We report a novel technique for manufacturing polymeric microparticles containing biocatalysts by the behavior of immiscible liquids in microfluidic systems and in situ photopolymerization. The approach utilizes a UV-polymerizable hydrogel/enzyme solution and an immiscible oil solution. The oil and hydrogel solutions form emulsions in pressure-driven flow in microchannels at high values of the dimensionless capillary number (Ca). The resultant hydrogel droplets are then polymerized in situ via exposure to 365 nm UV light. This technique allows for the generation of monodisperse particles whose size can be controlled by the regulation of flow rates. In addition, both manufacturing microparticles and immobilizing biocatalysts can be performed simultaneously and continuously.

We report a highly sensitive optical imaging technology using surface-enhanced Raman scattering (SERS)-fluorescence dual modal nanoprobes (DMNPs). Fluorescence microscopy is a well-known imaging technique that shows specific protein distributions within cells. However, most currently available fluorescent organic dyes have relatively weak emission intensities and are rapidly photo-bleached. Thus more sensitive and stable probes are needed. In this work we develop DMNPs, which can be used for both SERS and fluorescence detection. SERS detection is a powerful technique that allows ultrasensitive chemical or biochemical analysis through unlimited multiplexing and single molecule sensitivity. Combining advantages of fluorescence and SERS allows these dual modal nanostructures to be used as powerful probes for novel biomedical imaging. In this work, the fabrication and characterization of the SERS-fluorescence DMNPs and application to biological imaging were investigated using markers CD24 and CD44, which are co-expressed in MDA-MB-231 breast cancer cells, as a model system. SERS imaging with DMNPs was found to be a powerful tool to determine the co-localization of CD24 and CD44 in the cell.

Rapid and highly sensitive detection of duplex dye-labelled DNA sequences in a PDMS microfluidic channel was investigated using confocal surface enhanced Raman spectroscopy (SERS). This method does not need either an immobilization procedure or a PCR amplification procedure, which are essential for a DNA microarray chip. Furthermore, Raman peaks of each dye-labelled DNA can be easily resolved since they are much narrower than the corresponding broad fluorescence bands. To find the potential applicability of confocal SERS for sensitive bio-detection in a microfluidic channel, the mixture of two different dye-labelled (TAMRA and Cy3) sex determining Y genes, SRY and SPGY1, was adsorbed on silver colloids in the alligator teeth-shaped PDMS microfluidic channel and its SERS signals were measured under flowing conditions. Its major SERS peaks were observable down to the concentration of 10(-11) M. In the present study, we explore the feasibility of confocal SERS for the highly sensitive detection of duplex dye-labelled DNA oligonucleotides in a PDMS microfluidic chip.

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