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This work proposes an innovative strategy that combines two well-known easy and economical preparation techniques: powder metallurgy based space-holder (SH) technique to provide porous biocompatible Ti substrates with balanced biomechanical behavior (for cortical bone tissue substitution) promoting bone ingrowth and biocoating infiltration, and electropolymerization to coat these substrates with the polypyrrole–silver nanoparticles (PPy-AgNPs) composite conductive polymers improving its corrosion resistance, biocompatibility with enhanced antibacterial activity. The deposited PPy-based coatings present a cauliflower-like structure well adhered to the porous substrates. The macroporosity of and rough inner pore surface of Ti SH substrates are responsible for the superior adhesion of the conductive polymer comparing to typical denser substrates obtained by powder metallurgy or forging. The corrosion protection properties of the coatings were investigated by open circuit potential and Anodic Polarization in PBS media to simulate possible implant conditions, revealing improved corrosion resistance for the composite coatings. The bioactivity of the coatings was evaluated by immersion tests, revealing the formation of Hydroxyapatite after 90-day immersion in PBS. In both PPy and PPy-AgNPs composite coatings, a displacement of the polarization curves to more noble potentials and a decrease in the current density, indicated that the coating's protective character is maintained after 90-day immersion in PBS. The antibacterial activity was assessed by using the Kirby–Bauer disk-diffusion method against Staphylococcus aureus (ATCC 25923). The inhibition halo increased from 5.5 ± 0.4 mm for the bare substrate to 8.2 ± 0.6 mm for the PPy-coated substrate and to 12.5 ± 0.7 mm for the PPy-AgNPs-coated porous Ti. This feature associated to the improved corrosion protection and biocompatibility would significantly contribute to the success of the potential use of porous Ti implants

The use of nanomaterials as electrode modifiers permits the enhancement of electrode performance using a great variety of approaches, from electrocatalytic enhancement to the improvement of charge transfer processes. The control and understanding of the interaction between the modifiers and the electrode itself are of key importance for the final performance of the modified electrode. This becomes especially relevant in the case of nanostructured materials since their physical response is rarely trivial. In this work, we combined electrochemistry and atomic force microscopy (EC-AFM) to in-situ investigate the surface condition of electrodes modified with silver nanowires (AgNWs) during EC measurements for the first time. EC-AFM allows us to perform cyclic voltammetry and electrochemical impedance spectroscopy together with the assessment of the electrode surface directly in the electrolytic solution. On the other hand, the use of the Langmuir-Blodgett technique provides homogeneity and reproducibility to the electrode modification process. The electrochemical response of the modified electrodes has been found to strongly depend on the selected substrate, but also on the deposition procedure. This opens the path for a better understanding of electrode modification process, and also supports the viability of EC-AFM on open problems involving electrochemistry and surface science.

Porous titanium implants can be a good solution to solve the stress shielding phenomenon. However, the presence of pores compromises mechanical and corrosion resistance. In this work, porous titanium samples obtained using a space-holder technique are coated with Chitosan, Chi- tosan/AgNPs and Chitosan/Hydroxyapatite using only one step and an economic electrodeposition method. The coatings’ topography, homogeneity and chemical composition were analyzed. A study of the effect of the porosity and type of coating on corrosion resistance and cellular behavior was carried out. The electrochemical studies reveal that porous samples show high current densities and an unstable oxide film; therefore, there is a need for surface treatments to improve corrosion resistance. The Chitosan coatings provide a significant improvement in the corrosion resistance, but the Chitosan/AgNPs and Chitosan/HA coatings showed the highest protection efficiency, especially for the more porous samples. Furthermore, these coatings have better adherence than the chitosan coatings, and the higher surface roughness obtained favors cell adhesion and proliferation. Finally, a combination of coating and porous substrate material with the best biomechanical balance and biofunctional behavior is proposed as a potential candidate for the replacement of small, damaged bone tissues.