On the diffusion of hypericin in dimethylsulfoxide/water mixtures-the effect of aggregation

Singlet oxygen lifetime changes in dying glioblastoma cells

Time-resolved phosphorescence detection was employed to determine the lifetime of singlet oxygen in live cells. Using hypericin as a photosensitizer, singlet oxygen was generated in U87MG glioblastoma cells. The phosphorescence of singlet oxygen was detected in aqueous cell suspensions following pulsed laser excitation. Our goal was to eliminate or reduce the problems associated with lifetime measurements in water-based cell suspensions. The apparatus enabled simultaneous singlet oxygen phosphorescence and transient absorption measurements, reducing uncertainty in lifetime estimation. The changes in singlet oxygen lifetime were observed during early and late apoptosis induced by photodynamic action. Our findings show that the effective lifetime of singlet oxygen in the intracellular space of the studied glioblastoma cells is 0.4 μs and increases to 1.5 μs as apoptosis progresses. Another group of hypericin, presumably located in the membrane blebs and the plasma membrane of apoptotic cells, generates singlet oxygen with a lifetime of 1.9 μs.

Imaging of heterogeneity in 3D spheroids of U87MG glioblastoma cells and its implications for photodynamic therapy

BACKGROUND

In recent years, pharmacology and toxicology have emphasised the intention to move from in vivo models to simplified 3D objects represented by spheroidal models of cancer. Mitochondria are one of the subcellular organelles responsible for cell metabolism and are often a lucrative target for cancer treatment including photodynamic therapy (PDT).

METHODS

Hanging droplet-grown glioblastoma cells were forced to form spheroids with heterogeneous environments that were characterised by fluorescence microscopy and flow cytometry using fluorescent probes sensitive to oxidative stress and apoptosis. PDT was induced with hypericin at 590 nm.

RESULTS

It was found that the metabolic activity of the cells in the periphery and core of the spheroid was different. Higher oxidative stress and induction of caspase-3 were observed in the peripheral layers after PDT. These parts were more destabilised and showed higher expression of LC3B, an autophagic marker. However, the response of the whole system to the treatment was controlled by the cells in the core of the spheroids, which were hardly affected by the treatment. It has been shown that the depth of penetration of hypericin into this system is an important limiting step for PDT and the induction of autophagy and apoptosis.

CONCLUSIONS

In this work, we have described the fluorescence imaging of vital mitochondria, caspase-3 production and immunostaining of autophagic LC3B in cells from glioblastoma spheroids before and after PDT. Overall, we can conclude that this model represents an in vitro and in vivo applicable alternative for the study of PDT in solid microtumours.

Validation of an Innovative Chromatographic Method for Hypericin Quantification in Nanostructured Lipid Carriers

BACKGROUND

Hypericin (HYP) is a natural compound widely used as a food supplement. The encapsulation of HYP into nanosystems, such as nanostructured lipid carriers (NLC), is a promising strategy for delivering this lipophilic molecule and protecting it from degradation.

OBJECTIVE

This study aims to develop and validate an analytical method to quantify the encapsulation efficiency of HYP in NLC.

METHOD

A reverse-phase high-performance liquid chromatography (HPLC) method was developed and validated according to the International Conference on Harmonization (ICH) guide Q2 (R1). NLC was prepared through the ultrasonication method, and HYP encapsulation efficiency was evaluated using the validated method.

RESULTS

Separation was achieved using an isocratic mobile phase composed of acetonitrile, methanol, and ammonium acetate buffer (10 mM, pH 5.0) (54:36:10, v/v/v) and a reverse stationary phase. The specificity, linearity, precision, accuracy, and robustness of the method were assessed and confirmed during the validation. Furthermore, the validated method was able to determine the encapsulation efficiency of HYP in NLC.

CONCLUSIONS

The HPLC method was validated, and the results indicated the ability of NLC to deliver HYP compounds for further application as a food supplement.

HIGHLIGHTS

HYP is used as a food supplement and for photodynamic therapy (PDT). The developed method was specific, linear, precise, accurate, and robust. NLCs showed a high ability to encapsulate HYP.

Biocompatible zeolite-dye composites with anti-amyloidogenic properties

One of the most attractive approaches in biomedicine and pharmacy is the application of multifunctional materials. The mesoporous structure of clinoptilolite (CZ) absorbs various types of substances and can be used as a model for studying the carriers for targeted drug delivery with controlled release. CZ-dye composites are fabricated by incorporation into clinoptilolite pores commonly used dyes, aluminum phthalocyanine, zinc porphine, and hypericin. We examined and compared the effect of pure dyes and CZ-dye composites on insulin amyloidogenesis. The formation of insulin amyloid fibrils and the disassembly of preformed fibrils is significantly affected by any of the three compounds, however, the strongest effect is observed for aluminum phthalocyanine indicating a structurally-dependent anti-amyloidogenic activity of the dyes. The incorporation of dyes into CZ particles resulted in enhanced anti-amyloidogenic activity in comparison to pure CZ particles. The cell metabolic activity, biocompatibility and fluorescence biodistribution of the dyes entrapped in the composites were tested in vitro (U87 MG cells) and in vivo in the quail chorioallantoic membrane model. Considering the photoactive properties of the dyes used, we assume their applicability in photodiagnostics and photodynamic therapy. It can also be expected that their anti-amyloidogenic potential can be enhanced by photodynamic effect.

The potential effect of leptin co-administration on photodynamic damage using quail chorioallantoic membrane model

BACKGROUND

The chorioallantoic membrane (CAM) of the Japanese quail is an excellent model for studying photodynamic therapy (PDT) due to its rich vascularization. PDT is used not only in oncological treatment but also in infectious diseases, or psoriasis, where it yields significant advantages. This treatment also has its limitations, such as burning, itching, erythema, redness, swelling, and delayed wound healing. The aim of this study was to analyse the potentially protective properties of the tissue hormone leptin during PDT.

METHODS

Japanese quail embryos incubated ex ovo were used in this experiment. On the 9th day of embryonic development, leptin (5 μg) and photosensitiser hypericin (79 μM) were topically applied, followed by irradiation. The effect of leptin co-administration was evaluated from CAM images and histological structure analysis, histological samples, and qPCR, where the expression of genes involved in angiogenesis, apoptosis, and oxidative stress was monitored.

RESULTS

We observed vascular damage in all experimental groups, the highest damage was found after the application of hypericin without leptin coadministration. Histological analysis confirmed the protective effect of leptin. qPCR analysis presented differences in FREK gene expression, but also in genes involved in oxidative stress like SOD, NRF-1, NRF-2, and GPX7. The application of leptin significantly reduced the expression of apoptosis regulatory proteins CASP3, cytochrome C, and APAF1.

CONCLUSIONS

Our results in the CAM model suggest a possible protective effect of leptin to prevent PDT damage and aid in the subsequent regeneration of target tissues after antimicrobial PDT.

Redistribution of hydrophobic hypericin from nanoporous particles of SBA-15 silica in vitro, in cells and in vivo

Nanoporous silica is nowadays used in various fields of nano- and micro-materials research. The advantage of nanoporous material is that it can be filled with various hydrophilic and hydrophobic molecules, which are then delivered to the target cells and tissues. In the present study, we have studied the interaction of nanoporous silica with hydrophobic and photodynamically active molecule - hypericin. Hypericin was adsorbed on/in SBA-15 silica, which led to the disappearance of its fluorescence due to hypericin aggregate formation. However, it was observed here that hypericin can be easily redistributed from these particles towards proteins and lipids in serum and cells in vitro and in vivo. Moreover, the charged surface character of SBA-15 pores forced the creation of protein/lipid corona on particles. Such complex enabled monomerization of hypericin on the surface of particles presented by fluorescence in the corona and singlet oxygen production suitable for photodynamic therapy (PDT). The PDT efficacy achieved by introducing the new construct into the PDT protocol was comparable to the efficacy of hypericin PDT. In conclusion, this study demonstrates a promising approach for the delivery of hydrophobic photosensitizers to cancer cells by nanoporous silica using fluorescence techniques.

Photoactivity of hypericin: from natural product to antifungal application

Considering the multifaceted and increasing application of photodynamic therapy (PDT), in recent years the antimicrobial employment of this therapy has been highlighted, because of the antiviral, antibacterial, antiparasitic, and antifungal activities that have already been demonstrated. In this context, research focussed on antimycological action, especially for treatment of superficial infections, presents promising growth due to the characteristics of these infections that facilitate PDT application as new therapeutic options are needed in the field of medical mycology. Among the more than one hundred classes of photosensitizers the antifungal action of hypericin (Hyp) stands out due to its ability to permeate the lipid membrane and accumulate in different cytoplasmic organelles of eukaryotic cells. In this review, we aim to provide a complete overview of the origin, physicochemical characteristics, and optimal alternative drug deliveries that promote the photodynamic action of Hyp (Hyp-PDT) against fungi. Furthermore, considering the lack of a methodological consensus, we intend to compile the best strategies to guide researchers in the antifungal application of Hyp-PDT. Overall, this review provides a future perspective of new studies and clinical possibilities for the advances of such a technique in the treatment of mycoses in humans.

Selectively Identifying Exposed-over-Unexposed C-C+ Pairs in Human Telomeric i-Motif Structures with Length-Dependent Polymorphism

The i-motif structure (iM) has attracted much attention, because of its in vivo bioactivity and wide in vitro applications such as DNA-based switches. Herein, the length-dependent folding of cytosine-rich repeats of the human telomeric 5'-(CCCTAA)_n-1CCC-3' (iM-n, where n = 2-8) was fully explored. We found that iM-4, iM-5, and iM-8 mainly form the intramolecular monomer iM structures, while a tetramolecular structure populates only for iM-3. However, iM-6 and iM-7 have the potential to fold as well into the dimeric iM structures besides the monomer ones. The natural hypericin (Hyp) was used as the polymorphism-selective probe to recognize the iM structures. Interestingly, only iM-3, iM-6, and iM-7 can efficiently switch on the Hyp fluorescence by specifically binding with the outmost C-C⁺ base pairs that are exposed directly to solution. However, other iM structures that fold in a way with a coverage of the outmost C-C⁺ pairs by loop sequences are totally unavailable for the Hyp binding. Theoretical modeling indicates that adaptive π-π and cation-π interactions contribute to the Hyp recognition toward the exposed C-C⁺ pairs. This specific iM recognition can be boosted by a photocatalytic DNAzyme construct. Our work provides a reliable fluorescence method to selectively explore the polymorphism of iM structures.

Spheroidal Model of SKBR3 and U87MG Cancer Cells for Live Imaging of Caspase-3 during Apoptosis Induced by Singlet Oxygen in Photodynamic Therapy

Aspects related to the response of cells to photodynamic therapy (PDT) have been well studied in cell cultures, which often grow in monolayers. In this work, we propose a spheroidal model of U87MG and SKBR3 cells designed to mimic superficial tumor tissue, small spheroids (<500 µm) suitable for confocal fluorescence microscopy, and larger spheroids (>500 µm) that can be xenografted onto quail chorioallantoic membrane (CAM) to study the effects of PDT in real time. Hypericin was used as a model molecule for a hydrophobic photosensitizer that can produce singlet oxygen (1O2). 1O2 production by hypericin was detected in SKBR3 and U87MG spheroid models using a label-free technique. Vital fluorescence microscopy and flow cytometry revealed the heterogeneity of caspase-3 distribution in the cells of the spheroids. The levels of caspase-3 and apoptosis increased in the cells of spheroids 24 h after PDT. Lactate dehydrogenase activity was evaluated in the spheroids as the most reliable assay to detect differences in phototoxicity. Finally, we demonstrated the applicability of U87MG spheroids on CAM in photodiagnostics. Overall, the variability and applicability of the prepared spheroid models were demonstrated in the PDT study.

Multifunctional Nanoplatforms as a Novel Effective Approach in Photodynamic Therapy and Chemotherapy, to Overcome Multidrug Resistance in Cancer

It is more than sixty years since the era of modern photodynamic therapy (PDT) for cancer began. Enhanced selectivity for malignant cells with a reduced selectivity for non-malignant cells and good biocompatibility along with the limited occurrence of side effects are considered to be the most significant advantages of PDT in comparison with conventional therapeutic approaches, e.g., chemotherapy. The phenomenon of multidrug resistance, which is associated with drug efflux transporters, was originally identified in relation to the application of chemotherapy. Unfortunately, over the last thirty years, numerous papers have shown that many photosensitizers are the substrates of efflux transporters, significantly restricting the effectiveness of PDT. The concept of a dynamic nanoplatform offers a possible solution to minimize the multidrug resistance effect in cells affected by PDT. Indeed, recent findings have shown that the utilization of nanoparticles could significantly enhance the therapeutic efficacy of PDT. Additionally, multifunctional nanoplatforms could induce the synergistic effect of combined treatment regimens, such as PDT with chemotherapy. Moreover, the surface modifications that are associated with nanoparticle functionalization significantly improve the target potential of PDT or chemo-PDT in multidrug resistant and cancer stem cells.

Visible light-driven i-motif-based DNAzymes

DNA foldings provide variant possibilities to develop DNAzymes with remarkable catalytic performance. In spite of fruitful reports on G-quadruplex DNAzymes, four-stranded cytosine-rich i-motifs have not been explored as the potential skeletons of DNAzymes. In this work, we developed a visible light-driven DNAzyme based on human telomeric i-motifs using a natural photosensitizer of hypericin (Hyp) as the cofactor and dissolved oxygen as the oxidant source. The i-motif folding in acidic solution caused the distal thymine overhangs at the 3' and 5' ends to approach each other to provide a favorable binding site for Hyp via an interaction of fully complementary hydrogen bonding. However, the i-motifs without the distal overhangs or with the inappropriate overhang length and the base identity exhibited no binding with Hyp. The binding event converted Hyp from the fully dark state to the emissive state under visible light illumination. Subsequently, the excited Hyp had an opportunity to transfer energy to dissolved oxygen. Resultantly, singlet oxygen (¹O₂) was generated to initiate the substrate oxidation. The catalytic performance of the DNAzyme can be improved using a long-lived mediator. Our developed i-motif-based DNAzyme can be driven by almost the whole range of visible lights, suggesting broad applications in the photocatalytic fields, for example, as an alternative strategy in developing biodevices.

The Interaction of Hypericin with SARS-CoV-2 Reveals a Multimodal Antiviral Activity

Hypericin is a photosensitizing drug that is active against membrane-enveloped viruses and therefore constitutes a promising candidate for the treatment of SARS-CoV-2 infections. The antiviral efficacy of hypericin is largely determined by its affinity toward viral components and by the number of active molecules loaded on single viruses. Here we use an experimental approach to follow the interaction of hypericin with SARS-CoV-2, and we evaluate its antiviral efficacy, both in the dark and upon photoactivation. Binding to viral particles is directly visualized with fluorescence microscopy, and a strong affinity for the viral particles, most likely for the viral envelope, is measured spectroscopically. The loading of a maximum of approximately 30 molecules per viral particle is estimated, despite with marked heterogeneity among particles. Because of this interaction, nanomolar concentrations of photoactivated hypericin substantially reduce virus infectivity on Vero E6 cells, but a partial effect is also observed in dark conditions, suggesting multiple mechanisms of action for this drug.

Alkyl Chain Length in Poly(2-oxazoline)-Based Amphiphilic Gradient Copolymers Regulates the Delivery of Hydrophobic Molecules: A Case of the Biodistribution and the Photodynamic Activity of the Photosensitizer Hypericin

Self-assembled nanostructures of amphiphilic gradient copoly(2-oxazoline)s have recently attracted attention as promising delivery systems for the effective delivery of hydrophobic anticancer drugs. In this study, we have investigated the effects of increasing hydrophobic side chain length on the self-assembly of gradient copolymers composed of 2-ethyl-2-oxazoline as the hydrophilic comonomer and various 2-(4-alkyloxyphenyl)-2-oxazolines as hydrophobic comonomers. We show that the size of the formed polymeric nanoparticles depends on the structure of the copolymers. Moreover, the stability and properties of the polymeric assembly can be affected by the loading of hypericin, a promising compound for photodiagnostics and photodynamic therapy (PDT). We have found the limitation that allows rapid or late release of hypericin from polymeric nanoparticles. The nanoparticles entering the cells by endocytosis decreased the hypericin-induced PDT, and the contribution of the passive process (diffusion) increased the probability of a stronger photoeffect. A study of fluorescence pharmacokinetics and biodistribution revealed differences in the release of hypericin from nanoparticles toward the quail chorioallantoic membrane, a preclinical model for in vivo studies, depending on the composition of polymeric nanoparticles. Photodamage induced by PDT in vivo well correlated with the in vitro results. All formulations studied succeeded in targeting hypericin at cancer cells. In conclusion, we demonstrated the promising potential of poly(2-oxazoline)-based gradient copolymers for effective drug delivery and sequential drug release needed for successful photodiagnostics and PDT in cancer therapy.

Spectroscopic and photostability study of water-soluble hypericin encapsulated with polyvinylpyrrolidone

Hypericin has gained great attention as a powerful photosensitizing and fluorescent agent for photodynamic therapy (PDT) and fluorescence diagnosis (FD) of cancer. However, native hypericin is hydrophobic and nearly insoluble in aqueous media which hinders its photobiological activity. Herein, we demonstrate the encapsulation of hypericin and polyvinylpyrrolidone (hypericin@PVP) as an attractive class of water-soluble formula of hypericin with improved absorption and emission characteristics in water. The absorption and fluorescence properties of the water-soluble hypericin@PVP were studied at room temperature. Also, the photostability of the prepared hypericin@PVP was studied under visible light irradiation. The absorbance and emission measurements confirm the association and binding of hypericin and PVP with a binding constant (K_b) of 1.2 × 10⁵ M^-1. The interaction between hypericin and PVP in water could lead to the dissociation of aggregated hypericin into their monomeric state which is crucial for effective photobiological implementation in PDT and FD. Upon encapsulation with PVP, hypericin showed a significant increase in the fluorescence properties with an enhanced emission intensity of 300% at a PVP concentration of 1 × 10^-4 M. Moreover, water-soluble hypericin@PVP demonstrated high photostability under visible light irradiation with an irradiance of 15 mW/cm² and exposure time up to 150 min. This enhancement in the absorption, emission, and photostability of hypericin in water is related to the effects of encapsulation with PVP and the unique spectroscopic properties of the formulated hypericin@PVP.

The evolving roles of radiolabeled quinones as small molecular probes in necrotic imaging

Necrosis plays vital roles in living organisms which is related closely with various diseases. Non-invasively necrotic imaging can be of great values in clinical decision-making, evaluation of individualized treatment responses, and prediction of patient prognosis. This narrative review will demonstrate how the evolution of quinones for necrotic imaging has been promoted by searching for their active centers. In this review, we summarized the recent developments of various quinones with the continuous simplified π-conjugated cores in necrotic imaging and speculated their possible molecular mechanisms might be attributed to their intercalations with exposed DNA in necrotic tissues. We discussed their clinical challenges of necrotic imaging with quinones and their future translation studies deserved to be explored in personalized patient treatment.

Hypericin photodynamic activity in DPPC liposomes - part II: stability and application in melanoma B16-F10 cancer cells

Hypericin (Hyp) is considered a promising photosensitizer for Photodynamic Therapy (PDT), due to its high hydrophobicity, affinity for cell membranes, low toxicity and high photooxidation activity. In this study, Hyp photophysical properties and photodynamic activity against melanoma B16-F10 cells were optimized using DPPC liposomes (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) as a drug delivery system. This nanoparticle is used as a cell membrane biomimetic model and solubilizes hydrophobic drugs. Hyp oxygen singlet lifetime (τ) in DPPC was approximately two-fold larger than that in P-123 micelles (Pluronic™ surfactants), reflecting a more hydrophobic environment provided by the DPPC liposome. On the other hand, singlet oxygen quantum yield values (Φ_Δ¹O₂) in DPPC and P-123 were similar; Hyp molecules were preserved as monomers. The Hyp/DPPC liposome aqueous dispersion was stable during fluorescence emission and the liposome diameter remained stable for at least five days at 30 °C. However, the liposomes collapsed after the lyophilization/rehydration process, which was resolved by adding the lyoprotectant Trehalose to the liposome dispersion before lyophilization. Cell viability of the Hyp/DPPC formulation was assessed against healthy HaCat cells and high-metastatic melanoma B16-F10 cells. Hyp incorporated into the DPPC carrier presented a higher selectivity index than the Hyp sample previously solubilized in ethanol under the illumination effect. Moreover, the IC₅₀ was lower for Hyp in DPPC than for Hyp pre-solubilized in ethanol. These results indicate the potential of the formulation of Hyp/DPPC for future biomedical applications in PDT treatment.

Imaging Cell Death: Focus on Early Evaluation of Tumor Response to Therapy

Cell death plays a prominent role in the treatment of cancer, because most anticancer therapies act by the induction of cell death including apoptosis, necrosis, and other pathways of cell death. Imaging cell death helps to identify treatment responders from nonresponders and thus enables patient-tailored therapy, which will increase the likelihood of treatment response and ultimately lead to improved patient survival. By taking advantage of molecular probes that specifically target the biomarkers/biochemical processes of cell death, cell death imaging can be successfully achieved. In recent years, with the increased understanding of the molecular mechanism of cell death, a variety of well-defined biomarkers/biochemical processes of cell death have been identified. By targeting these established cell death biomarkers/biochemical processes, a set of molecular imaging probes have been developed and evaluated for early monitoring treatment response in tumors. In this review, we mainly present the recent advances in identifying useful biomarkers/biochemical processes for both apoptosis and necrosis imaging and in developing molecular imaging probes targeting these biomarkers/biochemical processes, with a focus on their application in early evaluation of tumor response to therapy.

In vitro study of disodium cromoglicate as a novel effective hydrotrope solvent for hypericin utilisation in photodynamic therapy

Hypericin (HY) is a naphthodianthrone that naturally occurs in Hypericum perforatum L. It is a promising photosensitiser used in photodynamic therapy for and diagnosis of oncological diseases. However, its hydrophobic character is an obstacle that has prevented its efficient use. The commonly used solvent, dimethyl sulfoxide (DMSO), is a controversial constituent of HY formulations and its use has been rejected by many researchers studying HY both in vitro and in vivo. In this study, we propose the utilisation of hydrotropy to solubilise HY in an aqueous environment. Cromolyn (DSCG) is a non-toxic, well-tolerated, antiallergic drug that has been employed in clinical practice since 1970, and in aqueous solution it acts as a hydrotrope. At a molecular ratio of 1:12,000 HY to DSCG, the compound is able to solubilise HY in aqueous environment. In an HT-29 cell suspension, DSCG (1.8 mmol L-1) considerably enhances the interaction between HY (150 nmol L-1) and HT-29 cells, which leads to an HY fluorescence emission increase with a half-time approximately 2 min compared to 29 min for samples that lack DSCG. Studies using HT-29 adenocarcinoma cells showed that DSCG at a given concentration significantly improved accumulation of HY within cells compared to DMSO (p < 0.05) despite the relative resistance of the HT-29 cell line to HY-PDT. Though no significant difference between total reactive oxygen species production was observed for photoactivated HY dissolved in DMSO and DSCG, significant singlet oxygen generation by photoactivated HY dissolved in a DSCG-containing water solution at the studied molecular ratio was confirmed. We also clarified that DSCG does not act as a scavenger of ABTS and galvinoxyl free radicals. The results from an MTT assay showed that DSCG also significantly enhanced the cytotoxicity of photoactivated HY compared to DMSO (p < 0.05). This study has demonstrated the ability of DSCG to act as a solvent of HY and enhance the effectiveness of HY-PDT compared to the commonly used organic solvent, DMSO.

Importance of Hypericin-Bcl2 interactions for biological effects at subcellular levels

Hypericin (Hyp) is a naturally occurring compound used as photosensitizer in photodynamic therapy and diagnosis. Recently, we have shown that Hyp presence alone, without illumination, resulted in substantial biological effects at several sub-cellular levels. Hyp induced changes in cellular ultrastructure, mitochondria function and metabolism, and distribution of Bcl2 proteins in malignant and non-malignant cells. The molecular mechanisms that underlie Hyp light-independent effects are still elusive. We have hypothesized that Bcl2-Hyp interactions might be one possible mechanism. We performed molecular docking studies to determine the Hyp-Bcl2 interaction profile. Based on the interaction profiles small Bcl2 peptide segments were selected for further study. We designed small peptides corresponding to Bcl2 BH3 and BH1 domains and tested the binding of Hyp and Bcl2 known inhibitor, ABT263, to the peptides in computer modeling and in vitro binding studies. We employed endogenous tryptophan and tyrosine in the BH3 and BH1 peptides, respectively, and their fluorescent properties to show interaction with Hyp and ABT263. Overall, our results indicate that Hyp can interact with Bcl2 protein at its BH3-BH1 hydrophobic groove, and this interaction may trigger changes in intracellular distribution of Bcl2 proteins. In addition, our computer modeling results suggest that Hyp also interacts with other anti-apoptotic members of Bcl2 family similar to the known BH3 mimetics. Our findings are novel and might contribute to understanding Hyp light-independent effects. In addition, they may substantiate the therapeutic use of Hyp as a BH3 mimetic molecule to enhance other cancer treatments.

From Protohypericin to Hypericin: Photoconversion Analysis Using a Time-Resolved Thermal Lens Technique

Hypericin (Hyp) is a natural compound with interesting photophysical and pharmacological properties, which has been used in photodynamic therapy and photodynamic inactivation of microorganisms. Its synthesis is based on a series of chemical processes that ends with a light-drug interaction by the photoconversion of protohypericin (pHyp) to Hyp. Although this photosensitizer is used in a variety of medical applications, the photophysical and photochemical mechanisms involved in the final step related to the photo production of Hyp are not completely understood at the molecular level. Protohypericin concentration, solvents, light irradiation under different wavelengths, and a sort of variables could play an important role in predicting the yielding of this photoconversion process. Here, we used the high-sensitive and remote measurement characteristics of the time-resolved thermal lens technique to investigate the relation between the light-induced photoconversion rate of pHyp to Hyp and the initial concentration pHyp. The results show a linear dependence of the photoreaction rate with the concentration of pHyp, indicating that the overall reaction process includes steps comprising the formation of distinct intermediate species. We demonstrate the applicability of the thermal lens technique for the photochemical characterization of photosensitive drugs at low concentration levels.

Hypericin-Loaded Carbon Nanohorn Hybrid for Combined Photodynamic and Photothermal Therapy in Vivo

Photodynamic therapy (PDT) of hypericin (Hyp) is hampered by poor water solubility and photostability. Incorporation of photosensitizers into nanocarriers has been designed to solve these issues. Herein, SWNH-Hyps nanohybrids were first fabricated by loading hypericin on the surface of single-walled carbon nanohorns (SWNHs) through ??? interaction and exhibited high solubility and stability in aqueous water. SWNH-Hyps could be utilized for a single platform for cancer therapy because it could simultaneously generate enough reactive oxygen species and hyperthermia using light irradiation. Moreover, the SWNHs not only improved water solubility, photostability, and therapy effects of Hyp but also protected it from light degradation. SWNH-Hyps could effectively ablate 4T1 cells by photodynamic/photothermal synergistic therapy upon 590 and 808 nm light irradiations compared with PDT. Furthermore, remarkable tumor cell death as well as tumor growth inhibition was proved via photothermal therapy and PDT of SWNH-Hyps under 590 and 808 nm light irradiations, which demonstrated that synergistic anticancer ability of SWNH-Hyps was better than that of free Hyp in vivo. Such a simple and facile adsorption method improved water solubility of Hyp and then enhanced its therapy effect, which displays that SWNHs can be hopefully used in medicines in the future.

Mucoadhesive In Situ Gelling Liquid Crystalline Precursor System to Improve the Vaginal Administration of Drugs

The vaginal mucosa is a very promising route for drug administration due to its high permeability and the possibility to bypass first pass metabolism; however, current vaginal dosage forms present low retention times due to their dilution in vaginal fluids, which hampers the efficacy of many pharmacological treatments. In order to overcome these problems, this study proposes to develop a mucoadhesive in situ gelling liquid crystalline precursor system composed of 30% of oleic acid and cholesterol (7:1), 40% of ethoxylated and propoxylated cetyl alcohol, and 30% of a dispersion of 16% Poloxamer 407. The effect of the dilution with simulated vaginal fluid (SVF) on this system was evaluated by polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), rheological studies, texture profile analysis (TPA), mucoadhesion study, in vitro drug release test using hypericin (HYP) as drug model, and cytotoxicity assay. PLM and SAXS confirmed the formation of an isotropic system. After the addition of three different concentrations of SVF (30, 50, and 100%), the resultant formulations presented anisotropy and characteristics of viscous lamellar phases. Rheology shows that formulations with SVF behaved as a non-Newtonian fluid with suitable shear thinning for vaginal application. TPA and mucoadhesion assays indicated the formation of long-range ordered systems as the amount of SVF increases which may assist in the fixation of the formulation on the vaginal mucosa. The formulations were able to control about 75% of the released HYP demonstrating a sustained release profile. Finally, all formulations acted as safe vaginal drug delivery systems.

Copolymeric micelles as efficient inert nanocarrier for hypericin in the photodynamic inactivation of Candida species

Aim: To evaluate the efficacy of photodynamic inactivation (PDI) mediated by hypericin encapsulated in P-123 copolymeric micelles (P123-Hyp) alone and in combination with fluconazole (FLU) against planktonic cells and biofilm formation of Candida species Materials & methods: PDI was performed using P123-Hyp and an LED device with irradiance of 3.0 mW/cm2 . Results: Most of isolates (70%) were completely inhibited with concentrations up to 2.0 μmol/l of HYP and light fluence of 16.2 J/cm2. FLU-resistant strains had synergic effect with P123-HYP-PDI and FLU. The biofilm formation was inhibited in all species, in additional the changes in Candida morphology observed by scanning electron microscopy. Conclusion: P123-Hyp-PDI is a promising option to treat fungal infections and medical devices to prevent biofilm formation and fungal spread.

Evaluation of Necrosis Avidity and Potential for Rapid Imaging of Necrotic Myocardium of Radioiodinated Hypocrellins

PURPOSE

Rapid noninvasive delineation of necrotic myocardium in ischemic regions is very critical for risk stratification and clinical decision-making but still challenging. This study aimed to evaluate the necrosis avidity of radioiodinated hypocrellins and its potential for rapidly imaging necrotic myocardium.

PROCEDURES

The aggregation constants of four natural hypocrellins were analyzed by UV/vis spectroscopy. Then, they were radiolabeled with iodine-131 by iodogen oxidation method. Necrosis avidity of iodine-131-labeled hypocrellins was evaluated in rat models with reperfused liver infarction and muscular necrosis by gamma counting, autoradiography, and histopathology. Their pharmacokinetic properties were examined in normal rats. The potential of iodine-131-labeled hypomycin A ([¹³¹I]HD) for early imaging of necrotic myocardium was explored in rat models with reperfused myocardial infarction. Finally, the possible mechanism of necrosis avidity was investigated by in vitro DNA binding and in vivo blocking experiments.

RESULTS

The aggregation constants of four hypocrellins were all much smaller than that of hypericin, a most studied necrosis avid agent. The radiochemical purities of the four radiotracers after purification were all greater than 95 %, and more than 90 % of tracers remained intact after incubation in rat serum for 24 h. Among the four tracers, [¹³¹I]HD exhibited the highest necrotic to viable tissue uptake ratio and the fastest blood clearance. The necrotic myocardium could be clearly visualized 4 h after injection of [¹³¹I]HD by single-photon emission computed tomography/X-ray computed tomography (SPECT/CT). DNA binding studies suggested that HD could bind to DNA through intercalation. Blocking studies demonstrated that uptake of [¹³¹I]HD in necrotic muscle could be significantly blocked by excess unlabeled HD and ethidium bromide with 67 and 60 % decline at 6 h after coinjection, respectively.

CONCLUSIONS

[¹³¹I]HD can be used to rapidly visualize necrotic myocardium. The necrosis avidity mechanism of [¹³¹I]HD may be attributed to its binding to the exposed DNA in necrotic tissues.

Selective Photodynamic Effects on Breast Cancer Cells Provided by p123 Pluronic®- Based Nanoparticles Modulating Hypericin Delivery

BACKGROUND

Breast cancer is the most relevant type of cancer and the second cause of cancer- related deaths among women in general. Currently, there is no effective treatment for breast cancer although advances in its initial diagnosis and treatment are available. Therefore, the value of novel anti-tumor therapeutic modalities remains an immediate unmet need in clinical practice. Following our previous work regarding the properties of the Pluronics with different photosensitizers (PS) for photodynamic therapy (PDT), in this study we aimed to evaluate the efficacy of supersaturated hypericin (HYP) encapsulated on Pluronic® P123 (HYP/P123) against breast cancer cells (MCF-7) and non-tumorigenic breast cells (MCF-10A).

METHODS

Cell internalization and subcellular distribution of HYP/P123 was confirmed by fluorescence microscopy. The phototoxicity and citototoxicity of HYP/P123 was assessed by trypan blue exclusion assay in the presence and absence of light. Long-term cytotoxicity was performed by clonogenic assay. Cell migration was determined by the wound-healing assay. Apoptosis and necrosis assays were performed by annexin VFITC/ propidium Iodide (PI) by fluorescence microscopy.

RESULTS

Our results showed that HYP/P123 micelles had high stability and high rates of binding to cells, which resulted in the selective internalization in MCF-7, indicating their potential to permeate the membrane of these cells. Moreover, HYP/P123 micelles accumulated in mitochondria and endoplasmic reticulum organelles, resulting in the photodynamic cell death by necrosis. Additionally, HYP/P123 micelles showed effective and selective time- and dose dependent phototoxic effects on MCF-7 cells but little damage to MCF-10A cells. HYP/P123 micelles inhibited the generation of cellular colonies, indicating a possible capability to prevent the recurrence of breast cancer. We also demonstrated that HYP/P123 micelles inhibit the migration of tumor cells, possibly by decreasing their ability to form metastases.

CONCLUSION

Taken together, the results presented here indicate a potentially useful role of HYP/P123 micelles as a platform for HYP delivery to more specifically and effectively treat human breast cancers through photodynamic therapy, suggesting they are worthy for in vivo preclinical evaluations.

Improved photodynamic effect through encapsulation of two photosensitizers in lipid nanocapsules

Photodynamic therapy (PDT) has developed into a new clinical and non-invasive treatment for cancer over the past 30 years. By the combination of three non-toxic partners, i.e. a photosensitizer (PS), molecular oxygen (O₂) and light, cytotoxic reactive oxygen species (ROS) are locally produced leading to irreversible vascular and cellular damage. In the present study, we report for the first time that the combination of two photosensitizers (2 PSs: Protoporphyrin IX, PpIX and Hypericin, Hy) loaded in the same lipid nanocapsules (LNCs) leads to enhanced photodynamic therapy efficiency when compared with previously reported systems. The 2 PS-loaded LNCs are shown to increase the in vitro phototoxicity at the nanomolar range (IC₅₀ = 274 and 278 nM on HeLa and MDA-MB-231 cell lines, respectively), whereas the corresponding single PS-loaded LNCs at the same concentration exhibit a phototoxicity two times lower. Intracellular localization in HeLa cells indicates a subcellular asymmetry of PpIX and Hy, in the plasma, ER membranes and round internal structures. The biodistribution of LNCs was studied upon different routes of injection into Swiss nude mice; based on the obtained data, LNCs were injected intratumorally and used to slow the growth of xenograft tumors in mice. The results obtained in this study suggest that the combination of two or more PSs may be a promising strategy to improve the efficacy of conventional photodynamic therapy as well as to reduce dark toxicity.

Phosphorescence Kinetics of Singlet Oxygen Produced by Photosensitization in Spherical Nanoparticles. Part II. The Case of Hypericin-Loaded Low-Density Lipoprotein Particles

The phosphorescence kinetics of singlet oxygen produced by photosensitized hypericin (Hyp) molecules inside low-density lipoprotein (LDL) particles was studied experimentally and by means of numerical and analytical modeling. The phosphorescence signal was measured after short laser pulse irradiation of aqueous Hyp/LDL solutions. The Hyp triplet state lifetime determined by a laser flash-photolysis measurement was 5.3 × 10^-6 s. The numerical and the analytical model described in part I of the present work (DOI: 10.1021/acs.jpcb.8b00658) were used to analyze the observed phosphorescence kinetics of singlet oxygen. It was shown that singlet oxygen diffuses out of LDL particles on a time scale shorter than 0.1 μs. The total (integrated) concentration of singlet oxygen inside LDL is more than an order of magnitude smaller than the total singlet oxygen concentration in the solvent. The time course of singlet oxygen concentrations inside and outside the particles was calculated using simplified representations of the LDL internal structure. The experimental phosphorescence data were fitted by a linear combination of these concentrations using the emission factor E (the ratio of the radiative singlet oxygen depopulation rate constants inside and outside LDL) as a fitting parameter. The emission factor was determined to be E = 6.7 ± 2.5. Control measurements were carried out by adding sodium azide, a strong singlet oxygen quencher, to the solution.

Excitation of triplet states of hypericin in water mediated by hydrotropic cromolyn sodium salt

Hypericin (Hyp) is a hydrophobic pigment found in plants of the genus Hypericum which exhibits low levels of solubility in water. This work shows that the solubility of Hyp can be significantly increased through the addition of cromolyn disodium salt (DSCG). Performed studies using UV-VIS absorption and fluorescence spectroscopies demonstrate that Hyp remains in a predominantly biologically photodynamic active monomeric form in the presence of DSCG at concentrations ranging from 4.6×10^-3 to 1.2×10^-1mol·L^-1. The low association constant between Hyp and DSCG (K_a=71.7±2M^-1), and the polarity value of 0.3 determined for Hyp in a DSCG-water solution, lead to a suggestion that the monomerization of Hyp in aqueous solution can be explained as a result of the hydrotropic effect of DSCG. This hydrotropic effect is most likely a result of interactions between two relative rigid aromatic rings of DSCG and a delocalized charge on the surface of the Hyp molecule. The triplet-triplet (T-T) electronic transition observed in is Hyp in the presence of DSCG suggests a possible production of reactive oxygen species once Hyp is irradiated with visible light in a DSCG aqueous solution.

Effects of Glycosylation on Biodistribution and Imaging Quality of Necrotic Myocardium of Iodine-131-Labeled Sennidins

PURPOSE

Sennidins are necrosis-avid agents for noninvasive assessment of myocardial viability which is important for patients with myocardial infarction (MI). However, high accumulation of radioactivity in the liver interferes with the assessment of myocardial viability. In this study, we compared sennidins with sennosides to investigate the effects of glycosylation on biodistribution and imaging quality of sennidins.

PROCEDURES

Sennidin A (SA), sennidin B (SB), sennoside A (SSA), and sennoside B (SSB) were labeled with I-131. In vitro binding to necrotic cells and hepatic cells and in vivo biodistribution in rats with muscular necrosis were evaluated by gamma counting, autoradiography, and histopathology. Single photon emission computed tomography/computed tomography (SPECT/CT) images were acquired in rats with acute MI.

RESULTS

The uptake of [¹³¹I]SA, [¹³¹I]SSA, [¹³¹I]SB, and [¹³¹I]SSB in necrotic cells was significantly higher than that in viable cells (p < 0.05). Hepatic cells uptake of [¹³¹I]SSA and [¹³¹I]SSB were 7-fold and 10-fold lower than that of corresponding [¹³¹I]SA and [¹³¹I]SB, respectively. The biodistribution data showed that the radioactivities in the liver and feces were significantly lower with [¹³¹I]sennosides than those with [¹³¹I]sennidins (p < 0.01). Autoradiography showed preferential accumulation of these four radiotracers in necrotic areas of muscle, confirmed by histopathology. SPECT/CT imaging studies showed better image quality with [¹³¹I]SSB than with [¹³¹I]SB due to less liver interference.

CONCLUSIONS

Glycosylation significantly decreased the liver uptake and improved the quality of cardiac imaging. [¹³¹I]SSB may serve as a promising necrosis-avid agent for noninvasive assessment of myocardial viability.

Comparative in vitro study of photodynamic activity of hypericin and hypericinates in MCF-7 cells

In this work we present a comparative in vitro study of photodynamic activity between hypericin (HYP) and some hypericinates (hypericin ionic pair with lysine or N-methylglucamine) in human mammary adenocarcinoma cells (MCF-7). The toxicity and phototoxicity of hypericin and hypericinates were compared, as well as their cellular uptake and localization and mutagenic, genotoxic and clonogenic capacity. Our results demonstrate that different cationic moieties promote differences in the hypericinate solubility in a biological environment, and can influence the cellular localization and the phototoxicity of the photosensitizer. It was verified that hypericinates have better efficiency to generate singlet oxygen than HYP, and a lower aggregation in biological medium. In vitro assays have shown that HYP and the hypericinates are able to permeate the MCF-7 cell membrane and accumulated in organelles near the nucleus. The difference in location, however, was not determinant to the cell death mechanism, and a higher prevalence of apoptosis for all studied compounds occurred. The photodynamic studies indicated that hypericinates were more effective than HYP and were able to inhibit the formation of cellular colonies, suggesting a possible ability to prevent the recurrence of tumors. It also appears that all compounds have relative safety for mutagenicity and genotoxicity, which opens up a further safe route for application in in vivo studies.

Formation of Large Hypericin Aggregates in Giant Unilamellar Vesicles-Experiments and Modeling

The incorporation of hypericin (Hyp) from aqueous solutions into giant unilamellar vesicle (GUV) membranes has been studied experimentally and by means of kinetic Monte Carlo modeling. The time evolution of Hyp fluorescence originating from Hyp monomers dissolved in the GUV membrane has been recorded by confocal microscopy and while trapping individual GUVs in optical tweezers. It was shown that after reaching a maximum, the fluorescence intensity gradually decreased toward longer times. Formation of oversized Hyp clusters has been observed on the GUV surface at prolonged time. A simplified kinetic Monte Carlo model is presented to follow the aggregation/dissociation processes of Hyp molecules in the membrane. The simulation results reproduced the basic experimental observations: the scaling of the characteristic fluorescence decay time with the vesicle diameter and the buildup of large Hyp clusters in the GUV membrane.

Estimation of PKCδ autophosphorylation in U87 MG glioma cells: combination of experimental, conceptual and numerical approaches

Golgi apparatus (GA) is a center for lipid metabolism and the final target of ceramide pathway, which may result in apoptosis. In this work localization of highly hydrophobic hypericin is followed by time-resolved imaging of NBDC₆ (fluorescent ceramide) in U87 MG glioma cells. Decrease of NBDC₆ fluorescence lifetimes in cells indicates that hypericin can also follow this pathway. It is known that both, ceramide and hypericin can significantly influence protein kinase C (PKC) activity. Western blotting analysis shows increase of PKCδ autophosphorylation at Ser645 (p(S645)PKCδ) in glioma cells incubated with 500 nM hypericin and confocal-fluorescence microscopy distinguishes p(S645)PKCδ localization between GA related compartments and nucleus. Experimental and numerical methods are combined to study p(S645)PKCδ in U87 MG cell line. Image processing based on conceptual qualitative description is combined with numerical treatment via simple exponential saturation model which describes redistribution of p(S645)PKCδ between nucleus and GA related compartments after hypericin administration. These results suggest, that numerical methods can significantly improve quantification of biomacromolecules (p(S645)PKCδ) directly from the fluorescence images and such obtained outputs are complementary if not equal to typical used methods in biology.

Excretion and toxicity evaluation of 131I-Sennoside A as a necrosis-avid agent

1. Sennoside A (SA) is a newly identified necrosis-avid agent that shows capability for imaging diagnosis and tumor necrosis targeted radiotherapy. As a water-soluble compound, ¹³¹I-Sennoside A (¹³¹I-SA) might be excreted predominately through the kidneys with the possibility of nephrotoxicity. 2. To further verify excretion pathway and examine nephrotoxicity of ¹³¹I-SA, excretion and nephrotoxicity were appraised. The pharmacokinetics, hepatotoxicity and hematotoxicity of ¹³¹I-SA were also evaluated to accelerate its possible clinical translation. All these studies were conducted in mice with ethanol-induced muscular necrosis following a single intravenous administration of 131I-SA at 18.5 MBq/kg or 370 MBq/kg. 3. Excretion data revealed that ¹³¹I-SA was predominately (73.5% of the injected dose (% ID)) excreted via the kidneys with 69.5% ID detected in urine within 72 h post injection. Biodistribution study indicated that ¹³¹I-SA exhibited initial high distribution in the kidneys but subsequently a fast renal clearance, which was further confirmed by the results of autoradiography and single-photon emission computed tomography-computed tomography (SPECT-CT) imaging. The maximum necrotic to normal muscle ratio reached to 7.9-fold at 48 h post injection, which further verified the necrosis avidity of ¹³¹I-SA. Pharmacokinetic parameters showed that ¹³¹I-SA had fast blood clearance with an elimination half-life of 6.7 h. Various functional indexes were no significant difference (p > 0.05) between before administration and 1 d, 8 d, 16 d after administration. Histopathology showed no signs of tissue damage. 4. These data suggest ¹³¹I-SA is a safe and promising necrosis-avid agent applicable in imaging diagnosis and tumor necrosis targeted radiotherapy.

Differential diagnosis of gallstones by using hypericin as a fluorescent optical imaging agent

AIM: To explore the feasibility of using hypericin as an optical imaging probe with affinity for cholesterol for differential fluorescent detection of human gallstones.

METHODS: Cholesterol, mixed and pigment stones from cholecystectomy patients were incubated with hypericin or solvent. After 72 h, the stones were analysed for fluorescence (365 nm) and treated with 2-propanol/dimethyl sulfoxide for high performance liquid chromatography (HPLC) analysis. Rats with virtual gallbladder containing human cholesterol, mixed or pigment gallstones (VGHG) received 5 mg/kg hypericin or solvent and VGHG rats with cholesterol stones were given different hypericin doses (5-15 mg/kg). Twelve hours later, the stones were analysed at 365 nm. Biliary excretion and metabolites of hypericin were assessed in common bile duct (CBD) cannulated rats for 9 h using fluorospectrometry, HPLC and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS).

RESULTS: Homogeneous high fluorescence was seen on cholesterol stones either pre-incubated with hypericin or extracted from VGHG rats receiving hypericin. Mixed stones showed a dotted fluorescent pattern, whereas pigment and solvent-treated ones lacked fluorescence. HPLC showed 7.68, 6.65 and 0.08 × 10^-3 M of cholesterol in extracts from cholesterol, mixed, and pigment gallstones, respectively. Hypericin accounted for 2.0, 0.5 and 0.2 × 10^-6 M in that order. On cholesterol stones from VGHG rats receiving different hypericin doses, a positive correlation was observed between dose and fluorescence. In the bile from CBD-cannulated rats, fluorescence represented 20% of the injected dose with two peaks in 9 h. HPLC analysis revealed that hypericin conjugates reached 60% of the peak area. By MALDI-TOF MS, hypericin-glucuronide was detected.

CONCLUSION: This study proves the potential use of hypericin for differential fluorescent detection of human gallstones regarding their chemical composition.

Molecular Dynamics Studies of Liposomes as Carriers for Photosensitizing Drugs: Development, Validation, and Simulations with a Coarse-Grained Model

Liposomes are proposed as drug delivery systems and can in principle be designed so as to cohere with specific tissue types or local environments. However, little detail is known about the exact mechanisms for drug delivery and the distributions of drug molecules inside the lipid carrier. In the current work, a coarse-grained (CG) liposome model is developed, consisting of over 2500 lipids, with varying degrees of drug loading. For the drug molecule, we chose hypericin, a natural compound proposed for use in photodynamic therapy, for which a CG model was derived and benchmarked against corresponding atomistic membrane bilayer model simulations. Liposomes with 21-84 hypericin molecules were generated and subjected to 10 microsecond simulations. Distribution of the hypericins, their orientations within the lipid bilayer, and the potential of mean force for transferring a hypericin molecule from the interior aqueous "droplet" through the liposome bilayer are reported herein.

Synthesis and Evaluation of 131I-Skyrin as a Necrosis Avid Agent for Potential Targeted Radionuclide Therapy of Solid Tumors

An innovative anticancer approach targeted to necrotic tissues, which serves as a noncancerous and generic anchor, may present a breakthrough. Necrosis avid agents with a flat conjugate aromatic structure selectively accumulate in necrotic tissues, but they easily form aggregates that undesirably distribute to normal tissues. In this study, skyrin, a dianthraquinone compound with smaller and distorted π-cores and thus decreased aggregates as compared with hypericin (Hyp), was designed to target necrosis for tumor therapy. Aggregation studies of skyrin by UV/vis spectroscopy showed a smaller self-association constant with skyrin than with Hyp. Skyrin was labeled by iodine-131 with a radiochemical purity of 98% and exhibited good stability in rat serum for 72 h. In vitro cell uptake studies showed significant difference in the uptake of ¹³¹I-skyrin by necrotic cells compared to normal cells (P < 0.05). Compared in rats with liver and muscle necrosis, radiobiodistribution, whole-body autoradiography, and SPECT/CT studies revealed higher accumulation of ¹³¹I-skyrin in necrotic liver and muscle (p < 0.05), but lower uptake in normal organs, relative to that of ¹³¹I-Hyp. In mice bearing H22 tumor xenografts treated with combretastatin A4 disodium phosphate, the highest uptake of ¹³¹I-skyrin was found in necrotic tumor. In conclusion, ¹³¹I-skyrin appears a promising agent with reduced accumulation in nontarget organs for targeted radionuclide therapy of solid tumors.

Exploring diagnostic potentials of radioiodinated sennidin A in rat model of reperfused myocardial infarction

Non-invasive "hot spot imaging" and localization of necrotic tissue may be helpful for definitive diagnosis of myocardial viability, which is essential for clinical management of ischemic heart disease. We labeled Sennidin A (SA), a naturally occurring median dianthrone compound, with (131)I and evaluated (131)I SA as a potential necrosis-avid diagnostic tracer agent in rat model of reperfused myocardial infarction. Magnetic resonance imaging (MRI) was performed to determine the location and dimension of infarction. (131)I-SA was evaluated in rat model of 24-hour old reperfused myocardial infarction using single-photon emission computed tomography/computed tomography (SPECT/CT), biodistribution, triphenyltetrazolium chloride (TTC) histochemical staining, serial sectional autoradiography and microscopy. Gamma counting revealed high uptake and prolonged retention of (131)I SA in necrotic myocardium and fast clearance from non-targeted tissues. On SPECT/CT images, myocardial infarction was persistently visualized as well-defined hotspots over 24h, which was confirmed by perfect matches of images from post-mortem TTC staining and autoradiography. Radioactivity concentration in infarcted myocardium was over 9 times higher than that of the normal myocardium at 24h. With favorable hydrophilicity and stability, radioiodinated SA may serve as a necrosis-avid diagnostic agent for assessment of myocardial viability.

Radiopharmaceutical evaluation of (131)I-protohypericin as a necrosis avid compound

Hypericin is a necrosis avid agent useful for nuclear imaging and tumor therapy. Protohypericin, with a similar structure to hypericin except poorer planarity, is the precursor of hypericin. In this study, we aimed to investigate the impact of this structural difference on self-assembly, and evaluate the necrosis affinity and metabolism in the rat model of reperfused hepatic infarction. Protohypericin appeared less aggregative in solution compared with hypericin by fluorescence analysis. Biodistribution data of (131)I-protohypericin showed the percentage of injected dose per gram of tissues (%ID/g) increased with time and reached to the maximum of 7.03 at 24 h in necrotic liver by gamma counting. The maximum ratio of target/non-target tissues was 11.7-fold in necrotic liver at 72 h. Pharmacokinetic parameters revealed that the half-life of (131)I-protohypericin was 14.9 h, enabling a long blood circulation and constant retention in necrotic regions. SPECT-CT, autoradiography, and histological staining showed high uptake of (131)I-protohypericin in necrotic tissues. These results suggest that (131)I-protohypericin is a promising necrosis avid compound with a weaker aggregation tendency compared with hypericin and it may have a broad application in imaging and oncotherapy.

Necrosis targeted combinational theragnostic approach using radioiodinated Sennidin A in rodent tumor models

Residual cancer cells and subsequent tumor relapse is an obstacle for curative cancer treatment. Tumor necrosis therapy (TNT) has recently been developed to cause residual tumor regression or destruction. Here, we exploited the avidity of the sennidin A (SA) tracer and radioiodinated SA (¹³¹I-SA) to necrotic tumors in order to further empower TNT. We showed high uptake and prolonged retention of SA in necrotic tumors and a quick clearance in other non-targeted tissues including the liver. On SPECT-CT images, tumor mass appeared persistently as a hotspot. Based on the prominent targetability of ¹³¹I-SA to the tumor necrosis, we designed a combinational theragnostic modality. The vascular disrupting agent (VDA) combretastatin A4 phosphate (CA4P) was used to cause massive tumor necrosis, which formed the target of ¹³¹I-SA that subsequently killed the residual tumor cells by cross-fire irradiation of beta particles. Consequently, ¹³¹I-SA combined with CA4P significantly inhibited tumor growth, extended tumor doubling time and prolonged mean animal survival. In conclusion, ¹³¹I-SA in combination with necrosis inducing drugs/therapies may generate synergetic tumoricidal effects on solid malignancies by means of primary debulking and secondary cleansing process.

Evaluation of hypericin: effect of aggregation on targeting biodistribution

Hypericin (Hy) has shown great promise as a necrosis-avid agent in cancer imaging and therapy. Given the highly hydrophobic and π-conjugated planarity characteristics, Hy tends to form aggregates. To investigate the effect of aggregation on targeting biodistribution, nonaggregated formulation (Non-Ag), aggregated formulation with overconcentrated Hy in dimethyl sulfoxide (Ag-DMSO) solution, and aggregated formulation in water solution (Ag-water) were selected by fluorescence measurement. They were labeled with ¹³¹I and evaluated for the necrosis affinity in rat model of reperfused hepatic infarction by gamma counting and autoradiography. The radioactivity ratio of necrotic liver/normal liver was 17.1, 7.9, and 6.4 for Non-Ag, Ag-DMSO, and Ag-water, respectively. The accumulation of two aggregated formulations (Ag-DMSO and Ag-water) in organs of mononuclear phagocyte system (MPS) was 2.62 ± 0.22 and 3.96 ± 0.30 %ID/g in the lung, and 1.44 ± 0.29 and 1.51 ± 0.23 %ID/g in the spleen, respectively. The biodistribution detected by autoradiography showed the same trend as by gamma counting. In conclusion, the Non-Ag showed better targeting biodistribution and less accumulation in MPS organs than aggregated formulations of Hy. The two aggregated formulations showed significantly lower and higher accumulation in targeting organ and MPS organs, respectively.

Experimental evaluation of radioiodinated sennoside B as a necrosis-avid tracer agent

Necrosis-avid agents are a class of compounds that selectively accumulate in the necrotic tissues after systemic administration, which can be used for in vivo necrosis imaging and targeted therapies. In order to search for a necrosis-avid tracer agent with improved drugability, we labelled iodine-131 on sennoside B (SB) as a naturally occurring median dianthrone compound. The necrosis targetability and clearance properties of (131)I-SB were evaluated in model rats with liver and muscle necrosis. On SPECT/CT images, a "hot spot" in the infarcted liver lobe and necrotic muscle was persistently observed at 24 h and 72 h post-injection (p.i.). Gamma counting of the tissues of interest revealed a radioactivity ratio of necrotic to viable liver at 4.6 and 3.4 and of necrotic to viable muscle at 7.0 and 8.8 at 24 h and 72 h p.i., respectively. The good match of autoradiographs and fluoromicroscopic images with corresponding histochemical staining suggested preferential uptake of (131)I-SB in necrotic tissue. Pharmacokinetic study revealed that (131)I-SB has an elimination half-life of 8.6 h. This study indicates that (131)I-SB shows not only prominent necrosis avidity but also favourable pharmacokinetics, which may serve as a potential necrosis-avid diagnostic agent for assessment of tissue viability.

Proof-of-principle for simple microshelter-assisted buffer exchange in laser tweezers: interaction of hypericin with single cells

Microshelters (i.e. thin dead-end side-arms of fluid channels) are used to aid buffer exchange in optical tweezers experiments. The basic idea is to transfer trapped objects into microshelters during the buffer exchange process. Particles "hidden" in microshelters become insensitive to extreme flow conditions in the main fluid channel, which minimizes the requirements for the applied flow system. The construction scheme of a simple microshelter system is described. The concept has been tested by fluorescence measurements on hypericin interaction with trapped yeast cells in different environments.