Collaborative Research: Engineering spatiotemporal temperature control of solvated noble-metal nanoparticles through the understanding of solid-water nanoscale conduction

The use of light-activated gold nanoparticles for thermal ablation of cancerous tissue and localized thermally-activated drug and gene delivery systems has been extensively investigated. However, these therapeutic approaches have stalled at the preclinical stage because the nanoparticle temperature cannot be controlled precisely, which leads to effects on tissue away from the therapeutic target. The conversion of light to heat inside the nanoparticles is efficient and fast, which means the key parameter determining overall therapeutic efficiency is the thermal energy dissipation across the interface between the gold nanoparticles and the surrounding medium, i.e., biological fluid. Therefore, the main goal of this project is to broaden our understanding of heat transfer across solid-liquid interfaces, which is a highly complex problem that involves surface chemistry, interfacial liquid properties, and energy carrier physics. The broader activities of this project will include the creation of a podcast for societal outreach, and several educational activities, including a course on the research tools used by the investigators. The goal of this project is to engineer a methodology for the spatiotemporal temperature control of solvated gold nanoparticles by focusing on the interfacial dissipation of thermal energy. The research plan is driven by the hypothesis that interfacial liquid properties and structuring determine the solid-liquid interfacial thermal conductance, which is the missing link between existing theory and experiments. This project will address this knowledge gap through a combination of unique experimental and computational efforts including: (i) spectroscopy techniques for probing the interfacial liquid properties; (ii) interface-sensitive laser pump-probe metrology for accurate thermal boundary conductance measurements; (iii) reactive force field development for capturing thermally-sensitive chemistry; and (iv) multiscale (atomistic and continuum) modeling of heat transfer in solvated nanoparticle systems. Thiolated gold surfaces and nanoparticles will be considered for thermotherapy and drug delivery systems based on Diels-Alder chemistry. Primary objectives are the creation of a comprehensive computational tool, based on the reactive force field (ReaxFF) able to capture thermally-sensitive chemistry and interfacial liquid properties as measured by spectroscopy; experimentally observing for the first time the computationally predicted relationship between adsorbed liquid ordering and solid-liquid conductance; and using these findings to create continuum models capable of incorporating the granularity of atomistic scale parameters and laser irradiation to formulate temperature control strategies. The successful execution of this project will bring significant advances in the fields of heat transfer, biomedical engineering, surface science, and potential cancer therapeutics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.