Role of silver ions in destabilization of intermolecular adhesion forces measured by atomic force microscopy in Staphylococcus epidermidis biofilms

Nanomaterial-based drug-delivery system as an aid to antimicrobial photodynamic therapy in treating oral biofilm

Diverse microorganisms live as biofilm in the mouth accounts for oral diseases and treatment failure. For decades, the prevention and treatment of oral biofilm is a global challenge. Antimicrobial photodynamic therapy (aPDT) holds promise for oral biofilm elimination due to its several traits, including broad-spectrum antimicrobial capacity, lower possibility of resistance and low cytotoxicity. However, the physicochemical properties of photosensitizers and the biological barrier of oral biofilm have limited the efficiency of aPDT. Nanomaterials has been used to fabricate nanocarriers to improve photosensitizer properties and thus enhance antimicrobial effect. In this review, we have discussed the challenges of aPDT used in dentistry, categorized the nanomaterial-delivery system and listed the possible mechanisms involved in nanomaterials when enhancing aPDT effect.

How to study biofilms: technological advancements in clinical biofilm research

Biofilm formation is an important survival strategy commonly used by bacteria and fungi, which are embedded in a protective extracellular matrix of organic polymers. They are ubiquitous in nature, including humans and other animals, and they can be surface- and non-surface-associated, making them capable of growing in and on many different parts of the body. Biofilms are also complex, forming polymicrobial communities that are difficult to eradicate due to their unique growth dynamics, and clinical infections associated with biofilms are a huge burden in the healthcare setting, as they are often difficult to diagnose and to treat. Our understanding of biofilm formation and development is a fast-paced and important research focus. This review aims to describe the advancements in clinical biofilm research, including both in vitro and in vivo biofilm models, imaging techniques and techniques to analyse the biological functions of the biofilm.

Mechanism Insights of Antibacterial Surfaces Coated with Dead Probiotics

To understand the antimicrobial effect of surfaces fabricated with dead probiotics, we prepared surfaces decorated with dead probiotics Lactobacillus rhamnosus GG (LGG) with varied inactivation methods and explored their inhibitory interactions with Pseudomonas aeruginosa (PAO1). By combining several techniques, i.e., digital holographic microscopy (DHM), atomic force microscopy (AFM), RNA sequencing, and metabolomic analysis, we studied the three-dimensional (3D) swimming behaviors, surface adhesion, biofilm formation, and adaptive responses of PAO1 near such surfaces. The results show that planktonic PAO1 decreases their flick and reverse motions by downregulating the chemotaxis pathway and accelerates with less accumulation near dead LGG surfaces by upregulating the flagellar assembly pathway and decreasing cyclic adenosine monophosphate. Distinct from live siblings, the surfaces decorated with dead LGG show a significant reduction in adhesion strength with PAO1 and inhibit biofilm formation with more downregulated genes in the Pseudomonas quinolone signal and biofilm formation pathway. We demonstrate that the antibacterial ability of such surfaces stems from the gradually released lysate from the dead LGG that is unfavorable to PAO1 in close proximity. The releasing rate and order depend on the cell membrane integrity, which closely relates to the inactivation methods.

The consistent application of hydrogen peroxide controls biofilm growth and removes Vermamoeba vermiformis from multi-kingdom in-vitro dental unit water biofilms

The water systems inside a dental unit are known to be contaminated with a multi-kingdom biofilm encompassing bacteria, fungi, viruses and protozoa. Aerosolization of these micro-organisms can potentially create a health hazard for both dental staff and the patient. Very little is known on the efficacy of dental unit disinfection products against amoeba. In this study we have examined the effect of four different treatment regimens, with the hydrogen peroxide (H₂O₂) containing product Oxygenal, on an in-vitro multi-kingdom dental unit water system (DUWS) biofilm. The treatment efficacy was assessed in time using heterotrophic plate counts, the bacterial 16S rDNA, fungal 18S rDNA gene load and the number of genomic units for Legionella spp. the amoeba Vermamoeba vermiformis. The results indicated that a daily treatment of the DUWS with a low dose H₂O₂ (0.02% for 5 h), combined with a weekly shock dose (0.25% H₂O₂, 30 min) is necessary to reduce the heterotrophic plate count of a severely contaminated DUWS (>10⁶ CFU.mL^-1) to below 100 CFU.mL^-1. A daily treatment with a low dose hydrogen peroxide alone, is sufficient for the statistically significant reduction of the total amount of bacterial 16S rDNA gene, Legionella spp. and Vermamoeba vermiformis load (p < 0.005). Also shown is that even though hydrogen peroxide does not kill the trophozoite nor the cysts of V. vermiformis, it does however result in the detachment of the trophozoite form of this amoeba from the DUWS biofilm and hereby ultimately removing the amoeba from the system.

Long-term antibacterial activity of silver-containing hydroxyapatite coatings against Staphylococcus aureus in vitro and invivo

BACKGROUND

The potential of silver-containing hydroxyapatite (Ag-HA) coatings to prevent orthopaedic implant-associated infection was explored previously; however, the resistance of Ag-HA coatings to late-onset orthopaedic infections is unknown. This study aimed to evaluate the long-term Ag+ elution and antibacterial properties of the Ag-HA coatings through in vitro and in vivo experiments.

METHODS

Ag-HA-coated disc specimens were immersed in fetal bovine serum (FBS) for six months. Ag concentration was measured over time using inductively coupled plasma-mass spectrometry to evaluate Ag release. The hydroxyapatite (HA)- or Ag-HA-coated disc specimens were immersed in FBS for 3 months to elute Ag+ for in vitro experiments. Methicillin-resistant Staphylococcus aureus (MRSA) suspensions were inoculated onto each disc; after 48 h, the number of colonies and the biofilm volume were measured. HA- or Ag-HA-coated disc specimens were inserted under the skin of Sprague-Dawley rats for three months for in vivo experiments. In in vivo experiment 1, specimens were inoculated with MRSA and the number of colonies was counted after 48 h. In in vivo experiment 2, the specimens were inoculated with bioluminescent S. aureus Xen36 cells, and bioluminescence was measured using an in vivo imaging system.

RESULTS

The Ag-HA-coated disc specimens continued to elute Ag+ after six months. The biofilm volume in the Ag-HA group was lower than in the HA group. In in vitro and in vivo experiment 1, the bacterial counts in the Ag-HA group were lower than those in the HA group. In in vivo experiment 2, the bioluminescence in the Ag-HA group was lower than that in the HA group on days 1-7 after inoculation.

CONCLUSIONS

The Ag-HA-coated discs continued to elute Ag+ for a long period and exhibited antibacterial activity and inhibition of biofilm formation against S. aureus. The Ag-HA coatings have the potential to reduce late-onset orthopaedic implant-associated infections.

The role of bacterial corrosion on recolonization of titanium implant surfaces: An in vitro study

BACKGROUND

Inflammation triggered by bacterial biofilms in the surrounding tissue is a major etiological factor for peri-implantitis and subsequent implant failure. However, little is known about the direct effects of bacterial corrosion and recolonization on implant failure PURPOSE: To investigate the influence of oral commensals on bacterial corrosion and recolonization of titanium surfaces.

MATERIALS AND METHODS

Streptococcus sanguinis (S. sanguinis) and Porphyromonas gingivalis (P. gingivalis), which are key bacteria in oral biofilm formation, were cultured on commercially pure titanium and titanium-aluminum-vanadium (Ti6Al4V) plates in artificial saliva/brain heart infusion medium under aerobic or anaerobic conditions. Biofilm formation was examined after 7 and 21 days by crystal violet and live/dead staining. Titanium ions released into culture supernatants were analyzed over a period of 21 days by atomic absorption spectrometry. Visual changes in surface morphology were investigated using scanning electron microscopy. Biofilm formation on sterilized, biocorroded, and recolonized implant surfaces was determined by crystal violet staining.

RESULTS

S. sanguinis and P. gingivalis formed stable biofilms on the titanium samples. Bacterial corrosion led to a significant increase in titanium ion release from these titanium plates (p < 0.01), which was significantly higher under aerobic conditions on pure titanium (p ≤ 0.001). No obvious morphological surface changes, such as pitting and discoloration, were detected in the titanium samples. During early biofilm formation, the addition of titanium ions significantly decreased the number of live cells. In contrast, a significant effect on biofilm mass was only detected with P. gingivalis. Bacterial corrosion had no influence on bacterial recolonization following sterilization of titanium and Ti6Al4V surfaces.

CONCLUSION

Bacterial corrosion differs between oral commensal bacteria and leads to increased titanium ion release from titanium plates. The titanium ion release did not influence biofilm formation or bacterial recolonization under in vitro conditions.

Advances in the Sensing and Treatment of Wound Biofilms

Wound biofilms represent a particularly challenging problem in modern medicine. They are increasingly antibiotic resistant and can prevent the healing of chronic wounds. However, current treatment and diagnostic options are hampered by the complexity of the biofilm environment. In this review, we present new chemical avenues in biofilm sensors and new materials to treat wound biofilms, offering promise for better detection, chemical specificity, and biocompatibility. We briefly discuss existing methods for biofilm detection and focus on novel, sensor-based approaches that show promise for early, accurate detection of biofilm formation on wound sites and that can be translated to point-of-care settings. We then discuss technologies inspired by new materials for efficient biofilm eradication. We focus on ultrasound-induced microbubbles and nanomaterials that can both penetrate the biofilm and simultaneously carry active antimicrobials and discuss the benefits of those approaches in comparison to conventional methods.

Engineered Nanotechnology: An Effective Therapeutic Platform for the Chronic Cutaneous Wound

The healing of chronic wound infections, especially cutaneous wounds, involves a complex cascade of events demanding mutual interaction between immunity and other natural host processes. Wound infections are caused by the consortia of microbial species that keep on proliferating and produce various types of virulence factors that cause the development of chronic infections. The mono- or polymicrobial nature of surface wound infections is best characterized by its ability to form biofilm that renders antimicrobial resistance to commonly administered drugs due to poor biofilm matrix permeability. With an increasing incidence of chronic wound biofilm infections, there is an urgent need for non-conventional antimicrobial approaches, such as developing nanomaterials that have intrinsic antimicrobial-antibiofilm properties modulating the biochemical or biophysical parameters in the wound microenvironment in order to cause disruption and removal of biofilms, such as designing nanomaterials as efficient drug-delivery vehicles carrying antibiotics, bioactive compounds, growth factor antioxidants or stem cells reaching the infection sites and having a distinct mechanism of action in comparison to antibiotics—functionalized nanoparticles (NPs) for better incursion through the biofilm matrix. NPs are thought to act by modulating the microbial colonization and biofilm formation in wounds due to their differential particle size, shape, surface charge and composition through alterations in bacterial cell membrane composition, as well as their conductivity, loss of respiratory activity, generation of reactive oxygen species (ROS), nitrosation of cysteines of proteins, lipid peroxidation, DNA unwinding and modulation of metabolic pathways. For the treatment of chronic wounds, extensive research is ongoing to explore a variety of nanoplatforms, including metallic and nonmetallic NPs, nanofibers and self-accumulating nanocarriers. As the use of the magnetic nanoparticle (MNP)-entrenched pre-designed hydrogel sheet (MPS) is found to enhance wound healing, the bio-nanocomposites consisting of bacterial cellulose and magnetic nanoparticles (magnetite) are now successfully used for the healing of chronic wounds. With the objective of precise targeting, some kinds of “intelligent” nanoparticles are constructed to react according to the required environment, which are later incorporated in the dressings, so that the wound can be treated with nano-impregnated dressing material in situ. For the effective healing of skin wounds, high-expressing, transiently modified stem cells, controlled by nano 3D architectures, have been developed to encourage angiogenesis and tissue regeneration. In order to overcome the challenge of time and dose constraints during drug administration, the approach of combinatorial nano therapy is adopted, whereby AI will help to exploit the full potential of nanomedicine to treat chronic wounds.

A novel dressing with silver to treat meticillin-resistant Staphylococcus aureus biofilm infection in a pig model

OBJECTIVE

The purpose of this study was to use an in vivo biofilm porcine model to examine a new polyvinyl alcohol-based gelling fibre dressing with silver and compare it to other commercial dressings containing: polyvinyl alcohol-based gelling fibre without silver; carboxymethyl cellulose-based fibre with silver, benzethonium chloride and ethylenediaminetetraacetic acid; and untreated control.

METHODS

A total of 52 deep partial-thickness wounds (10x7x0.5mm) were created on each of three animals and inoculated with 25µl of meticillin-resistant Staphylococcus aureus (MRSA) (10⁶ colony forming units (CFU)/ml). Wounds were covered for 24 hours to allow biofilm formation and were randomly designated to one of the four treatments. Samples were recovered for microbiological and histological analysis on days 3, 5 and 7 post-treatment.

RESULTS

Polyvinyl alcohol-based gelling fibre dressing with silver was able to significantly reduce biofilm more effectively than the other treatment groups. By day 7, wounds treated with the dressing had a 2.72±0.01 log CFU/g reduction in MRSA count versus untreated control wounds and a 2.59±0.01 log CFU/g reduction versus baseline counts. For histology analysis, all wounds reached 100% re-epithelialisation by day 5.

CONCLUSION

The results of this study indicated that polyvinyl alcohol-based gelling fibre dressing with silver was effective against biofilm of antibiotic-resistant staphylococcal strains without inhibiting the wound healing process, and may have important clinical implications when treating acute and/or hard-to-heal wounds.

Advances in the Sensing and Treatment of Wound Biofilms

Wound biofilms represent a particularly challenging problem in modern medicine. They are increasingly antibiotic resistant and can prevent the healing of chronic wounds. However, current treatment and diagnostic options are hampered by the complexity of the biofilm environment. In this review, we present new chemical avenues in biofilm sensors and new materials to treat wound biofilms, offering promise for better detection, chemical specificity, and biocompatibility. We briefly discuss existing methods for biofilm detection and focus on novel, sensor‐based approaches that show promise for early, accurate detection of biofilm formation on wound sites and that can be translated to point‐of‐care settings. We then discuss technologies inspired by new materials for efficient biofilm eradication. We focus on ultrasound‐induced microbubbles and nanomaterials that can both penetrate the biofilm and simultaneously carry active antimicrobials and discuss the benefits of those approaches in comparison to conventional methods.

Preparation and characterization of chitosan/graphene oxide nanocomposite coatings on Mg-2 wt% Zn scaffold by pulse electrodeposition process

Mg and its alloys are biodegradable and mechanically strong materials, which can be used for an orthopedic implant and device applications, but corrosion rate of these alloys is high. In this research, the nanocomposite coatings of chitosan (CS)/graphene oxide (GO) were fabricated to improve the corrosion resistance of the Mg-2 wt% Zn scaffold. The contents of the GO nanosheets and the pulse electrodeposition process parameters, including peak current density (CD) and duty cycle (DC), will also be investigated. The Mg-2 wt% Zn as a substrate of the scaffold was prepared using a powder metallurgy process. The influence of the porosity was studied on the microstructure fabricated scaffolds. The coating microstructures and morphologies were investigated by Raman spectroscopy, x-ray diffraction, thermogravimetric analysis, and SEM. The atomic force microscopy was performed to study the thickness of the nanocomposite coatings. The zeta potential measurement was conducted for the dispersion of the GO nanosheets in the CS matrix. The obtained results showed that the optimum conditions to fabricate a uniform CS/GO coating on the scaffolds were 2 wt% GO, CD = 20 mA cm^-2, and DC = 0.5. The pH, time and temperature for the fabrication of the coatings were conducted at 5, 20 min, and 37 °C, respectively. Additionally, the potentiodynamic polarization measurement in simulated body fluid indicated that the CS/GO coatings could provide effective protection of the scaffolds against corrosion. Additionally, the optimum sample obtained from the aspect of the corrosion behavior demonstrated adequate biocompatibility with proper adhesion of mouse fibroblast cells (L929) on the CS-2 wt% GO coating.

In vitro testing of silver-containing spacer in periprosthetic infection management

Deep infection is a serious complication in endoprosthetic surgery. In correlation to the patient local or systemic compromising factors conservative and surgical proceedings has to be evaluated. Systemic antibiotic therapy is the gold standard in infection management. Implanted silver-coated or silver-containing medical devices have been proven to their antimicrobial effectiveness since the 1990s by several investigators. The outcomes showed that long time implantation could cause damaging of the surrounding tissues, especially of adjacent nerves. The aim of our study was to evaluate the release of silver (I) ions from bone cement mixed with either nanosilver particles (AgNPs), different concentrations of silver sulfate (Ag2SO4) or from pure metallic silver strips. Therefore, we choose two methods: the first, called “static model”, was chosen to evaluate the maximal accumulative concentration of silver (I) ions, with the second, called “dynamic model”, we simulated a continuous reduction of the ions. In an additional test design, the different materials were evaluated for their antimicrobial activity using an agar gel diffusion assay. The outcome showed that neither the addition of 1% (w/w) nanosilver nor 0.1% silver sulfate (w/w) to polymethylmethacrylat bone cement has the ability to release silver (I) ions in a bactericidal/antifungal concentration. However, the results also showed that the addition of 0.5% (w/w) and 1% (w/w) silver sulfate (Ag2SO4) to bone cement is an effective amount of silver for use as a temporary spacer.

Au Nanoclusters Ameliorate Shigella Infectious Colitis by Inducing Oxidative Stress

Background

Shigella infection has always been a global burden, and it particularly threatens children between the ages of 1 and 5 years. Economically underdeveloped countries are dominated by Shigella flexneri infection. The most effective method to treat Shigella is antibiotics, but with the abuse of antibiotics and the prevalence of multidrug resistance, we urgently need a relatively safe non-antibiotic treatment to replace it. Ultrasmall Au nanoclusters (NCs) have special physical and chemical properties and can better interact with and be internalized by bacteria to disrupt the metabolic balance. The purpose of this study was to explore whether Au NCs may be a substitute for antibiotics to treat Shigella infections.

Methods

Au NCs and Shigella Sf301, R2448, and RII-1 were cocultured in vitro to evaluate the bactericidal ability of Au NCs. The degree of damage and mode of action of Au NCs in Shigella were clearly observed in images of scanning electron microscopy (SEM). In vivo experiments were conducted to observe the changes in body weight, clinical disease activity index (DAI) and colon (including length and histopathological sections) of mice treated with Au NCs. The effect of Au NCs was analysed by measuring the content of lipocalin-2 (LCN2) and Shigella in faeces. Next, the changes in Shigella biofilm activity, the release of reactive oxygen species (ROS), the changes in metabolism-related and membrane-related genes, and the effect of Au NCs on the body weight of mice were determined to further analyse the mechanism of action and effect.

Results

Au NCs (100 μM) interfered with oxidative metabolism genes, induced a substantial increase in ROS levels, interacted with the cell membrane to destroy it, significantly killed Shigella, and effectively alleviated the intestinal damage caused by Shigella in mice. The activity of the biofilm formed by Shigella was reduced.

Conclusion

The effective antibacterial effect and good safety suggest that Au NCs represent a good potential alternative to antibiotics to treat Shigella infections.

Formulation of inherently antimicrobial magnesium oxychloride cement and the effect of supplementation with silver phosphate

The growing threat of bacterial resistance to antibiotics is driving an increasing need for new antimicrobial strategies. This work demonstrates the potential of magnesium oxychloride cements (MOC) to be used as inorganic antimicrobial biomaterials for bone augmentation. An injectable formulation was identified at a powder to liquid ratio of 1.4 g mL^-1, with an initial setting time below 30 mins and compressive strength of 35 ± 9 MPa. Supplementation with Ag₃PO₄ to enhance the antimicrobial efficacy of MOC was explored, and shown via real time X-ray diffraction to retard the formation of hydrated oxychloride phases by up to 30%. The antimicrobial efficacy of MOC was demonstrated in vitro against Staphylococcus aureus and Pseudomonas aeruginosa, forming zones of inhibition and significantly reducing viability in broth culture. Enhanced efficacy was seen for silver doped formulations, with complete eradication of detectable viable colonies within 3 h, whilst retaining the cytocompatibility of MOC. Investigating the antimicrobial mode of action revealed that Mg and Ag release and elevated pH contributed to MOC efficacy. Sustained silver release was demonstrated over 14 days, suggesting the Ag₃PO₄ modified formulation offers two mechanisms of infection treatment, combining the inherent antimicrobial properties of MOC with controlled release of inorganic antimicrobials.

Update on the role of antiseptics in the management of chronic wounds with critical colonisation and/or biofilm

Biofilms play a major role in delaying chronic wounds from healing. A wound infiltrated with biofilm, or "critically colonised" wound, may become clinically infected if the number of microbes exceeds a critical level. Chronic wound biofilms represent a significant treatment challenge by demonstrating recalcitrance towards antimicrobial agents. However, a "window of opportunity" may exist after wound debridement when biofilms are more susceptible to topical antiseptics. Here, we discuss the role of antiseptics in the management of chronic wounds and biofilm, focusing on povidone-iodine (PVP-I) in comparison with two commonly used antiseptics: polyhexanide (PHMB) and silver. This article is based on the literature reviewed during a focus group meeting on antiseptics in wound care and biofilm management, and on a PubMed search conducted in March 2020. Compared with PHMB and silver, PVP-I has a broader spectrum of antimicrobial activity, potent antibiofilm efficacy, no acquired bacterial resistance or cross-resistance, low cytotoxicity, good tolerability, and an ability to promote wound healing. PVP-I represents a viable therapeutic option in wound care and biofilm management, with the potential to treat biofilm-infiltrated, critically colonised wounds. We propose a practical algorithm to guide the management of chronic, non-healing wounds due to critical colonisation or biofilm, using PVP-I.

The Effects of Silver-Releasing Foam Dressings on Diabetic Foot Ulcer Healing

Diabetic foot ulcers (DFUs) are a serious complication in diabetic patients and lead to high morbidity and mortality. Numerous dressings have been developed to facilitate wound healing of DFUs. This study investigated the wound healing efficacy of silver-releasing foam dressings versus silver-containing cream in managing outpatients with DFUs. Sixty patients with Wagner Grade 1 to 2 DFUs were recruited. The treatment group received silver-releasing foam dressing (Biatain^® Ag Non-Adhesive Foam dressing; Coloplast, Humlebaek, Denmark). The control group received 1% silver sulfadiazine (SSD) cream. The ulcer area in the silver foam group was significantly reduced compared with that in the SSD group after four weeks of treatment (silver foam group: 76.43 ± 7.41%, SSD group: 27.00 ± 4.95%, p < 0.001). The weekly wound healing rate in the silver foam group was superior to the SSD group during the first three weeks of treatment (p < 0.05). The silver-releasing foam dressing is more effective than SSD in promoting wound healing of DFUs. The effect is more pronounced in the initial three weeks of the treatment. Thus, silver-releasing foam could be an effective wound dressing for DFUs, mainly in the early period of wound management.

Local wound management factors related to biofilm reduction in the pressure ulcer: A prospective observational study

AIMS

Critical colonization in pressure ulcers delays healing and has been studied. However, local wound management includes no clear strategy for preventing the development of biofilms. Therefore, this multicenter, prospective, observational study was conducted to examine the effect of local management on the biofilm area of pressure ulcers with critical colonization.

METHODS

Participants were 34 patients with a pressure ulcer deeper than the dermis and in a state of critical colonization. The primary outcome was the change over a week in the proportion of the biofilm area in relation to that of the pressure ulcer area. We investigated the relationship between primary outcome and local wound management. The wound-blotting method was used for determining the biofilm area. To calculate the change in the biofilm area, baseline proportion was subtracted from proportion 1 week later.

RESULTS

Six types of topical treatment were used in three facilities. The proportion of the biofilm area at 1 week follow-up was significantly smaller with iodine ointment than that without iodine ointment (p = .02). The standardized partial regression coefficient of iodine ointment adjusted by the type of medical facility was -0.26 (p = .003).

CONCLUSION

This study revealed that the use of iodine ointment reduced the proportion of the biofilm area in the pressure ulcer surface. To manage pressure ulcers in a state of critical colonization, these results suggest that local management include the use of iodine ointment.

The combination of silver-containing hydroxyapatite coating and vancomycin has a synergistic antibacterial effect on methicillin-resistant Staphylococcus aureus biofilm formation

Aims

Biofilm formation is intrinsic to prosthetic joint infection (PJI). In the current study, we evaluated the effects of silver-containing hydroxyapatite (Ag-HA) coating and vancomycin (VCM) on methicillin-resistant Staphylococcus aureus (MRSA) biofilm formation.

Methods

Pure titanium discs (Ti discs), Ti discs coated with HA (HA discs), and 3% Ag-HA discs developed using a thermal spraying were inoculated with MRSA suspensions containing a mean in vitro 4.3 (SD 0.8) x 10⁶ or 43.0 (SD 8.4) x 10⁵ colony-forming units (CFUs). Immediately after MRSA inoculation, sterile phosphate-buffered saline or VCM (20 µg/ml) was added, and the discs were incubated for 24 hours at 37°C. Viable cell counting, 3D confocal laser scanning microscopy with Airyscan, and scanning electron microscopy were then performed. HA discs and Ag HA discs were implanted subcutaneously in vivo in the dorsum of rats, and MRSA suspensions containing a mean in vivo 7.2 (SD 0.4) x 10⁶  or 72.0 (SD 4.2) x 10⁵  CFUs were inoculated on the discs. VCM was injected subcutaneously daily every 12 hours followed by viable cell counting.

Results

Biofilms that formed on HA discs were thicker and larger than those on Ti discs, whereas those on Ag-HA discs were thinner and smaller than those on Ti discs. Viable bacterial counts in vivo revealed that Ag-HA combined with VCM was the most effective treatment.

Conclusion

Ag-HA with VCM has a potential synergistic effect in reducing MRSA biofilm formation and can thus be useful for preventing and treating PJI.

Cite this article:Bone Joint Res. 2020;9(5):211–218.

Comparison of sonication with chemical biofilm dislodgement methods using chelating and reducing agents: Implications for the microbiological diagnosis of implant associated infection

The diagnosis of implant-associated infections is hampered due to microbial adherence and biofilm formation on the implant surface. Sonication of explanted devices was shown to improve the microbiological diagnosis by physical removal of biofilms. Recently, chemical agents have been investigated for biofilm dislodgement such as the chelating agent ethylenediaminetetraacetic acid (EDTA) and the reducing agent dithiothreitol (DTT). We compared the activity of chemical methods for biofilm dislodgement to sonication in an established in vitro model of artificial biofilm. Biofilm-producing laboratory strains of Staphylococcus epidermidis (ATCC 35984), S. aureus (ATCC 43300), E. coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 53278) were used. After 3 days of biofilm formation, porous glass beads were exposed to control (0.9% NaCl), sonication or chemical agents. Quantitative and qualitative biofilm analyses were performed by colony counting, isothermal microcalorimetry and scanning electron microscopy. Recovered colony counts after treatment with EDTA and DTT were similar to those after exposure to 0.9% NaCl for biofilms of S. epidermidis (6.3 and 6.1 vs. 6.0 log10 CFU/mL, S. aureus (6.4 and 6.3 vs. 6.3 log10 CFU/mL), E. coli (5.2 and 5.1 vs. 5.1 log10 CFU/mL and P. aeruginosa (5.1 and 5.2 vs. 5.0 log10 CFU/mL, respectively). In contrast, with sonication higher CFU counts were detected with all tested microorganisms (7.5, 7.3, 6.2 and 6.5 log10 CFU/mL, respectively) (p <0.05). Concordant results were observed with isothermal microcalorimetry and scanning electron microscopy. In conclusion, sonication is superior to both tested chemical methods (EDTA and DTT) for dislodgement of S. epidermidis, S. aureus, E. coli and P. aeruginosa biofilms. Future studies may evaluate potential additive effect of chemical dislodgement to sonication.

Nanoparticles for the Treatment of Oral Biofilms: Current State, Mechanisms, Influencing Factors, and Prospects

Due to their excellent size, designability, and outstanding targeted antibacterial effects, nanoparticles have become a potential option for controlling oral biofilm-related infections. However, the formation of an oral biofilm is a dynamic process, and factors affecting the performance of antibiofilm treatments are complex. As such, when examining the existing literature on the antibiofilm effects of nanoparticles, attention should be paid to the specific mechanisms of action at different stages of oral biofilm formation, as well as relevant influencing factors, in order to achieve an objective and comprehensive evaluation. This review is intended to detail the antibacterial mechanisms of nanoparticles during the four stages of the formation of oral biofilms: 1) acquired film formation; 2) bacterial adhesion; 3) early biofilm development; and 4) biofilm maturation. In addition, factors influencing the antibiofilm properties of nanoparticles are summarized from the aspects of nanoparticles themselves, biofilm models, and host factors. The limitations of current research and possible trends for future research are also discussed. In summary, nanoparticles are a promising antioral biofilm strategy. It is hoped that this review can serve as a reference and inspire ideas for further research on the application of nanoparticles for effectively targeting and treating oral biofilms.

Efficacy of Poloxamer-Based Wound Dressings on Acinetobacter baumanni Biofilms

Objective: This study evaluated the antimicrobial and antibiofilm activity of a concentrated surfactant gel preserved with antimicrobials and a concentrated surfactant gel with 1% silver sulfadiazine (SSD) against 12 clinical strains of Acinetobacter baumannii and the type strain A. baumannii ATCC 19606. Approach: The biofilm-forming potential of the A. baumannii isolates was investigated using a crystal violet assay and classifying the isolates as "non-adherent," "weak," "moderate," or "strong" biofilm formers. The antimicrobial activity was determined using the zone of inhibition (ZOI) method. The antibiofilm activity was evaluated against A. baumannii ATCC 19606 using the Center for Disease Control bioreactor model. Results: A. baumannii readily forms biofilms with 8 out of the 12 clinical isolates being classified as strong biofilm formers (OD₅₇₀ > 0.4). The concentrated surfactant gel with 1% SSD demonstrated antimicrobial activity against all isolates with a ZOI of 7.2-14 mm. Antibiofilm activity against a 24 h biofilm of A. baumannii ATCC 19606 was found, with a ≥7 log decrease in bacterial cell density following 24 h treatment with the concentrated surfactant gel with 1% SSD. The concentrated surfactant gel preserved with antimicrobials also showed some biofilm disruption with ∼3 log decrease in bacterial cell density being found. Innovation: The concentrated surfactant gel with 1% SSD used in this study showed antimicrobial and antibiofilm activity against A. baumannii. Conclusion: The concentrated surfactant gel with 1% SSD used in this study showed efficacy against A. baumannii, a common cause of wound infections, and should be considered for treatment of wounds infected with A. baumannii in health care settings.

Responsive Assembly of Silver Nanoclusters with a Biofilm Locally Amplified Bactericidal Effect to Enhance Treatments against Multi-Drug-Resistant Bacterial Infections

Bacterial biofilms pose a major threat to public health because they are resistant to most current therapeutics. Conventional antibiotics exhibit limited penetration and weakened activity in the acidic microenvironment of a biofilm. Here, the development of biofilm-responsive nanoantibiotics (rAgNAs) composed of self-assembled silver nanoclusters and pH-sensitive charge reversal ligands, whose bactericidal activity can be selectively boosted in the biofilm microenvironment, is reported. Under neutral physiological conditions, the bactericidal activity of rAgNAs is self-quenched because the toxic silver ions' release is largely inhibited; however, upon entry into the acidic biofilm microenvironment, the rAgNAs not only exhibit charge reversal to facilitate local accumulation and retention but also disassemble into small silver nanoclusters, thus enabling deep penetration and accelerated silver ions release for dramatically amplified bactericidal activity. The superior antibiofilm activity of rAgNAs is demonstrated both in vitro and in vivo, and the mortality rate of mice with multi-drug-resistant biofilm-induced severe pyomyositis can be significantly reduced by rAgNAs treatment, indicating the immense potential of rAgNAs as highly efficient nanoscale antibacterial agents to combat resistant bacterial biofilm-associated infections.

Polymeric Composites with Silver (I) Cyanoximates Inhibit Biofilm Formation of Gram-Positive and Gram-Negative Bacteria

Biofilms are surface-associated microbial communities known for their increased resistance to antimicrobials and host factors. This resistance introduces a critical clinical challenge, particularly in cases associated with implants increasing the predisposition for bacterial infections. Preventing such infections requires the development of novel antimicrobials or compounds that enhance bactericidal effect of currently available antibiotics. We have synthesized and characterized twelve novel silver(I) cyanoximates designated as Ag(ACO), Ag(BCO), Ag(CCO), Ag(ECO), Ag(PiCO), Ag(PICO) (yellow and red polymorphs), Ag(BIHCO), Ag(BIMCO), Ag(BOCO), Ag(BTCO), Ag(MCO) and Ag(PiPCO). The compounds exhibit a remarkable resistance to high intensity visible light, UV radiation and heat and have poor solubility in water. All these compounds can be well incorporated into the light-curable acrylate polymeric composites that are currently used as dental fillers or adhesives of indwelling medical devices. A range of dry weight % from 0.5 to 5.0 of the compounds was tested in this study. To study the potential of these compounds in preventing planktonic and biofilm growth of bacteria, we selected two human pathogens (Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus) and Gram-positive environmental isolate Bacillus aryabhattai. Both planktonic and biofilm growth was abolished completely in the presence of 0.5% to 5% of the compounds. The most efficient inhibition was shown by Ag(PiCO), Ag(BIHCO) and Ag(BTCO). The inhibition of biofilm growth by Ag(PiCO)-yellow was confirmed by scanning electron microscopy (SEM). Application of Ag(BTCO) and Ag(PiCO)-red in combination with tobramycin, the antibiotic commonly used to treat P. aeruginosa infections, showed a significant synergistic effect. Finally, the inhibitory effect lasted for at least 120 h in P. aeruginosa and 36 h in S. aureus and B. aryabhattai. Overall, several silver(I) cyanoximates complexes efficiently prevent biofilm development of both Gram-negative and Gram-positive bacteria and present a particularly significant potential for applications against P. aeruginosa infections.

Recent Advances in Non-Conventional Antimicrobial Approaches for Chronic Wound Biofilms: Have We Found the 'Chink in the Armor'?

Chronic wounds are a major healthcare burden, with huge public health and economic impact. Microbial infections are the single most important cause of chronic, non-healing wounds. Chronic wound infections typically form biofilms, which are notoriously recalcitrant to conventional antibiotics. This prompts the need for alternative or adjunct ‘anti-biofilm’ approaches, notably those that account for the unique chronic wound biofilm microenvironment. In this review, we discuss the recent advances in non-conventional antimicrobial approaches for chronic wound biofilms, looking beyond standard antibiotic therapies. These non-conventional strategies are discussed under three groups. The first group focuses on treatment approaches that directly kill or inhibit microbes in chronic wound biofilms, using mechanisms or delivery strategies distinct from antibiotics. The second group discusses antimicrobial approaches that modify the biological, chemical or biophysical parameters in the chronic wound microenvironment, which in turn enables the disruption and removal of biofilms. Finally, therapeutic approaches that affect both, biofilm bacteria and microenvironment factors, are discussed. Understanding the advantages and limitations of these recent approaches, their stage of development and role in biofilm management, could lead to new treatment paradigms for chronic wound infections. Towards this end, we discuss the possibility that non-conventional antimicrobial therapeutics and targets could expose the ‘chink in the armor’ of chronic wound biofilms, thereby providing much-needed alternative or adjunct strategies for wound infection management.

Silver, biofilms and wounds: resistance revisited

Silver is added to an array of commercially available healthcare products including wound dressings. However, overuse of silver is being raised as a potential health concern due to the possible selection of tolerant or resistant bacteria and as a factor that may induce cross resistance to antibiotics. To date, there are only a limited number of studies that have documented evidence of silver resistance in bacteria isolated from medical situations. These studies have indicated low levels of silver resistance in bacteria. However, in comparison to antibiotics, only a small number of studies have been undertaken to investigate silver resistance. It is clear that more studies are required to confirm the most effective therapeutic levels of silver that are needed to kill microbes. In addition, it is probable that sub-therapeutic levels of silver may potentially select for enhanced microbial tolerance. Nevertheless, to date, there still remains very little evidence that silver resistance is a growing health concern in wound care; more studies are clearly needed to substantiate this concern, which has not been observed clinically to any major degree. The issue of biofilm tolerance to silver is more complicated and data on the effect of silver on biofilms is sparse at present.

Stability of Antibacterial Silver Carboxylate Complexes against Staphylococcus epidermidis and Their Cytotoxic Effects

The antibacterial effects against Staphylococcus epidermidis of five silver carboxylate complexes with anti-inflammatory ligands were studied in order to analyze and compare them in terms of stability (in solution and after exposure to UV light), and their antibacterial and morphological differences. Four effects of the Ag-complexes were evidenced by transmission electronic microscopy (TEM) and scanning electronic microscopy (SEM): DNA condensation, membrane disruption, shedding of cytoplasmic material and silver compound microcrystal penetration of bacteria. 5-Chlorosalicylic acid (5Cl) and sodium 4-aminosalicylate (4A) were the most effective ligands for synthesizing silver complexes with high levels of antibacterial activity. However, Ag-5Cl was the most stable against exposure UV light (365 nm). Cytotoxic effects were tested against two kinds of eukaryotic cells: murine fibroblast cells (T10 1/2) and human epithelial ovarian cancer cells (A2780). The main objective was to identify changes in their antibacterial properties associated with potential decomposition and the implications for clinical applications.

Potential of antimicrobial treatment of linear low-density polyethylene with poly((tert-butyl-amino)-methyl-styrene) to reduce biofilm formation in the food industry

Antimicrobial surfaces are one approach to prevent biofilms in the food industry. The aim of this study was to investigate the effect of poly((tert-butyl-amino)-methyl-styrene) (poly(TBAMS)) incorporated into linear low-density polyethylene (LLDPE) on the formation of mono- and mixed-species biofilms. The biofilm on untreated and treated LLDPE was determined after 48 and 168 h. The comparison of the results indicated that the ability of Listeria monocytogenes to form biofilms was completely suppressed by poly(TBAMS) (Δ_168 h 3.2 log₁₀ cfu cm^-2) and colonization of Staphylococcus aureus and Escherichia coli was significantly delayed, but no effect on Pseudomonas fluorescens was observed. The results of dual-species biofilms showed complex interactions between the microorganisms, but comparable effects on the individual bacteria by poly(TBAMS) were identified. Antimicrobial treatment with poly(TBAMS) shows great potential to prevent biofilms on polymeric surfaces. However, a further development of the material is necessary to reduce the colonization of strong biofilm formers.

Atividade antimicrobiana e antibiofilme de nanopartículas de prata sobre isolados de Aeromonas spp. obtidos de organismos aquáticos

RESUMO: O uso indiscriminado de antimicrobianos tem proporcionado a algumas bactérias patogênicas a seleção de cepas multirresistentes, situação que pode ser agravada pela formação do biofilme. Desta forma, as nanopartículas de prata (AgNPs) vêm se destacando como uma alternativa inovadora, de baixo custo e eficiente contra doenças causadas por bactérias. O objetivo deste estudo foi determinar a atividade antimicrobiana das AgNPs e a interferência na formação do biofilme de Aeromonas spp. obtidas de organismos aquáticos. As AgNPs foram sintetizadas quimicamente utilizando como agente redutor o citrato trissódico e caracterizadas por espectrofotometria ultravioleta-visível (UV-Vis). A atividade antimicrobiana foi realizada contra três isolados pelo método de microdiluição em caldo para determinar a concentração bactericida mínima (CBM) e um cultivo com CCCP, um inibidor da bomba de efluxo, foi realizado para complementar o efeito das AgNPs. A interferência no biofilme foi realizada segundo o protocolo de formação e consolidado, além da caracterização desta estrutura de resistência por microscopia eletrônica de varredura. No teste da CBM, as AgNPs não foram capazes de inativar o crescimento dos isolados, ao passo que o nitrato de prata obteve eficiência em diferentes concentrações. Na presença do inibidor de bomba de efluxo, dos isolados analisados, um passou de resistente a sensível na presença das nanopartículas. As AgNPs foram eficazes em diminuir a formação de biofilme, como também atuaram sobre o biofilme consolidado em todos os isolados testados. Estes resultados indicam o potencial das nanopartículas de prata em interferir com o biofilme de Aeromonas spp. de organismos aquáticos e seres humanos.

A Bacteriophage Mediated Gold Nanoparticles Synthesis and Their Anti-biofilm Activity

In the present study, gold nanoparticles (AuNPs) synthesis was carried out by using a rare bacteriophage which is morphologically similar to 7-11 phages of the C3 morphotype of tailed phage belonging to Podoviridae family as green route. Effect of various physiological parameters like pH, temperature and concentration of gold chloride salt on AuNPs synthesis was studied. The reaction mixtures have shown vivid colours at various physiological parameters. Phage inspired AuNPs were further characterized by using different techniques such as UV-Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and dynamic light scattering (DLS). DLS study revealed synthesis of various sizes of AuNPs in the range of 20-100 nm. SEM studies revealed synthesis of varied shaped AuNPs, viz., spheres, hexagons, triangles, rhomboids and rectangular etc. The presence of Au in the nanostructures was confirmed by EDS. The XRD pattern reflects the crystalline nature and nano size of AuNPs. These phage inspired AuNPs showed anti-bacterial activity against different bacterial pathogens. Anti-biofilm activity of AuNPs was evaluated on a glass slide. It was noticed that at 0.2 mM concentration of these AuNPs about 80% of biofilm formation by Pseudomonas aeruginosa, a human pathogen was inhibited. Thus, the phage inspired AuNPs synthesis could be potential therapeutic agents against human pathogens.

Sublethal concentrations of silver nanoparticles affect the mechanical stability of biofilms

Bacterial biofilms are most likely confronted with silver nanoparticles (Ag NPs) as a pollutant stressor in aquatic systems. In this study, biofilms of Aquabacterium citratiphilum were exposed for 20 h to 30 and 70 nm citrate stabilized Ag NPs in low-dose concentrations ranging from 600 to 2400 μg l^-1, and the Ag NP-mediated effects on descriptive, structural, and functional biofilm characteristics, including viability, protein content, architecture, and mechanical stability, were investigated. Viability, based on the bacterial cell membrane integrity of A. citratiphilum, as determined by epifluorescence microscopy, remained unaffected after Ag NP exposure. Moreover, in contrast to information in the current literature, protein contents of cells and extracellular polymeric substances (EPS) and biofilm architecture, including dry mass, thickness, and density, were not significantly impacted by exposure to Ag NPs. However, the biofilms themselves served as effective sinks for Ag NPs, exhibiting enrichment factors from 5 to 8. Biofilms showed a greater capacity to accumulate 30 nm sized Ag NPs than 70 nm Ag NPs. Furthermore, Ag NPs significantly threatened the mechanical stability of biofilms, as determined by a newly developed assay. For 30 nm Ag NPs, the mechanical stability of biofilms decreased as the Ag NP concentrations applied to them increased. In contrast, 70 nm Ag NPs produced a similar decrease in mechanical stability for each applied concentration. Overall, this finding demonstrates that exposure to Ag NPs triggers remarkable changes in biofilm adhesion and/or cohesiveness. Because of biofilm-mediated ecological services, this response raises environmental concerns regarding Ag NP release into freshwater systems, even in sublethal concentrations.

Mechanistic understanding of reduced AgNP phytotoxicity induced by extracellular polymeric substances

A knowledge gap concerning the potential effects of extracellular polymeric substances (EPS), a common organic material but highly variable in their composition of microbial origin, on the fate and phytotoxicity of silver nanoparticles (AgNP) still remains. A 48-h root elongation toxicity test showed that AgNP toxicity to wheat Triticum aestivum L. was dramatically alleviated by EPS isolated from Pseudomonas putida, as revealed by 7-59% increase in relative root elongation (RRE), 8-99% increase in root weight, 27-32% decrease in malondialdehyde (MDA) content and 11-43% decrease in H2O2 content compared to the treatment with AgNP in the absence of EPS. This was coincident with 7-69% decrease in root Ag concentrations. Our results showed that EPS could protect wheat seedlings from AgNP toxicity by reducing dissolved Ag concentration ([Ag]diss) and by forming AgNP-EPS complex. The FTIR spectra further showed that the amide, carboxyl, and phosphoryl functional groups of EPS were involved in binding with AgNP and/or Ag(+). All these processes worked simultaneously to reduce AgNP bioavailability, and subsequently mitigate AgNP toxicity. These findings highlight the importance of EPS in AgNP biogeochemistry in the terrestrial environment. EPS could be highly useful in developing strategies to counteract the phytotoxicty of metal-based nanoparticles in crops.

Nanoparticle-Based Therapies for Wound Biofilm Infection: Opportunities and Challenges

Clinical data from human chronic wounds implicates biofilm formation with the onset of wound chronicity. Despite the development of novel antimicrobial agents, the cost and complexity of treating chronic wound infections associated with biofilms remain a serious challenge, which necessitates the development of new and alternative approaches for effective anti-biofilm treatment. Recent advancement in nanotechnology for developing a new class of nanoparticles that exhibit unique chemical and physical properties holds promise for the treatment of biofilm infections. Over the last decade, nanoparticle-based approaches against wound biofilm infection have been directed toward developing nanoparticles with intrinsic antimicrobial properties, utilizing nanoparticles for controlled antimicrobials delivery, and applying nanoparticles for antibacterial hyperthermia therapy. In addition, a strategy to functionalize nanoparticles towards enhanced penetration through the biofilm matrix has been receiving considerable interest recently by means of achieving an efficient targeting to the bacterial cells within biofilm matrix. This review summarizes and highlights the recent development of these nanoparticle-based approaches as potential therapeutics for controlling wound biofilm infection, along with current challenges that need to be overcome for their successful clinical translation.

Understanding the fate and biological effects of Ag- and TiO₂-nanoparticles in the environment: The quest for advanced analytics and interdisciplinary concepts

Engineered inorganic nanoparticles (EINP) from consumers' products and industrial applications, especially silver and titanium dioxide nanoparticles (NP), are emitted into the aquatic and terrestrial environments in increasing amounts. However, the current knowledge on their environmental fate and biological effects is diverse and renders reliable predictions complicated. This review critically evaluates existing knowledge on colloidal aging mechanisms, biological functioning and transport of Ag NP and TiO2 NP in water and soil and it discusses challenges for concepts, experimental approaches and analytical methods in order to obtain a comprehensive understanding of the processes linking NP fate and effects. Ag NP undergo dissolution and oxidation with Ag2S as a thermodynamically determined endpoint. Nonetheless, Ag NP also undergo colloidal transformations in the nanoparticulate state and may act as carriers for other substances. Ag NP and TiO2 NP can have adverse biological effects on organisms. Whereas Ag NP reveal higher colloidal stability and mobility, the efficiency of NOM as a stabilizing agent is greater towards TiO2 NP than towards Ag NP, and multivalent cations can dominate the colloidal behavior over NOM. Many of the past analytical obstacles have been overcome just recently. Single particle ICP-MS based methods in combination with field flow fractionation techniques and hydrodynamic chromatography have the potential to fill the gaps currently hampering a comprehensive understanding of fate and effects also at a low field relevant concentrations. These analytical developments will allow for mechanistically orientated research and transfer to a larger set of EINP. This includes separating processes driven by NP specific properties and bulk chemical properties, categorization of effect-triggering pathways directing the EINP effects towards specific recipients, and identification of dominant environmental parameters triggering fate and effect of EINP in specific ecosystems (e.g. soil, lake, or riverine systems).

Silver and Alginates: Role in Wound Healing and Biofilm Control

Significance: Chronic wounds are known to be a significant issue globally. Of concern in wounds are the numbers and types of residing microorganisms and the ability of the host's immune system to control their proliferation. Wound healing is impeded by colonizing microorganisms growing within the biofilm phenotypic state. In this state microorganisms are recalcitrant to routinely impeded by used antimicrobial interventions. Recent advances: Silver has been reported to demonstrate efficacy on planktonic microorganisms both within the in vitro and in vivo environments. However, when silver is incorporated into a wound dressing, its antimicrobial efficacy on biofilms within the in vivo environment remains contentious. Critical Issues: Unequivocal evidence of the efficacy of silver, and wound dressings containing silver, on biofilms in clinical situations is lacking. This is principally due to the deficiency of definite biofilm definitions, markers, and evidence in the chronic wound environment. Future Direction: Research studies demonstrating antimicrobial efficacy on in vitro biofilms can be used to generate data and information appropriate for extrapolation and applicability to the in vivo environment. It is very important that inventors of antimicrobial wound dressings ensure efficacy against both planktonic and sessile microorganisms, within the in vitro and in vivo environments.

Inhibitory effect of silver nanoparticle fabricated urinary catheter on colonization efficiency of Coagulase Negative Staphylococci

Multiple antibiotic resistance and diverse mechanisms for biofilm formation make Coagulase Negative Staphylococci (CoNS) to cause infections associated with insertion of medical devices. As the infectious life style of CoNS pose difficult to treat conditions, materials with multitargeted antimicrobial effect can offer promising ways to modify the surface of devices to limit microbial growth. The broad spectrum of antimicrobial properties shown by silver nanoparticles (AgNPs) make it as an excellent candidate to act on device surface as persistent antimicrobial structures. In the current study, AgNPs assembled by soil bacteria under visible light at room temperature were analysed for its physical properties by UV-Vis spectroscopy, FTIR, SEM, HR-TEM and EDS and they also showed significant antimicrobial and antibiofilm properties against selected members of CoNS like Staphylococcus epidermidis and Staphylococcus haemolyticus. Very interestingly, further analysis on antibacterial mechanism of AgNPs showed their remarkable ability to cause disorganization of bacterial cell membrane. Further, surface engineering application of AgNPs on urinary catheter showed its excellent potential to prevent the attachment and colonization of CoNS which make result of study with significantly novel medical applications.

Staphylococcal biofilm formation on the surface of three different calcium phosphate bone grafts: a qualitative and quantitative in vivo analysis

Differences in physico-chemical characteristics of bone grafts to fill bone defects have been demonstrated to influence in vitro bacterial biofilm formation. Aim of the study was to investigate in vivo staphylococcal biofilm formation on different calcium phosphate bone substitutes. A foreign-body guinea-pig infection model was used. Teflon cages prefilled with β-tricalcium phosphate, calcium-deficient hydroxyapatite, or dicalcium phosphate (DCP) scaffold were implanted subcutaneously. Scaffolds were infected with 2 × 10(3) colony-forming unit of Staphylococcus aureus (two strains) or S. epidermidis and explanted after 3, 24 or 72 h of biofilm formation. Quantitative and qualitative biofilm analysis was performed by sonication followed by viable counts, and microcalorimetry, respectively. Independently of the material, S. aureus formed increasing amounts of biofilm on the surface of all scaffolds over time as determined by both methods. For S. epidermidis, the biofilm amount decreased over time, and no biofilm was detected by microcalorimetry on the DCP scaffolds after 72 h of infection. However, when using a higher S. epidermidis inoculum, increasing amounts of biofilm were formed on all scaffolds as determined by microcalorimetry. No significant variation in staphylococcal in vivo biofilm formation was observed between the different materials tested. This study highlights the importance of in vivo studies, in addition to in vitro studies, when investigating biofilm formation of bone grafts.

Multi-channel microfluidic biosensor platform applied for online monitoring and screening of biofilm formation and activity

Bacterial colonization of surfaces and interfaces has a major impact on various areas including biotechnology, medicine, food industries, and water technologies. In most of these areas biofilm development has a strong impact on hygiene situations, product quality, and process efficacies. In consequence, biofilm manipulation and prevention is a fundamental issue to avoid adverse impacts. For such scenario online, non-destructive biofilm monitoring systems become important in many technical and industrial applications. This study reports such a system in form of a microfluidic sensor platform based on the combination of electrical impedance spectroscopy and amperometric current measurement, which allows sensitive online measurement of biofilm formation and activity. A total number of 12 parallel fluidic channels enable real-time online screening of various biofilms formed by different Pseudomonas aeruginosa and Stenotrophomonas maltophilia strains and complex mixed population biofilms. Experiments using disinfectant and antibiofilm reagents demonstrate that the biofilm sensor is able to discriminate between inactivation/killing of bacteria and destabilization of biofilm structures. The impedance and amperometric sensor data demonstrated the high dynamics of biofilms as a consequence of distinct responses to chemical treatment strategies. Gene expression of flagellar and fimbrial genes of biofilms grown inside the microfluidic system supported the detected biofilm growth kinetics. Thus, the presented biosensor platform is a qualified tool for assessing biofilm formation in specific environments and for evaluating the effectiveness of antibiofilm treatment strategies.

Thermoresponsive antimicrobial wound dressings via simultaneous thiol-ene polymerization and in situ generation of silver nanoparticles

Thermoresponsive and antimicrobial wound dressing via thiol-ene polymerization reaction.

Evidence-based nanoscopic and molecular framework for excipient functionality in compressed orally disintegrating tablets

The work investigates the adhesive/cohesive molecular and physical interactions together with nanoscopic features of commonly used orally disintegrating tablet (ODT) excipients microcrystalline cellulose (MCC) and D-mannitol. This helps to elucidate the underlying physico-chemical and mechanical mechanisms responsible for powder densification and optimum product functionality. Atomic force microscopy (AFM) contact mode analysis was performed to measure nano-adhesion forces and surface energies between excipient-drug particles (6-10 different particles per each pair). Moreover, surface topography images (100 nm2-10 µm2) and roughness data were acquired from AFM tapping mode. AFM data were related to ODT macro/microscopic properties obtained from SEM, FTIR, XRD, thermal analysis using DSC and TGA, disintegration testing, Heckel and tabletability profiles. The study results showed a good association between the adhesive molecular and physical forces of paired particles and the resultant densification mechanisms responsible for mechanical strength of tablets. MCC micro roughness was 3 times that of D-mannitol which explains the high hardness of MCC ODTs due to mechanical interlocking. Hydrogen bonding between MCC particles could not be established from both AFM and FTIR solid state investigation. On the contrary, D-mannitol produced fragile ODTs due to fragmentation of surface crystallites during compression attained from its weak crystal structure. Furthermore, AFM analysis has shown the presence of extensive micro fibril structures inhabiting nano pores which further supports the use of MCC as a disintegrant. Overall, excipients (and model drugs) showed mechanistic behaviour on the nano/micro scale that could be related to the functionality of materials on the macro scale.