Studies On Phenylboronic Acid-Based Bioadhesive Polymers As Carriers For Drug Delivery

Peptide and protein drugs possess biological activities that mark them aspotential therapeutics. Insulin, interferon, heparin, tissue growth factor and so onhave been the first-choice drugs in clinical application. Biological drugs have beenincluded in the national strategic emerging industries, and have broad prospects.However, due to their hydrophilic nature and high molecular weight, these drugs arepoorly absorbed across plasma membranes and only have short-term effects onmembrane transport. In this work, we are going to offer novel polymers as a carriermatrix for drug delivery systems, these carriers are designed to have small sizes,good biocampatibility and bioadhesion and can protect the peptide and protein drugsfrom degradation.1. Phenylboronic acid-containing block copolymers: synthesis, self-assembly, andapplication for intracellular delivery of proteinsBoronic acid group has been known to bind to sugars and living animal cells.Herein, a novel amphiphilic block copolymer poly(2-lactobionamidoethylmethacrylate)-block-poly(3-acrylamidophenylboronic acid)(p(LAMA-b-AAPBA))was prepared by reversible addition fragmentation chain transfer (RAFT)polymerization. Due to the interaction between lactose moieties and phenylboronicacid moieties, the copolymer could easily form nanoparticles in a spherical shape.The mean size of p(LAMA-b-AAPBA) nanoparticles was in the range of238~403nm, and the zeta potential was about-20mV. To study the feasibility ofp(LAMA-b-AAPBA) nanoparticles acting as the potential nanocarrier for proteindelivery, insulin, as a drug model, was encapsulated into the nanoparticles, theloading capacity was about11%. Moreover, the nanoparticles demonstrated asustained release of insulin, and the release behavior was due to Fickian diffusion.The cell viability assays showed that the nanoparticles had no cytotoxicity onChinese hamster ovary cells (CHO) and human colorectal carcinoma (Caco-2) cells,indicating that the carbohydrate moieties in the nanoparticles improved the low cytotoxicity of boronic acid moieties. Confocal laser scanning microscopy showedthat the nanoparticles could be taken up by Caco-2cells, indicating that thestimuli-response of phenylboronic acid to carbohydrates on the cell surfacefacilitated the nanoparticles to bind to Caco-2cells. Thus, the p(LAMA-b-AAPBA)nanoparticles can be considered as a promising carrier for proteins transport.2. Development of novel self-assembled poly(3-acrylamidophenylboronicacid)/poly(2-lactobionamidoethyl methacrylate) hybrid nanoparticles forimprovingnasal adsorption of insulinIt is well-known that the phenylboronic acid derivatives have chemicalinteractions with sugars. Hence, stable nanoparticles with core-shell structure wereformed by the covalent complexation between boronic acid groups ofpoly(3-acrylamidophenylboronic acid)(pAPBA) and hydroxyl groups ofpoly(2-lactobionamidoethyl methacrylate)(pLAMA). The image taken bytransmission electron microscopy (TEM) showed that the nanoparticles had a size ofabout200nm and dispersed in irregular spherical shape; The methyl thiazolyltetrazolium (MTT) assay suggested that the nanoparticles were non-cytotoxic on thehuman colorectal carcinoma (Caco-2) cells; Insulin, as a model protein drug, wasencapsulated into the nanoparticles. The results revealed that the insulinencapsulation efficiency was higher than11%and the nanoparticles showed acontrolled in vitro release behavior; The confocal laser scanning microscope (CLSM)images showed that the pAPBA fraction of the NPs were helpful for the binding withcell surface, resulting in the internalization of NPs into Caco-2cells; The in vivostudies demonstrated that the NPs could increase the transport of insulin through therespiratory epithelia of the rats, leading to a significant decrease of the plasmaglucose levels; The histological assessment of the nasal mucosa tissue indicated thatthe exposure of NPs did not cause cell damage on the nasal epithelia and would notdevelop lesions in the nasal epithelium. Conclusively, pAPBA/pLAMA NPs arepotential carriers for nasal delivery of peptide and protein drugs.3. Phenylboronic acid-based hrdrogel: preparation, characterization and applicationfor drug deliveryPhenylboronic acid has specific and reversible interaction with diols, polyols and sugars. In certain polymerization process, phenylboronic acid polymers cancross-link with sugars and form into hydrogel. Consequently, the p(APBA-b-LAMA)hydrogels were prepared by RAFT polymerization without cross-linking agent; TheSEM images of freeze-dried hydrogels exhibited a highly macroporous spongelikestructure; All the hydrogels swelled rapidly and reached equilibrium within10min;The insulin was loaded into the hydrogels, and in vitro studies showed that theinsulin-loaded hrdrogels could give a sustained release of insulin, and the releasebehavior was controlled by a drug diffusion process; The secondary structure ofreleased insulin was determined by CD spectra, and it has shown that the activity ofinsulin was preserved; The cell viability study showed that the hydrogels had goodcyto-compatibility on NIH3T3cells. The hydrogels are promising carriers forcontrolled release of peptide and protein drugs.In summary, we synthesized a series of amphiphilic block copolymers orhomopolymers as carrier matrix which had good biocampatibility and bioadhesion,and could protect the peptide and protein drugs from degradation and deliver theminto cells or tissues with high bioavailability. These polymers have a potentialapplication for delivery of peptide and protein drugs.