Thermally Expanded Graphite Incorporated with PEDOT:PSS Based Anode for Microbial Fuel Cells with High Bioelectricity Production

Modification of anodes with highly biocompatible materials could enhance bacterial adhesion, growth, and improve the rate of electron-transfer ability in microbial fuel cells (MFCs). As such, there has been increasing interest in the development of innovative anode materials to prepare high-performance MFCs. We report the synthesis of poly(3,4-ethylene dioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) doped with thermally expanded graphite (TEG) composite coated carbon felt (CF) as anode for MFCs. For this purpose, as-synthesized PEDOT:PSS/TEG composite was characterized using high-resolution scanning electron microscopy (HR-SEM), and Raman and Fourier transform infrared (FT-IR) spectroscopies which indicated successful incorporation of TEG within PEDOT:PSS film. Furthermore, the electrochemical activity of the PEDOT:PSS/TEG coated CF was employed as the anode in the MFCs with sewage water as an anolyte. PEDOT:PSS/TEG@CF anode exhibited higher ion-transfer ability, superior bio-electrochemical conductivity, and excellent capacitance. Using the PEDOT:PSS/TEG@CF anode, we have constructed MFCs which exhibited good power (68.7 mW/m2) and current (969.3 mA/m2) densities compared to the unmodified CF based anode. The reliability of the MFCs performance was also investigated by testing three independently prepared MFCs with PEDOT:PSS/TEG@CF anodes which all showed a constant voltage (~540 mV) due to the higher stability and biocompatibility of PEDOT:PSS/TEG@CF.

The Effect of Ultraviolet Treatment on TiO2 Nanotubes: A Study of Surface Characteristics, Bacterial Adhesion, and Gingival Fibroblast Response

Titanium dioxide (TiO2) nanotubes are emerging as a provocative target for oral implant research. The aim of this study was to evaluate the effect of UV on the wettability behavior, bacterial colonization, and fibroblast proliferation rate of TiO2 nanotube surfaces prepared using different anodization voltages and aimed for use as implant abutment materials. Four different experimental materials were prepared: (1) TiO2 nanotube 10 V; (2) TiO2 nanotube 15 V; (3) TiO2 nanotube 20 V; and (4) commercial pure titanium as a control group. TiO2 nanotube arrays were prepared in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 vol.%). Different anodization voltages were used to modify the morphology of the TiO2 nanotubes. Equilibrium contact angles were measured using the sessile drop method with a contact angle meter. The investigated surfaces (n = 3) were incubated at 37 °C in a suspension of Streptococcus mutans (S. mutans) for 30 min for bacterial adhesion and 3 days for biofilm formation. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 7 days and the cell proliferation rate was assessed using the AlamarBlue assayTM (BioSource International, Camarillo, CA, USA). The data were analyzed using one-way ANOVA followed by Tukey’s post-hoc test. Water contact angle measurements on the TiO2 after UV treatment showed an overall hydrophilic behavior regardless of the anodization voltage. The ranking of the UV-treated surfaces of experimental groups from lowest to highest for bacterial adhesion was: TiO2 nanotube 20 V < Ti and TiO2 nanotube 15 V < TiO2 nanotube 10 V (p < 0.05), and for bacterial biofilm formation was: TiO2 nanotube 20 V-TiO2 nanotube 10 V < Ti-TiO2 nanotube 15 V (p < 0.05). Fibroblast cell proliferation was lower on TiO2 nanotube surfaces throughout the incubation period and UV light treatment showed no enhancement in cellular response. UV treatment enhances the wettability behavior of TiO2 nanotube surfaces and could result in lower bacterial adhesion and biofilm formation.

A Novel Strategy for Creating an Antibacterial Surface Using a Highly Efficient Electrospray-Based Method for Silica Deposition

Adhesion of bacteria on biomedical implant surfaces is a prerequisite for biofilm formation, which may increase the chances of infection and chronic inflammation. In this study, we employed a novel electrospray-based technique to develop an antibacterial surface by efficiently depositing silica homogeneously onto polyethylene terephthalate (PET) film to achieve hydrophobic and anti-adhesive properties. We evaluated its potential application in inhibiting bacterial adhesion using both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria. These silica-deposited PET surfaces could provide hydrophobic surfaces with a water contact angle greater than 120° as well as increased surface roughness (root mean square roughness value of 82.50 ± 16.22 nm and average roughness value of 65.15 ± 15.26 nm) that could significantly reduce bacterial adhesion by approximately 66.30% and 64.09% for E. coli and S. aureus, respectively, compared with those on plain PET surfaces. Furthermore, we observed that silica-deposited PET surfaces showed no detrimental effects on cell viability in human dermal fibroblasts, as confirmed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide and live/dead assays. Taken together, such approaches that are easy to synthesize, cost effective, and efficient, and could provide innovative strategies for preventing bacterial adhesion on biomedical implant surfaces in the clinical setting.

The Effect of the plant Adiantum philippense Extracts on Biofilms Formation and Adhesion to Shigella flexneri: A Predictive Modelling Approach

In the quest for novel bioactive metabolites, which can also be used as therapeutic agents, Adiantum philippense (A. philippense), an ethnomedically important fern, has become a fascinating herb. In this study, the predictive mathematical modelling of A. philippense crude extract was tested against Shigella flexneri, a common food pathogen for its phytochemical constituents, antagonistic ability, and effect on bacterial adhesion and biofilm formation was calculated. Various kinetics models such as Von Bertalanffy, Baranyi-Roberts, modified Schnute, Modified Richards, Modified Gompertz, Modified Logistics and latest Huang were used to get values for the above kinetic constants or parameters. modified Gompertz of the entire model was found to be the best model with the highest adjusted R2 value and lowest RMSE value. The accuracy and bias factors values were close to unity (1.0). The maximum specific growth rate (mmax (h-1) for S. flexneri treatment with A. philippense extract was significantly much lower (p<0.05) with a value of 0.292 (95% confidence interval of 0.254 to 0.331) compared to control with a value of 0.540 (95% confidence interval of 0.481 to 0.599) indicating potential biofilm inhibition.

Strategies for Antimicrobial Peptides Immobilization on Surfaces to Prevent Biofilm Growth on Biomedical Devices

Nosocomial and medical device-induced biofilm infections affect millions of lives and urgently require innovative preventive approaches. These pathologies have led to the development of numerous antimicrobial strategies, an emergent topic involving both natural and synthetic routes, among which some are currently under testing for clinical approval and use. Antimicrobial peptides (AMPs) are ideal candidates for this fight. Therefore, the strategies involving surface functionalization with AMPs to prevent bacterial attachment/biofilms formation have experienced a tremendous development over the last decade. In this review, we describe the different mechanisms of action by which AMPs prevent bacterial adhesion and/or biofilm formation to better address their potential as anti-infective agents. We additionally analyze AMP immobilization techniques on a variety of materials, with a focus on biomedical applications. Furthermore, we summarize the advances made to date regarding the immobilization strategies of AMPs on various surfaces and their ability to prevent the adhesion of various microorganisms. Progress toward the clinical approval of AMPs in antibiotherapy is also reviewed.