Miniature Hollow Gold Nanorods with Enhanced Effect for In Vivo Photoacoustic Imaging in the NIR‐II Window

Abstract

The miniaturization of gold nanorods exhibits a bright prospect for intravital photoacoustic imaging (PAI) and the hollow structure possesses a better plasmonic property. Herein, miniature hollow gold nanorods (M‐AuHNRs) (≈46 nm in length) possessing strong plasmonic absorbance in the second near‐infrared (NIR‐II) window (1000–1350 nm) are developed, which are considered as the most suitable range for the intravital PAI. The as‐prepared M‐AuHNRs exhibit 3.5 times stronger photoacoustic signal intensity than the large hollow Au nanorods (≈105 nm in length) at 0.2 optical density under 1064 nm laser irradiation. The in vivo biodistribution measurement shows that the accumulation in tumor of miniature nanorods is twofold as high as that of the large counterpart. After modifying with a tumor‐targeting molecule and fluorochrome, in living tumor‐bearing mice, the M‐AuHNRs group gives a high fluorescence intensity in tumors, which is 3.6‐fold that of the large ones with the same functionalization. Moreover, in the intravital PAI of living tumor‐bearing mice, the M‐AuHNRs generate longer‐lasting and stronger photoacoustic signal than the large counterpart in the NIR‐II window. Overall, this study presents the fabrication of M‐AuHNRs as a promising contrast agent for intravital PAI.

Seed-Mediated Synthesis of Gold Nanorods at Low Concentrations of CTAB

“…Gold nanorods (AuNRs) have attracted many researchers in the recent two decades because of their special characteristics and wide applications, including chemical and biological sensing, 1 − 3 surface-enhanced Raman scattering (SERS), 4 − 6 anticancer therapy, 7 − 9 and imaging. 10 − 12 Optically, the interaction of free electrons with light at different wavelengths leads to the localized surface plasmon resonance (LSPR) effect. 13 , 14 It can be characterized by the scattering and absorption peaks corresponding to various wavelength ranges in the spectrum.…”

A Unique Multifunctional Nanoenzyme Tailored for Triggering Tumor Microenvironment Activated NIR‐II Photoacoustic Imaging and Chemodynamic/Photothermal Combined Therapy

“…[14] Recently, the second NIR PAI window (NIR-II, 1000-1700 nm) has attracted attention owing to its low background signal interference, high resolution, and deep tissue penetration in vivo. [15] Few NIR-II PA contrast agents have been reported, including gold nanorods, [16] copper sulfide nanoparticles, [17] and semiconductor polymer nanoparticles; [18] unfortunately, these are often not appropriate for the specific properties of the targeted molecules, resulting in some limitations in their applications.…”

Development of Second Near-Infrared Photoacoustic Imaging Agents

“…Inorganic Materials Metallic Nanomaterials Metallic nanomaterials, represented by gold, silver, and copper, can achieve high light absorption and excellent photothermal conversion through a localized surface plasmon resonance (LSPR) effect. For example, gold nanostructures are widely used as molecular imaging agents in disease surveillance due to their unique physicochemical and optical properties, such as unique plasma surface absorption, mild surface chemistry, superior biocompatibility, and relative inertness [22][23][24][25][26][27]. To enhance light absorption in the NIR-II region, the main design strategies of gold nanostructures are as follows:…”