Preparation And Evaluation Of Paeoniflorin Loaded Hydrogels For Articular Cavity Administration

Rheumatoid arthritis（RA）is a common chronic disease.The Non-steroidal anti-inflammatory drugs is the commonly used drug in clinic,however long-term oral administration can cause serious side effects.Intra-articular injection can deliver the drug directly to the local joint by which to enhances the therapeutic efficacy while minimizing systemic side effects.Unfortunately,drugs injected into joints directly are often cleared very rapidly,which severely limits the feasibility of this approach.Injectable hydrogel can form sustained-release medicine depot at desired region,while maintaining a high local concentration over an extended period,and then improve the life quality of patients.Paeoniflorin（Pae）is the main active ingredient of traditional chinese medicine Paeonia tacti lora Pall.,with anti-inflammatory,analgesic and immunomodulatory effects.Pae therapy has shown definite effect on RA,however,oral administration suffers from low bioavailability.In this project,paeoniflorin loaded hydrogel for Intra-articular injection was prepared,and The anti-arthritis effect was evaluated by in vitro experiments and in vivo experiments in adjuvant-induced arthritis（AA）rats model.Objective:To choose the optimal hydrogel materials,develop paeoniflorin loaded hydrogels,and evaluate their quality and therapeutic effect on AA model.Methods:1 The hydrogels were prepared by mixing poly（aspartate）（PAA）solution with aldehyde-based polyethylene glycol（PEG-DA）of different molecular weight.The relationship between structure and properties of hydrogels and molecular weight of crosslinking agent was studied by Scanning electron microscopy（SEM）and rheological analysis,and the self-healing property.Doxorubicin（DOX）was used as a model drug to study the drug release properties of hydrogels with different molecular weight crosslinking agents in vitro;the MTT method was used to study the cytocompatibility of hydrogels.Finally,the molecular weight of crosslinking agent suitable for late drug-loaded hydrogels was selected.2 The paeoniflorin hydrogel was prepared and the gelation time was determined by tube invertion test;the drug release characteristic of paeoniflorin hydrogel in vitro was studied by micro-solution method;the in vitro degradation of paeoniflorin hydrogel was studied by visual observation.3 The rat AA model was prepared by injecting of complete Freund’s adjuvant into the knee of rat;the degree of knee lesions in rats were evaluated by joint index scoring;and the levels of TNF-α,IL-1,IL-6 and PGE₂ in serum of rats were determined by enzyme-linked immunosorbent assay（ELISA）.Results:1 SEM showed that the hydrogel showed a homogeneous interconnected porous structure.Rheological results showed that the PAA hydrogels prepared by PEG-DA method had high spatial stability and good flexibility.The hydrogels were able to re-infusion together after in vitro incision,indicating a self-healing property.The results of in vitro drug release showed that the DOX hydrogels formed by crosslinking of PEG-DA with different molecular weight showed sustained release in PBS buffer,with the best sustained release property of PEG₂₂₇-DA.In vitro cytotoxicity results showed that the concentration of hydrogel extract at 10μg·m L^-1-100μg·m L^-1 had no obvious toxicity to the growth of He La and JB6 P+cells.2 The gelation time of paeoniflorin hydrogel in vitro was 180 min;the drug released continually in vitro for 168 h;the paeoniflorin hydrogel was completely degraded in vitro for 9 days.3 Pharmacodynamic studies showed that,compared with day 0,the arthritis index of paeoniflorin hydrogel group decreased significantly on day21（P<0.01）;compared with the model group,on the day 21,the paeoniflorin hydrogel group had significantly lower arthritis index（P<0.01）.Compared with the model group,paeoniflorin hydrogel significantly reduced the levels of TNF-α（P<0.01）,IL-1（P<0.05）,IL-6（P<0.05）and PGE₂（P<0.05）in AA rats.Conclusions:The best performance of hydrogel was obtained through experimental analysis.The paeoniflorin hydrogels with PEG₂₂₇-DA and PAA had drug sustained release and biodegradable properties,and had obvious anti-inflammatory effect on AA rats,which could effectively relieve arthritis in AA rats,and had a good application prospect.