PH-Hesponsive Microneedle Patch For The Treatment Of Acute Gouty Arthritis

Objective:In this study,we propose to integrate microneedle patch technology with pH-responsive drug delivery system to prepare MN patches with good biocompatibility,rapid dissolution and pH-responsiveness,and characterise them in a series of ways;and then use them in the treatment of acute gouty arthritis（AGA）to assess anti-inflammatory efficacy by macroscopic gross observation,swelling degree measurement,H&E staining and ELISA analysis,in order to provide clinical treatment of gouty arthritis.Methods:（1）Preparation and characterisation of hollow calcium carbonate（CaCO₃）microspheres and curcumin-loaded hollow calcium carbonate（Cur@CaCO₃）microspheres:CaCO₃microspheres were prepared by the template method and Cur@CaCO₃was prepared by immersion adsorption,and then their morphology was characterised using transmission electron microscopy（TEM）,while their chemical composition was tested using Fourier transform infrared spectroscopy（FTIR）and ultraviolet spectroscopy（UV）.The loading rates and the slow release behaviour in PBS buffers of different pH values were also determined.（2）Preparation and characterisation of pH-responsive microneedle patches（Cur@CaCO₃-MN）:Cur@CaCO₃-MN was prepared using a split vacuum casting method,and its morphology was characterised using a body microscope and scanning electron microscope（SEM）,its mechanical properties were tested using a universal testing machine,and its tip dissolution properties were determined using isolated pig skin,and the in vitro biocompatibility of the material used was tested using the MTT method.（3）Construction of an acute gouty arthritis（AGA）model and evaluation of the efficacy of the pH-responsive Cur@CaCO₃-MN patch:The AGA model was constructed by grinding MSU crystals,preparing MSU crystal suspension（25 mg/m L）with sterile 0.9%sodium chloride solution,and injecting 10μL of MSU suspension vertically along the lateral posterior aspect of the right ankle joint of rats using a 1 m L syringe with a No.3 needle.The experiment was divided into 7 groups:normal group（Normal,saline,10 m L/kg）,negative control group（Negative,modelling,no treatment）,positive control group（Colchicine,modelling,colchicine gavage treatment,0.3 mg/kg）,blank microneedle patch group（HA-MN,modelling,HA-MN transdermal administration）,calcium carbonate microneedle patch group（CaCO₃-MN,modelling,CaCO₃-MN transdermal administration）,curcumin microneedle patch group（Cur-MN,modelling,Cur-MN transdermal administration）,and pH-responsive microneedle patch group（Cur@CaCO₃-MN,modelling,Cur@CaCO₃-MN transdermal administration）.The treatment was started 12 h after modelling.The Colchicine group was administered at a frequency of once daily for 3 days;the latter 3groups were treated with the corresponding microneedle patches,twice daily for 3days.After the treatment was completed,the rats were executed and the serum of each group was taken for analysis of IL-1β,IL-6,TNF-αand ICAM-1 inflammatory factors.The heart,liver,spleen,lungs and kidneys of the rats in both groups were analyzed for in vivo biocompatibility.The right ankle joint of the rats was taken for H&E staining.The degree of swelling of the joint was recorded before modelling,and 3,6,12,36,60 and 84 h after modelling.Results:（1）Preparation and characterization of CaCO₃and Cur@CaCO₃:CaCO₃and Cur@CaCO₃were successfully prepared with a diameter of about 1000 nm,and the resulting CaCO₃microspheres were structurally intact,well dispersed and had a large specific surface area.The drug loading and encapsulation rates were 13.94%and64.98%.Cur@CaCO3 is pH-sensitive,the cumulative release rate of Cur@CaCO₃was 56.78%at pH=7.5 in PBS and 89.28%at pH=5.5 in PBS.（2）Preparation and characterisation of pH-responsive microneedle patches（Cur@CaCO₃-MN）:SEM morphological characterisation showed that the 11×11conical microneedle arrays were uniformly arranged on a flat substrate.The MN tip height was approximately 515.33±11.33μm,The diameter of the MN substrate is approximately 217.67±6.37μm,the spacing between adjacent MN tips was approximately 458.73±1.31μm and the spacing between adjacent MN substrates was approximately 239.04±7.79μm.Cur@CaCO₃-MN was able to achieve the mechanical strength required to penetrate the stratum corneum.Needle tip dissolution performance tests show that MN has good dissolution properties,reaching 89%of the total height in 5 min.It also has good biocompatibility.（3）Construction of an acute gouty joint（AGA）model and evaluation of the efficacy of pH-responsive microneedle patch（Cur@CaCO₃-MN）:the trend graph of the change in joint swelling shows that compared to the Negative group,the Cur@CaCO₃-MN group showed the same therapeutic effect as the clinical Colchicine group,with joint swelling returning to the Normal group.The Cur@CaCO₃-MN group showed better results than the Cur-MN group.H&E staining and ELISA analysis of the joints in each group also confirmed these results.Conclusions:The results of this study show that the use of a pH-responsive drug delivery system combined with MN patch technology can deliver drugs subcutaneously in a painless,minimally invasive and efficient way,avoiding the negative effects of inflammation,infection and bleeding caused by traditional injection methods,increasing the concentration of effective local drugs and saving drug administration costs,providing a new idea for the clinical treatment of acute gouty arthritis.