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The effect of Gd-DOTA locations within PLGA- b -PEG micelle encapsulated IR-1061 on bimodal over-1000 nm near-infrared fluorescence and magnetic resonance imaging.

Thi Kim Dung DoanMasakazu UmezawaTakanori IchikiMasao KamimuraMasayuki YamaguchiHirofumi FujiiKohei Soga
Published in: Biomaterials science (2022)
Multimodal imaging is attractive in biomedical research because it can provide multidimensional information about objects that individual techniques cannot accomplish. In particular, combining over one-thousand-nanometer near-infrared (OTN-NIR) fluorescence and magnetic resonance (MR) imaging is promising for detecting lesions with high sensitivity and structural information. Herein, we describe the development of a bimodal OTN-NIR/MRI probe from gadolinium-tetraazacyclododecanetetraacetic acid (Gd-DOTA) conjugated poly(lactic- co -glycolic acid)- block -poly(ethylene glycol) copolymer (PLGA- b -PEG) micelle encapsulated IR-1061 at two different locations. One configuration contains Gd-DOTA at the end of the PEG of the hydrophilic shell and the other contains Gd-DOTA at the border of PLGA/PEG. The two structures show remarkable differences in fluorescence and R 1 relaxation rates in biological environments; the structure with Gd-DOTA at the border of PLGA/PEG exhibits stable fluorescence and T 1 signal distribution in live mice. The introduction ratio of Gd-DOTA to PEG is significant for controlling the properties of both structures; a higher Gd-DOTA ratio is preferable for the contrast enhancement effect. We found that Gd-DOTA ratios higher than 10% degraded the fluorescence intensity when Gd-DOTA was bound to the end of PEG. In contrast, the introduction of 70% Gd-DOTA at the border of PLGA/PEG did not exhibit a degraded signal, and the structural stability was enhanced with higher ratios of Gd-DOTA. In conclusion, we confirmed that the location of Gd-DOTA is a crucial factor in designing high-performance probes. The overall properties improve when Gd-DOTA is set on the border of PLGA/PEG. These improvements in the properties by controlling the probe structures are promising for future biomedical applications.
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