the 3-D serpentine mixer and the vortex mixer. The results indicate that mixing efficiency characterized with OCT is more accurate.
We present the use of DNA and peptide nucleic acid (PNA) molecular beacons (MBs) as sensitive indicators in microfluidic bioMEM devices. DNA and PNA MBs can be used to quantitatively study hybridization kinetics in real time in a polydimethyl siloxane (PDMS) microfluidic device. PNA MBs perform better than DNA MBs for the study of hybridization kinetics of rRNA targets in real time in microfluidic channels. We also demonstrate the use of PNA MBs for fast detection of bacterial cells in microfluidic channels. Using PNA MBs as detection probes will enable us to develop an integrated biosensor for the rapid and on-site detection and quantification of microbial pathogens in environmental and clinical samples.