Photo-cross-linked Polypeptide Nanoparticles via ROPISA Methodology

Abstract

Photo-crosslinked polymer nano-assemblies have gained significant importance in biomedical field in drug delivery, and tissue engineering, etc. This thesis work is aimed to make new classes of photo-crosslinkable polypeptides in aqueous medium via polymerization-induced self-assembly process. For this purpose, cinnamoyl functional group was conjugated into l-serine, an amino acid bio-resource, and new N-carboxylic anhydride (NCA) monomer was synthesized. The solvent route polymerization using PEG- amine as an initiator and NHC as catalyst via ring opening polymerization (ROP) confirmed the potential of the serine monomer to form polymers in controlled and efficient manner. The ring opening polymerization induced self-assembly (ROPISA) was employed taking PEG-amine as the hydrophilic initiator, to make stable emulsion of PEG-polypeptide di-block copolymer nano assemblies. ROPISA of serine-NCA monomer at M/I = 10 or 25 provided stable polymer emulsions in the form of opalescent solutions. The monomodal, narrow dispersed GPC profile and close agreement between the molecular weight of the amphiphilic di-block copolymers and the anticipated molecular weight of the copolymers indicate controlled polymerization. The size of the nano assemblies in these polypeptide emulsions range between 25 and 30 nm and had a spherical nanoparticle morphology. The photocuring ability of this opalescent solution was examined using UV light of wavelength 265nm. Upon shining the light, the cinnamoyl group underwent [2+2] cyclo addition which was confirmed by UV spectroscopy. The DLS studies revealed that the properties of the nanoparticle produced via ROPISA is intact after curing. Crosslinked and non-crosslinked nanoparticle loading efficiency were studied using dyes like Nile Red and Rhodamine B.