Polymeric Microneedles Integrated with Metformin-Loaded and PDA/LA-Coated Hollow Mesoporous SiO2 for NIR-Triggered Transdermal Delivery on Diabetic Rats

Herein, an NIR-responsive polymeric microneedle (MN) system incorporated with metformin-loaded and polydopamine/lauric-acid-coated (PDA/LA-coated) hollow mesoporous SiO2 has been developed for transdermal delivery of antidiabetic drug (metformin). First, an antidiabetic drug was loaded within hollow mesoporous SiO2 nanoparticles (HMSNs) by a diffusion method. Then, PDA as photothermal conversion agent and lauric acid (LA) as phase change material (PCM) were coated onto the HMSN to form NIR-responsive drug nanocarriers. Finally, these metformin-loaded and PDA/LA-coated HMSNs were encapsulated into poly(vinylpyrrolidone) (PVP) MNs. After insertion into skin tissue, LA could melt with the photothermal conversion of PDA under NIR light, thus enabling release of encapsulated metformin from MNs. The in vivo release behavior of metformin from MNs into skin was further studied to investigate its hypoglycemic effect on diabetic rats. Compared with the subcutaneous injection of metformin, the bioavailability of MN–NIR groups was 95.8 ± 2.7%. The antidiabetic drug can be precisely released by adjustment of exposure time and power densities of NIR light