An Overview of Potential Natural Photosensitizers in Cancer Photodynamic Therapy

Construction of Photosensitizer Candidates in Photodynamic Therapy: Computer Aided Design, Calculation, and Screening

Thiophene and pyrrole units are extensively utilized in light-responsive materials and have significantly advanced the field of organic photovoltaics (OPV). This progress has inspired our exploration of photosensitizers (PS) for photodynamic therapy (PDT). Currently, traditional PS face limitations in clinical application, including a restricted variety and narrow applicability. Drawing upon molecular design concepts from OPV, we aim to transcend these limitations in PDT. Given the abundance of candidate molecules, effective screening is crucial. Theoretical calculations and electronic structure analyses serve as precise and practical screening methods. In this study, we adopted strategies successfully employed in OPV molecular design, focusing on donor-acceptor (D-A) and acceptor-donor-acceptor (A-D-A) structures. Using density functional theory (DFT) and time-dependent density functional theory (TDDFT), we systematically designed combinations of promising organic fragments. These fragments include polythiophene and polypyrrole-dominated donor structures, paired with five electron acceptors: indene (Ind), diketopyrrole (DPP), naphthalimide (Ni), benzothiazole (Btd), and dithiazolyl diketopyrrole (Tbo). Through meticulous calculations, we obtained electronic structures and spectral properties for all candidate molecules, facilitating an efficient screening process. Our findings highlight that those combinations of polypyrrole-based frameworks with DPP, Ni, and Btd show significant promise for PS applications. Approximately 13% of candidates were selected through comprehensive comparison, markedly reducing molecular design time and experimental costs. This interdisciplinary approach holds potential to pave the way for more targeted and successful PS designs.

Development of optical microneedle-lens array for photodynamic therapy

Recently, photodynamic therapy (PDT) which involves a photosensitizer (PS), a special drug activated by light, and light irradiation has been widely used in treating various skin diseases such as port-wine stain as well as cancers such as melanoma and non-melanoma skin cancers. PDT comprises two general steps: the introduction of PS into the body or a specific spot to be treated, and the irradiation process using a light source with a specific wavelength to excite the PS. Although PDT is gaining great attention owing to its potential as a targeted approach in the treatment of skin cancers, several limitations still exist for practical use. One of the biggest challenges is the limited penetration of light owing to scattering, reflection, and absorption of light inside the skin layers. In addition, accidental light exposure of the target area causes additional cellular damage, which causes unexpected complications. To solve these issues, we introduced an optical microneedle-lens array (OMLA) to improve the efficiency and safety of PDT treatment. We designed and fabricated a novel optical microneedle-lens array with controlled dimensions to optimize light transmission. In addition, PS was coated uniformly over the tips of the OMLA using the dip coating method. Finally, we confirmed that the PS coated on the OMLA was released into the target area and subsequently generated radical oxygen by light irradiation. We expect that our proposed OMLA for PDT treatment can realize a new light-transmission platform optimized for PDT with targeting various types of skin cancers.

Recent advances in self-targeting natural product-based nanomedicines

Natural products, recognized for their potential in disease prevention and treatment, have been integrated with advanced nano-delivery systems to create natural product-based nanomedicines, offering innovative approaches for various diseases. Natural products derived from traditional Chinese medicine have their own targeting effect and remarkable therapeutic effect on many diseases, but there are some shortcomings such as poor physical and chemical properties. The construction of nanomedicines using the active ingredients of natural products has become a key step in the modernization research process, which could be used to make up for the defects of natural products such as low solubility, large dosage, poor bioavailability and poor targeting. Nanotechnology enhances the safety, selectivity, and efficacy of natural products, positioning natural product-based nanomedicines as promising candidates in medicine. This review outlines the current status of development, the application in different diseases, and safety evaluation of natural product-based nanomedicines, providing essential insights for further exploration of the synergy between natural products and nano-delivery systems in disease treatment.

In Vitro Anticancer Effects of Aqueous Leaf Extract from Nepeta nuda L. ssp. nuda

Despite significant efforts, cancer remains the second leading cause of mortality worldwide. The medicinal plant Nepeta nuda L. represents a valuable source of biologically active compounds with pharmacological activities including antioxidant, anti-inflammatory, antimicrobial, and antiviral. This study aimed to assess the antiproliferative potential and mechanisms of action of aqueous extract from the leaves of wild-grown N. nuda. Cancer cell lines, MDA-MB-231, MCF7 (breast), HT29, Colon 26 (colon), and HepG2 (liver cancer), and a non-cancerous skin cell line, BJ, were assessed for antiproliferative activity by MTT assay and observation of cell morphological alterations. The cancer cell line that was most sensitive to the extract was further studied for apoptotic alterations by Annexin V/propidium iodide staining, colony-forming assay, and qRT-PCR analysis. The results revealed that the plant extract inhibited the proliferation of all investigated cancer cell lines with the strongest cytostatic effect on Colon 26 cells with a half maximal inhibitory concentration (IC50) value of 380.2 μg/mL and a selectivity index (SI) of 3.5. The extract significantly inhibited the ability of cells to form colonies, exhibited considerable proapoptotic potential involving the participation of the CASP8 gene, and increased the expression levels of ATG3 and the BECN1 gene, which suggests a role of autophagic cell death in the antitumor action.

Photoactivated Anticancer Activity of Cobalt(III) Complexes with Naturally Occurring Flavonoids Chrysin and Silibinin

Photoactive metal complexes of bioessential transition metal ions with natural chelators are gaining interest as photocytotoxic agents for cancer photodynamic therapy (PDT). We report six new cobalt(III) complexes with a mixed-ligand formulation [Co(B)2(L)](ClO4)2 (Co1-Co6), where B represents a N,N-donor α-diimine ligand, namely, phenanthroline (phen; Co1, Co2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq; Co3, Co4), and dipyrido[3,2-a:2',3'-c]phenazine (dppz; Co5, Co6), and L is the monoanionic form of the naturally occurring flavonoids chrysin (chry; Co1, Co3, Co5) and silibinin (sili; Co2, Co4, Co6). Complexes displayed a d-d absorption band within 500-700 nm and exhibited excellent dark and photostability in solution. Cytotoxicity studies indicated significant activity of Co5 and Co6 against cervical (HeLa) and lung (A549) cancer cells under visible light (400-700 nm) irradiation giving low micromolar IC50 values (2.3-3.4 μM, phototoxicity index~15-30). The complexes demonstrated notably low toxicity against normal HPL1D lung epithelial cells. Flow cytometry assay revealed an apoptotic mode of cell damage triggered by the complexes when irradiated. ROS generation assay indicated the involvement of singlet oxygen species in the cell death mechanism when irradiated with light. Overall, complexes Co5 and Co6 with coordinated dipyridophenazine and flavonoid ligands are potential candidates for cancer PDT applications.

Functionalized and Theranostic Lipidic and Tocosomal Drug Delivery Systems: Potentials and Limitations in Cancer Photodynamic Therapy

Photodynamic therapy (PDT) is a multidisciplinary area, which involves photophysics and photochemical sciences and plays an important role in cancer diagnosis and treatment. PDT involves a photo-activable drug called photosensitizer (PS), a specific wavelength of light and cellular compounds to produce toxic oxygen species in a much-localized way to destroy malignant tumors. Despite the various benefits of PDT, some PS-related limitations hinder its use as an ideal treatment option for cancer. To address these limitations (e.g., poor bioavailability, weak permeability, hydrophobicity, and aggregation), lipid-based and vesicular drug delivery systems have been employed. These carrier systems possess the ability to enhance the bioavailability, permeability, and solubility of the drug. Furthermore, they tend to load hydrophobic and lipophilic compounds and can be employed for an efficient and targeted drug delivery. The purpose of this review is to highlight the precise idea of PDT, the limitations of PDT related to PS, and the application of lipidic and tocosomal carriers in PDT for the treatment of various types of cancers. Liposomes, nanoliposomes, solid lipid nanoparticles, vesicular phospholipid gels, exosomes, transferosomes, and tocosomes are presented as commonly-employed vesicular drug carriers. Moreover, the amalgamation of cell-based drug delivery systems (CBDDS) with PDT holds considerable potential as an encouraging avenue in cancer treatment, especially in the context of immunotherapy.

Visible light triggers the formation of reactive oxygen species in monoclonal antibody formulations

Most monoclonal antibody formulations require the presence of a surfactant, such as polysorbate, to ensure protein stability. The presence of high concentrations of polysorbate have been shown to enhance photooxidation of certain protein drug products when exposed to visible light. The current literature, however, suggest that photooxidation of polysorbate only occurs when exposed to visible light in combination with UVA light. This is probable as peroxides present in polysorbate solutions can be cleaved homolytically in the UVA region. In the visible region, photooxidation is not expected to occur as cleavage of peroxides is not expected at these wavelengths. This report presents findings suggesting that the presence of one or more photosensitiser(s) in polysorbate must be a cause and is required to catalyse the aerobic oxidation of polysorbate solutions upon exposure to visible light. Our investigation aimed to clarify the mechanism(s) of polysorbate photooxidation and explore the kinetics and the identity of the generated radicals and their impact on monoclonal antibody (mAb) degradation. Our study reveals that when polysorbate solutions are exposed to visible light between 400 - 800 nm in the absence of proteins, discolouration, radical formation, and oxygen depletion occur. We discuss the initial formation of reactive species, most likely occurring directly after reaction of molecular oxygen, with the presence of a triplet state photosensitiser, which is generated by intersystem crossing of the excited singlet state. When comparing the photooxidation of PS20 and PS80 in varying quality grades, we propose that singlet oxygen possesses potential for reacting with unsaturated fatty acids in PS80HP, however, PS20HP itself exhibited no measurable oxidation under the tested conditions. The study's final part delves into the photooxidation behaviour of different PS grades, examining its influence on the integrity of a mAb in the formulation. Finally, we examined the effect of photooxidation on the integrity of monoclonal antibodies. Our findings show that the exposure to visible light in polysorbate-containing mAb solutions at high PS concentrations of 4 mg·ml-1 results in increased monoclonal antibody degradation, highlighting the need for cautious evaluation of the correct PS concentration to stabilise protein therapeutics.

Inorganic nanoparticle-based treatment approaches for colorectal cancer: recent advancements and challenges

Colorectal cancer, the third most prevalent cancer globally, contributes significantly to mortality rates, with over 1.9 million reported cases and nearly 935,000 fatalities annually. Surgical resection is a primary approach for localized colorectal tumors, with adjunct therapies like chemotherapy, radiotherapy, and targeted/immunotherapy considered depending on the tumor stage. However, despite preferences for targeted and immunotherapy post-surgery, chemotherapy remains commonly chosen due to its lower cost and high cancer-killing efficiency. Yet, chemotherapy faces issues such as tumor resistance and severe side effects. Nanotechnology has emerged in cancer therapy by alleviating the drawbacks of current treatment approaches. In the past few decades, inorganic nanoparticles have shown promise in combating colorectal cancer, offering advantages over conventional chemotherapy. Compared to organic nanoparticles, inorganic nanoparticles exhibit properties like photosensitivity, conductivity, magnetic allure, and thermal proficiency, allowing them to function as both drug carriers and therapeutic agents. Derived primarily from carbon, silica, metals, and metal oxides, they offer superior drug-loading capacity, heightened quantum yield, and participation in advanced photothermal and photodynamic therapies. This review provides a brief overview of the pathophysiology of colorectal cancer and the pivotal role of inorganic nanoparticles in photothermal therapy photodynamic therapy, and drug delivery. Additionally, it discusses numerous inorganic nanoparticles in colorectal cancer therapy based on recent literature.

Editorial to the Special Issue "Theranostic Drug Delivery: Prospects and Problems"

The technical phrase theragnostic (also known as theranostic) was first introduced to the scientific community in the year 1998 by John Funkhouser, to describe a methodology or procedure employed to achieve disease diagnosis and treatment simultaneously [...].

Hypericin-mediated photodynamic therapy inhibits metastasis and EMT of colorectal cancer cells by regulating RhoA-ROCK1 signaling pathway

Colorectal cancer (CRC) is significantly contributed to global cancer mortality rates. Treating CRC is particularly challenging due to metastasis and drug resistance. There is a pressing need for new treatment strategies against metastatic CRC. Photodynamic therapy (PDT) offers a well-established, minimally invasive treatment option for cancer with limited side effects. Hypericin (HYP), a potent photosensitizer for PDT, has been documented to induce cytotoxicity and apoptosis in various types of cancers. However, there are few reports on the inhibitory effects of HYP-mediated PDT on the metastatic ability of CRC cells. Here, we evaluate the inhibitory effects of HYP-mediated PDT against metastatic CRC cells and define its underlying mechanisms. Wound-healing and Transwell assays show that HYP-mediated PDT suppresses migration and invasion of CRC cells. F-actin visualization assays indicate HYP-mediated PDT decreases F-actin formation in CRC cells. TEM assays reveal HYP-mediated PDT disrupts pseudopodia formation of CRC cells. Mechanistically, immunofluorescence and western blotting results show that HYP-mediated PDT upregulates E-cadherin and downregulates N-cadherin and Vimentin. HYP-mediated PDT also suppresses key EMT regulators, including Snail, MMP9, ZEB1 and α-SMA. Additionally, the expressions of RhoA and ROCK1 are downregulated by HYP-mediated PDT. Together, these findings suggest that HYP-mediated PDT inhibits the migration and invasion of HCT116 and SW620 cells by modulating EMT and RhoA-ROCK1 signaling pathway. Thus, HYP-mediated PDT presents a potential therapeutic option for CRC.

Chromophore-Assisted Light Inactivation for Protein Degradation and Its Application in Biomedicine

The functional investigation of proteins holds immense significance in unraveling physiological and pathological mechanisms of organisms as well as advancing the development of novel pharmaceuticals in biomedicine. However, the study of cellular protein function using conventional genetic manipulation methods may yield unpredictable outcomes and erroneous conclusions. Therefore, precise modulation of protein activity within cells holds immense significance in the realm of biomedical research. Chromophore-assisted light inactivation (CALI) is a technique that labels photosensitizers onto target proteins and induces the production of reactive oxygen species through light control to achieve precise inactivation of target proteins. Based on the type and characteristics of photosensitizers, different excitation light sources and labeling methods are selected. For instance, KillerRed forms a fusion protein with the target protein through genetic engineering for labeling and inactivates the target protein via light activation. CALI is presently predominantly employed in diverse biomedical domains encompassing investigations into protein functionality and interaction, intercellular signal transduction research, as well as cancer exploration and therapy. With the continuous advancement of CALI technology, it is anticipated to emerge as a formidable instrument in the realm of life sciences, yielding more captivating outcomes for fundamental life sciences and precise disease diagnosis and treatment.

BODIPY precursors and their cyclotriphosphazene Derivatives: Synthesis, photochemical properties and their application in PDT

Photodynamic therapy (PDT) is a treatment method consisting of common combination of oxygen, light energy and a light absorbing molecule called a photosensitizer. In this work, four new compounds consisting of BODIPY precursors and BODIPY-cyclotriphosphazene derivatives were synthesized to investigate the PDT effects. The chemical structures of the compounds were characterized and then their photophysical properties were determined by spectroscopic techniques. The precursor BODIPYs and their cyclotriphosphazene derivatives exhibited similar properties such as strong absorption intensity, high photostability and low fluorescence profile in the NIR region. Additionally, the singlet oxygen production capacities of these compounds were determined using the photobleaching technique of 1,3-diphenylisobenzofuran (DPBF) under light illumination. By introducing iodine atoms into the molecule, which are responsible for the intersystem transition (ISC) enhancement, a more efficient singlet oxygen production was achieved in both the iodinated-BODIPY and its cyclotriphosphazene derivative. Anticancer activities of the precursor BODIPYs and their cyclotriphosphazene derivatives in the absence and presence of light illumination were evaluated on cancerous cell lines (PC3 and DU145) and non-tumorigenic prostate epithelial PNT1a cell. The compounds triggered the death of cancer cell PC3 the more significantly in the presence of red light compared to the healthy cells (PNT1a).

New Avenues and Major Achievements in Phytocompounds Research for Glioblastoma Therapy

Phytocompounds have been evaluated for their anti-glioblastoma actions for decades, with promising results from preclinical studies but only limited translation into clinics. Indeed, by targeting multiple signaling pathways deregulated in cancer, they often show high efficacy in the in vitro studies, but their poor bioavailability, low tumor accumulation, and rapid clearance compromise their efficacy in vivo. Here, we present the new avenues in phytocompound research for the improvement of glioblastoma therapy, including the ways to enhance the response to temozolomide using phytochemicals, the current focus on phytocompound-based immunotherapy, or the use of phytocompounds as photosensitizers in photodynamic therapy. Moreover, we present new, intensively evaluated approaches, such as chemical modifications of phytochemicals or encapsulation into numerous types of nanoformulations, to improve their bioavailability and delivery to the brain. Finally, we present the clinical trials evaluating the role of phytocompounds or phytocompound-derived drugs in glioblastoma therapy and the less studied phytocompounds or plant extracts that have only recently been found to possess promising anti-glioblastoma properties. Overall, recent advancements in phytocompound research are encouraging; however, only with more 3D glioblastoma models, in vivo studies, and clinical trials it is possible to upgrade the role of phytocompounds in glioblastoma treatment to a satisfactory level.

Analysis of Self-Assembled Low- and High-Molecular-Weight Poly-L-Lysine-Ce6 Conjugate-Based Nanoparticles

In cancer therapy, photodynamic therapy (PDT) has attracted significant attention due to its high potential for tumor-selective treatment. However, PDT agents often exhibit poor physicochemical properties, including solubility, necessitating the development of nanoformulations. In this study, we developed two cationic peptide-based self-assembled nanomaterials by using a PDT agent, chlorin e6 (Ce6). To manufacture biocompatible nanoparticles based on peptides, we used the cationic poly-L-lysine peptide, which is rich in primary amines. We prepared low- and high-molecular-weight poly-L-lysine, and then evaluated the formation and performance of nanoparticles after chemical conjugation with Ce6. The results showed that both molecules formed self-assembled nanoparticles by themselves in saline. Interestingly, the high-molecular-weight poly-L-lysine and Ce6 conjugates (HPLCe6) exhibited better self-assembly and PDT performance than low-molecular-weight poly-L-lysine and Ce6 conjugates (LPLCe6). Moreover, the HPLCe6 conjugates showed superior cellular uptake and exhibited stronger cytotoxicity in cell toxicity experiments. Therefore, it is functionally beneficial to use high-molecular-weight poly-L-lysine in the manufacturing of poly-L-lysine-based self-assembling biocompatible PDT nanoconjugates.

The Use of Photoactive Polymeric Nanoparticles and Nanofibers to Generate a Photodynamic-Mediated Antimicrobial Effect, with a Special Emphasis on Chronic Wounds

This review is concerned with chronic wounds, with an emphasis on biofilm and its complicated management process. The basics of antimicrobial photodynamic therapy (PDT) and its underlying mechanisms for microbial eradication are presented. Intrinsically active nanocarriers (polydopamine NPs, chitosan NPs, and polymeric micelles) that can further potentiate the antimicrobial photodynamic effect are discussed. This review also delves into the role of photoactive electrospun nanofibers, either in their eluting or non-eluting mode of action, in microbial eradication and accelerating the healing of wounds. Synergic strategies to augment the PDT-mediated effect of photoactive nanofibers are reviewed.

Tumor-Associated Macrophage Targeting of Nanomedicines in Cancer Therapy

The tumor microenvironment (TME) is pivotal in tumor growth and metastasis, aligning with the "Seed and Soil" theory. Within the TME, tumor-associated macrophages (TAMs) play a central role, profoundly influencing tumor progression. Strategies targeting TAMs have surfaced as potential therapeutic avenues, encompassing interventions to block TAM recruitment, eliminate TAMs, reprogram M2 TAMs, or bolster their phagocytic capabilities via specific pathways. Nanomaterials including inorganic materials, organic materials for small molecules and large molecules stand at the forefront, presenting significant opportunities for precise targeting and modulation of TAMs to enhance therapeutic efficacy in cancer treatment. This review provides an overview of the progress in designing nanoparticles for interacting with and influencing the TAMs as a significant strategy in cancer therapy. This comprehensive review presents the role of TAMs in the TME and various targeting strategies as a promising frontier in the ever-evolving field of cancer therapy. The current trends and challenges associated with TAM-based therapy in cancer are presented.

Biological function, regulatory mechanism, and clinical application of mannose in cancer

Studies examining the regulatory roles and clinical applications of monosaccharides other than glucose in cancer have been neglected. Mannose, a common type of monosaccharide found in human body fluids and tissues, primarily functions in protein glycosylation rather than carbohydrate metabolism. Recent research has demonstrated direct anticancer effects of mannose in vitro and in vivo. Simply supplementing cell culture medium or drinking water with mannose achieved these effects. Moreover, mannose enhances the effectiveness of current cancer treatments including chemotherapy, radiotherapy, targeted therapy, and immune therapy. Besides the advancements in basic research on the anticancer effects of mannose, recent studies have reported its application as a biomarker for cancer or in the delivery of anticancer drugs using mannose-modified drug delivery systems. This review discusses the progress made in understanding the regulatory roles of mannose in cancer progression, the mechanisms underlying its anticancer effects, and its current application in cancer diagnosis and treatment.

Natural photosensitizers potentiate the targeted antimicrobial photodynamic therapy as the Monkeypox virus entry inhibitors: An in silico approach

BACKGROUND

Monkeypox is a viral zoonotic disease that has emerged as a threat to public health. Currently, there is no treatment approved specifically targeting Monkeypox disease. Hence, it is essential to identify and develop therapeutic approaches to the Monkeypox virus. In the current in silico paper, we comprehensively involve using computer simulations and modeling to insights and predict hypotheses on the potential of natural photosensitizers-mediated targeted antimicrobial photodynamic therapy (aPDT) against D8L as a Monkeypox virus protein involved in viral cell entry.

MATERIALS AND METHODS

In the current study, computational techniques such as molecular docking were combined with in silico ADMET predictions to examine how Curcumin (Cur), Quercetin (Qct), and Riboflavin (Rib) as the natural photosensitizers bind to the D8L protein in Monkeypox virus, as well as to determine pharmacokinetic properties of these photosensitizers.

RESULTS

The three-dimensional structure of the D8L protein in the Monkeypox virus was constructed using homology modeling (PDB ID: 4E9O). According to the physicochemical properties and functional characterization, 4E9O was a stable protein with the nature of a hydrophilic structure. The docking studies employing a three-dimensional model of 4E9O with natural photosensitizers exhibited good binding affinity. D8L protein illustrated the best docking score (-7.6 kcal/mol) in relation to the Rib and displayed good docking scores in relation to the Cur (-7.0 kcal/mol) and Qct (-7.5 kcal/mol).

CONCLUSIONS

The findings revealed that all three photosensitizers were found to obey the criteria of Lipinski's rule of five and displayed drug-likeness. Moreover, all the tested photosensitizers were found to be non-hepatotoxic and non-cytotoxic. In summary, our investigation identified Cur, Qct, and Rib could efficiently interact with D8L protein with a strong binding affinity. It can be concluded that aPDT using these natural photosensitizers may be considered an adjuvant treatment against Monkeypox disease.

Emerging Applications of Chlorella sp. and Spirulina (Arthrospira) sp

Chlorella sp. and Spirulina (Arthrospira) sp. account for over 90% of the global microalgal biomass production and represent one of the most promising aquiculture bioeconomy systems. These microorganisms have been widely recognized for their nutritional and therapeutic properties; therefore, a significant growth of their market is expected, especially in the nutraceutical, food, and beverage segments. However, recent advancements in biotechnology and environmental science have led to the emergence of new applications for these microorganisms. This paper aims to explore these innovative applications, while shedding light on their roles in sustainable development, health, and industry. From this state-of-the art review, it was possible to give an in-depth outlook on the environmental sustainability of Chlorella sp. and Spirulina (Arthrospira) sp. For instance, there have been a variety of studies reported on the use of these two microorganisms for wastewater treatment and biofuel production, contributing to climate change mitigation efforts. Moreover, in the health sector, the richness of these microalgae in photosynthetic pigments and bioactive compounds, along with their oxygen-releasing capacity, are being harnessed in the development of new drugs, wound-healing dressings, photosensitizers for photodynamic therapy, tissue engineering, and anticancer treatments. Furthermore, in the industrial sector, Chlorella sp. and Spirulina (Arthrospira) sp. are being used in the production of biopolymers, fuel cells, and photovoltaic technologies. These innovative applications might bring different outlets for microalgae valorization, enhancing their potential, since the microalgae sector presents issues such as the high production costs. Thus, further research is highly needed to fully explore their benefits and potential applications in various sectors.

Photodynamic Therapy: From the Basics to the Current Progress of N-Heterocyclic-Bearing Dyes as Effective Photosensitizers

Photodynamic therapy, an alternative that has gained weight and popularity compared to current conventional therapies in the treatment of cancer, is a minimally invasive therapeutic strategy that generally results from the simultaneous action of three factors: a molecule with high sensitivity to light, the photosensitizer, molecular oxygen in the triplet state, and light energy. There is much to be said about each of these three elements; however, the efficacy of the photosensitizer is the most determining factor for the success of this therapeutic modality. Porphyrins, chlorins, phthalocyanines, boron-dipyrromethenes, and cyanines are some of the N-heterocycle-bearing dyes' classes with high biological promise. In this review, a concise approach is taken to these and other families of potential photosensitizers and the molecular modifications that have recently appeared in the literature within the scope of their photodynamic application, as well as how these compounds and their formulations may eventually overcome the deficiencies of the molecules currently clinically used and revolutionize the therapies to eradicate or delay the growth of tumor cells.

Shining a Light on Prostate Cancer: Photodynamic Therapy and Combination Approaches

Prostate cancer is a major health concern worldwide, and current treatments, such as surgery, radiation therapy, and chemotherapy, are associated with significant side effects and limitations. Photodynamic therapy (PDT) is a promising alternative that has the potential to provide a minimally invasive and highly targeted approach to treating prostate cancer. PDT involves the use of photosensitizers (PSs) that are activated by light to produce reactive oxygen species (ROS), which can induce tumor cell death. There are two main types of PSs: synthetic and natural. Synthetic PSs are classified into four generations based on their structural and photophysical properties, while natural PSs are derived from plant and bacterial sources. Combining PDT with other therapies, such as photothermal therapy (PTT), photoimmunotherapy (PIT), and chemotherapy (CT), is also being explored as a way to improve its efficacy. This review provides an overview of conventional treatments for prostate cancer, the underlying principles of PDT, and the different types of PSs used in PDT as well as ongoing clinical studies. It also discusses the various forms of combination therapy being explored in the context of PDT for prostate cancer, as well as the challenges and opportunities associated with this approach. Overall, PDT has the potential to provide a more effective and less invasive treatment option for prostate cancer, and ongoing research is aimed at improving its selectivity and efficacy in clinical settings.

Biological Action of Singlet Molecular Oxygen from the Standpoint of Cell Signaling, Injury and Death

Energy transfer to ground state triplet molecular oxygen results in the generation of singlet molecular oxygen (¹O₂), which has potent oxidizing ability. Irradiation of light, notably ultraviolet A, to a photosensitizing molecule results in the generation of ¹O₂, which is thought to play a role in causing skin damage and aging. It should also be noted that ¹O₂ is a dominant tumoricidal component that is generated during the photodynamic therapy (PDT). While type II photodynamic action generates not only ¹O₂ but also other reactive species, endoperoxides release pure ¹O₂ upon mild exposure to heat and, hence, are considered to be beneficial compounds for research purposes. Concerning target molecules, ¹O₂ preferentially reacts with unsaturated fatty acids to produce lipid peroxidation. Enzymes that contain a reactive cysteine group at the catalytic center are vulnerable to ¹O₂ exposure. Guanine base in nucleic acids is also susceptible to oxidative modification, and cells carrying DNA with oxidized guanine units may experience mutations. Since ¹O₂ is produced in various physiological reactions in addition to photodynamic reactions, overcoming technical challenges related to its detection and methods used for its generation would allow its potential functions in biological systems to be better understood.

Photoresponsive Inorganic Nanomaterials in Oncology

The diagnosis and treatment of cancer are continuously evolving in search of more efficient, safe, and personalized approaches. Therapies based on nanoparticles or physical stimuli-responsive substances have shown great potential to overcome the inherent shortcomings of conventional cancer therapies. In fact, nanoparticles may increase the half-life of chemotherapeutic agents or promote the targeting in cancer tissues while physical stimuli-responsive substances are more effective and safer with respect to traditional chemotherapeutic agents because of the possibility to be switched on only when needed. These 2 approaches can be combined by exploiting the ability of some inorganic nanomaterials to be activated by light, ultrasounds, magnetic fields, or ionizing radiations. Albeit the development of stimuli-responsive materials is still at the early stages, research in this field is rapidly growing since they have important advantages with respect to organic nanoparticles or molecular substances, like higher stability, and higher efficiency in converting the stimulus in heat or, in some cases, reactive oxygen species. On the other hand, the translation process is slowed down by issues related to safety and quality of the formulations. This literature review summarizes the current advancements in this research field, analysing the most promising materials and applications.