Biosustainable Hybrid Nanoplatforms as Photoacoustic Agents.

The development of biosafe theranostic nanoplatforms has attracted great attention due to their multifunctional behavior, reduced potential toxicity, and improved long-term safety. When considering photoacoustic contrast agents and photothermal conversion tools, melanin and constructs like melanin are highly appealing due to their ability to absorb optical energy and convert it into heat. Following a sustainable approach, in this study, silver-melanin like-silica nanoplatforms were synthesized exploiting different bio-available and inexpensive phenolic acids as potential melanogenic precursors and exploring their role in tuning the final systems architecture. The Ultraviolet-Visible Spectroscopy (UV-Vis) combined with X-Ray Diffraction (XRD) investigation proved metallic silver formation, while Transmission Electron Microscopy (TEM) analysis revealed that different morphologies can be obtained by properly selecting the phenolic precursors. By looking at the characterization results, a tentative formation mechanism is proposed to explain how phenolic precursors' redox behavior may affect the nanoplatforms' structure. The antibacterial activity experiments showed that all synthesized systems had a strong inhibitory effect on Escherichia coli, even at low concentrations. Furthermore, very sensitive Photoacoustic Imaging (PAI) capabilities and significant photothermal behavior under laser irradiation were exhibited. Finally, a marked influence of phenol nature on the final system architecture was revealed resulting in a significant effect on both biological and photoacoustic features of the obtained systems. These melanin-based hybrid systems exhibit excellent potential as triggerable nanoplatforms for various biomedical applications. This article is protected by copyright. All rights reserved.