Bioanalytical microsystems are miniaturized biochemical and molecular biological assays that rely on highly specific binding of biological molecules such as antibodies, receptors and nucleic acids to an analyte of interest. Taking advantage of their small feature sizes, miniaturized analytical systems provide for small sample volume, highly parallel processes and thus good multi-analyte detection capabilities. It is a well-established research field with many systems described in literature based on various detection and recognition principles. Remaining key challenges are the integration with sample preparation and sample concentration steps. The ability to identify an analyte in a complex mixture of compounds is challenging for any detection system and needs to rely in part on the biorecognition molecule's ability to specifically bind and or react with its analyte. However, fouling of microchannels and the need for automated separation of the analyte out of its matrix renders it even more complicated for microsystems.
Electrospinning is a fiber formation process that relies on electrical rather than mechanical forces to form nano and microscale (100 nm to 10 microns) fibers. The fibers can be electrospun directly onto a conductive surface such as copper and gold. It is proposed to investigate the possibility to incorporate electrospun nanofibers for sample purification and analyte concentration within polymethyl methacrylate microfluidic channels. First, nanofibers will be spun within the channel, across the channel and along the channel length providing 3D structures with high surface to volume ratios within a polymer microchannel. Solvent bonding of the nanofibers to the channel surfaces will be studied and the strength of their attachment will be measured. Conductive nanofibers containing carbon nanotubes will be spun and investigated for amperometric and electrochemiluminescence reactions. Second, biorecognition elements will be included into the nanofibers (conductive and non-conductive) prior to the spinning process using streptavidin and DNA probes as models. These functional bionanofibers will be characterized physically using a variety of spectroscopy and microscopy techniques as well as tensile testing techniques to confirm successful incorporation of biological molecules, effect of this incorporation on fiber morphology and mechanical properties and to determine the location of the biological molecules within the fibers. The nanofibers will be characterized with respect to their biological recognition ability using liposome hybridization and binding assays developed previously in our labs. Third, these functional fibers bonded in microchannels will be studied as bioseparators; as electrodes; 3D guiding lines and concentrators and will be combined with nanofibers with negative and positive surface charges, with hydrophobic, hydrophilic surfaces.
The scientific merit of the proposal lies in the study of the integration of nanofibers with polymer-based microfluidic channels and their use as biofunctional nanofibers. Short term goals include the study of electrospinning conditions on the stability of streptavidin and DNA probes, their effective presentation on the surface of the nanofibers and usefulness as bioseparators and concentrators. Long term goals will broaden the technology to other protein and nucleic acid molecules, will result in an understanding of biorecognition molecule activities in embedded situations. It is postulated that protein molecules would be more stable when encapsulated in fibers than when in solution or surface-immobilized. Finally, complex 3D bioseparators and concentrators can be designed based on these initial findings.
The broader impact of the proposed research will be its direct applicability to on-site and lab-based diagnostic tests for clinical, food, environmental and biosecurity applications. Two graduate and at least four undergraduate students involved in the research will obtain cross-disciplinary training in fiber science, biology and nanotechnology engineering. High school students from the Cornell New Visions program will participate in research throughout the academic year, seniors from Onondaga Tribe high schools will be recruited for summer internships. A high school teacher and additional undergraduate students will be incorporated into the program via Cornell Center for Materials Research programs.
