Bactericidal Anti-Adhesion Potential Integrated Polyoxazoline/Silver Nanoparticle Composite Multilayer Film with pH Responsiveness.

Bacterial infections occur frequently during the implantation of medical devices, and functional coating is one of the effective means to prevent and remove biofilms. In this study, three different hydrophilic polyoxazolines with carboxyl groups (aPOx: PT1, PT2 and PT3) and bactericidal silver nanoparticles (AgNPs) were synthesized successfully, and an aPOx-AgNP multilayer film was prepared by electrostatic layer-by-layer self-assembly. The effect of charge density and assembly solution concentration was explored, and the optimal self-assembly parameters were established (PT2 1 mg/mL and AgNPs 3 mg/mL). The hydrophilicity of the surface can be enhanced to resist protein adhesion if the outermost layer is aPOx, and AgNPs can be loaded to kill bacteria, thereby realizing the bactericidal anti-adhesion potential integration of the aPOx-AgNP multilayer film. In addition, the aPOx-AgNP multilayer film was found to have the characteristic of intelligent and efficient pH-responsive silver release, which is expected to be used as a targeted anti-biofilm surface of implantable medical devices.

Ultrastretchable, self-adhesive, strain-sensitive and self-healing GO@DA/Alginate/P(AAc-co-AAm) multifunctional hydrogels via mussel-inspired chemistry.

For conductive hydrogels applied in biosensors, wearable devices and so forth, multifunctionality is an inevitable trend of development to meet various practical requirements and enhance human experience. Herein, inspired by nanocomposite, double-network (DN) and mussel chemistry, a new Graphene oxide@Dopamine/Alginate/Poly(acrylic acid-co-acrylamide) [GO@DA/Alginate/P(AAc-co-AAm)] hydrogel was fabricated through one-pot in-situ radical copolymerization. GO@DA nanofillers, prepared via GO confined DA polymerization, imparted the hydrogel with remarkable adhesiveness. Alginate/P(AAc-co-AAm) DN matrix, physically and chemically crosslinked by Fe3+ and N,N'-Methylenebisacrylamide, made hydrogels ultrastretchable, self-healing and biocompatible. With contents of DA and alginate accurately regulated, the tensile strength, elongation, adhesion strength and conductivity of the optimal hydrogel could reach 320.2 kPa, 1198 %, 36.9 kPa and 3.24 ± 0.12 S/m, respectively. What's more notable was that the synergistic integration of repeatable adhesiveness, strain sensitivity, use stability, self-healing ability and biocompatibility provided such hydrogels with tremendous possibility of practical application for strain sensors.

High strength graphene oxide/chitosan composite screws with a steel-concrete structure.

Due to the biocompatibility, biodegradability and numerous resources of chitosan (CS), CS screws attract much more attention, as a new generation of internal fixation devices. Herein, a facile solution-casting method was utilized to fabricate CS composite screws with a steel-concrete structure by combining graphene oxide (GO) and CS fiber bundles. The embedding GO endowed CS screws with a Honeycomb-Cobweb network. And CS screws reinforced with CS fiber bundles of four arrangement sequences could endure different degrees of external force. The optimal arrangement type of CS fiber bundles (the linear type) and addition amount of GO (0.15 wt%) was utilized to construct the steel-concrete structure. Due to the mechanical interlocking between the GO/CS matrices and CS fiber bundles, the bending strength of CS composite screws, with such an unusual structure, could reach high up to 378 MPa, approximately 1.88 times the blank control group was. The findings stand out as a new tool to prepare high bending strength screws and the steel-concrete structure might be used effectively in more critical load-bearing situations.

Catechol-Functional Chitosan/Silver Nanoparticle Composite as a Highly Effective Antibacterial Agent with Species-Specific Mechanisms.

In this study, silver nanoparticles (Ag NPs) coated with catechol-conjugated chitosan (CSS) were prepared using green methods. Interestingly, we uncovered that CSS-coated Ag NPs (CSS-Ag NPs) exhibited a higher toxicity against gram-negative Escherichia coli (E. coli) bacteria than against gram-positive Staphylococcus aureus (S. aureus) bacteria. The differences revealed that the CSS-Ag NPs killed gram bacteria with distinct, species-specific mechanisms. The aim of this study is to further investigate these underlying mechanisms through a series of analyses. The ultrastructure and morphology of the bacteria before and after treatment with CSS-Ag NPs were observed. The results demonstrated the CSS-Ag NPs killed gram-positive bacteria through a disorganization of the cell wall and leakage of cytoplasmic content. In contrast, the primary mechanism of action on gram-negative bacteria was a change in membrane permeability, induced by adsorption of CSS-Ag NPs. The species-specific mechanisms are caused by structural differences in the cell walls of gram bacteria. Gram-positive bacteria are protected from CSS-Ag NPs by a thicker cell wall, while gram-negatives are more easily killed due to an interaction between a special outer membrane and the nanoparticles. Our study offers an in-depth understanding of the antibacterial behaviors of CSS-Ag NPs and provides insights into ultimately optimizing the design of Ag NPs for treatment of bacterial infections.