RESUMEN
BACKGROUND: Cohesion is described as the force between particles of the same substance that acts to unite them. Contrary to rheology, there are currently no ready-made instruments designed to measure cohesion, or methods which could be easily adapted to gels. To study and compare the possible clinical effects from the cohesive properties of a gel, it is necessary to standardize the definition and measurement of cohesion. OBJECTIVE: The purpose of this study was to develop and evaluate methods for measuring cohesion. METHODS AND MATERIALS: Three different methods were evaluated and compared with measures of perceived cohesion; compression force, dispersion in water and drop weight. Two different families of fillers (Emervel and Restylane) were used for evaluating the different methods. RESULTS: The compression force did not reflect the measures of perceived cohesion. The dispersion method showed variable results over time, had some practical issues, and is evaluated by subjective assessment. The best correlation to the perceived cohesion was found with the drop weight method. CONCLUSION: The drop weight method which closely resembles the definition of cohesion (IUPAC) was considered to be the best method for measuring cohesion.
Asunto(s)
Ácido Hialurónico/análogos & derivados , Ensayo de Materiales/métodos , Reología/métodos , Humanos , Ácido Hialurónico/químicaRESUMEN
OBJECTIVE: The aim of the present study was to investigate the intra-articular duration of Durolane™ in a rabbit model to allow comparison between Durolane™ residence time and data reported for other hyaluronic acid products as well as native hyaluronic acid. DESIGN: (14)C-labeled Durolane™ was manufactured by labeling the cross-linker used for stabilization. A single injection of approximately 0.3 mL (14)C-labeled Durolane™ was administered intra-articularly in both knee joints of male New Zealand White rabbits. At days 1, 2, 3, 7, 28, 60, 96, and 120 after injection, the knee joints of 4 animals were collected, and the radioactivity of the remaining gel was measured. The obtained data were fitted by exponential models to calculate the half-life of the gel. Two additional rabbits were used for histology of the joint 127 days after the injection. RESULTS: The elimination of (14)C-labeled Durolane™ followed first-order kinetics with an apparent half-life of approximately 32 days. Histology showed no morphological changes in the knee joints. CONCLUSIONS: This study shows that Durolane™ has a half-life of 32 days in the rabbit knee joint, which is much longer compared to literature data on hyaluronic acid and other modified hyaluronic acid products.
RESUMEN
In the present study, a phage display library covering the genome of Staphylococcus lugdunensis, was affinity-selected against von Willebrand factor (vWf). This led to the identification of a gene, vwbl, encoding a putative cell surface protein of 2060 amino acids, denoted vWbl. The deduced protein has an overall organisation typical of staphylococcal cell surface proteins, with an N-terminal signal peptide, and a C-terminal cell wall sorting signal. The vWf-binding part is located in repetitive domains and antibodies against vWbl or vWf can inhibit the binding. Southern blot analysis showed that vwbl was present in the 12 S. lugdunensis strains tested.