Biosustainable Hybrid Nanoplatforms as Photoacoustic Agents

The development of biosafe theranostic nanoplatforms has attracted greatattention due to their multifunctional behavior, reduced potential toxicity, andimproved long-term safety. When considering photoacoustic contrast agentsand photothermal conversion tools, melanin and constructs like melanin arehighly appealing due to their ability to absorb optical energy and convert itinto heat. Following a sustainable approach, in this study, silver-melaninlike-silica nanoplatforms are synthesized exploiting different bio-available andinexpensive phenolic acids as potential melanogenic precursors and exploringtheir role in tuning the final systems architecture. The UV–Vis combined withX-Ray Diffraction investigation proves metallic silver formation, whileTransmission Electron Microscopy analysis reveals that differentmorphologies can be obtained by properly selecting the phenolic precursors.By looking at the characterization results, a tentative formation mechanism isproposed to explain how phenolic precursors’ redox behavior may affect thenanoplatforms’ structure. The antibacterial activity experiments showed thatall synthesized systems have a strong inhibitory effect on Escherichia coli,even at low concentrations. Furthermore, very sensitive PhotoacousticImaging capabilities and significant photothermal behavior under laserirradiation are exhibited. Finally, a marked influence of phenol nature on thefinal system architecture is revealed resulting in a significant effect on bothbiological and photoacoustic features of the obtained systems. Thesemelanin-based hybrid systems exhibit excellent potential as triggerablenanoplatforms for various biomedical applications.