Photochemical Properties and Stability of BODIPY Dyes

Revealing tumor cells and tissues with high selectivity through folic acid-targeted nanofluorescence probes responsive to acidic microenvironments

Tumor-specific fluorescent probes must fulfill the dual requirements of targeted accumulation within tumors and high-resolution imaging capabilities. To achieve both tumor-targeted accumulation and high-resolution imaging performance, we developed a composite comprising an acid-responsive bodipy conjugated to amphiphilic PEG-b-PLA polymer, along with folic acid (FA)-modified PEG-b-PLA as a targeting moiety for active tumor-specific accumulation. Finally, a novel assembly of hybrid fluorescent nanoparticles was successfully synthesized by integrating these two components, demonstrating exceptional responsiveness to acidic conditions for fluorescence excitation and remarkable tumor-targeted accumulation capabilities. We conducted comprehensive in vitro and in vivo investigations employing techniques such as analysis of physicochemical properties, fluorescence-based probes detection at varying pH levels, assessment of in vitro cytotoxicity, evaluation of cellular uptake capacity, analysis of lysosomal co-localization imaging, examination of tumor fluorescence images in vivo, and investigation of biological distribution patterns. The results demonstrated that the acid-responsive nanofluorescence probe we designed and synthesized possesses desirable physical and chemical characteristics, including a small particle size and low cytotoxicity. Moreover, it exhibits rapid real-time response to acidic environments and displays enhanced fluorescence intensity, enabling the real-time tracking of probe entry into tumor cells as well as intracellular lysozyme accumulation. We achieved highly specific in vivo tumor visualization by combining nanoprobes targeting folate receptor. Through imaging cervical tumor mice, we demonstrated the precise imaging performance and high targeted accumulation of FA-targeted nanofluorescence probes in tumor tissue. Furthermore, we confirmed the in vivo safety of the FA-targeted nanofluorescence probe through biological distribution analysis. These findings highlight the potential widespread application of FA-targeted acid-responsive nanofluorescence probes for selective imaging of tumor cells and tissues.

Effect of meso-substituents and medium properties on the photo- and pH-stability, penetration efficiency into bacterial and microscopic fungi cells of terpene-BODIPY conjugates

In order to expand the arsenal of tools and areas for practical use of BODIPY dyes as bifunctional fluorescent theranostics, we studied the effect of the meso-substituents nature and medium properties on photo- and pH-stability, efficiency of singlet oxygen generation, and affinity to biostructures of terpene-BODIPY conjugates. The BODIPYs fused with myrtenol or thiotherpenoid via carboxylic acid residues exhibit high stability over a wide pH range and the presence of a bulky substituent at the meso-position of BODIPY conjugates increases their photostability two-fold compared to structurally related meso-unsubstituted analogues. Furthermore, the photodegradation rate of the conjugates directly depends on their ability to generate singlet oxygen and the course probability of the corresponding red-ox reactions involving reactive oxygen species. The conjugate of BODIPY with a thiotherpenoid demonstrated high ability to penetrate the membranes of filamentous and yeast-like fungi and bind to membrane of organelles in the fungal cell. At the same time, this compound also had a high ability to penetrate into biofilms of Staphylococcus aureus and Klebsiella pneumoniae and into bacterial cells within the matrix, which makes this compound promising for staining intracellular structures of eukaryotic cells and bacteria embedded into biofilms.

BODIPY-Based Molecules for Biomedical Applications

BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) derivatives have attracted attention as probes in applications like imaging and sensing due to their unique properties like (1) strong absorption and emission in the visible and near-infrared regions of the electromagnetic spectrum, (2) strong fluorescence and (3) supreme photostability. They have also been employed in areas like photodynamic therapy. Over the last decade, BODIPY-based molecules have even emerged as candidates for cancer treatments. Cancer remains a significant health issue world-wide, necessitating a continuing search for novel therapeutic options. BODIPY is a flexible fluorophore with distinct photophysical characteristics and is a fascinating drug development platform. This review provides a comprehensive overview of the most recent breakthroughs in BODIPY-based small molecules for cancer or disease detection and therapy, including their functional potential.

BODIPY-labelled acetylcholinesterase reactivators can be encapsulated into ferritin nanovehicles for enhanced bioavailability in the CNS

The BODIPY-labelled oxime reactivator was prepared and used to study its biodistribution into central nervous system. The newly synthesized oxime was found to be weak inhibitor of acetylcholinesterase and strong inhibitor of butyrylcholinesterase. Its reactivation ability for organophosphate inhibited acetylcholinesterase was found similar to a parent oxime. The BODIPY-labelled oxime was further encapsulated into recombinant human H-ferritin and evaluated in vitro and in vivo. The oxime or encapsulated oxime were found to be bioaccumulated primarily in liver and kidneys of mice, but some amount was distributed also to the brain, where it was detectable even after 24 h. The BODIPY-labelled oxime encapsulated to human H-ferritin showed better CNS bioaccumulation and tissue retention at 8 and 24 h time points compared to free oxime, although the fluorescence results might be biased due to BODIPY metabolites identified in tissue homogenates. Taken together, the study demonstrates the first utilization of recombinant ferritins for changing the unfavourable pharmacokinetics of oxime reactivators and brings promising results for follow-up studies.

Long-Wavelength Absorbing Benzimidazolo-Chlorin for Enhanced Photodynamic Therapy

In this study, we condensed methyl pyropheophorbide-a (2) with 1,2-phenylenediamine to synthesize benzimidazolo-chlorin (3a) as an effective near-infrared photosensitizer (PS) with an absorption maximum of 730 nm. The ability of 3a to generate singlet oxygen, as well as its photodynamic effect on A549 and HeLa cells, was investigated. PS exhibited strong phototoxicity and negligible dark toxicity. Its structure was examined by UV-visible spectroscopy, nuclear magnetic resonance, and high-resolution fast atom bombardment mass spectrometry.