Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (λ=248nm, τFWHM=25ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay. The obtained thin films were XRD amorphous and exhibited a morphology characteristic to the laser deposited structures composed of nanometric round shaped grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan. The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of chitosan-rich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less chitosan. The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite.

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Two ZnO materials of spherical hierarchical morphologies, with hollow (ZnOHS) and solid cores (ZnOSS), were obtained through the hydrolysis of zinc acetylacetonate in 1,4-butanediol. The nature of the defects and surface reactivity for the two ZnO materials were investigated through photoluminescence, X-ray photoelectron spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy proving the coexistence of shallow and deep defects and, also, the presence of polyol byproducts adsorbed on the outer layers of the ZnO samples. The EPR spectroscopy coupled with the spin-trapping technique showed that the surface of the ZnO samples generates reactive oxygen species (ROS) like hydroxyl (•OH) and singlet oxygen (1O2) as well as carbon-centered radicals. The ZnO materials exhibited a wide spectrum of antimicrobial activity, being active against Gram-positive, Gram-negative, and fungi strains, both in planktonic and, more importantly, adherent growth states. The decrease of antimicrobial efficiency in the presence of a ROS scavenger (mannitol) and the decrease of the cell viability with the ROS level suggest that one of the mechanisms that governs both the antimicrobial and cytotoxic activities on human liver cells is ROS-mediated. However, at active antimicrobial concentrations, the biocompatibility of the tested materials is very good.

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