(584n) Synthesis of Selectively Functionalized Large Pore Silica Materials for Protein and Small Molecule Capture

The interaction of proteins with mesoporous silica is of interest for the development of novel platforms for drug delivery, chemical synthesis, and sensing.  Recent advances in the synthesis of mesoporous silica via surfactant templating have provided access to a range of pore sizes and particle morphologies that allow for the design of tailored mesoporous structures for protein encapsulation.  A major challenge in the design of these mesoporous structures is identifying the location of the protein (surface or pore associated) in order to interpret the effect of the local environment on protein activity or stability. Another challenge is functionalizing the silica surface to provide favorable surface interactions or reduce nonspecific interactions with solutes or proteins at the silica surface. Accessibility of pore loaded proteins with small molecules also needs to be addressed with a goal of optimizing protein availability to interactions with small molecule ligands.

Amino-propyl silanes are a primary functionalization agent for silica, leading to organic-inorganic composites that can be easily chemically modified.  Although previous research groups have demonstrated the ability to surface functionalize mesoporous materials, the pore sizes of the functionalized materials were not sufficiently large for protein capture.  The silica platforms used in this experiment are synthesized via a mixed surfactant template approach, where the desired pore size (> 7 nm) is achieved through temperature tunable hydrothermal aging during synthesis.  A new, facile method for surface functionalization is demonstrated, along with the ability to capture fluorescently tagged proteins within the mesoporous structure of the particles.  The confirmation of external functionalization is performed via fluorescein isothiocyanate (FITC) tagging of the selectively functionalized amino propyl silanes, and subsequent imaging in confocal scanning laser microscopy. Pore sizes capable of protein loading are demonstrated via localization of diffused Rhodamine B (RB) tagged proteins within individual particles also using confocal scanning laser microscopy. Finally, Fluorescence Resonance Energy Transfer (FRET) between RB tagged proteins and a small molecule probe (fluorescein) is used to confirm the accessibility of pore loaded proteins within the pore.