Molecular local thermal studies for magnetic hyperthermia

Abstract

Magnetic nanoparticles when coupled to an alternating magnetic field are capable of energy absorption and then release it in form of heat. Thus, enabling the heating of the surroundings of the excited nanoparticles which can be used as a tool in many bioapplications. The determination of temperature increments around excited nanoparticles represent however an experimental challenge and existing reports tend to show simple and limited assessments. We demonstrate experimentally these temperature increments, when 12 nm magnetic nanoparticles are exposed to a radiofrequency radiation. Moreover, by functionalizing the surface of the nanoparticles with DNA molecules and further hybridizing with different length fluorophore-modified DNA an accurate temperature spatial mapping could be determined. Due to the design of these DNAs, different denaturalization temperatures (melting temperature, Tm) could be achieved. The quantification of the denaturalized fluorophore-modified DNA, and by interpolation onto a Boltzmann fitting model, it has been possible to calculate the local temperature increments at different distances, corresponding to the length of each modified DNA, from the surface of the nanoparticles. The local increments achieved were up to 15ºC, and the rigidity conferred by the double strand DNA allowed to evaluate the temperature at distances up to 5.6 nm from the nanoparticle surface. Same effect has been observed using thermosensitive polymers or for in vivo experimentation using Hydra Vulgaris as animal model.