Novel double-layered PLGA microparticles-dissolving microneedle (MPs-DMN) system for peptide drugs sustained release by transdermal delivery.

The combination of microparticles (MPs) with dissolving microneedles (DMN) represents a promising transdermal approach for the sustained release of biomacromolecule drug. In this study, we developed a double-layered microparticles-dissolving microneedle (MPs-DMN) system, which strategically concentrates PLGA MPs at the tip of the microneedle to achieve sustained release of peptide drugs through transdermal delivery. We selected exenatide (EXT) as a model peptide drug and established HPLC-UV and UPLC-MS methods for the quantitative analysis of the drug content of MPs-DMN and drug concentrations in plasma. Ultrasonication was utilized in the first step of the double emulsion solvent evaporation method to produce PLGA microparticles, achieving a high drug loading efficiency of 22.76 ± 0.64 %, surpassing the commercial products. The EXT-loaded microparticles were then mixed with 10 % w/v sucrose solution to form the first layer of the microneedle, and the mixture of the base solution was added to form the double-layered dissolving microneedle. Microscopic analysis revealed that the MPs were predominantly concentrated in the upper 50 % of the microneedle body, resulting in an impressive drug delivery efficiency of 92.86 ± 1.62 %. The MPs-DMN patch demonstrated the capability to 238.20 ± 5.79 μg of EXT within a compact area of 0.75 cm, surpassing the capacities reported in existing research. The insertion and dissolution assessments exhibited rapid dissolution, maintaining the MPs as an effective drug reservoir within the skin. Pharmacokinetic assessments indicated that the long half-life (T) of 466.4 ± 12.2 h and high relative bioavailability of 89.71 % for MPs-DMN. Furthermore, pharmacodynamic studies indicated that the MPs-DMN effectively controlled blood glucose levels below 20 mmol/L in diabetic (db/db) mouse for two weeks. These promising findings suggest that the MPs-DMN system could serve as a viable transdermal delivery method for the prolonged administration of peptide drugs.