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Sericin removal from silk (degumming) affects material characteristics of silk fibroin (SF). Sodium carbonate is most commonly used for degumming, but numerous alternative methods are available. Herein, a systematic comparison of degumming methods is provided. Sodium carbonate, sodium oleate, trypsin, and ionic liquid are used, and materials are characterized regarding mass loss, SF content, molecular integrity of SF, refractive index, and tensile properties. Complete degumming is achieved within 30 min of using sodium carbonate, but results in significant reduction of molecular weight, shift toward less acidic charge variants, and reduction of yield‐ and rupture force. Sodium oleate and trypsin are inefficient and negatively affect tensile properties, while ionic liquid shows good efficiency and marginal degradation of SF but also reduced yield‐ and rupture force. Refractive index is not affected by degumming. These results allow rational selection of the degumming method and tuning of SF properties for biomedical applications.

Tissue engineering Controlled releaseSiRNA DNA a b s t r a c t Localized delivery of drugs is an emerging field both with regards to drug delivery during disease as well as in tissue engineering. Despite significant achievements made in the last decades, the efficient delivery of proteins and peptides remains challenging, especially in cases requiring long-term release of proteins after application. The localized delivery of nucleic acids (NA) represents an interesting alternative due to higher physicochemical stability of NA, increased efficiency by harnessing cells as bioreactors for the production of required proteins and improved versatility with regards to expression of specific proteins through plasmid DNA or repression of gene products through siRNA. However, unlike most proteins and peptides, NA must be delivered to the cytoplasm or nucleus to be efficacious, resulting in significant delivery challenges. We herein describe frequently used non-viral vectors for the delivery of NA including polyplexes, lipoplexes and lipopolyplexes and summarize recent developments in the field of nucleic acid delivery systems for local application based on hydrogels, solid scaffolds and physical delivery methods. The challenges associated with the different approaches are identified and options to address these challenges are discussed.

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