Preparation Of Polycarbonate-based Stimuli-responsive Nanoparticles And Their Application In Cancer Therapy

With the increasing number of new cancer cases and deaths in recent decades,cancer is a major cause of death worldwide and has been the focus of public health.Numerous researches have tried to study and develop new therapeutic methods for cancer treatment.At current,cell therapies,anti tumor vaccines,and new biotechnological drugs have shown some good results in preclinical experiments.Although a great achievement was made,traditional chemotherapy is still considered to be an effective and extensive treatment.However,the majority of anticancer drugs can't recognize normal cells and tumors,which usually leads to low drug efficacy and side effects.The use of stimuli-responsive nanoparticles as drug carriers is an alternative but still has a great challenge.In this paper,the amphiphilic block polymer was obtained and modified with various functional small molecules.The resulting polycarbonate-based polymer self-assembled into micelle nanoparticles,loading the cargos and could be triggered to release drugs under a specific stimulus.The content of studied projects and conclusions are briefly listed as follows:(1)PEG-b-poly(MPC-Azo/DEA)with light and p H dual-sensitive was facilely prepared for the first time by azide-alkyne click chemistry between amphiphilic block copolymer bearing pendant alkynyl group poly(ethylene glycol)-poly(5-methyl-5-propargylxycarbonyl-1,3-dioxane-2-one)(PEG-b-poly(MPC))and azobenzene derivative(Azo-N₃)as well as 2-azido-1-ethyl-diethylamine(DEA-N₃).The light response of the polymeric nanoparticles benefits from the azobenzene segments,and p H responsiveness is attributed to DEA moieties.The prepared copolymer could self-assemble into spherical micelle particles.The morphological changes of these particles in response to dual stimuli were investiga ted by UV/Vis spectroscopy,dynamic light scattering(DLS),and transmission electron microscopy(TEM).Nile Red(NR)was utilized as a probe,and fluorescence spectroscopy served as a piece of evidence for the enhanced release of cargos from polymeric nanoparticles under combined stimulation.The hydrophobic anticancer drug,DOX was loaded into the nanoparticles and the loaded-DOX could be released from these nanoparticles under dual stimuli.MTT assays further demonstrated that PEG-b-poly(MPC)and PEG-b-poly(MPC-Azo/DEA)were of biocompatibility and low toxicit y against Hep G2cells as well as SMCC-7721 cells.More importantly,the prepared DOX-loaded nanoparticles exhibited a good anticancer ability for Hep G2 cells and SMCC-7721cells.The synthesized light and p H dual-sensitive biodegradable polymeric nanoparticles had the potential to be platforms for precisely controlled release of encapsulated molecules.(2)A novel redox-responsive core crosslinked micelles(CCLMs)was developed via a simple one-step click chemistry reaction.CCLMs were prepared by the click reaction between poly(ethylene glycol)-b-poly(5-methyl-5-propargylxycarbonyl-1,3-dioxane-2-one)(PEG-b-poly(MPC))amphiphilic block copolymer and bis-(azidoethyl)disulfide.The CCLMs not only presented excellent stability under physiological conditions but also could realize controlled release of DOX in reduction circumstance(such as DTT,GSH).Furthermore,DOX-loaded CCLMs showed high cytotoxicity in Hela cells and 4T1 cells by MTT assays.They enhanced the cytotoxicity against drug-resistant ADR/MCF-7 cells in vitro.Confocal laser scanning microscope(CLSM)images exhibited that the DOX-loaded materials were easily taken up by Hela cells,free DOX as control.With facile preparation,superior stability,controlled release property,the redox-responsive CCLMs can provide a versatile platform for drug delivery and have great potential for antitumor therapy.(3)Polycarbonate-based core-crosslinked redox-responsive nanoparticles(CC-RRNs)were constructed via a simple and efficient strategy,which could efficiently regulate the drug loading content and redox-responsive drug release.A series of CC-RRNs for delivery of anticancer drugs DOX were synthesized by click reaction between alkyne-containing amphiphilic block copolymer PEG-b-poly(MPC)and azide-terminated molecules with different ratios of?-lipoic acid derivative(LA-N₃)to 6-bromohexanoic acid derivative(AHE-N₃),followed by introduction of crosslinked networks under catalytic amount of dithiothreitol(DTT).Dynamic light scattering(DLS)experiments exhibited that the CC-RRNs presented more excellent stability over no-crosslinked unresponsive nanoparticles(NC-URNs)under physiological conditions.Interestingly,the DOX loading content of nanoparticles(NPs)increased as the proportion of LA moieties rose,and the value of DOX loading content was up to 20.0±0.6%,close to the theoretical value of 23.1%.In vitro redox-responsive release of DOX and MTT assays confirmed that the ratio of LA-to-AHE of PMPC-based polymers not only determined the ultimate drug release of DOX-loaded CC-RRNs in the reductive environment but also dominated the cytotoxicity towards Hep G2 cells.Confocal laser scanning microscope(CLMS)and flow cytometry further proved the enhancement of cellular uptake and tumor accumulation.This facile strategy overcomes the tedious fabrication of drug nanocarriers,offers an opportunity for regulating the functionality of NPs,and thus paves the pathway for scale-up production of biodegradable drug carriers with biocompatibility,stabi lity,and targetability.