Nanoparticle heating: nanoscale to bulk effects of electromagnetically heated iron oxide and gold for biomedical applications

Biomedical applications of nanoparticle heating range in scale from molecular activation (i.e. molecular beacons, protein denaturation, lipid melting and drug release), cellular heating (i.e. nanophotolysis and membrane permeability control and rupture) to whole tumor heating (deep and superficial). This work will present a review on the heating of two classes of biologically compatible metallic nanoparticles: iron oxide and gold with particular focus on spatial and temporal scales of the heating event. The size range of nanoparticles under discussion will focus predominantly in the 10 - 200 nm diameter size range. Mechanisms of heating range from Neelian and Brownian relaxation due to magnetic susceptibility at 100s of kHz, optical absorption due to VIS and NIR lasers and "Joule" heating at higher frequency RF (13.56 MHz). The heat generation of individual nanoparticles and the thermal responses at nano-, micro-, and macro-scales are presented. This review will also discuss how to estimate a specific absorption rate (SAR, W/g) based on individual nanoparticles heating in bulk samples. Experimental setups are designed to measure the SAR and the results are compared with theoretical predictions.