Novel antibacterial bioactive glass nanocomposite functionalized with tetracycline hydrochloride

To prevent the high frequency of wound infections, anti-bacterial agents can be loaded onto composites. In the present study, the antibiotic tetracycline hydrochloride (TC)was incorporated, for the first time, in collagen type I membranes coated with nano-sized SiO2-CaOP2O5 bioactive glass (n-BG) obtained by a sol-gel chemical route. Collagen membranes coated with n-BG were immersed in simulated body fluid (SBF) containing 0.25, 0.75 or 1.25 mg mL−1 of TC for 48 h at 37∘C following a coprecipitation method. The antibiotic was released in distilledwater at 37∘C for up to 72 h. The antibacterial activity of the composites was evaluated in vitro by the inhibition zone test and plate count method. Two different Staphylococcus aureus strains, S. aureus ATCC29213 and S. aureus ATCC25923, were exposed to the biomaterials. The results showed that the incorporation but not the release of TC was dependent on the initial concentration of TC in SBF. The biomaterials inhibited S. aureus growth, although the efficacy was similar for all the concentrations. The results allow us to conclude that the new composite could have potential in the prevention of wound infections.Fil: Rivadeneira, Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Luz, Gisela M.. Universidade Do Minho; PortugalFil: Audisio, Marcela Carina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones Para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones Para la Industria Química; ArgentinaFil: Mano, Joao F.. Universidade Do Minho; PortugalFil: Gorustovich Alonso, Alejandro Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentin

Secondary structure of rhBMP-2 in a protective biopolymeric carrier material

Efficient delivery of growth factors is one of the great challenges of tissue engineering. Polyelectrolyte multilayer films (PEM) made of biopolymers have recently emerged as an interesting carrier for delivering recombinant human bone morphogenetic protein 2 (rhBMP-2 noted here BMP-2) to cells in a matrix-bound manner. We recently showed that PEM made of poly(l-lysine) and hyaluronan (PLL/HA) can retain high and tunable quantities of BMP-2 and can deliver it to cells to induce their differentiation in osteoblasts. Here, we investigate quantitatively by Fourier transform infrared spectroscopy (FTIR) the secondary structure of BMP-2 in solution as well as trapped in a biopolymeric thin film. We reveal that the major structural elements of BMP-2 in solution are intramolecular β-sheets and unordered structures as well as α-helices. Furthermore, we studied the secondary structure of rhBMP-2 trapped in hydrated films and in dry films since drying is an important step for future applications of these bioactive films onto orthopedic biomaterials. We demonstrate that the structural elements were preserved when BMP-2 was trapped in the biopolymeric film in hydrated conditions and, to a lesser extent, in dry state. Importantly, its bioactivity was maintained after drying of the film. Our results appear highly promising for future applications of these films as coatings of biomedical materials, to deliver bioactive proteins while preserving their bioactivity upon storage in dry state.This work was supported by the French Ministry of Research through an ANR-EmergenceBIO grant (ANR-09-EBIO-012-01), by the European Commission (FP7 program) via a European Research Council starting grant (BIOMIM, GA 259370), and by GRAVIT (081012_FIBIOS). C.P. is grafetul to IUF for financial support

Mecanismos de relaxacao em polimeros liquidos cristalinos de cadeia lateral

The technique of thermally stimulated depolarization currents - TSDC was used in order to study the dipolar relaxation mechanisms present in a series of eleven side-chain liquid crystalline polymers with different chemical structures (Chapters 3, 4 and 5). One of these polymers was also studied by dielectric relaxation spectroscopy (Chapter 6).The basic concepts which underline both experimental techniques are presented in chapters 1 and 2. It was observed (Chapter 3) that one or two relaxations can be observed by TSDC in the liquid crystalline phase of these materials.These relaxations have been correlated with some motions of the dipolar moment components of the mesogenic moiety. Both activation enthalpy and entropy do not show a significant variation which lead us to conclude that the distribution of relaxation time must be narrow. The compensation phenomenon (linear relationship between activation enthalpy and entropy) is observed in the complex relaxation observed near Tg for all polymers and it has been proposed an hypotheses to explain this behaviour. For same polymers it has been possible to observed a relaxation in the low temperature region (Chapter 5). Two components of this peak were detected and attributed to specific local motions within the mesogenic groupsAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga

Effect of Polyelectrolyte Multilayers Assembled on Ordered Nanostructures on Adhesion of Human Fibroblasts

Nanosphere lithography (NSL) and the layer-by-layer (LbL) technique are combined here for the first time to design a flexible system to achieve nanotopographical control of cell adhesion. NSL is used-to generate regular patterns of tetrahedral gold nanodots of different size and distance. Besides the change in topography, LbL is used to generate a polyelectrolyte multilayer (PEM) system consisting of heparin (HEP) and poly(ethylene imine) (PEI) on top of the gold dots. The localized formation of PEM on gold dots is achieved by prior passivation of the surrounding silicon or glass surface. Properties of PEM are changed by adjusting the pH value of HEP solution to either acidic or alkaline values. Studies with human dermal fibroblasts (HDF) reveal that cells spread to a higher extent on PEM formed at pH 5.0 in dependence on the structure dimension. Further, filopodia formation is highly increased in cells on nanostructures exhibiting HEP as a terminal layer. The new system offers a great potential to guide stem cell differentiation in the future owing to its high degree of chemical and topographical heterogeneity

Development control and inactivation of Byssochlamys nivea ascospores by hyperbaric storage at room temperature

This study tested hyperbaric storage (25-150 MPa, for 30 days) at room-temperature (HS/RT, 18-23 °C) in order to control the development of Byssochlamys nivea ascospores in apple juice. In order to mimic commercially pasteurized juice contaminated with ascospores, thermal pasteurization (70 and 80 °C for 30 s) and nonthermal high pressure pasteurization (600 MPa for 3 min at 17 °C, HPP) took place, and the juice was afterwards placed under HS/RT conditions. Control samples were also placed in atmospheric pressure (AP) conditions at RT and were refrigerated (4 °C). The results showed that HS/RT, in samples without a pasteurization step and those pasteurized at 70 °C/30 s, was able to inhibit ascospore development, contrarily to samples at AP/RT and refrigeration. HS/RT for samples pasteurized at 80 °C/30 s evidenced ascospore inactivation, especially at 150 MPa, wherein an overall reduction of at least 4.73 log units of ascospores was observed to below detection limits (1.00 Log CFU/mL); meanwhile, for HPP samples, especially at 75 and 150 MPa, an overall reduction of 3 log units (to below quantification limits, 2.00 Log CFU/mL) was observed. Phase-contrast microscopy revealed that the ascospores do not complete the germination process under HS/RT, hence avoiding hyphae formation, which is important for food safety since mycotoxin development occurs only after hyphae formation. These findings suggest that HS/RT is a safe food preservation methodology, as it prevents ascospore development and inactivates them following commercial-like thermal or nonthermal HPP pasteurization, preventing mycotoxin production and enhancing ascospore inactivation

Designing multigradient biomaterials for skin regeneration

Skin defects are amongst the main causes of morbidity and mortality worldwide, which account for significantly high socioeconomic costs. Today, much attention is being paid to tissue engineering and biomaterials strategies for skin regeneration, and among them, there is increasing interest in using multigradient biomaterials. Gradient-based approaches are an emerging trend in tissue engineering for the homogeneous delivery of therapeutic agents by using biomaterials. Several studies have acknowledged that wound repair mechanisms could be enhanced through biomimicking physicochemical properties of different skin layers. In addition, in different layers of skin tissue, cells experience various physicochemical gradients, which potentially regulate their behaviors. Therefore, interface tissue engineering and biomaterials approaches are gaining increasing attention for skin regeneration through the incorporation of physicochemical gradients within the engineered constructs. This review first presents a necessary overview of the biological properties of skin tissue and its changes during repair in different tissue injuries. Fundamental issues and necessities of using different types of gradient scaffolds and interface tissue engineering strategies for skin regeneration are addressed. The focus of this review is on describing current progress in designing gradient scaffolds for controlling and directing cellular and molecular responses in skin tissue. The main used fabrication approaches, including both traditional and advanced methods for designing multigradient scaffolds, are also discussed

Chitosan beads as templates for layer-by-layer assembly and their application in the sustained release of bioactive agents

Uncoated chitosan beads and chitosan beads coated with hyaluronic acid/chitosan (HA/Ch) multilayers, were used to investigate the controlled release of gentamicin sulphate (GS). Greater encapsulation efficiency was observed for the layer—by-layer multilayer coated beads. The in vitro drug release was in a slower sustained manner compared with noncoated chitosan beads. The differences in in vitro drug release results may be explained by the barrier effect of the coating that impedes diffusion of GS and supporting complementary water uptake. These findings indicated that a slower sustained release of gentamicin can be obtained using multilayer coatings of HA/Ch on chitosan beads and that this process could be used as a drug delivery system. In addition, agglomerates of these bead could provide a porous support in tissue engineering applications

Recent Developments in Chitosan-Based Micro/Nanofibers for Sustainable Food Packaging, Smart Textiles, Cosmeceuticals, and Biomedical Applications

Chitosan has many useful intrinsic properties (e.g., non-toxicity, antibacterial properties, and biodegradability) and can be processed into high-surface-area nanofiber constructs for a broad range of sustainable research and commercial applications. These nanofibers can be further functionalized with bioactive agents. In the food industry, for example, edible films can be formed from chitosan-based composite fibers filled with nanoparticles, exhibiting excellent antioxidant and antimicrobial properties for a variety of products. Processing ‘pure’ chitosan into nanofibers can be challenging due to its cationic nature and high crystallinity; therefore, chitosan is often modified or blended with other materials to improve its processability and tailor its performance to specific needs. Chitosan can be blended with a variety of natural and synthetic polymers and processed into fibers while maintaining many of its intrinsic properties that are important for textile, cosmeceutical, and biomedical applications. The abundance of amine groups in the chemical structure of chitosan allows for facile modification (e.g., into soluble derivatives) and the binding of negatively charged domains. In particular, high-surface-area chitosan nanofibers are effective in binding negatively charged biomolecules. Recent developments of chitosan-based nanofibers with biological activities for various applications in biomedical, food packaging, and textiles are discussed herein