Characterization of Polymeric Microneedle Arrays for Transdermal Drug Delivery

Abstract

Microfabrication of dissolvable, swellable, and biodegradable polymeric microneedle arrays (MNs) were extensively investigated based in a nano sensitive fabrication style known as micromilling that is then combined with conventional micromolding technique. The aim of this study was to describe the polymer selection, and optimize formulation compounding parameters for various polymeric MNs. Inverse replication of micromilled master MNs reproduced with polydimethylsiloxane (PDMS), where solid out of plane polymeric MNs were subsequently assembled, and physicochemically characterized. Dissolvable, swellable, and biodegradable MNs were constructed to depth of less than 1 mm with an aspect ratio of 3.6, and 1/2 mm of both inter needle tip and base spacing. Micromolding step also enabled to replicate the MNs very precisely and accurate. Polymeric microneedles (MN) precision was ranging from ±0.18 to ±1.82% for microneedle height, ±0.45 to ±1.42% for base diameter, and ±0.22 to ±0.95% for interbase spacing. Although dissolvable sodium alginate MN showed less physical robustness than biodegradable polylactic-co-glycolic acid MN, their thermogravimetric analysis is of promise for constructing these polymeric types of matrix devices.

Microneedle characterisation: the need for universal acceptance criteria and GMP specifications when moving towards commercialisation

“…Axial compression tests involve subjecting the MNs to a force perpendicular to the base-plate [26]. They typically involve the use of a mechanical test station which records both displacement and force while the MNs are pushed against a hard metallic surface at a defined rate [41,42,43], Figure 3A.…”

“…Transverse fracture force tests are therefore necessary to provide a more complete profile of the behaviour of MNs during application [42,43]. A mechanical test station is commonly used, where a transverse force (force applied parallel to the MN base-plate and normal to the microneedle y-axis) is applied at a defined point of the MN via a metal probe until the MN fractures.…”

“…Analysis of the force-displacement curves will identify the fracture force. A sudden drop in force indicates MN failure [26,43]. Transverse fracture force testing of a row of MNs in an array, rather than a single MN, involves dividing the force required to fracture all the MNs within the row by the number of MNs, to calculate the transverse fracture force per individual MN [26].…”

Hydrogel Microneedle Arrays for Transdermal Drug Delivery

“…Biodegradable polymeric polylactic-co-glycolic acid (PLGA) MNs and dissolvable MNs, for instance, sodium alginate MNs are proved to create micro-holes in the skin layers without breaking, although the former one have more resistance and mechanical stability [49,50].…”

“…They developed adhesive patches, containing the molecules at defined loadings, were then attached to the upper base plates of hydrogel-forming MN, with the novel composite system termed as "integrated MN". However, according to the experimental details, for example, the delivery of insulin from the MN (with 600 μm height, 300 μm width at base, 50 Fig. 2 The design of PVP MN microneedles.…”