Glucose-sensitive Polyphosphoester-based Polymer Nanoparticles For Insulin Delivery System

Diabetes has become a major problem that threatens human health globally.Currently,the most effective way to treat diabetes is to supplement exogenous insulin,but this still faces many difficulties.Therefore,it is urgent to develop a glucose-responsive insulin delivery system(GRIDS),which is mainly divided into three types:glucose oxidase,concanavalin A and phenylboronic acid(PBA).Compared to the first two,PBA has better performance and has attracted more attention in recent years.The GRIDS based on PBA mainly includes micelles,vesicles,nanogels and hybrid nanoparticles,etc.Among them,micelles that are easy to prepare and nanogels that have stable cross-linked structures(including core-crosslinked nanoparticles,abbreviated as CCL NPs,and shell-crosslinked nanoparticles,abbreviated as SCL NPs)have attracted wide attention.With biocompatible and biodegradable polyphosphoesters(PPEs)and polycaprolactone(PCL)as polymer carriers,this paper designs three kinds of NPs,including PBA-based NPs,CCL NPs and SCL NPs for insulin delivery system.The specific contents are as follows:1.Glucose-sensitive polyphosphoester block copolymer nanoparticles for insulin delivery systemIn the first part of this thesis,glucose-sensitive polyphosphoester block copolymer,abbreviated as(PBYP-g-MPBA)-b-PEEP,was prepared by ring-opening polymerization(ROP),"click" chemistry and amide reaction,where the PBYP and PEEP respectively represent two kinds of polyphosphoesters,and MPB A represents 3-mercaptopropionic acid modified with 3-aminophenylboronic acid(APBA).The successful synthesis of products was verified by nuclear magnetic resonance(NMR)spectroscopy,gel permeation chromatography(GPC)analysis,fourier transform infrared(FT-IR)spectroscopy and UV-vis measurement.The amphiphilic copolymer(PBYP-g-MPBA)-b-PEEP can self-assemble into core-shell NPs in aqueous solutions.The average particle size and morphology of the NPs were measured by dynamic light scattering(DLS)and transmission electron microscopy(TEM),respectively.The NPs swelled at different glucose concentrations.Fluorescein isothiocyanate(FITC)-insulin was loaded into the NPs and triggered to release in the presence of glucose.Methyl thiazolyl tetrazolium(MTT)assays and hemolysis tests proved that the(PBYP-g-MPBA)-b-PEEP copolymer had good biocompatibility.2.Glucose-sensitive core-crosslinked polyphosphoester block copolymer nanoparticles for insulin delivery systemIn the second part,a block copolymer based on polyphosphoester was prepared by ROP and Cu(I)-catalyzed azide-alkyne cycloaddition(CuAAC)reaction,abbreviated as(PBYP-g-Glu)-b-PEEP,where PBYP and PEEP represent two kinds of polyphosphoesters,and Glu represents the 2-azidoethym-?-D-gducopyranoside(Glu-N3)modified to the side groups of the copolymer.The crosslinking agent benzene diboronic acid(AAPBA)was prepared by amide reaction.The successful synthesis of products was verified by NMR,GPC analysis,FT-IR spectroscopy and UV-vis measurement.The amphiphilic polymer(PBYP-g-Glu)-b-PEEP can self-assemble into core-shell uncore-crosslinked nanoparticles(UCCL NPs)in aqueous solutions,and form CCL NPs after the addition of crosslinking agent(AAPBA).DLS and TEM were used to study the self-assembly behavior of two kinds of NPs and the effect of different contents of Glu groups on the size of two kinds of NPs,further to verify the stability and glucose-sensitivity of CCL NPs.The ability of NPs to load FITC-insulin and their glucose-triggered release behavior were detected by fluorescence spectrophotometer.The results of MTT tests and hemolysis activity experiments showed that the polymer(PBYP-g-Glu)-b-PEEP had good biocompatibility.3.Glucose-sensitive shell-crosslinked polyphosphoester and polycaprolactone polymer nanoparticles for insulin delivery systemIn the third part,a polymer based on polyphosphoester and polycaprolactone(abbreviated as(PEAEP-g-Glu)-g-PCL)was prepared by ROP,substitution reaction,Michael addition and "CuAAC" reaction,wherein PEAEP represents hydrophilic polyphosphoester,PCL represents hydrophobic polycaprolactone and Glu represents Glu-N3.NMR,GPC analysis and FT-IR spectroscopy were used to verify the successful synthesis of products and to characterize the molecular weights and molecular weight distributions.The amphiphilic polymer(PEAEP-g-Glu)-g-PCL can self-assemble into core-shell unshell-crosslinked nanoparticles(USCL NPs)in aqueous solutions,and form SCL NPs after adding AAPB A.The self-assembly behavior of the two kinds of NPs was studied by DLS and TEM,and the stability and glucose-sensitive behavior of SCL NPs were further studied by DLS.Fluorescence spectrophotometer was used to detect the ability of NPs to load FITC-insulin and their glucose-triggered release.The result that the polymer had good biocompatibility was verified by MTT tests and hemolysis activity tests.