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Abstract
Dual-modular imaging approaches combining near-infrared (NIR) fluorescence (FLI) and photoacoustic imaging (PAI) require suitable contrast agents to produce dual-modular signals. Although nanoparticles have been used to develop PAI agents, small molecule-based imaging agents have not been extensively studied, highlighting the need to design new fluorophores with an enhanced multifunctional ability. Thus, in this study, we designed a novel squaraine (SQ)-based dye and reported its rational preparation and conjugation with a cancer targeting peptide. Specifically, benzoindole-derived SQ (BSQ) showed strong absorption and fluorescence properties at above 650 nm under aqueous conditions, with a maximum absorption and emission at 665 and 680 nm, respectively. Moreover, PA signal scanning experiments revealed a maximum signal intensity in the range 680-700 nm. BSQ was also conjugated with cyclic arginine-glycine-aspartic acid (cRGD) to improve its active targeting ability for the αvβ3 integrin, which is overexpressed in various cancer and angiogenic cells. A series of in vitro, in vivo, and ex vivo FLI studies showed that the cRGD conjugated BSQ (BSQ-RGD2) successfully stained and targeted αvβ3 integrin-overexpressing tumor cells and xenografts, which were clearly visualized by FLI and PAI. Therefore, BSQ-RGD2 can successfully be applied to dual-modular imaging of the specific biomarker in living animals.

Affiliations

Yong Dae Park  1 , Jam-Eon Park  2 , Hyeon Sik Kim  3 , Seung-Hyeon Choi  2 , Jung Eun Park  4 , Jongho Jeon  4 , Seung-Hwan Park  2
1 Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 56212, Republic of Korea.
2 Biological Resource Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Jeongeup 56212, Republic of Korea.
3 Medical Photonics Research Center, Korea Photonics Technology Institute, Gwang-ju 61007, Republic of Korea.
4 Department of Applied Chemistry, School of Applied Chemical Engineering, Kyungpook National University, Daegu 41566, Republic of Korea.