Nanomedicine Design and Characterization of Biointerfaces
Practical applications that are expected to emerge from nanobiotechnology and nanomedicine research often include biointerfaces, i.e., biomolecules that are appropriately interfaced with synthetic or inorganic nanostructures or surfaces. Biointerfaces are also important for utilizing the intrinsic recognition properties of biomolecules to guide assembly and self-assembly of nanostructures. Elucidating the interactions between solid surfaces and biomolecules, such as DNA, peptides, or proteins, is the first critical step toward designing biointerfaces. A novel approach to the analysis of nanobio systems has been validated in preliminary studies of DNA and peptides on surfaces and involves designing model systems with systematically increasing chemical, physical, and structural complexity. In particular, model biomolecules of uniform composition, i.e., comprising repeated monomers or sequences, are amendable for spectroscopic analyses and provide the basic information for rational design of the subsequent model and realistic systems with more compositional and structural complexity.
Intimately connected to the design of biointerfaces are the development and validation of the appropriate analytical methods for quantitative analysis of the functional and nanostructured surfaces and materials. The current trend in the development of analytical instrumentation is to enable multiple techniques to be applied to the same sample serially or even in parallel. For example, a combined ellipsometry and quartz crystal microbalance (QCM) setup potentially allows one to follow the adsorption of biomolecules on surfaces and the association of solvent and solution counterions with the molecules. In another example, an advanced x-ray photoelectron spectroscopy (XPS) system can produce spectra from spots that are 20 to 900 microns in size, spectral images over areas of several mm across, and provides complementary ultraviolet photoelectron spectroscopy (UPS) and reflection electron energy loss spectroscopy (REELS) characterization. Because of the intrinsically limited information that can be obtained from any individual method, such advanced instrumentation is opening new analytical opportunities relevant for nanotechnology and nanobiotechnology. Practical application of these new analytical methods, however, continually provides challenges in terms of developing appropriate sample preparation protocols, instrument calibration methods, and reference materials for validation of complementary in situ and ex situ measurements.