Polypeptide-grafted macroporous polyHIPE by surface-initiated N-Carboxyanhydride (NCA) polymerization as a platform for bioconjugation

A new class of functional macroporous monoliths from polymerized high internal phase emulsion (polyHIPE) with tunable surface functional groups was developed by direct polypeptide surface grafting. In the first step, amino-functional polyHIPEs were obtained by the addition of 4-vinylbenzyl or 4-vinylbenzylphthalimide to the styrenic emulsion and thermal radical polymerization. The obtained monoliths present the expected open-cell morphology and a high surface area. The incorporated amino group was successfully utilized to initiate the ring-opening polymer- ization of benzyl-L-glutamate N-carboxyanhydride (BLG NCA) and benzyloxycarbonyl-L-lysine (Lys(Z)) NCA, which resulted in a dense homogeneous coating of polypeptides throughout the internal polyHIPE surfaces as confirmed by SEM and FTIR analysis. The amount of polypeptide grafted to the polyHIPE surfaces could be modulated by varying the initial ratio of amino acid NCA to amino-functional polyHIPE. Subsequent removal of the polypeptide protecting groups yielded highly functional polyHIPE-g-poly(glutamic acid) and polyHIPE-g- poly(lysine). Both types of polypeptide-grafted monoliths responded to pH by changes in their hydrohilicity. The possibility to use the high density of function (−COOH or −NH2) for secondary reaction was demonstrated by the successful bioconjugation of enhanced green fluorescent protein (eGFP) and fluorescein isocyanate (FITC) on the polymer 3D-scaffold surface. The amount of eGFP and FITC conjugated to the polypeptide-grafted polyHIPE was significantly higher than to the amino- functional polyHIPE, signifying the advantage of polypeptide grafting to achieve highly functional polyHIPEs

Polypeptide core-shell silica nanoparticles with high grafting density by N-carboxyanhydride (NCA) ring opening polymerization as responsive materials and for bioconjugation

Silica nanoparticles were furnished with a functional polypeptide shell to create a pH-responsive inorganic-organic hybrid material. Free amine groups present on silica nanoparticles initiated the N-carboxyanhydride (NCA) polymerization of particular amino acid NCAs directly onto the inorganic support, offering a convenient method to functionalize silica core nanoparticles with a uniformly dense polypeptide shell. Poly(gamma-benzyl-L-glutamate) (PBLG), poly(epsilon-carbobenzyoxy-L-lysine) (PZLL), and S-tert-butyl protected polycysteine (PtBLC) were grafted from the silica core both independently as homopolypeptides and simultaneously to form a copolypeptide shell, highlighting the versatility that the grafting mechanism possesses. The grafting of PBLG was investigated in detail at 0 degrees C and 20 degrees C to determine any differences in the size and uniformity of the polypeptide shell formed. Dynamic light scattering (DLS) analysis revealed a correlation between the thickness of the uniform organic shell and the amount of amino acid in the monomer feed, with higher linearity at the lower polymerization temperature. Size Exclusion Chromatography (SEC) analyses of degrafted PBLG confirmed the DLS results. A high grafting density of around 0.4 PBLG chains per nm(2) was calculated highlighting the control afforded in this approach to polypeptide grafting. Subsequent deprotection of the PBLG homopolypeptide shell afforded pH-sensitive poly(glutamic acid) (PGA) coupled silica nanoparticles. The selective release of a model rhodamine B dye was demonstrated to emphasize the potential that these hybrid nanomaterials have for the on-demand release of payload molecules in response to a targeted pH trigger. Moreover, covalent bioconjugation was successfully shown by attachment of green fluorescent protei