Self-reported and self-facilitated theranostic oxygen nano-economizer for precise and hypoxia alleviation-potentiated photodynamic therapy.

Photodynamic therapy (PDT) has been extensively investigated for cancer treatment by virtue of singlet oxygen-induced oxidative damage to tumors. Nevertheless, the therapeutic efficiency of PDT is still limited by the low singlet oxygen yield attributed to the improper irradiation duration and the tumor hypoxic microenvironment. To tackle these challenges, we elaborately design a theranostic oxygen nano-economizer to self-report the optimal irradiation duration and alleviate tumor hypoxia simultaneously, which is engineered by fluorescent 9,10-anthracenyl bis (benzoic acid) (DPA)-MOF, tetrakis (4-carboxyphenyl) porphyrin (TCPP), triphenyl phosphine (TPP) and redox-responsive lipid-PEG (DSPE-SS-PEG2k). Upon laser irradiation, the fluorescence of DPA-MOF could be quenched, thereby self-reporting the optimal irradiation duration for sufficient PDT. The decoration of DSPE-SS-PEG2k and TPP endows the theranostic oxygen nano-economizer with a tumor-specific response and mitochondrial targeting capability, respectively. Notably, singlet oxygen generated from TCPP reduces oxygen consumption by disrupting the entire oxidative phosphorylation (OXPHOS) pathway in the mitochondria of tumor cells, further improving the level of singlet oxygen in a self-facilitated manner for hypoxia alleviation-potentiated PDT. As expected, such a self-reported and self-facilitated theranostic oxygen nano-economizer exhibits potent antitumor activity in the 4T1 tumor-bearing mouse model. This study offers a theranostic paradigm for precise and hypoxia alleviation-potentiated cancer therapy.

The biological activities of 5,15-diaryl-10,20-dihalogeno porphyrins for photodynamic therapy.

PURPOSE: Esophageal cancer is the most common gastrointestinal tumor and is difficult to be eradicated with conventional treatment. Porphyrin-based photosensitizers (PSs) mediated photodynamic therapy (PDT) could kill tumor cells with less damage to normal cells. As the most widely used porphyrin-based photosensitizer in clinics, Photofrin II has excellent anti-tumor effect. However, it has some disadvantages such as weak absorption at near infrared region, the complexity of components and prolonged skin photosensitivity. Here series novel 5,15-diaryl-10,20-dihalogeno porphyrin derivatives were afforded and evaluated to develop more effective and safer photosensitizers for tumor therapy. METHODS: The photophysical properties and singlet oxygen generation rates of 5,15-diaryl-10,20-dihalogeno porphyrins (I1-6, II1-4) were tested. The cytotoxicity of I1-6 and II1-4 were measured by MTT assay. The pathway of cell death was studied by flow cytometry. In vivo photodynamic efficacy of I3 and II2-4 in Eca-109 tumor-bearing BABL/c nude mice were measured and histopathological analysis were examined. RESULTS: 5,15-Diaryl-10,20-dihalogeno porphyrins I1-6 and II1-4 were synthesized. The longest absorption wavelength of these halogenated porphyrins (λmax = 660 nm) displayed a red shift around 30 nm compared to the unhalogenated porphyrins PS1 (λmax = 630 nm). The singlet oxygen generation rates of I1-6 and II1-4 were significantly higher than PS1 and HMME. All PSs mediated PDT showed obvious cytotoxic effect against Eca-109 cells compared to HMME in vitro and in vivo. Among these PSs, II4 exhibited appropriate absorption in the phototherapeutic window, higher 1O2 generation rate (k = 0.0061 s-1), the strongest phototoxicity (IC50 = 0.4 µM), lower dark toxicity, high generation of intracellular ROS in Eca-109 cells and excellent photodynamic anti-tumor efficacy in vivo. Besides, cell necrosis was induced by compound II4 mediated PDT. CONCLUSION: All new compounds have obvious photodynamic anti-esophageal cancer effects. Among them, the photosensitizer II4 showed excellent efficacy in vitro and in vivo, which has the potential to become a photodynamic anti-tumor drug.

Activity-Based Photosensitizers with Optimized Triplet State Characteristics Toward Cancer Cell Selective and Image Guided Photodynamic Therapy.

Activity-based theranostic photosensitizers are highly attractive in photodynamic therapy as they offer enhanced therapeutic outcome on cancer cells with an imaging opportunity at the same time. However, photosensitizers (PS) cores that can be easily converted to activity-based photosensitizers (aPSs) are still quite limited in the literature. In this study, we modified the dicyanomethylene-4H-chromene (DCM) core with a heavy iodine atom to get two different PSs (DCMO-I, I-DCMO-Cl) that can be further converted to aPS after simple modifications. The effect of iodine positioning on singlet oxygen generation capacity was also evaluated through computational studies. DCMO-I showed better performance in solution experiments and further proved to be a promising phototheranostic scaffold via cell culture studies. Later, a cysteine (Cys) activatable PS based on the DCMO-I core (DCMO-I-Cys) was developed, which induced selective photocytotoxicity along with a fluorescence turn-on response in Cys rich cancer cells.

Gemini Surfactant Mediated Catansomes for Enhanced Singlet Oxygen Generation of Rose Bengal and Their Phototoxicity against Cancer Cells.

Photodynamic therapy (PDT) is an innovative technique for cancer treatment with minimal side effects, based on the use of a photosensitizer, oxygen, and light. Photosensitizers (PSs) have several limitations, that may limit their clinical use, like poor solubilization, self-aggregation, and lack of specific targeting, which can be addressed with the use of nanomaterials. Herein, a unique type of catansomes (CaSs) was prepared using a gemini imidazolium-based surfactant (1,3-bis[(3-octadecyl-1-imidazolio)methyl]benzene dibromide (GBIB) and a double chain surfactant, diaoctyl sodium sulfosuccinate or Aerosol OT (AOT). The formation of CaS GBIB/AOT was optimized in various ethanol/water (E/W) solvent ratios by employing a facile, quick, and most reliable solution-solution mixing method. The CaS was characterized by dynamic light scattering (DLS) and field emission gun scanning electron microscopy (FEG-SEM) techniques. The experimental results reveal that stable CaSs with a spherical shape were obtained at lower concentration (100 µM). Rose Bengal (RB), a PS of the xanthene family, was incorporated into these prepared CaSs, as proven by fluorescence spectroscopy, UV-visible absorption spectroscopy, and confocal laser scanning microscopy. Singlet oxygen (1O2) generation studies revealed the relevant role of the E/W solvent ratio as there was a 4-fold boost in the 1O2 production for GBIB/AOT in E/W = 50:50 and around 3-fold in E/W = 30:70. Also, the GBIB-rich 80:20 fraction was more efficient in increasing the 1O2 generation as compared to the AOT rich fraction (20:80). Further, their phototoxicity was tested in a water-rich solvent ratio (E/W = 30:70) against MCF-7 cells. Upon irradiation with a 532 nm laser (50 mW) for 5 min, RB@GBIB/AOT(20:80) fraction caused 50% decrease in the metabolic activity of MCF-7 cells, and RB@GBIB/AOT(80:20) fraction produced a maximum 85% decrease in cell viability. Furthermore, the enhancement in intracellular 1O2 generation by RB@GBIB/AOT, as compared to pure RB, was confirmed with singlet oxygen sensor green (SOSG). This new type of CaS based on gemini surfactants exhibiting a large amount of 1O2 generation, holds great interest for several applications, such as use in photomedicine in future.

Dimensional Reduction Enhances Photodynamic Therapy of Metal-Organic Nanophotosensitizers.

Herein we report that dimensional reduction from three-dimensional nanoscale metal-organic frameworks (nMOFs) to two-dimensional nanoscale metal-organic layers (nMOLs) increases the frequency of encounters between photosensitizers and oxygen and facilitates the diffusion of singlet oxygen from the nMOL to significantly enhance photodynamic therapy. The nMOFs and nMOLs share the same M12-oxo (M = Zr, Hf) secondary building units and 5,15-di-p-benzoatoporphyrin (DBP) ligands but exhibit three-dimensional and two-dimensional topologies, respectively. Molecular dynamics simulations and experimental studies revealed that the nMOLs with a monolayer morphology enhanced the generation of reactive oxygen species and exhibited over an order of magnitude higher cytotoxicity over the nMOFs. In a mouse model of triple-negative breast cancer, Hf-DBP nMOL showed 49.1% more tumor inhibition, an 80% higher cure rate, and 16.3-fold lower metastasis potential than Hf-DBP nMOF.

Photodecaging of a Mitochondria-Localized Iridium(III) Endoperoxide Complex for Two-Photon Photoactivated Therapy under Hypoxia.

Despite the clinical success of photodynamic therapy (PDT), the application of this medical technique is intrinsically limited by the low oxygen concentrations found in cancer tumors, hampering the production of therapeutically necessary singlet oxygen (1O2). To overcome this limitation, we report on a novel mitochondria-localized iridium(III) endoperoxide prodrug (2-O-IrAn), which, upon two-photon irradiation in NIR, synergistically releases a highly cytotoxic iridium(III) complex (2-IrAn), singlet oxygen, and an alkoxy radical. 2-O-IrAn was found to be highly (photo-)toxic in hypoxic tumor cells and multicellular tumor spheroids (MCTS) in the nanomolar range. To provide cancer selectivity and improve the pharmacological properties of 2-O-IrAn, it was encapsulated into a biotin-functionalized polymer. The generated nanoparticles were found to nearly fully eradicate the tumor inside a mouse model within a single treatment. This study presents, to the best of our knowledge, the first example of an iridium(III)-based endoperoxide prodrug for synergistic photodynamic therapy/photoactivated chemotherapy, opening up new avenues for the treatment of hypoxic tumors.

Construction and evaluation of curcumin upconversion nanocarriers decorated with MnO2 for tumor photodynamic therapy.

The limited tissue penetration depth and tumor hypoxic microenvironment have become the two pivotal obstacles that alleviate the antineoplastic efficacy in tumor photodynamic therapy (PDT). In the research, MnO2-decorated upconversion nanoparticles (UCSMn) have been designed to generate certain oxygen within the solid tumor, and also increase the light penetrating depth due to the optical conversion ability derived from upconversion nanoparticles. Furthermore, upconversion nanoparticles as the inner core are coated by mesoporous silica for the loading of curcumin as photosensitizer and chemotherapeutics, and then a MnO2 shell is proceeding to grow via redox method. When reaching the tumor tissue, the MnO2 nanoshells of UCSMn could be rapidly degraded into manganese ions (Mn2+) owing to the reaction with H2O2 in acidic tumor microenvironment, meanwhile producing oxygen and facilitating curcumin release. Once the tumor is illuminated by 980 nm light, the upconversion nanoparticles can transform the infrared light to visible light of 450 nm and 475.5 nm, which can be efficiently absorbed by curcumin, and then produce singlet oxygen to induce tumor cell apoptosis. Curcumin played a dual role which can not only be acted as a photosensitizer, but also a chemotherapeutic agent to further reinforce the antitumor activity. In short, the intelligent nanostructure has the potential to overcome the above-mentioned shortcomings existed in PDT and eventually do work well in the hypoxia tumors. MnO2-decorated upconversion nanoparticle to solve the tissue penetration and tumor hypoxic microenvironment for tumor photodynamic therapy.

Singlet oxygen formation during accelerated and hyperaccelerated corneal cross-linking: in vitro study.

BACKGROUND: To evaluate the singlet oxygen (1O2) production of oxygen assisted %0.1 riboflavin and ultraviolet-A (UVA) crosslinking therapy (with and without oxygen assistance), in combination with standard, accelerated and hyper-accelerated procedures via an important quantitive marker of 1O2 which is the photo-oxidation of 1,3 diphenylisobenzofuran (DPBF). METHODS: %0.1 riboflavin-containing wells were irradiated with UVA light (365-nm wavelength) with or without 2-4-6-8 L/min oxygen flow assistance. Measurements of decrease in absorbance of DPBF were made in 30 mW (hyper-accelerated), 9 mW (accelerated), and 3 mW UV-A (standard) applications, and with additional 2-4-6-8 L/min oxygen flow in 30 mW and 2 L/min oxygen flow in 9 mW. A total of 8 different UV-A irradiance with and without oxygen supplementation groups were formed. RESULTS: 2 L/min oxygen assisted accelerated UV-A irradiance group has shown a greater decrease in DPBF absorbance compared to Dresden protocol. (p = 0.014) Also, Dresden protocol has shown a greater decrease in DPBF compared to all groups except accelerated crosslinking with 2 L/min oxygen. (p < 0.001) Oxygen assisted hyper-accelerated crosslinking groups were showed greater reduction in DPBF absorbance compared to standard crosslinking without oxygen groups. (p < 0.001). CONCLUSION: Oxygen supplementation may increase the singlet oxygen generation to the similar levels of Dresden Protocol's in accelerated group. Also, more singlet oxygen generation with oxygen supplementation compared to standard UV-A application might be considered to be promising in terms of shortening the crosslinking therapy.

Highly Efficient Near-Infrared Photosensitizers with Aggregation-Induced Emission Characteristics: Rational Molecular Design and Photodynamic Cancer Cell Ablation.

Photosensitizers (PSs) that play a decisive role in effective photodynamic therapy (PDT) have attracted great research interest. PSs with aggregation-induced emission (AIE) characteristics could overcome the deficiencies of traditional PSs that usually suffer from the aggregation-caused fluorescence quenching (ACQ) effect in applications and show enhanced emission and high singlet oxygen (1O2) generation efficiency in aggregates; therefore, they are outstanding candidates for imaging-guided PDT, and the development of AIE PSs with both excellent photophysical properties and 1O2 generation ability is highly desirable. Herein, three AIE fluorogens (AIEgens), BtM, ThM, and NaM, with a donor-π-acceptor (D-π-A) structure were designed and synthesized, and the photosensitizing ability was adjusted by π-linker engineering. All of the three AIEgens showed excellent photostability and high molar absorption coefficients, and their emission edges were extended to the near-infrared (NIR) region, with peaks at 681, 678, and 638 nm, respectively. NaM demonstrated the smallest ΔES1-T1, which was ascribed to its better separation degree of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The AIEgens were fabricated into nanoparticles (NPs) by amphipathic mPEG3000-DSPE encapsulating, and thus the obtained NaM NPs exhibited the best 1O2 generation efficiency under white light irradiation, which was almost 3 times that of the renowned PS rose bengal (RB). Furthermore, under white light irradiation, the cell killing efficiency of NaM NPs was also much better than those of the other two AIE PSs and RB. Therefore, NaM NPs revealed great potential to treat superficial diseases as a PS for PDT.

An Oxidation-Enhanced Magnetic Resonance Imaging Probe for Visual and Specific Detection of Singlet Oxygen Generated in Photodynamic Cancer Therapy In Vivo.

Singlet oxygen is regarded as the primary cytotoxic agent in cancer photodynamic therapy (PDT). Despite the advances in optical methods to image singlet oxygen, it remains a challenge for in vivo application due to the limited tissue penetration depth of light. Up to date, no singlet oxygen-specific magnetic resonance imaging (MRI) probe has been reported. Herein, a T2 -weighted MRI probe is reported to visually detect singlet oxygen generated in PDT in vitro and in vivo. The MRI probe Ce6/Fe3 O4 -M is constructed by co-encapsulation of photosensitizer Ce6 and Fe3 O4 nanoparticles in mPEG2000 -TK-C16 micelles. Thioketal (TK) linker in the probe is highly sensitive to singlet oxygen, but lowly sensitive to other reactive oxygen species (ROS) existing in physiological and pathological environments. Singlet oxygen, generated with light irradiation, triggers the cleavage of TK, which leads to loss of surface polyethylene glycol, increment of the hydrophobicity, and aggregation of Fe3 O4 nanoparticles. Subsequently, negatively enhanced T2 -weighted MRI signal is obtained for visual detection of singlet oxygen in the solution, cancer cells, and in vivo. This oxidation responsive MRI probe is expected to hold great promise in evaluating the ability of photosensitizers to generate singlet oxygen and in predicting the therapeutic efficacies of PDT in vivo.

Energy-Free, Singlet Oxygen-Based Chemodynamic Therapy for Selective Tumor Treatment without Dark Toxicity.

Traditional singlet oxygen-based antitumor therapies have been burdened with the necessity of external energy (e.g., light and ultrasound) and harmful dark toxicity. Ascorbate at the pharmacological concentration could accumulate hydrogen peroxide only in the tumor site. It is postulated that the concurrent delivery of ascorbate and nanoparticulate hypochlorous ion (ClO- ) could produce singlet oxygen at the tumor site as an energy-free, tumor-specific therapy. The ClO- is loaded in a hybrid core-shell nanocarrier consisting of a zeolitic imidazolate framework and amphiphilic poloxamer 188. Intracellular singlet oxygen production is verified in 4T1 cells by the cooperation between hybrid nanocarriers and ascorbate, which induces significant apoptotic cell death. Upon intravenous nanocarriers delivery plus intraperitoneal ascorbate administration to xenograft mice, the in vivo antitumor efficacy of this cooperative nanomedicine is demonstrated without noticeable side-effects. This work demonstrates a proof-of-concept of singlet oxygen-based chemodynamic therapy for selective tumor eradication, which produces a novel trigger-free, singlet oxygen-based cancer therapy without the side effects of traditional photodynamic and sonodynamic therapy.

Light-Controlled Generation of Singlet Oxygen within a Discrete Dual-Stage Metallacycle for Cancer Therapy.

Noninvasive control over the reversible generation of singlet oxygen (1O2) has found the practical significance in benefiting photodynamic therapy. In this study, we developed a new dual-stage metallacycle (M) by using a photosensitizer and photochromic switch as the functional building blocks, which enables the noninvasive "off-on" switching of 1O2 generation through the efficient intramolecular energy transfer. Due to the proximal placement of the functional entities within the well-defined metallacyclic scaffold, 1O2 generation in the ring-closed form state of the photochromic switch (C-M) is quenched by photoinduced energy transfer, whereas the generation of 1O2 in the ring-open form state (O-M) is activated upon light irradiation. More interestingly, the metallacycle-loaded nanoparticles with relatively high stability and water solubility were prepared, which allow for the delivery of metallacycles to cancer cells via endocytosis. Their theranostic potential has been systematically investigated both in vitro and in vivo. Under the light irradiation, the designed ring-open form nanoparticles (O-NPs) show remarkable higher cytotoxicity against cancer cells compared to the ring-closed form nanoparticles (C-NPs). In vivo experiments also revealed that tumors can be very efficiently eliminated by the designed nanoparticles under light irradiation with the ability to regulate in vivo generation of singlet oxygen. All these results demonstrated that the supramolecular coordination complexes with a dual-stage state provide a highly efficient nanoplatform for noninvasive control over the reversible generation of 1O2, thus allowing for their promising applications in tumor treatment and beyond.

Cryodesiccation-driven crystallization preparation approach for zinc(II)-phthalocyanine nanodots in cancer photodynamic therapy and photoacoustic imaging.

Multifunctional nanodots represent an emerging platform for overcoming the delivery challenges of poorly water-soluble drugs for use in the diagnosis and treatment of cancer. The authors describe the preparation of nanocrystallites composed of the water-insoluble photosensitizer zinc(II)-phthalocyanine in the form of nanodots by applying a cryodesiccation-driven crystallization approach. Modification of the surface of the nanodots with Pluronic F127 and folic acid endows them with excellent water solubility and stealth properties in blood. Under near-infrared (NIR) photoexcitation at 808 nm, the nanodots are shown to produce singlet oxygen, which is widely used in photodynamic therapy of cancer. The nanodots exhibit strong NIR absorbance at 808 nm and can be used as a non-toxic contrast agent for photoacoustic imaging of tissue. Graphical abstract Schematic presentation of the preparation of ZnPcNDs by droplet-confined/cryodesiccation-driven crystallization.

Direct 1O2 optical excitation: A tool for redox biology.

Molecular oxygen (O2) displays very interesting properties. Its first excited state, commonly known as singlet oxygen (1O2), is one of the so-called Reactive Oxygen Species (ROS). It has been implicated in many redox processes in biological systems. For many decades its role has been that of a deleterious chemical species, although very positive clinical applications in the Photodynamic Therapy of cancer (PDT) have been reported. More recently, many ROS, and also 1O2, are in the spotlight because of their role in physiological signaling, like cell proliferation or tissue regeneration. However, there are methodological shortcomings to properly assess the role of 1O2 in redox biology with classical generation procedures. In this review the direct optical excitation of O2 to produce 1O2 will be introduced, in order to present its main advantages and drawbacks for biological studies. This photonic approach can provide with many interesting possibilities to understand and put to use ROS in redox signaling and in the biomedical field.

Highly efficient hierarchical micelles integrating photothermal therapy and singlet oxygen-synergized chemotherapy for cancer eradication.

It is highly desirable to develop theranostic nanoparticles for achieving cancer imaging with enhanced contrast and simultaneously multimodal synergistic therapy. Herein, we report a theranostic micelle system hierarchically assembling cyanine dye (indocyanine green) and chemotherapeutic compound (doxorubicin) (I/D-Micelles) as a novel theranostic platform with high drug loading, good stability and enhanced cellular uptake via clathrin-mediated endocytosis. I/D-Micelles exhibit the multiple functionalities including near-infrared fluorescence (NIRF), hyperthermia and intracellular singlet oxygen from indocyanine green, and simultaneous cytotoxicity from doxorubicin. Upon photoirradiation, I/D-Micelles can induce NIRF imaging, acute photothermal therapy via hyperthermia and simultaneous synergistic chemotherapy via singlet oxygen-triggered disruption of lysosomal membranes, eventually leading to enhanced NIRF imaging and superior tumor eradication without any re-growth. Our results suggest that the hierarchical micelles can act as a superior theranostic platform for cancer imaging and multimodal synergistic therapy.

Bactericidal action of photogenerated singlet oxygen from photosensitizers used in plaque disclosing agents.

BACKGROUND: Photodynamic therapy (PDT) has been suggested as an efficient clinical approach for the treatment of dental plaque in the field of dental care. In PDT, once the photosensitizer is irradiated with light of a specific wavelength, it transfers the excitation energy to molecular oxygen, which gives rise to singlet oxygen. METHODOLOGY/PRINCIPAL FINDINGS: Since plaque disclosing agents usually contain photosensitizers such as rose bengal, erythrosine, and phloxine, they could be used for PTD upon photoactivation. The aim of the present study is to compare the ability of these three photosensitizers to produce singlet oxygen in relation to their bactericidal activity. The generation rates of singlet oxygen determined by applying an electron spin resonance technique were in the order phloxine > erythrosine ≒ rose bengal. On the other hand, rose bengal showed the highest bactericidal activity against Streptococcus mutans, a major causative pathogen of caries, followed by erythrosine and phloxine, both of which showed activity similar to each other. One of the reasons for the discrepancy between the singlet oxygen generating ability and bactericidal activity was the incorporation efficiency of the photosensitizers into the bacterial cells. The incorporation rate of rose bengal was the highest among the three photosensitizers examined in the present study, likely leading to the highest bactericidal activity. Meanwhile, the addition of L-histidine, a singlet oxygen quencher, cancelled the bactericidal activity of any of the three photoactivated photosensitizers, proving that singlet oxygen was responsible for the bactericidal action. CONCLUSIONS: It is strongly suggested that rose bengal is a suitable photosensitizer for the plaque disclosing agents as compared to the other two photosensitizers, phloxine and erythrosine, when used for PDT.

A clinical evaluation of the efficacy and safety of singlet oxygen in cleansing and disinfecting stagnating wounds.

OBJECTIVE: This cohort study evaluated the clinical efficacy of singlet oxygen, ActiMaris (AM) a hypertonic (3%) ionised (pH 9.8) sea water solution. It was assumed that when used for wound cleansing, disinfection and the reduction of inflammation, AM would be safe and effective. METHOD: Between May 2008 and May 2009, ambulant patients presenting at one of four wound healing centres were included in the study. Patients had critically colonised and/or infected, malodorous wounds, covered with slough/fibrin or wounds showing inflammation of the periwound skin. Wounds were assessed in terms of percentage changes in fibrin, slough and granulation tissue, they were assessed clinically and high resolution digital photographs were scored by a physician who was blinded to treatment allocation. Results were compared at baseline (week 0) and following 42 days of AM treatment (week 6). RESULTS: Seventy-three patients were included in the analysis. Dressing changes were at 2-day intervals on average, and the median treatment period was 46.04 days (range: 3-197). At 42 days, 33% (n=24) of included wounds had healed, 57% (n=42) had improved and 10% (n=7) remained stagnant. Cleansing and wound disinfection with AM was effective. In 31 patients (42%) wounds had showed clinical signs and symptoms of critical colonisation and/or infection at day 0, whereas at day 42 the infection was completely eradicated. Inflammation was reduced in 60% (n=44) of cases and patients did not report pain or discomfort when using AM. CONCLUSION: The use of singlet oxygen was shown to be safe and the results of this study indicate AM to be useful for wound cleansing, disinfection, reducing inflammation and promoting wound healing. CONFLICT OF INTEREST: The centres were supplied with the study product by the sponsor. The authors have no financial interest in writing this article.