As a new transdermal drug delivery technology, bubble microneedle could achieve painless and precise drug delivery, which has attracted great attention from researchers. In order to improve the utilization rate of the drug carried by microneedle, we proposed a method for preparing a tip-loaded bubble-soluble microneedle. During the molding process of the microneedle, air bubbles were formed in the needle body, and the drug was concentrated on the needle tip. The preparation process of the bubble microneedle was optimized. The effects of foaming agent concentration, drying temperature, and solution viscosity on the forming of bubble microneedles were explored. Furthermore, the transdermal effect of the product was analyzed. The experimental results showed that the bubble microneedle forming process was stable, with the forming rate above 90% and the forming cycle shortened to about 4 h. The drug was mainly concentrated on the tip of the microneedle, with a length of 180 μm, and the length of the bubble was 250 μm. Moreover, the microneedle array can create microchannels on the mouse skin, and the needle bodies can be rapidly dissolved within 5 min. The bubble microneedle could rapidly release about 48% of the drug within 1 min and about 91% of the drug within 5 min. The bubble microstructure of the microneedle array hindered the diffusion of the drug to the substrate, which improves the utilization rate of the drug. This study provides a technical basis for the practical application of microneedle for transdermal drug delivery.
Keywords: bubble microneedle; cutting-edge drug loading; process optimization; transdermal effect; two-step pouring method.