Innus Mohammad

Photoacoustic imaging enhanced by indocyanine green-conjugated single-wall carbon nanotubes

Abstract. A photoacoustic contrast agent that is based on bis-carboxylic acid derivative of indocyanine green (ICG) covalently conjugated to single-wall carbon nanotubes (ICG/SWCNT) is presented. Covalently attaching ICG to the functionalized SWCNT provides a more robust system that delivers much more ICG to the tumor site. The detection sensitivity of the new contrast agent in a mouse tumor model is demonstrated in vivo by our custom-built photoacoustic imaging system. The summation of the photoacoustic tomography (PAT) beam envelope, referred to as the “PAT summation,” is used to demonstrate the postinjection light absorption of tumor areas in ICG- and ICG/SWCNT-injected mice. It is shown that ICG is able to provide 33% enhancement at approximately 20 min peak response time with reference to the preinjection PAT level, while ICG/SWCNT provides 128% enhancement at 80 min and even higher enhancement of 196% at the end point of experiments (120 min on average). Additionally, the ICG/SWCNT enhancement was mainly observed at the tumor periphery, which was confirmed by fluorescence images of the tumor samples. This feature is highly valuable in guiding surgeons to assess tumor boundaries and dimensions in vivo and to achieve clean tumor margins to improve surgical resection of tumors.

Targeting tumor hypoxia with 2-nitroimidazole- indocyanine green dye conjugates

Abstract. Tumor hypoxia is a major indicator of treatment resistance to chemotherapeutic drugs, and fluorescence optical tomography has tremendous potential to provide clinically useful, functional information by identifying tumor hypoxia. The synthesis of a 2-nitroimidazole-indocyanine green conjugate using a piperazine linker (piperazine-2-nitroimidazole-ICG) capable of robust fluorescent imaging of tumor hypoxia is described. In vivo mouse tumor imaging studies were completed and demonstrate an improved imaging capability of the new dye relative to an earlier version of the dye that was synthesized with an ethanolamine linker (ethanolamine-2-nitroimidazole-ICG). Mouse tumors located at imaging depths of 1.5 and 2.0 cm in a turbid medium were imaged at various time points after intravenous injection of the dyes. On average, the reconstructed maximum fluorescence concentration of the tumors injected with piperazine-2-nitroimidazole-ICG was twofold higher than that injected with ethanolamine-2-nitroimidazole-ICG within 3 h postinjection period and 1.6 to 1.7 times higher beyond 3 h postinjection. The untargeted bis-carboxylic acid ICG completely washed out after 3 h postinjection. Thus, the optimal window to assess tumor hypoxia is beyond 3 h postinjection. These findings were supported with fluorescence images of histological sections of tumor samples and an immunohistochemistry technique for identifying tumor hypoxia.

Target tumor hypoxia with 2-nitroimidazole-ICG dye conjugates

In this paper, we have synthesized a second generation tumor hypoxia targeted 2-nitroimidazole-ICG conjugate using piperazine linker (2-nitro-ICG-p) and validated its performance in in vivo tumor targeting. The results have shown that tumor hypoxia can be targeted with twice higher signal strength beyond three hours post-injection while the un-targeted ICG has completely washed out. The improvement of the second generation 2-nitro-ICG-p dyes is 1.2-1.3 times over the first generation 2-nitro-ICG dyes using ethanol linker beyond 3 hours post-injection which is the optimal time-window for evaluating tumor hypoxia.

Single wall carbon nanotube/bis carboxylic acid-ICG as asensitive contrast agent for in vivo tumor imaging inphotoacoustic tomography

In this study, we present a novel photoacoustic contrast agent which is based on bis-carboxylic acid derivative of Indocyanine green (ICG) covalently conjugated to single-wall carbon nanotubes (ICG/SWCNT). Covalently attaching ICG to the functionalized SWCNT provides a more robust system that delivers much more ICG to the tumor site. The detection sensitivity of the new contrast agent in mouse tumor model is demonstrated in vivo by our custom built photoacoustic imaging system. PAT summation signal is defined to show the long-term light absorption of tumor areas in ICG injected mice and ICG/SWCNT injected mice. It is shown that ICG is able to provide 33% enhancement at approximately 20 minutes peak response time referred to pre-injection PAT summation level, while ICG/SWCNT provides 128% enhancement at 80 minutes and even higher enhancement of 196% at the end point of experiments (120 minutes on average). Additionally, the ICG/SWCNT enhancement was mainly observed at the tumor periphery as confirmed by fluorescence images of the tumor samples. This feature is highly valuable in guiding surgeons to assess tumor boundaries and dimensions in vivo and improve surgical resection of tumors for achieving clean tumor margins.

Biodistribution study of 2-nitroimidazole indocyanine green conjugate dye conjugates

Using a fluorescence imager we studied the biodistribution of a new hypoxia probe, piperazine-2-nitroimidazole-ICG in murine tumor models. It showed much higher fluorescence intensity and tumor retention in comparison with its predecessors

Imaging of Tumor Hypoxia using 4-Nitroimidazole ICG-conjugate

We compared in vivo hypoxia targeting of 4-nitroimidazole-piperazine-indocyanine derivative (6) with imidazole- (5) and 2-nitroimidazole-indocyanine dye-conjugate (4). Results showed 1.5-fold and 2.5-fold intensity ratio between each pair. This is also supported by cell and immunohistochemistry results.