Biocompatible Nanostructures

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Summary   A variety of nanostructures have been developed for use in biomolecular detection. The nanosphere is the most widely used structure because of unique, highly desirable properties that make it a superior detection platform for life science research, in vitro diagnostic testing, and in vivo imaging. Other structures such as nanotips, nanorings, and nanocups have also been demonstrated for use in high resolution SERS spectroscopy and imaging. These structures provide significant field enhancement in experiments and in simulations but they have proved to be difficult to fabricate consistently. Researchers at the University of California, Berkeley have developed a new nanostructure that is biocompatible and incorporates the advantages of nanotips, nanospheres, and nanorings. Unlike present nanosphere-based SERS spectroscopy and imaging, which uses a wavelength of 500-600 nm, the new structure can be excited at near the infrared range. Excitation at longer wavelengths provides deeper penetration into tissue with minimal photothermal damage, and excitation of the nanostructure does not cause fluorescence of other biomolecules. The structure developed at Berkeley has a much stronger field emitting or "antenna" effect than previously seen even from nanotips and nanorings. The excited "hotspot" of the structure has been demonstrated to have an enhancement factor larger than 10^10. Batch fabrication is straightforward and does not require e-beam lithography. These characteristics make the improved nanostructure ideal for application in molecular medicine and in ultrasensitive Raman, biomolecular, and cellular imaging.