As locomotive organelles, flagella allow bacteria to move toward favorable environments. A flagellum consists of three parts: the basal structure (rotary motor), the hook (universal joint), and the filament (helical propeller). For ages, flagella have been generally regarded as important virulence factors, mainly because of their motility property. However, flagella are getting recognized to play multiple roles with more functions besides motility and chemotaxis. Recent evidence has pinpointed that the bacterial flagella participate in many additional processes including adhesion, biofilm formation, virulence factor secretion, and modulation of the immune system of eukaryotic cells. This mini-review summarizes data from recent studies that elucidated how flagella, as a virulence factor, contribute to bacterial pathogenicity.

Despite advances in the development of silk fibroin (SF)-based hydrogels, current methods for SF gelation show significant limitations such as lack of reversible crosslinking, use of nonphysiological conditions, and difficulties in controlling gelation time. In the present study, a strategy based on dynamic metal-ligand coordination chemistry is developed to assemble SF-based hydrogel under physiological conditions between SF microfibers (mSF) and a polysaccharide binder. The presented SF-based hydrogel exhibits shearthinning and autonomous self-healing properties, thereby enabling the filling of irregularly shaped tissue defects without gel fragmentation. A biomineralization approach is used to generate calcium phosphate-coated mSF, which is chelated by bisphosphonate ligands of the binder to form reversible crosslinkages. Robust dually crosslinked (DC) hydrogel is obtained through photopolymerization of acrylamide groups of the binder. DC SF-based hydrogel supports stem cell proliferation in vitro and accelerates bone regeneration in cranial critical size defects without any additional morphogenes delivered. The developed self-healing and photopolymerizable SF-based hydrogel possesses significant potential for bone regeneration application with the advantages of injectability and fit-to-shape molding.

Cellulose nanofibers (CNFs) aerogels with controllable surface wettability were prepared by grafting poly(N,N-dimethylamino-2ethyl methacrylate) (PDMAEMA) polymer brushes via surface-initiated atom-transfer radical polymerization. After grafting PDMAEMA polymer, the surface of the aerogel was hydrophobic. However, in the presence of CO 2 , the surface of the aerogel gradually changes from hydrophobic to hydrophilic. The porous structure and CO 2 -responsiveness of PDMAE-MA brushes within the CNFs aerogels allowed for the on−off switching of the oil−water mixture separation process. These CNFs aerogels were recyclable and displayed attractive separation efficiency for oil−water mixture and surfactant-stabilized emulsions. Furthermore, the switchable surface wettability holds an advantage of avoiding oil-fouling, which will greatly improve its recyclability.

Silk-based nanoparticles have been exhibiting an increasing potential for use as drug delivery systems due to their great versatility. To extend applications of silk sericin in nanomedicine and improve the performance of silk-based nanoparticles in drug delivery, a facile two-step cross-linking is attempted, for the first time, to fabricate surface charge-reversal silk sericin-based nanoparticles (SSC@NPs) by introducing chitosan into silk sericin. The results suggest stable SSC@NPs are formed with a negative surface charge in a neutral environment. Under mildly acidic conditions, however, surface charge of SSC@NPs undergoes a negative-to-positive conversion. It proves that pH can regulate surface charge of SSC@NPs. It is the increased amino/carboxyl ratio in SSC@NPs that explains the underlying mechanism of the charge conversion property of SSC@NPs. Furthermore, the positively charged SSC@NPs triggered by tumor acidic microenvironment (pH 6.0) result in a 6.0fold higher cellular uptake than the negatively charged counterparts at pH 7.4. In addition, an anticancer drug doxorubicin (DOX) is readily loaded into SSC@NPs and released in a pH-dependent manner. This work provides a simple method to fabricate smart pH-responsive nanoparticles for anticancer drug delivery.

Pure chitosan membranes present insufficient mechanical properties and a high swelling ratio, which limits their application in biomedical field. In this study, silk microfibers were obtained by chemical hydrolysis, and a novel type of chitosan/silk microfiber (CS/mSF) blended membrane was reported and its multiple physical properties were evaluated. The mechanical properties were significantly improved after blending silk microfibers with a chitosan matrix, while the swelling ratio was decreased. Observation of the surface microstructures of the blended membranes via scanning electron microscopy showed abundant embedding of mSF into the CS matrix, as well as connections among mSF. In vitro cytocompatibility was also investigated, and the blended membranes exhibited significant cytocompatibility, which was demonstrated by cell proliferation and cell morphology. Furthermore, the in vivo healing effects of the blended membrane as a wound dressing were determined on a full-thickness skin wound model of rats.Animal studies revealed that the membranes containing mSF exhibited increased wound healing efficiency compared with pure CS membranes and treatment without wound dressing. From an examination of histological changes, a higher level of epithelialization and collagen formation was observed with treatment of CS/mSF blended membranes after a 21 day repair period. In conclusion, our results indicated that the blended membranes with CS and mSF might be a potential candidate material for wound healing.