Chiara Rigo

Active Silver Nanoparticles for Wound Healing

In this preliminary study, the silver nanoparticle (Ag NP)-based dressing, Acticoat™ Flex 3, has been applied to a 3D fibroblast cell culture in vitro and to a real partial thickness burn patient. The in vitro results show that Ag NPs greatly reduce mitochondrial activity, while cellular staining techniques show that nuclear integrity is maintained, with no signs of cell death. For the first time, transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) analyses were carried out on skin biopsies taken from a single patient during treatment. The results show that Ag NPs are released as aggregates and are localized in the cytoplasm of fibroblasts. No signs of cell death were observed, and the nanoparticles had different distributions within the cells of the upper and lower dermis. Depth profiles of the Ag concentrations were determined along the skin biopsies. In the healed sample, most of the silver remained in the surface layers, whereas in the unhealed sample, the silver penetrated more deeply. The Ag concentrations in the cell cultures were also determined. Clinical observations and experimental data collected here are consistent with previously published articles and support the safety of Ag NP-based dressing in wound treatment.

Silver Nanoparticles and Mitochondrial Interaction

Nanotechnology has gone through a period of rapid growth, thus leading to the constant increase in the application of engineered nanomaterials in daily life. Several different types of nanoparticles have been engineered to be employed in a wide array of applications due to their high surface to volume ratio that leads to unique physical and chemical properties. So far, silver nanoparticles (AgNps) have been used in many more different medical devices than any other nanomaterial, mainly due to their antimicrobial properties. Despite the promising advantages posed by using AgNps in medical applications, the possible health effects associated with the inevitable human exposure to AgNps have raised concerns as to their use since a clear understanding of their specific interaction with biological systems has not been attained yet. In light of such consideration, aim of the present work is the morphological analysis of the intracellular behavior of AgNps with a diameter of 10 nm, with a special attention to their interaction with mitochondria.

Characterization and evaluation of silver release from four different dressings used in burns care

For centuries silver and silver compounds have been in use to control infection and avoid septicaemia in the care of burns and chronic wounds. Renewed interest has resulted in a number of Ag based dressings that are now widely used in burns centres. Despite extensive use, a systematic study of the chemical composition, release kinetics and biochemical action of these products has yet to be published. In this work we have characterized the morphology of four commercial Ag dressings by scanning electron microscopy and the silver content was determined to range between 1.39 mg/cm(2) and 0.03 mg/cm(2). Release kinetics in three different matrices (ultra pure water, normal saline solution and a human serum substitute) were determined. The highest rates were found in serum substitute, with a maximum of 4099 μg/(hcm(2)) to a minimum of 0.0001 μg/(hcm(2)). Our results show that the mean inhibitory concentrations are exceeded for most common pathogens in serum substitute and sterile water, but the presence of high Cl(-) concentrations tend to inactivate the dressings.

Hydrodynamic chromatography coupled to single-particle ICP-MS for the simultaneous characterization of AgNPs and determination of dissolved Ag in plasma and blood of burn patients

AbstractSilver nanoparticles (AgNPs) are increasingly used in medical devices as innovative antibacterial agents, but no data are currently available on their chemical transformations and fate in vivo in the human body, particularly on their potential to reach the circulatory system. To study the processes involving AgNPs in human plasma and blood, we developed an analytical method based on hydrodynamic chromatography (HDC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) in single-particle detection mode. An innovative algorithm was implemented to deconvolute the signals of dissolved Ag and AgNPs and to extrapolate a multiparametric characterization of the particles in the same chromatogram. From a single injection, the method provides the concentration of dissolved Ag and the distribution of AgNPs in terms of hydrodynamic diameter, mass-derived diameter, number and mass concentration. This analytical approach is robust and suitable to study quantitatively the dynamics and kinetics of AgNPs in complex biological fluids, including processes such as agglomeration, dissolution and formation of protein coronas. The method was applied to study the transformations of AgNP standards and an AgNP-coated dressing in human plasma, supported by micro X-ray fluorescence (μXRF) and micro X-ray absorption near-edge spectroscopy (μXANES) speciation analysis and imaging, and to investigate, for the first time, the possible presence of AgNPs in the blood of three burn patients treated with the same dressing. Together with our previous studies, the results strongly support the hypothesis that the systemic mobilization of the metal after topical administration of AgNPs is driven by their dissolution in situ. Graphical AbstractSimplified scheme of the combined analytical approach adopted for studying the chemical dynamics of AgNPs in human plasma/blood

Development and application of methods for the determination of silver in polymeric dressings used for the care of burns

Open vessel and microwave digestion methods have been developed for the determination of total silver in six commercial dressing used for the treatment of skin burns. An extraction method using TMAH has also been developed to determine the amount of silver present in the exudates found on the surface after dressing removal so an estimation of the patient dose can be made. All microwave methods had a quantitative recovery, whereas the open vessel had recoveries that ranged from 80 to 100%. The silver concentrations were determined by inductively coupled plasma mass spectrometry using an external calibration. In the absence of suitable reference materials, isotope dilution analysis was applied to validate the accuracy of results obtained by external calibration. All the products had a total Ag content that agreed with the values declared by the producer, which ranged from 10 to 0.2% Ag by weight. One of the methods was applied to the indirect determination of Ag released in vivo by Acticoat™ Flex 3, a dressing composed of silver nanoparticles on a polymer net. Silver levels were determined in used dressings after application to patients with partial thickness skin burns. A maximum of 62% of the silver was found to have been released onto the patient where hemopurulent exudate occurred, indicating that the dressing was virtually exhausted after 3 days of use. We conclude that the Ag released into the patients tissues is closely correlated with the local severity of the wound.