Steroid-grafted silk fibroin conjugates for drug and agrochemical delivery

Self-Assembled Silk Fibroin-Based Aggregates for Delivery of Camptothecin

A water-soluble hydrolysate of silk fibroin (SF) (~30 kDa) was esterified with tocopherol, ergocalciferol, and testosterone to form SF aggregates for the controlled delivery of the anticancer drug camptothecin (CPT). Elemental analysis and ¹H NMR spectroscopy showed a degree of substitution (DS) on SF of 0.4 to 3.8 mol %. Yields of 58 to 71% on vitamins- and testosterone-grafted SF conjugates were achieved. CPT was efficiently incorporated into the lipophilic core of SF aggregates using a dialysis-precipitation method, achieving drug contents of 6.3-8.5 wt %. FTIR spectra and DSC thermograms showed that tocopherol- and testosterone-grafted SF conjugates predominantly adopted a β-sheet conformation. After the esterification of tyrosine residues on SF chains with the vitamin or testosterone, the hydrodynamic diameters almost doubled or tripled that of SF. The zeta potential values after esterification increased to about -30 mV, which favors the stability of aggregates in aqueous medium. Controlled and almost quantitative release of CPT was achieved after 6 days in PBS at 37 °C, with almost linear release during the first 8 h. MCF-7 cancer cells exhibited good uptake of CPT-loaded SF aggregates after 6 h, causing cell death and cell cycle arrest in the G2/M phase. Substantial uptake of the CPT-loaded aggregates into MCF-7 spheroids was shown after 3 days. Furthermore, all CPT-loaded SF aggregates demonstrated superior toxicity to MCF-7 spheroids compared with parent CPT. Blank SF aggregates induced no hemolysis at pH 6.2 and 7.4, while CPT-loaded SF aggregates provoked hemolysis at pH 6.2 but not at pH 7.4. In contrast, parent CPT caused hemolysis at both pH tested. Therefore, CPT-loaded SF aggregates are promising candidates for chemotherapy.

A mussel-inspired supramolecular hydrogel with robust tissue anchor for rapid hemostasis of arterial and visceral bleedings

In recent years, the developed hemostatic technologies are still difficult to be applied to the hemostasis of massive arterial and visceral hemorrhage, owing to their weak hemostatic function, inferior wet tissue adhesion, and low mechanical properties. Herein, a mussel-inspired supramolecular interaction-cross-linked hydrogel with robust mechanical property (308.47 ± 29.20 kPa) and excellent hemostatic efficiency (96.5% ± 2.1%) was constructed as a hemostatic sealant. Typically, we combined chitosan (CS) with silk fibroin (SF) by cross-linking them through tannic acid (TA) to maintain the structural stability of the hydrogel, especially for wet tissue adhesion ability (shear adhesive strength = 29.66 ± 0.36 kPa). Compared with other materials reported previously, the obtained CS/TA/SF hydrogel yielded a lower amount of blood loss and shorter time to hemostasis in various arterial and visceral bleeding models, which could be ascribed to the synergistic effect of wound closure under wet state as well as intrinsic hemostatic activity of CS. As a superior hemostatic sealant, the unique hydrogel proposed in this work can be exploited to offer significant advantages in the acute wound and massive hemorrhage with the restrictive access of therapeutic moieties.