Nanostructure Tuning of Gold Nanoparticles Films via Click Sintering.

Colloidal metal nanoparticles dispersions are commonly used to create functional printed electronic devices and they typically require time-, energy- and equipment-consuming post-treatments to improve their electrical and mechanical properties. Traditional methods, e.g. thermal, UV/IR, and microwave treatments, limit the substrate options and may require expensive equipment, not available in all the laboratories. Moreover, these processes also cause the collapse of the film (nano)pores and interstices, limiting or impeding its nanostructuration. Finding a simple approach to obtain complex nanostructured materials with minimal post-treatments remains a challenge. In this study, a new sintering method for gold nanoparticle inks that called as "click sintering" has been reported. The method uses a catalytic reaction to enhance and tune the nanostructuration of the film while sintering the metallic nanoparticles, without requiring any cumbersome post-treatment. This results in a conductive and electroactive nanoporous thin film, whose properties can be tuned by the conditions of the reaction, i.e., concentration of the reagent and time. Therefore, this study presents a novel and innovative one-step approach to simultaneously sinter gold nanoparticles films and create functional nanostructures, directly and easily, introducing a new concept of real-time treatment with possible applications in the fields of flexible electronics, biosensing, energy, and catalysis.

Effect of nitrogen plasma treatment on the crystallinity and self-bonding of polyetheretherketone (PEEK) for biomedical applications.

Polyetheretherketone (PEEK) is a thermoplastic material with outstanding properties and high potential for biomedical applications, including hermetic encapsulation of active implantable devices. Different biomedical grade PEEK films with initial degree of crystallinity ranging from 8% to 32% (with or without mineral filling) were inspected. PEEK surfaces were treated with nitrogen RF plasma and the effects on materials crystallinity and self-bonding were evaluated. In particular, the relationship between auto-adhesive properties and crystalline content of PEEK before and after plasma treatment was examined. PEEK samples showed different bonding strength depending on their degree of crystallinity, with higher self-bonding performance of mineral-filled semi-crystalline films. XRD did not show any modification of the PEEK microstructure as a result of plasma treatment, excluding a significant influence of crystallinity on the self-bonding mechanisms. Nevertheless, plasma surface treatment successfully improved the self-bonding strength of all the PEEK films tested, with larger increase in the case of semi-crystalline unfilled materials. This could be interpreted to the increase in chain mobility that led to interfacial interpenetration of the amorphous phase.

Functional properties and performance of new and reprocessed coronary angioplasty balloon catheters.

The need of health costs control has prompted the reuse of devices originally manufactured for single use only. To assess reprocessing feasibility of disposable medical devices, hygienic, technical, and functional aspects must be taken into account in addition to economical, ethical, and legal implications. This study aims to characterize coronary angioplasty catheters and to evaluate performance changes induced by reprocessing. Multiple analysis including crossing profile, slipperiness, compliance, mechanical, and burst pressure tests were performed at different steps of the protocol on 25 catheters reprocessed up to two times. The results highlighted that both use and reprocessing can affect the features of angioplasty catheters. Mechanical stress caused by clinical inflation and thermal-chemical stress undergone by polymers during cleaning and sterilization procedures caused partial modifications of material properties, inducing an overall shrinking effect on balloons. Compliance tests reported a maximum variation of 6.2% from nominal values, showing the conformity of reprocessed devices with manufacturers' original specifications (+/-10%). The burst pressure of reprocessed devices was 80% higher than the rated burst pressure certified by manufacturers, thus reducing concerns of breakage during reuse. A strict dependence on device model in the behavior of catheters was found, especially for balloons crossing profile and slipperiness. Main changes occurred after the first reprocessing cycle, while a second cleaning and sterilization did not introduce further significant alterations. On the whole, the magnitude of modifications introduced up to two reprocessing cycles did not compromise catheters performance.

Tailored intracellular delivery via a crystal phase transition in 400 nm vaterite particles.

Porous vaterite containers of 400 nm size are studied with respect to intracellular drug delivery applications. A generic crystal phase transition from vaterite to calcite serves as a novel payload release mechanism, which reveals a delayed burst-release. This will permit control of the pharmacokinetics allowing for applications like preventive drug administration or scheduled application of pharmaceuticals during long term therapy. Experiments with two types of payloads, providing different molecular weights and zeta-potentials, demonstrate a flexible way of tailoring the payload delivery time via the molecular properties of the cargo. A dual in vitro cellular uptake experiment with human ovarian carcinoma cells ES2 and human fibroblasts MRC5 shows no cytotoxicity, no influence on cell viability, and fast penetration of substance-loaded containers into cells. Flow cytometry analysis proves high uptake rates and 3D microscopy analysis reveals the intracellular distribution.

Carbon coatings for cardiovascular applications: physico-chemical properties and blood compatibility.

Two different types of carbon coatings for cardiovascular applications were characterized both as regards to their physico-chemical properties and blood compatibility upon contact with human plasma and platelets. The samples were analyzed by means of a wide range of techniques, including scanning electron microscopy (SEM) and atomic force microscopy (AFM), contact angle goniometry, Raman spectroscopy and X-ray Diffraction (XRD). Multiple tests have been performed to evaluate plasma protein adsorption and platelets adhesion and activation, and to investigate possible correlations between the surface properties of the materials and their blood compatibility. We proposed a similar mechanism of blood/material interaction for the carbon-based materials tested. It has been suggested that the characteristic wettability and surface heterogeneity of the coatings guide protein adsorption and retention onto the carbon surfaces, promoting a preferential, extensive and tight adsorption of albumin molecules, that in turn leads to surface passivation and inhibits subsequent platelets adhesion and activation.

Surface properties and blood compatibility of commercially available diamond-like carbon coatings for cardiovascular devices.

The aim of this study was to determine the relationships between the surface properties and blood compatibility of in-use diamond-like carbon (DLC) coatings for cardiovascular components. Commercially available DLC films were characterized with respect to surface topography and wettability, protein adsorption from human plasma, and platelets adhesion/activation. Fibrinogen (Fng) and human serum albumin (HSA) adsorbed onto the sample surfaces were in particular quantified as two of the main proteins involved in blood compatibility. A low tendency of platelets to spread and form aggregates onto the DLC-coated surfaces has been described and related to a low Fng-to-HSA adsorption ratio. This study provides evidence that the rapid and tenacious binding of albumin molecules to DLC materials tends to passivate the surfaces and to inhibit Fng adsorption, thus imparting thromboresistance to the carbon coatings by rendering the surfaces less adhesive and activating for platelets. Albumin preferential adsorption was ascribed to high chemical heterogeneity of the DLC sample surfaces. The DLC films tested present a favorable behavior as regards blood compatibility with respect to platelet thrombus formation by reason of their surface properties.