Mauro Pollini

Characterization of antibacterial silver coated yarns

Surface treatments of textile fibers and fabrics significantly increase their performances for specific biomedical applications. Nowadays, silver is the most used antibacterial agent with a number of advantages. Among them, it is worth to note the high degree of biocompatibility, an excellent resistance to sterilization conditions, antibacterial properties with respect to different bacteria associated with a long-term of antibacterial efficiency. However, there are only a few antibacterial fibres available, mainly synthetic with high production cost and limited effectiveness. Cotton yarns with antimicrobial properties are most suitable for wound healing applications and other medical treatments thanks to their excellent moisture absorbance while synthetic based fibres are most suitable for industrial applications such as automotive tapestry and air filters. The silver-coated fibers were developed applying an innovative and low cost silver deposition technique for natural and synthetic fibers or yarns. The structure and morphology of the silver nanoclusters on the fibers was observed by scanning electron microscopy (SEM), atomic force microscopy analysis (AFM) and XRD analysis, and quantitatively confirmed by thermogravimetric analysis (TGA) measurements. Good silver coating stability has been confirmed performing several industrial washing. Antimicrobial tests with Escherichia coli were performed.

Metal-Based Antibacterial Substrates for Biomedical Applications

The interest in nanotechnology and the growing concern for the antibiotic resistance demonstrated by many microorganisms have recently stimulated many efforts in designing innovative biomaterials and substrates with antibacterial properties. Among the implemented strategies to control the incidence of infections associated with the use of biomedical device and implants, interesting routes are represented by the incorporation of bactericidal agents onto the surface of biomaterials for the prevention of bacterial adhesion and biofilm growth. Natural products and particularly bioactive metals such as silver, copper and zinc represent an interesting alternative for the development of advanced biomaterials with antimicrobial properties. This review presents an overview of recent progress in the modification of biomaterials as well as the most attractive techniques for the deposition of antimicrobial coatings on different substrates for biomedical application. Moreover, some research activities and results achieved by the authors in the development of antibacterial materials are also presented and discussed.

Efficacy of silver treated catheters for haemodialysis in preventing bacterial adhesion

The growing resistance of many strains of bacteria to antibiotics and antiseptics is becoming a serious problem in medicine. Nano-silver is one of the most prominent products in medicine because it exhibits unusual physicochemical properties and a strong biological activity. In this work an innovative silver deposition technology was applied to temporary polyurethane catheters for haemodialysis. The working conditions of catheters were reproduced through laboratory equipment that ensured the flow of deionized water and simulated body fluid inside the lumina at corporeal temperature. The growth and the adhesion of Staphylococcus aureus on the surface of the device were studied through fluorescence microscopy. ICP-AES was adopted to calculate the amount of silver released from the substrate. The stability of the coating during the whole working life of the device was demonstrated through thermo-gravimetric analysis.

Metal nanoantimicrobials for textile applications

Abstract Research on the nanomaterials containing one or more transition metals is growing tremendously, thanks to the large number of preparation processes available and to the novel applications that can be envisaged in several fields. This review presents an overview of the selected studies in the field of antimicrobial textiles, employing bioactive nanophases of elements/compounds such as silver, copper, or zinc oxide. In addition, the history of use of these antimicrobials and their mechanism of action are shortly reported. Finally, a short description is provided of the deposition/preparation methods, which are being used in the authors’ labs for the development of the textiles modified by the novel nanoantimicrobials.

Development of antibacterial and antifungal silver-coated polyurethane foams as air filtration units for the prevention of respiratory diseases

The development of silver‐coated polyurethane filters as filtration units for the prevention of the respiratory diseases.

Development of silver nano-coatings on silk sutures as a novel approach against surgical infections.

The infections give rise to a range of clinical problems and prolong hospitalization with increased healthcare costs. Moreover, persistent infections exasperate the problem of antibiotic resistance. The aim of this study was the development of effective and low-cost antibacterial silver coatings on surgical sutures by adopting an innovative photochemical deposition process to prevent early contamination of surgical wounds. The silver deposition technology adopted in this work is an innovative process based on the in situ photoreduction of a silver solution. The samples were dipped in the silver solution and then exposed to UV radiation in order to induce the synthesis of silver clusters on the surface of the suture. The homogeneous distribution of silver particles on the surface and on the cross-section of the treated sutures was demonstrated. All the antibacterial studies clearly demonstrated that the use of novel silver treated sutures could represent clinical advantages in terms of the prevention of surgical infections against bacterial colonization. The silver coating deposited on the sutures demonstrated no cytotoxic effect on a selected cell population. The results obtained suggested that the antibacterial silver-coated sutures developed in this work could represent an interesting alternative to conventional sutures, with evident advantages in terms of prevention of the surgical infections and on the health costs. In addiction, very low concentrations of silver significantly inhibited the microbial load, without affecting the cell viability.

Antibacterial natural leather for application in the public transport system

In the public transport system, hand-touch surfaces such as seats in buses, trains, trams, and airplanes represent a reservoir of bacteria and a potential risk for contamination among passengers. The antimicrobial activity of silver has been known since ancient times. In this work, natural leather commonly used in the public transport system was treated with silver through the in situ photoreduction of a silver solution. The morphology of the coating and the distribution of silver clusters were studied by scanning electron microscopy and by energy dispersive X-ray spectroscopy. The amount of silver on the surface was quantified by thermo-gravimetric analysis. The antibacterial capability of the treated materials was checked against Gram-positive and Gram-negative bacteria. Taber test was conducted on silver treated samples in order to study the durability of the treatment. The morphology of the silver coating and its antibacterial capability were analyzed also after the Taber test.

Engineering Nanostructured Silver Coatings for Antimicrobial Applications

Surface engineering based on the application of silver nanoparticles is emerging as one of the most promising in the nanotechnology field. The well-known antimicrobial activity of silver is emphasized by the high specific surface which grows inversely to the particle dimensions. In this chapter, various properties and applications of antibacterial silver coating are reviewed. In particular, an innovative deposition technology of silver nanoclusters on various natural and synthetic substrates developed by the authors is described. The deposition of strongly adhered silver nanostructures was obtained by a wet chemical method followed by a UV curing process. A very close view of the microstructure of the silver nanoclusters on the coated substrates has been obtained using advanced diagnostic tools: TEM, SEM, EDX. The strong antimicrobial capabilities of the treated substrates was evidenced with systematic antibacterial tests with Escherichia coli.

In vivo testing of silver treated fibers for the evaluation of skin irritation effect and hypoallergenicity

Textiles are a fertile breeding ground for a multitude of micro-organisms under appropriate conditions of moisture and temperature. The broad-spectrum biocide properties of silver are well known and many technologies have been developed so far to treat textiles with silver. The efficacy of the silver deposition technology presented in this article has been already demonstrated in previous works, where the strong adhesion of silver nanoparticles to the substrate and their antibacterial capability have been assessed. This work focuses on the evaluation of any possible interaction of silver treated cotton with human skin, in terms of skin irritation and hypoallergenicity. Moreover, the presence of silver and the antibacterial capability against Gram positive and Gram negative bacteria, namely Staphylococcus aureus and Escherichia coli, were verified even after several washing cycles in order to develop a product with long-term antibacterial capability and no adverse effects in terms of skin irritation and hypoallergenicity.

In Vitro Assessment of the Antibacterial Potential of Silver Nano-Coatings on Cotton Gauzes for Prevention of Wound Infections

Multidrug-resistant organisms are increasingly implicated in acute and chronic wound infections, thus compromising the chance of therapeutic options. The resistance to conventional antibiotics demonstrated by some bacterial strains has encouraged new approaches for the prevention of infections in wounds and burns, among them the use of silver compounds and nanocrystalline silver. Recently, silver wound dressings have become widely accepted in wound healing centers and are commercially available. In this work, novel antibacterial wound dressings have been developed through a silver deposition technology based on the photochemical synthesis of silver nanoparticles. The devices obtained are completely natural and the silver coatings are characterized by an excellent adhesion without the use of any binder. The silver-treated cotton gauzes were characterized through scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA) in order to verify the distribution and the dimension of the silver particles on the cotton fibers. The effectiveness of the silver-treated gauzes in reducing the bacterial growth and biofilm proliferation has been demonstrated through agar diffusion tests, bacterial enumeration test, biofilm quantification tests, fluorescence and SEM microscopy. Moreover, potential cytotoxicity of the silver coating was evaluated through 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide colorimetric assay (MTT) and the extract method on fibroblasts and keratinocytes. Inductively coupled plasma mass spectrometry (ICP-MS) was performed in order to determine the silver release in different media and to relate the results to the biological characterization. All the results obtained were compared with plain gauzes as a negative control, as well as gauzes treated with a higher silver percentage as a positive control.