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

Abstract

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.

Biodegradable silicon nanoneedles for ocular drug delivery

“…Furthermore, the degradation rate of Si NNs substantially decreased down to ~0.05 nm day −1 (purple line) through the conformal passivation of a thin (i.e., 3-nm-thick) pinhole-free layer, such as aluminum oxide (Al 2 O 3 ), across the surface (i.e., porosity = 30%) using an atomic layer deposition (ALD) ( 27 ). For instance, the Al 2 O 3 -passivated Si NNs exhibited at least five orders of magnitude prolonged degradation in tear fluid as compared to typical biodegradable composites, such as PLGA and MeHA (i.e., 24 to 120 μm day −1 ), that have been widely used for ocular drug delivery ( 8 , 28 ). The corresponding SEM images of Si NNs while being degraded at a prescribed time interval are shown in fig.…”

Recent Advances in Microneedle Platforms for Transdermal Drug Delivery Technologies

“…As shown by confocal images, the macromolecules developed tissue depots which resulted in a persistent permeation [ 122 ]. Detachable microneedle technology is highly attractive for the treatment of eye disorders such as keratitis or glaucoma due to its reduced invasiveness and consistent drug delivery [ 123 ]. Shortening the administration time during microneedle insertion into target tissues, remains an important issue, although different methods have been attempted using mechanical and chemical separation mechanisms.…”

“…In addition, gelatin phantom and porcine eye sclera were used to study the insertion properties of the system. A microneedle tip is almost instantly removed and embedded into the porcine sclera with the optimized sacrificial layer with the aid of impact insertion [ 123 ]. Enhanced targeting of drug delivery to the posterior region of the eye is critical for the treatment of several post-segment eye conditions.…”

Smart Microneedles for Therapy and Diagnosis

“…For more efficient skin interstitial fluid extraction and cargo loading, polymer microneedles with highly porous and interconnected microstructures have been generated. To fabricate porous microneedles, various approaches have been adopted, such as adding pore-forming agents to the prepolymers [ 60 , 61 ] and changing the structure of the polymer chain [ 62 ]. In a recent study, Kim et al used a “water annealing” method to modulate the polymorphism of their silk fibroin microneedles [ 63 ].…”