In this study, an original aza-BODIPY system comprising two Gd3+ complexes has been designed and synthesized for magnetic resonance imaging/optical imaging applications, by functionalization of the boron center. This strategy enabled the obtainment of a positively charged bimodal probe, which displays an increased water solubility, optimized photophysical properties in the near-infrared region, and very promising relaxometric properties. The absorption and emission wavelengths are 705 and 741 nm, respectively, with a quantum yield of around 10% in aqueous media. Moreover, the system does not produce singlet oxygen upon excitation, which would be toxic for tissues. The relaxivity obtained is high at intermediate fields (16.1 mM-1 s-1 at 20 MHz and 310 K) and competes with that of bigger or more rigid systems. A full relaxometric and 17O NMR study and fitting of the data using the Lipari-Szabo approach showed that this high relaxivity can be explained by the size of the system and the presence of some small aggregates. These optimized photophysical and relaxometric properties highlight the potential use of such systems for future bimodal imaging studies.

中文翻译：

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Aza-BODIPY平台：迈向MRI和近红外荧光的高效水溶性双峰成像探针。

在这项研究中，通过硼中心的功能化，已设计并合成了包含两个Gd3 +配合物的原始aza-BODIPY系统，用于磁共振成像/光学成像应用。这种策略使得能够获得带正电的双峰探针，该探针显示出增加的水溶性，在近红外区域中优化的光物理性质以及非常有前途的弛豫性质。吸收和发射波长分别为705和741 nm，在水性介质中的量子产率约为10％。此外，该系统在激发时不会产生单线态氧，这对组织有毒。在中间磁场（在20 MHz和310 K下为16.1 mM-1 s-1）下获得的弛豫率很高，并且与更大或更刚性的系统相竞争。完整的弛豫和17O NMR研究以及使用Lipari-Szabo方法进行的数据拟合显示，这种高弛豫性可以通过系统的大小和一些小聚集体的存在来解释。这些优化的光物理和弛豫特性突出了此类系统在未来双峰成像研究中的潜在用途。