Photodynamic therapy in oncology

Advances in nanotechnology-assisted photodynamic therapy for neurological disorders: a comprehensive review

Neurological disorders such as neurodegenerative diseases and nervous system tumours affect more than one billion people throughout the globe. The physiological sensitivity of the nervous tissue limits the application of invasive therapies and leads to poor treatment and prognosis. One promising solution that has generated attention is Photodynamic therapy (PDT), which can potentially revolutionise the treatment landscape for neurological disorders. PDT attracted substantial recognition for anticancer efficacy and drug conjugation for targeted drug delivery. This review thoroughly explained the basic principles of PDT, scientific interventions and advances in PDT, and their complicated mechanism in treating brain-related pathologies. Furthermore, the merits and demerits of PDT in the context of neurological disorders offer a well-rounded perspective on its feasibility and challenges. In conclusion, this review encapsulates the significant potential of PDT in transforming the treatment landscape for neurological disorders, emphasising its role as a non-invasive, targeted therapeutic approach with multifaceted applications.

Recent development of nanomaterials-based PDT to improve immunogenic cell death

Photodynamic therapy (PDT) is a clinically approved therapeutic modality for treating oncological and non-oncological disorders. PDT has proclaimed multiple benefits over further traditional cancer therapies including its minimal systemic toxicity and selective ability to eliminate irradiated tumors. In PDT, a photosensitizing substance localizes in tumor tissues and becomes active when exposed to a particular wavelength of laser light. This produces reactive oxygen species (ROS), which induce neoplastic cells to die and lead to the regression of tumors. The contributions of ROS to PDT-induced tumor destruction are described by three basic processes including direct or indirect cell death, vascular destruction, and immunogenic cell death. However, the efficiency of PDT is significantly limited by the inherent nature and tumor microenvironment. Combining immunotherapy with PDT has recently been shown to improve tumor immunogenicity while decreasing immunoregulatory repression, thereby gently modifying the anticancer immune response with long-term immunological memory effects. This review highlights the fundamental ideas, essential elements, and mechanisms of PDT as well as nanomaterial-based PDT to boost tumor immunogenicity. Moreover, the synergistic use of immunotherapy in combination with PDT to enhance immune responses against tumors is emphasized.

Low-symmetry A3B-type 6H-1,4-diazepinoporphyrazines with anti-Kasha effect as promising photosensitizers

A series of tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazines has been synthesized. A temperature-dependent steric effect was applied in the mixed Linstead macrocyclization of phthalonitrile and 5,7-bis(2'-arylethenyl)-6-propyl-6H-1,4-diazepine-2,3-dicarbonitrile to achieve high yield of low-symmetry A3B-type Mg(II) tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazinate. The analysis of photophysical and photochemical properties of the obtained complexes showed the anti-Kasha effect: the ultrafast spin changes successfully compete with the IC. TD-DFT calculations showed that the presence of 1,4-diazepine heterocycle in the porphyrazine structure leads to the formation of additional charge-transfer triplet state T2. We propose, it could participate in the pumping of T1x state alongside with T1y state (these states are degenerate in D4h symmetry) and, therefore, increase singlet oxygen (1Δg) generation. Stable micellar nanoparticles have been obtained based on the tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazine Mg(II) and Zn(II) complexes using polyvinylpyrrolidone. The nanoparticles effectively interact with model biological structures (FBS and brain homogenate), leading to disaggregation of the macrocycles. They also exhibit pronounced phototoxic effects in MCF-7 cells upon red light irradiation. We propose that enhancement in PDT activity could be explained by their increased resistance to aggregation due to the presence of n-propyl substituent directly attached to the C6 position of the 1,4-diazepine moiety. The demonstrated results show the promising potential of tribenzo-6H-1,4-diazepinoporphyrazines as heavy atom-free photosensitizers.

Recent Advances in Chemistry, Mechanism, and Applications of Quantum Dots in Photodynamic and Photothermal Therapy

Semiconductor quantum dots (QD) are a kind of nanoparticle with unique optical properties that have attracted a lot of attention in recent years. In this paper, the characteristics of these nanoparticles and their applications in nanophototherapy have been reviewed. Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has gained special importance because of its high accuracy and local treatment due to the activation of the drug at the tumor site. PDT is a new way of cancer treatment that is performed by activating light-sensitive compounds named photosensitizers (PS) by light. PSs cause the destruction of diseased tissue through the production of singlet oxygen. PTT is another non-invasive method that induces cell death through the conversion of near-infrared light (NIR) into heat in the tumor situation by the photothermal agent (PA). Through using energy transfer via the FRET (Förster resonance energy transfer) process, QDs provide light absorption wavelength for both methods and cover the optical weaknesses of phototherapy agents.

Cellular Mechanisms of Singlet Oxygen in Photodynamic Therapy

In this review, we delve into the realm of photodynamic therapy (PDT), an established method for combating cancer. The foundation of PDT lies in the activation of a photosensitizing agent using specific wavelengths of light, resulting in the generation of reactive oxygen species (ROS), notably singlet oxygen (1O2). We explore PDT's intricacies, emphasizing its precise targeting of cancer cells while sparing healthy tissue. We examine the pivotal role of singlet oxygen in initiating apoptosis and other cell death pathways, highlighting its potential for minimally invasive cancer treatment. Additionally, we delve into the complex interplay of cellular components, including catalase and NOX1, in defending cancer cells against PDT-induced oxidative and nitrative stress. We unveil an intriguing auto-amplifying mechanism involving secondary singlet oxygen production and catalase inactivation, offering promising avenues for enhancing PDT's effectiveness. In conclusion, our review unravels PDT's inner workings and underscores the importance of selective illumination and photosensitizer properties for achieving precision in cancer therapy. The exploration of cellular responses and interactions reveals opportunities for refining and optimizing PDT, which holds significant potential in the ongoing fight against cancer.

Advancements and Obstacles of PARP Inhibitors in Gastric Cancer

Gastric cancer (GC) is a common and aggressive cancer of the digestive system, exhibiting high aggressiveness and significant heterogeneity. Despite advancements in improving survival rates over the past few decades, GC continues to carry a worrisome prognosis and notable mortality. As a result, there is an urgent need for novel therapeutic approaches to address GC. Recent targeted sequencing studies have revealed frequent mutations in DNA damage repair (DDR) pathway genes in many GC patients. These mutations lead to an increased reliance on poly (adenosine diphosphate-ribose) polymerase (PARP) for DNA repair, making PARP inhibitors (PARPi) a promising treatment option for GC. This article presents a comprehensive overview of the rationale and development of PARPi, highlighting its progress and challenges in both preclinical and clinical research for treating GC.

5-aminolevulinic acid-loaded dissolving microneedle array for photodynamic therapy of rheumatoid arthritis on rats

Photodynamic therapy (PDT) is a noninvasive technique that can be used to treat rheumatoid arthritis (RA) by irradiating photosensitizers with specific wavelengths of light to generate reactive oxygen species (ROS), thus leading to targeted cell necrosis. However, efficient delivery of photosensitizers with low side effects is a key issue. We developed a 5-aminolevulinic acid-loaded dissolving microneedle array (5-ALA@DMNA) that can locally and efficiently deliver photosensitizers for RA treatment by PDT. 5-ALA@DMNA was fabricated through a two-step molding process, which was characterized. The effects of 5-ALA-mediated PDT on RA fibroblast-like synoviocytes (RA-FLs) were investigated via in vitro experiments. Adjuvant arthritis rat models were established to evaluate the therapeutic effect of 5-ALA@DMNA-mediated PDT on RA. The results showed that 5-ALA@DMNA could penetrate the skin barrier and efficiently deliver photosensitizers. 5-ALA-mediated PDT can significantly inhibit the migration ability and selectively induce apoptosis of RA-FLs. Moreover, 5-ALA-mediated PDT had a significant therapeutic effect on rats with adjuvant arthritis, which may be related to the upregulation of interleukin (IL)- 4 and IL-10 and downregulation of TNF-α, IL-6, and IL-17. Thus, 5-ALA@DMNA-mediated PDT may be a potential therapy for RA.

Evaluation of Detector Position and Light Fluence Distribution Using an Infrared Navigation System during Pleural Photodynamic Therapy†

Photodynamic therapy (PDT) has been used to treat malignant pleural mesothelioma. Current practice involves delivering light to a prescribed light fluence with a point source, monitored by eight isotropic detectors inside the pleural cavity. An infrared (IR) navigation system was used to track the location of the point source throughout the treatment. The recorded data were used to reconstruct the pleural cavity and calculate the light fluence to the whole cavity. An automatic algorithm was developed recently to calculate the detector positions based on recorded data within an hour. This algorithm was applied to patient case studies and the calculated results were compared to the measured positions, with an average difference of 2.5 cm. Calculated light fluence at calculated positions were compared to measured values. The differences between the calculated and measured light fluence were within 14% for all cases, with a fixed scattering constant and a dual correction method. Fluence-surface histogram (FSH) was calculated for photofrin-mediated PDT to be able to cover 80% of pleural surface area to 50 J cm-2 (83.3% of 60 J cm-2 ). The study demonstrates that it will be possible to eliminate the manual measurement of the detector positions, reducing the patient's time under anesthesia.

A primer on heme biosynthesis

Heme (protoheme IX) is an essential cofactor for a large variety of proteins whose functions vary from one electron reactions to binding gases. While not ubiquitous, heme is found in the great majority of known life forms. Unlike most cofactors that are acquired from dietary sources, the vast majority of organisms that utilize heme possess a complete pathway to synthesize the compound. Indeed, dietary heme is most frequently utilized as an iron source and not as a source of heme. In Nature there are now known to exist three pathways to synthesize heme. These are the siroheme dependent (SHD) pathway which is the most ancient, but least common of the three; the coproporphyrin dependent (CPD) pathway which with one known exception is found only in gram positive bacteria; and the protoporphyrin dependent (PPD) pathway which is found in gram negative bacteria and all eukaryotes. All three pathways share a core set of enzymes to convert the first committed intermediate, 5-aminolevulinate (ALA) into uroporphyrinogen III. In the current review all three pathways are reviewed as well as the two known pathways to synthesize ALA. In addition, interesting features of some heme biosynthesis enzymes are discussed as are the regulation and disorders of heme biosynthesis.

Ferrochelatase: Mapping the Intersection of Iron and Porphyrin Metabolism in the Mitochondria

Porphyrin and iron are ubiquitous and essential for sustaining life in virtually all living organisms. Unlike iron, which exists in many forms, porphyrin macrocycles are mostly functional as metal complexes. The iron-containing porphyrin, heme, serves as a prosthetic group in a wide array of metabolic pathways; including respiratory cytochromes, hemoglobin, cytochrome P450s, catalases, and other hemoproteins. Despite playing crucial roles in many biological processes, heme, iron, and porphyrin intermediates are potentially cytotoxic. Thus, the intersection of porphyrin and iron metabolism at heme synthesis, and intracellular trafficking of heme and its porphyrin precursors are tightly regulated processes. In this review, we discuss recent advances in understanding the physiological dynamics of eukaryotic ferrochelatase, a mitochondrially localized metalloenzyme. Ferrochelatase catalyzes the terminal step of heme biosynthesis, the insertion of ferrous iron into protoporphyrin IX to produce heme. In most eukaryotes, except plants, ferrochelatase is localized to the mitochondrial matrix, where substrates are delivered and heme is synthesized for trafficking to multiple cellular locales. Herein, we delve into the structural and functional features of ferrochelatase, as well as its metabolic regulation in the mitochondria. We discuss the regulation of ferrochelatase via post-translational modifications, transportation of substrates and product across the mitochondrial membrane, protein-protein interactions, inhibition by small-molecule inhibitors, and ferrochelatase in protozoal parasites. Overall, this review presents insight on mitochondrial heme homeostasis from the perspective of ferrochelatase.

Photosensitized co-generation of nitric oxide and singlet oxygen Enhanced toxicity against ovarian cancer cells

Near micromolar concentrations of nitric oxide (NO) induce tumor cells death. However, an appropriate NO load has to be delivered selectively to the tumor site in order to avoid NO loss and secondary NO-induced effects. The encapsulation of millimolar concentrations of a NO source and an appropriate trigger of NO release within phospatidylcholine-based liposomes should provide an efficient tool for the selective release of the needed NO payload. In this work we report the photosensitized generation of singlet oxygen and NO from folate-targeted PEGylated liposomes, containing AlPcS4 as the sensitizer and S-nitrosoglutathione (GSNO), in millimolar amounts, as the NO source. Amounts of singlet oxygen detected outside the liposome when using PEGylated liposomes are near 200 % larger when GSNO is present inside the liposomes as compared to its absence. These liposomes, conjugated to folate, were found to enhance the photosensitized cytotoxicity to A2780CP20 ovarian cancer cells as compared to liposomes containing the sensitizer but no GSNO (30 % as compared to 70 % cell viability) under the conditions of this work. Fluorescense of AlPcS4 was observed inside cells incubated with folate-conjugated liposomes but not with liposomes without folate. The photosensitized activity enhancement by GSNO increased when light fluence or liposome concentration were increased. The majority of ovarian cancer patients are initially diagnosed with disseminated intra-abdominal disease (stages III-IV) and have a 5-year survival of less than 20%. This work suggests a novel ovarian cancer nodules treatment via the use of tumor-targeted liposome nanoparticles with the capability of generating simultaneously reactive oxygen and nitrogen species upon illumination with near-infrared light.

Clinical Development of Metal Complexes as Photosensitizers for Photodynamic Therapy of Cancer

Cancer has emerged over the last decades as one of the deadliest diseases in the world. Among the most commonly used techniques (i.e. surgery, immunotherapy, radiotherapy or chemotherapy), increasing attention has been devoted towards photodynamic therapy. However, the vast majority of clinically applied photosensitizers are not ideal and associated with several limitations including poor aqueous solubility, poor photostability and slow clearance from the body, causing photosensitivity. In an effort to overcome these drawbacks, much attention has been devoted towards the incorporation of a metal ion. Herein, the clinical development of metal-containing compounds including Purlytin® , Lutrin® /Antrin® , Photosens® , TOOKAD® soluble or TLD-1433 is critically reviewed.

Methylene Blue-Based Nano and Microparticles: Fabrication and Applications in Photodynamic Therapy

Methylene blue (MB) has been used in the textile industry since it was first extracted by the German chemist Heinrich Caro. Its pharmacological properties have also been applied toward the treatment of certain diseases such as methemoglobinemia, ifosfamide-induced encephalopathy, and thyroid conditions requiring surgery. Recently, the utilization of MB as a safe photosensitizer in photodynamic therapy (PDT) has received attention. Recent findings demonstrate that photoactivated MB exhibits not only anticancer activity but also antibacterial activity both in vitro and in vivo. However, due to the hydrophilic nature of MB, it is difficult to create MB-embedded nano- or microparticles capable of increasing the clinical efficacy of the PDT. This review aims to summarize fabrication techniques for MB-embedded nano and microparticles and to provide both in vitro and in vivo examples of MB-mediated PDT, thereby offering a future perspective on improving this promising clinical treatment modality. We also address examples of MB-mediated PDT in both cancer and infection treatments. Both in-vitro and in-vivo studies are summarized here to document recent trends in utilizing MB as an effective photosensitizer in PDT. Lastly, we discuss how developing efficient MB-carrying nano- and microparticle platforms would be able to increase the benefits of PDT.

Photodynamic Therapy Review: Principles, Photosensitizers, Applications, and Future Directions

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality that has gained great attention in the past years as a new therapy for cancer treatment. PDT uses photosensitizers that, after being excited by light at a specific wavelength, react with the molecular oxygen to create reactive oxygen species in the target tissue, resulting in cell death. Compared to conventional therapeutic modalities, PDT presents greater selectivity against tumor cells, due to the use of photosensitizers that are preferably localized in tumor lesions, and the precise light irradiation of these lesions. This paper presents a review of the principles, mechanisms, photosensitizers, and current applications of PDT. Moreover, the future path on the research of new photosensitizers with enhanced tumor selectivity, featuring the improvement of PDT effectiveness, has also been addressed. Finally, new applications of PDT have been covered.

A Review of Chemotherapy and Photodynamic Therapy for Lung Cancer Treatment

Cancer is among the leading causes of mortality and morbidity worldwide. Among the different types of cancers, lung cancer is considered to be the leading cause of death related to cancer and the most commonly diagnosed form of such disease. Chemotherapy remains a dominant treatment modality for many types of cancers at different stages. However, in many cases, cancer cells develop drug resistance and become nonresponsive to chemotherapy, thus, necessitating the exploration of alternative and /or complementary treatment modalities. Photodynamic Therapy (PDT) has emerged as an effective treatment modality for various malignant neoplasia and tumors. In PDT, the photochemical interaction of light, Photosensitizer (PS) and molecular oxygen produces Reactive Oxygen Species (ROS), which induces cell death. Combination therapy, by using PDT and chemotherapy, can promote synergistic effect against this fatal disease with the elimination of drug resistance, and enhancement of the efficacy of cancer eradication. In this review, we give an overview of chemotherapeutic modalities, PDT, and the different types of drugs associated with each therapy. Furthermore, we also explored the combined use of chemotherapy and PDT in the course of lung cancer treatment and how this approach could be the last resort for thousands of patients that have been diagnosed by this fatal disease.

Reactive Oxygen Species (ROS): Key components in Cancer Therapies

Reactive oxygen species (ROS) refer to the highly reactive substances, which contain oxygen radicals. Hypochlorous acid, peroxides, superoxide, singlet oxygen, alpha-oxygen and hydroxyl radicals are the major examples of ROS. Generally, the reduction of oxygen (O2) in molecular form produces superoxide (•O2-) anion. ROS are produced during a variety of biochemical reactions within the cell organelles, such as endoplasmic reticulum, mitochondria and peroxisome. Naturally, ROS are also formed as a byproduct of the normal metabolism of oxygen. The production of ROS can be induced by various factors such as heavy metals, tobacco, smoke, drugs, xenobiotics, pollutants and radiation. From various experimental studies, it is reported that ROS act as either tumor suppressing or tumor promoting agent. The elevated levels of ROS can arrest the growth of tumor through the persistent increase in cell cycle inhibition. The increased level of ROS can induce apoptosis by both intrinsic and extrinsic pathways. ROS are considered to be tumor suppressing agent as the production of ROS is due to the use of most of the chemotherapeutic agents in order to activate the cell death. The cytotoxic effect of ROS provides impetus towards apoptosis, but in higher levels, ROS can cause initiation of malignancy that leads to uncontrolled cell death in cancer cells. Whereas, some species of ROS can influence various activities at the cellular level that include cell proliferation. This review highlights the genesis of ROS within cells by various routes and their role in cancer therapies.

Purpurin: A natural anthraquinone with multifaceted pharmacological activities

Purpurin is a naturally occurring anthraquinone isolated from the roots of Rubia cordifolia. Historically, it has been used as a red dye. However, its photosensitizing property and biological effects have deciphered its novel application. Purpurin shows antigenotoxic, anticancer, neuromodulatory, and antimicrobial potential associated with antioxidant action in in vivo and in vitro experiments. A robust antioxidant nature of purpurin is responsible for the majority of its pharmacological effects. It produces anti-inflammatory activity by reducing oxidative stress, which is a fundamental property to target diseases involving endoplasmic reticulum and mitochondrial stress. It can cross the blood-brain barrier and produce neuroprotective effects, including antidepressant and anti-Alzheimer action. It shows antimutagenic property via inhibiting essential CYP-450 enzymes. Interestingly, it gets photosensitized by UV-light and produces target-specific ROS-dependent apoptosis in cancer cells. Therefore, it owns cell killing and cell survival potential subject to the influence of external conditions. Hitherto, limited research studies are performed with purpurin to understand its therapeutic potential. Hence, this review describes and discusses different in vivo, in vitro, and in silico studies performed using purpurin. It also covers physicochemical, pharmacokinetics, and toxicology aspects of purpurin. Moreover, in the end, the prospect of purpurin in the management of cancer has also been proposed.

Potent oxidation of DNA by Ru(ii) tri(polypyridyl) complexes under visible light irradiation via a singlet oxygen-mediated mechanism

The irradiation of Ru(ii) tri(polypridyl) complexes with visible light can induce potent oxidation of DNA mediated by ¹O₂via a type II photosensitization mechanism.

A water soluble carbazolyl-BODIPY photosensitizer with an orthogonal D-A structure for photodynamic therapy in living cells and zebrafish

A novel photosensitizer carbazolyl-BODIPY (Cz-BODIPY) with an orthogonal donor-acceptor structure was developed for photodynamic therapy (PDT). The photosensitizer Cz-BODIPY showed strong singlet oxygen sensitizing capability (ΦΔ = 0.68 in MeOH), excellent water solubility in dilute solution, and high photostability. The photosensitizer Cz-BODIPY exhibited negligible dark cytotoxicity and high phototoxicity (IC50 0.45 μM). Cz-BODIPY could induce cell apoptosis upon light illumination. Three cell states including living cells, apoptotic cells, and dead cells in the PDT process of Cz-BODIPY were determined via the Hoechst 33342/PI dual staining assays. The ROS (reactive oxygen species) generation in living cells during the PDT process of Cz-BODIPY was captured by the ROS detector, dihydroethidium (DHE). The photosensitizer Cz-BODIPY could be assimilated by zebrafish to generate ROS and diminish the integrity of zebrafish tissue upon light illumination. Tumor cell growth could be inhibited by Cz-BODIPY upon light illumination. The photosensitizer Cz-BODIPY displayed potential in real PDT application.

Chemo-photodynamic therapy by pulmonary delivery of gefitinib nanoparticles and 5-aminolevulinic acid for treatment of primary lung cancer of rats

Lung cancer is a severe disease with high mortality. Chemotherapy is one major treatment for lung cancer. However, systemic chemotherapeutics usually distribute throughout the body without specific lung distribution so that serious side effects are unavoidable. Photodynamic therapy (PDT) is occasionally used for lung cancer treatment but photosensitizers are also systemically administered and the bronchoscopic intervention under anesthesia may hurt lung tissues. Here, we combined inhaled chemotherapeutics and photosensitizers for chemo-photodynamic therapy (CPDT) of primary lung cancer of rats with external laser light irradiation. Gefitinib PLGA nanoparticles (GNPs) were prepared. The anti-cancer effects of GNPs and/or a common photosensitizer 5-aminolevulinic acid (5-ALA) were explored on A549 cells (adenocarcinomic human alveolar basal epithelial cells) and primary lung cancer rats after intratracheal administration. External light irradiation was applied due to its higher safety compared to internal light irradiation that may result in injuries after a laser optic fiber was intubated into the lung. The remarkable synergistic effect of CPDT was confirmed although the single therapies were also effective, where the high anti-lung cancer effects were shown and some typical lung cancer markers, including CD31, VEGF, NF-κB p65 and Bcl-2, significantly decreased. Moreover, the treatments attenuated inflammation with the downregulation of TNF-α. The combination of pulmonary drug delivery and chemo-photodynamic therapy is a promising strategy for treatment of lung cancer.

Nanoconjugates of graphene oxide derivatives and meso-tetraphenylporphyrin: a new avenue for anticancer photodynamic therapies – Cell-on-a-Chip analysis

Cell-on-a-Chip analysis of nanoconjugates of graphene oxide derivatives and mesotetraphenylporphyrin as a new selective and effective avenue for anticancer photodynamic therapies.

Ruthenium(II) Conjugates of Boron-Dipyrromethene and Biotin for Targeted Photodynamic Therapy in Red Light

The ruthenium(II) complexes [RuCl(L¹)(L³)]Cl (1), [RuCl(L¹)(L⁴)]Cl (2), [RuCl(L²)(L⁴)]Cl (3), [RuCl(L¹)(L⁵)]Cl (4), and [RuCl(L²)(L⁵)]Cl (5) of NNN-donor dipicolylamine (dpa) bases (L⁴, L⁵) having BODIPY (boron-dipyrromethene) moieties, NN-donor phenanthroline derivatives (L¹, L²), and benzyldipicolylamine (bzdpa, L³) were prepared and characterized by spectroscopic techniques and their cellular localization/uptake and photocytotoxicity studied. Complex 1, as its PF₆ salt (1a), has been structurally characterized with help of a single-crystal X-ray diffraction technique. It has a RuN₅Cl core with the Cl bonded trans to the amine nitrogen atom of bzdpa. The complexes showed intense absorption spectral bands near 500 nm (ε ≈ 58000 M^-1 cm^-1) in 2 and 3 and 654 nm (ε ≈ 80000 M^-1 cm^-1) in 4 and 5 in 1/1 DMSO/DPBS (v/v). Complex 5 having biotin and PEGylated-disteryl BODIPY gave a singlet oxygen quantum yield (Φ_Δ) of ∼0.65 in DMSO. Complex 5 exhibited remarkable PDT (photodynamic therapy) activity (IC₅₀ ≈ 0.02 μM) with a photocytotoxicity index (PI) value of >5000 in red light of 600-720 nm in A549 cancer cells. The biotin-conjugated complexes showed better photocytotoxicity in comparison to nonbiotinylated analogues in A549 cells. The complexes displayed less toxicity in HPL1D normal cells in comparison to A549 cancer cells. The emissive BODIPY complexes 3 and 5 (Φ_F ≈ 0.07 in DMSO) showed significant mitochondrial localization.

Photobiomodulation combined with photodynamic therapy using ruthenium phthalocyanine complexes in A375 melanoma cells: Effects of nitric oxide generation and ATP production

Light irradiation has been used in clinical therapy for several decades. In this context, photobiomodulation (PBM) modulates signaling pathways via ROS, ATP, Ca²⁺, while photodynamic therapy (PDT) generates reactive oxygen species by excitation of a photosensitizer. NO generation could be an important tool when combined with both kinds of light therapy. By using a metal-based compound, we found that PBM combined with PDT could be a beneficial cancer treatment option. We used two types of ruthenium compounds, ([Ru(Pc)], Pc = phthalocyanine) and trans-[Ru(NO)(NO₂)(Pc)]. The UV-vis spectra of both complexes displayed a band in the 660 nm region. In the case of 0.5 μM trans-[Ru(NO)(NO₂)(Pc)], light irradiation at the Q-band reduced the percentage of viable human melanoma (A375) cells to around 50% as compared to [Ru(Pc)]. We hypothesized that these results were due to a synergistic effect between singlet oxygen and nitric oxide. Similar experiments performed with PDT (660 nm) combined with PBM (850 nm) induced more photocytotoxicity using both [Ru(Pc)] and trans-[Ru(NO)(NO₂)(Pc)]. This was interpreted as PBM increasing cell metabolism (ATP production) and the consequent higher uptake of the ruthenium phthalocyanine compounds and more efficient apoptosis. The use of metal-based photosensitizers combined with light therapy may represent an advance in the field of photodynamic therapy.

Investigation of copper-cysteamine nanoparticles as a new photosensitizer for anti-hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a primary malignancy of the liver and occurs predominantly in patients with underlying chronic liver disease and cirrhosis. HCC is now the third leading cause of cancer deaths worldwide, with over 500,000 people affected. However, there is no complete effective (ideal) treatment for liver cancer yet, and the new methods are expected to be discovered. Herein, for the first time, we report the anti-HCC effects of copper-cysteamine nanoparticles (Cu-Cy NPs), a new type of photosensitizers. An in vitro 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay shows that Cu-Cy NPs could significantly reduce the activity of HepG2 cells at a very low dose after a short time of ultraviolet radiation. In addition, we found that cell death was induced by Cu-Cy NPs, which is associated with cellular apoptosis. This implied that apoptosis might be the main mechanism of the Cu-Cy's anti-HCC activity. Furthermore, we found that Cu-Cy NPs obviously inhibited the tumor growth in vivo. More interestingly, we found that the soluble Cu-Cy NPs were able to enter exosomes which were secreted by tumor cells, and exosomes could be used to deliver Cu-Cy NPs to target tumor cells. All these observations suggest that Cu-Cy NPs have a good potential for cancer treatment.

The Cellular Uptake of Sensitizers Bound to Cyclodextrin Carriers

Photodynamic therapy of cancer uses the interaction of sensitizers and light to destroy cancer cells. In this study we tested the cellular uptake of meso-tetrakis(4-sulfonatophenyl)porphine (TPPS4) and its complex PdTPPS4 in the presence or absence of 2–hydroxypropyl-cyclodextrins (hpCDs) on G361 human melanoma cells. Self-fluorescence in G361 cells were measured by Perkin-Elmer LS50B luminometer equipped with well plate reader accessory. Morphological changes in cells have been evaluated using inversion fluorescent microscope Olympus IX 70 and image analysis. The uptake of the sensitizer PdTPPS4 at the given time interval from 1 to 48 hours is markedly higher than the uptake of TPPS4. The highest uptake was found for sensitizer PdTPPS4 in combination with hpβCD. TPPS4 and PdTPPS4 especially in the supramolecular complex with nontoxic cyclodextrin carriers represent efficient sensitizers for photodynamic therapy in vitro on G361 cells.

Recent Progress in Metal-Based Nanoparticles Mediated Photodynamic Therapy

Photodynamic therapy (PDT) is able to non-invasively treat and diagnose various cancers and nonmalignant diseases by combining light, oxygen, and photosensitizers (PSs). However, the application of PDT is hindered by poor water solubility and limited light-penetration depth of the currently available photosensitizers (PSs). Water solubility of PSs is crucial for designing pharmaceutical formulation and administration routes. Wavelength of light source at visible range normally has therapeutic depth less than 1 mm. In this review, focus is on the recent research progress of metal-based nanoparticles being applied in PDT. The potential toxicity of these nanoscales and future directions are further discussed.

Photoactivated in Vitro Anticancer Activity of Rhenium(I) Tricarbonyl Complexes Bearing Water-Soluble Phosphines

Fifteen water-soluble rhenium compounds of the general formula [Re(CO)3(NN)(PR3)]+, where NN is a diimine ligand and PR3 is 1,3,5-triaza-7-phosphaadamantane (PTA), tris(hydroxymethyl)phosphine (THP), or 1,4-diacetyl-1,3,7-triaza-5-phosphabicylco[3.3.1]nonane (DAPTA), were synthesized and characterized by multinuclear NMR spectroscopy, IR spectroscopy, and X-ray crystallography. The complexes bearing the THP and DAPTA ligands exhibit triplet-based luminescence in air-equilibrated aqueous solutions with quantum yields ranging from 3.4 to 11.5%. Furthermore, the THP and DAPTA complexes undergo photosubstitution of a CO ligand upon irradiation with 365 nm light with quantum yields ranging from 1.1 to 5.5% and sensitize the formation of 1O2 with quantum yields as high as 70%. In contrast, all of the complexes bearing the PTA ligand are nonemissive and do not undergo photosubstitution upon irradiation with 365 nm light. These compounds were evaluated as photoactivated anticancer agents in human cervical (HeLa), ovarian (A2780), and cisplatin-resistant ovarian (A2780CP70) cancer cell lines. All of the complexes bearing THP and DAPTA exhibited a cytotoxic response upon irradiation with minimal toxicity in the absence of light. Notably, the complex with DAPTA and 1,10-phenanthroline gave rise to an IC50 value of 6 μM in HeLa cells upon irradiation, rendering it the most phototoxic compound in this library. The nature of the photoinduced cytotoxicity of this compound was explored in further detail. These data indicate that the phototoxic response may result from the release of both CO and the rhenium-containing photoproduct, as well as the production of 1O2.

Plant Lectins Targeting O-Glycans at the Cell Surface as Tools for Cancer Diagnosis, Prognosis and Therapy

Aberrant O-glycans expressed at the surface of cancer cells consist of membrane-tethered glycoproteins (T and Tn antigens) and glycolipids (Lewis a, Lewis x and Forssman antigens). All of these O-glycans have been identified as glyco-markers of interest for the diagnosis and the prognosis of cancer diseases. These epitopes are specifically detected using T/Tn-specific lectins isolated from various plants such as jacalin from Artocarpus integrifola, and fungi such as the Agaricus bisporus lectin. These lectins accommodate T/Tn antigens at the monosaccharide-binding site; residues located in the surrounding extended binding-site of the lectins often participate in the binding of more extended epitopes. Depending on the shape and size of the extended carbohydrate-binding site, their fine sugar-binding specificity towards complex O-glycans readily differs from one lectin to another, resulting in a great diversity in their sugar-recognition capacity. T/Tn-specific lectins have been extensively used for the histochemical detection of cancer cells in biopsies and for the follow up of the cancer progression and evolution. T/Tn-specific lectins also induce a caspase-dependent apoptosis in cancer cells, often associated with a more or less severe inhibition of proliferation. Moreover, they provide another potential source of molecules adapted to the building of photosensitizer-conjugates allowing a specific targeting to cancer cells, for the photodynamic treatment of tumors.

DNA-Targeted Inhibition of MGMT

The cationic porphyrin 5,10,15,20-tetrakis (diisopropyl-guanidine)-21H,23H-porphine (DIGPor) selectively binds to DNA containing O⁶ -methylguanine (O⁶ -MeG) and inhibits the DNA repair enzyme O⁶ -methylguanine-DNA methyltransferase (MGMT). The O⁶ -MeG selectivity and MGMT inhibitory activity of DIGPor were improved by incorporating Zn^II into the porphyrin. The resulting metal complex (Zn-DIGPor) potentiated the activity of the DNA-alkylating drug temozolomide in an MGMT-expressing cell line. To the best of our knowledge, this is the first example of DNA-targeted MGMT inhibition.

Folic Acid-Conjugated Pyropheophorbide a as the Photosensitizer Tested for In Vivo Targeted Photodynamic Therapy

Photodynamic therapy (PDT) is a highly localized and minimally invasive cancer treatment modality with many important advantages, but the lack of ideal photosensitizers (PSs) greatly restricts its clinical utility. To develop new PSs with highly efficient singlet oxygen production and high tumor-localizing ability to reduce damage to healthy adjacent tissues, we conjugated folic acid (FA) with pyropheophorbide a (Pyro), a potent PS with a very high singlet oxygen quantum yield and a high extinction coefficient. In the present work, we describe the synthesis and PDT evaluation of this FA-Pyro conjugate both in vitro and in vivo. This conjugation increased the accumulation of Pyro inside the tumors and improved the efficiency of PDT, resulting in eradication of subcutaneous xenograft KB (human mouth epidermal carcinoma) tumors after only 1 or 2 applications of external near infrared light irradiation. This outstanding PDT outcome in a tumor-bearing mouse model and the simple synthesis of the conjugate should have very good practical potential for clinical application.

The Role of Stress and Stress Adaptations in Determining the Fate of the Bacterial Pathogen Listeria monocytogenes in the Food Chain

The foodborne pathogen Listeria monocytogenes is a highly adaptable organism that can persist in a wide range of environmental and food-related niches. The consumption of contaminated ready-to-eat foods can cause infections, termed listeriosis, in vulnerable humans, particularly those with weakened immune systems. Although these infections are comparatively rare they are associated with high mortality rates and therefore this pathogen has a significant impact on food safety. L. monocytogenes can adapt to and survive a wide range of stress conditions including low pH, low water activity, and low temperature, which makes it problematic for food producers who rely on these stresses for preservation. Stress tolerance in L. monocytogenes can be explained partially by the presence of the general stress response (GSR), a transcriptional response under the control of the alternative sigma factor sigma B (σB) that reconfigures gene transcription to provide homeostatic and protective functions to cope with the stress. Within the host σB also plays a key role in surviving the harsh conditions found in the gastrointestinal tract. As the infection progresses beyond the GI tract L. monocytogenes uses an intracellular infectious cycle to propagate, spread and remain protected from the host's humoral immunity. Many of the virulence genes that facilitate this infectious cycle are under the control of a master transcriptional regulator called PrfA. In this review we consider the environmental reservoirs that enable L. monocytogenes to gain access to the food chain and discuss the stresses that the pathogen must overcome to survive and grow in these environments. The overlap that exists between stress tolerance and virulence is described. We review the principal measures that are used to control the pathogen and point to exciting new approaches that might provide improved means of control in the future.

The enhancing effect of a laser photochemotherapy with cisplatin or zolendronic acid in primary human osteoblasts and osteosarcoma cells in vitro

BACKGROUND

Photodynamic therapies (PDT) have become increasingly popular in the adjuvant treatment of different tumour entities. Chemotherapeutic agents, such as cisplatin may be used in combination with low-level laser therapy (LLLT) as laser photochemotherapy. The aim of this study was to investigate the effect of LLLT on cell bioviability of normal and malignant bone cells under chemotherapeutic conditions with either cisplatin or zolendronic acid in vitro.

METHODS

Primary human osteoblasts (HOB) and an osteosarcoma cell line (Saos-2) were treated with different concentrations of zolendronic acid or cisplatin and irradiated twice with a diode laser (wavelength 670 nm, 120 s, energy outputs of 100mW/cm² , continuous wave mode). Cell viability was tested by XTT-assay and via histomorphological analysis.

RESULTS

LLLT alone increased bioviability for both cell lines. LLLT lowered HOB viability at the three highest concentrations of cisplatin and zolendronic acid. For Saos-2, LLLT reduced cell viability at every concentration of cisplatin. In cases of incubation with zolendronic acid, similar to osteoblasts, LLLT lowered cell viability at the highest concentration only.

CONCLUSIONS

Based on the conditions of this study, laser photochemotherapy may be able to raise the cytotoxicity of cisplatin and zolendronic acid in benign and malignant bone cells. This could be of interest in the development of new therapeutic treatment modalities against neoplastic bone diseases like osteosarcoma.

Combined use of optical spectroscopy and computational methods to study the binding and the photoinduced conformational modification of proteins when NMR and X-ray structural determinations are not an option

The functions of proteins depend on their interactions with various ligands and these interactions are controlled by the structure of the polypeptides. If one can manipulate the structure of proteins, their functions can in principle be modulated. The issue of protein structure-function relationship is not only a central problem in biophysics, but is becoming clear that the ability to "artificially" modify the structure of proteins could be relevant in fields beyond the biomedical area to provide, for instance, light responses in proteins which would not possess such properties in their native state. This chapter presents an overview of the combination of optical electronic and vibrational spectroscopy with various computational methods to investigate the binding between photoactive ligands and proteins.

Photodynamic Therapy in Non-Gastrointestinal Thoracic Malignancies

Photodynamic therapy has a role in the management of early and late thoracic malignancies. It can be used to facilitate minimally-invasive treatment of early endobronchial tumours and also to palliate obstructive and bleeding effects of advanced endobronchial tumours. Photodynamic therapy has been used as a means of downsizing tumours to allow for resection, as well as reducing the extent of resection necessary. It has also been used successfully for minimally-invasive management of local recurrences, which is especially valuable for patients who are not eligible for radiation therapy. Photodynamic therapy has also shown promising results in mesothelioma and pleural-based metastatic disease. As new generation photosensitizers are being developed and tested and methodological issues continue to be addressed, the role of photodynamic therapy in thoracic malignancies continues to evolve.

Small Molecule Microarrays Enable the Identification of a Selective, Quadruplex-Binding Inhibitor of MYC Expression

The transcription factor MYC plays a pivotal role in cancer initiation, progression, and maintenance. However, it has proven difficult to develop small molecule inhibitors of MYC. One attractive route to pharmacological inhibition of MYC has been the prevention of its expression through small molecule-mediated stabilization of the G-quadruplex (G4) present in its promoter. Although molecules that bind globally to quadruplex DNA and influence gene expression are well-known, the identification of new chemical scaffolds that selectively modulate G4-driven genes remains a challenge. Here, we report an approach for the identification of G4-binding small molecules using small molecule microarrays (SMMs). We use the SMM screening platform to identify a novel G4-binding small molecule that inhibits MYC expression in cell models, with minimal impact on the expression of other G4-associated genes. Surface plasmon resonance (SPR) and thermal melt assays demonstrated that this molecule binds reversibly to the MYC G4 with single digit micromolar affinity, and with weaker or no measurable binding to other G4s. Biochemical and cell-based assays demonstrated that the compound effectively silenced MYC transcription and translation via a G4-dependent mechanism of action. The compound induced G1 arrest and was selectively toxic to MYC-driven cancer cell lines containing the G4 in the promoter but had minimal effects in peripheral blood mononucleocytes or a cell line lacking the G4 in its MYC promoter. As a measure of selectivity, gene expression analysis and qPCR experiments demonstrated that MYC and several MYC target genes were downregulated upon treatment with this compound, while the expression of several other G4-driven genes was not affected. In addition to providing a novel chemical scaffold that modulates MYC expression through G4 binding, this work suggests that the SMM screening approach may be broadly useful as an approach for the identification of new G4-binding small molecules.

Dual mode of cell death upon the photo-irradiation of a RuII polypyridyl complex in interphase or mitosis

Photodynamic therapy (PDT) is an attractive, complementary medical technique to chemotherapy. Among the different photosensitizers (PSs) employed, Ru(ii) polypyridyl complexes were found to be valid substitutes to porphyrin-based or phthalocyanine-based PSs. Here, we confirm that one such complex, namely [Ru(bipy)₂-dppz-7-methoxy][PF₆]₂ (Ru65), which localizes in the nucleus of various cancer and normal cells, displays cytotoxicity only upon UV-A irradiation. Importantly, we disclose the molecular mechanism of the UV-A mediated cytotoxic action of Ru65. We demonstrate that Ru65 intercalates in DNA and, upon light irradiation, promotes guanine oxidation, resulting in nicks in the double helix. We confirm this mechanism of action in living cells, showing that the UV-A irradiation of cells loaded with Ru65 results in a transient DNA damage response and cell death. Strikingly, the photo-irradiation of Ru65 triggered distinct mechanisms of cell death in interphase or mitotic cells. The former underwent cell cycle arrest at the G2/M phase and massive cytoplasmic vacuolation, which was paralleled by an unfolded-protein stress response, resulting in a reduction of viability and cell death through a paraptosis-like mechanism. On the other hand, the UV-A irradiation of Ru65 in cells synchronized by G2/M block-release with a selective CDK1 inhibitor led to blocking mitotic entry and rapid cell death through classic apoptotic pathways. Importantly, targeting mitotic cells with Ru65 allowed increasing its photo-toxicity by a factor of 3.6. Overall, our findings show that the use of a combination of a cell cycle inhibitor and a PS targeting the nucleus could open up new avenues in PDT.

Spatiotemporally photoradiation-controlled intratumoral depot for combination of brachytherapy and photodynamic therapy for solid tumor

In an attempt to spatiotemporally control both tumor retention and the coverage of anticancer agents, we developed a photoradiation-controlled intratumoral depot (PRCITD) driven by convection enhanced delivery (CED). This intratumoral depot consists of recombinant elastin-like polypeptide (ELP) containing periodic cysteine residues and is conjugated with a photosensitizer, chlorin-e6 (Ce6) at the N-terminus of the ELP. We hypothesized that this cysteine-containing ELP (cELP) can be readily crosslinked through disulfide bonds upon exposure to oxidative agents, specifically the singlet oxygen produced during photodynamic stimulation. Upon intratumoral injection, CED drives the distribution of the soluble polypeptide freely throughout the tumor interstitium. Formation and retention of the depot was monitored using fluorescence molecular tomography imaging. When imaging shows that the polypeptide has distributed throughout the entire tumor, 660-nm light is applied externally at the tumor site. This photo-radiation wavelength excites Ce6 and generates reactive oxygen species (ROS) in the presence of oxygen. The ROS induce in situ disulfide crosslinking of the cysteine thiols, stabilizing the ELP biopolymer into a stable therapeutic depot. Our results demonstrate that this ELP design effectively forms a hydrogel both in vitro and in vivo. These depots exhibit high stability in subcutaneous tumor xenografts in nude mice and significantly improved intratumoral retention compared to controls without crosslinking, as seen by fluorescent imaging and iodine-125 radiotracer studies. The photodynamic therapy provided by the PRCITD was found to cause significant tumor inhibition in a Ce6 dose dependent manner. Additionally, the combination of PDT and intratumoral radionuclide therapy co-delivered by PRCITD provided a greater antitumor effect than either monotherapy alone. These results suggest that the PRCITD could provide a stable platform for delivering synergistic, anti-cancer drug depots.

Photodynamic therapy with a novel porphyrin-based photosensitizer against human gastric cancer

The objective of the present study was to evaluate the effects of novel porphyrin-based photosensitizer meso-5-[ρ-diethylene triamine pentaacetic acid- aminophenyl]-10,15,20-triphenyl-porphyrin (DTP)-mediated photodynamic therapy (PDT) on the HGC27 and SNU-1 human gastric cancer cell lines. The absorption spectrum of DTP was analyzed using a microplate spectrophotometer. The HGC27 or SNU-1 cells were incubated with DTP and exposed to illumination by a 650-nm laser. The experiments were divided into four groups: A blank control, cells treated with DTP without light, cells exposed to laser light without DTP and cells treated with a combination of DTP and light together. The phototoxicity of DTP was analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Cell apoptosis was detected by flow cytometry and Hoechst 33342 staining. In addition, the intracellular distribution of DTP was investigated by laser scanning confocal microscopy. DTP-PDT demonstrated marked phototoxicity towards HGC27- and SNU-1 cells. The rate of cell death increased significantly in a DTP concentration-dependent and light dose-dependent manner, with maximum mortality rates of 74.14 and 67.76%, respectively. There were significant differences between the therapeutic and control groups (P<0.01). In addition, the growth of cells treated with DTP or laser light alone was not inhibited. Further evaluation revealed that, following DTP-PDT, HGC27 and SNU-1 cells demonstrated notable apoptotic changes, including condensed chromatin, fragmented nuclei and apoptotic bodies, and the percentage of apoptotic cells was significantly higher than that of the control groups (P<0.01). Furthermore, confocal laser scanning microscopy revealed that DTP localized to the lysosomes but not mitochondria in the two types of tumor cell. In conclusion, significant phototoxicity and reduced cytotoxicity in dark conditions make the novel photosensitizer DTP a promising potential PDT drug for future use in the treatment of human gastric cancer.

Pyrazolo[3,4-h]quinolines promising photosensitizing agents in the treatment of cancer

A new series of pyrazolo[3,4-h]quinolines, heteroanalogues of angelicin was conveniently prepared with a broad substitution pattern. A large number of derivatives was obtained and the cellular photocytotoxicity was evaluated in vitro against 5 different human tumor cell lines with GI50 values reaching the nanomolar level (14.52-0.04 μM). Selected compounds were able to photoinduce a massive cell death with the involvement of mitochondria. Their photodamage cellular targets were proteins and lipids and they did not cause any kind of DNA photodamage. This latter event is of considerable importance in the modulation of long term side effects, generally associated with the use of classical furocoumarins.