Photoacoustic/ultrasound dual-modality contrast agent and its application to thermotherapy

Abstract

Abstract. This study investigates a photoacoustic/ultrasound dual-modality contrast agent, including extending its applications from image-contrast enhancement to combined diagnosis and therapy with site-specific targeting. The contrast agent comprises albumin-shelled microbubbles with encapsulated gold nanorods (AuMBs). The gas-filled microbubbles, whose diameters range from submicrometer to several micrometers, are not only echogenic but also can serve as drug-delivery vehicles. The gold nanorods are used to enhance the generation of both photoacoustic and photothermal signals. The optical absorption peak of the gold nanorods is tuned to 760 nm and is invariant after microbubble encapsulation. Dual-modality contrast enhancement is first described here, and the applications to cellular targeting and laser-induced thermotherapy in a phantom are demonstrated. Photoacoustic imaging can be used to monitor temperature increases during the treatment. The targeting capability of AuMBs was verified, and the temperature increased by 26°C for a laser power of 980 mW, demonstrating the potential of combined diagnosis and therapy with the dual-modality agent. Targeted photo-or acoustic-mediated delivery is also possible.

Penetration depth, concentration and efficiency of transdermal α-arbutin delivery after ultrasound treatment with albumin-shelled microbubbles in mice

“…Albumin-shelled MBs were prepared according to the procedure used in our previous studies (Liao et al, 2012b;Wang et al, 2012;Shih et al, 2013). Briefly, albumin-shelled MBs were generated by sonication in 10 ml of solution containing 140 mg of albumin (Octapharma, Vienna, Austria) and perfluorocarbon gas in physiological saline (pH 7.4, 0.9% sodium chloride) using a sonicator (Branson Ultrasonics, Danbury, CT) for 2 min.…”

Photoacoustic and Ultrasound Imaging with Nanosized Contrast Agents

“…due to the hybrid nature of PAT (i.e., combination of light and US), PAT has been easily integrated with existing US imaging systems [138,139]. The combined system shared the same US detectors.…”

“…Linear increases of the US and PA signals were observed as a function of concentration. As the second example, Figure 10.10d shows the TEM image of encapsulated gold nanorod human serum albumin (HSA)-shelled microbubbles (Aunr-HSA) [139]. The US and PA images acquired from a sample containing Aunr-HSA are shown in Figure 10.10e and f, respectively.…”

“…(e) US and (f) PA images of a phantom containing AuMBs. (reprinted with permission from refs [138,139]…”

In vitro and in vivo mapping of drug release after laser ablation thermal therapy with doxorubicin-loaded hollow gold nanoshells using fluorescence and photoacoustic imaging

“…Thus, both the Grueneisen parameter and photoacoustic signal are directly related to temperature [24,25]. Because it can be used to visualize temperature distribution and nanoparticle contrast agents, PAI is a promising approach to monitoring both temperature during PTA and Dox release and localization [26][27][28]. However, no study has investigated the use of PAI to monitor temperature during PTA and Dox release for localization.…”