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Biomedical subjects

A Borzacchiello

Publications and source records attributed to A Borzacchiello.

10 recordsLinked to original sources
PubMed2005

Evaluation of injection augmentation treatment of hyaluronic acid based materials on rabbit vocal folds viscoelasticity.

The viscoelastic properties of vocal folds after injection of hyaluronic acid (hyaluronan, HA) based materials have been studied in an animal model (rabbit) six months after injection. The results indicate that the viscoelastic properties of the vocal folds injected with the HA based materials are similar to the healthy vocal folds (non-injected samples) used as control. Histological analysis has been also performed to investigate on the fate of the injected materials after six months from the implant. The HA based materials remain up to six months and they recruited fibroblasts that induce the ingrowth of new connective tissue resulting in an endogenous soft tissue augmentation. The HA based compounds are good candidate for further studies aimed at restoring/preserving the vibratory capacity of the vocal folds with injection treatment in glottal insufficiency.

Animals↗
PubMed2004

Hyaluronic-acid-based semi-interpenetrating materials.

In order to enhance the mechanical performances of hyaluronic acid (HA) without compromising its biological activity, HA has been interpenetrating with a fibrillar collagen scaffold. The semi-interpenetrating materials were obtained by mixing HA with different molecular weight and a pepsin-solubilized collagen (atelocollagen) solution, and then by inducing collagen fibrillogenesis. Results indicate that molecular weight of HA significantly influences the mechanical properties of the semi-interpenetrating materials and more specifically stronger material results from the use of low-molecular-weight (LMW) HA. According to the dynamic mechanical data the composite collagen-LMW HA has a higher elastic modulus than collagen, whereas the opposite is true for the high-molecular-weight (HMW) HA. This result highlights the role of specific interactions that occur between collagen and HA during the gel formation in controlling the network mechanical stability. LMW HA may, probably, interact more strongly with collagen during the fibrillogenesis process than HMW HA due to the higher mobility of the chains and the weaker homologous interactions. Moreover, morphological observations showed that LMW HA is intimately interdispersed within the collagen network and completely coated the fibrils, which act as mechanical support.

Biocompatible Materials↗
PubMed2002

Hyaluronic acid hydrogel in the treatment of osteoarthritis.

In order to overcome the problem of rapid clearance of the polysaccharide hyaluronic acid (Hyal) in the treatment of osteoarthritis (OA), a 50% cross-linked Hyal hydrogel (Hyal 50%) was synthesised. The 50% refers to the amount of COOH groups of the polysaccharide involved in the cross-linking reaction. i.e. 50% of the total amount. The rheological behaviour of the Hyal 50% hydrogel, and in particular the possibility to inject it through a needle, was studied. The results obtained demonstrated that the hydrogel injected through the needle still behaved like a gel, although it showed a reduction of the dynamic moduli. The most appropriate sterilisation technique for this kind of hydrogel was also evaluated. Liophilised Hyal 50% samples were sterilised by steam, Ethylene Oxide (EtO) and gamma-rays. EtO and gamma-rays did not modify the characteristics of the hydrogel in terms of swellability and morphology. Lastly, the in vivo effect of Hyal 50% hydrogel in the treatment of chondral defect in rabbit knee was also studied. The results obtained showed the Hyal 50% injections improved chondrocytes density and matrix appearance. Furthermore, the permanence in situ of the hydrogel was longer than that of the linear Hyal.

3T3 Cells↗
PubMed2002

Spatial and structural dependence of mechanical properties of porcine intervertebral disc.

Structure-function relationship of natural tissues is crucial to design a device mimicking the structures present in human body. For this purpose, to provide guidelines to design an intervertebral disc (IVD) substitute, in this study the influence of the spatial location and structural components on the mechanical properties of porcine IVD was investigated. Local compressive stiffness (LCS) was measured on the overall disc, also constrained between the two adjacent vertebrae: the dependence on the lumbar position was evaluated. The compliance values in the anterior position (A) were higher than both in the central posterior (CP) and in the lateral-posterior (RP, LP) locations. The values of Young's Modulus (74.67+/-6.03 MPa) and compression break load (1.36x10(4)+/-0.09x10(4)N) of the disc were also evaluated by distributed compression test. The NP rheological behavior was typical of weak-gels, with elastic modulus G' always higher than viscous modulus G" all over the frequency range investigated (G' and G" respectively equal to 320 and 85 Pa at 1 Hz) and with the moduli trends were almost parallel to each other.

Journal Article↗
PubMed2001

Network formation of low molecular weight hyaluronic acid derivatives.

The oscillatory and steady shear rheological properties of the benzyl esters of hyaluronic acid (HA), partially esterified (Hyaff 11p50), at low molecular weight (150 kDa) were evaluated and compared to the properties of HA at the same molecular weight. At concentrations up to 40 mg cm(-3) both Hyaff 11p50 solutions and HA solutions, behaved as viscous fluids. At higher concentrations, HA ester solutions exhibited an elastic response typical of weak gels, whereas HA exhibited a viscous behaviour. A solid-like response was also observed by lowering the temperature. These results indicate that hyaluronic acid ester solutions can form a weak gel network. The rheological properties of HA derivatives changed significantly compared to HA solutions. The improved elasticity and residence times of these solutions expand the possible applications of hyaluronic acid in the biomedical field.

Dose-Response Relationship, Drug↗
PubMed2000

Synthesis, chemical and rheological characterization of new hyaluronic acid-based hydrogels.

New hyaluronic acid-based hydrogels have been synthesized. The carboxylate groups of hyaluronan were activated in order to bind the amino terminal groups of the di-amine cross-linking reagent. Different hydrogels were obtained according to the different di-amine cross-linking agents (1,3-diaminepropane, 1.6-diaminohexane, PEG500 di-amine. and PEG800 di-amine). The cross-linked polymer (C.L.Hyal) was then sulphated (C.L.HyalS) by a heterogeneous reaction using sulphur trioxide pyridine complex (SO3-Py). The thermo-mechanical properties and swelling degree were evaluated and are discussed in relation to the chemical structure and the hydrophilic character of the gels. The different behaviours of C.L.Hyal and C.L.HyalS indicate the important role of sulphated groups.

Biocompatible Materials↗
PubMed1998

Isothermal and non-isothermal polymerization of a new bone cement.

A new bone cement based on poly(ethylmethacrylate) (PEMA), hydroxyapatite powder (HA) and n-butylmethacrylate monomer (n-BMA) has been studied using isothermal and non-isothermal polymerization. Methacrylate monomers are highly reactive and release a considerable amount of heat during polymerization. A quantitative understanding of the methacrylate polymerization is necessary because the thermal history of the polymerization has considerable influence on the final properties of a bone cement. In the first part, polymerization kinetics are analysed by means of differential scanning calorimetry (DSC). DSC data are used to evaluate a phenomenological model describing the cure kinetics of this new bone cement. In the second part, a kinetic model coupled with the energy balance is used to obtain temperature and degree of conversion profiles in the bone-cement-prosthesis system, under non-isothermal conditions, as function of initial temperature and thickness of the cement. Material properties, boundary and initial conditions and the kinetic behaviour are the input data for the numerically solved heat-transfer model. The temperature at the bone/cement interface, can be considered as a weak point, often responsible for total joint replacement failure. For this particular bone cement exhibiting a low exotherm and low glass transition temperature, the interfacial temperature is lower than the threshold level for thermal tissue damage (50 degrees C). The conversion occurs almost completely, avoiding problems with unreacted monomers that can be released by the cement, giving rise to tissue damage.

Journal Article↗
PubMed1998

Comparison between the polymerization behavior of a new bone cement and a commercial one: modeling and in vitro analysis.

The polymerization behavior of a new bone cement based on poly(ethylmethacrylate), hydroxyapatite powder and n-butylmethacrylate monomer and a commercial cement have been studied. Polymerization kinetics were analyzed by means of differential scanning calorimetry (DSC). DSC data have been used to evaluate a phenomenological model describing the cure kinetics of this new bone cement. The kinetic model coupled with the energy balance was then used to obtain temperature and degree of conversion profiles in the bone-cement-prosthesis system, under non-isothermal conditions, as function of initial temperature and thickness of the cement. Material properties, boundary and initial conditions and the kinetic behavior were the input data for the numerically solved heat-transfer model. The modeling results have been compared with in vitro results.

Journal Article↗
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.

Journal Article↗