Fabrication of a Ti porous microneedle array by metal injection molding for transdermal drug delivery

Abstract

Microneedle arrays (MA) have been extensively investigated in recent decades for transdermal drug delivery due to their pain-free delivery, minimal skin trauma, and reduced risk of infection. However, porous MA received relatively less attention due to their complex fabrication process and ease of fracturing. Here, we present a titanium porous microneedle array (TPMA) fabricated by modified metal injection molding (MIM) technology. The sintering process is simple and suitable for mass production. TPMA was sintered at a sintering temperature of 1250°C for 2 h. The porosity of TPMA was approximately 30.1% and its average pore diameter was about 1.3 μm. The elements distributed on the surface of TPMA were only Ti and O, which may guarantee the biocompatibility of TPMA. TPMA could easily penetrate the skin of a human forearm without fracture. TPMA could diffuse dry Rhodamine B stored in micropores into rabbit skin. The cumulative permeated flux of calcein across TPMA with punctured skin was 27 times greater than that across intact skin. Thus, TPMA can continually and efficiently deliver a liquid drug through open micropores in skin.

Touch-actuated microneedle array patch for closed-loop transdermal drug delivery

“…The drug concentration can be easily adjusted. In this study, the porosity of the medical sponge loaded with insulin solution was approximately 95%, in accordance to the density method measurements (Li et al., 2017a ). The volume of the sponge in our TMAP was 194 mm 3 .…”

“…These MAs have key features, yet they also have some limitations, which prevent their market spreading. The porous MA suffers from insufficient mechanical strength, resulting in a risk of breakage in the skin (Li et al., 2017a ). The solid MA has a relatively high mechanical strength but is limited by its ‘poke with patch’ two-step delivery process, which leads to practical issues for patients (Wang et al., 2016 ).…”

Engineering Microneedles for Therapy and Diagnosis: A Survey

“…The materials mostly determine the methods for MN fabrication. Metallic MNs are usually fabricated by laser cutting, laser ablation, wet etching, metal electroplating, and micromolding [22,30]. Silicon MNs are commonly developed using wet etching, dry etching, and three-dimensional laser cutting [71,72].…”

“…The preliminary study on MNs started in 1976, but it was not extensively exploited until the late 1990s because of advancements in microfabrication technology, which provided suitable tools for MNs manufacture. Up to now, MNs have been developed with various materials (e.g., silicon, glass, ceramic, metal, polymers, and carbohydrate) [22][23][24]. Besides, the customized structure design enables MNs to be suitable for specific applications.…”

Microfabricated Drug Delivery Devices: Design, Fabrication, and Applications

“…It can be used alone or be bonded to silicon using anodic bonding or silicone rubbers to form complex systems with different microstructures (e.g., microfluidic chips) for controlled drug delivery. [50,51] Other rigid materials such as metals, [52][53][54] ceramics, [55,56] silicon nitride, [57,58] and polycrystalline silicon [59,60] have also been used in developing various drug delivery devices. [48,49] In addition, functionalization of the porous materials with molecular, supramolecular, or polymer moieties enable fabrication of new devices with great versatility in controlled drug delivery utilizations including sustained release, targeted release, and stimuli-responsive release.…”