Morpho-Structural Investigations of Biomaterials for Biocidal Activity

A new wound dressing made of gelatin and Ag, was evaluated for the management of tissue reconstitution in rats. The gelatin–based dressing, with metabolic stimulation properties that favored the recovery of the skin was made of stiff sheets to supply the repairingtissue with mechanical support. The gelatin sheets enhanced the development of collagen fibers and subsequently cell proliferation at the level of stromal and vascular elements. A protocol based on the utilization of natural biomaterials in the presence of low concentrations of a biocidal was proposed which could control microbiocidal activities principally in burned and debilitated patients.

HA/alginate hybrid composites prepared through bio-inspired nucleation

Poorly crystalline apatite has been directly nucleated on self-assembling alginate chains by neutralization synthesis to obtain a biomimetic artificial bone-like composite. It has been observed that in preparing HA/alginate composites, Ca2+ ions present on the apatitic surface cross-link the alginate chains to produce a material with different morphology and thermal stability, both functions of the HA/alginate weight ratio. In vitro tests were performed on different samples in terms of both the HA/alginate ratio and synthesis temperature. All the samples were cultured for seven days with MG63 osteoblast-like cells and then underwent morphological and biochemical analyses (MTT and ALP tests). Scaffolds showed a different solubility into the culture media, which was related to the temperature of synthesis and to the HA/alginate ratio. All our data confirm the ability of the tested materials to favour cell growth and to maintain their osteoblastic functionality, at least during the examined period.

Exploring the damage limitation possibilities of mineral fibres for future integrated solutions: an in vitro study

Owing to their possible carcinogenic effect, asbestos and other silica derivatives have been identified as priority substances for risk reduction and prevention of pollution. Neutralisation procedures have thus become a topical research subject in many European and American countries. In the present study, silica derivatives (asbestos-containing and asbestos substitutes like slag wool, rock wool, cement asbestos) were fully impregnated with an epoxy resin according to the procedure used for the in situ impregnation with viscous polymeric media, which penetrate and cement the fibres in place and reduce the risk of their dispersion in air. Untreated and treated samples were used to investigate their in vitro interaction with a human continuous epithelial cell line (NCTC 2544 keratinocytes) and test the resin's efficiency in passivating the surface activity of the fibrous particulate. SEM and morpho-quantitative data evidenced that impregnation with the epoxy resin modifies the mineral fibres' bioactivity (reduction of cell adhesion and decreased spread/round cell ratio) and demonstrated the value of in vitro cell testing after passivation as a risk-assessment procedure. These tests could be used for the rapid determination of the level of passivation of new synthetic mineral fibrous materials subjected to resin impregnation.

Fungistatic activity of modified chitosans against Saprolegnia parasitica

Five chemically modified chitosans were tested for their antifungal activities against Saprolegnia parasitica by the radial growth assay in chitosan-bearing agar, and the fungal growth assay in chitosan-bearing broth. Results indicated that methylpyrrolidinone chitosan, N-carboxymethyl chitosan and N-phosphonomethyl chitosan exerted effective fungistatic action against S. parasitica: in fact the radial growth was nil for 50 h at 20 degrees C, and the fungus was precipitated when the Bacto YM broth contained one of these chitosans. Electron microscopy observations (TEM and SEM) provided evidence of ultrastructural alterations, damaged fungal structures, uptake of modified chitosans, and hyphal distortion and retraction.

Fabricated hyalS micropatterns and surface guidance of NCTC 2544 continuous cell line: an in vitro study

Surface topography is important in establishing tissue organisation adjacent to implants, smooth surfaces generally being associated with fibrous encapsulation. By virtue of its large hydrated molecular volume and its capacity to form molecular matrix, hyaluronic acid can expand the interfibrillar collagen spaces to allow the movement of cells, although it can also hamper their locomotion. Low molecular-weight hyaluronan can also stimulate cell proliferation, especially at low concentrations. The aim of the present work was to evaluate in vitro the growth and migratory behaviour of NCTC 2544 keratinocytes cultured on different materials microstructured with hyaluronic acid or sulfated hyaluronic acid to assess the possibility of using these devices in the repair process of soft tissues. Ultrastructural morphological analyses, morphometric evaluations and detection of cytoskeletal elements were performed. Our observations provide evidence that micrometer-size parallel grooves of hyaluronic acid can influence cell growth behaviour since cells seeded onto the microstructured substrate arranged themselves according to a shape and an orientation that clearly reflected the chemotropism exerted on them by the two forms of acid. These data also highlight the importance of accurate microtexture fabrication. We intend to follow up these in vitro studies with in vivo experimental applications using PET and gelatin substrates structured with HyalS to evaluate wound healing responses, and to extend our investigations of the cytoskeletal modifications induced by different microstructures.

[Bio-metabolic changes produced by 2 commercial fluoride-containing compounds on human keratinocytes]

BACKGROUND

Although fluoride has been used for decades either systemically or topically to prevent dental caries, the cellular and molecular mechanisms underlying its action are poorly understood.

METHODS

An in vitro study of the human keratinocyte cell line NCTC 2544 was conducted in the presence of two different fluoride-containing commercial compounds (Zymafluor and Elmex) to investigate their toxicity threshold and the sequence of events involved in fluoride ion toxicity in this cell population. The toxicity threshold was determined by incubating cells with rising concentrations of Zymafluor and Elmex for 20 h. The study of the sequence of events involved in ion toxicity was performed through a time-effect study by exposing cells to 4 mM fluoride ions and testing them at 2, 6, and 20 h. Cell viability and ultrastructural parameters were assessed: degree of confluence, semiquantitative assessment of dead cells and debris in the supernatant, and morphology.

RESULTS

Ultrastructural morphological analysis showed different cell behaviours with the two compounds; moreover, their toxic effect appeared to be both concentration- and time-dependent.

CONCLUSIONS

These data underline the susceptibility of the intracellular communication system to fluoride and show that exceeding the therapeutic dose of fluoride involves substantial risk of toxicity.