Mitochondria-targeted BODIPY dyes for small molecule recognition, bio-imaging and photodynamic therapy

Mitochondria are essential for a diverse array of biological functions. There is increasing research focus on developing efficient tools for mitochondria-targeted detection and treatment. BODIPY dyes, known for their structural versatility and excellent spectroscopic properties, are being actively explored in this context. Numerous studies have focused on developing innovative BODIPYs that utilize optical signals for imaging mitochondria. This review presents a comprehensive overview of the progress made in this field, aiming to investigate mitochondria-related biological events. It covers key factors such as design strategies, spectroscopic properties, and cytotoxicity, as well as mechanism to facilitate their future application in organelle imaging and targeted therapy. This work is anticipated to provide valuable insights for guiding future development and facilitating further investigation into mitochondria-related biological sensing and phototherapy.

Luminescent and Photofunctional Transition Metal Complexes: From Molecular Design to Diagnostic and Therapeutic Applications

There has been emerging interest in the exploitation of the photophysical and photochemical properties of transition metal complexes for diagnostic and therapeutic applications. In this Perspective, we highlight the major recent advances in the development of luminescent and photofunctional transition metal complexes, in particular, those of rhenium(I), ruthenium(II), osmium(II), iridium(III), and platinum(II), as bioimaging reagents and phototherapeutic agents, with a focus on the molecular design strategies that harness and modulate the interesting photophysical and photochemical behavior of the complexes. We also discuss the current challenges and future outlook of transition metal complexes for both fundamental research and clinical applications.

Phototherapeutic anticancer strategies with first-row transition metal complexes: a critical review

Photodynamic therapy (PDT) and photoactivated chemotherapy (PACT) are therapeutic techniques based on a photosensitizer (PS) and light. These techniques allow the spatial and temporal control of the activation of drugs with light. Transition metal complexes are attractive compounds as photoactivatable prodrugs since their excited states can be appropriately designed by subtle modifications of the ligands, the metal centre, or the oxidation state. However, most metal-based PSs contain heavy metals such as Ru, Os, Ir, Pt or Au, which are expensive and non-earth-abundant, contrary to first-row transition metals. In this context, the exploration of the photochemical properties of complexes based on first-row transition metals appears to be extremely promising. This did encourage several groups to develop promising PSs based on these metals. This review presents up-to-date state-of-the-art information on first-row-transition metal complexes, from titanium to zinc in regard to their application as PSs for phototherapeutic applications.

Photodynamic Therapy of Inorganic Complexes for the Treatment of Cancer†

Photodynamic therapy (PDT) is a medicinal tool that uses a photosensitizer and a light source to treat several conditions, including cancer. PDT uses reactive oxygen species such as cytotoxic singlet oxygen (¹ O₂ ) to induce cell death in cancer cells. Chemotherapy has historically utilized the cytotoxic effects of many metals, especially transition metal complexes. However, chemotherapy is a systemic treatment so all cells in a patient's body are exposed to the same cytotoxic effects. Transition metal complexes have also shown high cytotoxicity as PDT agents. PDT is a potential localized method for treating several cancer types by using inorganic complexes as photosensitizing agents. This review covers several in vitro and in vivo studies, as well as clinical trials that reported on the anticancer properties of inorganic pharmaceuticals used in PDT against different types of cancer.

BODIPY-attached zinc(II) complexes of curcumin drug for visible light assisted photo-sensitization, cellular imaging and targeted PDT

Boron-dipyrromethene (BODIPY) based photosensitizers as porphyrinoids and curcumin as natural product possess exciting photophysical features suitable for theranostic applications, namely, imaging and photodynamic therapy (PDT). Limited aqueous solubility and insufficient physiological stability, however, reduce their efficacy significantly. We have designed a novel strategy to deliver these two unusable cytotoxins simultaneously in cancer cells and herein, report the synthesis, characterization and imaging-assisted photocytotoxicity of three zinc(II) complexes containing N³-donor dipicolylamine (dpa) ligands (L^1-3) and O,O-donor curcumin (Hcur) viz. [Zn(L¹)(cur)]Cl (1), [Zn(L²)(cur)]Cl (2) and [Zn(L³)(cur)]Cl (3), where L² and L³ have pendant fluorescent BODIPY and non-emissive di-iodo-BODIPY moieties. Metal chelation imparted remarkable biological stability (pH ∼7.4) to the respective ligands and induces significant aqueous solubility. These ternary complexes could act as replacements of the existing metalloporphyrin-based PDT photosensitizers as their visible-light photosensitizing ability is reinforced by the dual presence of blue light absorbing curcumin and green light harvesting BODIPY units. Complex 2 having emissive BODIPY unit L² and curcumin, showed mitochondria selective localization in HeLa, MCF-7 cancer cells and complex 3, the di-iodinated analogue of complex 2, exhibited type-I/II PDT activity via inducing apoptosis through mitochondrial membrane disruption in cancer cells while being significantly nontoxic in dark and to the healthy cells.

Experimental and theoretical investigations of novel oxidovanadium(IV) juglone complex: DNA/HSA interaction and cytotoxic activity

A new oxidovanadium(IV) complex VO(L)(Jug) (HL = 5-methoxy-1,3-bis (1-methyl-1H-benzo[d]imidazol-2-yl)benzene, Jug = juglone) was synthesized and characterized. Interactions of the V(IV) complex with calf thymus DNA (CT DNA) and human serum albumin were studied using different techniques such as UV-vis and fluorescence emission spectroscopy. The experimental results were confirmed by the molecular docking study. The oxidovanadium(IV) complex can efficiently cleave pUC19 DNA in the presence of Hydrogen peroxide. Also, the in vitro cytotoxicity properties of the oxidovanadium(IV) complex was evaluated against MCF-7, HPG-2 and HT-29 cancer cell lines and HEK293 non-malignant fibroblasts were evaluated and compared with free ligands, VOSO₄ and cisplatin as reference drugs.Communicated by Ramaswamy H. Sarma.