Aza-BODIPY nanomicelles as versatile agents for the in vitro and in vivo singlet oxygen-triggered apoptosis of human breast cancer cells

Evaluation of the antineoplastic properties of the photosensitizer biscyanine in 2D and 3D tumor cell models and artificial skin models

BACKGROUND

Photodynamic Therapy (PDT) is a therapeutic modality that combines the application of a photoactive compound (photosensitizer, PS) with low-power light to generate reactive oxygen species in the target tissue, resulting in cytotoxic damage and cell death, while sparing adjacent tissues. The objective of this study was to evaluate the phototoxicity of a cyanine dye with two chromophores (biscyanines, BCD) in systems with varying levels of cellular organization, and we used the Photogem® (a photosensitizer approved by the Brazilian ANVISA agency for clinical use in Photodynamic Therapy) as a positive control.

MATERIALS AND METHODS

The cytotoxicity of the compounds was assessed in vitro in 2D monolayers, 3D spheroid cultures, and artificial skin models. Four tumoral cell lines A375 (melanoma), HCB-541 (cutaneous squamous cell carcinoma), Vu120T and Vu147T (head and neck cancer), and two normal cell lines fibroblastic HFF-1 and keratinocyte HACAT were used in this study. Cell viability, migration, production of reactive oxygen species, expression of proteins linked to DNA damage and repair, internalization, and skin permeation of PS agents.

RESULTS

Light irradiation in the presence of the PS resulted in greater cytotoxic effects for BCD as compared to Photogem®, which was accompanied by an increase in the production of reactive oxygen species including H2O2, elevated levels of cleaved PARP, and a higher rate of phosphorylated H2AX protein. BCD demonstrated enhanced internalization and bioaccumulation in the spheroids and equivalent skin models.

CONCLUSION

BCD, as a photosensitizer, showed higher cytotoxicity, with an increased ability to generate reactive oxygen species. This led to reduced cell viability, inhibited migration, and upregulated DNA damage-related proteins. Additionally, its enhanced cellular uptake improved skin barrier permeability, making BCD a strong candidate for in vivo Photodynamic Therapy.

Biocompatible Aza-BODIPY-Biotin Conjugates for Photodynamic Therapy of Cancer

With an objective to develop efficient photosensitizers to cancerous tissues, we synthesized two novel biocompatible sensitizers based on aza-BODIPYs incorporated with heavy atoms and biotin moieties. The bioconjugates DPR2a and DPR2b exhibited a favorable absorption range (600-750 nm) with excellent triplet-state quantum yields (up to 79%) and singlet oxygen generation yields (up to 75%). In vitro photobiological investigations employing MDA-MB-231 breast cancer cell lines exhibited rapid cellular uptake, negligible dark toxicity, and high photocytotoxicity. The mechanism of cell death of these systems was predominantly due to the mitochondrial damage, leading to apoptosis mediated via the generation of singlet oxygen-triggered reactive oxygen species. The in vivo studies with the representative conjugate DPR2a employing female NOD/SCID mice models showed inhibition in tumor growth and significantly decreased tumor volume post photodynamic therapy (PDT) treatment. Our results validate that both DPR2a and DPR2b with iodine incorporation exhibit favorable and superior photophysical and photobiological aspects and demonstrate thereby their potential applications in imaging and PDT of cancer.

Asymmetric AZA-BODIPY with Optical Gain in the Near-Infrared Region

In recent years, there has been a lot of interest in the development of organic compounds emitting in the near-infrared (NIR) region due to their stimulating applications, such as biosensing and light detection and ranging (LiDAR). Moreover, a lot of effort has been devoted to finding organic emitters with optical gain in the NIR region for lasing applications. In this paper, we present the ultrafast spectroscopy of an asymmetric AZA-BODIPY molecule that shows relevant photophysical changes moving from a diluted solution to a concentrated solution and to a spin-coated film. The diluted solution and the spin-coated film show a bleaching band and a stimulated emission band in the visible region, while the very concentrated solution displays a broad (150 nm) and long-living (more than 400 ps) optical gain band in the NIR region, centered at 900 nm. Our results pave the way for a new organic laser system in a near-infrared spectral region.

Design, Spectral Characteristics, Photostability, and Possibilities for Practical Application of BODIPY FL-Labeled Thioterpenoid

This paper presents the design and a comparative analysis of the structural and solvation factors on the spectral and biological properties of the BODIPY biomarker with a thioterpene fragment. Covalent binding of the thioterpene moiety to the butanoic acid residue of meso-substituted BODIPY was carried out to find out the membranotropic effect of conjugate to erythrocytes, and to assess the possibilities of its practical application in bioimaging. The molecular structure of the conjugate was confirmed via X-ray, UV/vis-, NMR-, and MS-spectra. It was found that dye demonstrates high photostability and high fluorescence quantum yield (to ~100%) at 514–519 nm. In addition, the marker was shown to effectively penetrate the erythrocytes membrane in the absence of erythrotoxicity. The conjugation of BODIPY with thioterpenoid is an excellent way to increase affinity dyes to biostructures, including blood components.

Femtosecond Spectroscopy and Nonlinear Optical Properties of aza-BODIPY Derivatives in Solution

The fast relaxation processes in the excited electronic states of functionalized aza-boron-dipyrromethene (aza-BODIPY) derivatives (1-4) were investigated in liquid media at room temperature, including the linear photophysical, photochemical, and nonlinear optical (NLO) properties. Optical gain was revealed for nonfluorescent derivatives 3 and 4 in the near infrared (NIR) spectral range under femtosecond excitation. The values of two-photon absorption (2PA) and excited-state absorption (ESA) cross-sections were obtained for 1-4 in dichloromethane using femtosecond Z-scans, and the role of bromine substituents in the molecular structures of 2 and 4 is discussed. The nature of the excited states involved in electronic transitions of these dyes was investigated using quantum-chemical TD-DFT calculations, and the obtained spectral parameters are in reasonable agreement with the experimental data. Significant 2PA (maxima cross-sections ∼2000 GM), and large ESA cross-sections ∼10^-20  m² of these new aza-BODIPY derivatives 1-4 along with their measured high photostability reveal their potential for photonic applications in general and optical limiting in particular.

La(iii)–curcumin-functionalized gold nanocomposite as a red light-activatable mitochondria-targeting PDT agent

Functionalization of La(iii)–curcumin to gold nanoparticles resulted in remarkable red-shifted UV-visible absorption and exhibited remarkable differential photodynamic ability towards cancer cells upon red-light activation.

Amphiphilic Fullerene-BODIPY Photosensitizers for Targeted Photodynamic Therapy

Nanotheranostic tailor-made carriers are potent platforms for the treatment of cancer that propound a number of advantages over conventional agents for photodynamic therapy (PDT). Herein, four new heavy atom free amphiphilic glucose-BODIPY-fullerene dyads (14-17) endowed with carbohydrate units in the styryl units, which can also form nanomicelles (14-17NM) with Tween 80 for PDT are reported. Glucose-BODIPY-fullerene systems (14-17) and related nanomicelles (14-17NM) have been prepared to emcee efficient singlet oxygen generation upon light irradiation. In vitro anti-tumor effects of the compounds 14-17 and 14-17NM in the presence of light and in darkness have been investigated with K562 human chronic myelogenous leukemia suspension cells. Anti-tumor toxicity upon light irradiation was due to the formation of singlet oxygen and reactive oxygen species (ROS). This study may provide an accomplished example of efficient PDT applications based on nanovehicles fabricated with universal spin converter, fullerene, light harvesting unit, BODIPY dyes conjugated with targeting units to fight against cancer.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

The role of photodynamic therapy in breast cancer - A review of in vitro research

Breast cancer is the most common cancer affecting women and the incidence of occurrence is increasing. Currently, there are many methods of detecting and treating breast cancer. Some treatments have a number of side effects. Photodynamic therapy (PDT) is a minimally invasive method of treatment which uses monochromatic light of low to medium energy to excite previously applied photosensitizers (PS) for ROS production. The purpose of this article is to present a general overview of the use of PDT in in vitro studies of various cancer cell lines. A literature search for articles corresponding to the topic of this review was performed using the PubMed and Scopus databases using the following keywords: 'photodynamic therapy', 'breast cancer', and 'photosensitizer(s).' Much of the reviewed literature is based on evaluations of the cytotoxic potential of various PSs, particularly against the MCF-7 cell line, and enhancement of PDT potential with nanotechnology. Research on photodynamic effects in vitro may be helpful in the pre-clinical search for optimal methods for in vivo clinical treatment.

Benzothiadiazole-Substituted Aza-BODIPY Dyes: Two-Photon Absorption Enhancement for Improved Optical Limiting Performances in the Short-Wave IR Range

Aza-boron dipyrromethenes (aza-BODIPYs) presenting a benzothiadiazole substitution on upper positions are described. The strong electron-withdrawing effect of the benzothiadiazole moiety permits enhancement of the accepting strength and improves the delocalization of the aza-BODIPY core to attain a significant degree of electronic communication between the lower donating groups and the upper accepting groups. The nature of the intramolecular charge transfer is studied both experimentally and theoretically. Linear spectroscopy highlighted the strongly redshifted absorption and emission of the synthesized molecules with recorded fluorescence spectra over 1000 nm. Nonlinear optical properties were also investigated. Strong enhancement of the two-photon absorption of the substituted dyes compared with the unsubstituted one (up to 4520 GM at 1300 nm) results in an approximately 15-20 % improvement of the optical power limiting performances. These dyes are therefore a good starting point for further improvement of optical power limiting in the short-wave IR range.

Design of novel photosensitizers and controlled singlet oxygen generation for photodynamic therapy

Photodynamic therapy (PDT) is a promising strategy in cancer treatment with its relatively lower side effect profile.

Restricted suitability of BODIPY for caging in biological applications based on singlet oxygen generation

Recent studies report the boron-dipyrromethene (BODIPY) moiety to be interesting for caging applications in photopharmacology based on its response to irradiation with wavelengths in the biooptical window. Thus, in a model study, we investigated the meso-methyl-BODIPY caged CDK2 inhibitor AZD5438 and aimed to assess the usability of BODIPY as a photoremovable protecting group in photoresponsive kinase inhibitor applications. Photochemical analysis and biological characterisation in vitro revealed significant limitations of the BODIPY-caged inhibitor concept regarding solubility and uncaging in aqueous solution. Notably, we provide evidence for BODIPY-caged compounds generating singlet oxygen/radicals upon irradiation, followed by photodegradation of the caged compound system. Consequently, instead of caging, a non-specific induction of necrosis in cells suggests the potential usage of BODIPY derivatives for photodynamic approaches.

Biotinylated and fluorophore-incorporated polymeric mixed micelles for tumor cell-specific turn-on fluorescence imaging of Al3

Excessive amounts of Al3+ in the human body can cause adverse effects on immune function and induce several neurodegenerative disorders. So far, most of the reported fluorescent probes for Al3+ present some common drawbacks, such as low sensitivity and poor water solubility. In addition, a number of traditional fluorescent probes failed to image Al3+ in tumor cells due to the lack of tumor cell targeting capacity and cell penetrating abilities. To overcome these shortcomings, we constructed tumor-targeting fluorescent mixed nano-micelles (mPEG-Dye-Biotin) with an average particle size of 21 nm from an amphiphilic polymer containing a Schiff-base fluorescent unit (mPEG-Dye) and another amphiphilic polymer containing a tumor cell recognition ligand (DSPE-PEG-Biotin), through the co-self-assembly of both amphiphilic polymers in water using the film rehydration method. The as-prepared nanoprobe showed a highly sensitive and selective turn-on fluorescence response to Al3+ in aqueous solution with a low detection limit. MTT assay revealed the negligible cytotoxicity of the mPEG-Dye-Biotin nanoprobe to both HeLa cells and COS-7 cells, indicating the safety of mPEG-Dye-Biotin for biological applications. More importantly, the biotinylated nanoprobe showed better ability to enter biotin receptor-positive HeLa cells than that of the non-biotinylated micelle mPEG-Dye, which made it more suitable for imaging Al3+ in biotin receptor-positive tumor cells. This work provides a simple and general strategy to design a highly sensitive and tumor cell-specific metal ion nanoprobe, which can not only be applied in Al3+ imaging, but can also be extended to other ions or biomolecules by changing the incorporated fluorescent unit in the amphiphilic polymer.

Thieno[1,3,2]oxazaborinine-containing aza-BODIPYs with near infrared absorption bands: synthesis, photophysical properties, and device applications

Structurally constrained NIR aza-BODIPYs with thieno[1,3,2]oxazaborinine were synthesized for the first time, enabling their evaluation as NIR photodetectors through fabrication of a single-component device.

Poly-halogenated aza-bodipy dyes with improved solubility as a versatile synthetic platform for the design of photonic materials

The optimization of the solubility in organic solvents of halogenated aza-dipyrromethenes was achieved by substitution of the upper phenyl moieties by branched long alkoxy chains (1f) or by using an OMe–OHex–OMe pattern (1h).

Distribution, Trafficking, and in Vitro Photodynamic Therapy Efficacy of Cholesterol Silicon(IV) Phthalocyanine and Its Nanoparticles in Breast Cancer Cells

A cholesterol silicon(IV) phthalocyanine (Chol-Pc) and a water-soluble Chol-Pc based nanoparticle (DSPE@Chol-Pc), which was prepared using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000] (DSPE-PEG₂₀₀₀) as a nanocarrier were developed. Chol-Pc readily distributed within the cholesterol-rich domains and was preferentially localized in the Golgi apparatus after being transported into the cells. The trafficking of DSPE@Chol-Pc in breast cancer cells was visualized by tracking the fluorescence of Chol-Pc and FITC-labeled DSPE-PEG₂₀₀₀ through two-photonic imaging in real-time. It was discovered that Chol-Pc disassociated from the DSPE-PEG₂₀₀₀ on the plasma membrane and traveled to the cholesterol-rich domains soon afterward. Both DSPE@Chol-Pc and Chol-Pc effectively mediated photodynamic therapy to kill the breast cancer cells. After light irradiation, we found that the organizations of clustered cholesterol-rich domains in cells were destroyed, presumably leading to the death of cells for photodynamic therapy. It should be noted that DSPE@Chol-Pc is highly soluble in aqueous solution and has strong red fluorescence under two-photon excitation. Thus, it could be an excellent probe for detecting cholesterol-rich domains and studying transport processes of cholesterol in living cells.