Highly Site Specific, Protease Cleavable, Hydrophobic Peptide–Polymer Nanoparticles

Abstract

Here we present the synthesis of site specific, protease (trypsin) cleavable, hydrophobic peptide–polymer conjugate nanoparticles in inverse miniemulsion. Different peptide sequences were synthesized by microwave-assisted solid-phase synthesis and characterized by HPLC, NMR, and MALDI-TOF MS. The peptides were used to cross-link a hydrophobic functional polymer with standard peptide-coupling chemistry in inverse miniemulsion, thus generating the desired nanoparticulate morphology. By these means, well-defined nanoparticles in the size range of 200–300 nm were obtained. After transferring the particles into aqueous medium, they were characterized with photon cross-correlation spectroscopy (PCCS) and scanning electron microscopy (SEM). After removal of the solvent, the degree of cross-linking was determined by 15 N solid-state NMR. Integration of a fluorophore/quencher system, based on fluorescence resonance energy transfer (FRET) in the peptide sequences, enabled the monitoring of site specific recognition of cross-linked polymeric nanostructures by enzymes, resulting in a fluorescence recovery upon cleavage of the peptide.