Nanotheranostics 2022; 6(1):79-90. doi:10.7150/ntno.63634

Research Paper

Ultrasmall gold nanorod-polydopamine hybrids for enhanced photoacoustic imaging and photothermal therapy in second near-infrared window

Wonjun Yim1, Raina M. Borum2, Jiajing Zhou2, Yash Mantri3, Zhuohong Wu2, Jingcheng Zhou2, Zhicheng Jin2, Matthew Creyer2, Jesse V. Jokerst1,2,4,✉

1. Materials Science and Engineering Program, University of California San Diego, La Jolla, California, 92093, United States.
2. Department of Nanoengineering, University of California San Diego, La Jolla, California, 92093, United States.
3. Department of Bioengineering, University of California San Diego, La Jolla, California, 92093, United States.
4. Department of Radiology, University of California San Diego, La Jolla, California, 92093, United States.

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Citation:
Yim W, Borum RM, Zhou J, Mantri Y, Wu Z, Zhou J, Jin Z, Creyer M, Jokerst JV. Ultrasmall gold nanorod-polydopamine hybrids for enhanced photoacoustic imaging and photothermal therapy in second near-infrared window. Nanotheranostics 2022; 6(1):79-90. doi:10.7150/ntno.63634. Available from https://www.ntno.org/v06p0079.htm

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Abstract

Gold nanorods (GNRs) have attracted great interest for photo-mediated biomedicines due to their tunable and high optical absorption, high photothermal conversion efficiency and facile surface modifiability. GNRs that have efficient absorption in second near-infrared (NIR-II) window hold further promise in bio-applications due to low background signal from tissue and deep tissue penetration. However, bare GNRs readily undergo shape deformation (termed as 'melting effect') during the laser illumination losing their unique localized surface plasmon resonance (LSPR) properties, which subsequently leads to PA signal attenuation and decreased photothermal efficiency. Polydopamine (PDA) is a robust synthetic melanin that has broad absorption and high photothermal conversion. Herein, we coated GNRs with PDA to prepare photothermally robust GNR@PDA hybrids for enhanced photo-mediated theranostic agents. Ultrasmall GNRs (SGNRs) and conventional large GNRs (LGNRs) that possess similar LSPR characteristics as well as GNR@PDA hybrids were compared side-by-side in terms of the size-dependent photoacoustic (PA) imaging, photothermal therapy (PTT), and structural stability. In vitro experiments further demonstrated that SGNR@PDA showed 95% ablation of SKOV3 ovarian cancer cells, which is significantly higher than that of LGNRs (66%) and SGNRs (74%). Collectively, our PDA coating strategy represents a rational design for enhanced PA imaging and efficient PTT via a nanoparticle, i.e., nanotheranostics.

Keywords: miniature gold nanorod, core-shell structure, synthetic melanin, second near-infrared