Bioelectric effect and bacterial biofilms. A systematic review

Revealing detrimental effects of various DC electrical energy conditions on different multidrug resistant bacteria: a comprehensive study

The arbitrary discharge of contaminated wastes, especially that encompass multidrug resistant microbes (MDR), would broaden the circle of epidemic diseases such as COVID-19, which in turn deteriorate definitely the whole socioeconomics. Therefore, the employment of electrical stimulation techniques such as direct current (DC) with low energy considers being effective tool to impede spontaneous changes in microbial genetic makeup, which increases the prevalence of MDR phenomenon. Herein, the influence of different electric energies generated by DC electric field, volts and time on MDR-bacteria that are categorized among the highly ranked nosocomial pathogens, was scrutinized. Wherein, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis were examined as paradigms of Gram-negative and Gram-positive pathogens. The results declared the significant superior antagonizing potency of electric energy in a dose-dependent modality rather than the applied volts or exposure time. Notably, the exposure of bacterial cultures to140 J inhibited the bacterial count by > 78% and the range of 47-73% for Gram-negative and Gram-positive, respectively. While the suppression in their metabolic activity assessed by > 75% and 41-68%, respectively; reflecting the capability of electrical energy to induce viable but non-culturable (VBNC) state. Similarly, the results of total protein, extracellular protein content and lactate dehydrogenase activity emphasized the cell wall deterioration and losing of cell membrane integrity. Additionally, the elevating in ROS upon DC-exposure participated in DNA fragmentation and plasmid decomposability by the range of 33-60%. Further, SEM micrographs depicted drastic morphological deformations after electrical treatment. Strikingly, DC-treatment impaired antibiotic resistance of the examined strains against several antibiotics by > 64.2%. Generally, our comparative detailed study revealed deleterious potentiality of different DC-protocols in defeating microbial pollution, which could be invested as efficient disinfectant alternative in various sectors such as milk sterilization and wastewater purification.

Electric Current Application on Dental Implant Biofilms: Review

The prevalence of complications due to the presence of biofilms in dental implant surfaces and their relationship with peri-implant diseases, namely peri-implantitis, remain difficult problems to overcome. The information available about the application of electric current on dental implant biofilms; its parameters, namely current level, voltage and exposure time; and related effects are still not enough to understand which individual mechanisms are caused by this technique, culminating in the decrease or eradication of the biofilm. The purpose of this narrative review, based on a systematic search, is to understand the effect of electric current directly applied to biofilms present in dental implants and which parameters are used. For the systematic search, electronic databases including MEDLINE/PubMed, Scopus, and Web of Science, up to and including November 2023, were searched. Seven studies were included. A 12-item checklist was used to assess their methodological quality. All studies used direct/constant electric current; however, that use was not achieved by the same protocol/set-up. Parameters such as current, voltage, resistance, and actuation time were different in all studies. Monospecies and multi-species biofilm were used in the substrate made of titanium. The results indicate that the use of constant and alternating electric current directly applied to dental implant's surfaces is a promising way to treat problems related to biofilms and peri-implant diseases. Future trials, namely in vivo tests, are necessary to reveal all the potential of this treatment.

The treatment of bacterial biofilms cultivated on knee arthroplasty implants using the bioelectric effect

Introduction: The formation of bacterial biofilms on knee arthroplasty implants can have catastrophic consequences. The aim of this study was to analyze the effectiveness of the bioelectric effect in the elimination of bacterial biofilms on cultivated knee arthroplasty implants. Methods: A novel device was designed to deliver a bioelectric effect on the surface of knee arthroplasty implants. 4-femoral prosthetic implants were cultivated with a staphylococcus aureus inoculum for 15 days. The components were divided into four different groups: A (not treated), B (normal saline 20-minutes), C (bioelectric effect 10-minutes), D (bioelectric effect 20-minutes). The implants were sonicated, and the detached colonies were quantified as the number of colony-forming unit (CFUs). The implants were sterilised and the process was repeated in a standardized manner four more times, to obtain a total of five samples per group. Results: The number of the CFUs after a 10-minute exposure to the bioelectric effect was of 208.2 ± 240.4, compared with 6,041.6 ± 2010.7 CFUs in group A, representing a decrease of 96.5% ± 4.3 (p = 0.004). And a diminution of 91.8% ± 7.9 compared with 2,051.0 ± 1,364.0 CFUs in group B (p = 0.109). The number of bacterial colonies after a 20-minute exposure to the bioelectric effect was 70 ± 126.7 CFUs, representing a decrease of 98.9% ± 1.9 (p = 0.000) compared with group A. And a decrease of 97.8% ± 3.0 (p = 0.019) compared with group B. Conclusions: The bioelectric effect was effective in the elimination of bacterial biofilm from knee arthroplasty implants. This method could be used in the future as part of conventional surgical procedures.

The effect of dental material type and masticatory forces on periodontitis-derived subgingival microbiomes

Restorative dental materials can frequently extend below the gingival margin, serving as a potential haven for microbial colonization, and altering the local oral microbiome to ignite infection. However, the contribution of dental materials on driving changes of the composition of the subgingival microbiome is under-investigated. This study evaluated the microbiome-modulating properties of three biomaterials, namely resin dental composites (COM), antimicrobial piezoelectric composites (BTO), and hydroxyapatite (HA), using an optimized in vitro subgingival microbiome model derived from patients with periodontal disease. Dental materials were subjected to static or cyclic loading (mastication forces) during biofilm growth. Microbiome composition was assessed by 16S rRNA gene sequencing. Dysbiosis was measured in terms of subgingival microbial dysbiosis index (SMDI). Biomaterials subjected to cyclic masticatory loads were associated with enhanced biofilm viability except on the antibacterial composite. Biomaterials held static were associated with increased biofilm biomass, especially on HA surfaces. Overall, the microbiome richness (Chao index) was similar for all the biomaterials and loading conditions. However, the microbiome diversity (Shannon index) for the HA beams was significantly different than both composites. In addition, beta diversity analysis revealed significant differences between composites and HA biomaterials, and between both loading conditions (static and cyclic). Under static conditions, microbiomes formed over HA surfaces resulted in increased dysbiosis compared to composites through the enrichment of periopathogens, including Porphyromonas gingivalis, Porphyromonas endodontalis, and Fretibacterium spp., and depletion of commensals such as Granulicatella and Streptococcus spp. Interestingly, cyclic loading reversed the dysbiosis of microbiomes formed over HA (depletion of periopathogenes) but increased the dysbiosis of microbiomes formed over composites (enrichment of Porphyromonas gingivalis and Fusobacterim nucleatum). Comparison of species formed on both composites (control and antibacterial) showed some differences. Commercial composites enriched Selenomonas spp. and depleted Campylobacter concisus. Piezoelectric composites effectively controlled the microbiome viability without significantly impacting the species abundance. Findings of this work open new understandings of the effects of different biomaterials on the modulation of oral biofilms and the relationship with oral subgingival infections.

Evaluation of dental plaque reduction using microcurrent-emitting toothbrushes in orthodontic patients: a randomized, double-blind, crossover clinical trial

This study aimed to compare the effectiveness of microcurrent-emitting toothbrushes (MCTs) and ordinary toothbrushes in reducing the dental plaque index (PI) and dental caries activity among orthodontic patients. The evaluation was performed using a crossover study design involving 22 orthodontic patients randomly assigned to the MCT or ordinary toothbrush groups. The participants used the designated toothbrush for 4 weeks and had a 1-week wash-out time before crossover to the other toothbrush. PI (Attin's index) and dental caries activity were measured at baseline and at the end of each 4-week period. Additionally, patients completed questionnaires to assess patient satisfaction for "freshness in mouth" and "cleansing degree." The results showed that the MCT group had a significant reduction in PI (p = 0.009), whereas the ordinary toothbrush group did not (p = 0.595). There was no significant difference in the dental caries activity between the two groups (p > 0.05). Patient satisfaction assessment revealed that 65% patients in the MCT group had more than "fair" experience of freshness, in contrast to 50% of patients in the ordinary toothbrush group. Satisfaction with cleansing degree was similar in both groups. Overall, these findings suggest that MCTs are more effective in reducing dental PI than ordinary toothbrushes.

Transcriptomic profiles of Mannheimia haemolytica planktonic and biofilm associated cells

Mannheimia haemolytica is the principal agent contributing to bovine respiratory disease and can form biofilms with increased resistance to antibiotic treatment and host immune defenses. To investigate the molecular mechanisms underlying M. haemolytica biofilm formation, transcriptomic analyses were performed with mRNAs sequenced from planktonic and biofilm cultures of pathogenic serotypes 1 (St 1; strain D153) and St 6 (strain D174), and St 2 (strain D35). The three M. haemolytica serotypes were cultured in two different media, Roswell Park Memorial Institute (RPMI) 1640 and brain heart infusion (BHI) to form the biofilms. Transcriptomic analyses revealed that the functions of the differentially expressed genes (DEGs) in biofilm associated cells were not significantly affected by the two media. A total of 476 to 662 DEGs were identified between biofilm associated cells and planktonic cells cultured under BHI medium. Functional analysis of the DEGs indicated that those genes were significantly enriched in translation and many biosynthetic processes. There were 234 DEGs identified in St 1 and 6, but not in St 2. The functions of the DEGs included structural constituents of ribosomes, transmembrane proton transportation, proton channels, and proton-transporting ATP synthase. Potentially, some of the DEGs identified in this study provide insight into the design of new M. haemolytica vaccine candidates.

Automated measurement of transepithelial electrical resistance (TEER) in 96-well transwells using ECIS TEER96: Single and multiple time point assessments

Transepithelial electrical resistance (TEER) is a widely used technique for quantifying the permeability of epithelial and endothelial cell layers. However, traditional methods of measuring TEER are limited to single timepoint measurements and can subject cells to an altered environment during the measurement. Here, we assessed the validity of TEER measurements by the ECIS TEER96 device, which is designed to take continuous TEER measurements of a cell culture system in a standard laboratory incubator. We found that the instrument accurately measures TEER across TEER values ranging from 10 to 2050 Ω*cm2 and is more accurate than the manual epithelial voltohmmeter electrode at high TEER values. Furthermore, the high-resolution measurements provided by the device allowed for a unique insight into the mechanisms and kinetics of cells in vitro. To demonstrate the continuous measurement capability of the device, we tracked the formation of an MDCKI cell monolayer until TEER plateaued. Furthermore, we treated Caco-2 monolayers with different concentrations of DMSO and the antimicrobial and surfactant compound benzethonium chloride to measure disruptions to barrier integrity. Treatment of both compounds resulted in concentration-dependent loss of barrier integrity. Our results suggest that the ECIS TEER96 device is a reliable and convenient option for measuring TEER in cell cultures and can provide valuable insights into the behavior of cells in vitro. This technology will be especially useful for increasing throughput of drug permeability assays, inflammation studies, and gaining better understanding of disease states in a cell culture system.

A Prospective, Randomized, Controlled Study to Evaluate the Effectiveness of a Fabric-Based Wireless Electroceutical Dressing Compared to Standard-of-Care Treatment Against Acute Trauma and Burn Wound Biofilm Infection

Objective: Despite advances in the use of topical and parenteral antimicrobial therapy and the practice of early tangential burn wound excision to manage bacterial load, 60% of the mortality from burns is attributed to bacterial biofilm infection. A low electric field (∼1 V) generated by the novel FDA-cleared wireless electroceutical dressing (WED) was previously shown to significantly prevent and disrupt burn biofilm infection in preclinical studies. Based on this observation, the purpose of this clinical trial was to evaluate the efficacy of the WED dressing powered by a silver-zinc electrocouple in the prevention and disruption of biofilm infection. Approach: A prospective, randomized, controlled, single-center clinical trial was performed to evaluate the efficacy of the WED compared with standard-of-care (SoC) dressing to treat biofilms. Burn wounds were randomized to receive either SoC or WED. Biopsies were collected on days 0 and 7 for histology, scanning electron microscopy (SEM) examination of biofilm, and for quantitative bacteriological analyses. Results: In total, 38 subjects were enrolled in the study. In 52% of the WED-treated wounds, little to no biofilm could be detected by SEM. WED significantly lowered or prevented increase of biofilm in all wounds compared with the pair-matched SoC-treated wounds. Innovation: WED is a simple, easy, and rapid method to protect the wound while also inhibiting infection. It is activated by a moist environment and the electrical field induces transient and micromolar amounts of superoxide anion radicals that will prevent bacterial growth. Conclusion: WED decreased biofilm infection better compared with SoC. The study was registered in clinicaltrials.gov as NCT04079998.

Significant removal of bacterial biofilm induced by multiple-Short ranges of electric interventions

BACKGROUND

Biofilm-related infections are serious problems in the Orthopedics field, and Staphylococcus aureus are the most popular causative agents of bacterial infections associated with arthroplasty. Several studies demonstrated a synergistic effect of the electric intervention (EI) and the antibiotic administration in killing bacteria in biofilm; however, a constant, long-time EI was needed. In the present study, the effective removal of biofilm formed with S. aureus on a titanium ring by multiple times of one minute-EI was observed and described.

METHODS

A methicillin-sensitive S. aureus clinical isolate was used to form biofilm on a titanium ring. After applying a series of EI with various combinations of the frequencies and timings, the amount and principal components of biofilms were assessed with crystal violet staining, live bacterial cell count, and fluorescence staining with confocal laser scanning microscopy.

RESULTS

More than 60% biofilm removal was observed in the 2-time EI applied at 24 (1) and 72 (3) h (days) post bacterial exposure (PBE) and in the 3-time EI at 0 (0), 24 (1), and 72 (3) h (days) PBE, or at 24 (1), 48 (2), and 72 (3) h (days) PBE. The live bacterial cell numbers, the proportion of live and dead cells, and the amount of extracellular polysaccharide substances (EPS) of biofilm were similar with or without EI. It was assumed that an excess amount of the biofilm removal shown in the several EI was not attributed to the effect of the electrolysis.

CONCLUSIONS

The effective removal of biofilm was observed when multiple times 1 min EI was applied without any changes in the proportion of live and dead bacteria or the amount of EPS. The mechanisms to explain extra biofilm removal remain to be elucidated.

Bioelectric device for effective biofilm inflammation management of dental implants

Dental implant inflammation is primarily caused by oral biofilms, which form within 8 h, particularly at 37 °C, thereby requiring diligent cleaning. Considering the complex management of dental implants, a novel technology based on the bioelectric effect (BE) to combat inflammation has emerged. A BE-integrated toothbrush was developed and clinically tested on patients with dental implants (N = 36). Our findings revealed a significant average plaque index reduction of 67% with BE technology compared with that at baseline (P < 0.05), whereas non-BE did not yield statistical significance even after 4 weeks of use (P > 0.05). The bleeding index demonstrated a 59% average reduction in all surfaces with BE technology (P < 0.05), whereas the non-BE group exhibited no significant change. Substantial reductions in total plaque and bleeding indices suggest that using BE toothbrushes can help effectively remove oral biofilms and treat bleeding symptoms.

Combined effect of electrical energy and graphene oxide on Enterococcus faecalis biofilms

This study aimed to investigate the effects of electrical energy and its synergistic activity with graphene oxide (GO) in Enterococcus faecalis (E. faecalis) biofilms. The viability of E. faecalis biofilms was analyzed by colony-forming units, crystal violet staining, and confocal laser scanning microscopy. The morphologies of the biofilms and the bacterial organelles were observed by scanning electron microscopy and transmission emission microscopy (TEM), respectively. Application of electrical energy combined with 0.2% sodium hypochlorite (NaOCl) on E. faecalis in biofilms significantly decreased the bacterial viability and biofilm biomass compared to the 0.2% NaOCl-only-treated group. Furthermore, additional application of GO showed similar antibacterial effects to 0.5% NaOCl. Notably, TEM observation revealed that the bacteria treated with electric energy and GO showed damaged cell membranes. The results suggest that combination of electrical energy and GO enhances antibacterial activity of NaOCl and has the potential to be applied to root canal irrigation protocols.

The Alphabet of Nanostructured Polypyrrole

This review is devoted to polypyrrole and its morphology, which governs the electroactivity of the material. The macroscopic properties of the material are strictly relevant to microscopic ordering observed at the local level. During the synthesis, various (nano)morphologies can be produced. The formation of the ordered structure is dictated by the ability of the local forces and effects to induce restraints that help shape the structure. This review covers the aspects of morphology and roughness and their impact on the final properties of the modified electrode activity in selected applications.

In-situ cathodic electrolysis coupled with hydraulic backwash inhibited biofilm formation on a backwashable carbon nanotube membrane

Electro-coupled membrane filtration (ECMF) is an innovative and green technology for water and wastewater treatment. However, the dynamics of biofouling development in the ECMF system has yet been determined. This fundamental question was systematically investigated in this study through laboratory dead-end ECMF experiments. It was found that the ECMF process with an applied voltage of 3 V and a backwash interval of 60 min was capable of completely eradicating membrane biofouling in an extended filtration time of 1450 min. In contrast, membrane biofouling was much severer with a longer backwash interval of 720 min or without backwash. The complemental permeate analysis and membrane characterization results revealed that biofouling during ECMF involved two sequential stages. During the first stage, dead bacteria and their degradation debris formed a loose deposit layer on the membrane surface. The continuous accumulation of this layer decreased the electrochemical performance of the membrane cathode. As such, bacteria in the top deposit layer proliferated and secreted extracellular polymeric substances, which led to irreversible fouling in the second stage. Therefore, timely removal of the initial deposit layer by hydraulic backwash was crucial in preventing irreversible membrane biofouling. These findings provided novel insights into the synergistic effects of cathodic electrolysis and hydraulic backwash for biofouling mitigation.

Photodynamic Therapy, Probiotics, Acetic Acid, and Essential Oil in the Treatment of Chronic Wounds Infected with Pseudomonas aeruginosa

As a prevalent medical problem that burdens millions of patients across the world, chronic wounds pose a challenge to the healthcare system. These wounds, often existing as a comorbidity, are vulnerable to infections. Consequently, infections hinder the healing process and complicate clinical management and treatment. While antibiotic drugs remain a popular treatment for infected chronic wounds, the recent rise of antibiotic-resistant strains has hastened the need for alternative treatments. Future impacts of chronic wounds are likely to increase with aging populations and growing obesity rates. With the need for more effective novel treatments, promising research into various wound therapies has seen an increased demand. This review summarizes photodynamic therapy, probiotics, acetic acid, and essential oil studies as developing antibiotic-free treatments for chronic wounds infected with Pseudomonas aeruginosa. Clinicians may find this review informative by gaining a better understanding of the state of current research into various antibiotic-free treatments. Furthermore. this review provides clinical significance, as clinicians may seek to implement photodynamic therapy, probiotics, acetic acid, or essential oils into their own practice.

Investigation of the antimicrobial effect of anodic iontophoresis on Gram-positive and Gram-negative bacteria for skin infections treatment

Iontophoresis, a non-invasive application of a constant low-intensity electric current, is a promising strategy to accelerate wound healing. Although its mechanisms are not yet fully elucidated, part of its action seems related to inhibiting bacteria growth. This work aimed to investigate the antimicrobial effect of iontophoresis using Staphylococcus epidermidis and Escherichia coli strains, Gram-positive and Gram-negative bacteria, respectively. Anodic iontophoresis was applied to each bacterial suspension using Ag/AgCl electrodes, and bacteria viability was evaluated after 24 h incubation by counting colony-forming units. A Quality-by-Design approach was performed to assess the influence of the iontophoresis' intensity and application time on bacterial viability. Cell morphology was evaluated by scanning electron microscopy. Iontophoresis showed antimicrobial effects on the Gram-positive bacteria only at 5 mA and 60 min application. However, a linear relationship was observed between intensity and application time for the Gram-negative one, causing drastic morphological changes and up to 98 % death. The cell wall of Gram-negative bacteria seems more susceptible to disorganization triggered by iontophoresis-induced ion transport than Gram-positive ones. Therefore, anodic iontophoresis can be a powerful ally in controlling Gram-negative bacteria proliferation in wounds.

A Highly Efficacious Electrical Biofilm Treatment System for Combating Chronic Wound Bacterial Infections

Biofilm infection has a high prevalence in chronic wounds and can delay wound healing. Current treatment using debridement and antibiotic administration imposes a significant burden on patients and healthcare systems. To address their limitations, a highly efficacious electrical antibiofilm treatment system is described in this paper. This system uses high-intensity current (75 mA cm-2 ) to completely debride biofilm above the wound surface and enhance antibiotic delivery into biofilm-infected wounds simultaneously. Combining these two effects, this system uses short treatments (≤2 h) to reduce bacterial count of methicillin-resistant S. aureus (MRSA) biofilm-infected ex vivo skin wounds from 1010 to 105.2 colony-forming units (CFU) g-1 . Taking advantage of the hydrogel ionic circuit design, this system enhances the in vivo safety of high-intensity current application compared to conventional devices. The in vivo antibiofilm efficacy of the system is tested using a diabetic mouse-based wound infection model. MRSA biofilm bacterial count decreases from 109.0 to 104.6 CFU g-1 at 1 day post-treatment and to 103.3 CFU g-1 at 7 days post-treatment, both of which are below the clinical threshold for infection. Overall, this novel technology provides a quick, safe, yet highly efficacious treatment to chronic wound biofilm infections.

Weak direct current exerts synergistic effect with antibiotics and reduces the antibiotic resistance: An in vitro subgingival plaque biofilm model

BACKGROUND AND OBJECTIVE

Weak direct current (DC) exerts killing effect and synergistic killing effect with antibiotics in some specific bacteria biofilms. However, the potential of weak DC alone or combined with periodontal antibiotics in controlling periodontal pathogens and plaque biofilms remains unclear. The objective of this study was to investigate whether weak DC could exert the anti-biofilm effect or enhance the killing effect of metronidazole (MTZ) and/or amoxicillin-clavulanate potassium (AMC) on subgingival plaque biofilms, by constructing an in vitro subgingival plaque biofilm model.

METHODS

The pooled subgingival plaque and saliva of patients with periodontitis (n = 10) were collected and cultured anaerobically on hydroxyapatite disks in vitro for 48 h to construct the subgingival plaque biofilm model. Then such models were stimulated with 0 μA DC alone (20 min/12 h), 1000 μA DC alone (20 min/12 h), 16 μg/ml MTZ, 16 μg/ml AMC or their combination, respectively. Through viable bacteria counting, metabolic activity assay, quantitative real-time PCR absolute quantification and 16S rDNA sequencing analysis, the anti-biofilm effect of 1000 μA DC and enhanced killing effects of 1000 μA DC combined with antibiotics (MTZ, AMC or MTZ+AMC) were explored.

RESULTS

The old subgingival plaque model (48 h) had no significant difference in total bacterial loads from subgingival plaque in situ, which achieved a similarity of 80%. The 1000 μA DC plus MTZ or AMC for 12 h showed a stronger synergistic killing effect than the same combination for 20 min. The metabolic activity was reduced to the lowest by DC plus MTZ+AMC, as 37.4% of that in the control group, while average synergistic killing effect reached 1.06 log units and average total bacterial loads decreased to 0.87 log units. Furthermore, the relative abundance of the genera Porphyromonas, Prevotella, Treponema_2, and Tannerella were decreased significantly.

CONCLUSION

The presence of weak DC (1000 μA) improved the killing effect of antibiotics on subgingival plaque biofilms, which might provide a novel strategy to reduce their antibiotic resistance.

Biofilm Lifestyle in Recurrent Urinary Tract Infections

Urinary tract infections (UTIs) represent one of the most common infections that are frequently encountered in health care facilities. One of the main mechanisms used by bacteria that allows them to survive hostile environments is biofilm formation. Biofilms are closed bacterial communities that offer protection and safe hiding, allowing bacteria to evade host defenses and hide from the reach of antibiotics. Inside biofilm communities, bacteria show an increased rate of horizontal gene transfer and exchange of resistance and virulence genes. Additionally, bacterial communication within the biofilm allows them to orchestrate the expression of virulence genes, which further cements the infestation and increases the invasiveness of the infection. These facts stress the necessity of continuously updating our information and understanding of the etiology, pathogenesis, and eradication methods of this growing public health concern. This review seeks to understand the role of biofilm formation in recurrent urinary tact infections by outlining the mechanisms underlying biofilm formation in different uropathogens, in addition to shedding light on some biofilm eradication strategies.

Drug delivery approaches for enhanced antibiofilm therapy

Biofilms have attracted increasing attention in recent years. Many bacterial infections are associated with biofilm formation. A bacterial biofilm is an aggregated membrane-like substance that is composed of a large number of bacteria and their secreted extracellular polymeric substances. The traditional antibiofilm approaches, such as chemotherapy based on antibiotics, are often ineffective in eradicating biofilms owing to the limited diffusion ability of antibiotics within biofilms and inactivation of antibiotics by biofilms. Moreover, a larger dosage of antibiotics could be effective, but leads to an increased tolerance. Smart drug delivery systems that deliver antibiotics into the biofilm interior is a promising strategy to meet this challenge. In this review, we focus on the methods to improve drug delivery efficiency for enhanced chemotherapy of biofilms. Furthermore, we have summarized chemical approaches for enhanced drug delivery, such as chemical shields, charge reversal, and dual corona enhanced delivery strategies; these methods focus on physicochemical biofilm properties and specific biofilm features. Afterwards, physical approaches are discussed, such as magnetism-mediated drug delivery, electricity-mediated drug delivery, ultrasound-mediated drug delivery, and shock wave-mediated drug delivery. Finally, a perspective on the development of next-generation antibiofilm drug delivery systems is given.

Physical Approaches to Prevent and Treat Bacterial Biofilm

Prosthetic joint infection (PJI) presents several clinical challenges. This is in large part due to the formation of biofilm which can make infection eradication exceedingly difficult. Following an extensive literature search, this review surveys a variety of non-pharmacological methods of preventing and/or treating biofilm within the body and how they could be utilized in the treatment of PJI. Special attention has been paid to physical strategies such as heat, light, sound, and electromagnetic energy, and their uses in biofilm treatment. Though these methods are still under study, they offer a potential means to reduce the morbidity and financial burden related to multiple stage revisions and prolonged systemic antibiotic courses that make up the current gold standard in PJI treatment. Given that these options are still in the early stages of development and offer their own strengths and weaknesses, this review offers an assessment of each method, the progress made on each, and allows for comparison of methods with discussion of future challenges to their implementation in a clinical setting.

Ultrasound-Enhanced Antibacterial Activity of Polymeric Nanoparticles for Eradicating Bacterial Biofilms

Bacterial biofilms are a major healthcare concern resulting in refractory conditions such as chronic wounds, implant infections and failure, and multidrug-resistant infections. Aggressive and invasive strategies are employed to cure biofilm infections but are prone to long and expensive treatments, adverse side-effects, and low patient compliance. Recent strategies such as ultrasound-based therapies and antimicrobial nanomaterials have shown some promise in the effective eradication of biofilms. However, maximizing therapeutic effect while minimizing healthy tissue damage is a key challenge that needs to be addressed. Here a combination treatment involving ultrasound and antimicrobial polymeric nanoparticles (PNPs) that synergistically eradicate bacterial biofilms is reported. Ultrasound treatment rapidly disrupts biofilms and increases penetration of antimicrobial PNPs thereby enhancing their antimicrobial activity. This results in superior biofilm toxicity, while allowing for a two- to sixfold reduction in both the concentration of PNPs as well as the duration of ultrasound. Furthermore, that this reduction minimizes cytotoxicity toward fibroblast cells, while resulting in a 100- to 1000-fold reduction in bacterial concentration, is demonstrated.

Enzyme-Photocatalyst Tandem Microrobot Powered by Urea for Escherichia coli Biofilm Eradication

Urinary-based infections affect millions of people worldwide. Such bacterial infections are mainly caused by Escherichia coli (E. coli) biofilm formation in the bladder and/or urinary catheters. Herein, the authors present a hybrid enzyme/photocatalytic microrobot, based on urease-immobilized TiO₂ /CdS nanotube bundles, that can swim in urea as a biocompatible fuel and respond to visible light. Upon illumination for 2 h, these microrobots are able to remove almost 90% of bacterial biofilm, due to the generation of reactive radicals, while bare TiO₂ /CdS photocatalysts (non-motile) or urease-coated microrobots in the dark do not show any toxic effect. These results indicate a synergistic effect between the self-propulsion provided by the enzyme and the photocatalytic activity induced under light stimuli. This work provides a photo-biocatalytic approach for the design of efficient light-driven microrobots with promising applications in microbiology and biomedicine.

Investigating the anti-streptococcal biofilm effect of ssDNA aptamer-silver nanoparticles complex on a titanium-based substrate

Streptococcus mutans is a commensal and opportunistic pathogen that causes several diseases by forming a biofilm in humans and animals in many areas such as nasopharyngeal, cardiac valves, lungs, and oral cavity. Biofilms are very important in prosthetic infections associated with medical implants. The use of nanoparticles is one of the evolving fields in biofilm targeting. Silver nanoparticles can be used for biofilm targeting due to their inherent antimicrobial properties. Hybridization of nanoparticles with small molecules increases their biological properties and makes them multifunctional. The present investigation aimed to design an appropriate silver nanoparticles-aptamer complex that binds to the surface receptors of streptococcal strains. For this reason, silver nanoparticles with particle sizes in a range of 50 to 70 nm were synthesized and connected to a designed aptamer with a streptavidin-biotin linker. Then, the effect of the complex was investigated on the S. mutans biofilm formed on the surface of a medical-grade titanium substrate. The silver nanoparticles-aptamer complex at a concentration of 100 μg mL-1 after 48 h inhibited 43% of the biofilm formation and degraded 63% of the formed biofilm. Also, the cell availability reached 96% and the complex was stable in cell medium culture for 360 min. It was concluded that this complex could be a good candidate for removing the formed biofilms on the surface of titanium implants.

Enzymatic Dispersion of Biofilms: An Emerging Biocatalytic Avenue to Combat Biofilm-Mediated Microbial Infections

Drug resistance by pathogenic microbes has emerged as a matter of great concern to mankind. Microorganisms such as bacteria and fungi employ multiple defense mechanisms against drugs and the host immune system. A major line of microbial defense is the biofilm, which comprises extracellular polymeric substances that are produced by the population of microorganisms. Around 80% of chronic bacterial infections are associated with biofilms. The presence of biofilms can increase the necessity of doses of certain antibiotics up to 1000-fold to combat infection. Thus, there is an urgent need for strategies to eradicate biofilms. Although a few physicochemical methods have been developed to prevent and treat biofilms, these methods have poor efficacy and biocompatibility. In this review, we discuss the existing strategies to combat biofilms and their challenges. Subsequently, we spotlight the potential of enzymes, in particular, polysaccharide degrading enzymes, for biofilm dispersion, which might lead to facile antimicrobial treatment of biofilm-associated infections.

Nanoarchitectonics of Electrically Activable Phosphonium Self-Assembled Monolayers to Efficiently Kill and Tackle Bacterial Infections on Demand

Prosthetic implants are widely used in dentistry and orthopedics and, as a result, infections can occur which cause their removal. Therefore, it is essential to propose methods of eradicating the bacteria that remain on the prosthesis during treatment. For this purpose, it is necessary to develop surfaces whose antibacterial activity can be controlled. Herein, we designed innovative and smart phosphonium self-assembled monolayer (SAM) interfaces that can be electrically activated on demand for controlling bacterial contaminations on solid surfaces. Upon electroactivation with a low potential (0.2 V for 60 min., conditions determined through a DOE), a successful stamping out of Gram-positive and Gram-negative bacterial strains was obtained with SAM-modified titanium surfaces, effectively killing 95% of Staphylococcus aureus and 90% Klebsiellapneumoniae. More importantly, no toxicity towards eukaryotic cells was observed which further enhances the biocompatible character of these novel surfaces for further implementation.

Bacterial biofilm infections, their resistance to antibiotics therapy and current treatment strategies

Nearly 80% of human chronic infections are caused due to bacterial biofilm formation. This is the most leading cause for failure of medical implants resulting in high morbidity and mortality. In addition, biofilms are also known to cause serious problems in food industry. Biofilm impart enhanced antibiotic resistance and become recalcitrant to host immune responses leading to persistent and recurrent infections. It makes the clinical treatment for biofilm infections very difficult. Reduced penetration of antibiotic molecules through EPS, mutation of the target site, accumulation of antibiotic degrading enzymes, enhanced expression of efflux pump genes are the probable causes for antibiotics resistance. Accordingly, strategies like administration of topical antibiotics and combined therapy of antibiotics with antimicrobial peptides are considered for alternate options to overcome the antibiotics resistance. A number of other remediation strategies for both biofilm inhibition and dispersion of established biofilm have been developed. The metallic nanoparticles and their oxides have recently gained a tremendous thrust as antibiofilm therapy for their unique features. This present comprehensive review gives the understanding of antibiotic resistance mechanisms of biofilm and provides an overview of various currently available biofilm remediation strategies, focusing primarily on the applications of metallic nanoparticles and their oxides.

Comparisons of the killing effect of direct current partially mediated by reactive oxygen species on Porphyromonas gingivalis and Prevotella intermedia in planktonic state and biofilm state - an in vitro study

Background/purpose

Bacterial biofilms formed on the surface of tissues and biomaterials are major causes of chronic infections in humans. Among them, Porphyromonas gingivalis (P. gingivalis) and Prevotella intermedia (P. intermedia) are anaerobic pathogens causing dental infections associated with periodontitis. In this study, we evaluated the killing effect and underlying mechanisms of direct current (DC) as an antimicrobial method in vitro.

Materials and methods

We chose P. gingivalis and P. intermedia in different states to make comparisons of the killing effect of DC. By viable bacteria counting, fluorescent live/dead staining, reactive oxygen species (ROS) assay, addition of ROS scavenger DMTU and mRNA expression assay of ROS scavenging genes, the role of ROS in the killing effect was explored.

Results

The planktonic and biofilm states of two bacteria could be effectively killed by low-intensity DC. For the killing effect of 1000 μA DC, there were significant differences whether on planktonic P. gingivalis and P. intermedia (mean killing values: 2.40 vs 2.62 log₁₀ CFU/mL) or on biofilm state of those (mean killing values: 0.63 vs 0.98 log₁₀ CFU/mL). 1000 μA DC greatly induced ROS production and the mRNA expression of ROS scavenging genes. DMTU could partially decrease the killing values of DC and downregulate corresponding gene’s expression.

Conclusion

1000 μA DC can kill P. gingivalis and P. intermedia in two states by promoting overproduction of ROS, and P. intermedia is more sensitive to DC than P. gingivalis. These findings indicate low-intensity DC may be a promising approach in treating periodontal infections.

Ionic Silver and Electrical Treatment for Susceptibility and Disinfection of Escherichia coli Biofilm-Contaminated Titanium Surface

In this work, surface disinfection and biofilm susceptibility were investigated by applying ionic silver of 0.4–1.6 µg/mL and cathodic voltage-controlled electrical treatment of 1.8 V and a current of 30 mA to Escherichia coli (E. coli) ATCC 25922 biofilm-contaminated titanium substrates. Herein, it is evident that the treatment exhibited the potential use to enhance the susceptibility of bacterial biofilms for surface disinfection. In vitro studies have demonstrated that the ionic silver treatment of 60 min significantly increased the logarithmic reduction (LR) of bacterial populations on disinfectant-treated substrates and the electrical treatment enhanced the silver susceptibility of E. coli biofilms. The LR values after the ionic silver treatments and the electric-enhanced silver treatments were in the ranges of 1.94–2.25 and 2.10–2.73, respectively. The treatment was also associated with morphological changes in silver-treated E. coli cells and biofilm-contaminated titanium surfaces. Nevertheless, the treatments showed no cytotoxic effects on the L929 mouse skin fibroblast cell line and only a slight decrease in pH was observed during the electrical polarization of titanium substrate.

Direct current exerts electricidal and bioelectric effects on Porphyromonas gingivalis biofilms partially via promoting oxidative stress and antibiotic transport

Low electric current can inhibit certain microbial biofilms and enhance the efficacy of antimicrobials against them. This study investigated the electricidal and bioelectric effects of direct current (DC) against Porphyromonas gingivalis biofilms as well as the underlying mechanisms. Here, we firstly showed that DC significantly suppressed biofilm formation of P. gingivalis in time- and intensity-dependent manners, and markedly inhibited preformed P. gingivalis biofilms. Moreover, DC enhanced the killing efficacy of metronidazole (MTZ) and amoxicillin with clavulanate potassium (AMC) against the biofilms. Notably, DC-treated biofilms displayed upregulated intracellular ROS and expression of ROS related genes (sod, feoB, and oxyR) as well as porin gene. Interestingly, DC-induced killing of biofilms was partially reversed by ROS scavenger N-dimethylthiourea (DMTU), and the synergistic effect of DC with MTZ/AMC was weakened by small interfering RNA of porin gene (si-Porin). In conclusion, DC can exert electricidal and bioelectric effects against P. gingivalis biofilms partially via promotion of oxidative stress and antibiotic transport, which offers a promising approach for effective management of periodontitis.

Eltarahony M, E. Moustafa M. The impact of titanium oxide nanoparticles and low direct electric current on biofilm dispersal of $Bacillus~cereus$ and $Pseudomonas~aeruginosa$: A comparative study

Bacteria growing in biofilms cause a wide range of environmental, industrial and public health risks. Because biofilm bacteria are very resistant to antibiotics, there is an urgent need in medicine and industry to develop new approaches to eliminating bacterial biofilms. One strategy for controlling these biofilms is to generate an antibiofilm substance locally at the attachment surface. Direct electric current (DC) and nanoparticles (NPs) of metal oxides have outstanding antimicrobial properties. In this study we evaluated the effect of titanium oxide nanoparticle (TiO$_2$-NP) concentrations from 5 to 160 $\mu$g/mL on Bacillus cereus and Pseudomonas aeruginosa biofilms, and compared this with the effect of a 9 V, 6 mA DC electric field for 5, 10 and 15 min. TiO$_2$-NPs were characterized using transmission and scanning electron microscopes, X-ray diffraction and FTIR. They exhibited an average size of 22-34 nm. The TiO$_2$-NP concentrations that attained LD50 were $104 \pm 4$ $\mu$g/mL and $63 \pm 3$ $\mu$g/mL for B. cereus and P. aeruginosa, respectively. The eradication percentages obtained by DC at 5, 10, and 15 min exposure were 21%, 29%, and 33% respectively for B. cereus and 30%, 39%, and 44% respectively for P. aeruginosa. Biofilm disintegration was verified by exopolysaccharide, protein content and cell surface hydrophobicity assessment, as well as scanning electron microscopy. These data were correlated with the reactive oxygen species produced. The results indicated that both DC and TiO$_2$-NPs have a lethal effect on these bacterial biofilms, and that the DC conditions used affect the biofilms in a similar way to TiO$_2$-NPs at concentrations of 20-40 $\mu$g/mL.

Antimicrobial photodynamic therapy (aPDT) for biofilm treatments. Possible synergy between aPDT and pulsed electric fields

Currently, microbial biofilms have been the cause of a wide variety of infections in the human body, reaching 80% of all bacterial and fungal infections. The biofilms present specific properties that increase the resistance to antimicrobial treatments. Thus, the development of new approaches is urgent, and antimicrobial photodynamic therapy (aPDT) has been shown as a promising candidate. aPDT involves a synergic association of a photosensitizer (PS), molecular oxygen and visible light, producing highly reactive oxygen species (ROS) that cause the oxidation of several cellular components. This therapy attacks many components of the biofilm, including proteins, lipids, and nucleic acids present within the biofilm matrix; causing inhibition even in the cells that are inside the extracellular polymeric substance (EPS). Recent advances in designing new PSs to increase the production of ROS and the combination of aPDT with other therapies, especially pulsed electric fields (PEF), have contributed to enhanced biofilm inhibition. The PEF has proven to have antimicrobial effect once it is known that extensive chemical reactions occur when electric fields are applied. This type of treatment kills microorganisms not only due to membrane rupture but also due to the formation of reactive compounds including free oxygen, hydrogen, hydroxyl and hydroperoxyl radicals. So, this review aims to show the progress of aPDT and PEF against the biofilms, suggesting that the association of both methods can potentiate their effects and overcome biofilm infections.

Bioelectric Effect of a Microcurrent Toothbrush on Plaque Removal

This study evaluated the effectiveness of a microcurrent toothbrush (approved by the US Food and Drug Administration [FDA]), which employs a superimposed alternating and direct electric current, named as a Proxywave^® technology, similar to the intensity of the biocurrent, in plaque removal and reducing gingivitis by biofilm removal through the bioelectric effect. This study enrolled 40 volunteers with gingivitis. Dental observations were made every two weeks, before and after the use of each toothbrush. We randomly assigned participants into two groups: one group used the Proxywave^® toothbrush (PB) for two weeks followed by the control toothbrush (CB) for two weeks, while the other group used the CB for two weeks followed by the PB. The participants had a two-week washout period. If the toothbrush used earlier has had an effect on the bacterial flora in the oral cavity, this is to remove this effect and return it to its previous state. During each dental visit, we recorded plaque index (PI) and gingival index (GI) scores. The PI and GI scores were significantly lower in both the PB and the CB (p < 0.05). Considering the PI, there was no significant difference between the toothbrushes on all the surfaces. Considering the GI, the PB showed a significant decrease in the interproximal surface, compared to the CB (p < 0.05). The PB showed a significant decrease in the interproximal GI and had a beneficial effect in the interproximal area where the bristles could not reach. No adverse events were observed in the participants during the clinical trial. The microcurrent toothbrush is a device that can be safely used for plaque removal.

Bacterial Biofilm Inhibition: A Focused Review on Recent Therapeutic Strategies for Combating the Biofilm Mediated Infections

Biofilm formation is a major concern in various sectors and cause severe problems to public health, medicine, and industry. Bacterial biofilm formation is a major persistent threat, as it increases morbidity and mortality, thereby imposing heavy economic pressure on the healthcare sector. Bacterial biofilms also strengthen biofouling, affecting shipping functions, and the offshore industries in their natural environment. Besides, they accomplish harsh roles in the corrosion of pipelines in industries. At biofilm state, bacterial pathogens are significantly resistant to external attack like antibiotics, chemicals, disinfectants, etc. Within a cell, they are insensitive to drugs and host immune responses. The development of intact biofilms is very critical for the spreading and persistence of bacterial infections in the host. Further, bacteria form biofilms on every probable substratum, and their infections have been found in plants, livestock, and humans. The advent of novel strategies for treating and preventing biofilm formation has gained a great deal of attention. To prevent the development of resistant mutants, a feasible technique that may target adhesive properties without affecting the bacterial vitality is needed. This stimulated research is a rapidly growing field for applicable control measures to prevent biofilm formation. Therefore, this review discusses the current understanding of antibiotic resistance mechanisms in bacterial biofilm and intensely emphasized the novel therapeutic strategies for combating biofilm mediated infections. The forthcoming experimental studies will focus on these recent therapeutic strategies that may lead to the development of effective biofilm inhibitors than conventional treatments.

Novel treatment dynamics for biofilm-related infections

Introduction: As a result of progress in medical care, a huge number of medical devices are used in the treatment of human diseases. In turn, biofilm-related infection has become a growing threat due to the tolerance of biofilms to antimicrobials, a problem magnified by the development of antimicrobial resistance worldwide. As a result, successful treatment of biofilm-disease using only antimicrobials is problematic.Areas covered: We summarize some alternative approaches to classic antimicrobials for the treatment of biofilm disease. This review is not intended to be exhaustive but to give a clinical picture of alternatives to antimicrobial agents to manage biofilm disease. We highlight those strategies that may be closer to application in clinical practice.Expert opinion: There are a number of outstanding challenges in the development of novel antibiofilm therapies. Screening for effective antibiofilm compounds requires models relevant to all clinical scenarios. Although in vitro research of anti-biofilm strategies has progressed significantly over the past decade, there is a lack of in vivo research. In addition, the complexity of biofilm biology makes it difficult to develop a compound that is likely to provide the single 'magic bullet'. The multifaceted nature of biofilms imposes the need for multi-targeted or combinatorial therapies.

Functional Antimicrobial Surface Coatings Deposited onto Nanostructured 316L Food-Grade Stainless Steel

In our study, we demonstrated the performance of antimicrobial coatings on properly functionalized and nanostructured 316L food-grade stainless steel pipelines. For the fabrication of these functional coatings, we employed facile and low-cost electrochemical techniques and surface modification processes. The development of a nanoporous structure on the 316L stainless steel surface was performed by following an electropolishing process in an electrolytic bath, at a constant anodic voltage of 40 V for 10 min, while the temperature was maintained between 0 and 10 °C. Subsequently, we incorporated on this nanostructure additional coatings with antimicrobial and bactericide properties, such as Ag nanoparticles, Ag films, or TiO₂ thin layers. These functional coatings were grown on the nanostructured substrate by following electroless process, electrochemical deposition, and atomic layer deposition (ALD) techniques. Then, we analyzed the antimicrobial efficiency of these functionalized materials against different biofilms types (Candida parapsilosis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis). The results of the present study demonstrate that the nanostructuring and surface functionalization processes constitute a promising route to fabricate novel functional materials exhibiting highly efficient antimicrobial features. In fact, we have shown that our use of an appropriated association of TiO₂ layer and Ag nanoparticle coatings over the nanostructured 316L stainless steel exhibited an excellent antimicrobial behavior for all biofilms examined.

Use of electromagnetic stimulation on an Enterococcus faecalis biofilm on root canal treated teeth in vitro

Root canal disinfection is of utmost importance in the success of the treatment, thus, a novel method for achieving root canal disinfection by electromagnetic waves, creating a synergistic reaction via electric and thermal energy, was created. To study electromagnetic stimulation (EMS) for the disinfection of root canal in vitro, single rooted teeth were instrumented with a 45.05 Wave One Gold reciprocating file. Specimens were sterilized and inoculated with Enterococcus faecalis ATCC 29,212, which grew for 15 days to form an established biofilm. Samples were treated with 6% sodium hypochlorite (NaOCl), 1.5% NaOCl 1.5% NaOCl with EMS, 0.9% saline with EMS or 0.9% saline. After treatments, the colony forming units (CFU) was determined. Data was analyzed by Wilcoxon Rank Sums Test (α = 0.05). One sample per group was scored and split for confocal laser scanning microscopy imaging. There was a significant effect with the use of NaOCl with or without EMS versus 0.9% saline with or without EMS (p = 0.012 and 0.003, respectively). CFUs were lower when using 0.9% saline with EMS versus 0.9% saline alone (p = 0.002). Confocal imaging confirmed CFU findings. EMS with saline has an antibiofilm effect against E. faecalis and can potentially be applied for endodontic disinfection.

Integrated System for Bacterial Detection and Biofilm Treatment On Indwelling Urinary Catheters

GOAL

This work introduces an integrated system incorporated seamlessly with a commercial Foley urinary catheter for bacterial growth sensing and biofilm treatment.

METHODS

The system is comprised of flexible, interdigitated electrodes incorporated with a urinary catheter via a 3D-printed insert for impedance sensing and bioelectric effect-based treatment. Each of the functions were wirelessly controlled using a custom application that provides a user-friendly interface for communicating with a custom PCB via Bluetooth to facilitate implementation in practice.

RESULTS

The integrated catheter system maintains the primary functions of indwelling catheters - urine drainage, balloon inflation - while being capable of detecting the growth of Escherichia coli, with an average decrease in impedance of 13.0% after 24 hours, tested in a newly-developed simulated bladder environment. Furthermore, the system enables bioelectric effect-based biofilm reduction, which is performed by applying a low-intensity electric field that increases the susceptibility of biofilm bacteria to antimicrobials, ultimately reducing the required antibiotic dosage.

CONCLUSION

Overall, this modified catheter system represents a significant step forward for catheter-associated urinary tract infection (CAUTI) management using device-based approaches, integrating flexible electrodes with an actual Foley catheter along with the control electronics and mobile application.

SIGNIFICANCE

CAUTIs, exacerbated by the emergence of antibiotic-resistant pathogens, represent a significant challenge as one of the most prevalent healthcare-acquired infections. These infections are driven by the colonization of indwelling catheters by bacterial biofilms.

Antimicrobial and anti-adhesive properties of carbon nanotube-based surfaces for medical applications: a systematic review

Although high-performance carbon materials are widely used in surface engineering, with emphasis on carbon nanotubes (CNTs), the application of CNT nanocomposites on medical surfaces is poorly documented. In this study, we aimed to evaluate the antimicrobial and anti-adhesive properties of CNT-based surfaces. For this purpose, a PRISMA-oriented systematic review was conducted based on predefined criteria and 59 studies were selected for the qualitative analysis. Results from the analyzed studies suggest that surfaces containing modified CNTs, and specially CNTs conjugated with different polymers, exhibited strong antimicrobial and anti-adhesive activities. These composites seem to preserve the CNT toxicity to microorganisms and promote CNT-cell interactions, as well as to protect them from nonspecific protein adsorption. However, CNTs cannot yet compete with the conventional strategies to fight biofilms as their toxicity profile on the human body has not been thoroughly addressed. This review can be helpful for the development of new engineered medical surfaces.

A review of bacterial biofilm control by physical strategies

Biofilms are multicellular communities of microorganisms held together by a self-produced extracellular matrix, which contribute to hygiene problems in the food and medical fields. Both spoilage and pathogenic bacteria that grow in the complex structure of biofilm are more resistant to harsh environmental conditions and conventional antimicrobial agents. Therefore, it is important to develop eco-friendly preventive methodologies to eliminate biofilms from foods and food contact equipment. The present paper gives an overview of the current physical methods for biofilm control and removal. Current physical strategies adopted for the anti-biofilm treatment mainly focused on use of ultrasound power, electric or magnetic field, plasma, and irradiation. Furthermore, the mechanisms of anti-biofilm action and application of different physical methods are discussed. Physical strategies make it possible to combat biofilm without the use of biocidal agents. The remarkable microbiocidal properties of physical strategies are promising tools for antimicrobial applications.

New developments in anti-biofilm intervention towards effective management of orthopedic device related infections (ODRI's)

Orthopedic device related infections (ODRI's) represent a difficult to treat situation owing to their biofilm based nature. Biofilm infections once established are difficult to eradicate even with an aggressive treatment regimen due to their recalcitrance towards antibiotics and immune attack. The involvement of antibiotic resistant pathogens as the etiological agent further worsens the overall clinical picture, pressing on the need to look into alternative treatment strategies. The present review highlightes the microbiological challenges associated with treatment of ODRI's due to biofilm formation on the implant surface. Further, it details the newer anti-infective modalities that work either by preventing biofilm formation and/or through effective disruption of the mature biofilms formed on the medical implant. The study, therefore aims to provide a comprehensive insight into the newer anti-biofilm interventions (non-antibiotic approaches) and a better understanding of their mechanism of action essential for improved management of orthopedic implant infections.

Biofilm dispersion: The key to biofilm eradication or opening Pandora's box?

Biofilms are extremely difficult to eradicate due to their decreased antibiotic susceptibility. Inducing biofilm dispersion could be a potential strategy to help combat biofilm-related infections. Mechanisms of biofilm dispersion can basically be divided into two groups, i.e. active and passive dispersion. Active dispersion depends on a decrease in the intracellular c-di-GMP levels, leading to the production of enzymes that degrade the biofilm matrix and promote dispersion. In contrast, passive dispersion relies on triggers that directly release cells from the biofilm. In the present review, several active and passive dispersion strategies are discussed. In addition, the disadvantages and possible consequences of using dispersion as a treatment approach for biofilm-related infections are also reviewed.

Opportunities and challenges in managing antibiotic resistance in bacteria using plant secondary metabolites

Development of antibiotic resistance (ABR) in bacteria and its multidimensional spread is an emerging global threat that needs immediate attention. Extensive antibiotics (AB) usage results in development of ABR in bacteria by target modification, production of AB degrading enzymes, porin modifications, efflux pumps overexpression, etc. To counter this, apart from strict regulation of AB use and behavioural changes, research and development (R&D) of newer antimicrobials are in place. One such emerging approach to combat ABR is the use of structurally and functionally diverse plant secondary metabolites (PSMs) in combination with the conventional AB. Either the PSMs are themselves antimicrobial or they potentiate the activity of the AB through a range of mechanisms. However, their use is lagging due to poor knowledge of mode of action, structure-activity relationships, pharmacokinetics, etc. This review paper discussed the opportunities and challenges in managing ABR using PSMs. Mechanisms of ABR development in bacteria and current strategies to counter them were studied and the areas where PSMs can play an important role were highlighted. The use of PSMs, both as an anti-resistance and anti-virulence agent in combination therapy to counter multi-drug resistance along with their mechanisms of action, has been discussed in detail. The difficulties in the commercialisation of PSMs and strategies to overcome them along with future priority areas of research have also been given. Following the given R&D path will definitely help in better understanding and utilising the full potential of PSMs in solving the problem of antimicrobial resistance (AMR).

Electroceutical Management of Bacterial Biofilms and Surgical Infection

Significance: In the host-microbe microenvironment, bioelectrical factors influence microbes and hosts as well as host-microbe interactions. This article discusses relevant mechanistic underpinnings of this novel paradigm. It also addresses how such knowledge may be leveraged to develop novel electroceutical solutions to manage biofilm infection. Recent Advances: Systematic review and meta-analysis of several hundred wound studies reported a 78.2% prevalence of biofilms in chronic wounds. Biofilm infection is a major cause of delayed wound healing. In the host-microbe microenvironment, bioelectrical factors influence interactions between microbes and hosts. Critical Issues: Rapid biological responses are driven by electrical signals generated by ion currents moving across cell membranes. Bacterial life, growth, and function rely on a bioelectrical milieu, which when perturbed impairs their ability to form a biofilm, a major threat to health care. Electrokinetic stability of several viral particles depend on electrostatic forces. Weak electrical field strength, otherwise safe for humans, can be anti-microbial in this context. In the host, the electric field enhanced keratinocyte migration, bolstered immune defenses, improved mitochondrial function, and demonstrated multiple other effects consistent with supporting wound healing. A deeper mechanistic understanding of bioelectrical principles will inform the design of next-generation electroceuticals. Future Directions: This is an opportune moment in time as there is a surge of interest in electroceuticals in medicine. Projected to reach $35.5 billion by 2025, electroceuticals are becoming a cynosure in the global market. The World Health Organization reports that more than 50% of surgical site infections can be antibiotic resistant. Electroceuticals offer a serious alternative.

Activity of Antimicrobial Peptides and Ciprofloxacin against Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa is increasingly resistant to conventional antibiotics, which can be compounded by the formation of biofilms on surfaces conferring additional resistance. P. aeruginosa was grown in sub-inhibitory concentrations of the antimicrobial peptides (AMPs) melimine and Mel4 or ciprofloxacin for 30 consecutive days to induce the development of resistance. Antibiofilm effect of AMPs and ciprofloxacin was evaluated using crystal violet and live/dead staining with confocal microscopy. Effect on the cell membrane of biofilm cells was evaluated using DiSC(3)-5 dye and release of intracellular ATP and DNA/RNA. The minimum inhibitory concentration (MIC) of ciprofloxacin increased 64-fold after 30 passages, but did not increase for melimine or Mel4. Ciprofloxacin could not inhibit biofilm formation of resistant cells at 4× MIC, but both AMPs reduced biofilms by >75% at 1× MIC. At 1× MIC, only the combination of either AMP with ciprofloxacin was able to significantly disrupt pre-formed biofilms (≥61%; p < 0.001). Only AMPs depolarized the cell membranes of biofilm cells at 1× MIC. At 1× MIC either AMP with ciprofloxacin released a significant amount of ATP (p < 0.04), but did not release DNA/RNA. AMPs do not easily induce resistance in P. aeruginosa and can be used in combination with ciprofloxacin to treat biofilm.

Membrane potentials, oxidative stress and the dispersal response of bacterial biofilms to 405 nm light

The majority of chronic infections are caused by biofilms, which have higher levels of antibiotic resistance than planktonic growth. Violet-blue 405 nm light has recently emerged as a novel bactericide, but limited studies have been conducted on its effectiveness against biofilms. We found that in response to 405 nm light both Pseudomonas aeruginosa and Bacillus subtilis biofilms exhibited cell dispersal and membrane potential hyperpolarisations. The response to 405 nm light depended on the stage of biofilm growth. The use of reactive oxygen species scavengers reduced membrane hyperpolarisation and biofilm dispersal in response to 405 nm light. This is the first time that membrane potential hyperpolarisations have been linked with photooxidative stress in bacteria and with biofilm dispersal. These results provide a new insight into the role of membrane potentials in the bacterial stress response and could be used in the development of 405 nm light based biofilm treatments.

Electroactive 3D Printed Scaffolds Based on Percolated Composites of Polycaprolactone With Thermally Reduced Graphene Oxide for Antibacterial and Tissue Engineering Applications

Applying electrical stimulation (ES) could affect different cellular mechanisms, thereby producing a bactericidal effect and an increase in human cell viability. Despite its relevance, this bioelectric effect has been barely reported in percolated conductive biopolymers. In this context, electroactive polycaprolactone (PCL) scaffolds with conductive Thermally Reduced Graphene Oxide (TrGO) nanoparticles were obtained by a 3D printing method. Under direct current (DC) along the percolated scaffolds, a strong antibacterial effect was observed, which completely eradicated S. aureus on the surface of scaffolds. Notably, the same ES regime also produced a four-fold increase in the viability of human mesenchymal stem cells attached to the 3D conductive PCL/TrGO scaffold compared with the pure PCL scaffold. These results have widened the design of novel electroactive composite polymers that could both eliminate the bacteria adhered to the scaffold and increase human cell viability, which have great potential in tissue engineering applications.