Enhanced Performance of a Molecular Photoacoustic Imaging Agent by Encapsulation in Mesoporous Silicon Nanoparticles

Jinyoung Kang; Dokyoung Kim; Junxin Wang; Yunho Han; Jonathan M Zuidema; Ali Hariri; Ji-Ho Park; Jesse V Jokerst; Michael J Sailor

doi:10.1002/adma.201800512

Enhanced Performance of a Molecular Photoacoustic Imaging Agent by Encapsulation in Mesoporous Silicon Nanoparticles

Adv Mater. 2018 Jul;30(27):e1800512. doi: 10.1002/adma.201800512. Epub 2018 May 21.

Authors

Jinyoung Kang¹, Dokyoung Kim², Junxin Wang¹, Yunho Han³, Jonathan M Zuidema⁴, Ali Hariri¹, Ji-Ho Park³, Jesse V Jokerst⁵, Michael J Sailor⁶

Affiliations

¹ Department of Nanoengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
² Department of Anatomy and Neurobiology, College of Medicine, Center for Converging Humanities, Kyung Hee University, 26 Kyungheedae-Ro, Dongdaemun-Gu, Seoul, 02447, Republic of Korea.
³ Department of Bio and Brain Engineering & KAIST Institute for Health Science and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea.
⁴ Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
⁵ Department of Nanoengineering, Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
⁶ Department of Chemistry and Biochemistry, Department of Nanoengineering, Department of Bioengineering, Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, 92093, USA.

Abstract

Photoacoustic (PA) imaging allows visualization of the physiology and pathology of tissues with good spatial resolution and relatively deep tissue penetration. The method converts near-infrared (NIR) laser excitation into thermal expansion, generating pressure transients that are detected with an acoustic transducer. Here, we find that the response of the PA contrast agent indocyanine green (ICG) can be enhanced 17-fold when it is sealed within a rigid nanoparticle. ICG encapsulated in particles composed of porous silicon (pSiNP), porous silica, or calcium silicate all show greater PA contrast relative to equivalent quantities of free ICG, with the pSiNPs showing the strongest enhancement. A liposomal formulation of ICG performs similar to free ICG, suggesting that a rigid host nanostructure is necessary to enhance ICG performance. The improved response of the nanoparticle formulations is attributed to the low thermal conductivity of the porous inorganic hosts and their ability to protect the ICG payload from photolytic and/or thermal degradation. The translational potential of ICG-loaded pSiNPs as photoacoustic probes is demonstrated via imaging of a whole mouse brain.

Keywords: brain imaging; contrast agents; in vivo imaging; indocyanine green; ultrasound.

Abstract

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