Device-associated infections (DAI) remain a serious concern in modern healthcare. Bacterial attachment to a surface is the first step in biofilm formation, which is one of the main causes of DAIs. The development of materials capable of preventing or inhibiting bacterial attachment constitutes a promising approach to deal with this problem. The multifactorial nature of biofilm maturation and antibiotic resistance directs the research for multitargeted or combinatorial therapeutic approaches. One attractive strategy is the modification or the engineering of surfaces in order to provide antiadhesive and/or antimicrobial properties. Currently, several different approaches that involve physical and chemical surface modification deliver some possible alternatives to achieve this goal. The engineered surfaces can be coated with molecules capable of inhibiting the bacterial adhesion or with active agents that kill microorganisms. In addition, surfaces can also be modified in order to be stimuli-responsive, responding to a particular trigger and then delivering the consequent antimicrobial outcome. Here, we review the prevailing strategies to modify surfaces in order to create an antimicrobial surface and discuss how different surface functionalization can affect bacterial adhesion and/or viability.

The increasing incidence of infections in implantable devices has encouraged the search for biocompatible antimicrobial surfaces. To inhibit the bacterial adhesion and proliferation on biomaterials, several surface functionalization strategies have been developed. However, most of these strategies lead to bacteriostatic effect and only few of these are able to reach the bactericidal condition. In this work, bactericidal surfaces were designed through the functionalization of titanium surfaces with poly-l-lysine (PLL) as the mediator for the incorporation of antimicrobial silver nanoparticles (AgNPs). This functionalization influences the adsorption of the particles on the substrate impeding the agglomeration observed when bare titanium surfaces are used, leading to a homogeneous distribution of AgNPs on the surfaces. The antimicrobial activity of this surface has been tested against two different strains, namely, Staphylococcus aureus and Pseudomonas aeruginosa. For both strains and different AgNPs sizes, the surface modified with PLL and AgNPs shows a much enhanced antimicrobial activity in comparison with AgNPs deposited on bare titanium. This enhanced antibacterial activity is high enough to reach bactericidal effect, a condition hard to achieve in antimicrobial surfaces. Importantly, the designed surfaces are able to decrease the bacterial viability more than 5 orders with respect to the initial bacterial inoculum. That means that a relative low load of AgNPs on the PLL-modified titanium surfaces reaches 99.999% bacterial death after 24 h. The results of the present study are important to avoid infections in indwelling materials by reinforcing the preventive antibiotic therapy usually dosed throughout the surgical procedure and during the postoperative period.

With the intention of taking care of the environment and human health, the development of alternative eco-friendly methods to inhibit metal corrosion is intensively encouraged. In previous works we showed that some phytocompounds components of essential oils such as carvacrol (Carv) and thymol (TOH) are able to be electropolymerized on metals and they seem to be promissory for this purpose. The aim this paper is to investigate if the biocompatibility of copper covered by coatings formed by electropolymerization of Carv and TOH (polyCarv and polyTOH) is related with the potential selected for the electropolymerization process. Potentiostatic perturbations at different potentials, AFM images, ATR-FTIR spectroscopy and measurements of copper ions release provided suitable information to make a detailed analysis of different stages of the electropolymerization process that leads to polyCarv and polyTOH layers on copper surface. The change of the characteristics of the coatings over time was evaluated after several polymerization periods and current transients were interpreted by using nucleation and growth models. Results showed interesting changes in the polymerization process with the electrochemical perturbation, nature of the isomer, and time of the treatment. The treatment that provides the most protective, transparent and homogeneous layer, that strongly increased the biocompatibility of Cu could be selected: electropolymerization of Carv at 0.4V. Results highlight the importance of the detailed study of the evolution of the electropolymerization processes to select the best ecofriendly condition due the high impact of potential perturbation and polarization time on the biocompatibility of the resulting polymeric layer-copper system.