Viorica Trandafir

Doxycycline Delivery From Collagen Matrices Crosslinked With Tannic Acid

Collagen-doxycycline matrices crosslinked with a natural polyphenol – tannic acid for the treatment of infected wounds were obtained by the freeze-drying of the corresponding gels. FT-IR spectra show that the triple helical structure of collagen is preserved in all the matrices, doxycycline produce collagen crosslinking and the degree of crosslinking increases with tannic acid concentration. Digestion of matrices using collagenase confirms the crosslinking effect of doxycycline and tannic acid and the increasing of the crosslinking degree with the amount of acid. The release of doxycycline from the matrices crosslinked with tannic acid is slower than that from the uncrossliked one and decreases with increasing of acid concentration, according to FT-IR and digestion results, and follows the power law model, with a release exponent of about 0.4, which indicates an anomalous transport. The matrices containing doxycycline, tannic acid and their combination do not develop gram-positive (Staphylococcus aureus) or gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria, fungi or leavens.

The effect of the hydration degree on the hydrothermal and thermo-oxidative stability of some collageneous matrices

The methods of the thermal analysis (TG, DTG and DTA) were used in order to investigate the effect of the hydration degree on the thermal behaviour of some collageneous matrices. It was pointed out that the degradation of hydrated collagen in the temperature range 20-400°C occurs through two successive processes accompanied by mass losses. The first process, consisting in the collagen dehydration, is endothermic and takes place in the temperature range ≈25 - ≈125°C. The second process is exothermic and consists in the decomposition and/or thermo-oxidation of dry collagen. The thermal parameters of both processes depend on the hydration degree of collagen. The observed dependencies show that the hydrothermal and thermo-oxidative stability of collagen are strongly correlated with its water content.

In Vitro Biocompatibility of Human Endothelial Cells with Collagen-Doxycycline Matrices

The aim of this study was to test the biocompatibility between collagen-doxycycline matrices with various porosities and human endothelial cells. Collagen matrices were prepared by freeze-drying process. The crosslinking degree of collagen matrices was evaluated by FT-IR spectroscopy, the matrices morphology by SEM microscopy. The biocompatibility of collagen matrices with endothelial cells was monitored byfluorescence and transmission electron microscopy. We found that the three-dimensional structures of matrix with 1.2% collagen, 0.2% doxycycline crosslinked with 0.25% glutaraldehyde was optimal in terms of biodegradability, morphology and endothelial cells biocompatibility indicating the use of these scaffolds in tissueengineering.

Titania Modified Layered Silicate for Polymer/Inorganic Nanocomposites

Sodium montmorillonite, from purified Romanian bentonite, and quasiamorphous TiO2 aerogel were used for obtaining binary hybrids by solution intercalation method. In the nanohybrid, TiO2 results in crystalline-anatase form. The morphostructural properties of the TiO2 modified layered silicate were studied by X-Ray Diffraction, FTIR Spectroscopy, High Resolution Transmission Electron Microscopy and Thermogravimetric Analysis. By uniform dispersing of binary nanohybrid in a collagen matrix, nanocomposite with intercalated lamellar structure was obtained. The basal spacing (d001) increases from 14.8 A˚ in the binary hybrid to 18 Å in the nanocomposite with collagen. Applications in regenerative medicine of hard tissue are foreseen.

Ternary Bio-Nanostructured Systems Prepared under High Pressure Conditions

Many researchers have assumed that a combination of hydroxyl apatite (HAP) and collagen (COL) may be the best solution for bone replacement and have prepared their composites by several techniques [1]. However, such HAP/COL composite had no nanostructure similar to bone, and consequently indicated no bone-like mechanical properties. These results demonstrate that the chemical composition similar to bone only is insufficient for bone metabolism and mechanical properties. Mechanical and biological performance of this type of materials could be improved by adding TiO2 within the initial mixture of nanostructured composites [2]. Ternary nanostructured systems consisting of hydroxyl apatite, TiO2 aerogel and collagen were prepared for the first time by hydrothermal procedure in high pressure conditions. Among many advantages, the synthesis method proposed in this paper could lead to formation of chemically bonded compounds as a consequence of high pressure conditions. The resulted material could find applications in bone tissue regenerative medicine, either in powder form for bone defects treatment, or in matrix form as osteoconductive coating for metal implants. Further studies are necessary to evaluate the osteoconductive properties.

New Scaffold Structure Based on Collagen. Fabrication and Biocompatibility Evaluation

Development of bioactive material template for in vitro and in vivo synthesis of osteoinductive and biodegradable bone material was intensevely studied over the last decade and the research in the field of partial substitution of bone tissue, use a very large range of natural and synthetic polymers, inorganic components and their composites. Despite of composites collagen hydroxiapatite with a mimetic osseous composition until now was not defined a scaffold model suitable to biofunctionality of native osseous structure. The goal of the article is fabrication of a new scaffold structure, based on collagen fibrils with length 1–1.5 cm, thikness 0.1–0.3 and having a shroud structure. Collagen crosslinking was performed with aldehides in such way that aminic groups became bloked and carboxylic groups remain free in order to involve hydroxiapatite and biocompatible synthetic polymer (polyvinil alchol, polilactide) coupling. Crosslinking temperature for collagen fibrils is 70°C being a suitable temperature for resistance to “in vivo” resorbtion. Infrared spectra was performed and the amount of the hidroxyl bonds was correlated with hydrophilic [2] balance estimated from contact angle measurements. The morphology and the surface composition were determined with an Environmental Scanning Electron Microscope FEI/Phillips XL30 ESEM and all physical chemical properties especially surface features were used as basic factors in future cell growth and proliferation process. The main aim of biocompatibility tests is to multiply and to differentiate cells in vitro in osteoblasts from marrow. The environment of culture was supplemented with specific media containing Na β glicerofosfat and the cell was differentiated in osteoblasts. As arguments for differentiation were proposed the evidence of specific markers: osteonectine, sialoproteines and osteocalcine. Osteoprogenitors cells culture were tested on various samples of scaffold. Cell cultures were tested for alkaline phosphatase at a week after culture. The technique uses p-nitrophenole which is going to be change by alkaline phosphatase in dinitro-phenole.

Collagen - Modified Layered Silicate Biomaterials for Regenerative Medicine of Bone Tissue

Zina Vuluga1, Catalina-Gabriela Potarniche2, Madalina Georgiana Albu3, Viorica Trandafir4, Dana Iordachescu5 and Eugeniu Vasile5 1National Research and Development Institute for Chemistry and Petrochemistry-ICECHIM, Bucharest 2Department of Mechanical and Manufacturing Engineering Aalborg University, Aalborg, 3National Research and Development Institute for Textile and Leather, Bucharest, 4University of Bucharest, Research Center for Biochemistry and Molecular Biology, Bucharest, 5METAV CD, Bucharest, 1,3,4,5Romania 2Denmark