Evaluation of geometrical effects of microneedles on skin penetration by CT scan and finite element analysis

Abstract

Computerized tomography (CT scan) imaging and finite element analysis were employed to investigate how the geometric composition of microneedles affects their mechanical strength and penetration characteristics. Simulations of microneedle arrays, comprising triangular, square and hexagonal microneedle base, revealed a linear dependence of the mechanical strength to the number of vertices in the polygon base. A laser-enabled, micromoulding technique was then used to fabricate 3x3 microneedle arrays, each individual microneedle having triangular, square or hexagonal base geometries. Their penetration characteristics into ex-vivo porcine skin, were investigated for the first time by CT scan imaging. This revealed greater penetration depths for the triangular and square-based microneedles, demonstrating CT scan as a powerful and reliable technique for studying microneedle skin penetration.

Current trends in polymer microneedle for transdermal drug delivery

“…The material used in MN fabrication is the most important factor in design, as it determines the mechanical strength and drug release properties of the MN. Other factors that need to be considered include the density of the material, height of the microneedle, and diameter width of the tip and base of the microneedle ( Loizidou et al, 2016 ). Microneedles are arrays of cone- or pyramid-shaped structures formed with different materials, generally ranging from 250 to 2000 mm in height could cross the human skin barrier to deliver targeted drug molecules ( Tomono, 2019 ).…”

“…The microchannel dimensions created by MN can be estimated by histology examination ( Sivaraman & Banga, 2017 ). However, the sample preparation for histological examination may alter skin structure during the freezing and sectioning steps that lead to inaccurate assessment of the microneedle penetration into the skin ( Loizidou et al, 2016 , Nguyen et al, 2018 ). Thus, a real-time non-invasive method optical coherence tomography (OCT) can be used for skin characterization ( Donnelly et al, 2010 ).…”

A review on microfabrication of thermoplastic polymer‐based microneedle arrays

“…These results can be seen as a general guideline for the pattern design of an array . Furthermore, it was shown by Loizidou et al that finite‐element simulation together with computerized tomography scans could be used for estimating geometrical effects of microneedles on skin penetration. A greater penetration depth could be achieved with triangular and square‐based microneedles.…”

<p>Finite Element Analysis for Predicting Skin Pharmacokinetics of Nano Transdermal Drug Delivery System Based on the Multilayer Geometry Model</p>

“…Mapped mesh is used for numeralization of the multilayers of the drug transport system with the thickness of the vehicle, SC, viable epidermis, and dermis at 0.1 cm, 0.02 cm, 0.02 cm, and 0.16 cm, respectively. 31 , 32 The element grids were divided and optimized using the grid division tool provided by PDE tool software in Matlab 12.0. The initial drug concentration in the simulation was 0.2 g/cm 3 , and that in the skin was 0 g/cm 3 .…”