title: Rationally encapsulated gold nanorods improving both linear and nonlinear photoacoustic imaging contrast in vivo.
abstract: Photoacoustic tomography has emerged as a promising non-invasive imaging technique that integrates the merits of high optical contrast with high ultrasound resolution in deep scattering medium. Unfortunately, the blood background in vivo seriously impedes the quality of imaging due to its comparable optical absorption with contrast agents, especially in conventional linear photoacoustic imaging modality. In this study, we demonstrated that two hybrids consisting of gold nanorods (Au NRs) and zinc tetra(4-pyridyl)porphyrin (ZnTPP) exhibited a synergetic effect in improving optical absorption, conversion efficiency from light to heat, and thermoelastic expansion, leading to a notable enhancement in both linear (four times greater) and nonlinear (more than six times) photoacoustic signals as compared with conventional Au NRs. Subsequently, we carefully investigated the interesting factors that may influence photoacoustic signal amplification, suggesting that the coating of ZnTPP on Au NRs could result in the reduction of gold interfacial thermal conductance with a solvent, so that the heat is more confined within the nanoparticle clusters for a significant enhancement of local temperature. Hence, both the linear and nonlinear photoacoustic signals are enhanced on account of better thermal confinement. The present work not only shows that ZnTPP coated Au NRs could serve as excellent photoacoustic nanoamplifiers, but also brings a perspective for photoacoustic image-guided therapy.
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798. yjzheng@ntu.edu.sg.
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.forename: Linyi
authors.initials: L
authors.lastname: Bai
authors.forename: Siyu
authors.initials: S
authors.lastname: Liu
authors.forename: Ruochong
authors.initials: R
authors.lastname: Zhang
authors.forename: Jingtao
authors.initials: J
authors.lastname: Zhang
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Feng
authors.forename: Yuanjin
authors.initials: Y
authors.lastname: Zheng
authors.forename: Yanli
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000818:Animals; D003287:Contrast Media; D006046:Gold; D006367:HeLa Cells; D006801:Humans; D043942:Nanotubes; D061088:Photoacoustic Techniques; D051381:Rats; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D003287:Contrast Media; D006046:Gold