Protein-coated nanostructured surfaces affect the adhesion of Escherichia coli

Towards a better understanding of the effect of protein conditioning layers on microbial adhesion: a focused investigation of fibronectin and bovine serum albumin layers on SiO2 surfaces

The interaction of foreign implants with their surrounding environment is significantly influenced by the adsorption of proteins on the biomaterial surfaces, playing a role in microbial adhesion. Therefore, understanding protein adsorption on solid surfaces and its effect on microbial adhesion is essential to assess the associated risk of infection. The aim of this study is to evaluate the effect of conditioning by fibronectin (Fn) or bovine serum albumin (BSA) protein layers of silica (SiO2) surfaces on the adhesion and detachment of two pathogenic microorganisms: Pseudomonas aeruginosa PAO1-Tn7-gfp and Candida albicans CIP 48.72. Experiments are conducted under both static and hydrodynamic conditions using a shear stress flow chamber. Through the use of very low wall shear stresses, the study brings the link between the static and dynamic conditions of microbial adhesion. The results reveal that the microbial adhesion critically depends on: (i) the presence of a protein layer conditioning the SiO2 surface, (ii) the type of protein and (iii) the protein conformation and organization in the conditioning layer. In addition, a very distinct adhesion behaviour of P. aeruginosa is observed towards the two tested proteins, Fn and BSA. This effect is reinforced by the amount of proteins adsorbed on the surface and their organization in the layer. The results are discussed in the light of atomic force microscopy analysis of the organization and conformation of proteins in the layers after adsorption on the SiO2 surface, as well as the specificity in bacterial behaviour when interacting with these protein layers. The study also demonstrates the very distinctive behaviours of the prokaryote P. aeruginosa PAO1-Tn7-gfp compared to the eukaryote C. albicans CIP 48.72. This underscores the importance of considering species-specific interactions between the protein conditioning layer and different pathogenic microorganisms, which appear crucial in designing tailored anti-adhesive surfaces.

Biofouling on titanium implants: a novel formulation of poloxamer and peroxide for in situ removal of pellicle and multi-species oral biofilm

Eradicating biofouling from implant surfaces is essential in treating peri-implant infections, as it directly addresses the microbial source for infection and inflammation around dental implants. This controlled laboratory study examines the effectiveness of the four commercially available debridement solutions '(EDTA (Prefgel®), NaOCl (Perisolv®), H2O2 (Sigma-Aldrich) and Chlorhexidine (GUM® Paroex®))' in removing the acquired pellicle, preventing pellicle re-formation and removing of a multi-species oral biofilm growing on a titanium implant surface, and compare the results with the effect of a novel formulation of a peroxide-activated 'Poloxamer gel (Nubone® Clean)'. Evaluation of pellicle removal and re-formation was conducted using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy to assess the surface morphology, elemental composition and chemical surface composition. Hydrophilicity was assessed through contact angle measurements. The multi-species biofilm model included Streptococcus oralis, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomitans, reflecting the natural oral microbiome's complexity. Biofilm biomass was quantified using safranin staining, biofilm viability was evaluated using confocal laser scanning microscopy, and SEM was used for morphological analyses of the biofilm. Results indicated that while no single agent completely eradicated the biofilm, the 'Poloxamer gel' activated with 'H2O2' exhibited promising results. It minimized re-contamination of the pellicle by significantly lowering the contact angle, indicating enhanced hydrophilicity. This combination also showed a notable reduction in carbon contaminants, suggesting the effective removal of organic residues from the titanium surface, in addition to effectively reducing viable bacterial counts. In conclusion, the 'Poloxamer gel + H2O2' combination emerged as a promising chemical decontamination strategy for peri-implant diseases. It underlines the importance of tailoring treatment methods to the unique microbial challenges in peri-implant diseases and the necessity of combining chemical decontaminating strategies with established mechanical cleaning procedures for optimal management of peri-implant diseases.

Facile Preparation of the ZnSe/Ag2Se Binary Heterojunction for Photocatalytic Antibacterial Efficiency

In a novel approach that capitalized on the differential solubility product (Ksp) of ZnSe and Ag2Se, a unique ZnSe/Ag2Se binary heterostructure was efficiently synthesized in situ. ZnSe/Ag2Se exhibited excellent antimicrobial efficiency under visible light. Incorporating Ag2Se into ZnSe significantly enhanced the photoelectric performance of the catalyst, greatly accelerating the separation of the photogenerated electrons in the system. Active species removal experiments determined that ·O2- and H2O2 played crucial roles in photocatalytic antibacterial efficiency. Further investigation into the levels of cellular membrane peroxidation, bacterial morphology, and intracellular contents concentration revealed that during the photocatalytic antimicrobial process, reactive oxygen species initially oxidize phospholipids in the cell membrane, leading to damage to the external structure of the cell and leakage of the intracellular contents, ultimately resulting in bacteria inactivation. The photocatalytic antimicrobial process of ZnSe/Ag2Se fundamentally deviates from conventional methods, offering new insights into efficient disinfection and photocatalytic antimicrobial mechanisms.

Heat-induced amorphous aggregates assembly of soy protein modulate in vitro digestibility of potato starch

This research focused on the characteristics of amorphous aggregates derived from soy protein (SPAA), and their effects on the structural, physicochemical, and digestive properties of potato starch (PS). The SPAA induced by different heating temperatures at pH 7.0 formed an inhomogeneous spherical structure. The presence of SPAA could improve the degree of short-range order of starch, increase thermal stability, reduce pasting viscosity and breakdown, and setback viscosity values of PS. For the PS complexed with SPAAs under simulated cooking conditions, the fraction of digested starch at 300 min (C₃₀₀) decreased by 6-14 %, and rapid digestible starch content (RDS) decreased by 18-25 %, while the slowly digestible starch (SDS) and resistant starch (RS) increased by 0.4-3 % and 15-23 %, respectively. The SPAA at higher temperature treatment (SPAA₁₃₀) reduced digestive rate coefficient (k) values more significantly than SPAA at a lower temperature (SPAA₇₀, SPAA₉₀, SPAA₁₁₀). And the SPAA had no inhibitory effect on α-amylase. The results of this study would significantly contribute to expanding the theoretical information about protein regulation in starch digestion and promoting the development of healthy foods with digestion-resistant properties.

Nanomechanical probing of bacterial adhesion to biodegradable Zn alloys

Bacterial infections on implants cause an inflammatory response and even implant failure. Bacterial adhesion is an initial and critical step during implant infection. The prevention of bacterial adhesion to implant materials has attracted much attention, especially for biodegradable metals. A deep understanding of the mechanisms of bacterial adhesion to biodegradable metals is urgently needed. In this work, a bacterial probe based on atomic force spectroscopy was employed to determine the bacterial adhesion to Zn alloy, which depended on surface charge, roughness, and wettability. Negative surface charges of Zn, Zn-0.5Li, and 316L generated electrostatic repulsion force towards bacteria. The surface roughness of Zn-0.5Li was significantly increased by localized corrosion. Bacterial adhesion forces on Zn, Zn-0.5Li, and 316L were 325.2 pN, 519.1 pN, and 727.7 pN, respectively. The density of attached bacteria (early-stage bacterial adhesion) on these samples exhibited a positive correlation with the bacterial adhesion force. The bacterial adhesion force and adhesion work provide a quantitative determination of the interactions between bacteria and biodegradable alloys. These results provide a deeper understanding of early bacterial adhesion on Zn alloys, which can further guide the antibacterial surface design of biodegradable materials for clinical application.