Comparison of the In Vitro and In Vivo Behavior of a Series of NIR-II-Emitting Aza-BODIPYs Containing Different Water-Solubilizing Groups and Their Trastuzumab Antibody Conjugates.

The development of new fluorescent organic probes effective in the NIR-II region is currently a fast-growing field and represents a challenge in the domain of medical imaging. In this study, we have designed and synthesized an innovative series of aza-boron dipyrromethenes emitting in the NIR-II region. We have investigated the effect of different water-solubilizing groups not only on the photophysical properties of the compounds but also on their in vitro and in vivo performance after bioconjugation to the antibody trastuzumab. Remarkably, we discovered that the most lipophilic compound unexpectedly displayed the most favorable in vivo properties after bioconjugation. This underlines the profound influence that the fluorophore functionalization approach can have on the efficiency of the resulting imaging agent.

First Comparison Study of the In Vitro and In Vivo Properties of a Randomly and Site-Specifically Conjugated SPECT/NIRF Monomolecular Multimodal Imaging Probe (MOMIP) Based on an aza-BODIPY Fluorophore.

Among all approaches in molecular imaging, the combination of near-infrared fluorescence imaging (NIRF) with radioisotopic imaging (PET or SPECT) allows one to benefit from the advantages of each of the imaging techniques, which are very complementary and of comparable sensitivity. To this end, the construction of monomolecular multimodal probes (MOMIP) has made it possible to combine the two imaging modalities within the same molecule, thus limiting the number of bioconjugation sites and yielding more homogeneous conjugates compared with those prepared through sequential conjugation. However, in order to optimize the bioconjugation strategy and, at the same time, the pharmacokinetic and biodistribution properties of the resulting imaging agent, a site-specific approach may be preferred. To further investigate this hypothesis, random and glycan-based site-specific bioconjugation approaches were compared thanks to a SPECT/NIRF bimodal probe based on an aza-BODIPY fluorophore. The overall experiments conducted in vitro and in vivo on HER2-expressing tumors demonstrated a clear superiority of the site-specific approach to improve affinity, specificity, and biodistribution of the bioconjugates.