Biomedical subjects

Youssef Haikel

Publications and source records attributed to Youssef Haikel.

4 recordsLinked to original sources

PubMed2006

Layer-by-layer self-assembled polyelectrolyte multilayers with embedded liposomes: immobilized submicronic reactors for mineralization.

The development of chemical reactions in nanospaces is of paramount importance for the development of active nanodevices, particularly in nanofluidics. It has been shown in a previous paper that phospholipid vesicles can be incorporated without spontaneous bilayer rupture into poly-L-glutamic acid/poly(allylamine) (PGA/PAH) multilayered polyelectrolyte films. The aim of the present study was to use such a system as an "embedded submicronic reactor" able to trigger precipitation of calcium phosphates within closed spaces through an enzymatic reaction, the enzyme also being encapsulated in the vesicle interior. To this aim, large unilamellar vesicles (LUVs) were produced containing calcium ions as active ions in the mineralization process, spermine as an activator of crystal growth, and alkaline phosphatase as a catalyst to convert phosphate esters into phosphates. After stabilization by adding a layer of poly-(D-lysine), these vesicles were embedded in a (PGA-PAH)n film. A paranitrophenyl phosphate containing solution was then put in contact with this film. It is shown by means of infrared spectroscopy in the attenuated total reflection mode that, consecutively to this contact, calcium phosphates are growing inside the embedded vesicles. By using scanning near-field fluorescence microscopy, it is demonstrated that the alkaline phosphatase enzymes are most probably located inside the vesicles after their embedding. In addition, atomic force microscopy was used to show, after chemical removal of the organic top layer of the film, that the inorganic platelets produced after the precipitation reaction are localized in volumes of similar size and shape as that of the vesicles into which the phosphate ester hydrolysis and subsequent precipitation reaction did occur.

Journal Article↗

PubMed2005

Polyelectrolyte multilayers functionalized by a synthetic analogue of an anti-inflammatory peptide, alpha-MSH, for coating a tracheal prosthesis.

Polyelectrolyte multilayer films made of poly (L-lysine) (PLL) and poly (L-glutamic acid) (PGA) have been functionalized by covalent binding of a synthetic analogue of the anti-inflammatory peptide, alpha-melanocyte-stimulating hormone (alpha-MSH) to PGA to create biologically active coatings for tracheal prostheses. The morphology and in vivo stability of the films were investigated by atomic force microscopy and confocal laser scanning microscopy, respectively. For the in vivo evaluation, 87 rats were implanted and examined for a period superior to 3 months. Histological analysis, performed 1 month after implantation, showed a fibroblast colonization of the periprosthetic side and a respiratory epithelium type on the endoluminal side of the implant for all the polyelectrolyte coatings tested. However, for prostheses modified by PGA ending multilayer films, a more regular and less obstructive cell layer was observed on the endoluminal side compared to those modified by PLL ending films. Systemic anti-inflammatory IL-10 production was only detected in rats implanted with prostheses functionalized by alpha-MSH, demonstrating, in vivo, the anti-inflammatory activity of the embedded peptide into multilayer architectures.

Animals↗

PubMed2003

Insertional inactivation of pac and rmlB genes reduces the release of tumor necrosis factor alpha, interleukin-6, and interleukin-8 induced by Streptococcus mutans in monocytic, dental pulp, and periodontal ligament cells.

Streptococcus mutans possesses different cell wall molecules, such as protein of the I/II family, the serotype f polysaccharide rhamnose glucose polymer (RGP), and lipoteichoic acid (LTA), which act as adhesins and modulins, allowing S. mutans to colonize teeth and cause dental caries and pulpitis. We tested several isogenic mutants of S. mutans defective in protein I/II and/or RGP, as well as purified modulins such as protein I/II, RGP, and LTA, for their binding and activation abilities on monocytic, dental pulp (DP), and periodontal ligament (PDL) cells. Our results demonstrate that both protein I/II and RGP play important roles in streptococcal adherence to human monocytic and fibroblastic cells, whereas LTA is only a minor adhesin. In the activation process, the cytokine response elicited is polarized toward a Th1 response which seems principally due to protein I/II and RGP. Even if protein I/II seems to be more efficient in its purified form in triggering cells to release interleukin-8 (IL-8), RGP is the most efficient cytokine-stimulating component in intact bacteria, while LTA plays only a minor role. In cell activation, we showed, by using either cytochalasin D or coated ligands, that internalization of either S. mutans, S. mutans isogenic mutants, or purified ligands is not necessary to trigger cells to release IL-8. We also showed that, besides the implication of monocytes in pulpal inflammation, fibroblast-like cells such as DP and PDL cells are also actively implicated in local inflammation and in the generation of a Th1 response after stimulation with S. mutans cells or antigens.

Adhesins, Bacterial↗

PubMed2002

Viability, adhesion, and bone phenotype of osteoblast-like cells on polyelectrolyte multilayer films.

The aim of this study was to develop new biocompatible coatings for bone implants by the alternating deposition of oppositely charged polyelectrolytes. Polyelectrolyte films were built up with different terminating layers on which SaOS-2 osteoblast-like cells and human periodontal ligament (PDL) cells were grown. The terminating layer was made of one of the following polyelectrolytes: poly(ethylene imine) (PEI), poly(sodium 4-styrenesulfonate) (PSS), poly(allylamine hydrochloride) (PAH), poly(L-glutamic acid) (PGA), or poly(L-lysine) (PLL). Cell adherence, viability, stability of osteoblast phenotype, and inflammatory response were studied. Adherence and viability were good on all terminating layers except the PEI-terminating layer, which was cytotoxic. Maintenance of osteoblast phenotype marker expression was observed on PSS- and PGA-terminating films for both cell types, whereas downregulation, associated with the induction of Interleukin-8 (IL-8) secretion, was detected on PEI and PAH for both cell types and on PLL for PDL cells. These results suggested a good biocompatibility of PSS- and PGA-ending films for PDL cells and of PSS-, PGA-, and PLL-terminating films for SaOS-2 cells. As a result, polyelectrolyte multilayer films could emerge as new alternatives for implant coatings.

Alkaline Phosphatase↗