Rapidly Detachable Microneedles Using Porous Water-Soluble Layer for Ocular Drug Delivery

Detachable microneedle (MN) technology is highly desired for treatment of ocular diseases such as keratitis or glaucoma because of its minimally invasiveness and sustained drug delivery. However, shortening of administration time during insertion into target tissues still remains an important issue, although various approaches using mechanical and chemical separation mechanisms have been attempted. Here, a rapidly detachable microneedle pen (RD-MNP) containing a porous dissolvable sacrificial layer is fabricated for instant separation of the tip. The porous sacrificial layer is fabricated between a drug-loaded tip and a base by freeze drying. The sacrificial layer is comprised of water soluble polymers: poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP). Porous structure can accelerate dissolution rate compared to solid structure due to its capillary effect that relies on pore size and distribution. The pore size and distribution of the sacrificial layer are controlled and detachment of an RD-MNP with the optimum pore structures is immediate upon dipping the MNP in PBS. Furthermore, the insertion characteristics of the system are investigated using the gelatin phantom and porcine eye sclera. With the optimized sacrificial layer, a MN tip is almost immediately detached and embedded to the porcine sclera with the aid of impact insertion.