Cationic Poly(amide-imide) Prodrug:Synthesis,Self-assembly And Application In Drug Delivery

Objective:Both Camptothecin(CPT)and Doxorubicin(DOX)are hydrophobic small molecule anticancer drugs.Small molecule drug are usually conjugated to polymer carriers to form polymer prodrug systems,which can effectively relieve the systemic toxicity of small molecule drugs and prolong their blood circulation time.This is very important for the development of the field of biomedicine.Poly(amide-imide)(PAI)is a class of advanced engineering materials with excellent thermal,electrical,and mechanical properties.PAI has been seldomly used in biomedical applications due to poor aqueous solubility.In this study,for the first time,water-soluble PEGylated PAI was used as the polymer backbone to conjugate CPT to construct a PAI-based polymer drug delivery system.Methods:PAI with thiol side chain was prepared through the step-growth polymerization(aminolysis of a thiolactone and amine-maleimide Michael addition).The in-situ generated thiols on lateral chains of a PAI occurred a thiol-disulfide exchange reaction with a pyridinedisulfide-modified CPT(CPT-DSSP)drug precursor to generate PAI-CPT polymer prodrugs.Three PAI-CPT polymer prodrugs with different drug loading rates were prepared by changing initial PEG500/CPT-DSSP feed ratios.Hydrodynamic diameter,zeta potential,and critical aggregation concentration(CAC)of polymer prodrug nanoparticles(PDNPs)were measured through a dynamic light scattering particle size analyzer.The cumulative release amount of CPT in vitro was measured by fluorescence method to evaluate the reduction-responsive release characteristics of PAI-CPT PDNPs.The cellular uptake behavior of P1-P3 PDNPs was characterized by live cell imaging system and flow cytometry.CCK-8 colorimetric method was adopted to determine the in vitro killing effect of P1-P3 PDNPs on different tumor cell lines(HeLa cells,4T1 cells and HT-1080 cells).DOX was further encapsulated into PAI-CPT PDNPs by a ultrasonic method to construct a dual-drug-loaded nanomedicine,and to conduct in vitro drug release and anticancer efficacy studies.Results:The pyridinedisulfide-modified CPT(CPT-DSSP)drug precursor was successfully synthesized.Three PAI-CPT prodrugs were prepared and named P1,P2 and P3,respectively.The 1H and 13C nuclear magnetic resonance(NMR)and gel permeation chromatography(GPC)results confirmed their chemical structures.Drug loading rates of CPT were 7.5 mol%,13.4 mol%,and 22.7 mol%,respectively.Transmission electron microscope(TEM)images show that three PAI-CPT prodrugs could self-assemble into spherical nanoparticles with average sizes of 23.8±5.3 nm,25.2±6.9 nm,and 27.4±7.5 nm,respectively.Reduction-responsive drug release experiments confirmed that in the presence of 10 mM GSH,the cumulative release of CPT after 48 h was,88.3%,88.6%,and 93.3%,respectively.Live cell imaging and flow cytometry analysis confirmed the cellular uptake of P1-P3 PDNPs by Hela cells.After 2 hs incubation,the average fluorescence intensity of P1-P3 PDNPs entering Hela cells increased significantly,and the fluorescence intensity further increased with a longer incubation time(4 hours and 8 h).In vitro cytotoxicity experiments showed that at higher CPT concentrations(>10 ?g/mL),P1-P3 PDNPs had better anticancer efficacies than free CPT.Moreover,P1-P3 PDNPs(P1-P3/DOX PDNPs)dual-drug-loading system achieved an obvious combined treatment effect.Conclusions:In this project,a cationic poly(amide-imide)nanoprodrug was successfully synthesized.The self-assembly behavior of PAI prodrugs was studied,and a PAI-based prodrug delivery system was constructed for cancer chemotherapy.The experimental results showed that PAI polymer nanoprodrugs self-assembled into various nanostructures in water,and presented a reduction-reactive drug release profile.Meanwhile,P1-P3 PDNPs can also be used as drug carriers to load other hydrophobic drugs for combined chemotherapy.The efficacy of monotherapy was improved,and the biomedical application of PAIs is significantly expanded.