Cytotoxicity of polyethyleneimine (PEI), precursor base layer of polyelectrolyte multilayer films.

Polyethyleneimine (PEI) is a synthetic polymer commonly used as precursor base layer in polyelectrolyte multilayer films. However, the biological properties of this cationic macromolecule are poorly understood. The aim of this experimental investigation was to evaluate in vitro the biocompatibility of PEI towards two different human cell lines. The experimental investigation was undertaken on pure titanium (Ti) and nickel-titanium (NiTi) alloy samples with an average surface roughness of Ra=0.3microm. A biological study was undertaken at day 0 (2h after seeding), day 2, day 4 and day 7 to observe the cellular response of fibroblasts and osteoblasts cell lines in terms of morphology, adhesion (as observed by scanning electron microscopy), and viability (Mosmann's test). The results showed that PEI can be successfully deposited onto Ti or NiTi alloy, but generates a detrimental cellular response on both substrates as illustrated by a decrease of both fibroblast and osteoblast adhesion and proliferation over a 7-day culture period. These results suggest that PEI is potentially cytotoxic and may not be biocompatible enough in clinical applications using high molecular weight. As a consequence, polyelectrolyte multilayer films, which are promising in prosthesis and implantology fields, could not be coated with PEI at a high molecular weight. A lower molecular weight should be considered or a more biocompatible molecular base as precursor layer of polyelectrolyte multilayer films would be better to use for a good human bio-integration.

Tensile and shear bond strength evaluation of a total-etch three-step and two self-etching one-step dentin bonding systems.

PURPOSE: The aim of this study was to compare the bond strengths of two new self-etching one-step (Prompt L-Pop 2 and Adper Prompt L-pop) to a total-etch three-step dentin bonding system (Scotchbond Multipurpose Plus). MATERIALS AND METHODS: One hundred twenty human molars were randomly divided into 3 groups of 40 specimens each. Dentin surfaces of each group were bonded with either Scotchbond Multipurpose Plus (SMP), a three-step system, Prompt L-Pop 2 (PLP), or Adper Prompt L-Pop (APLP), two one-step bonding systems--according to manufacturers' recommendations. After adhesive application, a composite resin cylinder was incrementally built in a Teflon mold (5 mm high and 5 mm in diameter). The samples of each group were randomly divided into 2 subgroups of 20 samples each and were tested in a shear bond or in a tensile bond strength mode (crosshead speed 5 mm/min). Statistical analyses were performed with one-way ANOVA and Student's t-test. RESULTS: The significantly lowest shear and tensile bond strength values were obtained with APLP. PLP revealed higher shear bond strengths than APLP and SMP. There were no differences in tensile bond strengths between PLP and SMP (p < 0.05). CONCLUSION: The results of this in vitro study showed that the chemical modifications (adjunction of monomers and copolymers) of the self-etching all-in-one system APLP did not improve its mechanical properties.

Corrosion resistance and biocompatibility of a new porous surface for titanium implants.

Alterations of the commercially pure titanium (cpTi) surface may be undertaken to improve its biological properties. The aim of this study was to investigate the biocompatibility of cpTi when submitted to a new, porous titanium, surface treatment (porous Ti). Five types of surface treatments, namely sintered microspheres porous titanium (porous Ti), titanium plasma spray (TPS), hydroxyapatite (HA), sandblasted and acid etched (SBAE), and resorbable blast medium, sandblasted with hydroxyapatite (RBM) were made. In the experimental methods, the corrosion potentials were measured over time, and then a linear sweep voltammetric analysis measured the polarization resistances and corrosion currents. For biocompatibility evaluation, MG63 osteoblast-like cells were used. Cell morphology, cell proliferation, total protein content, and alkaline phosphatase (ALP) activity were evaluated after 2 h, and after 2, 4 and 7 d. Porous Ti and SBAE showed a better corrosion resistance, with a weak corrosion current and a high polarization resistance, than the other surfaces. Cell attachment, cell morphology, cell proliferation, and ALP synthesis were influenced by the surface treatments, with a significant increase observed of the activity of osteoblast cells on the porous coating (porous Ti). Based on these results, it is suggested that the porous Ti surface has a significantly better biocompatibility than the other surface treatments and an excellent electrochemical performance.