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Biomedical subjects

L Ambrosio

Publications and source records attributed to L Ambrosio.

80 records · Page 5Linked to original sources
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Cellulose derivative-hyaluronic acid-based microporous hydrogels cross-linked through divinyl sulfone (DVS) to modulate equilibrium sorption capacity and network stability.

The aim of this work is to obtain a chemically cross-linked hydrogel from hyaluronic acid and cellulose derivatives that exhibits sensitivity to variation of the composition of the external absorbing medium and an equilibrium sorption capacity higher than a common hyaluronic acid-based hydrogel, in view of its potential use in prevention of postsurgical soft tissue adhesion. This has been achieved by chemical stabilization of hyaluronic acid (HA) and cellulose derivatives, hydroxyethylcellulose (HEC) and carboxymethylcellulose (CMCNa) through the difunctional cross-linker divinyl sulfone. Significant increase in sorption capacity, both in water and in water solutions at different ionic strength, has been observed for these samples in comparison with hydrogels obtained through chemical stabilization of hyaluronic acid. Moreover, different dehydration procedures adopted for the xerogel synthesis have been used, which resulted in a modulation of the equilibrium sorption capacity. Hyaluronic acid stability has been confirmed by means of NMR analysis.

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Macroporous hydroxyapatite as alloplastic material for dental applications.

In the dentistry field, synthetic hydroxyapatite can be conveniently used as semiabsorbable alloplastic material to solve a number of clinical problems. The hydroxyapatite structure influences bone ingrowth as well as its resorption. In particular, pore size must exceed 100 microm to allow new bone ingrowth. Because of its brittleness, highly porous hydroxyapatite is difficult to handle without causing damage, and, therefore, its mechanical performance has to be improved placing the material on a dense hydroxyapatite substrate. Dense/porous hydroxyapatite laminates can be obtained by slip casting technology. The method starts with the preparation of a ceramic powder-binder-solvent system. This slurry produces, after solvent evaporation, a soft green tape, that is successively baked at 300 degrees C to remove all organic component, and finally sintered at high temperature (1200 degrees C). The material porosity cannot be significantly modified by changes in the slurry composition and sintering temperature; therefore, the macroporous hydroxyapatite layer must be obtained using a porous hydroxyapatite powder. The powder is prepared by grinding of green tape pieces and the resulting coarse material is successively baked at 300 degrees C. Such material is mixed with a polymer solution and cast on a green tape substrate. Layer fractures are not observed in both film bulks and interface, because during sintering the consolidation of two layers happens simultaneously. In the resulting material, the first layer consisted of macroporous hydroxyapatite with high osteoconductive properties, and the second layer was a dense hydroxyapatite substrate able to improve the laminate mechanical properties.

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Modulation of in vitro myogenesis induced by different polymer substrates.

The understanding of substrate dependence of cellular differentiation is important in the surface design of biocompatible artificial devices as well as cell-incorporated tissue engineered devices. In an attempt to understand some of the genetic and epigenetic aspects of the control of cell differentiation in the presence of two different materials, Chronoflex (CH) and plasma treated Chronoflex coated with Hyaluronan (CH-HA), we used primary cultures of human myogenic cells, a model that encompasses cell proliferation, migration, fusion, and differentiation dependent gene activation. By testing both the material samples on the growth of human myoblasts in primary cultures, we demonstrated that both CH and CH-HA substrates were able to support the cell growth since they did not affect cell count and DNA synthesis. On the contrary, the degree of myoblast differentiation, assessed as a function of creatine phosphokinase (CPK) activity on living cells, was completely different on the two biomaterials. Indeed, the amount of CPK increased on CH-HA cultured cells as a result of myotube formation, while CH grown myoblasts remained unfused and displayed no increase on the CPK activity even after 12 days culture. Moreover, the expression level of MyoD and myogenin mRNA, both related to myogenic cell differentiation, appeared extremely low in CH-grown cells, while they were rapidly induced in CH-HA cultured myoblasts.

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PubMedDate not supplied

Chitosan-based hydrogels: synthesis and characterization.

Chitosan (CHI) is a polysaccharide of beta-1,4-linked 2-amino-2-deoxy-D-glucopyranose derived by N-deacetylation of chitin in aqueous alkaline medium. The shells of crustaceans such as crabs, shrimp, and lobster are the current source of chitosan. It is known to be non-toxic, odourless, biocompatible in animal tissues and enzymatically biodegradable. For these reasons much research interest has been paid to its biomedical, ecological, and industrial applications over the past decade. However, its rigid crystalline structure, poor solubility in organic solvents and poor processability have limited its use. To broadening its range of applications, a growth research effort has been devoted to explore ways of modifying Chitosan. Here it has been reported on the synthesis of new hydrogels, obtained by self-curing chitosan with acrylic acid (AA) and methyl acrylate (MA). The hydrogels were characterized by FTIR, swelling and rheological analysis. The results of this study showed that the swelling and mechanical properties of chitosan are highly improved by the presence of poly acrylate. The swelling degree of these materials does not depend upon the ratio MA/AA. It is possible to improve and modulate the mechanical properties of the hydrogels by changing the relative MA/AA ratio.

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