Binding Quantum Dots to Silk Biomaterials for Optical Sensing

Quantum dots (QDs), have great potential for fabricating optical sensing devices and imaging biomaterial degradation in vivo. In the present study, 2-mercaptoethylamine- (MEA-) and mercaptopropionic acid- (MPA-) capped CdTe-QDs were physically incorporated in silk films that contained a high content (>30%) of crystalline beta-sheet structure. The beta-sheets were induced by the addition of glycerol, water annealing, glycerol/annealing, or treatment with methanol. Incorporation of QDs did not influence the formation of beta-sheets. When the films were extracted with water, most QDs remained associated with the silk, based on the retention of photoluminescence in the silk films and negligible photoluminescence in the extracts. Compared to the solution state, photoluminescence intensity significantly decreased for MEA-QDs but not for MPA-QDs in the silk films, while the emission maximum blue shifted (≈4 nm) slightly for both. Further film digestion using protease XIV, alpha-chymotrypsin, and the combination of the two proteases suggested that QDs may be bound to the silk beta-sheet regions but not the amorphous regions. QDs photoluminescence in silk films was quenched when the concentration of hydrogen peroxide (H2O2) was above 0.2-0.3 mM, indicating the QDs-incorporated silk films can be used to report oxidation potential in solution

Preparation and properties of silk fibroin hydrogel for biological dressing

As a protective layer of a wound, the medical dressing plays an important role in the healing of the wound. The hydrogel dressing is appeared as a new type of medical dressings and has become a research hotspot. Silk fibroin is a natural polymer protein with excellent biocompatibility, mechanical properties, and various plasticity. In this paper, a drug-loaded silk fibroin hydrogel by the polyethylene glycol was coated on cotton fabrics. The obtained biomedical functional textile dressing had antibacterial properties and biocompatibility

Inhibition of the proton-activated chloride channel PAC by PIP2

Proton-activated chloride (PAC) channel is a ubiquitously expressed pH-sensing ion channel, encoded by PACC1 (TMEM206). PAC regulates endosomal acidification and macropinosome shrinkage by releasing chloride from the organelle lumens. It is also found at the cell surface, where it is activated under pathological conditions related to acidosis and contributes to acid-induced cell death. However, the pharmacology of the PAC channel is poorly understood. Here, we report that phosphatidylinositol (4,5)-bisphosphate (PIP2) potently inhibits PAC channel activity. We solved the cryo-electron microscopy structure of PAC with PIP2 at pH 4.0 and identified its putative binding site, which, surprisingly, locates on the extracellular side of the transmembrane domain (TMD). While the overall conformation resembles the previously resolved PAC structure in the desensitized state, the TMD undergoes remodeling upon PIP2-binding. Structural and electrophysiological analyses suggest that PIP2 inhibits the PAC channel by stabilizing the channel in a desensitized-like conformation. Our findings identify PIP2 as a new pharmacological tool for the PAC channel and lay the foundation for future drug discovery targeting this channel

Fabrication and drug release properties of curcumin-loaded silk fibroin nanofibrous membranes

This paper describes a silk fibroin-based nanofibrous membranes loaded with antitumor drugs curcumin and 5-fluorouracil using electrospinning technique. The concentration of curcumin/5-fluorouracil in the silk fibroin solution for electrospinning was optimized to be 0.15/0.25, 0.3/0.5, and 0.45/0.75 wt%. The morphology, hydrophilic property, pore size, secondary structure, and antitumor drugs release of nanofibrous membranes were measured. The diameter of nanofibrous membranes ranged about 100–200 nm. The results indicated that electrospinning process did not influence the secondary structure and the drug content of antitumor drugs, and dual drugs encapsulated in the silk fibroin nanofibrous membranes were released in a steady and consistent process. In conclusion, the silk fibroin-based drug-loaded membranes can be useful as biomaterials with antitumor function

Self-Assembling Silk-Based Nanofibers with Hierarchical Structures

Self-assembling fibrous supramolecular assemblies with sophisticated hierarchical structures at the mesoscale are of interest from both fundamental and applied engineering. In this paper, the relatively hydrophilic domains of silk fibroin (HSF) were extracted and used in studies of self-assembly. The HSF fraction spontaneously self-assembled into nanofibers, 10 to 100 μm long and 50 to 250 nm in diameter, within 2 to 8 h in aqueous conditions. Interestingly, these HSF nanofibers consisted of dozens of nanofibrils arranged in a parallel organization with assembled diameters of ∼30 nm, similar to the sophisticated hierarchical structure observed in native silk fibers. Dynamic morphology and conformation studies were carried out to determine the mechanisms underlying the HSF self-assembly process at both the nanoscale and mesoscale. The HSF self-assembled into nanofibers in a bottom-to-up manner, from “sticky” colloid particles to cylindrical globules, to form nanofibrous networks. Because of the enhanced HSF self-assembling kinetics and the hierarchical structure of HSF nanofibers, this hydrophilicity-driven approach provides further insight into silk fibroin (SF) self-assembly in vivo and also offers new tools for the recapitulation of high-performance materials for engineering applications