Synthesis of a biodegradable tadpole-shaped polymer via the coupling reaction of polylactide onto mono(6-(2-aminoethyl)amino-6-deoxy)-β-cyclodextrin and its properties as the new carrier of protein delivery system

A new tadpole-shaped polymer was synthesized via the coupling reaction of poly(dl-lactide) (PLA) onto mono(6-(2-aminoethyl)amino-6-deoxy)-β-cyclodextrin (CDen) using N,N′-Dicyclohexycarbodiimide as the catalyst. The structures of CDenPLA as the products were characterized with infrared spectrometry, nuclear magnetic resonance and their molecular weights were determined by gel permeation chromatography. The tadpole-shaped polymer possessed both a hydrophilic head that could bind some residues on a protein and a hydrophobic polylactide tail so that it could be amphiphilic. Two methods, double emulsion (DE) and nanoprecipitation (NP), were employed to fabricate the polymeric nanoparticles into which the bovine serum albumin was loaded as a model protein. The nanoparticles with a hydrophobic core of the PLA segments covered with the hydrophilic corona layer of the cyclodextrin moiety could be formed from the copolymers using NP method as identified by 1HNMR. Influence of the preparation conditions on the nanoparticles size, encapsulation efficiency and release profile in vitro was investigated. The encapsulation efficiency of the BSA-loaded nanoparticles with the average diameter of 377 nm was 71.6% under an optimized condition. The structure maintenance in the nanoparticle preparation and release in vitro was also measured via sodium dodecyl sulfate polyacrylamide gel electrophoresis and circular dichroism spectrometry. The results showed that the new copolymer could load BSA effectively and BSA kept stable after it was released from the nanoparticles.