Construction And Properties Of Drug Carriers Based On Oleanolic Acid

Oleanolic acid（OA）is an antitumor natural product of pentacyclic triterpenoids,widely found in Oleaceae plants such as Ligustrum lucidum,Olea europaea and Forsythia suspensa.OA has many pharmacological activities such as antitumor,hepatoprotective and anti-inflammatory,which have attracted great attention of researchers.However,OA also has limitations such as poor water solubility,severe side effects and poor stability,which restrict its efficacy and clinical application.In order to overcome the drawbacks existing in OA,and realize the safe and efficient drug delivery,in this work,a series of OA based drug carriers including nano drug carriers and macroscopic drug carrier hydrogel,with good solubility in water,biological compatibility and efficient antitumor properties,were designed and prepared using natural polymers of cellulose derivatives andα-cyclodextrin（α-CD）,through physical and chemical modification methods,such as the reaction of functional group,reversible addition fragmentation chain transfer radical polymerization（RAFT）and ring opening polymerization（ROP）.In this study,the physicochemical properties and antitumor properties of drug carriers were also studied.The main research contents and conclusions of this work are as follows:1.In order to improve the water solubility of OA,polymeric nano-drug carriers based on water-soluble single-arm polyethylene glycol（m PEG）coupled with OA were prepared,and the physicochemical properties and antitumor properties were studied.The m PEG-OA polymer was prepared by coupling OA with m PEG,and then another natural anticancer drug,10-hydroxycamptothecin（HCPT）,was wrapped by self-assembly to form m PEG-OA/HCPT NPs.The results showed that the nanoparticles significantly increased the water solubility（1.03 mg/m L）of OA,which was 572 times higher than that of OA.The nanoparticles had appropriate particle size（164.18±40.12 nm）and well drug loading capacity（OA:6.18±1.20 wt%,HCPT:14.12±0.73 wt%）.The cell cytotoxicity in B16 cells of nanoparticles was 18.3 times higher than that of OA,and the antitumor activity of nanoparticles was also stronger than that of HCPT.The survival rate of tumor-bearing mice with B16 cells was 82.7%on the 20th day of the experiments.2.Preparation of nano-drug carriers based on OA block polymers with high drug loading capacity and controllable structure,and study on the physicochemical properties and antitumor properties.The hydrophilic block polymer was formed by RAFT reaction with oligo（ethylene glycol）methyl ether methacrylate（OEGMA）as the monomer,and then the amphiphilic POEGMA-b-POAMA block copolymers were prepared by free radical polymerization of OA prodrug monomer.Then HCPT was wrapped in OA block copolymers by self-assembly to form POEGMA-b-POAMA/HCPT NPs with high drug loading capacity.The number-average molecular weight（M_n）and polydispersity index（PDI）of the prepared POEGMA-b-POAMA block polymers were 15230 g/mol and 1.19,respectively.The nanoparticles had suitable particle size（164.23±4.21 nm）and high drug loading capacity（OA:17.35%±0.21 wt%,HCPT:28.33±0.67 wt%）,when the mass ratio of block polymer to HCPT was 20:10.The cell cytotoxicity in 4T1 cells and MCF-7 cells of nanoparticles was respectively 39.1 times and 22.0 times of OA.In addition,the nanoparticles showed high antitumor activity,and the survival rate of tumor-bearing mice with 4T1 cells was 64.2%on the 12th day of the experiments.3.In order to improve the biocompatibility of nano-drug carriers,polymeric nano-drug carriers based on carboxymethyl cellulose（CMC）coupled with OA were synthesized,and the physicochemical properties and antitumor properties were studied.The CMC-OA polymer was prepared by coupling OA with CMC,and then HCPT was wrapped by self-assembly to form CMC-OA/HCPT NPs.The results showed that the nanoparticles had a small particle size（78.58±8.74 nm）and high drug loading capacity（OA:20.89±2.96 wt%,HCPT:15.43±0.81 wt%）.The cell cytotoxicity in B16 cells of nanoparticles was 19.5 times higher than that of OA.At the same time,the nanoparticles showed good antitumor effects,and the survival rate of tumor-bearing mice with B16 cells was 84.6%on the 20th day of the experiments.4.Preparation of grafted copolymer nano-drug carriers based on carboxylated cellulose nanocrystals（CCNs）and study on the physicochemical properties and antitumor properties.A series of CC-g-PLLA grafted polymers were synthesized by grafting poly（L-lactide）to CCNs using ROP reaction.Then OA was wrapped in grafted polymers by self-assembly to form CC-g-PLLA/OA NPs.The grafted polymer with DS_PLLAof 2.03 was prepared when the mass ratio of CCNs to L-lactide was 1:9.The nanoparticles formed by the grafted polymer had suitable particle size（196.82±9.14 nm）,high drug loading capacity（OA:24.76±0.58 wt%）and good stability.The survival rate of tumor-bearing mice with 4T1 cells was45.6%on the 12th day of the experiments.5.In order to improve drug concentration at tumor sites,injectable and targetedα-CD based supramolecular hydrogel drug carriers were synthesized,and the physicochemical properties and antitumor properties were studied.Eight-arm polyethylene glycol（8PEG）was coupled with OA to form OA-8PEG polymer,and then folic acid（FA）was connected to form OA-8PEG-FA.HCPT was wrapped by self-assembly to form the nanoparticles.α-CD based supramolecular hydrogels were formed by the host-guest interaction betweenα-CD and nanoparticles.The results showed that hydrogels had a porous structure and thinning shear force,which was beneficial to sustained release and injectable drug delivery.The cell cytotoxicity in 4T1 cells and MCF-7 cells of nanoparticles was respectively 29.7 times and 23.6times of OA.Hydrogels could effectively inhibit tumor growth,and the survival rate of tumor-bearing mice with 4T1 cells was 67.7%on the 12th day of the experiments.A variety of drug carriers based on OA were designed and constructed in this work to achieve safe and efficient delivery of OA,which improved the antitumor treatment effect of OA and provided a theoretical basis for the development and utilization of natural product antitumor drugs.