| The secondary structure of a protein is highly influential in dictating its function. Similarly, amphiphilic block copolypeptides, which are formed from the same amino acid building blocks as proteins, can utilize these same structural motifs to form unique self-assembled materials. In my research, I have studied how disrupting the hydrophobic segment secondary structure via racemization influences our amphiphilic block copolypeptides to allow formation of both nanoscale double emulsions and micelles. These amphiphilic block copolypeptides are synthesized using transition metal mediated ring opening polymerization of alpha-amino acid N-carboxyanhydrides (NCAs). Amphiphilic block copolypeptide surfactants containing an alpha-helical hydrophobic segment are shown to form nanoscale single oil in water (OW) emulsions. However, when the hydrophobic portion is racemized, nanoscale water in oil in water (WOW) double emulsion droplets formed. The double emulsion stabilization is highly general, capable of forming with a variety of chain lengths, compositions, concentrations, and oil volume fractions. Moreover, the double emulsions are shown to be able to incorporate both hydrophilic and hydrophobic cargos into the same double emulsion droplet. Further studies indicate that the double emulsions are stable when mixed with small molecule surfactants, other block copolypeptide surfactants and when incubated in solutions with high ionic strength and varying pH values. Intial results from some in vitro studies indicate that surface charge is critical in reducing the cytoxicity of the double emulsion droplets. In another area, we investigate how racemizing the hydrophobic oligoleucine of a nonionic block copolypeptide could facilitate the self-assembly into micelles. The nanoscale size of both the double emulsions and micelles make them ideal candidates for future drug delivery applications. |
