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Nowadays, thanks to nanotechnological progress, which itself guides us more and more closely toward not only the efficient design of innovative nanomaterials or nanostructures, but to the improvement of their functionality, we benefit from an important asset in the battle against pathogenic illnesses. Herein, we report a versatile biocompatible plasmonic nanoplatform based on a Whatman paper incorporating positively-charged gold nanospherical particles via the immersion approach. The morphological characterization of the as-engineered-plasmonic paper was examined by SEM (scanning electron microscopy) and HRTEM (high-resolution transmission electron microscopy) investigations, while its surface chemical modification with a synthetic polypeptide, specifically RRWHRWWRR-NH2 (P2), was proved by monitoring the plasmonic response of loaded gold nanospheres and the emission signal of P2 via fluorescence spectroscopy. The as-functionalized plasmonic paper is non-cytotoxic towards BJ fibroblast human cells at bactericidal concentrations. Finally, the antimicrobial activity of the P2-functionalized plasmonic paper on both planktonic bacteria and biofilms was tested against two reference strains: Gram-positive Bacteria, i.e., Staphylococcus aureus and the Gram-negative Bacteria, i.e., Escherichia coli, determining microbial inhibition of up to 100% for planktonic bacteria. In line with the above presented nanoplatform&rsquo, s proper design, followed by their functionalization with active antimicrobial peptides, new roads can be open for determining antibiotic-free treatments against different relevant pathogens.

A great amount of effort is directed towards the progress of cancer treatment approaches aspiring to develop non-invasive, targeted and highly efficient therapies. In this context, Photothermal (PTT) and Photodynamic (PDT) Therapies were proven as promising. This work aims to integrate the therapeutic activities of two near-infrared (NIR) photoactive biomaterials - gold nano-bipyramids (AuBPs) and Indocyanine Green (ICG) - into one single targeted hybrid nanosystem able to operate as dual PTT-PDT agent with higher efficiency compared with each one alone. Firstly, different aspect ratio' AuBPs were systematically investigated in water solution for their intrinsic ability to efficiently generate toxic reactive oxygen species, namely oxygen singlet (1O2), under NIR laser irradiation, as this effect is less investigated in literature. Interestingly, the photodynamic activity of AuBPs measured by monitoring the photooxidation of 9,10-Anthracenediyl-bis(methylene)dimalonic acid (ABDA) - a well-known 1O2 sensor, is important, counting for 30 % decrease in ABDA optical absorbance for the most active AuBPs, well-correlating with the previously determined photothermal conversion efficiency. Furthermore, ICG was successfully grafted onto the Poly-lactic acid (PLA) coating of plasmonic nanoparticles and, consequently, the as-designed fully integrated hybrid nanosystem shows improved PTT-PDT performance in solution. Specifically, by triggering simultaneous PTT-PDT activities, the 1O2 amount is doubled, while the heating monitoring shows higher and faster increase in temperature compared to AuBPs alone. Finally, the efficiency of the combined PTT-PDT therapeutic activity was validated in vitro against B16-F10 cell line by covalent conjugation of the nanosystem with Folic Acid, which ensures the cellular recognition by overexpression of folate receptor.

In the current paper, we report an efficient approach to produce in a controllable manner electromagnetic hot-spots localized in linear assemblies of gold nanorods (AuNRs) that can be further exploited as highly active surface-enhanced Raman scattering (SERS) sites. The process of the AuNRs self-assembling was initiated in an aqueous solution at pH = 3.1 in the presence of L-cysteine (Cys) molecules and was monitored in real-time for minutes up to hours. The recorded sequential extinction spectra featuring a well-defined isosbestic point at 834 nm is consistent with the first-order like reaction between individual and end-to-end assembled AuNRs as final products. Moreover, the dynamic of the self-assembling process was examined by correlating the extinction spectra with the average number of AuNRs in the chains as provided from the transmission electron microscopy (TEM) pictures. Noteworthy, the average number of connected AuNRs can be fixed at any moment in solution, depending of the desired plasmonic response, by blocking the assembling process with a negative layer of poly (sodium-p-styrenesulfonate) (PSS) polyelectrolyte. The high electric field in the hot-spots in between the linked nanoparticles was proved by SERS experiments using as target analyte para-aminothiophenol (p-ATP) and conducted to clear the demonstration of a higher enhancement factor relative to the individual AuNRs. Finally, all experimental findings and, especially, the far and near-field optical properties of such fabricated plasmonic nanoassemblies were supported by finite-difference time-domain (FDTD) simulations.