Antibacterial properties of Ag nanoparticle loaded multilayers and formation of magnetically directed antibacterial microparticles

Facile preparation of multifunctional biomaterials BTO/Ag and their applications in photoelectrochemical sensing, photodegradation and antibacterial activities

With the progress of modern technology and the diversification of societal demands, traditional materials with single properties can no longer meet the requirements of complex and constantly evolving application scenarios. To tackle intricate biomedical applications like disease diagnosis and treatment, scientists are focusing on exploring the design of novel multifunctional biomaterials that possess diverse activities. Bismuth titanate (Bi4Ti3O12, BTO), which has multifunctionality and great application potential, unfortunately suffers from inadequate photocatalytic performance. On the other hand, silver nanoparticles (Ag), known for their antibacterial properties, have relatively limited functions. In this study, we overcame these limitations by combining BTO with Ag to form a BTO/Ag biomultifunctional material. Our experiments showed that the addition of Ag effectively improved BTO's UV absorption ability, decreased electron transfer resistance, and increased carrier concentration. As a result, the photocatalytic performance of BTO/Ag was significantly enhanced, and its photoelectrochemical sensing and photodegradation capabilities were also greatly improved. Moreover, BTO served as an effective substrate, preventing Ag from agglomerating and maximizing its antibacterial potential. In specific performance evaluations, ascorbic acid and methylene blue (MB) were used to study the photoelectrochemical sensing and photodegradation capabilities respectively, while Escherichia coli and Staphylococcus aureus were chosen as test organisms to assess the antibacterial properties. All in all, this research has yielded promising results.

Superhydrophobic Metal-Organic Framework-Based Composite Featuring Removal of Hydrophobic Drugs and Pesticides and Antibacterial Activities

The widespread use and contamination of natural sources by new-generation drugs and pesticides have enhanced concern about environmental pollution. Understanding the above importance, we developed a superhydrophobic metal-organic framework (MOF) (SHMOF': [Zr6O4(OH)4(BDC-NH-CO-R)2.4(BDC-NH2)0.6(CF3COO)6]·2.5H2O·4DMF) for ecological remediation via adsorption-based separation of hydrophobic drugs (flurbiprofen) and pesticides (fluazinam). The newly developed SHMOF' has a high adsorption capacity toward flurbiprofen and fluazinam, i.e., 435 and 575 mg/g, respectively. The adsorption equilibrium time of the MOF is very short (15 and 10 min for flurbiprofen and fluazinam, respectively). The outstanding superhydrophobic nature of the MOF was employed to separate flurbiprofen and fluazinam from highly alkaline and acidic media and environmental water samples. The SHMOF' has excellent selectivity toward the adsorption-based separation of flurbiprofen and fluazinam in the coexistence of common analytes. Again, we developed a polypropylene (PP) fabric-based composite of SHMOF' (SHMOF'@PP) to separate the hydrophobic targeted analytes by using a zero-energy-consuming filtration-based separation method, which made this separation process cost-efficient and user-friendly. Moreover, Ag nanoparticles were doped to the superhydrophobic composite. The Ag-doped reusable SHMOF'@PP@Ag composite exhibited excellent bacterial antiadhesion and antibacterial properties toward Staphylococcus aureus bacteria.

Fouling-Resistant Behavior of Hydrophobic Surfaces Based on Poly(dimethylsiloxane) Modified by Green rGO@ZnO Nanocomposites

In line with global goals to solve marine biofouling challenges, this study proposes an approach to developing a green synthesis inspired by natural resources for fouling-resistant behavior. A hybrid antifouling/foul release (HAF) coating based on poly(dimethylsiloxane) containing a green synthesized nanocomposite was developed as an environmentally friendly strategy. The nanocomposites based on graphene oxide (GO) and using marine sources, leaves, and stems of mangroves (Avicennia marina), brown algae (Polycladia myrica), and zinc oxide were compared. The effectiveness of this strategy was checked first in the laboratory and then in natural seawater. The performance stability of the coatings after immersion in natural seawater was also evaluated. With the lowest antifouling (17.95 ± 0.7%) and the highest defouling (51.2 ± 0.9%), the best fouling-resistant performance was for the coatings containing graphene oxide reduced with A. marina stem/zinc oxide (PrGZS) and graphene oxide reduced with A. marina leaves/zinc oxide with 50% multiwall carbon nanotubes (PrGZHC50), respectively. Therefore, the HAF coatings can be considered as developed and eco-friendly HAF coatings for the maritime industry.

Fast and Stable Antibacterial Coating of Photosensitive Aggregation-Induced Emission Luminogens for Disinfection on Medical Devices

Aggregation-induced emission luminogens (AIEgens) are promising photosensitizers that have exhibited excellent antibacterial ability with abundant reactive oxygen species (ROS) generation. TTCPy-PF6 and TTCPy-Br are deposited on the surface of diverse solid substrates through plasma-assistant electrostatic self-assembly. The AIEgens-covered coating can effectively eliminate different pathogenic Gram-positive (G+) bacteria and even their multidrug-resistant (MDR) mutants with negligible side effects such as cytotoxicity, hemolysis, and inflammation. Moreover, the AIEgen-coated surface can maintain high stability for long-time antibacterial usage, which is dependent on the ROS-mediated disruption of the attached bacteria. The AIEgen-based coatings with broad surface applicability have many advantages in high antibacterial ability, great biocompatibility, and low possibility of antibiotic pollution. The robust antibacterial ability and excellent biological safety of the AIEgen-based coatings would be helpful for the disinfection of medical devices.

3D printed PLGA scaffold with nano-hydroxyapatite carrying linezolid for treatment of infected bone defects

BACKGROUND

Linezolid has been reported to protect against chronic bone and joint infection. In this study, linezolid was loaded into the 3D printed poly (lactic-co-glycolic acid) (PLGA) scaffold with nano-hydroxyapatite (HA) to explore the effect of this composite scaffold on infected bone defect (IBD).

METHODS

PLGA scaffolds were produced using the 3D printing method. Drug release of linezolid was analyzed by elution and high-performance liquid chromatography assay. PLGA, PLGA-HA, and linezolid-loaded PLGA-HA scaffolds, were implanted into the defect site of a rabbit radius defect model. Micro-CT, H&E, and Masson staining, and immunohistochemistry were performed to analyze bone infection and bone healing. Evaluation of viable bacteria was performed. The cytocompatibility of 3D-printed composite scaffolds in vitro was detected using human bone marrow mesenchymal stem cells (BMSCs). Long-term safety of the scaffolds in rabbits was evaluated.

RESULTS

The linezolid-loaded PLGA-HA scaffolds exhibited a sustained release of linezolid and showed significant antibacterial effects. In the IBD rabbit models implanted with the scaffolds, the linezolid-loaded PLGA-HA scaffolds promoted bone healing and attenuated bone infection. The PLGA-HA scaffolds carrying linezolid upregulated the expression of osteogenic genes including collagen I, runt-related transcription factor 2, and osteocalcin. The linezolid-loaded PLGA-HA scaffolds promoted the proliferation and osteogenesis of BMSCs in vitro via the PI3K/AKT pathway. Moreover, the rabbits implanted with the linezolid-loaded scaffolds showed normal biochemical profiles and normal histology, which suggested the safety of the linezolid-loaded scaffolds.

CONCLUSION

Overall, the linezolid-loaded PLGA-HA scaffolds fabricated by 3D printing exerts significant bone repair and anti-infection effects.

Antibacterial, antioxidant, and anticancer potential of green fabricated silver nanoparticles made from Viburnum grandiflorum leaf extract

BACKGROUND

Recently, researchers are focusing on creating new tools to combat the antibiotic resistant bacteria and malignancy issues, which pose significant threats to humanity. Biosynthesized silver nanoparticles (AgNPs) are thought to be a potential solution to these issues. The biosynthesis method, known for its environmentally friendly and cost-effective characteristics, can produce small-sized AgNPs with antimicrobial and anticancer properties. In this study, AgNPs were bio-fabricated from the distilled water and methanolic extracts of Viburnum grandiflorum leaves. Physio-chemical characterization of the bio-fabricated AgNPs was conducted using UV-visible spectroscopy, scanning electron microscopy, energy dispersive X-ray, and X-ray diffraction analysis.

RESULTS

AgNPs produced from the methanol extract were smaller in size (12.28 nm) compared to those from the aqueous extract (17.77 nm). The bioengineered AgNPs exhibited a circular shape with a crystalline nature. These biosynthesized AgNPs demonstrated excellent bactericidal activity against both gram-negative (Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) bacteria. Highest antibacterial activity was observed with the methanol extract against P. aeruginosa (14.66 ± 0.74 mm). AgNPs from the methanol extract also displayed the highest antioxidant activity, with an IC50 value of 188.00 ± 2.67 μg/mL against 2,2-diphenyl-1-picrylhydrazyl (DPPH). Furthermore, AgNPs exhibited notable cytotoxic activity against Rhabdomyosarcoma cell line (RD cell) of human muscle cancer cell. The IC50 values calculated from the MTT assay were 26.28 ± 1.58 and 21.49 ± 1.44 μg/mL for AgNPs synthesized from aqueous and methanol extracts, respectively.

CONCLUSION

The methanol extract of V. grandiflorum leaves demonstrates significant potential for synthesizing AgNPs with effective antibacterial, antioxidant, and anticancer actions, making them applicable in various biomedical applications.

Prevention of marine biofouling in the aquaculture industry by a coating based on polydimethylsiloxane-chitosan and sodium polyacrylate

In this study, a series of novel hydrophobic/hydrophilic hybrid (HHH) coatings with the feature of preventing the fouling phenomenon was fabricated based on polydimethylsiloxane (PDMS), as matrix and two hydrophilic polymers: chitosan and sodium polyacrylate, as dispersed phases. Antibacterial activity, pseudo-barnacle adhesion strength, surface free energy, water contact angle, and water absorption were performed for all samples. Evaluating field immersion of the samples was performed in the natural seawater. The results showed that the dispersed phase containing PDMS coatings showed simultaneously both of antibacterial activity and foul release behavior. Among the samples, the PCs4 coating containing 4 wt% Cs indicated the lowest pseudo barnacle adhesion strength (0.04 MPa), the lowest surface free energy (18.94 mN/m), the highest water contact angle (116.05°), and the percentage of fouling organisms 9.8 % after 30 days immersion. The HHH coatings can be considered as novel eco-friendly antifouling/foul release coatings for aquaculture applications.

First clinical experience with posterior lumbar interbody fusion using a thermal-sprayed silver-containing hydroxyapatite-coated cage

BACKGROUND

To investigate the possibility of silver (Ag)-induced adverse events and the degree of bone fusion in posterior lumbar interbody fusion surgery using an Ag-containing hydroxyapatite (HA) lumbar interbody cage.

METHODS

An Ag-HA cage consisting of highly osteoconductive HA interfused with Ag was developed, and we applied it clinically at three university-affiliated hospitals from April 2020 to December 2020. During the 12-month postoperative observation period, Ag-related adverse events, neuropathy, and postoperative complications were investigated as indicators of safety, while clinical improvement and the fusion status were investigated as indicators of efficacy. Clinical improvement was defined as improvement beyond the minimum clinically important difference (MCID) in the numerical rating scale (NRS; 1.6) for low back and lower limb pain and the Oswestry Disability Index (ODI; 12.8).

RESULTS

We performed lumbar interbody fusion using an Ag-HA cage for 48 patients (female, n = 25; mean age, 67.5 years). The mean preoperative NRS was 6.4 (standard deviation, 1.9), while the mean preoperative ODI was 44 [12]. No adverse effects (i.e., argyria) were identified during the 12-month observation period. Surgical site infection occurred in one case, although the implant was preserved via immediate debridement. In total, 39 (81%) participants showed clinical improvement beyond MCID for both NRS and ODI. Bone fusion was achieved at 45 levels (88%) at 6 months and 48 levels (91%) at 12 months postoperatively.

CONCLUSIONS

The results of this study suggest that Ag-HA cages can be safely used in spinal fusion procedures and have the potential to prevent postoperative infections, prevent deterioration of the quality of life, and result in favorable outcomes. Larger-scale and longer-term follow-up studies will be required to corroborate these conclusions. Trial registration UMIN 000039964 (date: April 01, 2020).

A Review on Montmorillonite-Based Nanoantimicrobials: State of the Art

One of the crucial challenges of our time is to effectively use metal and metal oxide nanoparticles (NPs) as an alternative way to combat drug-resistant infections. Metal and metal oxide NPs such as Ag, Ag2O, Cu, Cu2O, CuO, and ZnO have found their way against antimicrobial resistance. However, they also suffer from several limitations ranging from toxicity issues to resistance mechanisms by complex structures of bacterial communities, so-called biofilms. In this regard, scientists are urgently looking for convenient approaches to develop heterostructure synergistic nanocomposites which could overcome toxicity issues, enhance antimicrobial activity, improve thermal and mechanical stability, and increase shelf life. These nanocomposites provide a controlled release of bioactive substances into the surrounding medium, are cost effective, reproducible, and scalable for real life applications such as food additives, nanoantimicrobial coating in food technology, food preservation, optical limiters, the bio medical field, and wastewater treatment application. Naturally abundant and non-toxic Montmorillonite (MMT) is a novel support to accommodate NPs, due to its negative surface charge and control release of NPs and ions. At the time of this review, around 250 articles have been published focusing on the incorporation of Ag-, Cu-, and ZnO-based NPs into MMT support and thus furthering their introduction into polymer matrix composites dominantly used for antimicrobial application. Therefore, it is highly relevant to report a comprehensive review of Ag-, Cu-, and ZnO-modified MMT. This review provides a comprehensive overview of MMT-based nanoantimicrobials, particularly dealing with preparation methods, materials characterization, and mechanisms of action, antimicrobial activity on different bacterial strains, real life applications, and environmental and toxicity issues.

Preparation of triangular silver nanoparticles and their biological effects in the treatment of ovarian cancer

BACKGROUND

In recent years, silver nanoparticles (AgNPs) have gradually been widely used, especially in the field of anticancer medicine. Ovarian cancer (OC) is the gynaecological malignancy with the highest mortality rate, and the current treatment is still based on surgery, chemotherapy and postoperative targeted therapy. Therefore, the development of safe and effective nanoparticles for targeted therapy of OC is very important. This study aimed to prepare a new type of triangular silver nanoparticles (tAgNPs) and evaluate the anticancer properties for OC in vitro and in vivo.

METHODS

The tAgNPs were chemically synthesized and characterized using scanning electron microscopy (SEM), ultraviolet (UV) spectrophotometry and other techniques. By performing cell-based tests, such as cell counting kit-8 (CCK-8), plate colony formation, cell apoptosis, reactive oxygen species (ROS), and western blot (WB) assays, the inhibitory effects and related mechanisms of tAgNPs on OC cells were analysed.The anticancer effect of tAgNPs in vivo was verified by a SKOV3 tumor-bearing mouse model.

RESULTS

Five types of tAgNPs with different colours were successfully synthesized, with a particle size of 25-50 nm and a good dispersion. The results of in vitro experiments showed that tAgNPs treatment reduced the viability and proliferation of SKOV3 cells, arrested the cell cycle in G0/G1 phase, inhibited the expression levels of proliferation-related factors and cyclins, and promoted cell apoptosis by producing ROS and increasing caspase-3 activity. Consistent with the results of in vitro experiments, in vivo animal experiments also showed that tAgNPs significantly inhibited the proliferation of ovarian cancer. More importantly, no obvious toxic and side effects were observed.

CONCLUSIONS

In this study, a novel triangular AgNPs was successfully prepared. tAgNPs are very stable, significantly inhibit the proliferation of OC cells and tumour growth in tumour-bearing mice, providing a promising nanotargeted therapy for OC.

In situ reduction of Ag on magnetic nanoparticles with gallic acid: effect of the synthesis parameters on morphology

Aim: Synthesis of Fe₃O₄-Ag composite nanoparticles (NPs) by a new in situ reduction of Ag NPs on the surface of Fe₃O₄ NPs using gallic acid as a reducing agent. Materials & methods: The influence of process parameters on NP morphology and functionalization was evaluated by means of field-emission scanning/scanning transmission electron microscopy and Fourier-transform IR spectroscopy. Results & conclusion: The synthesis conditions affected the morphology of the obtained NPs, evidence of the formation of polydispersed aggregates, nanoflower-like or nanodumbbell nanocomposites. In particular, well-defined nanodumbbells were obtained in aqueous media, with an NP/gallic acid ratio of 10:1, while the presence of a silica shell did not improve the morphology of Ag NPs nucleated on the Fe₃O₄ core.

Crocetin attenuating Urinary tract Infection and adherence of uropathogenic E. coli in NRK-52E cells via an inflammatory pathway

BACKGROUND AND OBJECTIVE

Urinary tract infections (UTI) are commonly treated with broad-spectrum antibiotics, but treatment has limitation due to causes of nephrotoxicity in uroepithelial cells. Recently, the researcher focuses their research on alternative therapy for the treatment of UTI. This study evaluated the anti-infectious effect of crocetin against adherence of pathogenic [2-¹⁴ C]-acetate labeled Escherichia coli (MTCC-729) to rat proximal renal tubular cells (NRK-52E cells) and explores the possible mechanism of action.

MATERIALS AND METHODS

In vitro cytotoxicity and radio acetate labeled tests were performed on NRK-52E cells. The rats were divided into five different groups as follows: normal control (NC), disease control (DC), and various doses of crocetin (1.25, 2.5, and 5 mg/kg) treated group rats. White blood cells in blood, urine, and bacterial colony counts were estimated at regular intervals. Pro-inflammatory cytokines, such as interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), interleukin-10 (IL-10), and interleukin-8 (IL-8), were also estimated. In the current study, we estimated the mRNA expression of toll-like receptor-4 (TLR-4) and toll-like receptor-2 (TLR-2) in the renal and bladder tissues.

RESULTS

Crocetin significantly (p < .05) inhibited the adherence of E. Coli in NRK-52E cells. Crocetin suppresses the lipid peroxidation (LPO) 42% in cells treated with H₂ O₂ cells without crocetin. The white blood cells (WBC) count in blood and urine were augmented and crocetin treatment significantly (p < .05) reduced the WBC in urine and blood. The pro-inflammatory cytokines, such as IL-6, MCP-1, IL-10, and IL-8, significantly (p < .05) increased in the DC group and crocetin significantly (p < .05) reduced the pro-inflammatory cytokines. Dose-dependent treatment of crocetin significantly reduced the mRNA expression of TLR2 and TLR4 in the renal and bladder tissues.

CONCLUSION

Crocetin considerably reduced the bacterial adherence to NRK-52E cells, attenuated the H₂ O₂ induced toxicity in NRK-52E cells and also improved the renal tubular function, and reduced the inflammatory response via altering the inflammatory and antioxidant markers.

PRACTICAL APPLICATION

As we all know that urinary tract infection is the most common disease worldwide. In this study, we scrutinized the protective effect of crocetin against urinary tract infection. Crocetin treatment considerably reduced the zone of inhibition and improved radioactivity. Crocetin significantly reduced the levels of cytokines and inflammatory mediators. Crocetin can be used as a protective drug in the treatment of urinary tract infections.

Biological fabrication and electrostatic attractions of new layered silver/talc nanocomposite using Lawsonia inermis L. and its chitosan-capped inorganic/organic hybrid: Investigation on acceleration of Staphylococcus aureus and Pseudomonas aeruginosa infected wound healing

In the present study, new-layered inorganic/organic hybrid of silver/talc nanocomposites (Ag/Tlc-NPs) and its chitosan-capped derivative (Ag/Tlc/Csn NCs) were biochemically synthesized utilizing Lawsonia inermis L. extract. The silver nanoparticles (Ag NPs) were synthesized employing green method on the exterior surface layer of talc mineral as a solid substrate. The negatively charged surface layer of talc might function as templates and can attract the chitosan cations from a solution to yield a layered hybrid structure, whose inorganic phase is formed by Si-O-Ag bonds. Our results revealed that Ag NPs were formed on the exterior surface of talc with a diameter with size of 124-215 nm. In addition, cytotoxicity, in vitro antibacterial activity, and clinical effects of wound-healing ointments containing talc were investigated. The results implied the successful synthesis of Ag/Tlc/Csn NCs using the extract. The structures were safe up to 0.50 mg/mL. In vitro studies confirmed antioxidant and antibacterial properties of Ag/Tlc/Csn NCs. In sum, our findings showed that the ointments improve wound healing process by inducing an anti-inflammatory M2 phenotype and bFGF, CD206, collagen1A, and IL-10 production that causes fibroblast migration and wound closure through influencing M2 macrophage. Ag/Tlc/Csn is suggested to be taken into consideration as a medical combination for improving infected wound healing and as a promising agent for clinical administration.

Development of biliary stent applying the antibacterial activity of silver: A literature review

BACKGROUND

Endoscopic transpapillary stenting is commonly performed in patients with obstructive jaundice caused by a biliary stricture. Although the plastic stent (PS) is widely used for biliary drainage because of the low-cost and easy procedure, patency is short after placement in the bile duct because of the small diameter. Dysfunction of PS is primarily caused by biliary sludge that forms as a result of bacterial adhesion and subsequent biofilm formation on the inner surface of the stent. It is well known that silver ions have excellent antibacterial activity against a wide range of microorganisms.

OBJECTIVE

This review provides an overview and perspective of the significance of silver-coated biliary stents.

METHODS

We collected literature regarding silver-coated biliary stents, reviewed the current research/development status and discussed their possible usefulness.

RESULTS

To date, several in vivo/vitro studies evaluated the patency of silver-blended or silver-coated biliary stents. These studies suggested that the silver coating on a PS was likely to prolong the patency period.

CONCLUSION

The development of biliary stents using silver is expected to prolong stent patency and prevent frequent stent replacement.

Incorporation of silver nanoparticles into active antimicrobial nanocomposites: Release behavior, analyzing techniques, applications and safety issues

Employing new strategies to develop novel composite systems has become a popular area of interest among researchers. Raising people's awareness and their attention to the health and safety issues are key parameters to achieve this purpose. One of the recommended strategies is the utilization of nanoparticles within the matrix of composite materials to improve their physical, mechanical, structural and antimicrobial characteristics. Silver nanoparticles (Ag NPs) have attracted much attention for nanocomposite applications mainly due to their antimicrobial characteristics. Herein, the current review will focus on the different methods for preparing antimicrobial nanocomposites loaded with Ag NPs, the release of Ag NPs from these nanostructures in different media, analyzing techniques for the evaluation of Ag release from nanocomposites, potential applications, and safety issues of nanocomposites containing Ag NPs. The applications of Ag NPs-loaded nanocomposites have been extensively established in food, biomedical, textile, environmental and pharmacological areas mainly due to their antibacterial attributes. Several precautions should be addressed before implementation of Ag NPs in nanocomposites due to the health and safety issues.

Facile Surfactant-, Reductant-, and Ag Salt-free Growth of Ag Nanoparticles with Controllable Size from 35 to 660 nm on Bulk Ag Materials

Morphologically and dimensionally controlled growth of Ag nanocrystals has long been plagued by surfactants or capping agents that complicate downstream applications, unstable Ag salts that impaired the reproducibility, and multistep seed injection that is troublesome and time-consuming. Here, we report a one-pot electro-chemical method to fast (∼2 min) produce Ag nanoparticles from commercial bulk Ag materials in a nitric acid solution, eliminating any need for surfactants or capping agents. Their size can be easily manipulated in an unprecedentedly wide range from 35 to 660 nm. Furthermore, the Ag nanoparticles are directly grown on the Ag substrate, highly desirable for promising applications such as catalysis and plasmonics. The mechanistic studies reveal that the concentration of Ag⁺ in the diffusion layer nearby the surface, controlled by the magnitude and duration of voltage, is critical in governing the nanoparticle formation (<1.3 mM) and its dimensional adjustability.

A systematic review of preclinical data regarding commercial silver-coated vascular grafts

OBJECTIVE

Vascular graft infection (VGI) is a serious complication with high mortality and morbidity rates. Several measures could be taken to decrease this risk, including the use of silver-containing vascular grafts. However, to date, no clinical advantages have been reported. This study reviews the outcome of preclinical studies focusing on the role of commercially available silver-coated grafts in the prevention of VGI.

METHODS

A systematic review was performed with a focus on the preclinical role of commercially available silver-coated vascular grafts in the prevention and treatment of VGI. A comprehensive search was conducted in Medline, Embase, and Web of Science.

RESULTS

Nine in vitro and five in vivo studies were included. Two commercial grafts were used (INTERGARD SILVER and Silver Graft). In vitro studies used both gram-positive and gram-negative strains. A positive antimicrobial effect was observed in seven of nine studies (77.8%). A delayed antifungal effect against Candida species was observed in vitro, but disappeared when adding serum proteins. In vivo studies witnessed a microbicidal effect in two out of five studies (40%), but only tested a single causative pathogen (ie, Staphylococcus aureus).

CONCLUSIONS

Both in vitro and in vivo studies demonstrated conflicting and mixed results concerning the antimicrobial efficacy of commercially available silver-containing grafts in the prevention of VGI. In general, the study setup was heterogeneous in the different articles. Given the lack of convincing preclinical evidence and their poor performance in clinical studies, more data are needed at this time to guide the appropriate use of silver grafts.

New Functionalized Macroparticles for Environmentally Sustainable Biofilm Control in Water Systems

Reverse osmosis (RO) depends on biocidal agents to control the operating costs associated to biofouling, although this implies the discharge of undesired chemicals into the aquatic environment. Therefore, a system providing pre-treated water free of biocides arises as an interesting solution to minimize the discharge of chemicals while enhancing RO filtration performance by inactivating bacteria that could form biofilms on the membrane system. This work proposes a pretreatment approach based on the immobilization of an industrially used antimicrobial agent (benzalkonium chloride—BAC) into millimetric aluminum oxide particles with prior surface activation with DA—dopamine. The antimicrobial efficacy of the functionalized particles was assessed against Escherichia coli planktonic cells through culturability and cell membrane integrity analysis. The results showed total inactivation of bacterial cells within five min for the highest particle concentration and 100% of cell membrane damage after 15 min for all concentrations. When reusing the same particles, a higher contact time was needed to reach the total inactivation, possibly due to partial blocking of immobilized biocide by dead bacteria adhering to the particles and to the residual leaching of biocide. The overall results support the use of Al₂O₃-DA-BAC particles as antimicrobial agents for sustainable biocidal applications in continuous water treatment systems.

Antimicrobial Activities of Synthesized Silver Nanoparticles using Ethanol and Water Extract of Mirabilis Jalapa

The focus of this study was to compare the antimicrobial activity of silver nanoparticles (AgNPs) synthesized using ethanol extracts (AgNPE) and water extracts (AgNPA) from four o’clock flowers (Mirabilis jalapa) against Staphylococcus aureus. AgNPs were characterized by UV-Vis diffraction, FTIR, SEM, and X-rays. UV-Vis analysis showed that AgNPA has an SPR band of about 460 nm and 530 nm for AgNPE, which proves the characteristics of the absorbance area of AgNPs. SEM images of AgNPE and AgNPA show a cuboid shape with a mean diameter of 80 and 30 nm, respectively and well dispersed. The response to the presence of polysaccharide biomolecules involved in forming AgNPs was analyzed using a Fourier transform infrared spectrometer. The result was that AgNPA and AgNPE have different reducing agents. The plant extracts, AgNPE and AgNPA, were studied for their antimicrobial activity against Staphylococcus aureus. The result was that both AgNPA and AgNPE showed good activity and showed that AgNPA with less inhibition was more effective than AgNPE.

Plasma-activated interfaces for biomedical engineering

As an important phenomenon to monitor disease development, cell signaling usually takes place at the interface between organisms/cells or between organisms/cells and abiotic materials. Therefore, finding a strategy to build the specific biomedical interfaces will help regulate information transmission and produce better therapeutic results to benefit patients. In the past decades, plasmas containing energetic and active species have been employed to construct various interfaces to meet biomedical demands such as bacteria inactivation, tissue regeneration, cancer therapy, and so on. Based on the potent functions of plasma modified surfaces, this mini-review is aimed to summarize the state-of-art plasma-activated interfaces and provide guidance to researchers to select the proper plasma and processing conditions to design and prepare interfaces with the optimal biological and related functions. After a brief introduction, plasma-activated interfaces are described and categorized according to different criteria including direct plasma-cells interfaces and indirect plasma-material-cells interfaces and recent research activities on the application of plasma-activated interfaces are described. The authors hope that this mini-review will spur interdisciplinary research efforts in this important area and expedite associated clinical applications.

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The Interfaces between organisms/cells and abiotic materials are crucial for cell signaling.

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Plasmas containing energetic and active species are potent tool to construct biomedical interfaces.

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The objective here is to summarize recent plasma-activated interfaces to spur interdisciplinary efforts for clinical applications.

Polymeric Coatings with Antimicrobial Activity: A Short Review

The actual situation of microorganisms resistant to antibiotics and pandemics caused by a virus makes research in the area of antimicrobial and antiviral materials and surfaces more urgent than ever. Several strategies can be pursued to attain such properties using different classes of materials. This review focuses on polymeric materials that are applied as coatings onto pre-existing components/parts mainly to inhibit microbial activity, but polymer surfaces with biocidal properties can be reported. Among the several approaches that can be done when addressing polymeric coatings, this review will be divided in two: antimicrobial activities due to the topographic cues, and one based on the chemistry of the surface. Some future perspectives on this topic will be given together with the conclusions of the literature survey.

Preparation of Ag nanoparticles by spark ablation in gas as catalysts for electrocatalytic hydrogen production

Spark ablation in gas (SAG) technology has the characteristics of being green, fast quenching, fast dynamics and specializes in producing metallic nanoparticles with a clean surface, small size, and abundant defects. In this study, Ag nanoparticles were prepared via SAG and in situ loaded on a carbon fiber through nitrogen flow. The effect of the carrier gas flow rate and deposition time on the particle size and the dispersibility of the as-prepared Ag nanoparticles on the carbon fiber by SAG were investigated, and the hydrogen evolution reaction (HER) performances of the samples in acidic media were further studied. When the carrier gas flow rate and deposition time are controlled at 5 L min-1 and 120 min, respectively, the sample displays an optimal activity with an overpotential of 362 mV at 10 mA cm-2, which is superior to commercial Ag nanoparticles on carbon fibers. Accordingly, this synthetic technology provides a new way to obtain efficient metallic nano-catalysts and is expected to achieve large-scale application.

In vitro biocompatibility evaluation of radiolytically synthesized silver/polyvinyl hydrogel nanocomposites for wound dressing applications

Nano silver/polyvinyl alcohol hydrogel nanocomposites have been prepared using gamma irradiation technique. Gamma irradiation serves as a crosslinking agent for the polyvinyl alcohol hydrogels and also acts as a reducing agent for reduction of Ag+ ions to zero valent Ag0 within the polyvinyl alcohol crosslinked network. The microstructural characteristics of the prepared composites were studied using powder X-ray diffraction, ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy and field emission scanning electron microscopy analysis. The data obtained by these characterizations indicate the homogeneous distribution of silver nanoparticles on the polyvinyl alcohol network. The swelling properties and mechanical parameters of the silver/polyvinyl alcohol hydrogel nanocomposites tend to show improvements, making them a better material for wound care applications. The silver/polyvinyl alcohol hydrogel nanocomposites have shown good antibacterial potential against both Gram-positive and Gram-negative bacteria and shown nil or minimal cytotoxic effect on human melanoma (SK-MEL-2) and mouse melanoma (B16-F1) cell lines. Overall, it was concluded that under optimized condition, silver/polyvinyl alcohol hydrogel nanocomposites synthesized using gamma irradiation technique are excellent candidates for wound dressing application.

Biological Safe Gold Nanoparticle-Modified Dental Aligner Prevents the Porphyromonas gingivalis Biofilm Formation

Oral microbiology could directly influence overall health. Porphyromonas gingivalis (P. gingivalis) is a highly pathogenic bacterium that causes periodontitis and other related systematic diseases, including Alzheimer's disease. Orthodontic devices (e.g., invisalign aligner) is commonly used in populations with periodontitis who are also at a high risk of systematic diseases. In this study, newly explored antibacterial 4,6-diamino-2-pyrimidinethiol-modified gold nanoparticles (AuDAPT) were coated onto aligners. The coated aligners showed favorable antibacterial activity against P. gingivalis. In the presence of the coated aligner, the number of planktonic cells was decreased, and biofilm formation was prevented. This material also showed favorable biocompatibility in vivo and in vitro. This study reveals a new method for treating oral P. gingivalis by coating aligners with AuDAPT, which has typical advantages compared to other treatments for both periodontitis and related systematic diseases.

Mussel-Inspired Dual-Cross-linking Hyaluronic Acid/ε-Polylysine Hydrogel with Self-Healing and Antibacterial Properties for Wound Healing

Physicians have long been calling for an inherent antimicrobial wound dressing, which will be a great progress for treating complicated infections. Here, we report a novel bioadhesive hydrogel with inherent antibacterial properties prepared by mixing modified hyaluronic acid (HA) and ε-polylysine (EPL). This hydrogel can effectively kill Gram (+) and (-) bacteria for its high positive charge density on the surface. The sol-gel transition occurs within seconds via horseradish peroxidase enzymatic cross-linking and Schiff base reaction, which also allows the hydrogel to recover completely from destruction quickly within 5 min. In an infected rat wound model, histological studies indicated that the hydrogels effectively killed bacteria on the surface of wounds and accelerated wound healing. Histological analysis indicated that the thickness of the newborn skin, the density of the newborn microvascular, granulation tissue, and the collagen of rats treated with hydrogel dressings were twice as high as those treated by commercial fibrin glue. These results indicate that the HA/EPL hydrogel has great potential as an antibacterial wound dressing for future clinical applications.

Universal Antifogging and Antimicrobial Thin Coating Based on Dopamine-Containing Glycopolymers

A novel strategy for preparing universal antifogging and antimicrobial coating is reported by the means of one-step coating and Ag nanoparticle (AgNP) formation in situ. A series of hydrophilic glycopolymers including poly(N-3,4-dihydroxybenzenethyl methacrylamide-co-2-deoxy-2-(methacrylamido)glucopyranose) (P1s) and poly(N-3,4-dihydroxybenzenethyl methacrylamide-co-methacrylic acid-co-2-deoxy-2-(methacrylamido)glucopyranose) (P2s) were synthesized by sunlight-induced reverse addition-fragmentation chain transfer (RAFT) polymerization. With the ability to strongly immobilize onto organic and inorganic surfaces (i.e., glass slide, silicon wafer, and polycarbonate) via catechol groups, P1s are very convenient to form superhydrophilic and transparent thin coatings, which result in a unique antifogging property. Additionally, the antimicrobial property is realized by in situ AgNPs forming P2 coatings, facilitated by the presence of carboxyl groups and catechol groups in the polymer chain, rendering it superior antimicrobial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus microorganisms. This antifogging and antimicrobial thin coating shows strong prospects in medical and optical devices, with the extra benefits of avoiding potential pathogen infection in vitro or while in storage.

Small molecule-decorated gold nanoparticles for preparing antibiofilm fabrics

The increase in antibiotic resistance reported worldwide poses an immediate threat to human health and highlights the need to find novel approaches to inhibit bacterial growth. In this study, we present a series of gold nanoparticles (Au NPs) capped by different N-heterocyclic molecules (N_Au NPs) which can serve as broad-spectrum antibacterial agents. Neither the Au NPs nor N-heterocyclic molecules were toxic to mammalian cells. These N_Au NPs can attach to the surface of bacteria and destroy the bacterial cell wall to induce cell death. Sonochemistry was used to coat Au NPs on the surface of fabrics, which showed superb antimicrobial activity against multi-drug resistant (MDR) bacteria as well as excellent efficacy in inhibiting bacterial biofilms produced by MDR bacteria. Our study provides a novel strategy for preventing the formation of MDR bacterial biofilms in a straightforward, low-cost, and efficient way, which holds promise for broad clinical applications.

Green synthesis of silver nanoparticles and their applications as an alternative antibacterial and antioxidant agents

Antimicrobial resistance is a complex global health challenge today. Discovery and development of new natural alternates with novel targets is utmost priority. In this experiment, alternative antibiotic agents in the form of silver nanoparticles (SNPs) and Achillea millefolium L. extracts were evaluated for antibacterial and antioxidant activity. The SNPs were synthesized using aqueous, ethanol and methanol extracts of A. millefolium and were monitored by a color change and UV-vis spectroscopy. The size and shape of the nanoparticles were determined through scanning electron microscopy and phase was assessed through X-ray diffraction. The SNPs were shown to have an average diameter of 20.77, 18.53 and 14.27 nm with spherical, rectangular and cubical shapes, synthesized from aqueous, ethanol and methanol extract respectively. The response of biomolecules present in plant extract during the formation of SNPs was analyzed by Fourier transform infrared spectrometry, showing polyphenols, proteins, carboxylic acid and alcohol are involved in the formation of SNPs. The plant extracts and SNPs were then studied for their antibacterial potential against common human pathogens such as gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacteria (Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa), displaying a very good activity against both types of bacteria. The Methanol-SNPs exhibit greater inhibition of DPPH radicals with IC₅₀ 7.03 ± 0.31 μg/mL. This green method of synthesis of SNPs would support the production of SNPs with considerably boosted antibacterial and antioxidant properties and significantly enhanced therapeutic performance.

Structural, luminescent and antimicrobial properties of ZnS and CdSe/ZnS quantum dot structures originated by precursors

ZnS quantum dots (QDs) and their core/shell (CdSe/ZnS) structures were studied for Zn based precursor reactivities. ZnS and CdSe/ZnS QDs were prepared selecting aqueous route and then characterized via XRD, TEM, EDX, PL, RAMAN and FTIR practices. Core/shell nanostructures were synthesized by taking dissimilar precursors for the shell formation. Photoluminescence spectra of prepared QDs corroborate the effectual luminescence. Prepared QDs have large surface area that make them useful alternative as organic antimicrobial agent which are highly irritant and unstable. Study of antimicrobial behavior of QD structures was carried out by disk diffusion method. Antimicrobial study of QDs and their core/shell structures was performed against gram negative and gram positive bacteria, E. coli, A. baumanni and Bacillus subtilis respectively. It is found that elemental composition and size of QDs plays important role in antimicrobial behavior. Prepared QDs are fluorescent and have a key role in complex microbial population studies and identification of bacteria.

A Bi2S3@mSiO2@Ag nanocomposite for enhanced CT visualization and antibacterial response in the gastrointestinal tract

The non-invasive imaging of the gastrointestinal (GI) tract is highly desired for clinical research due to the various GI tract bacterial infection-induced diseases. To treat GI tract infections, various antibiotics have been used in the clinic. The growing problem of multidrug-resistant bacteria calls for effective antibiotic alternatives. Here, we construct a dual-functional Bi₂S₃@mSiO₂@Ag nanocomposite for simultaneous enhanced X-ray computed tomography (CT) imaging and efficient antibacterial activity in the GI tract. The nanocomposite also has good stability, low cytotoxicity, and negligible hemolysis. Moreover, the investigation of the long-term toxicity and biodistribution of the Bi₂S₃@mSiO₂@Ag nanocomposite after oral administration confirms its safety at the tested dosage. In particular, Ag nanoparticles (NPs) well dispersed on a silica substrate can reduce the antibacterial dosage and enhance the antibacterial activity of the Bi₂S₃@mSiO₂@Ag nanocomposite. Furthermore, we have established bacterially infected enteritis animal models to confirm the antibacterial ability of the nanocomposite. This work opens up a new avenue for the design of a nanotheranostic agent that acts as both a contrast agent for the enhanced visualization of the GI tract and an antibacterial agent as an alternative to antibiotics.

Gold Nanoclusters-Coated Orthodontic Devices Can Inhibit the Formation of Streptococcus mutans Biofilm

Oral health is an issue that has attracted increasing attention recently. Poor oral hygiene may induce the formation of oral biofilm on orthodontic devices, and cause gingivitis and dental caries. Here, we present a strategy for modifying orthodontic devices (e.g., invisalign aligner) with quaternary ammonium (QA)-modified gold nanoclusters (QA-GNCs) as an antibiotic reagent to prevent bacterial contamination and biofilm formation. The QA-GNCs-coated aligner can efficiently inhibit the adhesion of cariogenic pathogenic Streptococcus mutans and the formation of biofilm. Moreover, the antibacterial activity of the coated QA-GNCs can be maintained for at least 3 months and after repeated usage (>3 cycles). Furthermore, the QA-GNCs coating shows excellent biosafety confirmed by the cell viability test, the hemolysis assay, and animal experiments. Our strategy for antibacterial coating has the advantages of broad applications, low cost, good stability, high antibacterial efficiency, good biocompatibility, and low risk of antibiotic contamination, which could be particularly useful in preventing infections involving implantable medical devices or wearable electronics.

Engineered nanomaterials: From their properties and applications, to their toxicity towards marine bivalves in a changing environment

As a consequence of their unique characteristics, the use of Engineered Nanomaterials (ENMs) is rapidly increasing in industrial, agricultural products, as well as in environmental technology. However, this fast expansion and use make likely their release into the environment with particular concerns for the aquatic ecosystems, which tend to be the ultimate sink for this type of contaminants. Considering the settling behaviour of particulates, benthic organisms are more likely to be exposed to these compounds. In this way, the present review aims to summarise the most recent data available from the literature on ENMs behaviour and fate in aquatic ecosystems, focusing on their ecotoxicological impacts towards marine and estuarine bivalves. The selection of ENMs presented here was based on the OECD's Working Party on Manufactured Nanomaterials (WPMN), which involves the safety testing and risk assessment of ENMs. Physical-chemical characteristics and properties, applications, environmental relevant concentrations and behaviour in aquatic environment, as well as their toxic impacts towards marine bivalves are discussed. Moreover, it is also identified the impacts derived from the simultaneous exposure of marine organisms to ENMs and climate changes as an ecologically relevant scenario.

In Situ Immobilized Silver Nanoparticles on Rubia tinctorum Extract-Coated Ultrasmall Iron Oxide Nanoparticles: An Efficient Nanocatalyst with Magnetic Recyclability for Synthesis of Propargylamines by A3 Coupling Reaction

This research suggests a green method for synthesizing hybrid magnetic nanocomposites that can be used as a reductant and a stabilizing agent for immobilizing metal nanoparticles (NPs). The central idea is the modification of magnetic NPs using Rubia tinctorum extract, which consists of numerous carbonyl and phenolic hydroxyl functional groups to increase adsorption of metals and chelate silver ions, and decrease the adsorption of silver ions by Ag NPs, in situ. Thus, the suggested catalyst preparation process does not require toxic reagents, additional reductants, and intricate instruments. To show the effectiveness of the plant extract in reducing and immobilizing Ag NPs, the structural, morphological, and physicochemical features of the particles are studied using Fourier-transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. One of the advantages of the suggested method is to reduce the size of the magnetic NPs from 15-20 to 2-5 nm, in the presence of the extract. Additionally, the prepared Fe3O4@R. tinctorum/Ag nanocatalyst is demonstrated to exhibit a very high activity in the catalysis of the three-component reaction of aldehydes, amines, and alkynes (A3 coupling) with good to high yields of diverse propargylamines. Moreover, the nanocatalyst can be recovered several times with no considerable leaching or loss of performance.

Controlling the Antimicrobial Action of Surface Modified Magnesium Hydroxide Nanoparticles

Magnesium hydroxide nanoparticles (Mg(OH)2NPs) have recently attracted significant attention due to their wide applications as environmentally friendly antimicrobial nanomaterials, with potentially low toxicity and low fabrication cost. Here, we describe the synthesis and characterisation of a range of surface modified Mg(OH)2NPs, including particle size distribution, crystallite size, zeta potential, isoelectric point, X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). We explored the antimicrobial activity of the modified Mg(OH)2NPs on the microalgae (C. reinhardtii), yeast (S. cerevisiae) and Escherichia coli (E. coli). The viability of these cells was evaluated for various concentrations and exposure times with Mg(OH)2NPs. It was discovered that the antimicrobial activity of the uncoated Mg(OH)2NPs on the viability of C. reinhardtii occurred at considerably lower particle concentrations than for S. cerevisiae and E. coli. Our results indicate that the antimicrobial activity of polyelectrolyte-coated Mg(OH)2NPs alternates with their surface charge. The anionic nanoparticles (Mg(OH)2NPs/PSS) have much lower antibacterial activity than the cationic ones (Mg(OH)2NPs/PSS/PAH and uncoated Mg(OH)2NPs). These findings could be explained by the lower adhesion of the Mg(OH)2NPs/PSS to the cell wall, because of electrostatic repulsion and the enhanced particle-cell adhesion due to electrostatic attraction in the case of cationic Mg(OH)2NPs. The results can be potentially applied to control the cytotoxicity and the antimicrobial activity of other inorganic nanoparticles.

Nanocomposite multifunctional polyelectrolyte thin films with copper nanoparticles as the antimicrobial coatings

The work presents the formation and physicochemical characterization of polyelectrolyte-copper nanocomposite coatings using: poly(diallyldimethylammonium chloride) (PDADMAC) as a polycation, poly(sodium 4-styrenesulfonate)(PSS) as a polyanion and negatively charged copper nanoparticles (CuNPs) to obtain biocompatible surfaces with an antibacterial functionality. The mass and thickness of composite films were investigated by the quartz crystal microbalance with dissipation monitoring (QCM-D) and the ellipsometry whereas, the structure and morphology of coatings were examined using scanning electron microscopy (SEM). The increase of the UV-Vis absorption confirmed the formation of the consecutive layers of the film. Antibacterial activity of the coatings was tested on a representative Gram-positive bacteria strain, Staphylococcus aureus. The microbiological tests were performed and bacteria visualized using fluorescent staining and microscopic technique. It was demonstrated that nanostructured films had antibacterial properties, which makes polyelectrolyte multilayer films containing copper an interesting material in biomedical applications area, e.g., for the prevention of microbial deposition on surfaces.