Effects of dexamethasone PLGA magnetic microspheres on chronic pain in inflammatory rats

JIN Xin; ZHENG Jichun; SUN Yonghai

doi:10.3969/j.issn.2097-1753.2023.05.010

Abstract：Objective To prepare dexamethasone polylactic-co-glycolic acid(PLGA)magnetic microspheres and evaluate their therapeutic efficacy against chronic pain in inflammatory rats.Methods Dexamethasone PLGA magnetic microspheres were prepared using the emulsion-solvent evaporation method.Chronic pain models in rats were established by injecting complete Freund's adjuvant into the plantar surface of the left hind paw.Therapeutic efficacy was assessed in 36 model rats,which were randomly divided into six groups according to treatments:the positive control,magnetotherapy,dexamethasone PLGA magnetic microspheres,dexamethasone sodium phosphate injection,dexamethasone PLGA magnetic microspheres plus magnetotherapy,and dexamethasone sodium phosphate injection plus magnetotherapy,with six rats per group.The appearance of the rat's left hind paw skin and the mechanical pain threshold were observed from day 2 to day 10 post-modeling.On the 10th day,the left hind paw skin was pathologically examined under anesthesia using hematoxylin and eosin staining.Results After treatment,all groups except the positive control and magnetotherapy groups showed significant improvement in the mechanical pain threshold of the left hind paw between days 4 and 6 post-treatment,particularly in the microspheres plus magnetotherapy group.Inter-group comparisons revealed no significant difference in the mechanical pain threshold between the microspheres plus magnetotherapy group and the injection plus magnetotherapy group during the first two days post-administration.However,from day 4 to day 10,the microspheres plus magnetotherapy group showed significantly higher thresholds compared to the other groups.Except for the magnetotherapy group,all the other groups showed a significant reduction in inflammatory cells compared to the positive control group on day 10 post-administration,espeically in the dexamethasone PLGA magnetic microspheres group and the microspheres plus magnetotherapy group.Conclusion Dexamethasone PLGA magnetic microspheres exhibit sustained-release properties and good biocompatibility,which can significantly alleviate chronic pain caused by chronic inflammation.