Ho Yee Poon, Siu Ming Kwan and King Lun Yeung
Department of Chemical and Biomolecular Engineering, 2Division of Environment, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, HKSAR;
The most common routes for drug delivery are oral administration, hypodermic injection and transdermal delivery. Transdermal delivery allows steady administration of drugs for hours and thus avoids the blood level spikes and troughs produced by other routes. Different innovative strategies, including iontophoresis, phonophoresis, skin ablation using chemicals, laser or radiofrequency and microneedle, have been developed to breach the barrier of stratum corneum for effective drug delivery. Microneedle offers a simple, painless and less invasive way for transdermal drug delivery that can be inexpensively manufactured and implemented. Unlike hypodermic injection, transdermal delivery with microneedle produces less dangerous medical wastes and poses a smaller risk for disease transmission.
We demonstrate for the first time the use of porous zeolite as microneedle material for transdermal drug delivery. The studies include the fabrication, characterization of zeolite microneedle array and its transdermal delivery test for insulin, NSAID and influenza vaccine in rodents (i.e. rats and mice animal models). Pure silica zeolite which is porous, chemically inert and biocompatible, was hydrothermally grown on polymer template, followed by template removal at high temperature to create an array of free standing hollow zeolite microneedles. The needle lumen and length were designed for efficient drug delivery, while maintaining good mechanical strength for skin insertion. The hydrothermal growth conditions were adjusted to obtain zeolite microneedles with different inter- and intra-crystalline pore size for comparable strength to metal microneedles and controlled drug delivery. The zeolite microneedles did not cause observable skin irritation or allergic responses during their use in the animal study. The in vitro and in vivo test results showed the blood glucose level of diabetic rats was well controlled by transdermally delivered insulin through zeolite microneedles and the remarkably increased IgG level appeared in the blood serum of mice after transdermal influenza vaccination using zeolite microneedles. Transdermal delivery with zeolite microneedle has been proved as an invasive, safe and effective drug delivery route. The attempts are being made for its long-term therapeutic application.
Keywords: Microporous microneedles, passive transdermal delivery, insulin, NSAID, influenza vaccine.