Sustained Release Of Silver Research Articles

Antifouling coating with controllable and sustained silver release for long-term inhibition of infection and encrustation in urinary catheters.

Urinary tract infections constitute a large proportion of nosocomial infections, and the urinary catheter is the most important predisposing factor. Encrustation induced by urease-producing uropathogens like Proteus mirabilis causes further complications. In the present work, a strategy for controllable and sustained release of silver over several weeks has been developed for combating bacterial infection and encrustation in urinary devices. Silver nanoparticles (AgNPs) were first immobilized on polydopamine (PDA) pre-treated silicone catheter surface and this was followed by another PDA coating. The number of AgNP-PDA bilayers could be manipulated to control the amount of silver loaded and its subsequent release. Poly(sulfobetaine methacrylate-co-acrylamide) was then grafted to provide an antifouling outer layer, and to ensure free diffusion of Ag from the surface. The micron-scale combination of an antifouling coating with AgNP-PDA bilayers reduced colonization of the urinary catheter by uropathogens by approximately two orders of magnitude. With one and two AgNP-PDA bilayers, the coated catheter could resist encrustation for 12 and 45 days, respectively, compared with approximately 6 days with the Dover™ silver-coated catheter. Such anti-infective and anti-encrustation catheters can potentially have a large impact on reducing patient morbidity and healthcare expenditure.

Electrospun Blends of Gelatin and Gelatin–Dendrimer Conjugates As a Wound-Dressing and Drug-Delivery Platform

In this work, we report a new nanofiber construct based on electrospun blends of gelatin and gelatin-dendrimer conjugates. Highly branched star-shaped polyamidoamine (PAMAM) dendrimer G3.5 was covalently conjugated to gelatin via EDC/NHS chemistry. Blends of gelatin and gelatin-dendrimer conjugates mixed with various loading levels of silver acetate (0, 0.83, 1.65, and 3.30% w/w) were successfully electrospun into nanofiber constructs (NCs). The NCs were further converted into semi-interpenetrating networks (sIPNs) with photoreactive polyethylene glycol diacrylate (Mn = 575 g mol(-1)) (PEG DA575). They were characterized in terms of fiber morphology, diameter, pore size, permeability, degradation, and mechanical properties. The resulting sIPN NCs retained nanofiber morphology, possessed similar fiber diameters to counterpart NCs, and gained improved structural stability. The sIPN NCs also showed good swelling capacity owing to porous structures and were permeable to aqueous solutions. Silver-containing sIPN NCs allowed sustained silver release and showed antimicrobial activity against two common types of pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. Incorporation of dendrimers into the gelatin nanofibers through covalent conjugation not only expands drug loading capacity of nanofiber constructs but also provides tremendous flexibility for developing multifunctional electrospun dressing materials.

Comparative Study of Loading of Anodic Porous Alumina with Silver Nanoparticles Using Different Methods.

Three different routes were used to infiltrate the pores of anodic porous alumina templates with silver nanoparticles, selected as an example of a bioactive agent. The three methods present a continuous grading from more physical to more chemical character, starting from ex situ filling of the pores with pre-existing particles, moving on to in situ formation of particles in the pores by bare calcination and ending with in situ calcination following specific chemical reactions. The resulting presence of silver inside the pores was assessed by means of energy dispersive X-ray spectroscopy and X-ray diffraction. The number and the size of nanoparticles were evaluated by scanning electron microscopy of functionalized alumina cross-sections, followed by image analysis. It appears that the best functionalization results are obtained with the in situ chemical procedure, based on the prior formation of silver ion complex by means of ammonia, followed by reduction with an excess amount of acetaldehyde. Elution of the silver content from the chemically functionalized alumina into phosphate buffer saline has also been examined, demonstrating a sustained release of silver over time, up to 15 h.

Preparation and characterization of antimicrobial wound dressings based on silver, gellan, PVA and borax

Silver-loaded dressings are designed to provide the same antimicrobial activity of topical silver, with the advantages of a sustained silver release and a reduced number of dressing changes. Moreover, such type of dressing must provide a moist environment, avoiding fiber shedding, dehydration and adherence to the wound site. Here we describe the preparation of a novel silver-loaded dressing based on a Gellan/Hyaff® (Ge-H) non woven, treated with a polyvinyl alcohol (PVA)/borax system capable to enhance the entrapment of silver in the dressing and to modulate its release. The new hydrophilic non woven dressings show enhanced water uptake capability and slow dehydration rates. A sustained silver release is also achieved. The antibacterial activity was confirmed on Staphylococcus aureus and Pseudomonas aeruginosa.

Hydrothermal synthesis of bacterial cellulose/AgNPs composite: A “green” route for antibacterial application

► A green route was proposed to synthesize AgNPs by hydrothermal synthesis. ► AgNPs of small size (17 nm) were synthesized on BC matrix. ► BC served as both the reducing and stabilizing agent in a gently heated system. ► Long-term antibacterial performance was obtained by BC/AgNPs composites. Antibacterial materials based on cellulose have been widely used in many fields. In this work, an environmentally benign and facile approach for production of silver nanoparticles (AgNPs) was proposed for the first time by hydrothermal synthesis using bacterial cellulose (BC) as both the reducing and stabilizing agent, without any chemical reagents introduced. Some key reaction parameters were optimized to achieve a high antibacterial activity of the BC/AgNPs composite. Under the optimal conditions, a small size and a narrow distribution of AgNPs, 17.1 ± 5.9 nm, was formed on the BC matrix, with a silver content of 1.78% (w/w) and a MIC value of 1.30 × 10 −4 μg/CFU. Moreover, a sustained release of silver and a prolonged antibacterial performance of the composite against Staphylococcus aureus were found over a long period time of 72 h, which were important for practical applications.

Antibacterial Performance of Polydopamine-Modified Polymer Surfaces Containing Passive and Active Components

A growing number of device-related nosocomial infections, elevated hospitalization costs, and patient morbidity necessitate the development of novel antibacterial strategies for clinical devices. We have previously demonstrated a simple, aqueous polydopamine dip-coating method to functionalize surfaces for a wide variety of uses. Here, we extend this strategy with the goal of imparting antifouling and antimicrobial properties to substrates, exploiting the ability of polydopamine to immobilize polymers and induce metal nanoparticle formation. Polydopamine was deposited as a thin adherent film of 4 nm thickness from alkaline aqueous solution onto polycarbonate substrates, followed by grafting of antifouling polymer polyethylene glycol and in situ deposition of silver nanoparticles onto the polydopamine coated polycarbonate substrates. Elemental and morphological surface analyses confirmed successful grafting of polyethylene glycol brushes onto polydopamine-coated substrates, as well as spontaneous silver nanoparticle formation for polydopamine-coated substrates incubated in silver-nitrate solutions. Sustained silver release was observed over at least 7 days from silver-coated substrates, and the release kinetics could be modulated via additional polydopamine overlayers. In vitro functional assays employing gram negative and positive strains demonstrated dual fouling resistance and antibacterial properties of the coatings due to the fouling resistance of grafted polyethylene glycol and antibacterial effect of silver, respectively. Polycarbonate substrates coated only with silver using a method similar to existing commercial coatings provided an antibacterial effect but failed to inhibit bacterial attachment. Taking into account the previously demonstrated substrate versatility of polydopamine coatings, our findings suggest that this strategy could be implemented on a variety of substrate materials to simultaneously improve antifouling and antimicrobial performance.

Engineering and optimisation of medically multi-functional mesoporous SiO2 fibers as effective wound dressing material

In this paper, we propose a novel strategy for the preparation of flexible mesoporous SiO2 fibers containing silver nanoparticles (Ag-cSiO2@mSiO2) as an effective wound dressing. The Ag-cSiO2@mSiO2 was core–shell structured, composed of a condensed electrospun SiO2 nanofiber doped with Ag NPs (silver nanoparticles) and a mesoporous SiO2 shell. Due to a high specific surface area and large pore volume, the Ag-cSiO2@mSiO2 can substantially absorb exudates, the absorption capacity for water and SBF (simulated body fluid) reached 267 wt% and 254 wt% of the sample, respectively. Additionally, the mesopores can also act as hosts for the accommodation of drugs. The Loading capacity of IBU (ibuprofen) reached up to 18 wt% of the sample, and its release was relatively fast, more than 85% of the drug was released within 12 h. The condensed core of the SiO2 nanofiber not only endowed the sample with a high flexibility, but also slowly released silver to possess a sustained antibiotic effect. Considering its effective exudate-absorption ability, dual drug-release profiles (fast release of IBU and sustained release of silver), together with its chemical and physical stability, biocompatibility and high flexibility, Ag-cSiO2@mSiO2 could be a promising wound dressing material.

Preparation and antibacterial properties of plasma sprayed nano-titania/silver coatings

In this work, plasma sprayed nano-titania/silver coatings were deposited on titanium substrates to obtain an implant material having excellent antibacterial property. The surface characteristics of nano-titania/silver coatings were investigated by scanning electron microscopy, energy dispersive spectrometer, optical emission spectrometry and X-ray diffraction. The bioactivity of nano-titania/silver coatings was examined by simulated body fluid soaking test. The antibacterial activity against Escherichia coli was examined by bacterial counting method. The cytocompatibility and in vitro osteotoxicity was evaluated by alamarBlue™ Assay using MG-63 osteoblasts. The results showed that nano-titania/silver coatings still had good bioactivity. Silver existed homogeneously in the nano-titania coating as silver oxide and metal silver, which ensured a sustained release of silver for 28 days. The loaded silver had no obvious osteotoxicity, while showed strong inhibition against the growth of Escherichia coli.

Biological and antibacterial properties of plasma sprayed wollastonite/silver coatings.

In this work, plasma sprayed wollastonite/silver coatings were prepared to obtain an implant material having excellent bioactivity, cytocompatibility as well as antibacterial property. The surface characteristics of wollastonite/silver coating were investigated by scanning electron microscopy, energy dispersive spectrometer, atomic absorbance spectroscope and x-ray diffraction. The bioactivity was examined by simulated body fluid soaking test. The antibacterial activity against Escherichia coli was examined by bacterial counting method. And the cytocompatibility and in vitro osteotoxicity was evaluated by alamarBlue Assay using MG-63 osteoblasts. The results showed that silver existed in the wollastonite coating homogeneously as silver oxide and metal silver, which ensured a sustained release of silver for 28 days in deionized water. The loaded silver showed strong inhibition against the growth of Escherichia coli, however exhibited no osteotoxicity. Although the wollastonite/silver coating can not induce apatite formation as quickly as the wollastonite coating did in simulated body fluid, it still exhibited good bioactivity. Therefore, the plasma sprayed wollastonite/silver coating is a promising implant material to be applied in surgery, reducing postoperative infections.

Preparation and antibacterial effect of plasma sprayed wollastonite coatings loading silver

In this work, the plasma sprayed wollastonite coating was soaked in 5 wt% AgNO 3 solution at room temperature to load silver for improving its antibacterial effect. The surface characteristics of the silver-loaded coating were investigated by SEM, EDS and XRD. The release rate of silver from the coating was measured by ICP-OES in deionized water. The osteotoxicity of the silver-loaded coating was evaluated by in vitro cell culturing test. The antibacterial activity against Staphylococcus aureus was examined by Zone of Inhibition test. The results showed that the loaded silver reacted with the wollastonite coating to form silver silicate, which ensured a sustained release of silver in deionized water for as long as 50 days. The antibacterial activity and cell culturing tests confirmed that the silver released from silver-loaded wollastonite coating had strong inhibition against the growth of S. aureus, while they did not exhibit any adverse effects on the osteoblasts proliferation.

Antimicrobial surface functionalization of plastic catheters by silver nanoparticles

To test the antimicrobial activity and evaluate the risk of systemic toxicity of novel catheters coated with silver nanoparticles. Catheters were coated with silver using AgNO3, a surfactant and N,N,N ',N '-tetramethylethylenediamine as a reducing agent. Particle size was determined by electron microscopy. Silver release from the catheters was determined in vitro and in vivo using radioactive silver ((110m)Ag+). Activity on microbial growth and biofilm formation was evaluated against pathogens most commonly involved in catheter-related infections, and the risk for systemic toxicity was estimated by measuring silver biodistribution in mice implanted subcutaneously with (110 m)Ag+-coated catheters. The coating method yielded a thin ( approximately 100 nm) layer of nanoparticles of silver on the surface of the catheters. Variations in AgNO3 concentration translated into proportional changes in silver coating (from 0.1 to 30 microg/cm(2)). Sustained release of silver was demonstrated over a period of 10 days. Coated catheters showed significant in vitro antimicrobial activity and prevented biofilm formation using Escherichia coli, Enterococcus, Staphylococcus aureus, coagulase-negative staphylococci, Pseudomonas aeruginosa and Candida albicans. Approximately 15% of the coated silver eluted from the catheters in 10 days in vivo, with predominant excretion in faeces (8%), accumulation at the implantation site (3%) and no organ accumulation (< or = 0.1%). A method to coat plastic catheters with bioactive silver nanoparticles was developed. These catheters are non-toxic and are capable of targeted and sustained release of silver at the implantation site. Because of their demonstrated antimicrobial properties, they may be useful in reducing the risk of infectious complications in patients with indwelling catheters.

Silver dressings: their role in wound management

Dressings have a part to play in the management of wounds; whether they are sutured or open, usually chronic wounds of many aetiologies which are healing by secondary intention. They traditionally provide a moist wound environment, but this property has been extended through simple to complex, active dressings which can handle excessive exudate, aid in debridement, and promote disorganised, stalled healing. The control of infection remains a major challenge. Inappropriate antibiotic use risks allergy, toxicity and most importantly resistance, which is much reduced by the use of topical antiseptics (such as povidone iodine and chlorhexidine). The definition of what is an antimicrobial and the recognition of infection has proven difficult. Although silver has been recognised for centuries to inhibit infection its use in wound care is relatively recent. Evidence of the efficacy of the growing number of silver dressings in clinical trials, judged by the criteria of the Cochrane Collaboration, is lacking, but there are good indications for the use of silver dressings, to remove or reduce an increasing bioburden in burns and open wounds healing by secondary intention, or to act as a barrier against cross contamination of resistant organisms such as MRSA. More laboratory, and clinical data in particular, are needed to prove the value of the many silver dressings which are now available. Some confusion persists over the measurement of toxicity and antibacterial activity but all dressings provide an antibacterial action, involving several methods of delivery. Nanocrystalline technology appears to give the highest, sustained release of silver to a wound without clear risk of toxicity.

Silver absorption and antibacterial efficacy of silver dressings

To evaluate the patterns of silver release from selected sustained silver-release dressings and the protective role of proteins in wound exudate and wound scale. The bactericidal action of silver in chronic wound therapy is also examined. Sequential microbiological examination of wound swabs from seven patients with chronic wounds and sampling of wound exudate and wound scale. Silver content was measured using atomic absorption spectrometry. The ability of Contreet Foam to absorb exudate and release silver was studied in punch biopsy wounds in a rodent model. Silver accumulation in wound exudate correlated well with its viscosity and protein content. Silver bound to wound scale and debris was approximately proportional to the silver ion release from dressings. Bacterial burden was controlled, but not eliminated, following chronic silver therapy. Silver dressings (Acticoat-7, Actisorb Silver, Contreet Foam, Aquacel Ag and Flamazine) were found to be safe for use in chronic wound therapy. Excess silver ion is bound by wound exudate and wound scale as a protective mechanism. Silver-release dressings are not likely to result in germ-free wounds. Further studies are needed to examine potential silver resistance.

The silver‐releasing foam dressing, Contreet Foam, promotes faster healing of critically colonised venous leg ulcers: a randomised, controlled trial

The study compared the effect of a sustained silver-release foam dressing (Contreet Foam) with a foam dressing (Allevyn Hydrocellular) without added silver in critically colonised venous leg ulcers with delayed healing. The study was a multicentre, open, randomised, controlled study lasting for 4 weeks. Ulcer area and healing were assessed weekly. Odour, maceration, absorption capacity and leakage were evaluated at dressing changes. All adverse events were recorded. One hundred and twenty-nine patients were included (Contreet Foam: 65, Allevyn Hydrocellular: 64). The two groups were comparable in all respects. After 4 weeks, there was a significantly greater reduction in ulcer area in the Contreet Foam group (45%) than in the Allevyn Hydrocellular group (25%). After 1 and 4 weeks, odour was present in significantly less of the ulcers in the Contreet Foam group (17% and 19%, respectively) compared with the Allevyn Hydrocellular group (47% and 39%, respectively) and at the final visit there were significantly fewer leakages in the Contreet Foam group (19%) compared with the Allevyn Hydrocellular group (49%). Also, less maceration was observed after 1 and 4 weeks in the Contreet Foam group (34% and 37%, respectively) compared with the Allevyn Hydrocellular group (55% and 48%, respectively). The occurrence and cause of adverse events were equally distributed between the study groups. The present study provides evidence of the superior performance of the silver-releasing dressing, Contreet Foam, compared with a traditional moist foam wound healing dressing in the treatment of critically colonised, chronic venous leg ulcers. The results of this randomised, controlled study suggest an important role of sustained silver-releasing dressings in the treatment of critically colonised chronic wounds.

A review of the use of silver in wound care: facts and fallacies.

This review traces the use of silver in wound care, discussing its merits as an antibacterial agent and constituent of many new dressings, which are increasingly tailored to the treatment of wounds ranging from acute surgical lesions to chronic and diabetic leg ulcers. Misconceptions regarding the biological properties of silver, its possible physiological value in the human body and wound bed, absorption through the skin, and safety factors are addressed. The article aims to present silver and the new range of sustained silver-release dressings as important features in the management of skin wounds, providing effective control of wound infections while ensuring patient comfort and quality of life.

Sustained release of silver from periodontal wafers for treatment of periodontitis

Periodontal wafers intended to treat the underlying infections in patients with periodontitis have been developed. The wafers consist of poly(lactic-co-glycolic acid) as a primary bioerodible polymeric component, poly(ethylene glycol) as a plasticizer and encapsulation aid, and silver nitrate as the antimicrobial agent. The wafers are capable of sustained in vitro release of bioactive silver for at least 4 weeks. The wafers exhibit silver release that follows erosion kinetics, confirming a bulk erosion/release mechanism. In clinical evaluation, sustained release of silver at bactericidal levels for at least 21 days is observed. Staining of hard and soft tissues due to the released silver is minimal and reversible.