Coating Formulations for Microneedles |
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Authors: | Harvinder S Gill Mark R Prausnitz |
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Institution: | (1) Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Georgia Institute of Technology, 313 Ferst Drive, Atlanta, Georgia 30332-0535, USA;(2) School of Chemical & Biomolecular Engineering Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia 30332-0100, USA |
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Abstract: | Purpose To develop a rational basis for designing coating solution formulations for uniform and thick coatings on microneedles and
to identify coating strategies to form composite coatings, deliver liquid formulations, and control the mass deposited on
microneedles.
Materials and Methods Microneedles were fabricated using laser-cutting and then dip-coated using different aqueous, organic solvent-based or molten
liquid formulations. The mass of riboflavin (vitamin B2) coated onto microneedles was determined as a function of coating and microneedle parameters. Coated microneedles were also
inserted into porcine cadaver skin to assess delivery efficacy.
Results Sharp-tipped microneedles, including pocketed microneedles, were fabricated. Excipients that reduced coating solution surface
tension improved coating uniformity, while excipients that increased solution viscosity improved coating thickness. Evaluation
of more than 20 different coating formulations using FDA approved excipients showed that hydrophilic and hydrophobic molecules
could be uniformly coated onto microneedles. Model proteins were also uniformly coated on microneedles using the formulations
identified in the study. Pocketed microneedles were selectively filled with solid or liquid formulations to deliver difficult-to-coat
substances, and composite drug layers were formed for different release profiles. The mass of riboflavin coated onto microneedles
increased with its concentration in the coating solution and the number of coating dips and microneedles in the array. Coatings
rapidly dissolved in the skin without wiping off on the skin surface.
Conclusions Microneedles and coating formulations can be designed to have a range of different properties to address different drug delivery
scenarios. |
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Keywords: | coating formulations dip-coating method microfabricated microneedles protein coatings transdermal drug delivery |
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