Biomedical subjects

Pierre Schaaf

Publications and source records attributed to Pierre Schaaf.

39 records · Page 3Linked to original sources

PubMed2002

Polyelectrolyte multilayer films modulate cytoskeletal organization in chondrosarcoma cells.

The aim of this study was to evaluate polyelectrolyte multilayer films as interfaces for implants. Polyelectrolyte multilayers were built up with different terminating layers by alternate deposition of oppositely charged polyelectrolytes on which chondrosarcoma (HCS-2/8) cells were grown in the presence of serum. Films formed by an increasing number of layers were investigated. The terminating layer was made of one of the following polyelectrolytes: poly-sodium-4-styrenesulfonate (PSS), poly-L-glutamic acid (PGA), poly-allylamine hydrochloride (PAH), or poly(L-lysine) (PLL). Cell viability, inflammatory response, adherence, and cytoskeletal organization were studied. Induction of interleukin-8 (IL-8) secretion was detected on PAH and PLL ending polyelectrolyte films. Early cellular adherence was enhanced with PGA, PAH, PLL, and, to a lower extent, PSS terminating layers. Adherence was independent of the number of layers constituting the films. The presence of actin filaments and vinculin focal adhesion spots was observed on PSS or PAH ending films. They were respectively partially and totally absent on PGA and PLL terminating multilayer architectures. For PLL ending films, vinculin and actin organization was clearly dependent on the number of deposited layers. The results of this study suggest that PSS ending multilayered films constitute a good interfacial micro-environment at the material surface for HCS-2/8 cells.

Actins↗

PubMedDate not supplied

Improvement of stability and cell adhesion properties of polyelectrolyte multilayer films by chemical cross-linking.

Poly(L-lysine)/hyaluronan (PLL/HA) films were chemically cross-linked with a water soluble carbodiimide (EDC) in combination with a N-hydroxysulfo-succinimide (NHS) to induce amide formation. Fourier transform infrared spectroscopy confirms the conversion of carboxylate and ammonium groups into amide bonds. Quartz crystal microbalance-dissipation reveals that the cross linking reaction is accompanied by a change in the viscoelastic properties of the films leading to more rigid films. After the cross-linking reaction, both positively and negatively ending films exhibit a negative zeta potential. It is shown by fluorescence recovery after photobleaching measured by confocal laser scanning microscopy that cross-linking dramatically reduces the diffusion of the PLL chains in the network. Cross linking also renders the films highly resistant to hyaluronidase, an enzyme that naturally degrades hyaluronan. Finally, the adhesion of chondrosarcoma cells on the films terminating either with PLL or HA is also investigated. Whereas the non cross-linked films are highly resistant to cell adhesion, the cells adhere and spread well on the cross-linked films.

Cell Adhesion↗

PubMedDate not supplied

Degradability of polysaccharides multilayer films in the oral environment: an in vitro and in vivo study.

Biomedical devices and modified biomaterial surfaces constitute an expanding research domain in the dental field. However, such oral applications have to face a very particular environment containing specific physiological conditions and specific enzymes. To evaluate their suitability in the development of novel oral applications, the degradability of polyelectrolyte multilayer films made of the natural polysaccharides chitosan and hyaluronan (CHI/HA) was investigated in vitro and in vivo in a rat mouth model. The films were either native or cross-linked using a water-soluble carbodiimide (EDC) in combination with N-hydroxysulfosuccinimide. The in vitro degradation of the films by different enzymes present in the oral environment, such as lysozyme and amylase, was followed by quartz crystal microbalance measurements and confocal laser scanning microscopy observations after being film labeled with CHI(FITC). Whereas native films were subjected to degradation by all the enzymes, cross-linked films were more resistant to enzymatic degradation. Films were also put in contact with whole saliva, which induced a slow degradation of the native films over an 18 h period. The in vivo degradation of the films deposited on polymer disks and sutured in the rat mouth was followed over a 3 day period. Whereas film degradation is fast for native films, it is much slower for the cross-linked ones. More than 60% of these films remained on the disks after 3 days in the mouth. Taken together, these results suggest that the multilayer films made of natural polysaccharides are of high potential interest for oral applications, especially as drug release systems, offering various degradation rates and consequent release characteristics.

Animals↗