Mechanisms in photodynamic therapy: part one-photosensitizers, photochemistry and cellular localization

Lima K, Alves de Matos P, Tsubone TM, Gonçalves RR, Ferrari JL. Upconversion rare Earths nanomaterials applied to photodynamic therapy and bioimaging

Light-based therapies and diagnoses including photodynamic therapy (PDT) have been used in many fields of medicine, including the treatment of non-oncological diseases and many types of cancer. PDT require a light source and a light-sensitive compound, called photosensitizer (PS), to detect and destroy cancer cells. After absorption of the photon, PS molecule gets excited from its singlet ground state to a higher electronically excited state which, among several photophysical processes, can emit light (fluorescence) and/or generate reactive oxygen species (ROS). Moreover, the biological responses are activated only in specific areas of the tissue that have been submitted to exposure to light. The success of the PDT depends on many parameters, such as deep light penetration on tissue, higher PS uptake by undesired cells as well as its photophysical and photochemical characteristics. One of the challenges of PDT is the depth of penetration of light into biological tissues. Because photon absorption and scattering occur simultaneously, these processes depend directly on the light wavelength. Using PS that absorbs photons on "optical transparency windows" of biological tissues promises deeper penetration and less attenuation during the irradiation process. The traditional PS normally is excited by a higher energy photon (UV-Vis light) which has become the Achilles' heel in photodiagnosis and phototreatment of deep-seated tumors below the skin. Thus, the need to have an effective upconverter sensitizer agent is the property in which it absorbs light in the near-infrared (NIR) region and emits in the visible and NIR spectral regions. The red emission can contribute to the therapy and the green and NIR emission to obtain the image, for example. The absorption of NIR light by the material is very interesting because it allows greater penetration depth for in vivo bioimaging and can efficiently suppress autofluorescence and light scattering. Consequently, the penetration of NIR radiation is greater, activating the biophotoluminescent material within the cell. Thus, materials containing Rare Earth (RE) elements have a great advantage for these applications due to their attractive optical and physicochemical properties, such as several possibilities of excitation wavelengths - from UV to NIR, strong photoluminescence emissions, relatively long luminescence decay lifetimes (µs to ms), and high sensitivity and easy preparation. In resume, the relentless search for new systems continues. The contribution and understanding of the mechanisms of the various physicochemical properties presented by this system is critical to finding a suitable system for cancer treatment via PDT.

Advancements in photodynamic therapy of esophageal cancer

The poor prognosis of patients with esophageal cancer leads to the constant search for new ways of treatment of this disease. One of the methods used in high-grade dysplasia, superficial invasive carcinoma, and sometimes palliative care is photodynamic therapy (PDT). This method has come a long way from the first experimental studies to registration in the treatment of esophageal cancer and is constantly being improved and refined. This review describes esophageal cancer, current treatment methods, the introduction to PDT, the photosensitizers (PSs) used in esophageal carcinoma PDT, PDT in squamous cell carcinoma (SCC) of the esophagus, and PDT in invasive adenocarcinoma of the esophagus. For this review, research and review articles from PubMed and Web of Science databases were used. The keywords used were "photodynamic therapy in esophageal cancer" in the years 2000-2020. The total number of papers returned was 1,000. After the review was divided into topic blocks and the searched publications were analyzed, 117 articles were selected.

5-Aminolevulinic Acid-Mediated Photodynamic Therapy Potentiates the Effectiveness of Doxorubicin in Ewing Sarcomas

Ewing sarcomas (ES) are aggressive primary bone tumors that require radical therapy. Promising low toxicity, 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) could enhance the effectiveness of conventional treatment modalities (e.g., doxorubicin (DOX)), improving, thus, the anti-tumorigenic effects. In this study, we investigated the effects of DOX and 5-ALA PDT alone or in combination on three different human ES cell lines. Cell viability, reactive oxygen species (ROS) production, and cellular stiffness were measured 24 h after PDT (blue light-wavelength 436 nm with 5-ALA) with or without DOX. ES cell lines have a different sensitivity to the same doses and exposure of 5-ALA PDT. DOX in combination with 5-ALA PDT was found to be effective in impairing the viability of all ES cells while also increasing cytotoxic activity by high ROS production. The stiffness of the ES cells increased significantly (p < 0.05) post treatment. Overall, our results showed that across multiple ES cell lines, 5-ALA PDT can successfully and safely be combined with DOX to potentiate the therapeutic effect. The 5-ALA PDT has the potential to be a highly effective treatment when used alone or in conjunction with other treatments. More research is needed to assess the effectiveness of 5-ALA PDT in in vivo settings.

Advancements in Polymeric Nanocarriers to Mediate Targeted Therapy against Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a destructive disease with a poor prognosis, low survival rate and high rate of metastasis. It comprises 15% of total breast cancers and is marked by deficiency of three important receptor expressions, i.e., progesterone, estrogen, and human epidermal growth factor receptors. This absence of receptors is the foremost cause of current TNBC therapy failure, resulting in poor therapeutic response in patients. Polymeric nanoparticles are gaining much popularity for transporting chemotherapeutics, genes, and small-interfering RNAs. Due to their exclusive properties such as great stability, easy surface modification, stimuli-responsive and controlled drug release, ability to condense more than one therapeutic moiety inside, tumor-specific delivery of payload, enhanced permeation and retention effect, present them as ideal nanocarriers for increasing efficacy, bioavailability and reducing the toxicity of therapeutic agents. They can even be used as theragnostic agents for the diagnosis of TNBC along with its treatment. In this review, we discuss the limitations of already existing TNBC therapies and highlight the novel approach to designing and the functionalization of polymeric nanocarriers for the effective treatment of TNBC.

Target Prediction of 5,10,15,20-Tetrakis(4'-Sulfonatophenyl)-Porphyrin Using Molecular Docking

Photodynamic therapy has the potential to be a new and effective cancer treatment. Even if in vitro and in vivo research show promise, the molecular mechanism remains unclear. In this study, molecular docking simulations predict the binding affinity of the 5,10,15,20-tetrakis(4'-sulfonatophenyl)-porphyrin tetraammonium photosensitizer on several potential targets in photodynamic treatment. Our results indicate that this photosensitizer binds to several receptor targets, including B-cell lymphoma 2 (BCL-2) and other related proteins BCL-xL, MCL-1, or A1. The binding affinity of the porphyrin derivative with human serum albumin was determined using UV-vis absorption spectroscopy and predicted using molecular docking. We conclude that the studied porphyrin photosensitizer binds to human serum albumin and may inhibit the cancer cell line through its interactions with HIS and MET AA residues from BCL-2, MCL-1, and β-catenin receptors or through its low estimated free energy of binding when interacting with A1 and BCL-B receptors.

MOF(Fe)-derived composites as a unique nanoplatform for chemo-photodynamic tumor therapy

Fe-based metal-organic frameworks (MOFs) can be used for chemodynamic therapy (CDT) for tumors due to their unique Fenton-like effects and porous and biodegradable nature. The adsorption and transport of small molecule drugs by their structure has attracted much attention. Herein, MnO₂@NH₂-MIL101(Fe)@Ce6-F127 nanoparticles (MNMCF NPs) were synthesized using a facile solvothermal strategy. The small molecule photosensitizer Ce6 was adsorbed by MOFs to improve the biocompatibility of Ce6 and give it high bioavailability when injected intravenously. When the MNMCF NPs reached the tumor site, Fe-based MOFs exhibited Fenton-like properties, producing ˙OH and showing CDT effects. MnO₂ could specifically respond to produce O₂ in a tumor microenvironment, thereby improving the tumor hypoxia state and enhancing the efficacy of photodynamic therapy (PDT) by Ce6. Both the in vitro and in vivo experiments showed that the MNMCF-guided CDT/PDT combination therapy could effectively ablate tumors without the drawbacks of poor tolerability and potential long-term side effects. Therefore, the prepared MNMCF NPs can be used as promising candidates for synergistic CDT/PDT tumor therapy.

Spin-Coating-Based Facile Annular Photodynamic Intraocular Lens Fabrication for Efficient and Safer Posterior Capsular Opacification Prevention

Posterior capsular opacification (PCO) is the most common complication after cataract surgery, which is primarily caused by the proliferation of the residual lens epithelial cells (LECs) in the lens capsule. Previous studies have demonstrated that a drug-eluting intraocular lens (IOL), aimed to in situ eliminate LECs, are an effective and promising way to prevent PCO. However, because of the potential toxicities of the antiproliferative drugs to the adjacent tissues, the safety of such drug-eluting IOLs is still a highly important issue to be solved. In this investigation, a facile photodynamic coating-modified IOL was developed for effective and safer PCO prevention. An annular poly(lactide-co-glycolic acid) (PLGA) coating loaded with photosensitizer chlorin e6 (Ce6) was prepared by a spin-coating technique. The optical property investigations showed that the Ce6@PLGA coating was particularly suitable for the IOL surface modification. The in vitro cell culture investigation showed that Ce6@PLGA coating-modified IOLs effectively eliminated LECs when treated with light illumination, whereas it appeared to have good cytocompatibility without irradiation. The investigation of the cell elimination mechanism showed that the apoptosis of HLECs may be associated with the cytomembrane disruption induced by ROS, which is generated by the photodynamic coating during light illumination. The in vivo implantation experiments confirmed the desired PCO prevention effect, as well as the safety to and biocompatibility with the surrounding tissues. Thus, the facile Ce6@PLGA coating will provide an effective yet safe alternative of IOL surface modification for PCO prevention.

Highly Charged Ru(II) Polypyridyl Complexes as Photosensitizer Agents in Photodynamic Therapy of Epithelial Ovarian Cancer Cells

Ovarian cancer recurrence is frequent and associated with chemoresistance, leading to extremely poor prognosis. Herein, we explored the potential anti-cancer effect of a series of highly charged Ru(II)-polypyridyl complexes as photosensitizers in photodynamic therapy (PDT), which were able to efficiently sensitize the formation of singlet oxygen upon irradiation (Ru12+ and Ru22+) and to produce reactive oxygen species (ROS) in their corresponding dinuclear metal complexes with the Fenton active Cu(II) ion/s ([CuRu1]4+ and [Cu2Ru2]6+). Their cytotoxic and anti-tumor effects were evaluated on human ovarian cancer A2780 cells both in the absence or presence of photoirradiation, respectively. All the compounds tested were well tolerated under dark conditions, whereas they switched to exert anti-tumor activity following photoirradiation. The specific effect was mediated by the onset of programed cell death, but only in the case of Ru12+ and Ru22+ was preceded by the loss of mitochondrial membrane potential soon after photoactivation and ROS production, thus supporting the occurrence of apoptosis via type II photochemical reactions. Thus, Ru(II)-polypyridyl-based photosensitizers represent challenging tools to be further investigated in the identification of new therapeutic approaches to overcome the innate chemoresistance to platinum derivatives of some ovarian epithelial cancers and to find innovative drugs for recurrent ovarian cancer.

Biochemical Basis of Selective Accumulation and Targeted Delivery of Photosensitizers to Tumor Tissues

The method of photodynamic therapy for treatment of malignant neoplasms is based on the selective of accumulation of photosensitizers in the tumor tissue. Insufficient selectivity of photosensitizers in relation to pathologically altered tissues and generalized distribution throughout the body leads to the development of severe toxic effects, including skin phototoxicity. The mechanisms underlying selectivity of photosensitizers for tumor tissue include selective binding to blood proteins and lipoproteins (considering that the number of receptors for those is increased on tumor cell membranes), uptake by macrophages, better solubility at low pH (acidic pH is characteristic of tumor cells), and other mechanisms. At present, increase in the efficiency of photodynamic therapy is largely associated with the additional targeting of photosensitizers to tumor tissues. Targeted delivery strategies are based on the differences in metabolism and gene expression profiles between the tumor and healthy cells. There are differences in expression of receptors, proteases, or transmembrane transporters in these cells. In particular, accelerated metabolism in many types of tumors leads to overexpression of receptors for epidermal growth factor, folic acid, transferrin, and a number of other compounds. This review considers biochemical basis for the selective accumulation of various classes of photosensitizers in tumors (chlorins, phthalocyanines, 5-aminolevulinic acid derivatives, etc.) and discusses various strategies of targeted delivery with emphasis on conjugation of photosensitizers with the receptor ligands overexpressed in tumor cells.

Phthalocyanine-Based Nanoassembly with Switchable Fluorescence and Photoactivities for Tumor Imaging and Phototherapy

Switchable theranostics are of great interest for accurate tumor imaging and targeted therapy. Here, we develop smart engineering to construct nanostructured phthalocyanines self-assembled by amphiphilic zinc phthalocyanines (ZnPcs) and hydrophobic copper phthalocyanines (CuPcs) (ZnPc(PEG)₅:CuPc-N, where ZnPc(PEG)₅ is monosubstituted ZnPcs with pentaethylene glycol as the substituent). The fluorescence and reactive oxygen species generation of ZnPc(PEG)₅:CuPc-N can be triggered depending on the membrane of the tumor cells for the imaging and photoactivities. Concerning the stability in blood circulation, the surface of the nanocomplex is coated with polydopamine, which responds to the tumor acidic microenvironment. ZnPc(PEG)₅ and CuPc focus on photodynamic and photothermal properties, respectively, and can be stimulated by a single laser beam, endowing ZnPc(PEG)₅:CuPc-N a combined antitumor effect from evaluations both in vitro and in vivo. In our study, the mechanism of switchable theranostics, the strategy of combined photodynamic and photothermal therapy, and the smart nanoengineering technology of phthalocyanines with poor water solubility can be applied to other phthalocyanines or phthalocyanine-like phototherapy agents.

Conquering Cancer Multi-Drug Resistance Using Curcumin and Cisplatin Prodrug-Encapsulated Mesoporous Silica Nanoparticles for Synergistic Chemo- and Photodynamic Therapies

Recently, the development of anti-cancer approaches using different physical or chemical pathways has shifted from monotherapy to synergistic therapy, which can enhance therapeutic effects. As a result, enormous efforts have been devoted to developing various delivery systems encapsulated with dual agents for synergistic effects and to combat cancer cells acquired drug resistance. In this study, we show how to make Institute of Bioengineering and Nanotechnology (IBN)-1-based mesoporous silica nanoparticles (MSNs) for multifunctional drug delivery to overcome drug resistance cancer therapy. Initially, curcumin (Cur)-embedded IBN-1 nanocomposites (IBN-1-Cur) are synthesized in a simple one-pot co-condensation and then immobilized with the prodrug of Cisplatin (CP) on the carboxylate-modified surface (IBN-1-Cur-CP) to achieve photodynamic therapy (PDT) and chemotherapy in one platform, respectively, in the fight against multidrug resistance (MDR) of MES-SA/DX5 cancer cells. The Pluronic F127 triblock copolymer, as the structure-directing agent, in nanoparticles acts as a p-glycoprotein (p-gp) inhibitor. These designed hybrid nanocomposites with excellent structural properties are efficiently internalized by the endocytosis and successfully deliver Cur and CP molecules into the cytosol. Furthermore, the presence of Cur photosensitizer in the nanochannels of MSNs resulted in increased levels of cellular reactive oxygen species (ROS) under light irradiation. Thus, IBN-1-Cur-CP showed excellent anti-cancer therapy in the face of MES-SA/DX5 resistance cancer cells, owing to the synergistic effects of chemo- and photodynamic treatment.

The Use of Photodynamic Therapy in the Treatment of Brain Tumors-A Review of the Literature

The treatment of neoplastic disease of the brain is still a challenge for modern medicine. Therefore, advanced methodologies are needed that can rationally and successfully contribute to the early diagnosis of primary and metastatic tumors growing within the brain. Photodynamic therapy (PDT) seems to be a valuable method of treatment for precancerous and cancerous lesions including brain tumors. The main advantage of PDT is its high efficiency, minimal invasiveness and no serious side effects, compared with chemotherapy and radiotherapy. This review was conducted through a comprehensive search of articles, scientific information databases and the websites of organizations dealing with cancer treatment. Key points from clinical trials conducted by other researchers are also discussed. The common databases such as PubMed, Google Scholar, EBSCO, Scopus, and Elsevier were used. Articles in the English language of reliable credibility were mainly analyzed. The type of publications considered included clinical and preclinical studies, systematic reviews, and case reports. Based on these collected materials, we see that scientists have already demonstrated the potential of PDT application in the field of brain tumors. Therefore, in this review, the treatment of neoplasm of the Central Nervous System (CNS) and the most common tumor, glioblastoma multiforme (GBM), have been explored. In addition, an overview of the general principles of PDT, as well as the mechanism of action of the therapy as a therapeutic platform for brain tumors, is described. The research was carried out in June 2022.

Effect of Chitosan and Amphiphilic Polymers on the Photosensitizing and Spectral Properties of Rose Bengal

The influence of chitosan (CS) and amphiphilic polymers (AP: pluronic F108 and polyvinylpyrrolidone (PVP)) on the photocatalytic activity of rose bengal (RB) in a model reaction of tryptophan photo-oxidation in phosphate-buffered saline (PBS) was studied. It was shown that in the presence of CS, the effective rate constant k_eff of tryptophan photo-oxidation catalyzed by RB in PBS solution decreases by a factor of two. This is due to the ionic interaction of the RB with the chitosan. Rose bengal in a slightly acidic environment (pH 4.5) passes into a neutral lactone form, which sharply reduces the photosensitizing properties of the dye. It was demonstrated that the introduction of AP into a solution containing RB and CS prevents direct interaction between RB and CS. This is evidenced by the presence of photocatalytic activity of the dye in the RB-AP-CS systems, as well as bathochromic shifts of the main absorption bands of the dye, and an increase in the optical density and luminescence intensity of the RB when AP is introduced into a buffer solution containing RB and chitosan. The presence of RB-CS and RB-AP interaction in aqueous and PBS media is confirmed by the increase in the degree of fluorescence anisotropy (r) of these binary systems. In an aqueous solution, the value of r for the RB-F108-CS system decreases by a factor of 3.5 (compared to the value of r for the RB-CS system), which is associated with the localization of the dye in pluronic micelles. In PBS, the fluorescence anisotropy is practically the same for all systems, which is related to the stability of the dye structure in this medium. The presence of interaction between RB and AP in aqueous solutions was confirmed by the proton NMR method. In addition, the formation of RB-F108 macromolecular complexes, which form associates during solution concentration (in particular, during evaporation), was shown by AFM. Such RB-AP-CS systems may be promising for practical application in the treatment of local foci of infections by aPDT.

Efficacy of Antimicrobial Photodynamic Therapy Mediated by Photosensitizers Conjugated with Inorganic Nanoparticles: Systematic Review and Meta-Analysis

Antimicrobial photodynamic therapy (aPDT) is a method that does not seem to promote antimicrobial resistance. Photosensitizers (PS) conjugated with inorganic nanoparticles for the drug-delivery system have the purpose of enhancing the efficacy of aPDT. The present study was to perform a systematic review and meta-analysis of the efficacy of aPDT mediated by PS conjugated with inorganic nanoparticles. The PubMed, Scopus, Web of Science, Science Direct, Cochrane Library, SciELO, and Lilacs databases were searched. OHAT Rob toll was used to assess the risk of bias. A random effect model with an odds ratio (OR) and effect measure was used. Fourteen articles were able to be included in the present review. The most frequent microorganisms evaluated were Staphylococcus aureus and Escherichia coli, and metallic and silica nanoparticles were the most common drug-delivery systems associated with PS. Articles showed biases related to blinding. Significant results were found in aPDT mediated by PS conjugated with inorganic nanoparticles for overall reduction of microorganism cultured in suspension (OR = 0.19 [0.07; 0.67]/p-value = 0.0019), E. coli (OR = 0.08 [0.01; 0.52]/p-value = 0.0081), and for Gram-negative bacteria (OR = 0.12 [0.02; 0.56/p-value = 0.0071). This association approach significantly improved the efficacy in the reduction of microbial cells. However, additional blinding studies evaluating the efficacy of this therapy over microorganisms cultured in biofilm are required.

Application of MOF-based nanotherapeutics in light-mediated cancer diagnosis and therapy

Light-mediated nanotherapeutics have recently emerged as promising strategies to precisely control the activation of therapeutic reagents and imaging probe both in vitro and in vivo, largely ascribed to their unique properties, including minimally invasive capabilities and high spatiotemporal resolution. Nanoscale metal-organic frameworks (NMOFs), a new family of hybrid materials consisting of metal attachment sites and bridging ligands, have been explored as a new platform for enhanced cancer diagnosis and therapy due to their tunable size, modifiable surface, good biocompatibility, high agent loading and, most significantly, their ability to be preferentially deposited in tumors through enhanced permeability and retention (EPR). Especially the light-driven NMOF-based therapeutic platform, which not only allow for increased laser penetration depth and enhanced targeting, but also enable imaging-guided or combined treatments. This review provides up-to-date developments of NMOF-based therapeutic platforms for cancer treatment with emphasis on light-triggered therapeutic strategies and introduces their advances in cancer diagnosis and therapy in recent years.

[Effects of low-dose photodynamic therapy on the function of human adipose mesenchymal stem cells and its mechanism]

Objective: To investigate the effects of low-dose photodynamic therapy on the proliferation, regulation, and secretion functions of human adipose mesenchymal stem cells (ADSCs) and the related mechanism, so as to explore a new method for the repair of chronic wounds. Methods: The experimental research methods were adopted. From February to April 2021, 10 patients (5 males and 5 females, aged 23 to 47 years) who underwent cutaneous surgery in the Department of Dermatology of the First Affiliated Hospital of Army Medical University (the Third Military Medical University) donated postoperative waste adipose tissue. The cells were extracted from the adipose tissue and the phenotype was identified. Three batches of ADSCs were taken, with each batch of cells being divided into normal control group with conventional culture only, photosensitizer alone group with conventional culture after being treated with Hemoporfin, irradiation alone group with conventional culture after being treated with red light irradiation, and photosensitizer+irradiation group with conventional culture after being treated with Hemoporfin and red light irradiation, with sample number of 3 in each group. At culture hour of 24 after the treatment of the first and second batches of cells, the ADSC proliferation level was evaluated by 5-ethynyl-2'-deoxyuridine staining method and the migration percentage of HaCaT cells cocultured with ADSCs was detected by Transwell experiment, respectively. On culture day of 7 after the treatment of the third batch of cells, the extracellular matrix protein expression of ADSCs was detected by immunofluorescence method. The ADSCs were divided into 0 min post-photodynamic therapy group, 15 min post-photodynamic therapy group, 30 min post-photodynamic therapy group, and 60 min post-photodynamic therapy group, with 3 wells in each group. Western blotting was used to detect the protein expressions and calculate the phosphorylated mammalian target of rapamycin complex (p-mTOR)/mammalian target of rapamycin (mTOR), phosphorylated p70 ribosomal protein S6 kinase (p-p70 S6K)/p70 ribosomal protein S6 kinase (p70 S6K) ratio at the corresponding time points after photodynamic therapy. Two batches of ADSCs were taken, and each batch was divided into normal control group, photodynamic therapy alone group, and photodynamic therapy+rapamycin group, with 3 wells in each group. At culture minute of 15 after the treatment, p-mTOR/mTOR and p-p70 S6K/p70 S6K ratios of cells from the first batch were calculated and detected as before. On culture day of 7 after the treatment, extracellular matrix protein expression of cells from the second batch was detected as before. Data were statistically analyzed with one-way analysis of variance and least significant difference test. Results: After 12 d of culture, the cells were verified as ADSCs. At culture hour of 24 after the treatment, the ADSC proliferation level ((4.0±1.0)% and (4.1±0.4)%, respectively) and HaCaT cell migration percentages (1.17±0.14 and 1.13±0.12, respectively) in photosensitizer alone group and irradiation alone group were similar to those of normal control group ((3.7±0.6)% and 1.00±0.16, respectively, P>0.05), and were significantly lower than those of photosensitizer+irradiation group ((34.2±7.0)% and 2.55±0.13, respectively, P<0.01). On culture day of 7 after the treatment, compared with those in normal control group, the expression of collagen Ⅲ in ADSCs of photosensitizer alone group was significantly increased (P<0.05), and the expressions of collagen Ⅰ and collagen Ⅲ in ADSCs of irradiation alone group were significantly increased (P<0.01). Compared with those in photosensitizer alone group and irradiation alone group, the expressions of collagen Ⅰ, collagen Ⅲ, and fibronectin of ADSCs in photosensitizer+irradiation group were significantly increased (P<0.01). Compared with those in 0 min post-photodynamic therapy group, the ratios of p-mTOR/mTOR and p-p70 S6K/p70 S6K of ADSCs in 15 min post-photodynamic therapy group were significantly increased (P<0.01), the ratios of p-p70 S6K/p70 S6K of ADSCs in 30 min post-photodynamic therapy group and 60 min post-photodynamic therapy group were both significantly increased (P<0.01). At culture minute of 15 after the treatment, compared with those in normal control group, the ratios of p-mTOR/mTOR and p-p70 S6K/p70 S6K of ADSCs in photodynamic therapy alone group were significantly increased (P<0.05 or P<0.01). Compared with those in photodynamic therapy alone group, the ratios of p-mTOR/mTOR and p-p70 S6K/p70 S6K of ADSCs in photodynamic therapy+rapamycin group were significantly decreased (P<0.05). On culture day of 7 after the treatment, compared with those in normal control group, the expressions of collagen Ⅰ, collagen Ⅲ, and fibronectin of ADSCs in photodynamic therapy alone group were significantly increased (P<0.01). Compared with those in photodynamic therapy alone group, the expressions of collagen Ⅰ, collagen Ⅲ, and fibronectin of ADSCs in photodynamic therapy+rapamycin group were significantly decreased (P<0.01). Conclusions: Low-dose photodynamic therapy can promote the proliferation of ADSCs, improve the ability of ADSCs to regulate the migration of HaCaT cells, and enhance the secretion of extracellular matrix protein by rapidly activating mTOR signaling pathway.

BODIPYs in PDT: A Journey through the Most Interesting Molecules Produced in the Last 10 Years

Over the past 30 years, photodynamic therapy (PDT) has shown great development. In the clinical setting the few approved molecules belong almost exclusively to the porphyrin family; but in the scientific field, in recent years many researchers have been interested in other families of photosensitizers, among which BODIPY has shown particular interest. BODIPY is the acronym for 4,4-difluoro-4-bora-3a, 4a-diaza-s-indacene, and is a family of molecules well-known for their properties in the field of imaging. In order for these molecules to be used in PDT, a structural modification is necessary which involves the introduction of heavy atoms, such as bromine and iodine, in the beta positions of the pyrrole ring; this change favors the intersystem crossing, and increases the ¹O₂ yield. This mini review focused on a series of structural changes made to BODIPYs to further increase ¹O₂ production and bioavailability by improving cell targeting or photoactivity efficiency.

Efficacy of antimicrobial photodynamic therapy versus antiviral therapy in the treatment of herpetic gingivostomatitis among children: Aa randomized controlled clinical trial

AIM

The aim of the present study was to evaluate the effect of antimicrobial photodynamic therapy (aPDT) as an adjunctive treatment to topical antiviral therapy for the treatment of children having herpetic gingivostomatitis.

MATERIALS AND METHODS

45 individuals (age group 12-18 years) with herpetic gingivostomatitis (HG) were divided into three groups on the basis of provision of treatment. (a) Group A: topical anti-viral therapy (TAT) (n = 14, mean age = 17.0 years) (b) Group B: antimicrobial photodynamic therapy (aPDT) (n = 15, mean age =17.7 years) and (c) Group C: topical anti-viral therapy + adjunctive aPDT (n = 16, mean age = 18.0 years) respectively. Pain scores [visual analogue scale (VAS) and McGill Pain Questionnaire (MPQ)] were assessed and HSV-1 was quantified. ENZYME LINKED IMMUNOSORBENT ASSAY (ELISA) was used to compute the pro-inflammatory cytokine including interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-α). The analysis of the mean values and inter group comparisons were evaluated with the Mann-Whitney test. The Friedman test was used to establish the comparison of the changes observed in HSV quantification, pain scores, and pro-inflammatory cytokines. ANOVA tests were employed for the quantification of differences observed at follow-ups. The assessments for the clinical trial were done at baseline, immediate after post-op, two, and four weeks, and three and six months respectively.

RESULTS

According to the analysis of the data obtained after the clinical assessment, the three groups reported a decrease in the pain scores, HSV-1 quantification and levels of the pro-inflammatory cytokines. However, Group C (TAT + aPDT) reported improvement in the observed parameters which was statistically significant in comparison to Group A (TAT) and Group B (aPDT) respectively.

CONCLUSION

Antimicrobial photodynamic therapy (aPDT) in conjunction with topical antiviral therapy (TAT) helped in reducing the pain scores and pro-inflammatory cytokine levels in herpetic gingivostomatitis among children.

Metallated phthalocyanines and their hydrophilic derivatives for multi-targeted oncological photodynamic therapy

BACKGROUND AND AIM

A photosensitizer (PS) delivery and comprehensive tumor targeting platform was developed that is centered on the photosensitization of key pharmacological targets in solid tumors (cancer cells, tumor vascular endothelium, and cellular and non-cellular components of the tumor microenvironment) before photodynamic therapy (PDT). Interstitially targeted liposomes (ITLs) encapsulating zinc phthalocyanine (ZnPC) and aluminum phthalocyanine (AlPC) were formulated for passive targeting of the tumor microenvironment. In previous work it was established that the PEGylated ITLs were taken up by cultured cholangiocarcinoma cells. The aim of this study was to verify previous results in cancer cells and to determine whether the ITLs can also be used to photosensitize cells in the tumor microenvironment and vasculature. Following positive results, rudimentary in vitro and in vivo experiments were performed with ZnPC-ITLs and AlPC-ITLs as well as their water-soluble tetrasulfonated derivatives (ZnPCS4 and AlPCS4) to assemble a research dossier and bring this platform closer to clinical transition.

METHODS

Flow cytometry and confocal microscopy were employed to determine ITL uptake and PS distribution in cholangiocarcinoma (SK-ChA-1) cells, endothelial cells (HUVECs), fibroblasts (NIH-3T3), and macrophages (RAW 264.7). Uptake of ITLs by endothelial cells was verified under flow conditions in a flow chamber. Dark toxicity and PDT efficacy were determined by cell viability assays, while the mode of cell death and cell cycle arrest were assayed by flow cytometry. In vivo systemic toxicity was assessed in zebrafish and chicken embryos, whereas skin phototoxicity was determined in BALB/c nude mice. A PDT efficacy pilot was conducted in BALB/c nude mice bearing human triple-negative breast cancer (MDA-MB-231) xenografts.

RESULTS

The key findings were that (1) photodynamically active PSs (i.e., all except ZnPCS4) were able to effectively photosensitize cancer cells and non-cancerous cells; (2) following PDT, photodynamically active PSs were highly toxic-to-potent as per anti-cancer compound classification; (3) the photodynamically active PSs did not elicit notable systemic toxicity in zebrafish and chicken embryos; (4) ITL-delivered ZnPC and ZnPCS4 were associated with skin phototoxicity, while the aluminum-containing PSs did not exert detectable skin phototoxicity; and (5) ITL-delivered ZnPC and AlPC were equally effective in their tumor-killing capacity in human tumor breast cancer xenografts and superior to other non-phthalocyanine PSs when appraised on a per mole administered dose basis.

CONCLUSIONS

AlPC(S4) are the safest and most effective PSs to integrate into the comprehensive tumor targeting and PS delivery platform. Pending further in vivo validation, these third-generation PSs may be used for multi-compartmental tumor photosensitization.

Nanomedicine and versatile therapies for cancer treatment

The higher prevalence of cancer is related to high rates of mortality and morbidity worldwide. By virtue of the properties of matter at the nanoscale, nanomedicine is proven to be a powerful tool to develop innovative drug carriers with greater efficacies and fewer side effects than conventional therapies. In this review, different nanocarriers for controlled drug release and their routes of administration have been discussed in detail, especially for cancer treatment. Special emphasis has been given on the design of drug delivery vehicles for sustained release and specific application methods for targeted delivery to the affected areas. Different polymeric vehicles designed for the delivery of chemotherapeutics have been discussed, including graft copolymers, liposomes, hydrogels, dendrimers, micelles, and nanoparticles. Furthermore, the effect of dimensional properties on chemotherapy is vividly described. Another integral section of the review focuses on the modes of administration of nanomedicines and emerging therapies, such as photothermal, photodynamic, immunotherapy, chemodynamic, and gas therapy, for cancer treatment. The properties, therapeutic value, advantages, and limitations of these nanomedicines are highlighted, with a focus on their increased performance versus conventional molecular anticancer therapies.

Diethynylarene-linked bis(triarylborane)cations as theranostic agents for tumor cell and virus-targeted photodynamic therapy

We recently reported diethynylarene-linked bis(triarylborane) tetracations which show remarkable fluorimetric and Raman-SERS sensing of DNA/RNA. In the current study, we show that they exhibit promising photodynamic therapy (PDT)-based biological activity on human cell lines and adenovirus type 5 (HAdV5), acting as theranostic agents. All compounds efficiently enter living cells showing negligible antiproliferative activity. Bis-thiophene- and anthracene- analogues bind non-covalently to HAdV5 virus with high affinity, the anthracene-analogue itself causing a moderate antiviral effect, i.e., decreased ability of the virus to infect human cells. Irradiation of bis-thiophene- and anthracene- analogues with visible light (400-700 nm) caused a very rapid (within 1 min) and strong increase in cytotoxicity, as well as an order of magnitude increase in antiviral activity, attributed to the formation of reactive oxygen species (ROS). Photochemical studies of the compounds revealed that, upon irradiation, they produce singlet oxygen, which correlates with the observed light-induced bioactivity.

Photodynamic therapy of lung cancer, where are we?

Lung cancer remains the leading threat of death globally, killing more people than colon, breast, and prostate cancers combined. Novel lung cancer treatments are being researched because of the ineffectiveness of conventional cancer treatments and the failure of remission. Photodynamic therapy (PDT), a cancer treatment method that is still underutilized, is a sophisticated cancer treatment that shows selective destruction of malignant cells via reactive oxygen species production. PDT has been extensively studied in vitro and clinically. Various PDT strategies have been shown to be effective in the treatment of lung cancer. PDT has been shown in clinical trials to considerably enhance the quality of life and survival in individuals with incurable malignancies. Furthermore, PDT, in conjunction with the use of nanoparticles, is currently being researched for use as an effective cancer treatment, with promising results. PDT and the new avenue of nanoPDT, which are novel treatment options for lung cancer with such promising results, should be tested in clinical trials to determine their efficacy and side effects. In this review, we examine the status and future potentials of nanoPDT in lung cancer treatment.

Photodynamic antibacterial and antibiofilm activity of riboflavin against Xanthomonas oryzae pv oryzae: an ecofriendly strategy to combat bacterial leaf blight (BLB) rice disease

Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv oryzae (Xoo), is one of the most damaging rice diseases, causing severe production losses depending on the rice variety. The purpose of this study was to develop an antibacterial photodynamic treatment (aPDT) using riboflavin for the treatment of BLB disease. Combining light and riboflavin (RF) therapy significantly reduced bacterial planktonic cells compared to RF alone. Photoactivated riboflavin also decreased biofilm biomass by reducing the number of viable sessile cells and the production of extracellular polymeric substances (EPS). Reactive oxygen species (ROS) levels in Xoo cells treated with photoactivated riboflavin were found to be significantly higher than in cells treated with riboflavin and light individually. Malondialdehyde (MDA) increased greatly in photoactivated riboflavin treated cells, indicating that severe oxidative damage was induced. Subsequently, a reduction in lactate dehydrogenase (LDH) activity in photoactivated riboflavin treated Xoo cells indicates that oxidative stress has disrupted the respiratory system, leading to bacterial cell death. In an ex vivo aPDT assay, photoactivated riboflavin successfully eradicated Xoo on the surface of rice leaves. Photoactivated riboflavin had no side effects on rice seed germination in subsequent trials, indicating that it is safe for agricultural applications. Therefore, all these findings suggest that aPDT is a potential alternative management strategy for BLB disease.

Surface modification of gold nanoparticles with 6-mercapto-1-hexanol to facilitate dual conjugation of protoporphyrin IX and folic acid for improving the targeted photochemical internalization

Objective(s):

Photochemical internalization (PCI) is an important type of photodynamic therapy for delivering macromolecules into the cytosol by the endocytosis process. In this study, 6-mercapto-1-hexanol (MH) was used to functionalize the gold nanostructure as a primer for surface modification to improve conjugation of multi-agents such as protoporphyrin IX (Pp-IX) and folic acid with gold nanoparticles (PpIX/FA-MH-AuNP) to facilitate the photochemical internalization.

Materials and Methods:

After surface modification of AuNPs with MH, PpIX and FA are bonded to the surface of the MH-AuNPs through the coupling reaction to produce the desired conjugated AuNPs. In the next step, the synthesized nanostructures were characterized by different methods. Finally, after selecting specific concentrations, light treatments were applied and cell survival was measured based on MTT analysis. Also, in order to better study the morphology of the cells, they were stained by the Giemsa method. The SPSS 16 software was used for data analysis

Results:

By surface modification of the nanostructure with MH and then conjugation of FA to it, the incubation time of the drug in PpIX/FA-MH-AuNP was reduced from 3 hr to 30 min. Also, at each light dose, cell death in the presence of PpIX/FA-MH-AuNP was significantly reduced compared with unconjugated conditions (P<0.001). Under these conditions, the ED50 for PpIX and PpIX-MH-AuNP and PpIX/FA-MH-AuNP at a concentration of 2.5 μg/ml is 8.9, 9.1, and 6.17 min, respectively.

Conclusion:

The results show that the PCI of PpIX/FA-MH-AuNP increases the selective phototoxicity efficiency on cancer cells compared with the conventional process of photodynamic therapy.

A new valid rhabdomyosarcoma spheroid culture model for in vitro evaluation of hypericin-based photodynamic therapy

BACKGROUND

Advanced stages of pediatric alveolar rhabdomyosarcoma (RMA) are associated with an unfavorable outcome at established therapeutic strategies, accentuating the need for novel treatment options. Photodynamic therapy (PDT) with hypericin (HYP) has shown strong cytotoxic effects in two-dimensional (2D) cell culture. In order to more accurately mimic in vivo tissue architecture and better predict pharmaceutical response, the aim of this study was to establish a spheroid culture model by which PDT efficacy could be assessed in a three-dimensional (3D) context.

MATERIALS AND METHODS

3D multicellular tumor spheroids were generated using various scaffold-based and scaffold-free techniques. On two reproducible methods, HYP-PDT was performed varying spheroid sizes, photosensitizer concentrations, and illumination times. The ability for HYP uptake within the spheroid was analyzed assessing the substrate's autofluorescence. Antitumorigenic treatment effects were evaluated investigating cell viability, spheroid morphology, proliferative activity, and induction of apoptosis.

RESULTS

Magnetic spheroid printing and orbital shaking methods were established as reproducible culturing systems producing uniform spheroids. Within assessed incubation times, HYP showed good penetration depth in spheroids containing 50,000 cells. PDT was causing metabolic and molecular impairment of RMA cells, resulting in viability decrease, reduction of cell proliferation, and induction of apoptosis.

CONCLUSION

Assessing HYP-based PDT in a 3D culture model, we were able to gain an insight on how parameters like photosensitizer, oxygen, and light distribution contribute to the phototoxic effect. Compared to 2D cell culture, a higher treatment resistance was detected, which can be related to spheroid structure and mechanisms of intercellular communication, signal transduction, and gene expression.

Photothermal agents based on small organic fluorophores with intramolecular motion

Photothermal therapy (PTT) has attracted great attention due to its noninvasive and low side effects. Photothermal agents (PTAs) which could convert absorbing light into heat play a critical role in PTT. For conventional small organic PTAs, the photothermal conversion ability is mainly achieved by intermolecular noncovalent interactions such as π-π interactions. However, in terms of organic fluorophores with rotator or vibrator segments, the balance between fluorescence emission and heat generation is mainly regulated by intramolecular motions which could be mediated by molecular engineering. Following this designing principle, various fluorophores with intramolecular motions for effective PTT have been reported. In this review, we highlight the recent progress of PTAs based on small organic fluorophores with intramolecular motions for enhanced PTT. Designing tactics of these fluorophores to afford long-wavelength absorption, high photothermal conversion ability, and effective accumulation capability are emphasized. Finally, one-for-all phototheranostics achieved by mediating intramolecular motions of these fluorophores are highlighted. We hope this review could pave a new avenue to developing fluorophores with intramolecular motion as PTAs to advance their clinical transition. STATEMENT OF SIGNIFICANCE: Recent progress of photothermal agents (PTAs) based on small organic fluorophores with intramolecular motion is summarized in this review. Molecular engineering of these small organic fluorophores to afford long-wavelength absorption, high photothermal conversion ability, and effective accumulation at tumor sites for enhanced photothermal therapy (PTT) is highlighted. Strategies to tune the intramolecular motions of these fluorophores to achieve multimodal phototherapy are emphasized as well.

Liquid crystalline lipid nanoparticle promotes the photodynamic activity of gallium protoporphyrin against S. aureus biofilms

Antimicrobial photodynamic therapy (aPDT) has emerged as an innovative strategy to combat antibiotic resistant microbes; yet aPDT efficacies against biofilms are sub-optimal due to inability of photosenstizers to reach microbes embedded in biofilm matrix. To overcome this challenge, liquid crystal lipid nanoparticles (LCNP) were employed in this study as a smart, biocompatible and triggerable delivery system for the new photosensitizer gallium protoporphyrin (GaPP), due to their capabilities in promoting efficient antimicrobial delivery to biofilms. The relationship between GaPP loading of LCNP, reactive oxygen species (ROS) production and the in vitro antibacterial activity against two antibiotic resistant Staphylococcus aureus strains was established. LCNP substantially improved the antibacterial activity of GaPP, completely eradicating S. aureus and MRSA planktonic cultures, using a GaPP concentration of 0.8 μM and light dose 1.9 J/cm². At the same concentration and light dose, unformulated GaPP triggered only a 4 log₁₀ and 2 log₁₀ reduction in respective planktonic cultures. Most importantly, the activity of GaPP against biofilms was enhanced by 2-fold compared to unformulated GaPP, reducing the viability of S. aureus and MRSA biofilms by 8 log₁₀ and 5 log₁₀, respectively. The biosafety of photoactivated GaPP-LCNP was evaluated against human fibroblasts, which indicated a high safety profile of the treatment. Therefore, these findings encourage further investigations of GaPP-LCNP as a potential treatment for localized chronic infections.

Potential Application of Photosensitizers With High-Z Elements for Synergic Cancer Therapy

The presence of heavy elements in photosensitizers (PS) strongly influences their electronic and photophysical properties, and hence, conjugation of PS with a suitable element is regarded as a potential strategy to improve their photodynamic properties. Moreover, PS conjugated to metal ion or metal complex and heavy atoms such as halogen have attracted considerable attention as promising agents for multimodal or synergistic cancer therapy. These tetrapyrrole compounds depending on the type and nature of the inorganic elements have been explored for photodynamic therapy (PDT), chemotherapy, X-ray photon activation therapy (PAT), and radiotherapy. Particularly, the combination of metal-based PS and X-ray irradiation has been investigated as a promising novel approach for treating deep-seated tumors, which in the case of PDT is a major limitation due to low light penetration in tissue. This review will summarize the present status of evidence on the effect of insertion of metal or halogen on the photophysical properties of PS and the effectiveness of various metal and halogenated PS investigated for PDT, chemotherapy, and PAT as mono and/or combination therapy.

Comparative analysis of Radachlorin accumulation, localization, and photobleaching in three cell lines by means of holographic and fluorescence microscopy

In this paper we compare the response of cells of established lines of different origin: HeLa, A549 and 3T3 to photodynamic treatment with Radachlorin photosensitizer. The analysis was performed on different aspects of the treatment procedure including photosensitizer accumulation, localization and photobleaching in cells and post-treatment dynamics of changes in cellular morphology at different treatment doses. It was shown that in the three cell lines Radachlorin accumulated in lysosomes to much greater extent than in mitochondria. The cells' response to treatment was analyzed by identification of their death pathways and evaluation of average phase shift dynamics using digital holographic microscopy. The analysis performed on the three cell lines allowed us to evaluate treatment doses specific for each pathway in each line. Among the three lines HeLa cells were found to be the most susceptible to treatment while 3T3 cells the most resistant. The comparison of these results with the data on Radachlorin accumulation, localization and photobleaching rates showed that the observed higher sensitivity of HeLa cells to photodynamic treatment correlated with higher photosensitizer uptake and more intensive photobleaching while lower sensitivity of 3T3 cells correlated with lower uptake and less intensive photobleaching.

Light-Controllable Binary Switch Activation of CAR T Cells

Major challenges to chimeric antigen receptor (CAR) T cell therapies include uncontrolled immune activity, off-tumor toxicities and tumor heterogeneity. To overcome these challenges, we engineered CARs directed against small molecules. By conjugating the same small molecule to distinct tumor-targeting antibodies, we show that small molecule specific-CAR T cells can be redirected to different tumor antigens. Such binary switches allow control over the degree of CAR T cell activity and enables simultaneous targeting of multiple tumor-associated antigens. We also demonstrate that ultraviolet light-sensitive caging of small molecules blocks CAR T cell activation. Exposure to ultraviolet light, uncaged small molecules and restored CAR T cell-mediated killing. Together, our data demonstrate that a light-sensitive caging system enables an additional level of control over tumor cell killing, which could improve the therapeutic index of CAR T cell therapies.

Injectable and Self-Healing Polysaccharide Hydrogel Loading Molybdenum Disulfide Nanoflakes for Synergistic Photothermal-Photodynamic Therapy of Breast Cancer

In order to overcome the limitation of traditional therapies for cancer and improve the accuracy of treatment, more advantageous cancer treatment methods need to be explored and studied. As a result, photothermal photodynamic therapy of breast cancer using bovine serum albumin (BSA) modifies molybdenum disulfide nanoflakes. Then the well-dispersed BSA-MoS₂ NFs are loaded in the injectable and self-healing polysaccharide hydrogel which is prepared by the reaction of oxidized sodium alginate (OSA) and hydroxypropyl chitosan (HPCS) through the formation of Schiff base bonds. The injection and self-healing properties of the nanocomposite hydrogel are investigated. In vitro photothermal and photodynamic investigations demonstrate that BSA-MoS₂ NFs possess obvious photothermal conversion and production of reactive oxygen species (ROS) under the irradiation of near infrared (NIR) laser (808 nm). In vivo anticancer investigation indicates that the nanocomposite hydrogel can be directly injected and remain in the tumor sites and achieve the synergistic photothermal-photodynamic therapy of cancer.

Antimicrobial efficacy and topographical alterations of photodynamic therapy versus conventional antimicrobials on contaminated zirconia ceramic in vitro

PURPOSE

The aim of this in vitro study was to assess the efficacy of antimicrobial photodynamic therapy (aPDT), neodymium-doped yttrium aluminium garnet (Nd:YAG) laser, and two other disinfecting agents against P. gingivalis and T. forsythia that colonized over zirconia ceramics and to evaluate if the disinfecting protocols result in zirconia surface alteration.

MATERIALS AND METHODS

The experiment was conducted on pre-sintered, commercially available Yttria Stabilized Zirconia (Y-TZP) ceramic blocks. The bacterial strains of P. gingivalis and T. forsythia were used to contaminate the zirconia specimens. The infected zirconia specimens were randomly divided into 4 groups (n=20/group): aPDT, Nd:YAG laser, hydrogen peroxide (H2O2), and chlorhexidine groups. The viability of bacteria was assayed using the MTT protocol. The surface roughness (Ra) of all zirconia specimens was estimated using a profilometer and a drop-shape analyzer was used to evaluate the contact angle using a special sessile drop method.

RESULTS

A statistically significant reduction by the aPDT group is noticed for P. gingivalis and T. forsythia species compared to other disinfection methods (p<0.05). The second highest reduction was seen for chlorhexidine followed by Nd:YAG laser. The least reduction was demonstrated for the hydrogen peroxide group. Statistically, there was no significant difference in Ra scores between the four groups. However, the contact angles were significantly reduced from the zirconia specimens after the aPDT method which indicates a hydrophilicity increase compared to other groups. The SFE scores of all decontamination protocols from highest to lowest were aPDT (41.68), chlorhexidine (39.83), Nd:YAG (34.52), and H2O2 (29.88).

CONCLUSIONS

Antimicrobial photodynamic therapy demonstrated a high antibacterial efficacy over zirconia ceramic surface without altering surface topography.

Targeting Microenvironment of Melanoma and Head and Neck Cancers in Photodynamic Therapy

Background:

Photodynamic therapy (PDT), in comparison to other skin cancers, is still far less effective for melanoma, due to the strong absorbance and the role of melanin in cytoprotection. The tumour microenvironment (TME) has a significant role in tumour progression, and the hypoxic TME is one of the main reasons for melanoma progression to metastasis and its resistance to PDT. Hypoxia is also a feature of solid tumours in the head and neck region that indicates negative prognosis.

Objective:

The aim of this study was to individuate and describe systematically the main strategies in targeting the TME, especially hypoxia, in PDT against melanoma and head and neck cancers (HNC), and assess the current success in their application.

Methods:

PubMed was used for searching, in MEDLINE and other databases, for the most recent publications on PDT against melanoma and HNC in combination with the TME targeting and hypoxia.

Results:

In PDT for melanoma and HNC, it is very important to control hypoxia levels, and amongst the different approaches, oxygen self-supply systems are often applied. Vascular targeting is promising, but to improve it, optimal drug-light interval, and formulation to increase the accumulation of the photosensitiser in the tumour vasculature, have to be established. On the other side, the use of angiogenesis inhibitors, such as those interfering with VEGF signalling, is somewhat less successful than expected and needs to be further investigated.

Conclusion:

The combination of PDT with immunotherapy by using multifunctional nanoparticles continues to develop and seems to be the most promising for achieving a complete and lasting antitumour effect.

Novel Lysosome-Targeting Fluorescence Off-On Photosensitizer for Near-Infrared Hypoxia Imaging and Photodynamic Therapy In Vitro and In Vivo

Photodynamic therapy (PDT) has emerged as a new antitumor modality. Hypoxia, a vital characteristic of solid tumors, can be explored to stimulate the fluorescence response of photosensitizers (PSs). Considering the characteristics of PDT, the targeting of organelles employing PS would enhance antitumor effects. A new multifunctional cyanine-based PS (CLN) comprising morpholine and nitrobenzene groups was prepared and characterized. It generated fluorescence in the near-infrared (NIR) region in the presence of sodium dithionite (Na₂S₂O₄) and nitroreductase (NTR). The response mechanism of CLN was well investigated, thus revealing that its obtained reduction product was CLNH. The obtained fluorescence and singlet oxygen quantum yield of CLNH were 8.65% and 1.60%, respectively. Additionally, the selective experiment for substrates indicated that CLN exhibited a selective response to NTR. Thus, CLN fluorescence could be selectively switched on and its fluorescence intensity increased, following a prolonged stay in hypoxic cells. Furthermore, fluorescence colocalization demonstrated that CLN could effectively target lysosomes. CLN could generate reactive oxygen species and kill tumor cells (IC50 for 4T1 cells was 7.4 μM under a hypoxic condition), following its response to NTR. NIR imaging and targeted PDT were finally applied in vivo.

A host-guest strategy for converting the photodynamic agents from a singlet oxygen generator to a superoxide radical generator

Type-I photosensitizers (PSs) generate cytotoxic oxygen radicals by electron transfer even in a hypoxic environment. Nevertheless, the preparation of type-I PSs remains a challenge due to the competition of triplet-triplet energy transfer with O2 (type-II process). In this work, we report an effective strategy for converting the conventional type-II PS to a type-I PS by host-guest complexation. Electron-rich pillar[5]arenes are used as an electron donor and macrocyclic host to produce a host-guest complex with the traditional electron-deficient type-II PS, an iodide BODIPY-based guest. The host-guest complexation promotes intermolecular electron transfer from the pillar[5]arene moiety to BODIPY and then to O2 by the type-I process upon light-irradiation, leading to efficient generation of the superoxide radical (O2 -˙). The results of anti-tumor studies indicate that this supramolecular PS demonstrates high photodynamic therapy efficacy even under hypoxic conditions. This work provides an efficient method to prepare type-I PSs from existing type-II PSs by using a supramolecular strategy.

Comparative randomized trial study about the efficacy of photobiomodulation and curcumin antimicrobial photodynamic therapy as a coadjuvant treatment of oral mucositis in oncologic patients: antimicrobial, analgesic, and degree alteration effect

INTRODUCTION

As conventional treatments currently available for mucositis are not considerably effective, there is a need to implement an adjuvant protocol for the treatment of oral mucositis in patients undergoing radiotherapy and chemotherapy.

PURPOSE

To evaluate the effect of photobiomodulation (PBM) and antimicrobial photodynamic therapy (aPDT) mediated by curcumin and blue LED as an adjunct treatment of oral mucositis for oncology patients using chemotherapy and/or radiotherapy.

METHODS

Clinical, randomized study, in a single location, in an oncology service of a general hospital, with a total of 30 patients (over 18 years old) with stable oral mucosa lesions in the process of chemotherapy and/or radiotherapy. The patients were divided into 3 groups: control group (treated with nystatin), PBM group (treated with low-level laser therapy), and the aPDT group (treated with 450-nm blue LED and curcumin photosensitizer).

RESULTS

The results showed, by means of intra-group comparisons, that the two experimental treatments promoted yeast reduction of the genus Candida in the last two evaluations (21 days and 30 days), but not in the first two evaluations (7 days and 14 days). The intra-group comparisons showed that the control and aPDT group showed a significant difference in the degree of mucositis over the four evaluations performed, with the results pointing out that the mucositis worsened in the control group from the 14th day, while reduced in the aPDT group from the 21st day of treatment.

CONCLUSION

A reduction in the degree of mucositis and pain score was observed in the PBM and aPDT groups, with the aPDT group standing out when presenting early clinical improvement in relation to the PBM group and the control group, thus emphasizing its effectiveness within the desired aspects. Regarding the antimicrobial effect, aPDT showed a greater reduction of yeasts of the genus Candida in the tested parameters.

Photoactivation of Curcumin Doped Poly-Lactic-Co-Glycolic Acid Nanoparticles in Rat Model with Fixed Orthodontic Appliances

This study aimed to evaluate the antimicrobial effect of curcumin doped poly-lactic-co-glycolic acid nanoparticles (Cur-PLGA-Nps)-mediated antimicrobial photodynamic therapy (aPDT), as well as the probiotics on S. mutans in rats with fixed orthodontic appliances. Orthodontic appliances were ligated to the right maxillary of the rats. After the oral colonization of S. mutans, the rats were then treated in four groups including Cur-PLGA-Nps, light-emitting diode, Cur-PLGA-Nps-mediated aPDT, and probiotic (Lactobacillus acidophilus). After that, the S. mutans counts and the gtfB gene expression of S. mutans were determined on days 4, 7, 15, and 30. Probiotic and Cur-PLGA-Nps-mediated aPDT groups significantly reduced the count of S. mutans in a time-dependent manner (P < 0.05). So, probiotics and Cur-PLGA-Nps-mediated aPDT were able to reduce S. mutans more than other groups on the 30th day. Also, there was no considerable difference between Cur-PLGA-Nps-mediated aPDT and probiotic groups in bacterial growth inhibition. The expression level of gtfB gene was significantly downregulated at all-time intervals after exposure to Cur-PLGA-Nps-mediated aPDT compared with untreated bacteria (P < 0.05). According to the results, simultaneous use of Cur-PLGA-Nps-mediated aPDT and probiotic therapeutic approaches can be suggested to increase effectiveness.

Which cell death modality wins the contest for photodynamic therapy of cancer?

Photodynamic therapy (PDT) was discovered more than 100 years ago. Since then, many protocols and agents for PDT have been proposed for the treatment of several types of cancer. Traditionally, cell death induced by PDT was categorized into three types: apoptosis, cell death associated with autophagy, and necrosis. However, with the discovery of several other regulated cell death modalities in recent years, it has become clear that this is a rather simple understanding of the mechanisms of action of PDT. New observations revealed that cancer cells exposed to PDT can pass through various non-conventional cell death pathways, such as paraptosis, parthanatos, mitotic catastrophe, pyroptosis, necroptosis, and ferroptosis. Nowadays, immunogenic cell death (ICD) has become one of the most promising ways to eradicate tumor cells by activation of the T-cell adaptive immune response and induction of long-term immunological memory. ICD can be triggered by many anti-cancer treatment methods, including PDT. In this review, we critically discuss recent findings on the non-conventional cell death mechanisms triggered by PDT. Next, we emphasize the role and contribution of ICD in these PDT-induced non-conventional cell death modalities. Finally, we discuss the obstacles and propose several areas of research that will help to overcome these challenges and lead to the development of highly effective anti-cancer therapy based on PDT.

Nanomaterials enabling clinical translation of antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (aPDT) has emerged as a promising approach to aid the fight against looming antibiotic resistance. aPDT harnesses the energy of light through photosenstizers to generate highly reactive oxygen species that can inactivate bacteria and fungi with no resistance. To date aPDT has shown great efficacy against microbes causing localized infections in the skin and the oral cavity. However, its wide application in clinical settings has been limited due to both physicochemical and biological challenges. Over the past decade nanomaterials have contributed to promoting photosensitizer performance and aPDT efficiency, yet further developments are required to establish accredited treatment options. In this review we discuss the challenges facing the clinical application of aPDT and the opportunities that nanotechnology may offer to promote the safety and efficiency of aPDT.

Combination of Curcumin and Photodynamic Therapy Based on the Use of Red Light or Near-Infrared Radiation in Cancer: a Systematic Review

BACKGROUND

Photodynamic therapy (PDT) is a therapeutic intervention that can be applied to the treatment of cancer. The interaction between a photosensitizer (PS), ideal wavelength radiation and tissue molecular oxygen, triggers a series of photochemical reactions that are responsible for the production of reactive oxygen species. These highly reactive species can decrease proliferation and induce tumor cell death. The search for PS of natural origin extracted from plants becomes relevant, as they have photoactivation capacity, preferentially targeting tumor cells and because they do not present any or little toxicity to healthy cells.

OBJECTIVE

Our work aimed to carry out a qualitative systematic review to investigate the effects of curcumin (CUR), a molecule considered as PS of natural origin, on PDT, using red light or near infrared radiation, in tumor models.

METHODS

A systematic search was performed in three databases (PubMed, Scopus, and Web of Science) using the PICOT method, retrieving a total of 1,373 occurrences. At the end of the peer screening, using inclusion, exclusion, and eligibility criteria, 25 eligible articles were included in this systematic review.

RESULTS

CUR, whether in its free state, associated with metal complexes or other PS, and in a nanocarrier system, was considered a relevant PS for PDT using red light or near-infrared against tumoral models in vitro and in vivo, acting by increasing cytotoxicity, inhibiting proliferation, inducing cell death mainly by apoptosis, and changing oxidative parameters.

CONCLUSION

The results found in this systematic review suggest the potential use of CUR as a PS of natural origin to be applied in PDT against many neoplasms, encouraging further search in the field of PDT against cancer and serving as an investigative basis for upcoming pre-clinical and clinical applications.

Recent Advances in Near Infrared Upconverting Nanomaterials for Targeted Photodynamic Therapy of Cancer

Photodynamic therapy (PDT) is a well-established treatment of cancer that uses the toxic reactive oxygen species, including singlet oxygen (1O2), generated by photosensitiser drugs following irradiation of a specific wavelength to destroy the cancerous cells and tumours. Visible light is commonly used as the excitation source in PDT, which is not ideal for cancer treatment due to its reduced tissue penetration, and thus inefficiency to treat deep-lying tumours. Additionally, these wavelengths exhibit elevated autofluorescence background from the biological tissues which hinders optical biomedical imaging. An alternative to UV-Vis irradiation is the use of near infrared (NIR) excitation for PDT. This can be achieved using upconverting nanoparticles (UCNPs) functionalised with photosensitiser (PS) drugs where UCNPs can be used as an indirect excitation source for the activation of PS drugs yielding to the production of singlet 1O2 following NIR excitation. The use of nanoparticles for PDT is also beneficial due to their tumour targeting capability, either passively via the enhanced permeability and retention (EPR) effect or actively via stimuli-responsive targeting and ligand-mediated targeting (ie. using recognition units that can bind specific receptors only present or overexpressed on tumour cells). Here, we review recent advances in NIR upconverting nanomaterials for PDT of cancer with a clear distinction between those reported nanoparticles that could potentially target the tumour due to accumulation via the EPR effect (passive targeting) and nanoparticle-based systems that contain targeting agents with the aim of actively target the tumour via a molecular recognition process.

The Meta-Substituted Isomer of TMPyP Enables More Effective Photodynamic Bacterial Inactivation than Para-TMPyP In Vitro

Porphyrinoid-based photodynamic inactivation (PDI) provides a promising approach to treating multidrug-resistant infections. However, available agents for PDI still have optimization potential with regard to effectiveness, toxicology, chemical stability, and solubility. The currently available photosensitizer TMPyP is provided with a para substitution pattern (para-TMPyP) of the pyridinium groups and has been demonstrated to be effective for PDI of multidrug-resistant bacteria. To further improve its properties, we synthetized a structural variant of TMPyP with an isomeric substitution pattern in a meta configuration (meta-TMPyP), confirmed the correct structure by crystallographic analysis and performed a characterization with NMR-, UV/Vis-, and IR spectroscopy, photostability, and singlet oxygen generation assay. Meta-TMPyP had a hypochromic shift in absorbance (4 nm) with a 55% higher extinction coefficient and slightly improved photostability (+6.9%) compared to para-TMPyP. Despite these superior molecular properties, singlet oxygen generation was increased by only 5.4%. In contrast, PDI, based on meta-TMPyP, reduced the density of extended spectrum β-lactamase-producing and fluoroquinolone-resistant Escherichia coli by several orders of magnitude, whereby a sterilizing effect was observed after 48 min of illumination, while para-TMPyP was less effective (p < 0.01). These findings demonstrate that structural modification with meta substitution increases antibacterial properties of TMPyP in PDI.

Recent advances in nanoparticle-based targeting tactics for antibacterial photodynamic therapy

Abstract

The rise of antibacterial drug resistance means treatment options are becoming increasingly limited. We must find ways to tackle these hard-to-treat drug-resistant and biofilm infections. With the lack of new antibacterial drugs (such as antibiotics) reaching the clinics, research has switched focus to exploring alternative strategies. One such strategy is antibacterial photodynamic therapy (aPDT), a system that relies on light, oxygen, and a non-toxic dye (photosensitiser) to generate cytotoxic reactive oxygen species. This technique has already been shown capable of handling both drug-resistant and biofilm infections but has limited clinical approval to date, which is in part due to the low bioavailability and selectivity of hydrophobic photosensitisers. Nanotechnology-based techniques have the potential to address the limitations of current aPDT, as already well-documented in anti-cancer PDT. Here, we review recent advances in nanoparticle-based targeting tactics for aPDT.

Graphical Abstract

Advances in local therapy for glioblastoma - taking the fight to the tumour

Despite advances in neurosurgery, chemotherapy and radiotherapy, glioblastoma remains one of the most treatment-resistant CNS malignancies, and the tumour inevitably recurs. The majority of recurrences appear in or near the resection cavity, usually within the area that received the highest dose of radiation. Many new therapies focus on combatting these local recurrences by implementing treatments directly in or near the tumour bed. In this Review, we discuss the latest developments in local therapy for glioblastoma, focusing on recent preclinical and clinical trials. The approaches that we discuss include novel intraoperative techniques, various treatments of the surgical cavity, stereotactic injections directly into the tumour, and new developments in convection-enhanced delivery and intra-arterial treatments.

Effectiveness of Experimental Whitening Toothpastes Containing Colorants on the Optical Properties of Enamel

Objective. This in vitro study investigated the whitening potential of experimental toothpastes containing optical colorants in their formulations in comparison with commercial products. The chemical and physical characteristics of the toothpastes, the morphology, and elemental analysis of the enamel surface after treatment were also analyzed. Materials and Methods. One hundred twenty-five bovine incisor teeth were randomly divided into five groups according to the treatment: (i) experimental PHTALOX dental gel (PHT); (ii) experimental blue silica dental gel (SDG); (iii) Sensodyne Whitening Repair & Protect (WRP); (iv) Sensodyne True White (STW); (v) Snow White Toothpaste (SWS). The whiteness index differences (ΔWID) and color alteration (CIELab-ΔE, CIEDE2000-ΔE00) were calculated after color change analysis using a spectrophotometer before and after the enamel treatment (n = 25). The surface and cross-sectional micromorphology were assessed using scanning electron microscopy. The elemental analyses were determined with energy-dispersive X-ray spectroscopy (EDS). The pH, particle size, zeta potential, and polydispersity index of toothpaste were evaluated. Data was statistically analyzed (ANOVA/Tukey, 5%). Results. Whitening toothpastes containing optical colorants were effective for whitening the enamel, as whiter teeth were observed following treatment (higher means of ΔWID). In addition, when the parameters ΔEab and ΔE00 were evaluated, these toothpastes were graded as very good effectiveness (grade 4). Other toothpastes were graded as 3 (good effectiveness). PHT had a neutral pH and a larger mean particle size (412.8 nm). Elemental analysis demonstrated enamel with a silicon-enriched mineral layer on the enamel surface treated with SDG. The Ca/P ratio after enamel treatment varied from 1.74 (SWS) to 2.04 (SDG and WRP). Conclusions. Experimental whitening toothpastes containing optical colorants are effective at bleaching the enamel. The synergism among the different parameters analyzed seems to positively affect the color change after brushing with whitening toothpastes containing optical colorants.