Injection molding for manufacturing of solid poly( l -lactide-co-glycolide) microneedles

A solid microneedle array can be used for “poke and flow” transdermal delivery of a drug, which involves the infusion or diffusion of a drug through pores in the skin that were created by the microneedle array. In this paper, solid microneedle arrays were created out of the polymer RESOMER LG 855 S—poly( l -lactide-co-glycolide) using injection molding. Scanning electron microscopy revealed that the microneedle in the injection-molded four-by-one microneedle array closely matched the dimensions that were used for injection molding. X-ray photoelectron spectroscopy revealed that the carbon bonding in the microneedle material matched that expected for poly( l -lactide-co-glycolide). The reduced elastic modulus of the microneedle material, 6.04 ± 0.17 GPa, was noted to be appropriate for skin penetration applications. The microneedle array was used for the delivery of the model drug methyl blue to surgically discarded human underarm skin. These results suggest that injection molding of RESOMER LG 855 S—poly( l -lactide-co-glycolide) may be an appropriate approach for large-scale manufacturing of solid microneedles. Graphic Abstract