Advanced antifouling and antibacterial hydrogels enabled by controlled thermo-responses of a biocompatible polymer composite

To optimally apply antibiotics and antimicrobials, smart wound dressing conferring controlled drug release and preventing adhesions of biological objects is advantageous. Poly(; N; -isopropylacrylamide) (PNIPAAm), a conventional thermo-responsive polymer, and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), a typical antifouling polymer, have therefore potential to be fabricated as copolymers to achieve dual functions of thermo-responsiveness and antifouling. Herein, a hydrogel made of PNIPAM-; co; -PMPC was designed and loaded with octenidine, a widely applied antimicrobial agent for wound treatment, to achieve both antifouling and triggered drug release. The thermo-switch of the fabricated hydrogel allowed 25-fold more octenidine release at 37 °C (infected wound temperature) than at 30 °C (normal skin temperature) after 120 minutes, which led to at least a 3 lg reduction of the viable bacteria at 37 °C on artificially infected wounds. Furthermore, we pioneeringly assessed the antifouling property of the material in PBS buffer using single molecule/cell/bacterial force spectroscopy, and revealed that the fabricated hydrogel displayed distinctive antifouling properties against proteins, mammalian cells, and bacteria. This work demonstrated a promising design of a hydrogel applicable for preventing and treating wound infections. The concept of dual-functional materials can be envisaged for other clinical applications related to the prevention of biofilm-associated infections, such as urinary catheters, stents, and dental implants

pH-responsive silica nanoparticles for the treatment of skin wound infections

Chronic wounds are not only a burden for patients but also challenging for clinic treatment due to biofilm formation. Here, we utilized the phenomenon that chronic wounds possess an elevated local pH of 8.9 and developed pH-sensitive silica nanoparticles (SiNPs) to achieve a targeted drug release on alkaline wounds and optimized drug utility. Chlorhexidine (CHX), a disinfectant and antiseptic, was loaded into SiNPs as the model drug. The loaded CHX displayed a release 4 - 5 fold higher at pH 8.0 and 8.5 than at pH 6.5, 7.0 and 7.4. CHX-SiNPs furthermore exhibited a distinctive antibacterial activity at pH 8.0 and 8.5 against both Gram-negative and -positive bacterial pathogens, while no cytotoxicity was found according to cell viability analysis. The CHX-SiNPs were further formulated into alginate hydrogels to allow ease of use. The antibacterial efficacy of CHX-SiNPs was then studied with artificial wounds on ex vivo human skin. Treatment with CHX-SiNPs enabled nearly a 4-lg reduction of the viable bacterial cells, and the alginate formulated CHX-SiNPs led to almost a 3-lg reduction compared to the negative controls. The obtained results demonstrated that CHX-SiNPs are capable of efficient pH-triggered drug release, leading to high antibacterial efficacy. Moreover, CHX-SiNPs enlighten clinic potential towards the treatment of chronic wound infections. STATEMENT OF SIGNIFICANCE: A platform for controlled drug release at a relatively high pH value i.e., over 8, was established by tuning the physical structures of silica nanoparticles (SiNPs). Incorporation of chlorhexidine, an antimicrobial agent, into the fabricated SiNPs allowed a distinctive inhibition of bacterial growth at alkaline pHs, but not at acidic pHs. The efficacy of the SiNPs loaded with chlorhexidine in treating wound infections was further validated by utilizing ex vivo human skin samples. The presented work demonstrates clinic potential of employing alkaline pH as a non-invasive stimulus to achieve on-demand delivery of antimicrobials through SiNPs, showcasing a valuable approach to treating bacterial infections on chronic wounds

Plasma-deposited AgOx-doped TiOx coatings enable rapid antibacterial activity based on ROS generation

Abstract To enable a rapid-acting antibacterial mechanism without the release of biocidal substances, TiO2 catalysts have been considered based on the generation of reactive oxygen species (ROS). Doping with dissimilar metals generates electron-hole pairs with narrow band gaps promoting the production of ROS. Here, plasma technology is investigated to deposit Ag nano islets on defective TiOx films, stabilized by plasma postoxidation suppressing Ag ion release. Importantly, ROS generation is maintained upon storage in the dark yet with diminishing efficacy; however, it can be restored by exposure to visible light. The rapid-acting antibacterial properties are found to strongly correlate with ROS generation, which can even be maintained by functionalization with hydrophobic plasma polymer films. The cytocompatible coatings offer promising applications for implants and other medical devices

Nanostructured surface topographies have an effect on bactericidal activity

Abstract Background Due to the increased emergence of antimicrobial resistance, alternatives to minimize the usage of antibiotics become attractive solutions. Biophysical manipulation of material surface topography to prevent bacterial adhesion is one promising approach. To this end, it is essential to understand the relationship between surface topographical features and bactericidal properties in order to develop antibacterial surfaces. Results In this work a systematic study of topographical effects on bactericidal activity of nanostructured surfaces is presented. Nanostructured Ormostamp polymer surfaces are fabricated by nano-replication technology using nanoporous templates resulting in 80-nm diameter nanopillars. Six Ormostamp surfaces with nanopillar arrays of various nanopillar densities and heights are obtained by modifying the nanoporous template. The surface roughness ranges from 3.1 to 39.1 nm for the different pillar area parameters. A Gram-positive bacterium, Staphylococcus aureus, is used as the model bacterial strain. An average pillar density at ~ 40 pillars μm−2 with surface roughness of 39.1 nm possesses the highest bactericidal efficiency being close to 100% compared with 20% of the flat control samples. High density structures at ~ 70 pillars μm−2 and low density structures at < 20 pillars μm−2 with surface roughness smaller than 20 nm reduce the bactericidal efficiency to almost the level of the control samples. Conclusion The results obtained here suggests that the topographical effects including pillar density and pillar height inhomogeneity may have significant impacts on adhering pattern and stretching degree of bacterial cell membrane. A biophysical model is prepared to interpret the morphological changes of bacteria on these nanostructures

In Situ Investigation of Pseudomonas aeruginosa Biofilm Development: Interplay between Flow, Growth Medium, and Mechanical Properties of Substrate

To better understand the impact of biomaterial mechanical properties and growth medium on bacterial adhesion and biofilm formation under flow, we investigated the biofilm formation ability of Pseudomonas aeruginosa in different media on polydimethylsiloxane (PDMS) of different stiffness in real time using a microfluidic platform. P. aeruginosa colonization was recorded with optical microscopy and automated image analysis. The bacterial intracellular level of cyclic diguanylate (c-di-GMP), which regulates biofilm formation, was monitored using the transcription of the putative adhesin gene (cdrA) as a proxy. Contrary to the previous supposition, we revealed that PDMS material stiffness within the tested range has negligible impact on biofilm development and biofilm structures, whereas culture media not only influence the kinetics of biofilm development but also affect the biofilm morphology and structure dramatically. Interestingly, magnesium rather than previously reported calcium was identified here to play a decisive role in the formation of dense P. aeruginosa aggregates and high levels of c-di-GMP. These results demonstrate that although short-term adhesion assays bring valuable insight into bacterial and material interactions, long-term evaluations are essential to better predict overall biofilm outcome. The microfluidic system developed here presents a valuable application potential for studying biofilm development in situ.

MOESM1 of Nanostructured surface topographies have an effect on bactericidal activity

Additional file 1: Figure S1. Fabrication of nanostructured Ormostamp surfaces. Figure S2. Fluorescence image of S. aureus cells on smooth control surface. Figure S3. Quantification of bactericidal efficiency by proliferation measuremen. Figure S4. SEM images of S. aureus cells on nanostructured Ormostamp surfaces S(a)-S(f). Figure S5. Biophysical model of bacterial cells adhered on nanostructured surfaces

Surface Chemistry Dictates the Osteogenic and Antimicrobial Properties of Palladium-, Platinum-, and Titanium-Based Bulk Metallic Glasses

Titanium alloys are commonly used as biomaterials in musculoskeletal applications, but their long-term efficacy can be limited by wear and corrosion, stress shielding, and bacterial colonization. As a promising alternative, bulk metallic glasses (BMGs) offer superior strength and corrosion resistance, but the influence of their chemical composition on their bioactivity remains largely unexplored. This study, therefore, aims to examine how the surface chemistry of palladium (Pd)-, platinum (Pt)-, and titanium (Ti)-based BMGs can steer their response to biological systems. The chemical composition of BMGs governs their thermophysical and mechanical properties, with Pd-based BMGs showing exceptional glass-forming ability suitable for larger implants, and all BMGs exhibiting a significantly lower Young's modulus than Ti-6Al-4 V (Ti64), suggesting a potential to reduce stress shielding. Although BMGs feature copper depletion at the near surface, their surface chemistry remains more stable than that of Ti64 and supports blood biocompatibility. Fibrin network formation is heavily dependent on BMGs’ chemical composition and Ti-based BMGs support thicker fibrin network formation than Ti64. Furthermore, BMGs outperform Ti64 in promoting mineralization of human bone progenitor cells and demonstrate antimicrobial properties against Staphylococcus aureus in a surface chemistry-dependent manner, thereby indicating their great potential as biomaterials for musculoskeletal applications.ISSN:1616-3028ISSN:1616-301

Robust Antibacterial Activity of Xanthan-Gum-Stabilized and Patterned CeO2–x–TiO2 Antifog Films

Increased occurrence of antimicrobial resistance leads to a huge burden on patients, the healthcare system, and society worldwide. Developing antimicrobial materials through doping rare-earth elements is a new strategy to overcome this challenge. To this end, we design antibacterial films containing CeO; 2-; x; -TiO; 2; , xanthan gum, poly(acrylic acid), and hyaluronic acid. CeO; 2-; x; -TiO; 2; inks are additionally integrated into a hexagonal grid for prominent transparency. Such design yields not only an antibacterial efficacy of ∼100% toward; Staphylococcus aureus; and; Escherichia coli; but also excellent antifog performance for 72 h in a 100% humidity atmosphere. Moreover, FluidFM is employed to understand the interaction in-depth between bacteria and materials. We further reveal that reactive oxygen species (ROS) are crucial for the bactericidal activity of; E. coli; through fluorescent spectroscopic analysis and SEM imaging. We meanwhile confirm that Ce; 3+; ions are involved in the stripping phosphate groups, damaging the cell membrane of; S. aureus; . Therefore, the hexagonal mesh and xanthan-gum cross-linking chains act as a reservoir for ROS and Ce; 3+; ions, realizing a long-lasting antibacterial function. We hence develop an antibacterial and antifog dual-functional material that has the potential for a broad application in display devices, medical devices, food packaging, and wearable electronics

Role of the Surface Nanoscale Roughness of Stainless Steel on Bacterial Adhesion and Microcolony Formation

Hospital-acquired infections can cause serious complications and are a severe problem because of the increased emergence of antibiotic-resistant bacteria. Biophysical modification of the material surfaces to prevent or reduce bacteria adhesion is an attractive alternative to antibiotic treatment. Since stainless steel is a widely used material for implants and in hospital settings, in this work, we used stainless steel to investigate the effect of the material surface topographies on bacterial adhesion and early biofilm formation. Stainless steel samples with different surface roughnesses <i>R</i>_q in a range of 217.9–56.6 nm (<i>R</i>_a in a range of 172.5–45.2 nm) were fabricated via electropolishing and compared for adhesion of bacterial pathogens Pseudomonas aeruginosa and Staphylococcus aureus. It was found that the number of viable cells on the untreated rough surface was at least 10-fold lower than those on the electropolished surfaces after 4 h of incubation time for P. aeruginosa and 15-fold lower for S. aureus. Fluorescence images and scanning electron microscopy images revealed that the bacterial cells tend to adhere individually as single cells on untreated rough surfaces. In contrast, clusters of the bacterial cells (microcolonies) were observed on electropolished smooth surfaces. Our study demonstrates that nanoscale surface roughness can play an important role in restraining bacterial adhesion and formation of microcolonies