The Preparation Of Antitumor Polymer-drug Conjugates With Dual Drug Synergistic Effect

The traditional chemotherapy was used to adopting mono-therapy with single agent which displays several intrinsic drawbacks in clinical practice,such as lower anticancer efficacy,side effects of dose-limited toxicity and drug resistance.To overcome these problems,the strategy of drug combination therapy was proposed.Drug combination possess the following advantages by its unique anticancer mechanism:(1)Different anticancer agents act on different biological signaling pathways in tumor cells to generate synergistic effect,thereby enhancing the anti-cancer activity;(2)using multiple drugs with different molecular targets can modulate the genetic barriers that are responsible for cancer cell mutations,thereby delaying the cancer adaptation process;(3)The synergistic effect of drug combination by acting on different signaling pathways can reduce the dose and frequency of each drug to reduce side effects and overcome drug resistance.However,combination of free drugs can't achieve the expected anticancer efficacy for the unwarrantable dose and ratio of drugs by initial injection at tumor and cell levels.Therefore,combining the advantages of nanocarrier and drug combination and using the dual drug conjugated system will not only avoid drug burst release by encapsulation system but also achieve synergistic effects.In addition,there are several difficulties in the synthesis of polymer-drug conjugates like the harsh condition for drug conjunction,the singular and non-degradable of nanocarrier and the difficult regulation of drug content.The introduction of biological orthogonal reactions into the synthesis of polymer-drug conjugates can effectively solve these problems.In this study,anionic ring-opening polymerization was carried out with functionalized L-lactide and caprolactone and polyethylene glycol monomethyl ethe,the polymer decorated by thio-bromo ‘click' chemistry,p-Nitrophenyl chloroformate(NPC)activated reaction and photoinitiated thiol-ene click reaction.Then,the carboxyl paclitaxel and doxorubicin were bonded gradually.Thus,a polymer-drug conjugates containing doxorubicin(DOX)and paclitaxel(PTX)was obtained.Then,the dual-drug conjugates were self-assembly into micelles for the measurement of CMC values and nano-dimension by fluorescence,.dynamic light scattering and transmission electron microscopy assay.The results showed that the micelles possess a good stability and suitable size.In vitro simulated drug release study showed that the dual-drug conjugates may be more stable in normal tissues while is slightly acid reliable in the microenvironment of tumor tissues for the continuous release of the two drugs.The cytotoxicity of pure copolymer and dual-drug conjugated system was tested by MTT method towards A549 and MCF-7 cancer cells which showed the polymer is non-toxic,while the dual-drug conjugated system induces a higher inhibition of tumor cell proliferation.At the same time,the synergistic effect study suggested that the combination index of the dual-drug conjugated prodrugs were less than 1 respectively,which indicated a remarkably synergistic effect.In addition,the anionic ring-opening polymerization was carried out with functionalized L-lactide and polyethylene glycol monomethyl ether,and the azide group was introduced into the pendant of the polymer by photoinitiated thiol-ene click reaction and DIC condensation reaction.The carboxyl paclitaxel is condensed with(1R,8S,9s)-Bicyclo[6.1.0]non-4-yn-9-ylmethanol,and then subjected to a strain promoted azido-alkyne cycloaddition reaction.The outcomes of FI-IR and high-performance liquid chromatography measurement showed that the reaction exhibits much higher efficiency in a very mild way.It demonstrated a successful development of a new way for drug conjunction and make a foundation for the further conjunction of dual drug by the one pot method.