Field ready: Development of a rapid LAMP-based colorimetric assay for the causal agent of white pine blister rust, Cronartium ribicola

Objectives: Ascorbic acid has many benefits to the skin. Numerous attempts to promote its topical delivery show great challenges since its chemical instability and poor skin impermeability. Microneedle delivery is a simple, safe, painless and effective means to deliver therapeutic or nourishing molecules into the skin. The purpose of this study was twofold: (a) to develop a new formulation of ascorbic acid-loaded microneedles to enhance ascorbic acid stability by investigating an optimal amount of polyethyleneimine as an additive to the dextran- based microneedle formulation and (b) to assess microneedle properties in terms of dissolving rate, skin penetration ability, biocompatibility and antimicrobial activity. Methods: The microneedles formulated with ascorbic acid and varied polyethyleneimine concentrations were fabricated and subsequently tested for ascorbic acid stability using 2,2- diphenyl- 1-picrylhydrazyl assay. The dissolution rate and skin penetration depth were investigated in porcine skin and the reconstructed human full-thickness skin model respectively. The skin irritation tests were done according to the Organisation for Economic Co-operation and Development