Long-term Antibacterial Efficacy Research Articles

Ultrasonic Vibration assisted Silver Integration by Powder Mixed EDM for Antibacterial Surfaces

Powder mixed electrical discharge machining (PMEDM) with silver nano-powder has demonstrated its potential capability in antibacterial surface modification. Analyses in the cross-sectional layer showed that silver was mainly integrated near the topmost surface layer, and its content is reduced within the layer towards the substrate. However, to achieve a long-term antibacterial efficacy, silver needs to be deeply integrated in the modified layer.Previous studies indicated that ultrasonic vibration (UV) assisted PMEDM can homogenize the silver content in the deposited layer. In this study, the effect of UV on the silver distribution within the modified layer is investigated. Ti6Al4V workpieces were stimulated by UV with a frequency of 22.3 kHz and an amplitude of 2.5 µm. Hydrocarbon-based dielectric fluid, mixed with silver nano-powder with concentrations up to 15 g/L, were internally flushed through a hollow tool with a pressure of 4 bar. PMEDM without UV was investigated for comparison. The layer thickness, micro-cracks and the cross-sectional distribution of deposited silver were analysed by confocal microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Results indicate that applying UV leads to the highest silver content in the middle region of the layer, a significant decrease of micro-cracks and a slight reduction of the layer thickness.

Long-Term Antibacterial Efficacy of Cetylpyridinium Chloride-Montmorillonite Containing PMMA Resin Cement.

Despite being able to adhesively restore teeth, adhesives and cement do not possess any anticariogenic protection potential, by which caries recurrence may still occur and reduce the clinical lifetime of adhesive restorations. Several antibacterial agents have been incorporated into dental adhesives and cement to render them anticariogenic. Due to an additional therapeutic effect, such materials are classified as 'dental combination products' with more strict market regulations. We incorporated cetylpyridinium chloride (CPC), often used for oral hygiene applications, into montmorillonite (CPC-Mont), the latter to serve as a carrier for controlled CPC release. CPC-Mont incorporated into tissue conditioner has been approved by the Pharmaceuticals and Medical Devices Agency (PmontMDA) in Japan. To produce a clinically effective dental cement with the antibacterial potential to prevent secondary caries, we incorporated CPC-Mont into PMMA resin cement. We measured the flexural strength, shear bond strength onto dentin, CPC release, and the biofilm-inhibition potential of the experimental CPC-Mont-containing PMMA cement. An 8 and 10 wt% CPC-Mont concentration revealed the antibacterial potential without reducing the mechanical properties of the PMMA cement.

Efficacy of Cold Atmospheric Plasma Therapy on Chronic Wounds: An Updated Systematic Review and Meta-Analysis of RCTs.

Objective A previous meta-analysis has revealed that cold atmospheric plasma (CAP) might not be clinically beneficial to chronic wounds. However, several new randomized controlled trials (RCTs) reported that CAP was an effective treatment option for accelerating wound healing in chronic wounds. The purpose of this review is to incorporate these new results and evaluate the efficacy of CAP in chronic wounds. Methods The major databases, including PubMed, Embase, Cochrane Library, and Web of Science, were searched for articles related to CAP treatment in chronic wounds until March 21, 2022. The literature retrieval and evaluation were carried out by two independent researchers. Result A total of 13 randomized clinical trials published between 2010 and 2022 were finally included. CAP therapy showed to be more effective in reducing the area of wounds (mean difference (MD): -1.74, 95%; confidence interval (CI): [-3.14, -0.33], p = 0.02), compared with non-CAP treatments. The immediate reduction of the bacterial load was higher in the CAP group than in the control group. (MD: -0.37, 95%; CI: [-0.7, -0.05], p = 0.02). Conclusion No significant changes were found in long-term antibacterial efficacy and pain perception between the two groups. However, more RCTs of excellent methodological quality are required to confirm technical details of the source of AP and the appropriate duration of the treatment with plasma.

Antimicrobial properties of Theruptor 3D-hydrocellular wound dressing: An in vitro study

BackgroundColonized wound infections become a major public health concern. Infections may lead to delayed healing process or severe complications. Thus, the incorporation of antimicrobial agents such as silver, iodine, etc., into the dressing material provides protection against microbes. However, these agents have limited functional usage. Recently, Dimethyl tetradecyl [3-(trimethoxysilyl)propyl] ammonium chloride (DTAC) based 3D-hydrocellular wound dressings have emerged. Therefore, we evaluated the short- and long-term antibacterial efficacy of Theruptor 3D-hydrocellular wound dressing. MethodsThe antimicrobial activity of the dressing was evaluated using modified method of AATCC100. Inoculums of 27 differential microbes including gram-positive bacteria, gram-negative bacteria, and fungus were obtained. The fabric samples were inoculated with a different microbial sample in a sterile petri plate. The samples were incubated for short (1 min, 30 min, 1h, and 4h) and long (7, 14, and 28 days) term durations. ResultsInitially, the growth of test microorganisms ranged between 7.9 × 106 to 2.38 × 107 CFU/ml at 0 min. After respective time intervals, the growth of all the tested microbes was significantly reduced in a time-dependent manner (p < 0.05). The dressing material achieved zero CFU/ml at 4 h. Moreover, it showed a significant reduction of >5 log at 1 h till 28 days. ConclusionBased on the “physical kill mechanism”, Theruptor 3D-hydrocellular wound dressing not only provides protection against a broad spectrum of pathogens but for a wide-ranging time period i.e., 1 min to 28 days that ensures effective and significant wound healing. Thus, it may consider as a promising advancement in the wound care settings.

Emerging nanomaterials for antibacterial textile fabrication.

In recent times, the search for innovative material to fabricate smart textiles has been increasing to satisfy the expectation and needs of the consumers, as the textile material plays a key role in the evolution of human culture. Further, the textile materials providean excellent environment for themicrobes to grow, because oftheir large surface area and ability to retain moisture. In addition, the growth of harmful bacteria on the textile material not only damages them but also leads to intolerable foul odour and significant danger to public health. In particular, the pathogenic bacteria present in the fabric surface can cause severe skin infections such as skin allergy and irritation via direct human contact and even can lead to heart problems and pneumonia in certain cases. Recently, nanoparticles and nanomaterials play a significant role in textile industries for developing functional smart textiles with self-cleaning, UV-protection, insect repellent, waterproof, anti-static, flame-resistant and antimicrobial-resistant properties. Thus, this review is an overview of various textile fibres that favour bacterial growth and potential antibacterial nanoparticles that can inhibit the growth of bacteria on fabric surfaces. In addition, the probable antibacterial mechanism of nanoparticles and the significance of the fabric surface modification and fabric finishes in improving the long-term antibacterial efficacy of nanoparticle-coated fabrics were also discussed.

Self-assembled nanogels of luminescent thiolated silver nanoclusters and chitosan as bactericidal agent and bacterial sensor

Multifunctional theranostic agents with the features of good biocompatibility, long-term antibacterial efficacy, and rapid bacterial detection are the desired future medicine for infectious diseases, but which poses huge challenges on the design of such multifunctional nanocomposites in a single entity. Herein, self-assembled nanogels of thiolated silver nanoclusters (Ag NCs) and chitosan was designed and synthesized, which combines the desirable biocompatible, targeting specific, luminescent properties. This nanogel displays an amplified luminescence via strong matrix-ligand coordination between thiolate ligands and chitosan matrix to rigidify the molecular structure on the surface of Ag NCs. Concomitantly, this nanogel exhibits exceptional bactericidal activity, with approximately >10-fold stronger activity compared to its counterpart Ag NCs. Furthermore, a bacterial detection system was developed based on the bacterial binding on the fluorescent nanogels. This work provides a new strategy in designing multifunctional theranostic agents and this new composite Ag NC nanogel holds great promise for practical applications as the theranostic nanomedicines.

Rechargeable anti-microbial adhesive formulation containing cetylpyridinium chloride montmorillonite

Long-term anti-bacterial effect is a desired ability of any dental material in combating tooth caries as one of the most common and widespread persistent diseases today. Among several cationic quaternary ammonium compounds with antiseptic properties, cetylpyridinium chloride (CPC) is often used in mouthrinses and toothpastes. In this study, we incorporated CPC in a soft phyllosilicate mineral (clay), referred to as montmorillonite (Mont), to enable gradual CPC release with rechargeability. Besides measuring CPC release and recharge, we examined the anti-bacterial effect, cytotoxicity and bonding effectiveness of five experimental adhesive formulations, prepared by adding 1 and 3 wt% CPC_Mont, 3 wt% Mont (without CPC), and 1 and 3 wt% CPC (without Mont) to the commercial adhesive Clearfil S3 Bond ND Quick (‘C-S3B’; Kuraray Noritake). Strong inhibition of Streptococcus mutans biofilm formation by CPC_Mont adhesives was confirmed by optical density and SEM. CPC release from CPC_Mont adhesives was higher and lasted longer than from CPC adhesives, while CPC_Mont adhesives could also be recharged with CPC upon immersion in 2 wt% CPC. In conclusion, CPC_Mont technology rendered adhesives anti-bacterial properties with recharge ability, this without reducing its bonding potential, neither increasing its cytotoxicity. Statement of significanceDental caries is one of the most prevalent chronic diseases in the population worldwide and is the major cause of tooth loss. In this study, we developed cetylpyridinium chloride (CPC) loaded montmorillonite (CPC-Mont) with a long-term antibacterial efficacy to prevent caries. CPC is an antibacterial agent approved by FDA, used as an OTC drug and contained in oral hygiene aids. CPC-Mont was incorporated in a dental adhesive to gradually release CPC. CPC_Mont technology rendered adhesives anti-bacterial properties with rechargeability, this without reducing its bonding potential, neither increasing its cytotoxicity.

A facile dopamine-assisted method for the preparation of antibacterial surfaces based on Ag/TiO2 nanoparticles

Highly effective antibacterial surfaces are crucial to prevent bacterial infections. In this work, we developed a simple method based on Ag/TiO2 nanoparticles via a dopamine-assisted process with long-term antibacterial efficacy, for the preparation of antibacterial glass surfaces. The chemical and morphological features of the prepared surfaces were investigated through field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, X-ray diffraction, and X-ray photoelectron spectrometry. The ultraviolet-visible spectroscopy absorption spectra of the prepared glass samples were measured with a spectrophotometer. The prepared Ag/TiO2 nanoparticle modified surfaces exhibited high activity in the elimination of the Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria under visible light and still maintained good antibacterial properties against E. coli after immersion in phosphate buffered saline solution for 60 days.

Silver nanoparticle antibacterial efficacy and resistance development in key bacterial species

Silver nanoparticles (AgNPs) are widely used for their antibacterial properties due to the expected benefit of long-term antibacterial efficacy and low potential for bacterial resistance. This study examined the potential for three bacterial species, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, to develop resistance to AgNPs in comparison to ciprofloxacin, benzalkonium chloride, and silver nitrate. Antibacterial efficacy was measured by determining the minimum inhibitory and minimum bactericidal concentrations using a broth microtiter method, and resistance development was tested using stepwise increasing concentrations of antibacterial agents. Only P. aeruginosa was able to develop resistance to AgNPs while all three organisms developed resistance to ciprofloxacin, and none of them developed resistance to silver nitrate or benzalkonium chloride. The resistance was stable and appeared to derive from multiple mechanisms since one AgNP-resistant variant was cross-resistant to silver nitrate, but the other variant was not. The precise mechanisms of AgNP resistance are yet to be elucidated, but they might involve the ability of phenazine pigments produced by P. aeruginosa to limit the bacterium’s exposure to silver. In order to reduce the possibility of bacteria developing resistance, AgNPs or their carrier medium should be engineered to ensure that an inhibitory concentration of silver is consistently maintained.

Long-term antibacterial efficacy of disinfectants based on benzalkonium chloride and sodium hypochlorite tested on surfaces against resistant gram-positive bacteria

The long-term antibacterial activity of disinfectant products based on benzalkonium chloride and sodium hypochlorite on surfaces was evaluated for prevention of bacterial adhesion. To this end, the European standard EN 13697, which determines the antibacterial activity of disinfectant formulations on bacteria, was adapted. As a prior step, the initial antibacterial activity (≥4 log10) was determined and after 24 h the long-term efficacy (≥3 log10) of each disinfectant product. Gram-positive bacteria belonging to the genera Staphylococci and Enterococci are able to survive in adverse conditions and have been involved in the increasing of bacterial resistance to different antimicrobials. In this study, Staphylococcus aureus and Enterococcus hirae were selected as ‘indicator organisms’ for the presence of bacterial contamination. The results showed that all the disinfectant products based on benzalkonium chloride and sodium hypochlorite had an initial antibacterial activity of up to 4 log10. After 24 h, the benzalkonium chloride based products demonstrated long-term antibacterial efficacy for both bacterial strains. Sodium hypochlorite as a sole compound at 4.0% did not demonstrate long-term efficacy, but when it was formulated with sodium hydroxide, benzalkonium chloride, fatty alcohol ethoxylate and amine oxide, it was effective. The bactericidal test developed in this study fulfills the purpose of evaluating the long-term antibacterial efficacy of disinfectant products on surfaces.

Anti-infection silver nanoparticle immobilized biomaterials facilitated by argon plasma grafting technology

Many research groups have attained slow, persistent, continuous release of silver ions through careful experimental design using existing methods. Such methods effectively kill planktonic bacteria and therefore prevent surface adhesion of pathogens. However, the resultant modified coatings cannot provide long-term antibacterial efficacy due to sustained anti-microbial release. In this study, the anti-infection activity of AgNP immobilized biomaterials was evaluated, facilitated by argon plasma grafting technology and activated by bacterial colonization. The modified materials generated in this study showed excellent specificity and were active against both Gram-positive and Gram-negative biofilm forming bacteria, including methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli. The anti-infection biomaterials developed in this study demonstrate several attractive advantages in comparison to traditional anti-bacterial surfaces loaded with antibiotics or other types of antibacterial agents and include (1) broad spectrum of activity against antibiotic resistant bacteria, (2) the unlikelihood of bacterial resistance, (3) specificity, (4) biocompatibility, and (5) stability.

Immobilization of antibacterial chlorhexidine on stainless steel using crosslinking polydopamine film: Towards infection resistant medical devices

Chlorhexidine (CHX) is known for its high antibacterial substantivity and is suitable for use to bio-inert medical devices due to its long-term antibacterial efficacy. However, CHX molecules require a crosslinking film to be stably immobilized on bio-inert metal surfaces. Therefore, polydopamine (PDA) was utilized in this study to immobilize CHX on the surface of 316L type stainless steel (SS316L). The SS316L disks were pre-treated, modified with PDA film and immobilized with different concentrations of CHX (10mM–50mM). The disks were then subjected to various surface characterization analyses (ATR-FTIR, XPS, ToF-SIMS, SEM and contact angle measurement) and tested for their cytocompatibility with human skin fibroblast (HSF) cells and antibacterial activity against Escherichia coli and Staphylococcus aureus. The results demonstrated the formation of a thin PDA film on the SS316L surface, which acted as a crosslinking medium between the metal and CHX. CHX was immobilized via a reduction process that covalently linked the CHX molecules with the functional group of PDA. The immobilization of CHX increased the hydrophobicity of the disk surfaces. Despite this property, a low concentration of CHX optimized the viability of HSF cells without disrupting the morphology of adherent cells. The immobilized disks also demonstrated high antibacterial efficacy against both bacteria, even at a low concentration of CHX. This study demonstrates a strong beneficial effect of the crosslinked PDA film in immobilizing CHX on bio-inert metal, and these materials are applicable in medical devices. Specifically, the coating will restrain bacterial proliferation without suffocating nearby tissues.

Nanomaterials and synergistic low-intensity direct current (LIDC) stimulation technology for orthopedic implantable medical devices.

Nanomaterials play a significant role in biomedical research and applications because of their unique biological, mechanical, and electrical properties. In recent years, they have been utilized to improve the functionality and reliability of a wide range of implantable medical devices ranging from well-established orthopedic residual hardware devices (e.g., hip implants) that can repair defects in skeletal systems to emerging tissue engineering scaffolds that can repair or replace organ functions. This review summarizes the applications and efficacies of these nanomaterials that include synthetic or naturally occurring metals, polymers, ceramics, and composites in orthopedic implants, the largest market segment of implantable medical devices. The importance of synergistic engineering techniques that can augment or enhance the performance of nanomaterial applications in orthopedic implants is also discussed, the focus being on a low-intensity direct electric current (LIDC) stimulation technology to promote the long-term antibacterial efficacy of oligodynamic metal-based surfaces by ionization, while potentially accelerating tissue growth and osseointegration. While many nanomaterials have clearly demonstrated their ability to provide more effective implantable medical surfaces, further decisive investigations are necessary before they can translate into medically safe and commercially viable clinical applications. The article concludes with a discussion about some of the critical impending issues with the application of nanomaterials-based technologies in implantable medical devices, and potential directions to address these.

In vitro antibacterial and cytotoxicity assay of multilayered polyelectrolyte‐functionalized stainless steel

Infection of implanted materials by bacteria constitutes one of the most serious complications following prosthetic and implant surgery. In the present study, a new strategy for confering stainless steel with antibacterial property via the alternate deposition of quaternized polyethylenimine (PEI) or quaternized polyethylenimine-silver complex and poly(acrylic acid) (PAA) was investigated. The success of the deposition of the polyelectrolyte multilayers (PEM) and its chemical nature was investigated by static water contact angle and X-ray photoelectron spectroscopy (XPS), respectively. The antibacterial activity was assessed using Escherichia coli (E. coli, a gram-negative bacterium) and Staphylococcus aureus (S. aureus, a gram-positive bacterium). The inhibition of E. coli and S aureus growth on the surface of functionalized films was clearly shown using the LIVE/DEAD Baclight bacterial viability kits and fluorescence microscopy. The cytotoxicity of the PEM to mammalian cells, evaluated by the MTT assay, was shown to be minimal and long-term antibacterial efficacy can be maintained. These results indicate new possibilities for the use of such easily built and functionalized architectures for the functionalization of surfaces of implanted medical devices.