Increasing dielectric-loss of graphene oxide nanoparticle to enhance microwave thermoacoustic imaging contrast of breast tumor
Microwave-induced thermoacoustic imaging (MTAI) utilizes the high dielectric contrast of tissues in the microwave range, and, combined with the high resolution of ultrasound imaging, can noninvasively obtain anatomical and functional structure information. However, adequate contrast in certain indications (e.g., breast tumor in their early stages) can be difficult to achieve due to the minimal dielectricity difference in the target tissues. A tumor specific targeting nanoparticle with high-dielectric-loss would enhance the MTAI contrast in such applications. In this work, we propose a physics-principle based technique that increasing dielectric-loss of a nanoparticle by increasing its atomic defect to generate an amplified thermoacoustic signal. In principle, bovine serum albumin loaded on graphene oxide (GO) serves as a reductant to create additional vacancies in GO to produce more electric dipoles. Upon pulsed microwave irradiation, the defect dipoles are polarized repeatedly, causing transient heating and thermoelastic expansion that generates an amplified acoustic wave. The hypothesis was tested in vitro and in vivo with a breast tumor animal model. The results demonstrate that the nanoparticle can effectively enhance MTAI contrast of breast tumors. The physics-principle based technique is likely to contribute to early breast tumors imaging.