Preparation and in vitro-in vivo evaluation of temperature-sensitive sinomenine hydrochloride reservoir microneedles.

Objective: This paper focuses on the manufacturing technique of bubble microneedles and temperature-sensitive materials in order to design and prepare a temperature-sensitive reservoir microneedle. The objective is to evaluate the feasibility of addressing the issue of low drug load in traditional Chinese medicine (TCM) external preparations using microneedles. Methods: The study involved the utilization of sinomenine hydrochloride as the model drug. The drug, along with the temperature-sensitive material N-isopropylacrylamide, was filled into the cavity of the bubble microneedle made from chitosan. Through positioning and curing processes, a temperature-sensitive sinomenine hydrochloride reservoir microneedle was prepared. The microneedle consisted of a needle body, a positioning layer, a basal layer, and a drug reservoir. The drug load, size, length, mechanical properties, and puncture ability of the prepared reservoir microneedle were measured to characterize and evaluate its drug load and mechanical properties. In addition, the in vitro release characteristics of the microneedles were determined using Franz diffusion cells, while the in vivo release characteristics were evaluated using the percutaneous microdialysis technique. Results: The research result demonstrated that the prepared temperature-sensitive reservoir microneedle had a drug load of approximately 5.76 mg/cm2. The exposed needle tip had a conical shape with a height of around 650 μm, exhibiting good mechanical strength and skin puncture ability. The in vitro release tests showed that the microneedle could simulate the temperature of the skin and release the drug in a controlled and gradual manner, displaying characteristics of diffusion and dissolution of the skeleton. Furthermore, compared to conventional external preparations, the reservoir microneedles significantly enhanced transdermal permeation of the drug in the in vivo percutaneous studies. Conclusion: The study demonstrated that reservoir-type microneedles prepared using temperature-sensitive materials and bubble microneedle preparation techniques could significantly increase the drug load of microneedles, providing the advantage of microinvasion. [ABSTRACT FROM AUTHOR]