Tunable repeated drug administration is often inevitable in a number of pathological cases. Reloadable 3D matrices for sustained drug delivery are predicted as a prospective avenue to realize this objective. This study was directed toward sonication-induced fabrication of novel reloadable Bombyx mori silk fibroin (SF) (4, 6, and 8 wt %) hydrogel, injected within 3D porous (8 wt %) scaffolds. The focus was to develop a dual-barrier reloadable depot system for sustained molecular cargo release. Both the varying SF concentration (4, 6, and 8 wt %) and the sonication time (30, 45, and 60 s) dictated the extent of cross-linking, β-sheet content, and porosity (1-10 μm) influencing the release behavior of model molecules. Release studies of model molecules (trypan blue, TB, 961 Da and bovine serum albumin, BSA, 66 kDa) for 28 days attested that the variations in their molecular weight, the matrix cross-linking density, and the scaffold-hydrogel interactions dictated the release behavior. The Ritger and Peppas equation was further fitted into the release behavior of model molecules from various SF matrices. The hybrid constructs exhibited high compressive strength along with in vitro compatibility using primary porcine chondrocytes and tunable enzymatic degradation as assessed for 28 days. The aptness of the constructs was evinced as a reloadable model molecule (BSA and fluorescein isothiocyanate-inulin, 3.9 kDa) depot system through UV-visible and fluorescence spectroscopic analyses. The novel affordable platform developed using silk scaffold-hydrogel hybrid constructs could serve as a sustained and reloadable drug depot system for administration of multiple and repeated drugs.

Development and characterization of porous scaffolds for tissue engineering and regenerative medicine is of great importance. In recent times, silk scaffolds were developed and successfully tested in tissue engineering and drug release applications. We developed a novel composite scaffold by mechanical infusion of silk hydrogel matrix into a highly porous network silk scaffold. The mechanical behaviour of these scaffolds was thoroughly examined for their possible use in load bearing applications. Firstly, unconfined compression experiments show that the denser composite scaffolds displayed significant enhancement in the elastic modulus as compared to either of the components. This effect was examined and further explained with the help of foam mechanics principles. Secondly, results from confined compression experiments that resemble loading of cartilage in confinement, showed nonlinear material responses for all scaffolds. Finally, the confined creep experiments were performed to calculate the hydraulic permeability of the scaffolds using soil mechanics principles. Our results show that composite scaffolds with some modifications can be a potential candidate for use of cartilage like applications. We hope such approaches help in developing novel scaffolds for tissue engineering by providing an understanding of the mechanics and can further be used to develop graded scaffolds by targeted infusion in specific regions.

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The advent of COVID-19 pandemic has made it necessary to wear masks across populations. While the N95 mask offers great performance against airborne infections, its multilayered sealed design makes it difficult to breathe for a longer duration of use. The option of using highly breathable cloth or silk masks especially for a large populace is fraught with the danger of infection. As a normal cloth or silk mask absorbs airborne liquid, it can be a source of plausible infection. We demonstrate the chemical modification of one such mask, Eri silk, to make it hydrophobic (contact angle of water is 143.7°), which reduces the liquid absorption capacity without reducing the breathability of the mask significantly. The breathability reduces only 22% for hydrophobic Eri silk compared to the pristine Eri silk, whereas N95 shows a 59% reduction of breathability. The modified hydrophobic silk can repel the incoming aqueous liquid droplets without wetting the surface. The results indicate that a multilayered modified silk mask to make it hydrophobic can be an affordable and breathable alternative to the N95 mask.

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