Editorial Special issue on nano-systems for antimicrobial therapy

Editorial of the Special issue on Nano-Systems for Antimicrobial Therap

Nanocomposite sprayed films with photo-thermal properties for remote bacteria eradication

Currently there is a strong demand for novel protective materials with effcient antibacterial properties. Nanocomposite materials loaded with photo-thermally active nanoparticles can offer promising opportunities due to the local increase of temperature upon near-infrared (NIR) light exposure capable of eradicating bacteria. In this work, we fabricated antibacterial films obtained by spraying on glass slides aqueous solutions of polymers, containing highly photo-thermally active gold nanostars (GNS) or Prussian Blue (PB) nanoparticles. Under NIR light irradiation with low intensities (0.35W/cm2) these films demonstrated a pronounced photo-thermal effect: 06Tmax up to 26.4 ffC for the GNS-containing films and 06Tmax up to 45.8 ffC for the PB-containing films. In the latter case, such a local temperature increase demonstrated a remarkable effect on a Gram-negative strain (P. aeruginosa) killing (84% of dead bacteria), and a promising effect on a Gram-positive strain (S. aureus) eradication (69% of dead bacteria). The fabricated films are promising prototypes for further development of lightweight surfaces with effcient antibacterial action that can be remotely activated on demand

Self-assembled monolayers of copper sulfide nanoparticles on glass as antibacterial coatings

We developed an easy and reproducible synthetic method to graft a monolayer of copper sulfide nanoparticles (CuS NP) on glass and exploited their particular antibacterial features. Samples were fully characterized showing a good stability, a neat photo-thermal effect when irradiated in the Near InfraRed (NIR) region (in the so called \u201cbiological window\u201d), and the ability to release controlled quantities of copper in water. The desired antibacterial activity is thus based on two different mechanisms: (i) slow and sustained copper release from CuS NP-glass samples, (ii) local temperature increase caused by a photo-thermal effect under NIR laser irradiation of CuS NP\u2013glass samples. This behavior allows promising in vivo applications to be foreseen, ensuring a \u201cstatic\u201d antibacterial protection tailored to fight bacterial adhesion in the critical timescale of possible infection and biofilm formation. This can be reinforced, when needed, by a photo-thermal action switchable on demand by an NIR light

Modular approach for bimodal antibacterial surfaces combining photo-switchable activity and sustained biocidal release

Photo-responsive antibacterial surfaces combining both on-demand photo-switchable activity and sustained biocidal release were prepared using sequential chemical grafting of nano-objects with different geometries and functions. The multi-layered coating developed incorporates a monolayer of near-infrared active silica-coated gold nanostars (GNS) decorated by silver nanoparticles (AgNP). This modular approach also enables us to unravel static and photo-activated contributions to the overall antibacterial performance of the surfaces, demonstrating a remarkable synergy between these two mechanisms. Complementary microbiological and imaging evaluations on both planktonic and surface-attached bacteria provided new insights on these distinct but cooperative effects

Enhanced kinetic inertness in the electrochemical interconvertion of Cu(I) double helical – Cu(II) monomeric complexes

Three new ligands made of two iminoquinoline halves separated by an (R,R)-trans-1,2-cyclohexenediyl spacer have been synthesized. These ligands feature –OR functions appended in the 8-positions of the quinoline rings (R = n-alkyl). The ligands display a behaviour similar to that of their analogues that contain unsubstituted quinolines, forming a bistable system with copper. [Cu2L2]2+ helicates are obtained with Cu+ and [CuL]2+ monomers with Cu2+, as shown by UV/Vis titrations, determination of complex formation constants, mass and NMR measurements, and X-ray crystallographic analysis. The OR groups are found to be noncoordinating, but the presence of such substituents on the quinoline rings slows the electrochemical interconversion of [Cu2L2]2+ into [CuL]2+. In particular, oxidation of [Cu2L2]2+ gives a reversible two-step profile in cyclic voltammetry experiments, due to the formation of the Cu2+ helicate [Cu2L2]4+, that does not evolve into [CuL]2+in the CV experiment time scal

Coordination chemistry of surface-grafted ligands for antibacterial materials

Antibacterial metal complex monolayers covalently grafted on bulk surfaces are reviewed, focusing on the experimental values found for metal:ligand surface stoichiometry, on the surface concentration of the complexes, on time-regulated cation release and on the relation with the observed antibacterial properties. Stability, geometry and coordination features of the surface-grafted complexes are discussed where available, and compared with the classical ligand/metal behavior found in solution. In the applicable cases, comparison is made also with surfaces bearing monolayers of silver nanoparticles as antibacterial agents, evidencing the advantages of the coordination complex monolayers in obtaining fast release, efficient antibacterial action and null or negligible risks as regards toxicity