| The plasmonic properties of metal nanoparticles (e.g. Au nanoparticles) make them attractive as alternatives to fluorescent tags in biological detection and imaging. However, bioconjugates of metal nanoparticles are often less stable to biological media than those of fluorophores. This thesis describes a strategy to improve the stability and bioconjugate chemistry of nanoparticles by encapsulating them within a shell of photo-cross-linked block copolymer surfactants.;Photo-cross-linkable, poly(vinylbenzophenone)-containing polymers were synthesized via a one-step, Friedel-Crafts benzoylation of polystyrene-containing starting materials (including PS, PS-b-PtBA, PS-b-PEO, PS-b-PMMA and PS-b-P nBuA) using benzoyl trifluoromethanesulfonate (BzOTf) as a benzoylation reagent. Use of this mild reagent (which requires no added Lewis acid) permitted polymers with well-defined compositions and narrow molecular weight distributions to be synthesized. Micelles formed from one of these benzoylated polymers, (PS0.25-co-PVBP0.75)115- b-PAA14, were then fixed by irradiating the micelle cores with UV light. As the irradiation time was increased, the pendent benzophenone groups cross-linked with other chains in the glassy micelle cores. Dynamic light scattering, spectrofluorimetry, and Fourier transform infrared spectroscopy (FTIR) were all used to verify the progress of the cross-linking reaction.;Photo-cross-linkable block copolymer amphiphiles [polystyrene- co-poly(4-vinyl benzophenone)]-block-poly(acrylic acid) [(PS-co-PVBP)-b-PAA] and [poly(styrene)- co-poly(4-vinyl benzophenone)]-block-poly(ethylene oxide) [(PS-co-PVBP)-b-PEO] were assembled around Au nanoparticles ranging from 12 nm to 108 nm in diameter. UV irradiation cross-linked the PVBP groups on the polymer to yield particles that withstood extremes of temperature, ionic strength, and chemical etching. Streptavidin was attached to [PS-co-PVBP]-b-PAA-coated particles using the same noncovalent and covalent conjugation protocols used to bind biomolecules to divinylbenzene-cross-linked polystyrene microspheres. We expecte these particles will be useful as plasmonic, highly light-scattering and light-absorbing analogs of fluorescently labeled polystyrene nanospheres; in general, the stability and convenience of these particles makes them as everyday biotechnological tools. |
