Photodynamic Therapy Activity Research Articles

Oxygen saturation imaging as a useful tool for visualizing the mode of action of photodynamic therapy for esophageal cancer.

Background and aimsOxygen saturation (OS) imaging is a novel technique that directly measures and visualizes the tissue oxygen saturation at the surface of the GI tract. Our purpose was to evaluate the ability of OS imaging to visualize the action mode of photodynamic therapy (PDT).MethodsEight patients with local recurrence after chemoradiotherapy for esophageal cancer were enrolled. OS imaging observation was performed before PDT, after 100 J/cm2 illumination and illumination completion, and on the second day.ResultsOS imaging showed an extreme change in the hypoxic state in the illuminated area, although the change was near invisible on white-light imaging. The median tissue oxygen saturation value at the tumor lesion was 61.5% (range, 36%-91%) before PDT and significantly decreased immediately after illumination: 11% (range, 0%-57%) after 100 J/cm2 illumination, 1% (range, 0%-6%) at PDT completion, and 2% (range, 0%-12%) on the second day.ConclusionsOS imaging could be a useful tool to visualize changes after PDT.

Designing Synthetic Glycosylated Photosensitizers for Photodynamic Therapy

Abstract In recent years, photodynamic therapy (PDT) has been approved for treating various medical conditions, including pre-cancer and cancer. PDT is a treatment that employs particular drugs, called ‘photosensitizers (PS)' which work along with the specific light source and local oxygen in the treated area. The significant benefits of PDT are minimally invasive procedures while delivering high accuracy in targeting areas. In the past two decades, cancer researchers have conducted remarkable studies developing photosensitizers that have enhanced our understanding in the fields of cancer biology and its genetics. However, several limitations of PDT have been noticed, such as skin photosensitivity and inefficient PDT efficacy under hypoxia conditions. Besides this, the stability and solubility of photosensitizer in aqueous solution is another crucial factor for efficient PDT activity. The glycosylation of photosensitizers would be a potential strategy to overcome the limitations of PDT described above. Thus, this mini-review is focused primarily on the molecular design and biological applications of glycosylated photosensitizers, which can provide new ways of designing them.

Solvent mixing generating air bubbles as a template for polydopamine nanobowl fabrication: Underlying mechanism, nanomotor assembly and application in cancer treatment

Fabrication of hollow or bowl-like materials using gas bubbles as templates is an attractive technique. However, it is challenging to develop simple and mild methods that produce nanosized and homogeneous gas bubble templates. Herein, excess air could outgas in the form of bubbles by mixing water and water-soluble solvents in the proper proportion. And polydopamine (PDA) nanobowls are fabricated using these bubble templates. Furthermore, Mn(CO)5Br (COMn, gas fuel generator) is loaded on PDA nanobowls to form a nanomotor to carry zinc phthalocyanine (ZnPc, photosensitive drug) (denoted PCZN), which can migrate efficiently in cancer cells. Singlet oxygen (1O2), the primary cytotoxic reactive oxygen species (ROS) in photodynamic therapy (PDT), has an extremely short lifetime (<0.04 µs) and action radius (<20 nm), which limits its influence range to strictly around its production site. The movement of PCZNs can enlarge the ZnPc diffusion range, expand the 1O2 reach, and improve the PDT activity. In addition, PCZNs have multiple functions, including tumor vasodilatation to promote nanomedicine accumulation, tumor hypoxia relief to supply O2 for PDT, photothermal therapy (PTT) for synergistic treatment and multimodal imaging to ensure the theranostic outcome.

Polythiophenes with Cationic Phosphonium Groups as Vectors for Imaging, siRNA Delivery, and Photodynamic Therapy.

In this work, we exploit the versatile function of cationic phosphonium-conjugated polythiophenes to develop multifunctional platforms for imaging and combined therapy (siRNA delivery and photodynamic therapy). The photophysical properties (absorption, emission and light-induced generation of singlet oxygen) of these cationic polythiophenes were found to be sensitive to molecular weight. Upon light irradiation, low molecular weight cationic polythiophenes were able to light-sensitize surrounding oxygen into reactive oxygen species (ROS) while the highest were not due to its aggregation in aqueous media. These polymers are also fluorescent, allowing one to visualize their intracellular location through confocal microscopy. The most promising polymers were then used as vectors for siRNA delivery. Due to their cationic and amphipathic features, these polymers were found to effectively self-assemble with siRNA targeting the luciferase gene and deliver it in MDA-MB-231 cancer cells expressing luciferase, leading to 30–50% of the gene-silencing effect. In parallel, the photodynamic therapy (PDT) activity of these cationic polymers was restored after siRNA delivery, demonstrating their potential for combined PDT and gene therapy.

Multifunctional TPP-PEG-biotin self-assembled nanoparticle drug delivery-based combination therapeutic approach for co-targeting of GRP78 and lysosome

BackgroundIn this study, a multifunctional tetraphenylporphyrin (TPP) conjugated polyethylene glycol with biotin (TPP-PEG-biotin) as a photo-dynamic therapy (PDT) material encapsulating a ruthenium complex 1 (Ru-1) was fabricated as self-assembled nanoparticle (Ru-1@TPP-PEG-biotin SAN) to co-target glucose-regulated protein 78 (GRP78) and the lysosome as a new anti-cancer therapeutic strategy.ResultsThe MTT assay results reveals the enhanced anticancer activity of the Ru-1@TPP-PEG-biotin SANs due to the co-targeting of the GRP78 and lysosome. The Ru-1@TPP-PEG-biotin reduced level of GRP78 and lysosomal ceramide that contributed to the stability of the lysosomal membrane. The endoplasmic reticulum (ER) stress concomitant with the inhibition of GRP78 was clearly monitored by the phosphorylation of protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), and inositol-requiring enzyme 1 α (IRE1α) kinases to indicate the activation of the unfolded protein response (UPR) signaling using immunofluorescence assay. On the other hand, the degradation of the lysosome was observed through PDT action by the Ru-1@TPP-PEG-biotin SAN treatment. This was confirmed by the co-localization assay showing the disappearance of cathepsin D and lysosomal-associated membrane protein 1 (LAMP1) in the lysosome.ConclusionsConsidering lysosome-mediated autophagy is an effective cancer cell survival mechanism, the degradation of the lysosome along with GRP78 inhibition by the Ru-1@TPP-PEG-biotin SAN combination therapy is suggested as a new co-targeting cancer treatment.

Mitochondria targeted redox GFP reveals time and dose dependent onset and progression of mitochondrial oxidation with diverging cell death decisions during photodynamic therapy.

Photodynamic therapy (PDT) is a successful cancer treatment modality. In vitro, in vivo, and clinical studies with different photosensitizers reveal diverging cell fates, including apoptosis, necrosis, autophagy, and non-specific forms of cell death. The mode of action and efficacy of PDT is mediated through free radical generation and is highly dependent on diverse variables such as nature, dose, metabolism of photosensitizer, irradiation energy, and irradiation cycle. Discovery of newer photosensitizers and optimization of PDT approaches to achieve a clinically relevant form of cell death called apoptosis requires better in vitro real-time methods. Oxidative damage and mitochondrial permeabilization are critical signaling events involved in photodamage and apoptosis. Hence, mitochondrial damage detection is an appropriate target signaling for mechanistic evaluation of PDT. We report mitochondria-targeted redox GFP expressing cells as a sensitive system to test and validate important variables of PDT using the photosensitizer 5-Aminolevulinic acid (5-ALA) as a model. An independent FRET-based caspase sensor cell was also used to study the impact of the photosensitizer dosage and irradiation duration on the mode of cell death. The study reveals that the cancer cells expressing mt-roGFP are extremely sensitive to monitor mitochondrial oxidation induced by PDT. The extent of mitochondrial redox changes induced by PDT can be determined using these sensor cells by real-time image-based approaches. These approaches provide sufficient temporal resolution that is required to fine-tune and optimize the PDT conditions. The degree of oxidation of the probe is highly dependent on the dosage of photosensitizer and duration of light irradiation, which determines the nature of cell death. A real-time caspase sensor probe further confirmed that the caspase-dependent and caspase-independent nature of cell death is in high correlation with the extent of mitochondrial oxidation. A condition that triggers rapid and extreme mito-oxidation seems to favor necrosis, while delayed and slowly progressing redox changes contribute to caspase-dependent apoptosis. The study confirms that temporal analysis of mitochondrial oxidation is a reliable biomarker for fine-tuning PDT conditions to achieve the desired outcome. This can be achieved using stable cancer cell lines expressing mitochondria-targeted roGFP by ratiometric imaging.

Theoretical and photodynamic therapy characteristics of heteroatom doped detonation nanodiamonds linked to asymmetrical phthalocyanine for eradication of breast cancer cells

An amide mono substituted benzothiozole phthalocyanine: zinc(II) 3-(4-((3,17,23-tris(4-(benzo [d]thiazol-2-yl)phenoxy)-9-yl)oxy) phenyl)amide phthalocyanine (NH2BzPc) was covalently linked to undoped and heteroatom doped detonation nanodiamonds (DNDs): B@DNDs, P@DNDs, S@DNDs, N@DNDs, and S&N@DNDs There is a drastic decrease in highest occupied molecular orbital (HOMO) – lowest unoccupied molecular orbital (LUMO) energy gaps for nanoconjugates compared to DNDs alone. B@DNDs-NH2BzPc, S&N@DNDs-NH2BzPc, and P@DNDs-NH2BzPc showed superior photodynamic therapy (PDT) effects. DNDs-NH2BzPc also had a small HOMO-LUMO gap, but did not show improved PDT activity compared to the Pc alone, suggesting doping of DNDs is important. This study shows improved PDT effect on Michigan Cancer Foundation-7 breast cancer lines at 7.63%, 7.62% and 6.5% cell viability for P@DNDs-NH2BzPc, S&N@DNDs-NH2BzPc and B@DNDs-NH2BzPc, respectively.

Chlorin e6-mediated photodynamic therapy modulates adipocyte differentiation and lipogenesis in 3T3-L1 cells.

Chlorin e6-mediated photodynamic therapy (Ce6-mediated PDT) is a therapeutic modality that consists of a photosensitizer, source of light at a suitable wavelength, and molecular oxygen. PDT has been widely used for the treatment of cancers and non-neoplastic disorders. However, information on the inhibitory activity of Ce6-mediated PDT on adipogenesis and lipogenesis in 3T3-L1 cells is not available to date. MTT assay, Oil Red O staining, and Nile red staining were used to investigate lipid accumulation in 3T3-L1 cells to clarify adipocyte differentiation. The expression levels of various molecular signals associated with adipogenesis and lipogenesis were examined by RT-PCR and western blot analysis. Adipocyte differentiation and lipid accumulation were reduced by Ce6-mediated PDT in 3T3-L1 cells. Inhibition of the expression of PPAR-γ, C/EBPα, β, δ, SREBP-1, FAS, and LPL and the activation of AMPK, revealed concise modulation of adipogenic and lipogenic molecules by Ce6-mediated PDT. The anti-adipogenic effect of Ce6-mediated PDT was reversed by AMPKα siRNA. Ce6-mediated PDT inhibits adipocyte differentiation and lipogenesis via regulating AMPK. Ce6-mediated PDT might serve as a potential therapy for the treatment of obesity and obesity-associated diseases.

Antimicrobial and immunomodulatory responses of photodynamic therapy in Galleria mellonella model

BackgroundNew therapeutics are urgently needed for infectious diseases, especially for the fungal infection like Fonsecaea monophora. Photodynamic therapy has been showing antimicrobial activity on some pathogens. The combination of antimicrobial medicines and photodynamic therapy (PDT) might be a practical approach. However, whether the treatment of PDT could do benefits to the host immunity remains poorly documented.ResultsIn this study, Galleria mellonella larvae were employed as a model organism to evaluate the activity of PDT, and also to investigate the regulation of humoral immunity by PDT. Photosensitizer 5-aminolevulinic acid (ALA) was applied to the G. mellonella infection model. It was found that ALA-mediated PDT was non-toxic to G. mellonella, and could extend the median survival of infected larvae from 3 days to 5.5 days. We observed that larval hemocytes inhibited the growth of Candida albicans and Staphylococcus aureus, without any contribution by ALA-PDT. Furthermore, the application of ALA-PDT demonstrated the immunomodulation of larval innate immunity as increased hemocyte density counting, cell morphological transformation, and sensitivity to pathogens.ConclusionsG. mellonella could be considered as a useful model to study the immunoregulation of PDT. This model revealed that ALA-PDT positively defense against infections through inducing humoral immune responses of larvae.

In Vitro Bioeffects of Polyelectrolyte Multilayer Microcapsules Post-Loaded with Water-Soluble Cationic Photosensitizer.

Microencapsulation and targeted delivery of cytotoxic and antibacterial agents of photodynamic therapy (PDT) improve the treatment outcomes for infectious diseases and cancer. In many cases, the loss of activity, poor encapsulation efficiency, and inadequate drug dosing hamper the success of this strategy. Therefore, the development of novel and reliable microencapsulated drug formulations granting high efficacy is of paramount importance. Here we report the in vitro delivery of a water-soluble cationic PDT drug, zinc phthalocyanine choline derivative (Cholosens), by biodegradable microcapsules assembled from dextran sulfate (DS) and poly-l-arginine (PArg). A photosensitizer was loaded in pre-formed [DS/PArg]4 hollow microcapsules with or without exposure to heat. Loading efficacy and drug release were quantitatively studied depending on the capsule concentration to emphasize the interactions between the DS/PArg multilayer network and Cholosens. The loading data were used to determine the dosage for heated and intact capsules to measure their PDT activity in vitro. The capsules were tested using human cervical adenocarcinoma (HeLa) and normal human dermal fibroblast (NHDF) cell lines, and two bacterial strains, Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Our results provide compelling evidence that encapsulated forms of Cholosens are efficient as PDT drugs for both eukaryotic cells and bacteria at specified capsule-to-cell ratios.

The photophysicochemical properties and photodynamic therapy activity of In and Zn phthalocyanines when incorporated into individual or mixed Pluronic® micelles

The synthesis, photophysicochemical properties and photodynamic activity (PDT) of tetra-pyridyloxy (1,2) and benzothiazole (3, 4) substituted indium (III) (1,3) and zinc (2, 4) phthalocyanines (Pcs) and their incorporation into Pluronic® F127 and Pluronic L121/F127 mixed micelles (the latter for 3 and 4 only) are presented in this study. The InPcs exhibited higher singlet oxygen (ΦΔ) at 0.76 and 0.68 compared to the ZnPc’s at 0.47 and 0.44 in dimethyl sulfoxide. The ΦΔ values in the presence of Pluronic® F127 and in water, were 0.39 and 0.42 for InPcs and 0.23 and 0.37 for ZnPc. The ΦΔ values in the presence of Pluronic F127/L121 mixed micelles for complex 3 and 4 were 0.51 and 0.29 in water. The Kp was determined using the water and octanol system. InPcs had larger Kp values suggesting that they are more likely to be taken up by the cancer cells hence they showed better PDT activity.

Theranostic lyotropic liquid crystalline nanostructures for selective breast cancer imaging and therapy

Herein, we report the development of theranostic lyotropic liquid crystalline nanostructures (LCN's) loaded with unique MnO nanoparticles (MNPs) for selective cancer imaging and therapy. MNPs serves as a fluorescent agent as well as a source of manganese (Mn2+) and enables localized oxidative stress under the hallmarks of cancer (acidosis, high H2O2 level). In pursuit of synergistic amplification of Mn2+ antitumor activity, betulinic acid (BA) is loaded in LCN's. In this investigation, nano-architecture of LCN's phase interface is established via SAXS, Cryo-TEM and Cryo-FESEM. Intriguing in vitro studies showed that the LCN's triggered hydroxyl radical production and exhibited greater selective cytotoxicity in cancer cells, ensuring the safety of normal cells. Significant tumor ablation is realized by the 96.5 % of tumor growth inhibition index of LCN's as compared to control group. Key insights into on-site drug release, local anti-cancer response, and tumor location are gained through precise guidance of fluorescent MNPs. In addition, comprehensive assessment of the safety, pharmacokinetics and tumor distribution behavior of LCN's is performed in vivo or ex vivo. This work emphasizes the promise of modulating tumor microenvironment with smart endogenous stimuli sensitive nano systems to achieve advanced comprehensive cancer nano-theranostics without any external stimulus. Statement of significanceEffective diagnosis and treatment approaches with maximum anti-cancer activity and minimal side-effects are critical to ameliorate cancer therapy. Compared to radiation, photodynamic and photothermal therapy, the specific and selective activation of tumor microenvironmental endogenous stimuli for the logical generation of cytotoxic OH· free radicals serves as an efficient therapeutic strategy for chemodynamic-cancer treatment. In this investigation, MnO nanoparticles fulfill two needs (fluorescence-based optical imaging and a source of Mn2+ based chemodynamic therapy) in one unit. This approach also ensures the safety of normal cells, as the toxic OH· free radical activity is substantially suppressed under the mild alkaline/H2O2 conditions in normal cell microenvironment.

Magnetic stomatocyte-like nanomotor as photosensitizer carrier for photodynamic therapy based cancer treatment

Amphiphilic block copolymer can self-assemble to stomatocyte-like structure as drug delivery carrier. Photodynamic therapy (PDT) is an emerging modality for cancer treatment. However, PDT has various problems, such as weak tumor accumulation ability of photosensitizers (PSs), short lifetime of singlet oxygen (1O2, main reactive oxygen species in PDT) and tumor hypoxia microenvironment, to restrict its therapeutic efficacy. To convey PSs to tumor tissues and improve PDT efficacy, iron oxide nanoparticles (IONPs) were loaded inside the self-assembly stomatocytes-like structure of poly(ethylene glycol) block polystyrene (PEG-b-PS) as nanomotors (IONPs loaded stomatocytes nanomotors, denoted IS-NMs) for PS (zinc phthalocyanine, ZnPc) delivery. The hybrid nanomotors (iron oxide nanoparticles loaded stomatocytes@ZnPc nanomotors, denoted ISP-NMs) can be gathered in tumor tissues under magnetic field owing to magnetism of IONPs. After been trapped by cancer cells, IONPs can catalyze decomposition of endogenous H2O2 to generate O2 as propelling force for ISP-NMs movement. The motion characteristics of ISP-NMs expanded the distribution of ZnPc to enlarge ROS reactive distribution and enhance the activity of PDT. And the generated O2 can be supplied for PDT process to ensure its high-performance. Furthermore, ISP-NMs have nuclear magnetic resonance imaging (MRI) function since IONPs are efficient T2 contrast agent.

X-ray induced photodynamic therapy (PDT) with a mitochondria-targeted liposome delivery system

In this study, we constructed multifunctional liposomes with preferentially mitochondria-targeted feature and gold nanoparticles-assisted synergistic photodynamic therapy. We systemically investigated the in vitro X-ray triggered PDT effect of these liposomes on HCT 116 cells including the levels of singlet oxygen, mitochondrial membrane potential, cell apoptosis/necrosis and the expression of apoptosis-related proteins. The results corroborated that synchronous action of PDT and X-ray radiation enhance the generation of cytotoxic reactive oxygen species produced from the engineered liposomes, causing mitochondrial dysfunction and increasing the levels of apoptosis.

High-efficiency platinum–carbon nanozyme for photodynamic and catalytic synergistic tumor therapy

Photodynamic therapy (PDT) is an effective approach for tumor treatment, which converts oxygen into reactive oxygen species (ROS) through light irradiation upon a photosensitizer. Due to the low instability of most current photosensitizers, nanocarriers for loading and delivering photosensitizers were specifically needed to be developed. However, most nanocarriers, such as polymer-based, lipid-based vehicles, only act as a carrier, without antitumor activity. Thus, development of suitable nanocarriers for photosensitizers with integrating multi-antitumor functions will improve the efficiency of PDT. Here, we reported two different kinds of Pt/carbon (Pt/C) nanozymes as the nanocarriers for chlorin e6 (Ce6) loading. Besides the PDT based on Ce6, Pt/C nanozymes could mimic the activities of peroxidase and oxidase to transfer H2O2 and O2 in tumor sites to ROS respectively, further killing tumor. By comparing the distribution of Pt nanoparticles inside or outside the carbon spheres, we found that it exhibited higher enzyme-mimicking and antitumor activity when the Pt was loaded outside the carbon shell. Cellular and animal studies demonstrated that the efficient tumor destruction was achieved through the combination of PDT and nanozyme-based catalytic therapy. These results implied that the intrinsic enzyme-like activity of nanozymes and PDT can be synergized for efficient tumor treatment, providing a proof-of-concept of tumor photodynamic-catalytic therapy.

Ultra-dispersed biomimetic nanoplatform fabricated by controlled etching agglomerated MnO2 for enhanced photodynamic therapy and immune activation

Hypoxia plays a pivotal role in malignant tumor invasion and metastasis, affecting tumor therapeutic effect and tumor immune microenvironment (TME). Previous studies have proved that manganese dioxide (MnO2) nanoparticles could significantly improve the hypoxic tumor microenvironment. Yet the fatal disadvantage of agglomeration upon collection by centrifugation or other treatments limit their uses in hypoxia therapies. In this study, we avoided the agglomeration of MnO2 by a controlled etching method via the unique weak acidity of PEG-PLGA aqueous solution. Then, the photosensitizer chlorin e6 (Ce6) was loaded into the PEG-PLGA core and 4T1 cancer cell membrane fragments acting as a shell (PLGA-Ce6-MnO2@4T1M, PCM@M). After intravenous injection into the 4T1-tumor bearing mice, PCM@M showed homogeneous targeting to 4T1 tumor and greatly enhanced the effect of photodynamic therapy (PDT) in vivo. In addition, PCM@M also alleviate tumor hypoxia and polarize macrophages in the TME. More interestingly, PCM@M activated T-cells and maturated dendritic cells in vivo upon laser irradiation. All data showed that PCM@M can reshape the immunosuppressive TME and be promising in cancer treatment.

Photodynamic Therapy Activity of Phthalocyanine-Silver Nanoparticles on Melanoma Cancer Cells.

The synthesis, characterization and photodynamic therapy activity of a novel metal free phthalocyanine (complex 3), with or without silver nanoparticles (AgNPs), are reported. The in vitro photodynamic activity of this complex was investigated using metastatic melanoma cancer cell line. In the presence of different concentrations of complex 3 or 3 in combination with silver nanoparticles, the viability of the cells showed a concentration dependent decrease upon irradiation with red light. The photodynamic activity of complex 3 showed an increase in the presence of the AgNPs. Although complex showed a high degree of aggregation in water, it still demonstrated reasonable potency towards the melanoma cancer cell line.

Investigation of the emission spectra and cytotoxicity of TiO2 and Ti-MSN/PpIX nanoparticles to induce photodynamic effects using X-ray.

Photodynamic therapy (PDT) has been recognized as an effective method for cancer treatment; however, it suffers from limited tissue penetration depth. X-rays are ideal excitation sources for activating self-lighting nanoparticles that can penetrate through deep tumor tissues and convert the X-rays to visible light. In this study, Ti-MSN/PpIX nanoparticles for X-ray induced photodynamic therapy was synthesized. Preparation, characterization, and emission spectrum of Ti-MSN/PpIX nanoparticles as well as PDT activity and toxicity of the nanoparticles on HT-29 cell line were investigated. Firstly, mesoporous silica nanoparticles (MSN) were synthesized through sol-gel method. Then, TiO2 and PpIX were loaded in MSN. Next, the emission spectra of TiO2, Ti-MSN, and Ti-MSN/PpIX nanoparticles, while activated by X-ray (6 MVp), were recorded. In addition, viability of cells after treatment by Ti-MSN/PpIX nanoparticles and X-ray irradiation was studied. SEM, TEM and FESEM images of the spherical composite nanoparticles showed that their dimensions were changed by incorporating Ti and organic compound of PpIX. Two-dimensional hexagonal structure with d100-spacing was about 3.5 nm with particle sizes of 70-110 nm. The optical characteristics of TiO2 nanoparticles showed strong emission lines, which effectively overlapped with the absorption wavelengths of protoporphyrin IX (PpIX). Cellular experiments showed Ti-MSN/PpIX nanoparticles have proper biocompatibility, however, after X-ray irradiation, significant decrease of cell viability in the presence of the nanoparticles was observed. The presented X-PDT method could enhance RT efficacy and is enable that allows for reducing X-ray dose exposure to healthy tissues to overcome radio-resistant tumors.

Adjuvants that Empower the Action of Photodynamic Therapy.

Compounds have been devised whose supportive actions make them important adjuvants in the priming of photosensitization to selectively target cancer cells. Here, we highlight the paper by Maytin and Hasan in this issue of Photochemistry & Photobiology, which describes adjuvants methotrexate, 5-fluorouracil, vitamin D and its analogs leading to improved photodynamic therapy outcome. These small molecule adjuvants act by different mechanisms to enhance the cytotoxicity in tumor cells and the therapeutic effect in cancers. These findings add to the list of strategies for enhancement of photodynamic therapy.

Comparison of photodynamic therapy with methylene blue associated with ceftriaxone in gram-negative bacteria; an in vitro study.

The resistance of microorganisms increases the need for new antimicrobial therapies. The aim of this study was to evaluate the in vitro action of photodynamic therapy and its combination with ceftriaxone in third generation cephalosporin resistant gram-negative bacteria. Clinical strains of Klebsiella pneumoniae, Enterobacter aerogenes and Escherichia coli were obtained, incubated with MB for 15 min combined or not with ceftriaxone and irradiated with fluence of 10 and 25 J/cm². MB internalization was evaluated by confocal microscopy. Cell viability was assessed by counting colony forming units and bacterian metabolism by the resazurin test. MB has been observed within cells, although not in all bacteria. PDT-MB alone and combined with Ceftriaxone reduced bacterial growth by approximately 1 log at 10 J/cm² of fluence and 4 logs by 25 J/cm², with a significant difference from the control group. The reduction in bacterial growth between the treated groups was similar, without significant difference between them. The Resazurin test showed lower bacterial metabolic activity in the treated groups, but it did not allow to observe difference between fluences. It was concluded with this study that the internalization of MB was not observed in all cells of K. pneumoniae, E. aerogenes and E. coli strains. There was less bacterial metabolic activity in the treated groups, with no variation between different fluences. PDT-MB 25 J/cm² alone and combined with Ceftriaxone showed antimicrobial action, but the PDT-MB/Ceftriaxone combination had no potentiating effect.