Taking the Silver Bullet Colloidal Silver Particles for the Topical Treatment of Biofilm-Related Infections

Nanotechnology-Based Therapeutics for Airway Inflammatory Diseases

Under the concept of "one airway, one disease", upper and lower airway inflammatory diseases share similar pathogenic mechanisms and are collectively referred to as airway inflammatory diseases. With industrial development and environmental changes, the incidence of these diseases has gradually increased. Traditional treatments, including glucocorticoids, antihistamines, and bronchodilators, have alleviated much of the discomfort experienced by patients. However, conventional drug delivery routes have inherent flaws, such as significant side effects, irritation of the respiratory mucosa, and issues related to drug deactivation. In recent years, nanomaterials have emerged as excellent carriers for drug delivery and are being increasingly utilized in the treatment of airway inflammatory diseases. These materials not only optimize the delivery of traditional medications but also facilitate the administration of various new drugs that target novel pathways, thereby enhancing the treatment outcomes of inflammatory diseases. This study reviews the latest research on nano-drug delivery systems used in the treatment of airway inflammatory diseases, covering traditional drugs, immunotherapy drugs, antimicrobial drugs, plant-derived drugs, and RNA drugs. The challenges involved in developing nano-delivery systems for these diseases are discussed, along with a future outlook. This review offers new insights that researchers can utilize to advance further research into the clinical application of nano-drug delivery systems for treating airway inflammatory diseases.

Structural characteristics, functions, and counteracting strategies of biofilms in Staphylococcus aureus

Background

Staphylococcus aureus (S. aureus) is a prevalent pathogen associated with a wide range of infections, exhibiting significant antibiotic resistance and posing therapeutic challenges in clinical settings. The formation of biofilms contributes to the emergence of resistant strains, further diminishing the efficacy of antibiotics. This, in turn, leads to chronic and recurrent infections, ultimately increasing the healthcare burden. Consequently, preventing and eliminating biofilms has become a critical focus in clinical management and research.

Aim of review

This review systematically examines the mechanisms underlying biofilm formation in S. aureus and its contribution to antibiotic resistance, emphasizing the essential roles biofilms play in maintaining structural integrity and enhancing resistance. It also analyses the protective mechanisms that fortify S. aureus biofilms against antimicrobial treatments. Furthermore, the review provides a comprehensive overview of recent therapeutic innovations, including enzymatic therapy, nanotechnology, gene editing, and phage therapy.

Key scientific concepts of review

Emerging therapeutic strategies present novel approaches to combat S. aureus biofilm-associated infections through various mechanisms. This review discusses recent advancements in these therapies, their practical challenges in clinical application, and provides an in-depth analysis of each strategy's mechanisms and therapeutic potential. By mapping future research directions, this review aims to refine anti-biofilm strategies to control infection progression and effectively mitigate recurrence.

Liposomal drug delivery strategies to eradicate bacterial biofilms: Challenges, recent advances, and future perspectives

Typical antibiotic treatments are often ineffectual against biofilm-related infections since bacteria residing within biofilms have developed various mechanisms to resist antibiotics. To overcome these limitations, antimicrobial-loaded liposomal nanoparticles are a promising anti-biofilm strategy as they have demonstrated improved antibiotic delivery and eradication of bacteria residing in biofilms. Antibiotic-loaded liposomal nanoparticles revealed remarkably higher antibacterial and anti-biofilm activities than free drugs in experimental settings. Moreover, liposomal nanoparticles can be used efficaciously for the combinational delivery of antibiotics and other antimicrobial compounds/peptide which facilitate, for instance, significant breakdown of the biofilm matrix, increased bacterial elimination from biofilms and depletion of metabolic activity of various pathogens. Drug-loaded liposomes have mitigated recurrent infections and are considered a promising tool to address challenges associated to antibiotic resistance. Furthermore, it has been demonstrated that surface charge and polyethylene glycol modification of liposomes have a notable impact on their antibacterial biofilm activity. Future investigations should tackle the persistent hurdles associated with development of safe and effective liposomes for clinical application and investigate novel antibacterial treatments, including CRISPR-Cas gene editing, natural compounds, phages, and nano-mediated approaches. Herein, we emphasize the significance of liposomes in inhibition and eradication of various bacterial biofilms, their challenges, recent advances, and future perspectives.

Deciphering the dynamics of methicillin-resistant Staphylococcus aureus biofilm formation: from molecular signaling to nanotherapeutic advances

Methicillin-resistant Staphylococcus aureus (MRSA) represents a global threat, necessitating the development of effective solutions to combat this emerging superbug. In response to selective pressures within healthcare, community, and livestock settings, MRSA has evolved increased biofilm formation as a multifaceted virulence and defensive mechanism, enabling the bacterium to thrive in harsh conditions. This review discusses the molecular mechanisms contributing to biofilm formation across its developmental stages, hence representing a step forward in developing promising strategies for impeding or eradicating biofilms. During staphylococcal biofilm development, cell wall-anchored proteins attach bacterial cells to biotic or abiotic surfaces; extracellular polymeric substances build scaffolds for biofilm formation; the cidABC operon controls cell lysis within the biofilm, and proteases facilitate dispersal. Beside the three main sequential stages of biofilm formation (attachment, maturation, and dispersal), this review unveils two unique developmental stages in the biofilm formation process for MRSA; multiplication and exodus. We also highlighted the quorum sensing as a cell-to-cell communication process, allowing distant bacterial cells to adapt to the conditions surrounding the bacterial biofilm. In S. aureus, the quorum sensing process is mediated by autoinducing peptides (AIPs) as signaling molecules, with the accessory gene regulator system playing a pivotal role in orchestrating the production of AIPs and various virulence factors. Several quorum inhibitors showed promising anti-virulence and antibiofilm effects that vary in type and function according to the targeted molecule. Disrupting the biofilm architecture and eradicating sessile bacterial cells are crucial steps to prevent colonization on other surfaces or organs. In this context, nanoparticles emerge as efficient carriers for delivering antimicrobial and antibiofilm agents throughout the biofilm architecture. Although metal-based nanoparticles have been previously used in combatting biofilms, its non-degradability and toxicity within the human body presents a real challenge. Therefore, organic nanoparticles in conjunction with quorum inhibitors have been proposed as a promising strategy against biofilms. As nanotherapeutics continue to gain recognition as an antibiofilm strategy, the development of more antibiofilm nanotherapeutics could offer a promising solution to combat biofilm-mediated resistance.

Zwitterionic silver nanoparticle based antibacterial eye drops for efficient therapy of bacterial keratitis

Inefficient biofilm clearance and the risk of drug resistance pose significant challenges for antibiotic eye drops in the treatment of bacterial keratitis (BK). Recently, silver nanoparticles (AgNPs) have emerged as promising alternatives to antibiotics due to their potent antibacterial activity and minimal drug resistance. However, concerns regarding the potential biotoxicity of aggregated AgNPs in tissues have limited their practical application. In this study, polyzwitterion-functionalized AgNPs with excellent dispersion stability in the ocular physiological environment were chosen to prepare antibacterial eye drops. Zwitterionic AgNPs were synthesized using a copolymer, poly(sulfobetaine methacrylate-co-dopamine methacrylamide) (PSBDA), as a stabilizer and a reducing agent. The resulting antibacterial eye drops, named ZP@Ag-drops, demonstrated outstanding biocompatibility in in vitro cytotoxicity tests and in vivo rabbit eye instillation experiments, attributed to the zwitterionic PSBDA surface. Furthermore, the ZP@Ag-drops exhibited strong antibacterial activity against multiple pathogenic bacteria, particularly in penetrating and eradicating biofilms, due to the synergistic bactericidal effect of the released Ag+ and reactive oxygen species (ROS). Importantly, in vivo BK rabbit models showed that the ZP@Ag-drops effectively inhibited corneal infection and prevented ocular tissue damage, surpassing the therapeutic effect of commercial levofloxacin eye drops (LEV-drops). Overall, this study presents a promising alternative option for the effective treatment of BK using antibacterial eye drops.

Biological macromolecules-based nanoformulation in improving wound healing and bacterial biofilm-associated infection: A review

A chronic wound is a serious complication associated with diabetes mellitus and is difficult to heal due to high glucose levels, oxidative stress, and biofilm-associated microbial infection. The structural complexity of microbial biofilm makes it impossible for antibiotics to penetrate the matrix, hence conventional antibiotic therapies became ineffective in clinical settings. This demonstrates an urgent need to find safer alternatives to reduce the prevalence of chronic wound infection associated with microbial biofilm. A novel approach to address these concerns is to inhibit biofilm formation using biological-macromolecule based nano-delivery system. Higher drug loading efficiency, sustained drug release, enhanced drug stability, and improved bioavailability are advantages of employing nano-drug delivery systems to prevent microbial colonization and biofilm formation in chronic wounds. This review covers the pathogenesis, microbial biofilm formation, and immune response to chronic wounds. Furthermore, we also focus on macromolecule-based nanoparticles as wound healing therapies to reduce the increased mortality associated with chronic wound infections.

Colloidal silver against macrophage infections and biofilms of atypical mycobacteria

Skin and soft tissue infection (SSTI) caused by atypical mycobacteria such as Mycobacterium abscessus and Mycobacterium avium intracellulare complex (MAIC) have increased in recent years. Current therapeutic options are limited, and hence new and better therapies are urgently required. Colloidal Silver (CS) has been identified for its widespread antibacterial properties and silver-impregnated dressings have been used for SSTIs caused by various pathogens. The efficacy of Green Synthesized Colloidal Silver (GSCS) was investigated for bacterial growth inhibition (BGI) using a microdilution method and minimum biofilm eradication concentration (MBEC) using resazurin assay and confocal scanning laser microscopy (CSLM) of M. abscessus (n = 5) and MAIC (n = 5). The antibacterial effect of GSCS against M. abscessus infected macrophages was also evaluated. The in vitro cytotoxicity of GSCS on a human keratinocyte cell line (HaCaT) and neonatal foreskin fibroblasts was analyzed by the crystal violet proliferation assay. Average BGI and MBEC of GSCS varied between 0.7 and 22 ppm for M. abscessus and MAIC. The concentration of 3 ppm reduced M. abscessus-infection in macrophages significantly. GSCS was not cytotoxic to HaCaT and neonatal foreskin fibroblast cells at concentrations < 3 ppm up to 2 h exposure time. GSCS therefore, has the potential for topical application against atypical mycobacterial SSTI.

Nanotechnology-enabled topical delivery of therapeutics in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a chronic inflammatory disease of the paranasal sinuses which represents a significant health burden due to its widespread prevalence and impact on patients' quality of life. As the molecular pathways driving and sustaining inflammation in CRS become better elucidated, the diversity of treatment options is likely to widen significantly. Nanotechnology offers several tools to enhance the effectiveness of topical therapies, which has been limited by factors such as poor drug retention, mucosal permeation and adhesion, removal by epithelial efflux pumps and the inability to effectively penetrate biofilms. In this review, we highlight the successful application of nanomedicine in the field of CRS therapeutics, discuss current limitations and propose opportunities for future work.

Topical Nanotherapeutics for Treating MRSA-Associated Skin and Soft Tissue Infection (SSTIs)

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) imposes a major challenge for the treatment of infectious diseases with existing antibiotics. MRSA associated with superficial skin and soft tissue infections (SSTIs) is one of them, affecting the skin's superficial layers, and it includes impetigo, folliculitis, cellulitis, furuncles, abscesses, surgical site infections, etc. The efficient care of superficial SSTIs caused by MRSA necessitates local administration of antibiotics, because oral antibiotics does not produce the required concentration at the local site. The topical administration of nanocarriers has been emerging in the area of drug delivery due to its advantages over conventional topical formulation. It enhances the solubility and permeation of the antibiotics into deeper layer of the skin. Apart from this, antibiotic resistance is something that needs to be combated on multiple fronts, and antibiotics encapsulated in nanocarriers help to do so by increasing the therapeutic efficacy in a number of different ways. The current review provides an overview of the resistance mechanism in S. aureus as well as various nanocarriers reported for the effective management of MRSA-associated superficial SSTIs.

Investigating forthcoming strategies to tackle deadly superbugs: current status and future vision

INTRODUCTION

Superbugs are microorganisms that cause disease and have increased resistance to the treatments typically used against infections. Recently, antibiotic resistance development has been more rapid than the pace at which antibiotics are manufactured, leading to refractory infections. Scientists are concerned that a particularly virulent and lethal 'superbug' will one day join the ranks of existing bacteria that cause incurable diseases, resulting in a global health disaster on the scale of the Black Death.

AREAS COVERED

This study highlights the current developments in the management of antibiotic-resistant bacteria and recommends strategies for further regulating antibiotic-resistant microorganisms associated with the healthcare system. This review also addresses the origins, prevalence, and pathogenicity of superbugs, and the design of antibacterial against these growing multidrug-resistant organisms from a medical perspective.

EXPERT OPINION

It is recommended that antimicrobial resistance should be addressed by limiting human-to-human transmission of resistant strains, lowering the use of broad-spectrum antibiotics, and developing novel antimicrobials. Using the risk-factor domains framework from this study would assure that not only clinical but also community and hospital-specific factors are covered, lowering the chance of confounders. Extensive subjective research is necessary to fully understand the underlying factors and uncover previously unexplored areas.

The combination of diethyldithiocarbamate and copper ions is active against Staphylococcus aureus and Staphylococcus epidermidis biofilms in vitro and in vivo

Staphylococcus aureus and Staphylococcus epidermidis are associated with life-threatening infections. Despite the best medical care, these infections frequently occur due to antibiotic resistance and the formation of biofilms of these two bacteria (i.e., clusters of bacteria embedded in a matrix). As a consequence, there is an urgent need for effective anti-biofilm treatments. Here, we describe the antibacterial properties of a combination treatment of diethyldithiocarbamate (DDC) and copper ions (Cu²⁺) and their low toxicity in vitro and in vivo. The antibacterial activity of DDC and Cu²⁺ was assessed in vitro against both planktonic and biofilm cultures of S. aureus and S. epidermidis using viability assays, microscopy, and attachment assays. Cytotoxicity of DDC and Cu²⁺ (DDC-Cu²⁺) was determined using a human fibroblast cell line. In vivo antimicrobial activity and toxicity were monitored in Galleria mellonella larvae. DDC-Cu²⁺ concentrations of 8 μg/ml DDC and 32 μg/ml Cu²⁺ resulted in over 80% MRSA and S. epidermidis biofilm killing, showed synergistic and additive effects in both planktonic and biofilm cultures of S. aureus and S. epidermidis, and synergized multiple antibiotics. DDC-Cu²⁺ inhibited MRSA and S. epidermidis attachment and biofilm formation in the xCELLigence and Bioflux systems. In vitro and in vivo toxicity of DDC, Cu²⁺ and DDC-Cu²⁺ resulted in > 70% fibroblast viability and > 90% G. mellonella survival. Treatment with DDC-Cu²⁺ significantly increased the survival of infected larvae (87% survival of infected, treated larvae vs. 47% survival of infected, untreated larvae, p < 0.001). Therefore, DDC-Cu²⁺ is a promising new antimicrobial with activity against planktonic and biofilm cultures of S. epidermidis and S. aureus and low cytotoxicity in vitro. This gives us high confidence to progress to mammalian animal studies, testing the antimicrobial efficacy and safety of DDC-Cu²⁺.

Silver nanoparticles associated with a polyphosphate and fluoride enhance the prevention of enamel demineralization and impact on dual-biofilm adhesion

OBJECTIVES

The aim of this study were to produce a multifunctional nanocomposite combining silver nanoaparticles (Ag), sodium trimetaphosphate (TMP) and fluoride (F), to investigate its effect on dental enamel demineralization and on biofilms of Streptococcus mutans and Candida albicans.

METHODS

Bovine enamel blocks were submitted to five pH cycles and treated 2x/day with 100ppm F, 225ppm F, 100ppm F+0.2%TMP or 100ppm F+0.2%TMP+10% Ag (100F/TMP/Ag). Next, surface hardness loss (%SH), integrated loss of subsurface hardness (ΔKHN), enamel fluoride (F) and calcium (Ca) concentration were determined. Biofilms from single and dual species of S. mutans and C. albicans were treated with 100F/TMP/Ag, Ag or chlorhexidine gluconate for 24h. The antibiofilm effect was evaluated by colony-forming unit counting and Scanning Electron Microscopy.

RESULTS

The nanocomposite reduced 43.0% of %SH and was similar with samples treated with 225F, 100F/TMP and 100/TMP/Ag. The attribute of F and/or TMP in reducing ΔKHN in 5-20 μm was not affected by the addiction of Ag (110F = 225F = 100F/TMP = 100F/TMP/Ag > Negative Control). Further, 100F/TMP/Ag strongly reduced viable cells of S. mutans in dual biofilms (∼5 log₁₀cm²) and structurally affected the biofilms.

CONCLUSION

The 100F/TMP/F promoted a protective effect against enamel demineralization and was able to significantly inhibit the growth of biofilms of S. mutans and C. albicans.

CLINICAL SIGNIFICANCE

The focus on prevention and non-invasive dental treatment is the most effective and least costly way to improve the population's oral health conditions. We present a nanocomposite for a multiple approach in prevention of caries.

Topical Antibiofilm Agents With Potential Utility in the Treatment of Chronic Rhinosinusitis: A Narrative Review

The role of bacterial biofilms in chronic and recalcitrant diseases is widely appreciated, and the treatment of biofilm infection is an increasingly important area of research. Chronic rhinosinusitis (CRS) is a complex disease associated with sinonasal dysbiosis and the presence of bacterial biofilms. While most biofilm-related diseases are associated with highly persistent but relatively less severe inflammation, the presence of biofilms in CRS is associated with greater severity of inflammation and recalcitrance despite appropriate treatment. Oral antibiotics are commonly used to treat CRS but they are often ineffective, due to poor penetration of the sinonasal mucosa and the inherently antibiotic resistant nature of bacteria in biofilms. Topical non-antibiotic antibiofilm agents may prove more effective, but few such agents are available for sinonasal application. We review compounds with antibiofilm activity that may be useful for treating biofilm-associated CRS, including halogen-based compounds, quaternary ammonium compounds and derivatives, biguanides, antimicrobial peptides, chelating agents and natural products. These include preparations that are currently available and those still in development. For each compound, antibiofilm efficacy, mechanism of action, and toxicity as it relates to sinonasal application are summarised. We highlight the antibiofilm agents that we believe hold the greatest promise for the treatment of biofilm-associated CRS in order to inform future research on the management of this difficult condition.

Nanomaterials enabling clinical translation of antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (aPDT) has emerged as a promising approach to aid the fight against looming antibiotic resistance. aPDT harnesses the energy of light through photosenstizers to generate highly reactive oxygen species that can inactivate bacteria and fungi with no resistance. To date aPDT has shown great efficacy against microbes causing localized infections in the skin and the oral cavity. However, its wide application in clinical settings has been limited due to both physicochemical and biological challenges. Over the past decade nanomaterials have contributed to promoting photosensitizer performance and aPDT efficiency, yet further developments are required to establish accredited treatment options. In this review we discuss the challenges facing the clinical application of aPDT and the opportunities that nanotechnology may offer to promote the safety and efficiency of aPDT.

A one-pot synthesis of PEGylated plasmonic WO3−x@Eugenol nanoflowers with NIR-controllable antioxidant activities for synergetically combating bacterial biofilm infection

Schematic diagram of dual treatment of bacterial infection.

Facile Biofilm Penetration of Cationic Liposomes Loaded with DNase I/Proteinase K to Eradicate Cutibacterium acnes for Treating Cutaneous and Catheter Infections

Background

The biofilm produced by Cutibacterium acnes is a major infection threat for skin and implanted catheters. Nanoparticles provide a new approach to eradicate biofilms. The present study evaluated the capability of cationic liposomes loaded with DNase I (DNS) and proteinase K (PK) to remove preformed C. acnes biofilms.

Methods

DNS and PK were able to target and disassemble the biofilm by degrading extracellular polymer substances (EPS). Soyaethyl morpholinium ethosulfate (SME) was used to render a positive charge and enhance the antibacterial activity of the liposomes.

Results

The cationic liposomes containing enzymes yielded monodisperse nanovesicles ranging between 95 and 150 nm. The entrapment efficiency of the enzymes in the liposomes achieved a value of 67–83%. All liposomal formulations suppressed planktonic C. acnes growth at a minimum inhibitory concentration (MIC) equal to the free SME in the solution. The enzyme in the liposomal form inhibited biofilm growth much better than that in the free form, with the dual enzyme-loaded liposomes demonstrating the greatest inhibition of 54% based on a crystal violet assay. The biofilm-related virulence genes PA380 and PA1035 were downregulated by the combined enzymes in the liposomes but not the individual DNS or PK. Scanning electron microscopy (SEM) and confocal microscopy displayed reduced C. acnes aggregates and biofilm thickness by the liposomal system. The liposomes could penetrate through about 85% of the biofilm thickness. The in vitro pig skin permeation also showed a facile delivery of liposomes into the epidermis, deeper skin strata, and hair follicles. The liposomes exhibited potent activity to eliminate C. acnes colonization in mouse skin and catheters in vivo. The colony-forming units (CFUs) in the catheter treated with the liposomes were reduced by 2 logs compared to the untreated control.

Conclusion

The data suggested a safe application of the enzyme-loaded cationic liposomes as antibacterial and antibiofilm agents.

The Antibiofilm Nanosystems for Improved Infection Inhibition of Microbes in Skin

Biofilm formation is an important virulence factor for the opportunistic microorganisms that elicit skin infections. The recalcitrant feature of biofilms and their antibiotic tolerance impose a great challenge on the use of conventional therapies. Most antibacterial agents have difficulty penetrating the matrix produced by a biofilm. One novel approach to address these concerns is to prevent or inhibit the formation of biofilms using nanoparticles. The advantages of using nanosystems for antibiofilm applications include high drug loading efficiency, sustained or prolonged drug release, increased drug stability, improved bioavailability, close contact with bacteria, and enhanced accumulation or targeting to biomasses. Topically applied nanoparticles can act as a strategy for enhancing antibiotic delivery into the skin. Various types of nanoparticles, including metal oxide nanoparticles, polymeric nanoparticles, liposomes, and lipid-based nanoparticles, have been employed for topical delivery to treat biofilm infections on the skin. Moreover, nanoparticles can be designed to combine with external stimuli to produce magnetic, photothermal, or photodynamic effects to ablate the biofilm matrix. This study focuses on advanced antibiofilm approaches based on nanomedicine for treating skin infections. We provide in-depth descriptions on how the nanoparticles could effectively eliminate biofilms and any pathogens inside them. We then describe cases of using nanoparticles for antibiofilm treatment of the skin. Most of the studies included in this review were supported by in vivo animal infection models. This article offers an overview of the benefits of nanosystems for treating biofilms grown on the skin.

ISMN-loaded PLGA-PEG nanoparticles conjugated with anti-Staphylococcus aureus α-toxin inhibit Staphylococcus aureus biofilms in chronic rhinosinusitis

Background: Staphylococcus aureus biofilms were linked to negative postsurgical outcomes of chronic rhinosinusitis (CRS). This study aims to develop a targeted nanoparticle and characterize its bactericidal effects. Methods: The authors prepared ISMN-loaded poly-lactide-co-glycolide acid (PLGA) and polyethylene glycol (PEG) nanoparticles conjugated with anti-S. aureus α-toxin (AA; ISMN-PLGA-PEG-AA), and determined its bactericidal and toxic effects. The antibiofilm propriety of ISMN-PLGA-PEG-AA was further investigated in a sheep CRS model. Results: ISMN-PLGA-PEG-AA had no toxic effect, while ISMN, ISMN-PLGA-PEG and ISMN-PLGA-PEG-AA had significantly anti-S. aureus effects. The blood concentrations and mRNA levels in sinus tissues of IL-4, IL-8 and IFN-γ in the sheep CRS model were significantly low. Conclusion: ISMN-PLGA-PEG-AA can effectively inhibit S. aureus biofilm, and is a promising drug for CRS treatment.

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.

Polymeric micelles with anti-virulence activity against Candida albicans in a single- and dual-species biofilm

Infections caused by fungal biofilms with rapidly evolving resistance against the available antifungal agents are difficult to manage. These difficulties demand new strategies for effective eradication of biofilms from both biological and inert surfaces. In this study, polymeric micelles comprised of di-block polymer, poly-(ethylene glycol) methyl ether methacrylate and poly 2-(N,N-diethylamino) ethyl methacrylate polymer, P(PEGMA-b-DEAEMA), were observed to exhibit remarkable inhibitory effects on hyphal growth of Candida albicans (C. albicans) and C. tropicalis, thus preventing biofilm formation and removing existing biofilms. P(PEGMA-b-DEAEMA) micelles showed biofilm removal efficacy of > 40% and a 1.4-log reduction in cell viability of C. albicans in its single-species biofilms. In addition, micelles alone promoted high removal percentage in a mixed biofilm of C. albicans and C. tropicalis (~ 70%) and remarkably reduced cell viability of both strains. Co-delivery of fluconazole (Flu) and amphotericin B (AmB) with micelles showed synergistic effects on C. albicans biofilms (3-log reduction for AmB and 2.2-log reduction for Flu). Similar effects were noted on C. albicans planktonic cells when treated with the micellar system combined with AmB but not with Flu. Moreover, micelle-drug combinations showed an enhancement in the antibiofilm activity of Flu and AmB against dual-species biofilms. Furthermore, in vivo studies using Caenorhabditis elegans nematodes revealed no obvious toxicity of the micelles. Targeting morphologic transitions provides a new strategy for defeating fungal biofilms of polymorphic resistance strains and can be potentially used in counteracting Candida virulence.

Colloidal silver combating pathogenic Pseudomonas aeruginosa and MRSA in chronic rhinosinusitis

The emergence of antibiotic resistant bacteria requires for the development of new antimicrobial compounds one of which colloidal silver (CS) having strong bactericidal properties and being the most promising inorganic nanoparticles for the treatment of bacterial infectious diseases. However, their production can be slow and cumbersome. Here, we used Corymbia maculata aqueous leaf extract as a reducing agent to synthesize CS in a single 15-minute process. CS was physico-chemically characterized for shape, size, zeta potential and stability. The Minimal Inhibitory Concentration (MIC) and Minimum Biofilm Eradication Concentration (MBEC) of CS against planktonic and biofilm forms of methicillin-resistant Staphylococcus aureus (MRSA, n = 5), Pseudomonas aeruginosa (n = 5), Haemophilus influenzae (n = 5) and Streptococcus pneumoniae (n = 3) chronic rhinosinusitis clinical isolates were investigated using the microdilution method and resazurin assay, respectively. The in vitro cytotoxicity on bronchial epithelial cells (Nuli-1) was analyzed by the crystal violet proliferation assay. The safety and efficacy of CS was evaluated in an in vivo infection model in Caenorhabditis elegans. CS was spherical in shape with a diameter of between 11-16 nm (TEM analysis) in dried form and 40 nm (NanoSight) in colloidal form and was stable at room temperature and 4 °C for one year. Average MIC and MBEC values varied between 11 and 44 ppm for MRSA, H. influenzae and S. pneumoniae and between 0.2 and 3 ppm for P. aeruginosa. CS was not toxic to Nuli-1 cells or C. elegans at concentrations of 44 ppm and reduced the Colony Forming Units counts by 96.9 % and 99.6 % in C. elegans for MRSA and P. aeruginosa, respectively. In conclusion, a novel, green synthesis of stable CS is demonstrated with good safety and efficacy profiles, particularly against P. aeruginosa in planktonic and biofilm forms. These CS have potential applications against clinical infections, including in the context of CRS.

Hierarchical Assembly of Nanodimensional Silver-Silver Oxide Physical Gels Controlling Nosocomial Infections

Microbial infections originating from medical care facilities are raising serious concerns across the globe. Therefore, nanotechnology-derived nanostructures have been investigated and explored due to their promising characteristics. In view of this, silver-based antimicrobial hydrogels as an alternative to antibiotic-based creams could play a crucial role in combating such infections. Toward this goal, we report a simple method for the synthesis and assembly of silver nanoparticles in a biopolymer physical gel derived from Abroma augusta plant in imparting antimicrobial properties against nosocomial pathogens. Synthesized silver nanoparticles (diameter, 30 ± 10 nm) were uniformly distributed inside the hydrogel. Such synthesized hydrogel assembly of silver nanoparticles dispersed in the biopolymer matrix exhibited hemocompatibility and antimicrobial and antibiofilm characteristics against nosocomial pathogens. The developed hydrogel as a surface coating offers reduced hardness and modulus value, thereby minimizing the brittleness tendency of the gel in the dried state. Hence, we believe that the hierarchical assembly of our hydrogel owing to its functional activity, host toxicity, and stability could possibly be used as an antimicrobial ointment for bacterial infection control.

Best served small: nano battles in the war against wound biofilm infections

The global challenge of antimicrobial resistance is of increasing concern, and alternatives to currently used antibiotics or methods to improve their stewardship are sought worldwide. Microbial biofilms, complex 3D communities of bacteria and/or fungi, are difficult to treat with antibiotics for several reasons. These include their protective coats of extracellular matrix proteins which are difficult for antibiotics to penetrate. Nanoparticles (NP) are one way to rise to this challenge; whilst they exist in many forms naturally there has been a profusion in synthesis of these small (<100 nm) particles for biomedical applications. Their small size allows them to penetrate the biofilm matrix, and as well as some NP being inherently antimicrobial, they also can be modified by doping with antimicrobial payloads or coated to increase their effectiveness. This mini-review examines the current role of NP in treating wound biofilms and the rise in multifunctionality of NP.

Ultrasmall AgNP-Impregnated Biocompatible Hydrogel with Highly Effective Biofilm Elimination Properties

Ultrasmall silver nanoparticles (AgNPs; size < 3 nm) have attracted a great deal of interest as an alternative to commercially available antibiotics due to their ability to eliminate a wide range of microbial pathogens. However, most of these ultrasmall AgNPs are highly reactive and unstable, as well as susceptible to fast oxidation. Therefore, both the stability and toxicity remain major shortcomings for their clinical application and uptake. To circumvent these problems, we present a novel strategy to impregnate ultrasmall AgNPs into a biocompatible thermosensitive hydrogel that enables controlled release of silver alongside long-term storage stability and highly potent antibacterial activity. The advantage of this strategy lies in the combination of a homogenous dispersion of AgNPs in a hydrogel network, which serves as a sustained-release reservoir, and the unique feature of ultrasmall AgNP size, which provides an improved biofilm eradication capacity. The superior biofilm dispersion properties of the AgNP hydrogel is demonstrated in both single-species and multispecies biofilms, eradicating ∼80% of established biofilms compared to untreated controls. Notably, the effective antibacterial concentration of the formulation shows minimal toxicity to human fibroblasts and keratinocytes. These findings present a promising novel strategy for the development of AgNP hydrogels as an efficient antibacterial platform to combat resistant bacterial biofilms associated with wound infections.

Nanoparticulate drug-delivery systems for fighting microbial biofilms: from bench to bedside

Biofilms are highly tolerant to antimicrobial agents and adverse environmental conditions being important reservoirs for chronic and hard-to-treat infections. Nanomaterials exhibit microbiostatic/microbicidal/antipathogenic properties and can be also used for the delivery of antibiofilm agents. However, few of the many promising leads offered by nanotechnology reach clinical studies and eventually, become available to clinicians. The aim of this paper was to review the progress and challenges in the development of nanotechnology-based antibiofilm drug-delivery systems. The main identified challenges are: most papers report only in vitro studies of the activity of different nanoformulations; lack of standardization in the methodological approaches; insufficient collaboration between material science specialists and clinicians; paucity of in vivo studies to test efficiency and safety.

Antibacterial Activity of Colloidal Silver against Gram-Negative and Gram-Positive Bacteria

Due to the emergence of antimicrobial resistance, new alternative therapies are needed. Silver was used to treat bacterial infections since antiquity due to its known antimicrobial properties. Here, we aimed to evaluate the in vitro activity of colloidal silver (CS) against multidrug-resistant (MDR) Gram-negative and Gram-positive bacteria. A total of 270 strains (Acinetobacter baumannii (n = 45), Pseudomonas aeruginosa (n = 25), Escherichia coli (n = 79), Klebsiella pneumoniae (n = 58)], Staphylococcus aureus (n = 34), Staphylococcus epidermidis (n = 14), and Enterococcus species (n = 15)) were used. The minimal inhibitory concentration (MIC) of CS was determined for all strains by using microdilution assay, and time-kill curve assays of representative reference and MDR strains of these bacteria were performed. Membrane permeation and bacterial reactive oxygen species (ROS) production were determined in presence of CS. CS MIC₉₀ was 4-8 mg/L for all strains. CS was bactericidal, during 24 h, at 1× and 2× MIC against Gram-negative bacteria, and at 2× MIC against Gram-positive bacteria, and it did not affect their membrane permeabilization. Furthermore, we found that CS significantly increased the ROS production in Gram-negative with respect to Gram-positive bacteria at 24 h of incubation. Altogether, these results suggest that CS could be an effective treatment for infections caused by MDR Gram-negative and Gram-positive bacteria.

Future topical medications in chronic rhinosinusitis

BACKGROUND

Research has progressed rapidly in recent decades to better understand the etiopathogenesis and management paradigms of chronic rhinosinusitis (CRS). Although oral antibiotics often mitigate symptoms in acute CRS exacerbations, eradication of polymicrobial biofilms and multidrug-resistant bacteria remains a challenge. The goal of this review is to summarize and discuss the potential and pitfalls of topical medications in the treatment of CRS.

METHODS

A related literature review was performed using PubMed and Scopus, with only the English database included.

RESULTS

The main therapies were selected and separated in sections. Details regarding future topical treatments of CRS were summarized and discussed.

CONCLUSION

The ease of access of the sinonasal mucosa positions CRS as a disease with high potential for local topical treatment. The ultimate adoption of topical agents will require continued expansion of our understanding of novel local targets in CRS as well as improved methods to deliver and retain the drug of interest at the site of activity.

Inhibition of Staphylococcus aureus and Pseudomonas aeruginosa biofilms by quatsomes in low concentrations

Staphylococcus aureus and Pseudomonas aeruginosa are primary pathogens in chronic rhinosinusitis (CRS), and the presence of S. aureus and P. aeruginosa biofilms has been associated with negative outcomes after surgery. This study investigated the inhibition effect of cetylpyridinium chloride (CPC)-quatsomes at low concentrations on both S. aureus and P. aeruginosa biofilms in vitro , as well as their toxicities towards cultured human airway epithelial (NuLi-1) cells. S. aureus ATCC 25923 and P. aeruginosa ATCC 15692 were used to establish biofilms. CPC-quatsome and CPC micelle solutions at concentrations of 0.01%, 0.025%, and 0.05% were prepared. AlamarBlue was used to test the viability of both planktonic S. aureus and P. aeruginosa and their biofilms after treatment for 5 min and 2 h, respectively. Confocal laser scanning microscopy (CLSM) was used to investigate the interactions between CPC-quatsomes and S. aureus and P. aeruginosa biofilms. A lactate dehydrogenase (LDH) assay was used to determine the toxicity of CPC-quatsomes on NuLi-1 cells. CPC-quatsome and CPC micelle solutions had significant inhibition effects at all tested concentrations on planktonic S. aureus and P. aeruginosa and their biofilms after 5-min exposure (P  <  0.05). In the CLSM study, different interactions between CPC-quatsomes and S. aureus or P. aeruginosa biofilms were observed. After 2-h treatment, the size of S. aureus biofilms decreased, while the number of dead bacteria increased in P. aeruginosa biofilms. Neither CPC-quatsomes nor CPC micelle solutions showed significant toxicity on NuLi-1 cell at all tested CPC concentrations (P  <  0.05). CPC-quatsomes at low concentrations inhibited S. aureus and P. aeruginosa in both planktonic form and biofilms. No adverse effects on NuLi-1 cells were observed, indicating their promising potential in the treatment of CRS.

Enzyme responsive copolymer micelles enhance the anti-biofilm efficacy of the antiseptic chlorhexidine

Staphylococcal biofilms cause many infectious diseases and are highly tolerant to the effects of antimicrobials; this is partly due to the biofilm matrix, which acts as a physical barrier retarding the penetration and reducing susceptibility to antimicrobials, thereby decreasing successful treatment outcomes. In this study, both single and mixed micellar systems based on poly vinyl caprolactam (PCL)-polyethylene glycol (PEG) copolymers were optimised for delivery of chlorhexidine (CHX) to S. aureus, MRSA and S. epidermidis biofilms and evaluated for their toxicity using Caenorhabditis elegans. The respective polyethylene glycol (PEG) and poly vinyl caprolactam (PCL) structural components promoted stealth properties and enzymatic responsive release of CHX inside biofilms, leading to significantly enhanced penetration (56%) compared with free CHX and improving the efficacy against Staphylococcus aureus biofilms grown on an artificial dermis (2.4 log reduction of CFU). Mixing Soluplus-based micelles with Solutol further enhanced the CHX penetration (71%) and promoted maximum reduction in biofilm biomass (>60%). Nematodes-based toxicity assay showed micelles with no lethal effects as indicated by their high survival rate (100%) after 72 h exposure. This study thus demonstrated that bio-responsive carriers can be designed to deliver a poorly water-soluble antimicrobial agent and advance the control of biofilm associated infections.

Colloidal Silver Induces Cytoskeleton Reorganization and E-Cadherin Recruitment at Cell-Cell Contacts in HaCaT Cells

Up until the first half of the 20th century, silver found significant employment in medical applications, particularly in the healing of open wounds, thanks to its antibacterial and antifungal properties. Wound repair is a complex and dynamic biological process regulated by several pathways that cooperate to restore tissue integrity and homeostasis. To facilitate healing, injuries need to be promptly treated. Recently, the interest in alternatives to antibiotics has been raised given the widespread phenomenon of antibiotic resistance. Among these alternatives, the use of silver appears to be a valid option, so a resurgence in its use has been recently observed. In particular, in contrast to ionic silver, colloidal silver, a suspension of metallic silver particles, shows antibacterial activity displaying less or no toxicity. However, the human health risks associated with exposure to silver nanoparticles (NP) appear to be conflicted, and some studies have suggested that it could be toxic in different cellular contexts. These potentially harmful effects of silver NP depend on various parameters including NP size, which commonly range from 1 to 100 nm. In this study, we analyzed the effect of a colloidal silver preparation composed of very small and homogeneous nanoparticles of 0.62 nm size, smaller than those previously tested. We found no adverse effect on the cell proliferation of HaCaT cells, even at high NP concentration. Time-lapse microscopy and indirect immunofluorescence experiments demonstrated that this preparation of colloidal silver strongly increased cell migration, re-modeled the cytoskeleton, and caused recruitment of E-cadherin at cell-cell junctions of human cultured keratinocytes.

Long-Term Prevention of Bacterial Infection and Enhanced Osteoinductivity of a Hybrid Coating with Selective Silver Toxicity

Antibacterial and osteogenic design is required for ideal orthopedic implants. The excellent antimicrobial performance of silver nanoparticles (AgNPs) has attracted interest for the treatment of implant-related infections. However, the dose-dependent cytotoxicity of silver and its negative impact on bone implants restrict the further use of AgNPs coatings. Therefore, a hybrid coating containing polydopamine (PDA), hydroxyapatite (HA), AgNPs, and chitosan (CS) is prepared. Organic chelators CS and PDA that have promising biocompatibility are used to prevent the rapid release of silver ions from the AgNPs coating. The double chelating effect of PDA and CS significantly reduces silver ion release from the hybrid coating. The coating exhibits excellent anti-biofilm efficiency of 91.7%, 89.5%, and 92.0% for Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli, respectively. In addition, the coating can significantly stimulate osteogenic differentiation of MC3T3-E1 cells and promote bone-implant osseointegration in vivo as compared to that in the control group. The longitudinal biosafety of the coating is confirmed in vivo by histological evaluation and blood tests. The results of this study indicate that the hybrid coating exhibits antibacterial properties as well as allow bone-implant osseointegration, thereby providing insight into the design of multifunctional implants for long-term orthopedic applications.

Synergistic Anti-MRSA Activity of Cationic Nanostructured Lipid Carriers in Combination With Oxacillin for Cutaneous Application

Nanoparticles have become a focus of interest due to their ability as antibacterial agents. The aim of this study was to evaluate the anti-methicillin-resistant Staphylococcus aureus (MRSA) activity of cationic nanostructured lipid carriers (NLC) combined with oxacillin against ATCC 33591 and clinical isolate. The cationic resource on the NLC surface was soyaethyl morpholinium ethosulfate (SME). NLC loaded with oxacillin was produced to assess the antibacterial activity and the effectiveness of topical application for treating cutaneous infection. The hydrodynamic diameter and zeta potential of oxacillin-loaded NLC were 177 nm and 19 mV, respectively. When combined with NLC, oxacillin exhibited synergistic MRSA eradication. After NLC encapsulation, the minimum bactericidal concentration (MBC) of oxacillin decreased from 250 to 62.5 μg/ml. The combined NLC and oxacillin reduced the MRSA biofilm thickness from 31.2 to 13.0 μm, which was lower than the effect of NLC (18.2 μm) and antibiotic (25.2 μm) alone. The oxacillin-loaded NLC showed significant reduction in the burden of intracellular MRSA in differentiated THP-1 cells. This reduction was greater than that achieved with individual treatment. The mechanistic study demonstrated the ability of cationic NLC to disrupt the bacterial membrane, leading to protein leakage. The cell surface disintegration also increased oxacillin delivery into the cytoplasm, activating the bactericidal process. Topical NLC treatment of MRSA abscess in the skin decreased the bacterial load by log 4 and improved the skin’s architecture and barrier function. Our results demonstrated that a combination of nanocarriers and an antibiotic could synergistically inhibit MRSA growth.

Application of cationic polymer micelles for the dispersal of bacterial biofilms

Contamination of surfaces in hospitals and food industry by bacterial biofilms is a serious health risk. Of concern is their resistance to routine antibacterials and disinfectants. This requires the development of novel approaches to biofilm detachment. The study evaluates the effectiveness of cationic polymer micelles (CPMs) against pre-formed biofilms. CPMs based on different polycations were used. The hydrodynamic radius of the particles ranged from 16 to 360 nm. Biofilms of Escherichia coli 420, Pseudomonas aeruginosa PAO1, Staphylococcus aureus 29213 and Bacillus subtilis 168 were cultivated for 24 h then the pre-formed biofilms were treated with the CPMs for 2, 4 or 6 h. Biofilm biomass was evaluated by the crystal violet assay, and live/dead fluorescence test was applied for bacterial viability. The ability of CPMs to interact with pre-formed biofilms of the model strains was evaluated. We observed that the most effective CPMs were those based on poly(2-(dimethylamino)ethyl methacrylate) copolymers which reduced the biofilm biomass three- to four-fold compared with the treatment of the biofilm with water. Significantly reduced vitality of the bacteria in the biofilms was registered by the live/dead stain. The results indicate the applicability of the CPMs for disinfection of biofilm-contaminated surfaces and the treatment of wounds.

Topical Colloidal Silver for the Treatment of Recalcitrant Chronic Rhinosinusitis

Background: The management of recalcitrant chronic rhinosinusitis (CRS) is challenged by difficult-to-treat polymicrobial biofilms and multidrug resistant bacteria. This has led to the search for broad-spectrum non-antibiotic antimicrobial therapies. Colloidal silver (CS) has significant antibiofilm activity in vitro and in vivo against S. aureus, MRSA, and P. aeruginosa. However, due to the lack of scientific efficacy, it is only currently used as an alternative medicine. This is the first study looking at the safety and efficacy of CS in recalcitrant CRS.

Methods: Patients were included when they had previously undergone endoscopic sinus surgery and presented with signs and symptoms of sinus infection with positive bacterial cultures. Twenty-two patients completed the study. Patients were allocated to 10–14 days of culture directed oral antibiotics with twice daily saline rinses (n = 11) or 10 days of twice daily 0.015 mg/mL CS rinses (n = 11). Safety observations included pre- and post-treatment serum silver levels, University of Pennsylvania Smell Identification Test (UPSIT) and adverse event (AE) reporting. Efficacy was assessed comparing microbiology results, Lund Kennedy Scores (LKS) and symptom scores using Visual Analog Scale (VAS) and Sino-Nasal Outcome Test (SNOT-22).

Results: CS demonstrated good safety profile with no major adverse events, no changes in UPSIT and transient serum silver level changes in 4 patients. CS patients had 1/11 (9.09%) negative cultures, compared to 2/11 (18.18%) in the control group upon completion of the study. Whilst not statistically significant, both groups showed similar improvement in symptoms and endoscopic scores.

Conclusion: This study concludes that twice daily CS (0.015 mg/mL) sinonasal rinses for 10 days is safe but not superior to culture-directed oral antibiotics. Further studies including more patients and looking at longer treatment or improving the tonicity of the solution for better tolerability should be explored.