Mioara Drobota

Bactericidal effect on Foley catheters obtained by plasma and silver nitrate treatments

New medical, materials, and surgical procedures keep improving current health-care practices. Many of these innovations involve polymeric devices that must meet certain clinical and cost requirements. Novel antimicrobial technologies and nanotechnologies are being implemented in more applications such as implant interphases, coatings, and others to avoid postoperatory infections. Here we present a novel approach to create antimicrobial surfaces on Foley catheters widely used in hospitals in order to avoid a variety of harms including infection, pain, and trauma. The combination of plasma and silver nitrate wet treatments demonstrates to be a fast, easy, and convenient method for obtaining colonization-resistant catheter surfaces.

Collagen immobilization on poly(ethylene terephthalate) and polyurethane films after UV functionalization

An attractive alternative method to add new functionalities such as biocompatibility due to the micro- and nanoscaled modification of surfaces is offered by UV-modified polymers. The aim of this study was to evaluate the effect of the UV light functionalization on two polymers, poly(ethylene terephthalate) (PET) and polyurethane (PU) films, by means of atomic force microscopy (AFM), Fourier transform infrared–attenuated total reflectance (FTIR–ATR), and contact angle measurements. Thus, the UV-irradiation activates the polymers surface by breaking some chemical bonds and generation of new functional groups on the surface. This process can be controlled by the irradiation time. The topography provides the formation of superposed ‘nap’ and ‘wall-type’ structures on both untreated and treated samples. The surface parameters were found to depend on the polymer films before and after irradiation. The immobilization of collagen on PET surface was confirmed by X-ray photoelectron spectroscopy measurements and for PU surface was proved by FTIR–ATR. First technique suggests an increase of the nitrogen content at longer UV exposure time, and the second one reveals the appearance of the protein Amide I band. Supplementary, AFM measurements clearly revealed the presence of collagen attached on the polymer surface. Thus, these new UV-irradiated polymers are promising materials in our further attempts to obtain new biofunctionalized surfaces.

Thermal, mechanical and wettability properties of some branched polyetherurethane elastomers

Abstract In this study three series of polyetherurethanes (PEU) based on Terathane ® (polytetramethyleneetherglycol - PTMEG, Mn 1400) as polyol; isophorone diisocyanate (IPDI), 4,4’-methylene-bis-(cyclohexyl-isocyanate) (HMDI) and hexamethylene diisocyanate (HDI) as aliphatic diisocyanate components; 1,4- butanediol (BD) and glycerin (Gly) as chain extenders were synthesized. The glycerin as triol is responsible for the crosslinking structures. All polyether urethanes were synthesized by prepolymer method. The PTMEG was reacted with diisocyanate to realize a diisocyanate-terminated prepolymer, which in next step was extended with blend of the 1,4-butanediol (BD) and glycerin (Gly) in different proportion. The influence of the diisocyanate structure and chain extender functionality on the thermal, mechanical and wettability properties were the aim of this study. The physical, mechanical and wettability properties of these polymers were measured according to standard methods. All polymers were characterized by conventional characterization methods. Different methods of thermal analysis (TGA and DSC) were used for characterization. Wettability was estimated by determination of the dynamic contact angle. The structures were confirmed by FTIR and H-NMR analysis. The results show that the thermal stability, mechanical and wettability properties of the final products are influenced by the diisocyanate and chain extenders nature.

The Effect of Silver Nanoparticles on the Collagen Secondary Structure

Attenuated Total Reflection - Fourier Transform Infrared (ATR-FTIR) spectroscopy is a label-free, non-destructive analytical technique that can be used extensively to study a wide variety of molecules in different conditions. Proteins have very complicated three dimensional structures with multi-level conformations, which are highly correlated with their biological activities. Recently, there is a significant increase of materials based on interaction between proteins and nanoparticles. The aim of this paper is to highlight the understanding of protein interaction with silver nanoparticles (AgNPs) surfaces. Information about the secondary structures of collagen with and without AgNPs was obtained from atomic force microscopy (AFM) measurements.ATR-FTIR spectroscopy was used for monitoring the changes in the secondary structures of collagen upon interaction with AgNPs. Amide I is the most sensitive band for detecting changes in the protein secondary structures. Its characteristic absorption band is located at 1600–1700 cm-1. Comparing the spectra of collagen with and without AgNPs in this region, information about the different types of secondary structures such as α-helix, β-sheets, turns and random coil can be obtained. The conjugation of AgNPs-collagen occurred mainly through electrostatic interactions. Based on these data, the effects of AgNPs stability and the conformational changes of collagen upon interaction with the AgNPs are discussed.

Poly(alkylene sebacate ether)urethane hydrogels for indomethacin delivery formulations

A series of aliphatic polyurethane hydrogels based on poly(alkylene sebacate) diols was developed by polyaddition reaction. The chemical structures of unloaded and indomethacin-loaded poly(alkylene sebacate ether)urethane hydrogels were characterized using ATR-FT-IR spectroscopy. The aim of this research was to study the influence of the long alkylene chains on the indomethacin release rate. The swelling kinetics was analyzed using power law and second-order equation and it was found that both diffusion and polymer relaxation mechanisms control the overall rate of water uptake. The release mechanism follows the same behavior as swelling, but the interaction of the drug with the hydrophobic matrix influences the release kinetics. The surface properties and the influence of the surface configuration on the indomethacin release kinetics were also investigated using contact angle measurements. The mechanical properties of the dry samples were affected by the crosslinker, while, for the swollen samples, the stress–strain curves were overlapping and the mechanical parameter values decrease. The swelling of these hydrogels was also attributed to the network porosity, which was revealed by scanning electron microscopy (SEM) on freeze-dried specimens. The results prove the importance of the polyurethane matrix structure in the development of new drug releasing systems.

Thermal behavior, surface energy analysis, and hemocompatibility of some polycarbonate urethanes for cardiac engineering

The understanding of basic surface properties and the relationships between temperature and the configuration of the polymer surface are the key to further understand the first interaction mechanism of the polymer with the body. To this end, some poly(carbonate tetramethylene ether)urethane (PCEU), poly(carbonate siloxane tetramethylene ether)urethane (PCSiEU), and their 1:1 gravimetric mixture (PCEU/PCSiEU) membranes were prepared. In order to establish the relationships between temperature and the chemical structure of polymer surface, the polyurethane (PU) membranes were analyzed by attenuated total reflectance–Fourier transform infrared spectroscopy. The temperature has a significant influence on these PU surface structures. Surface characteristics such as wettability and surface free energy were also analyzed since the interaction between biomaterials and blood occurs at their interface. The preliminary cytotoxicity screening showed no cytotoxicity of these PU membranes. The PU samples do not accelerate the clot formation mechanisms under the tested conditions. The results suggest that these PU membranes are promising materials for the preparation of cardiovascular scaffolds.

Collagen immobilization on ultraviolet light-treated poly(ethylene terephthalate):

The present article is focused on the studies regarding the effects of ultraviolet (UV) light on poly(ethylene terephthalate) (PET) films surfaces using scanning electron microscopy (SEM), Fourier transform infrared, X-ray photoelectron spectrometry (XPS), and atomic force microscopy (AFM) measurements, subsequent to collagen immobilization. UV treatment influences the surface energy of polymers as the result of the polymer chain breaking, followed by insertion of oxygen-containing functional groups. Accordingly, after UV light treatment, collagen was adsorbed on the PET surfaces in different proportions. Significant changes in the surface topography appeared after collagen immobilization on UV-treated PET films, and they were put in evidence by SEM and tapping-mode AFM experiments. XPS measurements demonstrated the adsorption of collagen on PET UV light-altered surfaces by increasing of nitrogen content. The cytocompatibility tests using stem cells have shown good results for all treated polymers.

Preparation approach effect on polyurethane/montmorillonite nanocomposites characteristics

Segmented polyurethane/montmorillonite (MMT) nanocomposites have been obtained by solvent casting or in situ polymerization approaches using poly(tetramethyleneglycol), α,ω-dihydroxylated poly(2-alkyl-2-oxazoline), 4,4′-methylenebis-(phenyl isocyanate) and MMT. The influence of the preparation method on the characteristics of the resulted materials was studied by means of spectral and thermal analysis, X-ray diffraction, scanning electronic microscopy, and dynamic-mechanical analysis.

Dielectric Characterization of Biopolymer/Poly(ϵ-Caprolactone) Hydrogels

The dielectric properties of a series of pure atelocollagen samples and of atelocollagen-based hydrogels long-range cross-linked with bifunctional poly(ϵ-caprolactone) derivative, or further short-range cross-linked by UV irradiation, were discussed in relation to the cross-linking method, composition, and hierarchical assembly. Three main factors with significant influence on the electrical behavior, frequency, temperature, and moisture content, are analyzed in detail.

Modification of Polyethylene Terephthalate

Nowadays, polymers find wide applications in modern industry, but finishing and bonding of almost all polymers present low hydrophilicity of their surfaces, which affects printability, wettability, biocompatibility, and adhesion. Therefore, polymer films need additional surface treatments to modify the surface properties, for better wettability and adhesion activities. There are different methods to modify the surface properties of the polymer films such as chemical or plasma treatments, ultraviolet (UV) or laser irradiation. Chemical surface modification may produce toxic compounds and physical alterations in the composition of the surface. From the polymer class, the polyesters have been frequently used to improve protein and cell adhesion.