There is a strong interest in the simultaneous detection of a number of different proteins in a single biological sample. Limitations on the size of the collected sample require that these measurements be done on as small a volume of fluid as possible. This interest has been one of the driving forces behind the development of microfluidic devices for biomedical applications. The move to these smaller-scale systems has a number of advantages. First, they are capable of analyzing smaller sample volumes. Second, in applications such as capillary electrophoresis the microfluidic system can achieve the same separation resolution in much less time than a larger-scale system. Finally, the reduced size of the analysis setup raises the possibility of developing portable analytical devices.? ? One device under development is capable of measuring eight different electrophoretic runs simultaneously, while another device, a multi-channel flow immunoassay, is intended to measure up to twenty different analytes in a single sample. This latter device holds great potential for monitoring the immune or hormonal status of new born infants or measuring different cellular pathways within a single patient sample. Other interests of our group include the design and development of devices capable of analyzing the secretions and physiology of single cells. Our facilities have now developed to a point where we are able to advise and collaborate with investigators on how to produce microfluidic devices that address their specific needs.? ? In collaboration with scientists at NIST, LBPS has developed a microfluidic device for immunoassay that can simultaneously isolate and detect multiple proteins, and which can ultimately be used for a variety of clinical and research applications. Using the microfabrication facilities at NIST, we are able to make micrometer-scale glass-encapsulated microfluidic systems with any desired two-dimensional configuration. The channel device architecture has several advantages over existing array technology; for example, proteins are detected by single-point capture, and much smaller sample volumes can be used. ? ? In a second collaboration with NIST, LBPS developed an eight channel plastic device for electrophoretic separation of DNA fragments. Currently, our focus is to further develop this chip for proteomic applications. One important challenge, key to the successful implementation of these devices, is the ability to achieve real-time detection of fluorescent labels at high sensitivity. We have achieved 10pM, 10 Hz label detection in eight independent 50u channels in a plastic substrate using a novel ball-lens, fiber optic approach that couples to an imaging spectrograph with CCD detection that allows four labeling dyes to be used simultaneously.
