Cell death pathways in photodynamic therapy of cancer

Investigation of Copper Cysteamine Nanoparticles as a New Type of Radiosensitiers for Colorectal Carcinoma Treatment

Copper Cysteamine (Cu-Cy) is a new photosensitizer and a novel radiosensitizer that can be activated by light, X-ray and microwave to produce singlet oxygen for cancer treatment. However, the killing mechanism of Cu-Cy nanoparticles on cancer cells is not clear yet and Cu-Cy nanoparticles as novel radiosensitizers have never been tested on colorectal cancers. Here, for the first time, we investigate the treatment efficiency of Cu-Cy nanoparticles on SW620 colorectal cells and elucidate the underlying mechanisms of the effects. The results show that X-ray activated Cu-Cy nanoparticles may kill SW620 cancerscells is in a dose-dependent manner. The JC-1 staining shows the mitochondrial membrane potential is decreased after the treatment. The observations confirm that Cu-Cy nanoparticles may improve X-ray radiotherapy on cancer treatment and X-ray activated Cu-Cy nanoparticles can be efficiently destroy colorectal cancer cells by inducing apoptosis as well as autophagy. As a new type of radiosensitizers and photosensitizers, Cu-Cy nanoparticles have a good potential for colorectal cancer treatment and the discovery of autophagy induced by X-ray irradiated Cu-Cy nanoparticles sheds a good insight to the mechanism of Cu-Cy for cancer treatment as a new radiosensitizers.

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

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

Enhanced efficiency of cell death by lysosome-specific photodamage

Mobilization of specific mechanisms of regulated cell death is a promising alternative to treat challenging illness such as neurodegenerative disease and cancer. The use of light to activate these mechanisms may provide a route for target-specific therapies. Two asymmetric porphyrins with opposite charges, the negatively charged TPPS2a and the positively charged CisDiMPyP were compared in terms of their properties in membrane mimics and in cells. CisDiMPyP interacts to a larger extent with model membranes and with cells than TPPS2a, due to a favorable electrostatic interaction. CisDiMPyP is also more effective than TPPS2a in damaging membranes. Surprisingly, TPPS2a is more efficient in causing photoinduced cell death. The lethal concentration on cell viability of 50% (LC50) found for TPPS2a was ~3.5 (raw data) and ~5 (considering photosensitizer incorporation) times smaller than for CisDiMPyP. CisDiMPyP damaged mainly mitochondria and triggered short-term phototoxicity by necro-apoptotic cell death. Photoexcitation of TPPS2a promotes mainly lysosomal damage leading to autophagy-associated cell death. Our data shows that an exact damage in lysosome is more effective to diminish proliferation of HeLa cells than a similar damage in mitochondria. Precisely targeting organelles and specifically triggering regulated cell death mechanisms shall help in the development of new organelle-target therapies.

Photothermal and photodynamic activity of polymeric nanoparticles based on α-tocopheryl succinate-RAFT block copolymers conjugated to IR-780

The aim of this work was the generation of a multifunctional nanopolymeric system that incorporates IR-780 dye, a near-infrared (NIR) imaging probe that exhibits photothermal and photodynamic properties; and a derivate of α-tocopheryl succinate (α-TOS), a mitochondria-targeted anticancer compound. IR-780 was conjugated to the hydrophilic segment of copolymer PEG-b-polyMTOS, based on poly(ethylene glycol) (PEG) and a methacrylic derivative of α-tocopheryl succinate (MTOS), to generate IR-NP, self-assembled nanoparticles (NPs) in aqueous media which exhibit a hydrophilic shell and a hydrophobic core. During assembly, the hydrophobic core of IR-NP could encapsulate additional IR-780 to generate derived subspecies carrying different amount of probe (IR-NP-eIR). Evaluation of photo-inducible properties of IR-NP and IR-NP-eIR were thoroughly assessed in vitro. Developed nanotheranostic particles showed distinct fluorescence and photothermal behavior after excitation by a laser light emitting at 808nm. Treatment of MDA-MB-453 cells with IR-NP or IR-NP-eIR resulted in an efficient internalization of the IR-780 dye, while subsequent NIR-laser irradiation led to a severe decrease in cell viability. Photocytoxicity conducted by IR-NP, which could not be attributed to the generation of lethal hyperthermia, responded to an increase in the levels of intracellular reactive oxygen species (ROS). Therefore, the fluorescence imaging and inducible phototoxicity capabilities of NPs derived from IR-780-PEG-b-polyMTOS copolymer confer high value to these nanotheranostics tools in clinical cancer research.

STATEMENT OF SIGNIFICANCE

Multifunctional polymeric nanoparticles (NPs) that combine imaging and therapeutic properties are highly valuable in cancer treatment. In this paper we describe the development of NPs that are fluorescent in the near-infrared (NIR). This is important for their visualization in living tissues that present low absorption and low autofluorescence in this wavelength region (between 700 and 1000nm). Moreover, NPs present photothermal and photodynamic properties when NIR irradiated: the NPs produce an efficient increment of temperature and increase the intracellular reactive oxygen species (ROS) when laser irradiated at 808nm. These tuneable photoinduced properties make the NPs highly cytotoxic after NIR irradiation and provide a new tool for highly precise cancer treatment.

Photobiomodulation of breast and cervical cancer stem cells using low-intensity laser irradiation

Breast and cervical cancers are dangerous threats with regard to the health of women. The two malignancies have reached the highest record in terms of cancer-related deaths among women worldwide. Despite the use of novel strategies with the aim to treat and cure advanced stages of cancer, post-therapeutic relapse believed to be caused by cancer stem cells is one of the challenges encountered during tumor therapy. Therefore, further attention should be paid to cancer stem cells when developing novel anti-tumor therapeutic approaches. Low-intensity laser irradiation is a form of phototherapy making use of visible light in the wavelength range of 630-905 nm. Low-intensity laser irradiation has shown remarkable results in a wide range of medical applications due to its biphasic dose and wavelength effect at a cellular level. Overall, this article focuses on the cellular responses of healthy and cancer cells after treatment with low-intensity laser irradiation alone or in combination with a photosensitizer as photodynamic therapy and the influence that various wavelengths and fluencies could have on the therapeutic outcome. Attention will be paid to the biomodulative effect of low-intensity laser irradiation on cancer stem cells.

Flexible laser endoscope for minimally invasive photodynamic diagnosis (PDD) and therapy (PDT) toward efficient tumor removal

Photodynamic diagnosis (PDD) provides valuable assistance in distinguishing tumor from the normal tissue using fluorescent colors. These colors are affected by the illumination and the photosensitizer, and PDD may be applied during operation. After the diagnosis, photodynamic therapy (PDT) could destroy tiny lesion without removing the tissue, something that considerably reduces the possibility of tumor recurrence. However, the present endoscope technologies cannot realize PDD and PDT using the same endoscope. The use of different endoscopes presents three main disadvantages. First, the intra-operation diagnosis cannot be realized unless endoscopes are the different during operation; use of different endoscopes further burdens of the surgeon and the patients. Second, it is very difficult to find the exact same area via the PDT endoscope, one that is confirmed as tumor or cancer by the PDD endoscope, when different endoscopes are used just as present applied. Third, the laser irradiation field cannot be controlled with present technologies, something that may hurt the surrounding healthy tissue or blood vessels, thus leading to serious complications. To resolve the above-mentioned problems, we propose a new flexible laser endoscope, which integrates PDD and PDT, and provides a controllable laser irradiation field for the surgeon. Experimental results proved that the resolution of both diagnosis and therapy images were five times higher than that of standard laparoscopy, the laser power density was high enough for PDT for a distance of 20 to 50 mm away from the target tumor, and the position accuracy of the presented system was half of the required errors. Moreover, the in-vitro experiments further verified the effectiveness of the laser endoscope system. Therefore, this new flexible laser endoscope is potentially suitable for future in-vivo experiments or clinical applications.

Cancer cell death pathways caused by photothermal and photodynamic effects through gold nanoring induced surface plasmon resonance

The different death pathways of cancer cells under the conditions of the photothermal (PT), effect, photodynamic (PD) effect, and their combination are evaluated. By incubating cells with Au nanoring (NRI) either linked with the photosensitizer, AlPcS, or not, the illumination of a visible continuous laser for exciting the photosensitizer or an infrared femtosecond laser for exciting the localized surface plasmon resonance of Au NRI, leads to various PT and PD conditions for study. Three different staining dyes are used for identifying the cell areas of different damage conditions at different temporal points of observation. The cell death pathways and apoptotic evolution speeds under different cell treatment conditions are evaluated based on the calibration of the threshold laser fluences for causing early-apoptosis (EA) and necrosis (NE) or late-apoptosis (LA). It is found that with the PT effect only, strong cell NE is generated and the transition from EA into LA is faster than that caused by the PD effect when the EA stage is reached within 0.5 h after laser illumination. By combining the PT and PD effects, in the first few hours, the transition speed becomes lower, compared to the case of the PT effect only, when both Au NRIs internalized into cells and adsorbed on cell membrane exist. When the Au NRIs on cell membrane is removed, in the first few hours, the transition speed becomes higher, compared to the case of the PD effect only.

Selective photocytotoxicity of anthrols on cancer stem-like cells: The effect of quinone methides or reactive oxygen species

Cancer stem cells (CSCs) are a subpopulation of cancer cells that share properties of embryonic stem cells like pluripotency and self-renewal and show increased resistance to chemo- and radiotherapy. Targeting CSC, rather than cancer cells in general, is a novel and promising strategy for cancer treatment. Novel therapeutic approaches, such as photodynamic therapy (PDT) have been investigated. A promising group of phototherapeutic agents are reactive intermediates - quinone methides (QMs). This study describes preparation of QM precursor, 2-hydroxy-3-hydroxymethylanthracene (2) and a detailed photochemical and photobiological investigation on similar anthracene derivatives 3 and 4. Upon photoexcitation with near visible light at λ > 400 nm 1 and 2 give QMs, that were detected by laser flash photolysis and their reactivity with nucleophiles has been demonstrated in the preparative irradiation experiments where the corresponding adducts were isolated and characterized. 3 and 4 cannot undergo photodehydration and deliver QM, but lead to the formation of phenoxyl radical and singlet oxygen, respectively. The activity of 1-4 was tested on a panel of human tumor cell lines, while special attention was devoted to demonstrate their potential selectivity towards the cells with CSC-like properties (HMLEshEcad). Upon the irradiation of cell lines treated with 1-4, an enhancement of antiproliferative activity was demonstrated, but the DNA was not the target molecule. Confocal microscopy revealed that these compounds entered the cell and, upon irradiation, reacted with cellular membranes. Our experiments demonstrated moderate selectivity of 2 and 4 towards CSC-like cells, while necrosis was shown to be a dominant cell death mechanism. Especially interesting was the selectivity of 4 that produced higher levels of ROS in CSC-like cells, which forms the basis for further research on cancer phototherapy, as well as for the elucidation of the underlying mechanism of the observed CSC selectivity based on oxidative stress activation.

Polymer-lipid-PEG hybrid nanoparticles as photosensitizer carrier for photodynamic therapy

Polymer-lipid-PEG hybrid nanoparticles were investigated as carriers for the photosensitizer (PS), 5,10,15,20-Tetrakis(4-hydroxy-phenyl)-21H,23H-porphine (pTHPP) for use in photodynamic therapy (PDT). A self-assembled nanoprecipitation technique was used for preparing two types of core polymers poly(d,l-lactide-co-glycolide) (PLGA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with lipid-PEG as stabilizer. The resulting nanoparticles had an average particle size of 88.5±3.4nm for PLGA and 215.0±6.3nm for PHBV. Both nanoparticles exhibited a core-shell structure under TEM with high zeta potential and loading efficiency. X-ray powder diffraction analysis showed that the encapsulated pTHPP molecules in polymeric nanoparticles no longer had peaks of free pTHPP in the crystalline state. The pTHPP molecules encapsulated inside the polymeric core demonstrated improved photophysical properties in terms of singlet oxygen generation and cellular uptake rate in a FTC-133 human thyroid carcinoma cell line, compared to non-encapsulated pTHPP. The pTHPP-loaded polymer-lipid-PEG nanoparticles showed better in vitro phototoxicity compared to free pTHPP, in both time- and concentration-dependent manners. Overall, this study provides detailed analysis of the photophysical properties of pTHPP molecules when entrapped within either PLGA or PHBV nanoparticle cores, and demonstrates the effectiveness of these systems for delivery of photosensitizers. The two polymeric systems may have different potential benefits, when used with cancer cells. For instance, the pTHPP-loaded PLGA system requires only a short time to show a PDT effect and may be suitable for topical PDT, while the delayed photo-induced cytotoxic effect of the pTHPP-loaded PHBV system may be more suitable for cancer solid tumors. Hence, both pTHPP-encapsulated polymer-lipid-PEG nanoparticles can be considered promising delivery systems for PDT cancer treatment.

Photodynamic therapy for the treatment of atherosclerotic plaque: Lost in translation?

Acute coronary syndrome is a life-threatening condition of utmost clinical importance, which, despite recent progress in the field, is still associated with high morbidity and mortality. Acute coronary syndrome results from a rupture or erosion of vulnerable atherosclerotic plaque with secondary platelet activation and thrombus formation, which leads to partial or complete luminal obstruction of a coronary artery. During the last decade, scientific evidence demonstrated that when an acute coronary event occurs, several nonculprit plaques are in a "vulnerable" state. Among the promising approaches, several investigations provided evidence of photodynamic therapy (PDT)-induced stabilization and regression of atherosclerotic plaque. Significant development of PDT strategies improved its therapeutic outcome. This review addresses PDT's pertinence and major problems/challenges toward its translation to a clinical reality.

Use of Spectroscopic Techniques for Evaluating the Coupling of Porphyrins on Biocompatible Nanoparticles. A Potential System for Photodynamics, Theranostics, and Nanodrug Delivery Applications

Modern medicine has been searching for new and more efficient strategies for diagnostics and therapeutics applications. Considering this, porphyrin molecules have received great interest for applications in photodiagnostics and phototherapies, even as magnetic nanoparticles for drug-delivery systems and magnetic-hyperthermia therapy. Aiming to obtain a multifunctional system, which combines diagnostics with therapeutic functions on the same platform, the present study employed UV/vis absorption and fluorescence spectroscopies to evaluate the interaction between meso-tetrakis(p-sulfonatofenyl)porphyrin (TPPS) and maghemite nanoparticles (γ-Fe₂O₃). These spectroscopic techniques allowed us to describe the dynamics of coupling porphyrins on nanoparticles and estimate the number of 21 porphyrins per nanoparticle. Also, the binding parameters, such as the association constants (K_a = 8.89 × 10⁵ M^-1) and bimolecular quenching rate constant (k_q = 2.54 × 10¹⁴ M^-1 s^-1) were obtained. These results suggest a static quenching process where the electrostatic attraction plays an essential role. The work shows that spectroscopic techniques are powerful tools to evaluate the coupling of organic molecules and nanoparticles. Besides, the system studied provides a relevant background for potential applications in bionanotechnology and nanomedicine, such as (1) nanodrug delivery system, (2) photodiagnostics/theranostics, and/or (3) a combined action of photodynamic and hyperthermia therapies, working in a synergetic way.

Effects of Photodynamic Therapy Using Yellow LED-light with Concomitant Hypocrellin B on Apoptotic Signaling in Keloid Fibroblasts

Keloid is a common and refractory disease characterized by abnormal fibroblast proliferation and excessive deposition of extracellular matrix components. Hypocrellin B (HB) is a natural perylene quinone photosensitizer. In this experiment, we studied the effects of photodynamic therapy (PDT) using yellow light from light-emitting diode (LED) combined with HB on keloid fibroblasts (KFB) in vitro. Our results showed that HB-LED PDT treatment induced significant KFB apoptosis and decreased KFB cell viability. HB-LED PDT treatment lead to significant BAX upregulation and BCL-2 downregulation in KFB cells, which led to elevation of intracellular free Ca²⁺ and activation of caspase-3. Our data provides preliminary evidence for the potential of HB-LED PDT as a therapeutic strategy for keloid.

Oncologic Photodynamic Therapy: Basic Principles, Current Clinical Status and Future Directions

Photodynamic therapy (PDT) is a clinically approved cancer therapy, based on a photochemical reaction between a light activatable molecule or photosensitizer, light, and molecular oxygen. When these three harmless components are present together, reactive oxygen species are formed. These can directly damage cells and/or vasculature, and induce inflammatory and immune responses. PDT is a two-stage procedure, which starts with photosensitizer administration followed by a locally directed light exposure, with the aim of confined tumor destruction. Since its regulatory approval, over 30 years ago, PDT has been the subject of numerous studies and has proven to be an effective form of cancer therapy. This review provides an overview of the clinical trials conducted over the last 10 years, illustrating how PDT is applied in the clinic today. Furthermore, examples from ongoing clinical trials and the most recent preclinical studies are presented, to show the directions, in which PDT is headed, in the near and distant future. Despite the clinical success reported, PDT is still currently underutilized in the clinic. We also discuss the factors that hamper the exploration of this effective therapy and what should be changed to render it a more effective and more widely available option for patients.

Photodynamic Synergistic Effect of Pheophorbide a and Doxorubicin in Combined Treatment against Tumoral Cells

A combination of therapies to treat cancer malignancies is at the forefront of research with the aim to reduce drug doses (ultimately side effects) and diminish the possibility of resistance emergence given the multitarget strategy. With this goal in mind, in the present study, we report the combination between the chemotherapeutic drug doxorubicin (DOXO) and the photosensitizing agent pheophorbide a (PhA) to inactivate HeLa cells. Photophysical studies revealed that DOXO can quench the excited states of PhA, detracting from its photosensitizing ability. DOXO can itself photosensitize the production of singlet oxygen; however, this is largely suppressed when bound to DNA. Photodynamic treatments of cells incubated with DOXO and PhA led to different outcomes depending on the concentrations and administration protocols, ranging from antagonistic to synergic for the same concentrations. Taken together, the results indicate that an appropriate combination of DOXO with PhA and red light may produce improved cytotoxicity with a smaller dose of the chemotherapeutic drug, as a result of the different subcellular localization, targets and mode of action of the two agents.

Photodynamic therapy for the treatment of complex anal fistula

BACKGROUND

Photodynamic therapy (PDT) is a new procedure for the treatment of anal fistula. This preliminary study was designed to investigate the safety and effectiveness of this new technique in the treatment of anal fistula.

METHODS

Ten patients were treated with PDT. Intralesional 5-aminolevulinic acid (ALA) 2% was directly injected into the fistula. The internal and external orifices were closed. After an incubation period of 2 h, the fistula was irradiated using an optical fibre connected to a red laser (MULTIDIODE 630 PDT, INTERmedic, Spain) operating at 1 W/cm for 3 min (180 Joules). Patient demographics, operation notes and complications were recorded.

RESULTS

There were no complications. The average length of patient follow-up was 14.9 months (range 12-20 months). We could observe primary healing in eight patients (80%). Two patients (20%) showed persistence of suppuration after the operation. No patient reported incontinence postoperatively.

CONCLUSIONS

PDT is a potential sphincter-saving procedure that is safe, simple and minimally invasive and has a high success rate.

Proton MR Spectroscopy and Diffusion MR Imaging Monitoring to Predict Tumor Response to Interstitial Photodynamic Therapy for Glioblastoma

Despite recent progress in conventional therapeutic approaches, the vast majority of glioblastoma recur locally, indicating that a more aggressive local therapy is required. Interstitial photodynamic therapy (iPDT) appears as a very promising and complementary approach to conventional therapies. However, an optimal fractionation scheme for iPDT remains the indispensable requirement. To achieve that major goal, we suggested following iPDT tumor response by a non-invasive imaging monitoring. Nude rats bearing intracranial glioblastoma U87MG xenografts were treated by iPDT, just after intravenous injection of AGuIX® nanoparticles, encapsulating PDT and imaging agents. Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS) allowed us an original longitudinal follow-up of post-treatment effects to discriminate early predictive markers. We successfully used conventional MRI, T2 star (T2*), Diffusion Weighted Imaging (DWI) and MRS to extract relevant profiles on tissue cytoarchitectural alterations, local vascular disruption and metabolic information on brain tumor biology, achieving earlier assessment of tumor response. From one day post-iPDT, DWI and MRS allowed us to identify promising markers such as the Apparent Diffusion Coefficient (ADC) values, lipids, choline and myoInositol levels that led us to distinguish iPDT responders from non-responders. All these responses give us warning signs well before the tumor escapes and that the growth would be appreciated.

Evaluation of Silicon Phthalocyanine 4 Photodynamic Therapy Against Human Cervical Cancer Cells In Vitro and in Mice

BACKGROUND

Cervical cancer is the second most common cancer in women worldwide [1]. Photodynamic therapy has been used for cervical intraepithelial neoplasia with good responses, but few studies have used newer phototherapeutics. We evaluated the effectiveness of photodynamic therapy using Pc 4 in vitro and in vivo against human cervical cancer cells.

METHODS

CaSki and ME-180 cancer cells were grown as monolayers and spheroids. Cell growth and cytotoxicity were measured using a methylthiazol tetrazolium assay. Pc 4 cellular uptake and intracellular distrubtion were determined. For in vitro Pc 4 photodynamic therapy cells were irradiated at 667nm at a fluence of 2.5 J/cm² at 48 h. SCID mice were implanted with CaSki and ME-180 cells both subcutaneously and intracervically. Forty-eight h after Pc 4 photodynamic therapy was administered at 75 and 150 J/cm².

RESULTS

The IC₅₀s for Pc 4 and Pc 4 photodynamic therapy for CaSki and ME-180 cells as monolayers were, 7.6μM and 0.016μM and >10μM and 0.026μM; as spheroids, IC₅₀s of Pc 4 photodynamic therapy were, 0.26μM and 0.01μM. Pc 4 was taken up within cells and widely distributed in tumors and tissues. Intracervical photodynamic therapy resulted in tumor death, however mice died due to gastrointestinal toxicity. Photodynamic therapy resulted in subcutaneous tumor death and growth delay.

CONCLUSIONS

Pc 4 photodynamic therapy caused death within cervical cancer cells and xenografts, supporting development of Pc 4 photodynamic therapy for treatment of cervical cancer. Support: P30-CA47904, CTSI BaCCoR Pilot Program.

Photodynamic therapy mediated by acai oil (Euterpe oleracea Martius) in nanoemulsion: A potential treatment for melanoma

Melanoma is the most aggressive and lethal form of skin cancer, responsible for >80% of deaths. Standard treatments for late-stage melanoma usually present poor results, leading to life-threatening side effects and low overall survival. Thus, it is necessary to rethink treatment strategies and design new tools for the treatment of this disease. On that ground, we hereby report the use of acai oil in nanoemulsion (NanoA) as a novel photosensitizer for photodynamic therapy (PDT) used to treat melanoma in in vitro and in vivo experimental models. NIH/3T3 normal cells and B16F10 melanoma cell lines were treated with PDT and presented 85% cell death for melanoma cells, while maintaining high viability in normal cells. Flow cytometry indicated that cell death occurred by late apoptosis/necrosis. Tumor bearing C57BL/6 mice treated five times with PDT using acai oil in nanoemulsion showed tumor volume reduction of 82% in comparison to control/tumor group. Necrotic tissue per tumor area reached its highest value in PDT-treated mice, supporting PDT efficacy. Overall, acai oil in nanoemulsion was an effective photosensitizer, representing a promising source of new photosensitizing molecules for PDT treatment of melanoma, a tumor with an inherent tendency to be refractory for this type of therapy.

Laser applications in surgery

In modern medicine, lasers are increasingly utilized for treatment of a variety of pathologies as interest in less invasive treatment modalities intensifies. The physics behind lasers allows the same basic principles to be applied to a multitude of tissue types using slight modifications of the system. Multiple laser systems have been studied within each field of medicine. The term "laser" was combined with "surgery," "ablation," "lithotripsy," "cancer treatment," "tumor ablation," "dermatology," "skin rejuvenation," "lipolysis," "cardiology," "atrial fibrillation (AF)," and "epilepsy" during separate searches in the PubMed database. Original articles that studied the application of laser energy for these conditions were reviewed and included. A review of laser therapy is presented. Laser energy can be safely and effectively used for lithotripsy, for the treatment of various types of cancer, for a multitude of cosmetic and reconstructive procedures, and for the ablation of abnormal conductive pathways. For each of these conditions, management with lasers is comparable to, and potentially superior to, management with more traditional methods.

Optimization and therapeutic effects of PDT mediated by ALA and MAL in the treatment of cutaneous malignant lesions: A comparative study

5-aminolevulinic acid (ALA) and its methylated ester (MAL) are the most common topical agents used in photodynamic therapy (PDT) as precursors of the photosensitizer protoporphyrin IX (PpIX). The induction of newly PpIX depends on incubation time of each photosensitizer in the tissue and the presence of high intralesional porphyrin levels is an important parameter for the PDT effectiveness. This study used laser-induced fluorescence (LIF) spectroscopy to evaluate the optimum time to light exposure of PDT mediated by ALA (20% w/w) and MAL (10% w/w) to treat malignant lesions precursors of cutaneous squamous cell carcinoma induced in mice. The therapeutic effects obtained by optimized ALA- and MAL-PDT were assessed 10 and 20 days after treatments. Higher PpIX levels were evidenced in the lesions photosensitized by ALA than MAL and according to LIF measurements the PDT irradiation was performed, respectively, at 300 and 330 minutes after ALA and MAL incubation. Histopathological analysis evidenced necrosis and epithelial atrophy after 10 days of PDT using both prodrugs, as well as reepitelization and collagen deposition at 20 days. Thus, despite the distinct concentration of ALA and MAL used in the formulation of each photosensitizing cream, PDT mediated by both photosensitizing agents obtained similar therapeutic outcomes.

Nanoceria-Mediated Drug Delivery for Targeted Photodynamic Therapy on Drug-Resistant Breast Cancer

Photodynamic therapy (PDT) has shown great potential for overcoming drug-resistant cancers. Here, we report a multifunctional drug delivery system based on chlorin e6 (Ce6)/folic acid (FA)-loaded branched polyethylenimine-PEGylation ceria nanoparticles (PPCNPs-Ce6/FA), which was developed for targeted PDT to overcome drug-resistant breast cancers. Nanocarrier delivery and FA targeting significantly promoted the cellular uptake of photosensitizers (PSs), followed by their accumulation in lysosomes. PPCNPs-Ce6/FA generated reactive oxygen species (ROS) after near-infrared irradiation (NIR, 660 nm), leading to reduced P-glycoprotein (P-gp) expression, lysosomal membrane permeabilization (LMP), and excellent phototoxicity toward resistant MCF-7/ADR cells, even at ultralow doses. Moreover, we identified NIR-triggered lysosomal-PDT using the higher dose of PPCNPs-Ce6/FA, which stimulated cell death by plasma membrane blebbing, cell swelling, and energy depletion, indicating an oncosis-like cell death pathway, despite the occurrence of apoptotic or autophagic mechanisms at lower drug doses. In vivo studies showed prolonged blood circulation times, low toxicity in mice, and high tumor accumulation of PPCNPs-Ce6/FA. In addition, using NIR-triggered PDT, PPCNPs-Ce6/FA displayed excellent potency for tumor regression in the MCF-7/ADR xenograft murine model. This study suggested that multifunctional PPCNPs-Ce6/FA nanocomposites are a versatile and effective drug delivery system that may potentially be exploited for phototherapy to overcome drug-resistant cancers, and the mechanisms of cell death induced by PDT should be considered in the design of clinical protocols.

Pegylated and nanoparticle-conjugated sulfonium salt photo triggers necrotic cell death

Photodynamic therapy (PDT) processes involving the production of singlet oxygen face the issue of oxygen concentration dependency. Despite high oxygen delivery, a variety of properties related to metabolism and vascular morphology in cancer cells result in hypoxic environments, resulting in limited effectiveness of such therapies. An alternative oxygen-independent agent whose cell cytotoxicity can be remotely controlled by light may allow access to treatment of hypoxic tumors. Toward that end, we developed and tested both polyethylene glycol (PEG)-functionalized and hydrophilic silica nanoparticle (SiNP)-enriched photoacid generator (PAG) as a nontraditional PDT agent to effectively induce necrotic cell death in HCT-116 cells. Already known for applications in lithography and cationic polymerization, our developed oxygen-independent PDT, whether free or highly monodispersed on SiNPs, generates acid when a one-photon (1P) or two-photon (2P) excitation source is used, thus potentially permitting deep tissue treatment. Our study shows that when conjugated to SiNPs with protruding amine functionalities (SiNP–PAG9), such atypical PDT agents can be effectively delivered into HCT-116 cells and compartmentalize exclusively in lysosomes and endosomes. Loss of cell adhesion and cell swelling are detected when an excitation source is applied, suggesting that SiNP–PAG9, when excited via near-infrared 2P absorption (a subject of future investigation), can be used as a delivery system to selectively induce cell death in oxygen-deprived optically thick tissue.

Quantitative Multi-Parametric Magnetic Resonance Imaging of Tumor Response to Photodynamic Therapy

Objective

The aim of this study was to characterize response to photodynamic therapy (PDT) in a mouse cancer model using a multi-parametric quantitative MRI protocol and to identify MR parameters as potential biomarkers for early assessment of treatment outcome.

Methods

CT26.WT colon carcinoma tumors were grown subcutaneously in the hind limb of BALB/c mice. Therapy consisted of intravenous injection of the photosensitizer Bremachlorin, followed by 10 min laser illumination (200 mW/cm²) of the tumor 6 h post injection. MRI at 7 T was performed at baseline, directly after PDT, as well as at 24 h, and 72 h. Tumor relaxation time constants (T₁ and T₂) and apparent diffusion coefficient (ADC) were quantified at each time point. Additionally, Gd-DOTA dynamic contrast-enhanced (DCE) MRI was performed to estimate transfer constants (K^trans) and volume fractions of the extravascular extracellular space (v_e) using standard Tofts-Kermode tracer kinetic modeling. At the end of the experiment, tumor viability was characterized by histology using NADH-diaphorase staining.

Results

The therapy induced extensive cell death in the tumor and resulted in significant reduction in tumor growth, as compared to untreated controls. Tumor T₁ and T₂ relaxation times remained unchanged up to 24 h, but decreased at 72 h after treatment. Tumor ADC values significantly increased at 24 h and 72 h. DCE-MRI derived tracer kinetic parameters displayed an early response to the treatment. Directly after PDT complete vascular shutdown was observed in large parts of the tumors and reduced uptake (decreased K^trans) in remaining tumor tissue. At 24 h, contrast uptake in most tumors was essentially absent. Out of 5 animals that were monitored for 2 weeks after treatment, 3 had tumor recurrence, in locations that showed strong contrast uptake at 72 h.

Conclusion

DCE-MRI is an effective tool for visualization of vascular effects directly after PDT. Endogenous contrast parameters T₁, T₂, and ADC, measured at 24 to 72 h after PDT, are also potential biomarkers for evaluation of therapy outcome.

Beyond the Barriers of Light Penetration: Strategies, Perspectives and Possibilities for Photodynamic Therapy

Photodynamic therapy (PDT) is a photochemistry based treatment modality that involves the generation of cytotoxic species through the interactions of a photosensitizer molecule with light irradiation of an appropriate wavelength. PDT is an approved therapeutic modality for several cancers globally and in several cases has proved to be effective where traditional treatments have failed. The key parameters that determine PDT efficacy are 1. the photosensitizer (nature of the molecules, selectivity, and macroscopic and microscopic localization etc.), 2. light application (wavelength, fluence, fluence rate, irradiation regimes etc.) and 3. the microenvironment (vascularity, hypoxic regions, stromal tissue density, molecular heterogeneity etc.). Over the years, several groups aimed to monitor and manipulate the components of these critical parameters to improve the effectiveness of PDT treatments. However, PDT is still misconstrued to be a surface treatment primarily due to the limited depths of light penetration. In this review, we present the recent advances, strategies and perspectives in PDT approaches, particularly in cancer treatment, that focus on increasing the 'damage zone' beyond the reach of light in the body. This is enabled by a spectrum of approaches that range from innovative photosensitizer excitation strategies, increased specificity of phototoxicity, and biomodulatory approaches that amplify the biotherapeutic effects induced by photodynamic action. Along with the increasing depth of understanding of the underlying physical, chemical and physiological mechanisms, it is anticipated that with the convergence of these strategies, the clinical utility of PDT will be expanded to a powerful modality in the armamentarium for the management of cancer.

Intratumoral Photodynamic Therapy With Newly Synthesized Pheophorbide a in Murine Oral Cancer

Photodynamic therapy (PDT) is a therapeutic alternative for malignant tumors that uses a photosensitizer. Our group recently synthesized photosensitizer pheophorbide a (Pa) from chlorophyll-a. The present study investigated the therapeutic effect of PDT using intratumoral administration of the synthetic photosensitizer Pa in an in vivo murine oral squamous cell carcinoma (OSCC) animal model. Pa accumulation was measured using the fluorescence spectrum and imaging in living C3H mice. Intratumoral treatment of Pa-PDT (IT Pa-PDT) significantly inhibited the growth of transplanted OSCC cells. Histopathological examination of tumor tissues showed that PCNA expression was significantly decreased, while TUNEL-stained cells were markedly increased in the IT Pa-PDT group compared to controls. IT Pa-PDT-induced apoptosis was confirmed by immunoblot. Reduction of Bcl-2 and cleavage of caspase 3 and PARP were observed in IT Pa-PDT. These data demonstrate that IT Pa-PDT inhibited tumor cell proliferation and induced apoptosis, which is correlated with the anticancer activity of IT Pa-PDT. These potent antitumor activities of IT Pa-PDT were observed in both the immunohistochemistry and Western blot experiments. Our findings suggest the intratumoral therapeutic potential of Pa-PDT on OSCC. Additionally, demonstrated detection of Pa using a fluorescence spectroscopy system or molecular imaging system provides a means for simultaneous diagnosis and treatment of OSCC.

Targeting Antitumor Immune Response for Enhancing the Efficacy of Photodynamic Therapy of Cancer: Recent Advances and Future Perspectives

Photodynamic therapy (PDT) is a minimally invasive therapeutic strategy for cancer treatment, which can destroy local tumor cells and induce systemic antitumor immune response, whereas, focusing on improving direct cytotoxicity to tumor cells treated by PDT, there is growing interest in developing approaches to further explore the immune stimulatory properties of PDT. In this review we summarize the current knowledge of the innate and adaptive immune responses induced by PDT against tumors, providing evidence showing PDT facilitated-antitumor immunity. Various immunotherapeutic approaches on different cells are reviewed for their effectiveness in improving the treatment efficiency in concert with PDT. Future perspectives are discussed for further enhancing PDT efficiency via intracellular targetable drug delivery as well as optimized experimental model development associated with the study of antitumor immune response.

Photoinduced effects of m-tetrahydroxyphenylchlorin loaded lipid nanoemulsions on multicellular tumor spheroids

BACKGROUND

Photosensitizers are used in photodynamic therapy (PDT) to destruct tumor cells, however, their limited solubility and specificity hampers routine use, which may be overcome by encapsulation. Several promising novel nanoparticulate drug carriers including liposomes, polymeric nanoparticles, metallic nanoparticles and lipid nanocomposites have been developed. However, many of them contain components that would not meet safety standards of regulatory bodies and due to difficulties of the manufacturing processes, reproducibility and scale up procedures these drugs may eventually not reach the clinics. Recently, we have designed a novel lipid nanostructured carrier, namely Lipidots, consisting of nontoxic and FDA approved ingredients as promising vehicle for the approved photosensitizer m-tetrahydroxyphenylchlorin (mTHPC).

RESULTS

In this study we tested Lipidots of two different sizes (50 and 120 nm) and assessed their photodynamic potential in 3-dimensional multicellular cancer spheroids. Microscopically, the intracellular accumulation kinetics of mTHPC were retarded after encapsulation. However, after activation mTHPC entrapped into 50 nm particles destroyed cancer spheroids as efficiently as the free drug. Cell death and gene expression studies provide evidence that encapsulation may lead to different cell killing modes in PDT.

CONCLUSIONS

Since ATP viability assays showed that the carriers were nontoxic and that encapsulation reduced dark toxicity of mTHPC we conclude that our 50 nm photosensitizer carriers may be beneficial for clinical PDT applications.

Design of Pluronic-Based Formulation for Enhanced Redaporfin-Photodynamic Therapy against Pigmented Melanoma

The therapeutic outcome of photodynamic therapy (PDT) with redaporfin (a fluorinated sulfonamide bacteriochlorin, F2BMet or LUZ11) was improved using Pluronic-based (P123, F127) formulations. Neither redaporfin encapsulated in Pluronic nor micelles alone exhibited cytotoxicity in a broad concentration range. Comprehensive in vitro studies against B16F10 melanoma cells showed that redaporfin-P123 micelles enhanced cellular uptake and increased oxidative stress compared with redaporfin-F127 or photosensitizer alone after short incubation times. ROS-sensitive fluorescent probes showed that the increased oxidative stress is due, at least in part, to a more efficient formation of hydroxyl radicals, and causes strong light-dose dependent apoptosis and necrosis. Tissue distribution and pharmacokinetic studies in tumor-bearing mice show that the Pluronic P123 formulation of redaporfin increases its bioavailability as well as the tumor-to-muscle and tumor-to-skin ratios, in comparison with Cremophor EL and Pluronic F127 formulations. Redaporfin in P123 was most successful in the PDT of C57BL/6J mice bearing subcutaneously implanted B16F10 melanoma tumors. Vascular-targeted PDT combining 1.5 mg kg(-1) redaporfin in P123 with a light dose of 74 J cm(-2) led to 100% complete cures (i.e., no tumor regrowth over one year post-treatment). This remarkable result reveals that modification of redaporfin with Pluronic block copolymers overcomes the resistance of melanoma cells to PDT possibly via increased tumor selectivity and enhanced ROS generation.

P2X7 receptor as a novel drug delivery system to increase the entrance of hydrophilic drugs into cells during photodynamic therapy

The second-generation photosensitizer methylene blue (MB) exhibits photochemical and photophysical properties suitable for photodynamic therapy (PDT)-based cancer treatment. However, the clinical application of MB is limited because of its high hydrophilicity, which hinders its penetration into tumor tissues. Therefore, new methods to improve the entry of MB into the cytoplasm of target cells are necessary. Because MB has a mass of 319 Da, transient pores on the plasma membrane, such as the pore induced by the P2X7 receptor (P2X7R) that allows the passage of molecules up to 900 Da, could be used. Using MTT viability assays, flow cytometry experiments, and fluorescence microscopy, we evaluated the toxicity and phototoxicity of MB and potentiation effects of ATP and MB on cell death processes in the J774 cell line (via a P2X7-associated pore). We observed that treatment with 5 μM MB for 15 min promoted the rate of entry of MB into the cytoplasm to 4.7 %. However, treatment with 5 μM MB and 1 mM ATP for the same amount of time increased this rate to 90.2 %. However, this effect was inhibited by pretreatment with a P2X7 antagonist. We used peritoneal macrophages and a cell line that does not express P2X7R as controls. These cells were more resistant to PDT with MB under the same experimental conditions. Taken together, these results suggest the use of the pore associated with P2X7R as a drug delivery system to increase the passage of hydrophilic drugs into cells that express this receptor, thus facilitating PDT.

Multifunctional Photosensitizer Grafted on Polyethylene Glycol and Polyethylenimine Dual-Functionalized Nanographene Oxide for Cancer-Targeted Near-Infrared Imaging and Synergistic Phototherapy

The integration of photodynamic therapy (PDT) with photothermal therapy (PTT) offers improved efficacy in cancer phototherapy. Herein, a PDT photosensitizer (IR-808) with cancer-targeting ability and near-infrared (NIR) sensitivity was chemically conjugated to both polyethylene glycol (PEG)- and branched polyethylenimine (BPEI)-functionalized nanographene oxide (NGO). Because the optimal laser wavelength (808 nm) of NGO for PTT is consistent with that of IR-808 for PDT, the IR-808-conjugated NGO sheets (NGO-808, 20-50 nm) generated both large amounts of reactive oxygen species (ROS) and local hyperthermia as a result of 808 nm laser irradiation. With PEG- and BPEI-modified NGO as the carrier, the tumor cellular uptake of NGO-808 exhibited higher efficacy than that of strongly hydrophobic free IR-808. Through evaluation with both human and mouse cancer cells, NGO-808 was demonstrated to provide significantly enhanced PDT and PTT effects compared to individual PDT using IR-808 or PTT using NGO. Furthermore, NGO-808 preferentially accumulated in cancer cells as mediated by organic-anion transporting polypeptides (OATPs) overexpressed in many cancer cells, providing the potential for highly specific cancer phototherapy. Using the targeting ability of NGO-808, in vivo NIR fluorescence imaging enabled tumors and their margins to be clearly visualized at 48 h after intravenous injection, providing a theranostic platform for imaging-guided cancer phototherapy. Remarkably, after a single injection of NGO-808 and 808 nm laser irradiation for 5 min, the tumors in two tumor xenograft models were ablated completely, and no tumor recurrence was observed. After treatment with NGO-808, no obvious toxicity was detected in comparison to control groups. Thus, high-performance cancer phototherapy with minimal side effects was afforded from synergistic PDT/PTT treatment and cancer-targeted accumulation of NGO-808.

The PARP inhibitor PJ-34 sensitizes cells to UVA-induced phototoxicity by a PARP independent mechanism

A combination of a photosensitizer with light of matching wavelength is a common treatment modality in various diseases including psoriasis, atopic dermatitis and tumors. DNA damage and production of reactive oxygen intermediates may impact pathological cellular functions and viability. Here we set out to investigate the role of the nuclear DNA nick sensor enzyme poly(ADP-ribose) polymerase 1 in photochemical treatment (PCT)-induced tumor cell killing. We found that silencing PARP-1 or inhibition of its enzymatic activity with Veliparib had no significant effect on the viability of A431 cells exposed to 8-methoxypsoralen (8-MOP) and UVA (2.5J/cm(2)) indicating that PARP-1 is not likely to be a key player in either cell survival or cell death of PCT-exposed cells. Interestingly, however, another commonly used PARP inhibitor PJ-34 proved to be a photosensitizer with potency equal to 8-MOP. Irradiation of PJ-34 with UVA caused changes both in the UV absorption and in the 1H NMR spectra of the compound with the latter suggesting UVA-induced formation of tautomeric forms of the compound. Characterization of the photosensitizing effect revealed that PJ-34+UVA triggers overproduction of reactive oxygen species, induces DNA damage, activation of caspase 3 and caspase 8 and internucleosomal DNA fragmentation. Cell death in this model could not be prevented by antioxidants (ascorbic acid, trolox, glutathione, gallotannin or cell permeable superoxide dismutase or catalase) but could be suppressed by inhibitors of caspase-3 and -8. In conclusion, PJ-34 is a photosensitizer and PJ-34+UVA causes DNA damage and caspase-mediated cell death independently of PARP-1 inhibition.

Targeted and effective photodynamic therapy for cancer using functionalized nanomaterials

Photodynamic therapy (PDT) is an emerging, non-invasive therapeutic strategy that involves photosensitizer (PS) drugs and external light for the treatment of diseases. Despite the great progress in PS-mediated PDT, their clinical applications are still hampered by poor water solubility and tissue/cell specificity of conventional PS drugs. Therefore, great efforts have been made towards the development of nanomaterials that can tackle fundamental challenges in conventional PS drug-mediated PDT for cancer treatment. This review highlights recent advances in the development of nano-platforms, in which various functionalized organic and inorganic nanomaterials are integrated with PS drugs, for significantly enhanced efficacy and tumor-selectivity of PDT.