The skin is an effective barrier against the invasion of noxious chemicals and harmful pathogens. The rigidity of the outermost layer of skin, stratum corneum, hinders the transdermal delivery of drugs especially those with large molecular weight and low lipophilicity. A pathway across the skin barrier is needed for drug delivery. Microneedles primarily made of silicon, metals or polymers can be used to breach the skin barrier and facilitate transdermal drug administration.

This study explores zeolite, microporous aluminosilicate structure, as a material for microneedle. A back-side exposure technique for forming the SU-8 into template needle structure was developed for fabrication of various zeolite microneedle shapes including cylindrical, hollow and tapered structure. Fa...[ Read more ]

The skin is an effective barrier against the invasion of noxious chemicals and harmful pathogens. The rigidity of the outermost layer of skin, stratum corneum, hinders the transdermal delivery of drugs especially those with large molecular weight and low lipophilicity. A pathway across the skin barrier is needed for drug delivery. Microneedles primarily made of silicon, metals or polymers can be used to breach the skin barrier and facilitate transdermal drug administration.

This study explores zeolite, microporous aluminosilicate structure, as a material for microneedle. A back-side exposure technique for forming the SU-8 into template needle structure was developed for fabrication of various zeolite microneedle shapes including cylindrical, hollow and tapered structure. Fabrication parameters for controlling the length and shape of zeolite microneedles were investigated. The mechanical properties of the fabricated zeolite microneedles were measured and analyzed. The axial fracture force, shear fracture force and insertion force for excised porcine skin model were obtained. The relationship of the zeolite microneedle geometry to its axial fracture force was determined, and a safety factor of 3.2 to 4.3 were obtained for zeolite microneedles for skin insertion due to the sharp edge of zeolite crystals on the tip. Finally, in vivo transdermal drug delivery by zeolite microneedles was illustrated for influenza vaccination of mice model. The serum IgG level of mice by conventional vaccination and vaccination by zeolite microneedles were found to be comparable indicating successful vaccination by microneedles.