Preparation and Characterization of Nanofibrous Membranes Electro-Spun from Blended Poly(l-lactide-co-ε-caprolactone) and Recombinant Spider Silk Protein as Potential Skin Regeneration Scaffold.

Biomaterial scaffolding serves as an important strategy in skin tissue engineering. In this research, recombinant spider silk protein (RSSP) and poly(L-lactide-co-ε-caprolactone) (PLCL) were blended in different ratios to fabricate nanofibrous membranes as potential skin regeneration scaffolds with an electro-spinning process. Scanning electron microscopy (SEM), water contact angles measurement, Fourier transform infrared (FTIR) spectroscopy, wide angle X-ray diffraction (WAXD), tensile mechanical tests and thermo-gravimetric analysis (TGA) were carried out to characterize the nanofibrous membranes. The results showed that the blending of RSSP greatly decreased the nanofibers' average diameter, enhanced the hydrophilicity, changed the microstructure and thermal properties, and could enable tailored mechanical properties of the nanofibrous membranes. Among the blended membranes, the PLCL/RSSP (75/25) membrane was chosen for further investigation on biocompatibility. The results of hemolysis assays and for proliferation of human foreskin fibroblast cells (hFFCs) confirmed the membranes potential use as skin-regeneration scaffolds. Subsequent culture of mouse embryonic fibroblast cells (NIH-3T3) demonstrated the feasibility of the blended membranes as a human epidermal growth factor (hEGF) delivery matrix. The PLCL/RSSP (75/25) membrane possessed good properties comparable to those of human skin with high biocompatibility and the ability of hEGF delivery. Further studies can be carried out on such membranes with chemical or genetic modifications to make better scaffolds for skin regeneration.

Tough synthetic spider-silk fibers obtained by titanium dioxide incorporation and formaldehyde cross-linking in a simple wet-spinning process.

Due to its unique mechanical properties, spider silk shows great promise as a strong super-thin fiber in many fields. Although progress has been made in the field of synthesizing spider-silk fiber from recombinant spidroin (spider silk protein) in the last few decades, methods to obtain synthetic spider-silk fibers as tough as natural silk from small-sized recombinant protein with a simple spinning process have eluded scientists. In this paper, a recombinant spidroin (MW: 93.4 kDa) was used to spin tough synthetic spider-silk fibers with a simple wet-spinning process. Titanium oxide incorporation and formaldehyde cross-linking were used to improve the mechanical properties of synthetic spider-silk fibers. Fibers treated with incorporation or/and cross-linking varied in microstructure, strength and extensibility while all exhibited enhanced strength and toughness. In particular, one fiber possessed a toughness of 249 ± 22 MJ/m3. This paper presents a new method to successfully spin tough spider-silk fibers in a simple way.

Tensile properties of synthetic pyriform spider silk fibers depend on the number of repetitive units as well as the presence of N- and C-terminal domains.

Spiders can spin seven different types of silk, some of which are well characterized, but studies on natural and synthetic pyriform silks are few. In this study, recombinant spidroins composed of one to three pyriform repeat units from Araneus ventricosus, in some cases flanked with non-repetitive N- and C-terminal domains (NT and CT), were produced and spun into continuous silk fibers using a wet-spinning process in organic solvents. All the fibers showed high and similar tensile strain (60-80%), but the Young's modulus, stress and toughness of fibers increased with increasing number of repeat units and in the presence of NT and CT as well. Systematic studies of the secondary structure contents of the different spinning dopes and spun fibers revealed no major differences between the different types of recombinant spidroins. This suggests that optimal tensile properties of artificial spider silks require the presence of several repetitive units as well as terminal domains and that secondary structure content of silk dope and fibers have limited correlation with mechanical behaviors.

Bacterial effector NleL promotes enterohemorrhagic E. coli-induced attaching and effacing lesions by ubiquitylating and inactivating JNK.

As a major diarrheagenic human pathogen, enterohemorrhagic Escherichia coli (EHEC) produce attaching and effacing (A/E) lesions, characterized by the formation of actin pedestals, on mammalian cells. A bacterial T3SS effector NleL from EHEC O157:H7 was recently shown to be a HECT-like E3 ligase in vitro, but its biological functions and host targets remain elusive. Here, we report that NleL is required to effectively promote EHEC-induced A/E lesions and bacterial infection. Furthermore, human c-Jun NH2-terminal kinases (JNKs) were identified as primary substrates of NleL. NleL-induced JNK ubiquitylation, particularly mono-ubiquitylation at the Lys 68 residue of JNK, impairs JNK's interaction with an upstream kinase MKK7, thus disrupting JNK phosphorylation and activation. This subsequently suppresses the transcriptional activity of activator protein-1 (AP-1), which modulates the formation of the EHEC-induced actin pedestals. Moreover, JNK knockdown or inhibition in host cells complements NleL deficiency in EHEC infection. Thus, we demonstrate that the effector protein NleL enhances the ability of EHEC to infect host cells by targeting host JNK, and elucidate an inhibitory role of ubiquitylation in regulating JNK phosphorylation.

A nitroolefin functionalized BODIPY chemodosimeter for biothiols driven by an unexpected conjugated addition mechanism.

A weakly fluorescent nitroolefin functionalized BODIPY 1 was prepared and rapidly reacted with thiols through an unexpected conjugated addition to the azafulvene ring of BODIPY to generate highly fluorescent BODIPYs 4 and 5. This reaction was applied for the highly selective and sensitive detection of Cys in living cells.