Effect of extraction methods on silk fibroin microneedles for drug delivery application

Silk fibroin (SF) extracted from Bombyx mori cocoons was used for developing microneedles using the micromolding technique. Extractions of SF from Bombyx mori were carried out using two methods: (1) lithium bromide and (2) Ajisawa's reagent with 30 min and 60 min of degumming time. SF obtained using Ajisawa's reagent undergoes slower sol to gel transition compared to the LiBr method. SF was characterized using Fourier Transform IR analysis and the molecular weight of the SF was found using sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Microneedles were developed using all the four types of SFs through the micromoulding technique and properties were evaluated and compared. The morphology of the microneedles was evaluated using stereomicroscopy and SEM. The mechanical strength of the microneedles was evaluated using a Universal Testing Machine and Texture Analyzer and it was found that SF‐LiBr‐30 and SF‐CaCl 2 ‐30 have higher mechanical strength as the longer degumming time will lower the mechanical strength of the microneedles. Insertion ability, swelling behaviour and in vitro degradation studies indicate that SF‐CaCl 2 ‐30 microneedles exhibit enhanced performance in all three aspects, which can be linked to their lower crystalline β‐sheet content. Cytotoxicity analysis was done on all four types of microneedles and they were found to be non‐toxic to L929 cells. This research article compares the properties of microneedles developed using the four distinct SFs. It was found that SF‐CaCl 2 ‐30 has good mechanical strength, insertion ability, stability, high degradation rate and swelling ability, and also, due to its slower sol to gel transition, it gives a prolonged handling time, making it more suitable and convenient than other SF solutions towards the fabrication of microneedles. Hence it is a promising choice for both diagnostic and drug delivery applications.