Femtosecond pulsed laser photodynamic therapy activates melanin and eradicates malignant melanoma.

Photodynamic therapy (PDT) relies on a series of photophysical and photochemical reactions leading to cell death. While effective for various cancers, PDT has been less successful in treating pigmented melanoma due to high light absorption by melanin. Here, this limitation is addressed by 2-photon excitation of the photosensitizer (2p-PDT) using ~100 fs pulses of near-infrared laser light. A critical role of melanin in enabling rather than hindering 2p-PDT is elucidated using pigmented and non-pigmented murine melanoma clonal cell lines in vitro. The photocytotoxicities were compared between a clinical photosensitizer (Visudyne) and a porphyrin dimer (Oxdime) with ~600-fold higher σ2p value. Unexpectedly, while the 1p-PDT responses are similar in both cell lines, 2p activation is much more effective in killing pigmented than non-pigmented cells, suggesting a dominant role of melanin 2p-PDT. The potential for clinical translational is demonstrated in a conjunctival melanoma model in vivo, where complete eradication of small tumors was achieved. This work elucidates the melanin contribution in multi-photon PDT enabling significant advancement of light-based treatments that have previously been considered unsuitable in pigmented tumors.

Effects on Colonization Factors and Mechanisms Involved in Antimicrobial Sonophotodynamic Inactivation Mediated by Curcumin.

Photodynamic (PDI) and sonodynamic (SDI) inactivation have been successfully employed as antimicrobial treatments. Moreover, sonophotodynamic inactivation (SPDI), which is the simultaneous application of PDI and SDI, has demonstrated greater effects. This study assessed the effects of PDI (PDI group), SDI (SDI group) and SPDI (SPDI group) using curcumin as a sensitizer on the metabolism, adhesion capability, biofilm formation ability and structural effects in a Staphylococcus aureus biofilm. Moreover, the production of reactive oxygen species (ROS) and the degradation spectrum of curcumin under the irradiation sources were measured. SPDI was more effective in inactivating the biofilm than PDI and SDI. All treatments reduced the adhesion ability of the bacteria: 58 ± 2%, 58 ± 1% and 71 ± 1% of the bacterial cells adhered to the polystyrene plate after the SPDI, SDI and PDI, respectively, when compared to 79 ± 1% of the untreated cells (control group). This result is probably related to the metabolism cell reduction after treatments. The metabolism of cells from the PDI group was 89 ± 1% lower than the untreated cells, while the metabolic activity of SDI and SPDI groups were 82 ± 2% and 90 ± 1% lower, respectively. Regarding the biofilm formation ability, all treatments (SPDI, SDI and PDI) reduced the total biomass. The total biomass of the PDI, SDI and SPDI groups were 26 ± 2%, 31 ± 5% and 35 ± 6% lower than the untreated biofilm (control group), respectively. Additionally, all treatments produced ROS and caused significant structural changes, reducing cells and the extracellular matrix. The light caused a greater absorbance decay of the curcumin; however, the US did not expressively alter its spectrum. Finally, SPDI had improved antimicrobial effects, and all treatments exhibited similar effects in the colonization factors evaluated.

Photobleaching Kinetics and Effect of Solvent in the Photophysical Properties of Indocyanine Green for Photodynamic Therapy.

Indocyanine green is an attractive molecule for photodynamic therapy due to its near infrared absorption, resulting in a higher tissue penetration. However, its quantum yields of the triplet and singlet state have been reported to be low and then, reactive oxygen species are unlikely to be formed. Aiming to understand the ICG role in photodynamic response, its photobleaching behavior in solution has been studied under distinct conditions of CW laser irradiation at 780 and 808 nm, oxygen saturations and solvents. Sensitizer bleaching and photoproduct formation were measured by absorption spectroscopy and analyzed using the PDT bleaching macroscopic model to extract physical parameters. ICG photobleaching occurs even at lower oxygen concentrations, indicating that the molecule presents more than one way of degradation. Photoproducts were produced even in solution of less than 4 % oxygen saturation for both solvents and excitation wavelengths. Also, the amplitude of absorption related to J-dimers was increased during irradiation, but only in 50 % PBS solution. The formation of photoproducts was enhanced in the presence of J-type dimers under low oxygen concentration, and the quantum yields of triplet and singlet states were one order of magnitude and two times higher, respectively, when compared to ICG in distilled H2 O.

Nanostructure-Driven Indocyanine Green Dimerization Generates Ultra-Stable Phototheranostics Nanoparticles.

Indocyanine green (ICG) is the only near-infrared (NIR) dye approved for clinical use. Despite its versatility in photonic applications and potential for photothermal therapy, its photobleaching hinders its application. Here we discovered a nanostructure of dimeric ICG (Nano-dICG) generated by using ICG to stabilize nanoemulsions, after which ICG enabled complete dimerization on the nanoemulsion shell, followed by J-aggregation of ICG-dimer, resulting in a narrow, red-shifted (780 nm→894 nm) and intense (≈2-fold) absorbance. Compared to ICG, Nano-dICG demonstrated superior photothermal conversion (2-fold higher), significantly reduced photodegradation (-9.6 % vs. -46.3 %), and undiminished photothermal effect (7 vs. 2 cycles) under repeated irradiations, in addition to excellent colloidal and structural stabilities. Following intravenous injection, Nano-dICG enabled real-time tracking of its delivery to mouse tumors within 24 h by photoacoustic imaging at NIR wavelength (890 nm) distinct from the endogenous signal to guide effective photothermal therapy. The unprecedented finding of nanostructure-driven ICG dimerization leads to an ultra-stable phototheranostic platform.

Revisiting the evidence of photodynamic therapy for oral potentially malignant disorders and oral squamous cell carcinoma: An overview of systematic reviews.

BACKGROUND: This study summarized the available evidence about the use of photodynamic therapy (PDT) for the management of oral potentially malignant disorders (OPMD) and oral squamous cell carcinoma (OSCC). METHODS: An overview of systematic reviews was undertaken based on the 2020 PRISMA statement. Electronic searches were performed in five databases. Studies published up to November 2022 were included. Risk of bias was assessed with the AMSTAR 2 tool. RESULTS: A total of 30 studies enrolling 9,245 individuals with OPMD (n = 7,487) or OSCC (n = 1,758) met the selection criteria. All studies examined the efficacy and/or safety of PDT. OPMD were investigated individually in 82.8% of the studies, the most common being oral lichen planus and actinic cheilitis. OSCC was addressed separately in 10.3% of the studies, while only 6.9% evaluated both OPMD and OSCC. Fourteen different types of photosensitizers were described. PDT was used according to the following setting parameters: 417-670 nm, 10-500 mW/cm2, 1.5-200 J/cm2, and 0.5-143 min. Regarding OPMD, leukoerythroplakia showed the best response rates, while oral lichen planus presented a partial or no response in nearly 75% of documented cases. A complete response was observed in 85.9% of OSCC cases, while 14.1% had no resolution. CONCLUSION: Overall, the response to PDT depended on the type of OPMD/OSCC and the parameters used. Although PDT is an emerging candidate for the treatment of OPMD and OSCC, there is heterogeneity of the methodologies used and the clinical data obtained, particularly regarding the follow-up period.

ERRATUM: Kidney decontamination during perfusion for transplantation procedure: In vitro and ex vivo viability analysis.

Organ transplantations have an increasing medical relevance. It is becoming a regular procedure with an increase in individuals waiting for organs. The increase in the number of discarded organs is mostly due to the donor's bacterial and/or viral infection. In this article, we are demonstrating the feasibility of reduction of the bacterial load in the kidney model by using Ultraviolet-C (UV-C) as a germicidal agent in circulating liquids. Using Staphylococcus aureus as a bacteria model, we were able to demonstrate that in less than 30 min of liquid circulation and associated to irradiation, the bacterial load of the perfusate Custodiol® HTK, histidine-tryptophan-ketoglutarate (solution with 5 log CFU ml-1 ), was fully eliminated. A modeling approach was created to verify the possibility of bacterial load decrease, when an organ (here, a renal experimental model) is present in the circuit, releasing a varied rate of microorganisms over time, while the solution is irradiated. Finally, we use an ex vivo model with a swine kidney, circulating in the preservation solution with a Lifeport® Kidney Transporter machine, to demonstrate that we can contaminate the organ and then promote the elimination of the microbiological load. The results show the feasibility of the technique.

Fluorescence spectroscopy for clinical transplantation liver grafts monitoring: possibilities offered by 408 nm excitation.

PURPOSE: Fluorescence spectroscopy techniques have been investigated aiming to reduce the invasiveness of methods for investigation of tissue. In transplantation procedures, it may offer the possibility of a complementary technique for the monitoring of liver grafts' conditions prior to and during the transplantation procedure stages involving cold perfusion. The objective of this study was to evaluate fluorescence spectroscopy under violet light excitation (408 nm) for the monitoring of clinical hypothermic liver transplantation procedures. METHODS: Organ grafts were monitored from before the removal of the donor's body to 1 h after the implant into the receptor's body. Fluorescence spectroscopy was assessed over five stages within these transplant stages. RESULTS: The study provided evidence of a correlation between fluorescence information collected during liver grafts transplantation and the survival of patients. CONCLUSIONS: Fluorescence spectroscopy can become a tool to monitor transplantation grafts, providing objective information for the final decision of surgeons to use organs.

Porphyrin nanoemulsion for antimicrobial photodynamic therapy: effective delivery to inactivate biofilm-related infections.

The management of biofilm-related infections is a challenge in healthcare, and antimicrobial photodynamic therapy (aPDT) is a powerful tool that has demonstrated a broad-spectrum activity. Nanotechnology has been used to increase the aPDT effectiveness by improving the photosensitizer's delivery properties. NewPS is a simple, versatile, and safe surfactant-free nanoemulsion with a porphyrin salt shell encapsulating a food-grade oil core with promising photodynamic action. This study evaluated the use of NewPS for aPDT against microorganisms in planktonic, biofilm, and in vivo models of infected wounds. First, the potential of NewPS-mediated aPDT to inactivate Streptococcus pneumoniae and Staphylococcus aureus suspensions was evaluated. Then, a series of protocols were assessed against S. aureus biofilms by means of cell viability and confocal microscopy. Finally, the best biofilm protocol was used for the treatment of S. aureus in a murine-infected wound model. A high NewPS-bacteria cell interaction was achieved since 0.5 nM and 30 J/cm2 was able to kill S. pneumoniae suspension. In the S. aureus biofilm, enhanced efficacy of NewPS-aPDT was achieved when 100 µM of NewPS was applied with longer periods of incubation at the light dose of 60 J/cm2. The best single and double-session protocol reduced 5.56 logs and 6.03 logs, respectively, homogeneous NewPS distribution, resulting in a high number of dead cells after aPDT. The in vivo model showed that one aPDT session enabled a reduction of 6 logs and faster tissue healing than the other groups. In conclusion, NewPS-aPDT may be considered a safe and effective anti-biofilm antimicrobial photosensitizer.

Photodynamic Inactivation of Microorganisms Using Semisynthetic Chlorophyll a Derivatives as Photosensitizers.

In this study, we describe the semisynthesis of cost-effective photosensitizers (PSs) derived from chlorophyll a containing different substituents and using previously described methods from the literature. We compared their structures when used in photodynamic inactivation (PDI) against Staphylococcus aureus, Escherichia coli, and Candida albicans under different conditions. The PSs containing carboxylic acids and butyl groups were highly effective against S. aureus and C. albicans following our PDI protocol. Overall, our results indicate that these nature-inspired PSs are a promising alternative to selectively inactivate microorganisms using PDI.

Discrimination of cancerous from benign pigmented skin lesions based on multispectral autofluorescence lifetime imaging dermoscopy and machine learning.

SIGNIFICANCE: Accurate early diagnosis of malignant skin lesions is critical in providing adequate and timely treatment; unfortunately, initial clinical evaluation of similar-looking benign and malignant skin lesions can result in missed diagnosis of malignant lesions and unnecessary biopsy of benign ones. AIM: To develop and validate a label-free and objective image-guided strategy for the clinical evaluation of suspicious pigmented skin lesions based on multispectral autofluorescence lifetime imaging (maFLIM) dermoscopy. APPROACH: We tested the hypothesis that maFLIM-derived autofluorescence global features can be used in machine-learning (ML) models to discriminate malignant from benign pigmented skin lesions. Clinical widefield maFLIM dermoscopy imaging of 41 benign and 19 malignant pigmented skin lesions from 30 patients were acquired prior to tissue biopsy sampling. Three different pools of global image-level maFLIM features were extracted: multispectral intensity, time-domain biexponential, and frequency-domain phasor features. The classification potential of each feature pool to discriminate benign versus malignant pigmented skin lesions was evaluated by training quadratic discriminant analysis (QDA) classification models and applying a leave-one-patient-out cross-validation strategy. RESULTS: Classification performance estimates obtained after unbiased feature selection were as follows: 68% sensitivity and 80% specificity with the phasor feature pool, 84% sensitivity, and 71% specificity with the biexponential feature pool, and 84% sensitivity and 32% specificity with the intensity feature pool. Ensemble combinations of QDA models trained with phasor and biexponential features yielded sensitivity of 84% and specificity of 90%, outperforming all other models considered. CONCLUSIONS: Simple classification ML models based on time-resolved (biexponential and phasor) autofluorescence global features extracted from maFLIM dermoscopy images have the potential to provide objective discrimination of malignant from benign pigmented lesions. ML-assisted maFLIM dermoscopy could potentially assist with the clinical evaluation of suspicious lesions and the identification of those patients benefiting the most from biopsy examination.

Lung surfactant negatively affects the photodynamic inactivation of bacteria-in vitro and molecular dynamic simulation analyses.

In the context of the rapid increase of antibiotic-resistant infections, in particular of pneumonia, antimicrobial photodynamic therapy (aPDT), the microbiological application of photodynamic therapy (PDT), comes in as a promising treatment alternative since the induced damage and resultant death are not dependent on a specific biomolecule or cellular pathway. The applicability of aPDT using the photosensitizer indocyanine green with infrared light has been successfully demonstrated for different bacterial agents in vitro, and the combination of pulmonary delivery using nebulization and external light activation has been shown to be feasible. However, there has been little progress in obtaining sufficient in vivo efficacy results. This study reports the lung surfactant as a significant suppressor of aPDT in the lungs. In vitro, the clinical surfactant Survanta® reduced the aPDT effect of indocyanine green, Photodithazine®, bacteriochlorin-trizma, and protoporphyrin IX against Streptococcus pneumoniae. The absorbance and fluorescence spectra, as well as the photobleaching profile, suggested that the decrease in efficacy is not a result of singlet oxygen quenching, while a molecular dynamics simulation showed an affinity for the polar head groups of the surfactant phospholipids that likely impacts uptake of the photosensitizers by the bacteria. Methylene blue is the exception, likely because its high water solubility confers a higher mobility when interacting with the surfactant layer. We propose that the interaction between lung surfactant and photosensitizer must be taken into account when developing pulmonary aPDT protocols.

A single session of antimicrobial photodynamic therapy does not influence the alveolar repair process in rats.

The aim of this study was to use microscopic and molecular techniques to evaluate the effects of a single session of antimicrobial photodynamic therapy (aPDT) on the alveolar repair process after tooth extraction in rats. The study sample included 84 rats divided into four groups, as follows: a) Control - untreated socket; b) Laser - socket treated using photobiomodulation; c) TBO - socket treated with topic application of the photosensitizer agent, toluidine blue O (TBO); and d) aPDT - socket treated with TBO and laser irradiation. An additional rat was used for thermal mapping during socket irradiation. The animals were euthanatized at 6, 15, and 28 days after unilateral extraction of the upper incisor. Quantitative and qualitative analyses of the connective and bone tissues, blood clot, blood vessel, and inflammatory infiltrate were performed, and real-time polymerase chain reaction was used to study the expression of genes (collagen type I, osteocalcin, alkaline phosphatase [ALP], runt-related transcription factor 2 [RUNX2], and vascular endothelial growth factor [VEGF]) involved in the bone healing process. No statistically significant differences in microscopic and molecular outcomes were observed between the groups (p > 0.05). A positive correlation was seen to exist between blood clot and VEGF (p = 0.000), and a negative correlation was observed between bone tissue and ALP (p = 0.028) and blood vessel and VEGF (p = 0.018). A single session of aPDT in the dental extraction site did not influence the alveolar repair process in rats.

Kidney decontamination during perfusion for transplantation procedure: In vitro and ex vivo viability analysis.

Organ transplantations have an increasing medical relevance. It is becoming a regular procedure with an increase in individuals waiting for organs. The increase in the number of discarded organs is mostly due to the donor bacterial and/or viral infection. In this article, we are demonstrating the feasibility of reduction of the bacterial load in kidney model by using ultraviolet-C as a germicidal agent in circulating liquids. Using Staphylococcus aureus as a bacteria model, we were able to demonstrate that in less than 30 min of liquid circulation and associated to irradiation, the bacterial load of the perfusate Custodiol HTK, histidine-tryptophan-ketoglutarate (solution with 5 log CFU mL-1 ), was fully eliminated. A modeling approach was created to verify the possibility of bacterial load decrease, when an organ (here, a renal experimental model) is present in the circuit, releasing a varied rate of microorganisms over time, while the solution is irradiated. Finally, we use an ex vivo model with swine kidney, circulating in the preservation solution with a Lifeport Kidney Transporter machine, to demonstrate that we can contaminate the organ and then promote the elimination of the microbiological load. The results show the feasibility of the technique.

Photodynamic inactivation of Streptococcus pneumoniae with external illumination at 808 nm through the ex vivo porcine thoracic cage.

Pneumonia is responsible for high mortality rates around the world, and its major treatment is based on antibiotic treatment. Antimicrobial resistance has been increasing in the last years, resulting in relevant public health concern. A promising alternative for pneumonia is antimicrobial photodynamic therapy. The purpose of this study was to investigate whether 808 nm wavelength is able to be transmitted through the biological tissues of the thoracic wall and be delivered in enough energy inside the cage to activate indocyanine green and promote photodynamic response. A light source panel was developed composed of 200 lasers centered at 808 nm with an irradiance of 77.8 ± 10.0 mW/cm2 and tested in an ex vivo thoracic cage model. Monte Carlo simulations were used to understand the photon migration through all the tissues at the thoracic wall. It was observed that tissues responsible for the major absorption of photons are the skin and subcutaneous fat. Experimental measurement of the irradiance was obtained after the light pass-through ex vivo pig thoracic cage, obtaining 3% to 5% of the emitted irradiance. Finally, it was observed that even with 3% of the initial irradiance, a 99.9% reduction of the Streptococcus pneumoniae was successfully achieved after 42.6 minutes of irradiation.

Effects of methylene blue and curcumin photosensitizers on the color stability of endodontically treated intraradicular dentin.

BACKGROUND: Photodynamic therapy with photosensitizers can reduce the microbial load. However, few studies have evaluated the effects of photosensitizers on the color stability of endodontically treated intraradicular dentin. This in vitro study investigated the effects of methylene blue and curcumin photosensitizers used in photodynamic therapy on the color stability of intraradicular dentin. METHODS: Sixty human incisors were divided into three experimental groups according to the photosensitizer solutions used and their concentrations: methylene blue (25 mg/L), curcumin (1000 mg/L), and curcumin (1500 mg/L). The color stability of endodontically treated intraradicular dentin was evaluated using a portable reflectance spectrophotometer before and after the samples been storage in 2 mL of the photosensitizer solutions during 5 min (n = 20). Color stability data were subjected to a normality test, and statistical analysis was performed using the one-way analysis of variance and Tukey least significant difference test (α = 0.05). RESULTS: Samples treated with 25 mg/L methylene blue photosensitizer showed a higher level of color alteration than those stored in 1000 mg/L curcumin (p = .03322). However, there was no significant difference in the color alteration profiles between the samples treated with 25 mg/L methylene blue and 1500 mg/L curcumin (p = .36428). Furthermore, there was no difference in the color alteration profiles between the dentin samples immersed in 1000 mg/L and 1500 mg/L curcumin photosensitizer solutions (p = .45321). CONCLUSIONS: Methylene blue and curcumin photosensitizers influenced the color stability of endodontically treated intraradicular dentin, and this color alteration exceeded the clinical acceptability threshold. Samples treated with 25 mg/L methylene blue showed the highest level of color alteration.

A new photodynamic therapy protocol for nodular basal cell carcinoma treatment: Effectiveness and long-term follow-up.

BACKGROUND: Photodynamic therapy (PDT) has been reported as an excellent option for the treatment of small nodular basal cell carcinomas (nBCC). The standard protocol consists of two sessions, one week apart. Sometimes, returning to the hospital after one week can be impractical for elderly patients, due to comorbidities and mobility issues. Therefore, a new technique performed in one day could be superior for those patients. OBJECTIVE: Evaluate the effectiveness of a PDT Single-visit protocol comparing to the standard protocol, as well as pain and long-term recurrence-free follow-up for nBCC. METHODS: A total of 120 nBCC were treated through a Standard PDT protocol(two sessions, one week apart), and 120 nBCC were treated through a Single-visit PDT(two sessions in one day). A 30-day-after biopsy was performed in order to evaluate the results after the treatment. The lesions that had successful treatment were clinically and dermoscopically evaluated every 6 months up to 60 months. The pain score was compared between the groups(assessed every 3 min during PDT). RESULTS: A complete response at 30-days-after PDT biopsy was observed in 85% of Standard PDT and in 93.3% of Single-visit PDT. Regarding the pain during the illumination, less pain was observed during the second session of the Single-visit PDT. The recurrence-free follow up showed, after 60 months, an 69.0% cumulative probability of recurrence-free for Standard PDT and 80.6% for Single-visit PDT. CONCLUSIONS: The suggested Single-visit PDT protocol resulted in better outcomes at 30-day-after PDT biopsy and in lower recurrence rates than the Standard PDT protocol. A more comfortable and more efficient treatment was offered for the patients, with lower pain.

Fluorescence spectroscopy for clinical transplantation liver grafts monitoring: possibilities offered by 408 nm excitation

Purpose: Fluorescence spectroscopy techniques have been investigated aiming to reduce the invasiveness of methods for investigation of tissue. In transplantation procedures, it may offer the possibility of a complementary technique for the monitoring of liver grafts' conditions prior to and during the transplantation procedure stages involving cold perfusion. The objective of this study was to evaluate fluorescence spectroscopy under violet light excitation (408 nm) for the monitoring of clinical hypothermic liver transplantation procedures. Methods: Organ grafts were monitored from before the removal of the donor's body to 1 h after the implant into the receptor's body. Fluorescence spectroscopy was assessed over five stages within these transplant stages. Results: The study provided evidence of a correlation between fluorescence information collected during liver grafts transplantation and the survival of patients. Conclusions: Fluorescence spectroscopy can become a tool to monitor transplantation grafts, providing objective information for the final decision of surgeons to use organs.

A single session of antimicrobial photodynamic therapy does not influence the alveolar repair process in rats

Abstract: The aim of this study was to use microscopic and molecular techniques to evaluate the effects of a single session of antimicrobial photodynamic therapy (aPDT) on the alveolar repair process after tooth extraction in rats. The study sample included 84 rats divided into four groups, as follows: a) Control - untreated socket; b) Laser - socket treated using photobiomodulation; c) TBO - socket treated with topic application of the photosensitizer agent, toluidine blue O (TBO); and d) aPDT - socket treated with TBO and laser irradiation. An additional rat was used for thermal mapping during socket irradiation. The animals were euthanatized at 6, 15, and 28 days after unilateral extraction of the upper incisor. Quantitative and qualitative analyses of the connective and bone tissues, blood clot, blood vessel, and inflammatory infiltrate were performed, and real-time polymerase chain reaction was used to study the expression of genes (collagen type I, osteocalcin, alkaline phosphatase [ALP], runt-related transcription factor 2 [RUNX2], and vascular endothelial growth factor [VEGF]) involved in the bone healing process. No statistically significant differences in microscopic and molecular outcomes were observed between the groups (p > 0.05). A positive correlation was seen to exist between blood clot and VEGF (p = 0.000), and a negative correlation was observed between bone tissue and ALP (p = 0.028) and blood vessel and VEGF (p = 0.018). A single session of aPDT in the dental extraction site did not influence the alveolar repair process in rats.

Photodynamic therapy with a new bacteriochlorin derivative: Characterization and in vitro studies.

Photodynamic therapy presents a therapeutic choice that can be utilized to treat diverse neoplasms. In this technique, the critical element is a photosensitive molecule that absorbs light energy and transfers it to molecular oxygen or biological molecules to form reactive oxygen species, thus inducing irreversible damage to target cells and ultimately leading to cell death. Bacteriochlorin derivatives are employed as photosensitizers (PSs), possessing light-absorbing capacity in the near-infrared region. The objective of this study was to prepare a semi-synthetic bacteriochlorin from Rhodopseudomonas faecalis and adding Trizma® to improve solubility. Cell viability tests, flow cytometry (apoptotic and necrotic cells were identified by Annexin V and propidium iodide), and confocal microscopy were used to evaluate the photoactivity of bacteriochlorin-Trizma (Bchl-T) in fibroblast (HFF-1-control cells) and breast cancer (MCF-7 cells-target cells) cells. At concentrations above 0.5 µM, Bchl-T demonstrated 80 % cell death, presenting the highest PS interaction (via fluorescence microscopy) with lysosomes, mitochondria, and the endoplasmic reticulum; the cell death type was revealed as apoptosis (via cytometry). Our findings indicated the suitability of Bchl-T for future application in photodynamic therapy against cancer cells by inducing apoptosis.

Features of third generation photosensitizers used in anticancer photodynamic therapy: Review.

Cancer remains a main public health issue and the second cause of mortality worldwide. Photodynamic therapy is a clinically approved therapeutic option. Effective photodynamic therapy induces cancer damage and death through a multifactorial manner including reactive oxygen species-mediated damage and killing, vasculature damage, and immune defense activation. Anticancer efficiency depends on the improvement of photosensitizers drugs used in photodynamic therapy, their selectivity, enhanced photoproduction of reactive species, absorption at near-infrared spectrum, and drug-delivery strategies. Both experimental and clinical studies using first- and second-generation photosensitizers had pointed out the need for developing improved photosensitizers for photodynamic applications and achieving better therapeutic outcomes. Bioconjugation and encapsulation with targeting moieties appear as a main strategies for the development of photosensitizers from their precursors. Factors influencing cellular biodistribution and uptake are briefly discussed, as well as their roles as cancer diagnostic and therapeutic (theranostics) agents. The two-photon photodynamic approach using third-generation photosensitizers is present as an attempt in treating deeper tumors. Although significant advances had been made over the last decade, the development of next-generation photosensitizers is still mainly in the developmental stage.