Silver Release Kinetics Research Articles

Multifunctional ternary composite films based on PLA and Ag/alginate microbeads: Physical characterization and silver release kinetics

Novel multifunctional composite poly(lactic acid) (PLA) films with alginate microbeads containing silver nanoparticles (AgNPs) were developed for potential antimicrobial food packaging applications. AgNPs, 10–20 nm in size, were synthesized in a Na-alginate solution by a hydrothermal method yielding a sterile, pH neutral colloid solution of low viscosity that was electrostatically extruded to produce Ag/alginate microbeads (190 μm in size) with retained AgNPs. Dried microbeads were uniformly dispersed in PLA films with retained AgNPs as confirmed by UV–Vis spectroscopy and scanning electron microscopy. The films were characterized regarding thermal and mechanical properties as well as silver release in different food simulants. Results show that PLA matrix served as a diffusion barrier so that the released silver concentration in water after 10 days was within the prescribed limit of 0.05 mg kg−1 while the films induced inhibitory effects against Staphylococcus aureus in the agar diffusion test.

Silver/poly(vinyl alcohol)/chitosan/graphene hydrogels – Synthesis, biological and physicochemical properties and silver release kinetics

This study presents the synthesis of novel silver/poly(vinyl alcohol)/chitosan/graphene (Ag/PVA/CHI/Gr) nanocomposite hydrogels by in situ electrochemical reduction of silver ions in the hydrogel matrix and their thorough characterization by UV–visible and Raman spectroscopies, field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and silver release measurements. The influence of chitosan content on the incorporation and stabilization of silver nanoparticles (AgNPs) was investigated, and we found that hydrogels with higher chitosan content contain higher amounts of AgNPs. In addition, the cytotoxicity and antibacterial activity of Ag/PVA/CHI/Gr nanocomposite hydrogels were evaluated. Based on in vitro investigations, the obtained materials exhibit diffusion-controlled release profiles over 28 days, strong antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial strains, and no cytotoxicity toward human and mice fibroblast cell lines.

An effective treatment of experimental osteomyelitis using the antimicrobial titanium/silver-containing nHP66 (nano-hydroxyapatite/polyamide-66) nanoscaffold biomaterials.

Effective treatment of osteomyelitis remains a formidable clinical challenge. The rapid emergence of multidrug-resistant bacteria has renewed interest in developing antimicrobial biomaterials using antiseptic silver ions to treat osteomyelitis. However, inadequate local retention and severe cytotoxic effects have limited the clinical use of ionic silver for bone grafts. We recently developed novel porous nano-hydroxyapatite/polyamide 66 (nHP66)-based nanoscaffold materials containing varied concentrations of silver ions (Ag+) (TA-nHAPA66) and oxidized titanium (TiO2), which was added as a second binary element to enhance antibacterial activity and biocompatibility. In this study, we establish a large cohort of rabbit model of experimental osteomyelitis and investigate the in vivo antimicrobial and therapeutic effects of TA-nHP66 biomaterials and their in vivo silver release kinetics. We find the TA-nHP66 scaffolds exhibit potent antibacterial activities against E. coli and S. aureus, support cell adhesion and cell proliferation of pre-osteoblasts, and stimulate osteogenic regulator/marker expression. Moreover, the TA2-nHP66 scaffold exerts potent antibacterial/anti-inflammation effects in vivo and promotes bone formation at the lesion site of osteomyelitis. We further demonstrate that TA2-nHP66 exhibits excellent biosafety profile without apparent systemic toxicities. Therefore, the TA-nHP66 scaffold biomaterials may be further explored as an effective adjuvant therapy for infected bone defects and/or osteomyelitis debridement.

Development and characterization of active films based on starch-PVA, containing silver nanoparticles

Abstract In order to obtain antimicrobial packaging films, starch-PVA-based films with silver nanoparticles (AgNPs) have been developed and characterized as to their physical and antimicrobial properties and silver release kinetics to polar (A, B, C and D1) and non-polar (D2) food simulants. Antimicrobial activity against two bacteria, Listeria innocua and Escherichia coli, and two fungi, Aspergillus niger and Penicillium expansum, was studied. Silver-loaded starch-PVA films exhibited antimicrobial activity against the tested microorganisms, which depended heavily on the concentration of AgNPs. Their addition only led to notable physical changes in the colour and transparency of the films, which underwent significant changes and turned brownish-yellow and opaque, this being more notable when the silver concentration rose. Silver was released into aqueous simulants in its entirety within the first 60 min of contact. In the non-polar simulant (oleic acid), the release capacity of the films drastically decreased, being the only case where the established limit (60 mg/kg simulant) was met. As a consequence, the use of the developed films as food packaging materials should be restricted to fat-rich foodstuffs.

Antibacterial potency of different deposition methods of silver and copper containing diamond-like carbon coated polyethylene

BackgroundAntibacterial coatings of medical devices have been introduced as a promising approach to reduce the risk of infection. In this context, diamond-like carbon coated polyethylene (DLC-PE) can be enriched with bactericidal ions and gain antimicrobial potency. So far, influence of different deposition methods and ions on antimicrobial effects of DLC-PE is unclear.MethodsWe quantitatively determined the antimicrobial potency of different PE surfaces treated with direct ion implantation (II) or plasma immersion ion implantation (PIII) and doped with silver (Ag-DLC-PE) or copper (Cu-DLC-PE). Bacterial adhesion and planktonic growth of various strains of S. epidermidis were evaluated by quantification of bacterial growth as well as semiquantitatively by determining the grade of biofilm formation by scanning electron microscopy (SEM). Additionally silver release kinetics of PIII-samples were detected.Results(1) A significant (p < 0.05) antimicrobial effect on PE-surface could be found for Ag- and Cu-DLC-PE compared to untreated PE. (2) The antimicrobial effect of Cu was significantly lower compared to Ag (reduction of bacterial growth by 0.8 (Ag) and 0.3 (Cu) logarithmic (log)-levels). (3) PIII as a deposition method was more effective in providing antibacterial potency to PE-surfaces than II alone (reduction of bacterial growth by 2.2 (surface) and 1.1 (surrounding medium) log-levels of PIII compared to 1.2 (surface) and 0.6 (medium) log-levels of II). (4) Biofilm formation was more decreased on PIII-surfaces compared to II-surfaces. (5) A silver-concentration-dependent release was observed on PIII-samples.ConclusionThe results obtained in this study suggest that PIII as a deposition method and Ag-DLC-PE as a surface have high bactericidal effects.

Kinetics of silver release from microfuel with taking into account the limited-solubility effect

The effect of a limited solubility of silver in silicon carbide on silver release from a microfuel with a TRISO coating is studied. It is shown that a limited solubility affects substantially both concentration profiles and silver release from a microfuel over a broad range of temperatures. A procedure is developed for obtaining fission-product concentration profiles in a microfuel and graphs representing the flow and integrated release of fission products on the basis of data from neutron-physics calculations and results obtained by calculating thermodynamics with the aid of the Ivtanthermo code and kinetics with the aid of the FP-Kinetics code. This procedure takes into account a limited solubility of fission products in protective coatings of microfuel.

Regenerable antimicrobial activity in polyamide thin film nanocomposite membranes

Control of microbial growth at the membrane surface on a continuous basis is needed to mitigate biofouling in long term membrane applications. In this study, a regenerable antimicrobial nanocomposite membrane was developed for sustainable membrane biofouling control via slow release of silver. Nanozeolites attached to the surface of a commercial polyamide nanofiltration membrane by covalent binding served as carriers for Ag+ or Ag(0). At a silver loading of 7.18±0.62mg/m2, the nanocomposite membranes effectively inhibited growth of P. aeruginosa for up to seven 24 h exposure cycles, and the antimicrobial efficacy correlated well with silver release kinetics data. The release of silver strongly depended on the Cl− concentration in the solution. At low Cl− concentrations, the low aqueous solubility of silver controlled silver release; the Ag+ and Ag(0) loaded membranes showed similar release rate. At high Cl− concentration, silver release from the Ag(0) loaded membrane was notably more stable and longer lasting as Ag(0) oxidation became the rate-limiting step. After depletion, reloading silver via a simple physisoprtion protocol resumed the antimicrobial activity. The regenerated membranes had similar silver loading and antimicrobial activity as the freshly prepared membranes, demonstrating the potential of this approach in long-term control of membrane biofouling.

Inkjet printing of Chitlac-nanosilver—a method to create functional coatings for non-metallic bone implants

Biostable fiber-reinforced composites, based on bisphenol-A-dimethacrylate and triethyleneglycoldimethacrylate thermoset polymer matrix reinforced with E-glass fibers have been successfully used in cranial reconstructions and the material has been approved for clinical use. As a further refinement of these implants, antimicrobial, non-cytotoxic coatings on the composites were created by an immersion procedure driven by strong electrostatic interactions. Silver nanoparticles (nAg) were immobilized in lactose-modified chitosan (Chitlac) to prepare the bacteriostatic coatings. Herein, we report the use of inkjet technology (a drop-on-demand inkjet printer) to deposit functional Chitlac-nAg coatings on the thermoset substrates. Characterization methods included scanning electron microscopy, scanning white light interferometry and electro-thermal atomic absorption spectroscopy. Inkjet printing enabled the fast and flexible functionalization of the thermoset surfaces with controlled coating patterns. The coatings were not impaired by the printing process: the kinetics of silver release from the coatings created by inkjet printing and conventional immersion technique was similar. Further research is foreseen to optimize printing parameters and to tailor the characteristics of the coatings for specific clinical applications.

Anti-biofilm efficacy of low temperature processed AgCl–TiO2 nanocomposite coating

Biofilms are a major concern in the medical settings and food industries due to their high tolerance to antibiotics, biocides and mechanical stress. Currently, the development of novel methods to control biofilm formation is being actively pursued. In the present study, sol–gel coatings of AgCl–TiO2 nanoparticles are presented as potential anti-biofilm agents, wherein TiO2 acts as a good supporting matrix to prevent aggregation of silver and facilitates its controlled release. Low-temperature processed AgCl–TiO2 nanocomposite coatings inhibit biofilm formation by Escherichia coli, Staphylococcus epidermidis and Pseudomonas aeruginosa. In vitro biofilm assay experiments demonstrated that AgCl–TiO2 nanocomposite coated surfaces, inhibited the development of biofilms over a period of 10days as confirmed by scanning electron microscopy. The silver release kinetics exhibited an initial high release, followed by a slow and sustained release. The anti-biofilm efficacy of the coatings could be attributed to the release of silver, which prevents the initial bacterial adhesion required for biofilm formation.

Bioreactor validation and biocompatibility of Ag/poly(N-vinyl-2-pyrrolidone) hydrogel nanocomposites

Silver/poly(N-vinyl-2-pyrrolidone) (Ag/PVP) nanocomposites containing Ag nanoparticles at different concentrations were synthesized using γ-irradiation. Cytotoxicity of the obtained nanocomposites was determined by MTT assay in monolayer cultures of normal human immunocompetent peripheral blood mononuclear cells (PBMC) that were either non-stimulated or stimulated to proliferate by mitogen phytohemagglutinin (PHA), as well as in human cervix adenocarcinoma cell (HeLa) cultures. Silver release kinetics and mechanical properties of nanocomposites were investigated under bioreactor conditions in the simulated body fluid (SBF) at 37°C. The release of silver was monitored under static conditions, and in two types of bioreactors: perfusion bioreactors and a bioreactor with dynamic compression coupled with SBF perfusion simulating in vivo conditions in articular cartilage.Ag/PVP nanocomposites exhibited slight cytotoxic effects against PBMC at the estimated concentration of 0.4μmoldm−3, with negligible variations observed amongst different cell cultures investigated. Studies of the silver release kinetics indicated internal diffusion as the rate limiting step, determined by statistically comparable results obtained at all investigated conditions. However, silver release rate was slightly higher in the bioreactor with dynamic compression coupled with SBF perfusion as compared to the other two systems indicating the influence of dynamic compression. Modelling of silver release kinetics revealed potentials for optimization of Ag/PVP nanocomposites for particular applications as wound dressings or soft tissue implants.

Functionalizing calcium phosphate biomaterials with antibacterial silver particles.

Antimicrobial silver particles are created on calcium phosphate (CaP) biomaterials by sequentially incubating in citric acid and silver nitrate solutions. The subsequent silver release kinetics and released dosage are controlled by simply changing the solution conditions during growth of silver particles. Released silver efficiently suppresses the growth of gram-positive Staphylococcus aureus and gram-negative Escherichia coli without significant cytotoxicity to eukaryotic cells. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.