A Stereolithography-Based Modified Spin-Casting Method for Faster Laboratory-Scale Production of Dexamethasone-Containing Dissolving Microneedle Arrays.

Microneedle arrays (MNAs) consist of a few dozens of submillimeter needles, which tend to penetrate through the stratum corneum layer of the skin and deliver hardly penetrating drugs to the systemic circulation. The application of this smart dosage form shows several advantages, such as simple use and negligible pain caused by needle punctures compared to conventional subcutaneous injections. Dissolving MNAs (DMNAs) represent a promising form of cutaneous drug delivery due to their high drug content, biocompatibility, and ease of use. Although different technologies are suitable to produce microneedle arrays (e.g., micromilling, chemical etching, laser ablation etc.), many of these are expensive or hardly accessible. Following the exponential growth of the 3D-printing industry in the last decade, high-resolution desktop printers became accessible for researchers to easily and cost-effectively design and produce microstructures, including MNAs. In this work, a low force stereolithography (LFS) 3D-printer was used to develop the dimensionally correct MNA masters for the spin-casting method. The present study aimed to develop and characterize drug-loaded DMNAs using a two-level, full factorial design for three factors focusing on the optimization of DMNA production and adequate drug content. For the preparation of DMNAs, carboxymethylcellulose and trehalose were used in certain amounts as matrices for dexamethasone sodium phosphate (DEX). Investigation of the produced DexDMNAs included mechanical analysis via texture analyzer and optical microscopy, determination of drug content and distribution with HPLC and Raman microscopy, dissolution studies via HPLC, and ex vivo qualitative permeation studies by Raman mapping. It can be concluded that a DEX-containing, mechanically stable, biodegradable DexDMNA system was successfully developed in two dosage strengths, of which both efficiently delivered the drug to the lower layers (dermis) of human skin. Moreover, the ex vivo skin penetration results support that the application of DMNAs for cutaneous drug delivery can be more effective than that of a conventional dermal gel.