Structural characterisation and transdermal delivery studies on sugar microneedles: Experimental and finite element modelling analyses

• The mechanical and drug delivery properties of sugar microneedles were investigated.
• Buckling predicted to be the main mode of microneedle failure.
• Critical load factor and microneedle skin penetration correlated to Young’s modulus.
• Chemical properties, in addition to mechanical, are important for skin delivery.
• CMC/maltose microneedles are superior to CMC/trehalose and CMC/sucrose.

Dissolving microneedles are especially attractive for transdermal drug delivery as they are associated with improved patient compliance and safety. Furthermore, microneedles made of sugars offer the added benefit of biomolecule stabilisation making them ideal candidates for delivering biological agents such as proteins, peptides and nucleic acids. In this study, we performed experimental and finite element analyses to study the mechanical properties of sugar microneedles and evaluate the effect of sugar composition on microneedle ability to penetrate and deliver drug to the skin. Results showed that microneedles made of carboxymethylcellulose/maltose are superior to those made of carboxymethylcellulose/trehalose and carboxymethylcellulose/sucrose in terms of mechanical strength and the ability to deliver drug. Buckling was predicted to be the main mode of microneedle failure and the order of buckling was positively correlated to the Young’s modulus values of the sugar constituents of each microneedle.

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