Silver Hydrogel Research Articles

Preparation of silver nanoparticle-containing semi-interpenetrating network hydrogels composed of pluronic and poly(acrylamide) with antibacterial property

In this investigation, we prepared semi-interpenetrating network (IPN) hydrogels composed of pluronic and poly(acrylamide), using free radical polymerization with a redox initiator system in the presence of N, N′-methylenebisacrylamide. The hydrogels served as templates for producing highly stable and uniformly distributed silver nanoparticles via in situ reduction of silver nitrate (AgNO 3) using sodium borohydride (NaBH 4) as reducing agent. We confirmed the formation of silver nanoparticles using ultraviolet visible (UV–vis) spectroscopy and X-ray diffraction (XRD). Stability and morphology of the nanoparticles was examined using thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Finally, we demonstrated the presence of antibacterial activity in the developed hydrogel–silver nanocomposite.

Silver or Nitrofurazone Impregnation of Urinary Catheters Has a Minimal Effect on Uropathogen Adherence

Bacterial adherence to the urinary catheter is an early step in biofilm formation and the pathogenesis of catheter associated urinary tract infection. We studied in vitro the effect of silver or nitrofurazone impregnation of urinary catheters on uropathogen ability to adhere to urinary catheters. We studied commercially available nitrofurazone-silicone, silicone only, silver-silicone-hydrogel, silicone-hydrogel, silver-latex-hydrogel and latex-hydrogel catheters. Catheters were incubated in sterile broth for 0, 3, 5, 7 and 10 days, respectively, before inoculation and overnight incubation with Escherichia coli or Enterococcus faecalis. Adherence of E. coli and E. faecalis to nitrofurazone catheters was significantly decreased compared to that of silicone-only catheters when catheters were fresh. The anti-adherence effect of nitrofurazone on E. coli decreased with time but was still significant at 5 days. For E. faecalis the effect of nitrofurazone was lost by 3 days of pre-incubation. E. coli adherence was not significantly decreased on silver impregnated catheters compared to that on control catheters of the same base material. Silver was associated with a significant decrease in E. faecalis adherence to latex-hydrogel catheters but not to silicone-hydrogel catheters. The adherence of each species to silicone catheters with hydrogel was significantly lower than that to silicone-only control catheters. Silver impregnation had little effect on bacterial adherence in our model and nitrofurazone impregnation had a significant effect only for the first 5 days. Our results do not support a role for silver urinary catheters to prevent catheter associated urinary tract infection by decreasing bacterial adherence.

Hydrogel–silver nanoparticle composites: A new generation of antimicrobials

AbstractDesign of consistant and eco‐friendly methods for the synthesis of silver nanoparticles (AgNPs) is a significant forward direction in the field of application of antibacterial bionanotechnology. One among the available options is hydrogel templates, which are highly useful to achieve this goal. This investigation involves the development of poly(acrylamide)/poly(vinyl alcohol) hydrogel–silver nanocomposites (HSNCs) to achieve AgNPs of ∼2–3 nm size in gel networks. The nanocomposite synthesis process is quite convenient, direct, and very fast, and the obtained hydrogel AgNP composites can be used for antibacterial and wound dressing applications. All the nanocomposite aqueous solutions have shown absorption peaks at 420 nm in UV–visible absorption spectrum corresponding to the Plasmon absorbance of AgNPs. X‐ray diffraction spectrum of the HSNC exhibited 2θ values matching with silver nanocrystals. Transmission electron microscopy images of nanocomposites represent discrete AgNPs throughout the gel networks in the range of 2–3 nm. The developed nanocomposites were evaluated for antibacterial application on E. coli. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Silver hydrogel urinary catheters: Evaluation of safety and efficacy in single patient with chronic spinal cord injury

Urinary tract infections (UTIs) are a large health burden for patients with spinal cord injury (SCI) who have neurogenic bladder dysfunction, especially those patients using indwelling catheters. One method that has shown promise in recent years is the use of a silver hydrogel catheter (SHC). This article describes the outcome of a subject who was part of a prospective, randomized, double-blind study and assigned to use an SHC for 6 months. Using the indwelling SHC effectively prevented this subject from developing a symptomatic UTI. He did not display any symptoms suggestive of silver toxicity or increased serum levels of silver with chronic use of the device. Although no general conclusions can be drawn from this single-subject observation, the results suggest that SHC use has a positive effect. Use of this catheter for persons with neurogenic bladder dysfunction after SCI should be explored further with a study design that optimizes subject recruitment.

Breathing‐in/breathing‐out approach to preparing nanosilver‐loaded hydrogels: Highly efficient antibacterial nanocomposites

AbstractThe key objective of developing novel materials for hygienic living conditions is to lower the risk of transmitting diseases and biofouling. To this end, a number of silver–hydrogel nanocomposite systems are under development. In this study, we attempted a unique strategy to prepare silver‐nanoparticle‐loaded poly(acrylamide‐co‐N‐vinyl‐2‐pyrolidone) hydrogel composites. To load nanosilver particles into such a nonionic hydrogel, a novel breathing‐in/breathing‐out (BI–BO) approach was employed. As the number of BI–BO cycles increased, the amount of the silver nanoparticles loaded into these hydrogels also increased. This behavior was obvious and was confirmed by ultraviolet–visible spectroscopy and thermal analysis. Furthermore, the hydrogel–silver‐nanoparticle composites were confirmed with Fourier transform infrared spectroscopy and transmission electron microscopy studies. Antibacterial studies of these hydrogel–silver nanocomposites showed excellent results against Escherichia coli. The antibacterial activity increased with the number of BI–BO cycles, and samples that underwent three BI–BO cycles showed optimal bactericidal activity. The degree of crosslinking and the silver content had a great influence on the antibacterial efficacy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Controlled silver nanoparticles synthesis in semi-hydrogel networks of poly(acrylamide) and carbohydrates: A rational methodology for antibacterial application

In the present study, we report the preparation of semi interpenetrating hydrogel networks (SIHNs) based on cross-linked poly (acrylamide) prepared through an optimized rapid redox-solution polymerization with N, N′-methylenebisacrylamide (MBA) in presence of three different carbohydrate polymers, namely gum acacia (GA), carboxymethylcellulose (CMC) and starch (SR). Highly stable and uniformly distributed silver nanoparticles have been obtained with hydrogel networks as nanoreactors via in situ reduction of silver nitrate (AgNO 3) using sodium borohydride (NaBH 4) as reducing agent. The formation of silver nanoparticles has been confirmed with ultraviolet visible (UV–vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analyses. Thermogravimetric analysis (TGA) provides the amounts of silver nanoparticles exist in the hydrogel networks. Transmission electron microscopy (TEM) results demonstrate that acacia employed hydrogels have regulated the silver nanoparticles size to 2–5 nm where as CMC and starch composed hydrogel networks result in a heterogeneous size from 2 to 20 nm. The preliminary antibacterial activity performed to these hydrogel–silver nanocomposites.

Stimuli-responsive hydrogel–silver nanoparticles composite for development of localized surface plasmon resonance-based optical biosensor

In this paper, the development of a localized surface plasmon resonance (LSPR)-based optical enzyme biosensor using stimuli-responsive hydrogel–silver nanoparticles composite is described. This optical enzyme biosensor was constructed by immobilizing glucose oxidase (GOx) into the stimuli-responsive hydrogel. When a sample solution such as glucose was applied to the surface of this optical enzyme biosensor, the interparticle distances of the silver nanoparticles present in the stimuli-responsive hydrogel were increased, and thus the absorbance strength of the LSPR was decreased. Furthermore, hydrogen peroxide, which was produced by the enzymatic reaction, induced the degradation of highly clustered silver nanoparticles by the decomposition of hydrogen peroxide. Hence, a drastic LSPR absorbance change, which depends on the glucose concentrations, could be observed. On the basis of the abovementioned mechanism, the characterization of the LSPR-based optical enzyme biosensor was carried out. It was found that the LSPR-based optical enzyme biosensor could be used to specifically determine glucose concentrations. Furthermore, the detection limit of this biosensor was 10 pM. Therefore, this LSPR-based optical enzyme biosensor has the potential to be applied in cost-effective, highly simplified, and highly sensitive test kits for medical applications.

First successful design of semi-IPN hydrogel–silver nanocomposites: A facile approach for antibacterial application

Semi-IPN hydrogels in which poly(vinyl pyrrolidone) (PVP) chains were physically dispersed throughout poly(acrylamide) (PAM) gel networks were synthesized. These semi-IPN hydrogel networks can act as excellent nanoreactors for producing and stabilizing metal nanoparticles. The current methodology allows us to entrap metal nanoparticles throughout hydrogel networks via PVP chains. An optimized semi-IPN hydrogel formulation was found to produce silver nanoparticles, ca. 3–5 nm. The synthesized semi-IPN hydrogel–silver nanocomposites were fully characterized by using UV–vis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The developed semi-IPN hydrogel–silver nanocomposite (SHSNC) was evaluated for preliminary antibacterial applications.

A versatile strategy to fabricate hydrogel–silver nanocomposites and investigation of their antimicrobial activity

In this study, hydrogel–silver nanocomposites have been synthesized by a unique methodology, which involves formation of silver nanoparticles within swollen poly (acrylamide- co-acrylic acid) hydrogels. The formation of silver nanoparticles was confirmed by transmission electron microscopy (TEM) and surface plasmon resonance (SPR) which was obtained at 406 nm. The TEM of hydrogel–silver nanocomposites showed almost uniform distribution of nanoparticles throughout the gel networks. Most of the particles, as revealed from the particle-size distribution curve, were 24–30 nm in size. The X-ray diffraction pattern also confirmed the face centered cubic (fcc) structure of silver nanoparticles. The nanocomposites demonstrated excellent antibacterial effects on Escherichia coli (E. coli). The antibacterial activity depended on size of the nanocomposites, amount of silver nanoparticles, and amount of monomer acid present within the hydrogel–silver nanocomposites. It was also found that immersion of plain hydrogel in 20 mg/30 ml AgNO 3 solution yielded nanocomparticle–hydrogel composites with optimum bactericidal activity.

Antibiofilm Activity of GlmU Enzyme Inhibitors against Catheter-Associated Uropathogens

The colonization of uropathogenic bacteria on urinary catheters resulting in biofilm formation frequently leads to the infection of surrounding tissue and often requires removal of the catheter. Infections associated with biofilms are difficult to treat since they may be more than 1,000 times more resistant to antibiotics than their planktonic counterparts. We have developed an antibiofilm composition comprising an N-acetyl-D-glucosamine-1-phosphate acetyltransferase (GlmU) inhibitor and protamine sulfate, a cationic polypeptide. The antibiofilm activity of GlmU inhibitors, such as iodoacetamide (IDA), N-ethyl maleimide (NEM), and NEM analogs, including N-phenyl maleimide, N,N'-(1,2-phenylene)dimaleimide (oPDM), and N-(1-pyrenyl)maleimide (PyrM), was tested against that of catheter-associated uropathogens. Both IDA and NEM inhibited biofilm formation in Escherichia coli. All NEM analogs showed antibiofilm activity against clinical isolates of E. coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus epidermidis, and Enterococcus faecalis. The combination of oPDM with protamine sulfate (PS) enhanced its antibiofilm activity and reduced its effective concentration to as low as 12.5 microM. In addition, we found that the in vitro inhibitory activity of oPDM-plus-PS-coated silicone catheters against P. aeruginosa and S. epidermidis colonization was superior to that of catheters coated with silver hydrogel. Confocal scanning laser microscopy further confirmed that the oPDM-plus-PS-coated silicone catheters were almost free from bacterial colonization. Thus, a broad-spectrum antibiofilm composition comprising a GlmU inhibitor and protamine sulfate shows promise for use in anti-infective coatings for medical devices, including urinary catheters.

What are the clinical benefits and economic impact associated with the use of a silver hydrogel urinary catheter utilizing a novel bacteriostatic collection system)?

BACKGROUND: Silver/hydrogel (SC) urinary catheters have been shown to reduce the incidence of catheter-associated urinary tract infections (CAUTIs).The impact of using the SC in combination with a novel bacteristatic safety collection system (BSC) has not been documented. OBJECTIVE: Determine the clinical and financial impact of using the SC/BCS consisting of: a silver/hydrogel catheter, bacteriostatic drainage tube, bacteriostatic collection bag, microbicidal outlet tube, and a safety sample port. METHODS: Retrospective rates of CAUTIs were known because monitoring of CAUTIs is part of the institution's surveillance program. Use of the SC/BCS was instituted in July 2002. The facility utilized the SC/BCS housewide, and surveillance of CAUTIs continued for 2 years. Policies and procedures for insertion and care of Foley catheters were not modified. RESULTS: There were 181 infections within 117,803 patient-days (1.54 CAUTIs per 1000 patient days) in the baseline period (July 2001–July 2002), 124 infections within 113,669 patient days (1.09 CAUTIs per 1000 patient days) during the first year, and there were 112 CAUTIs within 101,913 patient days (1.02 CAUTIs for the second year. There is a positive correlation (0.0940), between the three-year data with a probability of 0.2251, suggesting that use of SC/BCS decreases CAUTIs. Using the average cost for a CAUTI of $3803; a net savings of $258,604 was computed for the two-year period. CONCLUSION: Use of the SC/BSC revealed a significant reduction in the incidence of CAUTIs. The hospital is committed to providing extraordinary care to the patients and now utilizes the SC/BCS as the standard practice of care.

Silver-Coated Endotracheal Tubes Associated With Reduced Bacterial Burden in the Lungs of Mechanically Ventilated Dogs

To evaluate the influence of silver-coated endotracheal tubes on the lung bacterial burden of mechanically ventilated dogs. Randomized, double-blinded, controlled experiment. Animal research facility of a regional medical university. Eleven healthy adult dogs. The dogs were intubated either with cuffed, noncoated endotracheal tubes or with endotracheal tubes having a novel antimicrobial silver hydrogel coating and were challenged with buccal administration of Pseudomonas aeruginosa. The silver coating delayed the appearance of bacteria on the inner surface of the endotracheal tubes ([mean +/- SD] duration of mechanical ventilation before appearance of bacteria, 3.2 +/- 0.8 days; mean duration of mechanical ventilation, 1.8 +/- 0.4 days; p = 0.016). The mean total aerobic bacterial burden in the lung parenchyma was statistically lower among the dogs receiving the silver-coated endotracheal tubes compared to those not receiving them (4.8 +/- 0.8 vs 5.4 +/- 9 log cfu/g lung tissue, respectively; p = 0.010). Pronounced differences were seen in the gross and histologic assessments of inflammation in the lung. Using an increasing severity scale of 0 to 12 to assess four components of histology (ie, hyperemia, edema, cellular infiltration, and bacterial presence), dogs receiving noncoated endotracheal tubes had statistically greater histology scores compared to dogs receiving silver-coated endotracheal tubes (7.1 plus minus 1.6 vs 2.8 plus minus 1.2, respectively; p < 0.001). These results suggest that the silver coating of endotracheal tubes may delay the onset of and decrease the severity of lung colonization by aerobic bacteria. Based on these results, clinical studies are planned to determine the safety and clinical efficacy of silver-coated endotracheal tubes in patients requiring mechanical ventilation in the ICU setting.

Activities of a nitrofurazone-containing urinary catheter and a silver hydrogel catheter against multidrug-resistant bacteria characteristic of catheter-associated urinary tract infection.

The in vitro inhibitory activity of a nitrofurazone-coated urinary catheter (NFC) against 86 recently obtained susceptible and multidrug-resistant (MDR) clinical isolates of Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Staphylococcus aureus, coagulase-negative staphylococci, and Enterococcus faecium, which are species implicated in catheter-associated urinary tract infection and which traditionally have been susceptible to nitrofuran derivatives, was determined using an agar diffusion assay. In a subset of these strains, the activity of the NFC was compared with that of a silver hydrogel urinary catheter (SHC), and the durability of each catheter's inhibitory activity was assessed during serial daily transfers of catheter segments to fresh culture plates. Except for vancomycin-resistant E. faecium, the NFC was active against all isolates tested and showed comparable inhibition zones with susceptible and MDR strains of each species. In contrast, the SHC inhibited only certain staphylococci (P < 0.01 versus the NFC), and among these strains, the SHC produced smaller inhibition zones than did the NFC (P < 0.01). Inhibition was evident for up to 5 days with the NFC, but for only 1 day (if at all) with the SHC (P < 0.01). These data document that, for most genera which traditionally have been susceptible to nitrofuran derivatives, the NFC remains active against contemporary MDR isolates. They also demonstrate that the in vitro antibacterial activity of the NFC is markedly superior to that of the SHC in several respects. Thus, the NFC shows promise for clinical use in the current era of MDR bacteria.