Photosensitizer Concentration Research Articles

Highly sensitive measurement method for photosensitizers based on dual-excitation laser modulation technique

A dual-excitation laser modulation technique for the sensitive measurement of photosensitizers in tumor is proposed. The technique is based on the difference in optical absorption properties of photosensitizers and biological tissues at 405 nm and 450 nm. The 405 nm and 450 nm laser beams, with the same modulation frequency and 180° phase difference, were coupled into a single fiber simultaneously. A periodic signal with a frequency of 1 kHz was generated in alternating excitation, and was processed by phase sensitive detectors. The weak photosensitizer fluorescence masked by tissue autofluorescence can be effectively separated through the proposed method, so that the final signal intensity is only related to the concentration of photosensitizer. The method with a sensitivity of 0.22 mL/ng was determined by measuring the low concentration of protoporphyrin IX (PpIX) solution, and the detection limit of instrument reached 0.5 ng/mL. The puncturable optical probe with a diameter of 675 µm ensures that PpIX in can be detected with spatial resolution, which was performed in the measurement of PpIX in tumor bearing nude mice.

Homogeneous Photosensitized Oxidation for Water Reuse in Cellars: A Study of Different Photosensitizers

The demand for fresh water is increasing daily, requiring industries to take action to reduce the need for fresh water. Winemaking industries represent a massive hydric impact by combining the water consumed and the high volume of wastewater produced. The sun-driven photooxidation process has been widely employed in removing wastewater pollutants. This work employed four photosensitizers, Rose Bengal, AlPcS4, ZnPcS4, and TPP, for water reuse in cellars. A secondary effluent has been investigated as a water matrix. Of all the photosensitizers (PS) employed, ZnPcS4 showed better chemical oxygen demand (COD) (23%) and phenolic (TPh) (81%) removal. The effect of pH and concentration was also assessed for ZnPcS4. The phenolic content removal was found to be highly dependent on the solution’s pH, as alkaline solutions improve the singlet oxygen quantum yield where the use of a pH = 11 reached 42% and 81% of COD and TPH removal. However, a pH higher than 7 showed higher PS bleaching than pH = 7. Three different PS concentrations were evaluated: 3 × 10−6, 5 × 10−6, and 1 × 10−5 mol/L. The optimal PS concentration was found to be 5 × 10−6 mol/L.

Photoresponsive liposomes and LipoParticles by incorporating a photosensitizer agent in their lipid membrane

Liposomes, as self-assembled lipid layer vesicles, have emerged as a promising platform for various biomedical applications such as photodynamic therapy (PDT). LipoParticles are core–shell lipid assemblies with a solid polymer core coated by a lipid membrane, which gather the advantages of both their counterparts. Photosensitizers (PS), used in PDT, are photosensitive molecules than can be activated by an exposure to a light source, leading to the death of pathogenic surrounding cells. In this context, the aim of this study is to elaborate liposomes and LipoParticles incorporating a PS, and to examine their resulting photoresponsive properties by following the release, triggered by an UV irradiation, of incorporated fluorescent (macro)molecules. Al(III) phthalocyanine chloride disulfonic acid (AlPcS2) was chosen as PS, and the release of 5(6)-carboxyfluorescein (CF) or bovine serum albumin conjugated with fluorescein isothiocyanate (BSA-FITC) from liposomes and poly (lactic-co-glycolic acid) (PLGA) core of LipoParticles respectively, was investigated by fluorescence spectroscopy. The results have shown that UV irradiation led to the release of CF molecules depending on the membrane lipid formulation, and that repeated irradiations could increase the amount of CF molecules released from liposomes. The main parameters governing the release of BSA-FITC macromolecules from LipoParticles were the temperature of their elaboration (corresponding to a reorganization of several liposomes on the surface of PLGA particles), the initial PS concentration, and the duration of UV irradiation. Best results were found with a temperature of the LipoParticles elaboration of 20 °C, a PS concentration of 0.1 mM, and a duration of irradiation of 5 min. These results support the fact that similarly to liposomes, LipoParticles can also be endowed with photoresponsive properties, which positions them as interesting nanovectors for PDT.

Antimicrobial photodynamic in vitro inactivation of Enterococcus spp. and Staphylococcus spp. strains using tetra-cationic platinum(II) porphyrins

This manuscript presents the first report on antimicrobial photo-inactivation in vitro using tetra-cationic porphyrins with peripheral platinum(II) bipyridyl complexes against Gram-positive bacteria. Two isomeric tetra-cationic porphyrins (3TPyP and 4TPyP) were tested against clinically important bacterial species. The antimicrobial activity assays were performed at specific photosensitizer (PS) concentrations under dark and white-light LED irradiation conditions for 120 min. The porphyrin 3-PtTPyP was the most efficient PS against the bacteria tested, inhibiting bacterial growth in just 15 min and 30 min at low concentrations (3.75 and 0.45 µM). The minimal inhibitory concentration of the porphyrin increased in the presence of reactive oxygen species scavengers, indicating that singlet oxygen and radical species likely participated in the photo-oxidation mechanism. In addition, the checkerboard assay that tests the association of compounds, showed a synergistic effect, suggesting a potentiation of the antibacterial effect when porphyrin was tested in combination with ciprofloxacin and vancomycin. Thus, tetra-cationic porphyrins containing platinum(II) complexes are promising agents for microbial photo-inactivation as an alternative therapy against infections.

On the need for standardized reporting of photophysical parameters of in vitro photodynamic therapy studies.

In vitro dose escalation experiments are one of the first gatekeepers in therapeutic evaluation and development. This also holds for evaluating novel photosensitizers (PS) and Photodynamic Therapy (PDT) co-therapies as needed to provide dose response guidelines before engaging in further pre-clinical studies. The dose needed to achieve 50% cell kill (LD50) is a standard metric to report the potency of a therapeutic agents that is widely accepted for single-drug therapies. In reporting results of PDT experiments, which involve delivery of both drug and light, it is inherently more complicated to identify such a convenient dose response metric that actually captures the larger space of treatment parameters. In addition to ubiquitous sources of biological variability that apply broadly in biomedical research, PDT treatment efficacy is determined by multiple key parameters that may or may not have been documented, including PS concentration and light fluence, where the latter is itself a function of the spectral properties of the light source used (often not described), not to mention dose rate, fractionation and other parameters that potentially vary between individual studies. It is impossible to compare results between two study when, for example one reports LD50 PS concentration without providing essential light dosimetry details. Motivated by this challenge in comparing outcomes and establishing reproducibility of in vitro PDT studies, we endeavored to perform a meta-analysis of the reporting of PDT results by converting, where possible, the disparately reported experimental details into a consistent metric that could be used to compare across studies. In this context we adopt here the number of photons absorbed by photosensitizers per unit volume to affect a 50% decline in cell survival as a standardized metric. By choosing this metric one can acknowledge the quantum-based generation of cytotoxins. While this metric does not cover every possible source of variability between any two studies, for a PS with known optical properties, this does encapsulate PS concentration as well as irradiance and spectral properties of light delivered. For the sake of focus we adopt this approach for study of reported results with two photosensitizers, Protoporphyrin IX, either synthesized in the cells by aminolevulinic acid or administered exogenously, and Chlorin e6. A literature search was performed to identify in vitro studies with these two photosensitizers and collect necessary information to calculate the absorbed photon LD50 threshold for each study. Only approximately 1/10 of the manuscripts reporting on in vitro studies provide the minimum required information to calculate the threshold values. While the majority of the determined threshold values are within a factor of 10, the range of threshold values spanned close to 7 orders of magnitude for both photosensitizers. To contrast with single-agent therapies, a similar exercise was performed for chemotherapeutic drugs targeting cellular mitosis or tyrosine kinase inhibitors resulted in an LD50 or IC50 range of 1-2 orders of magnitude, with LD50 or IC50 values for a single cell line being within a factor of 5. This review underscores challenges in the reporting of in vitro PDT efficacy. In many cases it takes considerable effort to extract the necessary methodology information to make meaningful comparison between PDT studies. Only when results between studies can be compared is it possible to begin to assess reproducibility which, as shown here, can be a major issue. Hence, guidelines need to be developed and enforced through the peer review process for meaningful reporting of preclinical PDT results in order for the most promising sensitizers and co-therapies to be identified and translated into the clinic.

Effects of sunlight on the fate of graphene oxide and reduced graphene oxide nanomaterials in the natural surface water

Graphene nanomaterials have been commercialized for use in the electronic and biomedical industries, increasing their dissemination into surface waters and subsequent transformation in natural aquatic environment. While the photodegradation of graphene oxide nanomaterials has been investigated in the past, previous research did not consider actual natural aquatic environment and also focused on primarily graphene oxide nanomaterials. In this study, photodegradation of graphene nanomaterials with varying oxidation levels, including graphene oxide (GO) and partially reduced graphene oxide (rGO-2 h) are evaluated in Columbia River Water and compared with each other. Our results indicate that both direct and indirect photolysis of graphene-based nanomaterials will occur simultaneously in natural surface water. However, environmentally relevant concentrations of photosensitizers in surface water are not capable of producing sufficient ·OH to initiate degradation of GO via indirect photolysis. For all conditions tested, GO showed more rapid photodegradation compared to rGO. Overall, direct and indirect photodegradation of graphene oxide nanomaterials in natural surface water is minimal and slow indicating that phototransformation of graphene-based nanomaterials will be insignificant in natural surface water.

Sulfonamide Porphyrins as Potent Photosensitizers against Multidrug-Resistant Staphylococcus aureus (MRSA): The Role of Co-Adjuvants.

Sulfonamides are a conventional class of antibiotics that are well-suited to combat infections. However, their overuse leads to antimicrobial resistance. Porphyrins and analogs have demonstrated excellent photosensitizing properties and have been used as antimicrobial agents to photoinactivate microorganisms, including multiresistant Staphylococcus aureus (MRSA) strains. It is well recognized that the combination of different therapeutic agents might improve the biological outcome. In this present work, a novel meso-arylporphyrin and its Zn(II) complex functionalized with sulfonamide groups were synthesized and characterized and the antibacterial activity towards MRSA with and without the presence of the adjuvant KI was evaluated. For comparison, the studies were also extended to the corresponding sulfonated porphyrin TPP(SO3H)4. Photodynamic studies revealed that all porphyrin derivatives were effective in photoinactivating MRSA (>99.9% of reduction) at a concentration of 5.0 μM upon white light radiation with an irradiance of 25 mW cm-2 and a total light dose of 15 J cm-2. The combination of the porphyrin photosensitizers with the co-adjuvant KI during the photodynamic treatment proved to be very promising allowing a significant reduction in the treatment time and photosensitizer concentration by six times and at least five times, respectively. The combined effect observed for TPP(SO2NHEt)4 and ZnTPP(SO2NHEt)4 with KI seems to be due to the formation of reactive iodine radicals. In the photodynamic studies with TPP(SO3H)4 plus KI, the cooperative action was mainly due to the formation of free iodine (I2).

In Vitro Photoinactivation of Fusarium oxysporum Conidia with Light-Activated Ammonium Phthalocyanines.

Antimicrobial photodynamic therapy (aPDT) has been explored as an innovative therapeutic approach because it can be used to inactivate a variety of microbial forms (vegetative forms and spores) without causing significant damage to host tissues, and without the development of resistance to the photosensitization process. This study assesses the photodynamic antifungal/sporicidal activity of tetra- and octasubstituted phthalocyanine (Pc) dyes with ammonium groups. Tetra- and octasubstituted zinc(II) phthalocyanines (1 and 2) were prepared and tested as photosensitizers (PSs) on Fusarium oxysporum conidia. Photoinactivation (PDI) tests were conducted with photosensitizer (PS) concentrations of 20, 40, and 60 µM under white-light exposure at an irradiance of 135 mW·cm-2, applied during 30 and 60 min (light doses of 243 and 486 J·cm-2). High PDI efficiency corresponding to the inactivation process until the detection limit was observed for both PSs. The tetrasubstituted PS was the most effective, requiring the lowest concentration and the shortest irradiation time for the complete inactivation of conidia (40 µM, 30 min, 243 J·cm-2). Complete inactivation was also achieved with PS 2, but a longer irradiation time and a higher concentration (60 µM, 60 min, 486 J·cm-2) were necessary. Because of the low concentrations and moderate energy doses required to inactivate resistant biological forms such as fungal conidia, these phthalocyanines can be considered potent antifungal photodynamic drugs.

All-in-one device for mapping the interactive effects of photodynamic therapy dosimetry in tumor gaseous microenvironment.

Photodynamic therapy (PDT) elicits cell death, vascular damage, or/and anti-tumor host immune response upon activating the administered photosensitive drug by an appropriate light source. Because PDT is heavily dependent on tissue oxygen (O2) in essence, the concentration-dependent impact of O2 on tailoring cellular response to PDT remains an in-depth investigation. As a multifaceted modality, optimal combinations of photosensitizer (PS) concentration, light dose, and O2 delivery are critical to achieve ideal therapeutic outcomes. We herein present a fully integrated all-in-one device for the in vitro assessment of PDT efficacy synchronizing the quantitative control of three PDT disciplines simultaneously, aiming at 1) identifying the influence of varying gaseous microenvironments on PDT; and 2) determining the contribution of each PDT factor and estimating the strength of their synergic effect. The gas-gradient-generating unit for contactless headspace O2 delivery and spatial light control filtering layer in our device could either work as a stand-alone module or combine to screen a range of experimental PDT parameters. By sweeping a total of 128 conditions over four 5-aminolevulinic acid (5-ALA) concentrations, four light dosages, and eight O2 levels in one single experiment, we determined the main effects of the three key PDT agents and highlighted the interactive effect between 5-ALA and light after full-factorial statistical analysis. Our device is not only a versatile tool for predicting PDT efficacy during the translational study but also provides valuable multidimensional information for the interrelation between key PDT factors, which may expedite clinical PDT dosimetry and furnish new insights for the fundamental understanding of photobiological processes.

Positive effects of low-dose photodynamic therapy with aminolevulinic acid or its methyl ester in skin rejuvenation and wound healing: An update.

In dermatology, photodynamic therapy (PDT) is widely used in skin tumors, infections, etc., because of the killing effect triggered by toxic reactive oxygen species (ROS). However, the ROS concentration is determined by various photosensitizer concentrations and formulations, as well as various irradiation parameters. Low-dose PDT leads to sufficiently low ROS level, which results in biological effects that are the exact opposite of the killing potency. Therefore, in recent years, low-dose PDT has been exploited in improving aging and wound. Low-dose ALA/MAL PDT might improve aging through promoting the proliferation of fibroblasts, blocking DNA damage, counteracting oxidative stress, inhibiting melanogenesis, and remodeling lymphatic vessels in aged skin. Promoting fibroblasts and epidermal stem cells proliferation and migration, promoting granulation tissue formation and angiogenesis and regulating the inflammatory process might be the mechanisms of low-dose ALA/MAL PDT in wound healing. Nevertheless, the positive effects of low-dose PDT have not been thoroughly investigated in dermatology, and high-quality studies are still needed to fill the relevant vacancy.

In vitro anti-tumoral activity of two versatile cationic porphyrins on melanoma cells

Porphyrin (Por) dyes are considered photoactive entities with potential properties to be applied as photosensitizers (PS) in cancer Photodynamic Therapy (PDT). The use of suitable units, like pyridinium ones, is an important strategy to add peripheral and non-peripheral positive charges in the Por structure, and in that way develop effective cationic PSs for melanoma treatments. In this context, free-base porphyrins bearing thiopyridinium (1) or methoxypyridinium (2) units were studied on melanoma cells, and their PDT effectiveness was studied and compared. The different charge positions of the cationic peripheral units on the Por macrocycle contribute differently to their PDT behavior. The obtained results demonstrate high in vitro PDT efficacy for both PSs. For the highest PS concentration tested (20 [Formula: see text]M) the photocytotoxicity reaches the detection limit of the MTT assay upon 201 seconds of blue light irradiation ([Formula: see text] = 405 ± 20 nm) at an irradiance of 24.9 mW/cm2, which corresponds to a light dose of 5 J/cm2. Interestingly, under the same experimental conditions, cationic Por 1 shows very interesting PDT results at lower concentrations of 1 to 10 [Formula: see text]M.

Generation of singlet oxygen by porphyrin and phthalocyanine derivatives regarding the oxygen level

Background. The principle of photodynamic effect is based on the combined action of photosensitiser, molecular oxygen and light, which produce various reactive oxygen species and are associated with significant cellular damage. Singlet oxygen is one of the most serious representatives, which is characterised by powerful oxidising properties. Moreover, concomitant hyperbaric oxygen treatment can support these effects. Therefore, the subject of our study was to compare the yields of singlet oxygen for four different photosensitizers in dependency on the oxygen concentration. Material and methods. Four different photosensitizers 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate), tetramethylthionine chloride, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin zinc(II) and zinc phthalocyanine disulfonate were investigated to determine the yield of singlet oxygen in PBS by Singlet Oxygen Sensor Green reagent under different partial pressures of oxygen (0.4 and 36 mg/l). Results. There were no noticeable shifts in the excitation and emission fluorescence spectra regarding the oxygen concentration. Concerning the same molar concentration of photosensitizers the production of singlet oxygen was highest for 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin zinc(II), where the rate of the fluorescence change was more than 3 times higher than that obtained for 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate). On the other hand, zinc phthalocyanine disulfonate showed the lowest yield in singlet oxygen production. Conclusions. Singlet oxygen production, within the range of oxygen concentrations achievable in tissues under normoxia or hyperoxia, does not depend on these concentrations. However, the singlet oxygen generation is significantly influenced by the type of photosensitizer, with the highest yield belonging to 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin zinc(II).

In Vivo and In Silico Study of Photodynamic Necrosis Volume in Rat Liver

Photodynamic therapy is a treatment modality that can be used to treat various types of lesions. To produce cell death, reaching a certain threshold dose of reactive oxygen species (ROS) is required. The estimation of ROS production is of paramount importance to predict the depth of necrosis and to ensure that the volume to be treated receives doses higher than the threshold. In this study, we compared a theoretical model for PDT based on Monte Carlo simulations of light irradiance and rate equations with a rat liver model. At the end of the simulation, necrosis depths and volumes were estimated, as well as the photosensitizer (PS), oxygen, and ROS concentrations at each position of the treated area. From the in vivo study, we obtained the ROS concentration threshold of about 1 mM for Photogem in rat liver. This proposed method can be used for any PS or tissue, including tissues with multiple layers. The proposed method can be used to estimate parameters for any PS or tissue, including layered tissues, as long as their parameters are known. In addition, other protocols can be tested, or compared with the standard ones, providing the bases for analyzing a diverse range of photodynamic treatment scenarios.

Development of AB3-Type Novel Phthalocyanine and Porphyrin Photosensitizers Conjugated with Triphenylphosphonium for Higher Photodynamic Efficacy.

There are a number of lipophilic cations that can be chosen; the triphenylphosphonium (TPP) ion is particularly unique for mitochondrion targeting, mainly due to its simplicity in structure and ease to be linked to the target molecules. In this work, mitochondrion-targeted AB3-type novel phthalocyanine and porphyrin photosensitizers (PSs) were synthesized and their photophysical photochemical properties were defined. Fluorescence quantum yields (ΦF) are 0.009, 0.14, 0.13, and 0.13, and the singlet-oxygen quantum yields (ΦΔ) are 0.27, 0.75, 0.57, and 0.58 for LuPcPox(OAc), AB 3 TPP-Pc, AB 3 TPP-Por-C4, and AB 3 TPP-Por-C6, respectively. To evaluate the photodynamic efficacy of the TPP-conjugated PS cell viabilities of A549 and BEAS-2B lung cells were comparatively measured and IC-50 values were determined. AB 3 TPP-Por-C4, AB 3 TPP-Por-C6, and AB 3 TPP-Pc compounds compared to the reference molecules ZnPc and H 2 TPP were found to be highly cytotoxic (sub-micromolar concentration) under the light. LuPcPox(OAc) is the most effective molecule regarding cell killing (the activity). The cell killing of the TPP-conjugated porphyrin derivatives exhibits a similar response compared to LuPcPox(OAc) when the light absorbing factor of the PS is normalized at 660 nm: TPP-conjugated porphyrins absorb less light (lower extinction coefficient) but produce more radical species (higher singlet-oxygen quantum yield) and therefore effectively kill the cells. The singlet oxygen-producing capacity of AB 3 TPP-Pc is almost 3 times higher compared to LuPcPox(OAc) and 50% more efficient with respect to ZnPc, suggesting that TPP-conjugated phthalocyanine may serve as a good photosensitizer for photodynamic therapy (PDT). The high singlet oxygen generation capacity of these novel TPP-conjugated porphyrin and phthalocyanine PS suggests that they might be useful for PDT requiring lower photosensitizer concentration and reduced energy deposited through less light exposure.

Mechanistic Insights into the Charge Transfer Dynamics of Photocatalytic Water Oxidation at the Lipid Bilayer-Water Interface.

Photosystem II, the natural water-oxidizing system, is a large protein complex embedded in a phospholipid membrane. A much simpler system for photocatalytic water oxidation consists of liposomes functionalized with amphiphilic ruthenium(II)-tris-bipyridine photosensitizer (PS) and 6,6'-dicarboxylato-2,2'-bipyridine-ruthenium(II) catalysts (Cat) with a water-soluble sacrificial electron acceptor (Na2S2O8). However, the effect of embedding this photocatalytic system in liposome membranes on the mechanism of photocatalytic water oxidation was not well understood. Here, several phenomena have been identified by spectroscopic tools, which explain the drastically different kinetics of water photo-oxidizing liposomes, compared with analogous homogeneous systems. First, the oxidative quenching of photoexcited PS* by S2O82- at the liposome surface occurs solely via static quenching, while dynamic quenching is observed for the homogeneous system. Moreover, the charge separation efficiency after the quenching reaction is much smaller than unity, in contrast to the quantitative generation of PS+ in homogeneous solution. In parallel, the high local concentration of the membrane-bound PS induces self-quenching at 10:1-40:1 molar lipid-PS ratios. Finally, while the hole transfer from PS+ to catalyst is rather fast in homogeneous solution (kobs > 1 × 104 s-1 at [catalyst] > 50 μM), in liposomes at pH = 4, the reaction is rather slow (kobs ≈ 17 s-1 for 5 μM catalyst in 100 μM DMPC lipid). Overall, the better understanding of these productive and unproductive pathways explains what limits the rate of photocatalytic water oxidation in liposomal vs homogeneous systems, which is required for future optimization of light-driven catalysis within self-assembled lipid interfaces.

Precision Killing of Sinoporphyrin Sodium-Mediated Photodynamic Therapy against Malignant Tumor Cells.

Photodynamic therapy (PDT) has significant advantages in the treatment of malignant tumors, such as high efficiency, minimal invasion and less side effects, and it can preserve the integrity and quality of the organs. The power density, irradiation time and photosensitizer (PS) concentration are three main parameters that play important roles in killing tumor cells. However, until now, the underlying relationships among them for PDT outcomes have been unclear. In this study, human malignant glioblastoma U-118MG and melanoma A375 cells were selected, and the product of the power density, irradiation time and PS concentration was defined as the total photodynamic parameter (TPP), in order to investigate the mechanisms of PS sinoporphyrin sodium (DVDMS)-mediated PDT (DVDMS-PDT). The results showed that the survival rates of the U-118MG and A375 cells were negatively correlated with the TPP value in the curve, and the correlation exactly filed an e-exponential function. Moreover, according to the formula, we realized controllable killing effects of the tumor cells by randomly adjusting the three parameters, and we finally verified the accuracy and repeatability of the formula. In conclusion, the establishment and implementation of a newly functional relationship among the PDT parameters are essential for predicting PDT outcomes and providing personalized precise treatment, and they are contributive to the development of PDT dosimetry.

The antibacterial activity of photodynamic agents against multidrug resistant bacteria causing wound infection

Antimicrobial photodynamic inactivation (aPDI) of multidrug-resistant (MDR) wound pathogens was evaluated with cationic porphyrin derivatives (CPDs). MDR bacterial strains including Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, and Klebsiella pneumoniae were used. The CPDs named PM, PE, PN, and PL were synthesized as a photosensitizer (PS). A diode laser with a wavelength of 655 nm was used as a light source. aPDI of the combinations formed with different energy densities (50, 100, and 150 J/cm²) and PS concentrations (ranging from 3.125 to 600 µM) were evaluated on each bacterial strain. Dark toxicity, cytotoxicity, and phototoxicity were determined on fibroblast cells. In the aPDI groups, survival reductions of up to 5.80 log₁₀ for E. coli, 5.90 log₁₀ for P. aeruginosa, 6.11 log₁₀ for K. pneumoniae, and 6.78 log₁₀ for A. baumannii were obtained. The cytotoxic effect of PL and PM on fibroblast cells was very limited. PN was the type of CPD with the highest dark toxicity on fibroblast cells. In terms of providing broad-spectrum aPDI without or with very limited cytotoxic effect, the best result was observed in aPDI application with PL. The other CPDs need some modifications to show bacterial selectivity for use at 50 µM and above.

Antimicrobial photodynamic activity by water-soluble curcumin against foodborne pathogens

Foodborne diseases and microbiological control represent the major challenge for the food industry. New technologies using natural agents have attracted increasing interest. Therefore, this study aimed to evaluate the in vitro susceptibility of Staphylococcus aureus and Escherichia coli to water-soluble curcumin (WSC) combined with acidic pH and blue LED light. The minimum inhibitory concentration (MIC) and bacterial photoinactivation were conducted using different photosensitizer concentrations. For S. aureus, the combination of WSC with lactic acid and 2.5 min illumination time reduced MIC from 500 µg/mL to 15.62 µg/mL, and WSC with citric acid reduced MIC from 125 µg/mL to 7.81 µg/mL after 5 min of light exposure. WSC without illumination did not inhibit E. coli growth (MIC >1,000 µg/mL), however, when applied with photodynamic therapy (5 min blue LED illumination), WSC at 62.5 µg/mL with lactic acid and WSC at 7.81 µg/mL with citric acid eliminated E. coli cells. The results obtained suggest that water-soluble curcumin with organic acids when combined with a blue LED light was effective against foodborne pathogens.

In vitro photodynamic treatment of Fusarium oxysporum conidia through the action of thiopyridinium and methoxypyridinium chlorins

Antimicrobial photodynamic inactivation (PDI) has been explored as an innovative therapeutic and phytosanitary approach because it can be used to inactivate microbial vegetative forms and spores, without significant development of resistance to photosensitization and collateral damage to host tissues. The objective of this study was to assess the photodynamic antifungal/sporicidal activity of quaternized chlorins (Chls) with thiopyridinium or methoxypyridinium substituents. Free-base and zinc(II) thiopyridinium or methoxypyridinium Chls (1a, 1b, 2a, and 2b, respectively) were prepared and tested on Fusarium oxysporum conidia. The PDI tests were conducted with photosensitizer (PS) concentrations of 100, 25, 15 and 5 µM, under white light exposure at an irradiance of 50 mW.cm−2, applied during 60 min (light dose of 180 J.cm−2). A high PDI efficiency, corresponding to inactivation to the detection limit, was observed with all the molecules. The free-base thiopyridinium chlorin 1a was the most effective PS, requiring the lowest concentration and the shortest irradiation time, for the complete inactivation of conidia (15 µM, 15 min, 45 J.cm−2). Complete inactivation was also achieved with the other chlorins but a higher concentration (100 µM) of PS and, in the case of chlorin 1b, a longer irradiation period (30 min, 90 J.cm−2), were required. Because of the low concentrations and small energy doses required to inactivate resistant biological forms such as fungal conidia, these chlorins can be regarded as potent antifungal photodynamic drugs.

Research on selective uptake of photosensitizer C3N4@RP by different cancer cells

Photodynamic therapy (PDT), as a clinical treatment, can remove malignant cells upon laser irradiation by selective uptake of photosensitizer (PS). The relative contribution of these antitumor effects depends largely on the dose and uptake of PS. In this study, C3N4@RP was chosen as a candidate for selective uptake studies of different cancer cells. C3N4@RP has been proved to possess excellent properties, including absorption edges extending up to 700 nm, efficient cellular uptake, low cytotoxicity, and favorable intracellular fluorescence localization. Considering the optimal therapeutic effect, we first incubated different concentrations of PS with A549 cells and HeLa cells in vitro to observe the uptake efficiency at different times. At a concentration of 20 μg ml−1, the cellular uptake by A549 and HeLa showed a time-dependent accumulation. The increasing accumulation for cancer cells at the most effective cellular uptake for 24 h follows an order of HeLa > A549. These results suggest that different types of cancer cells have different uptake saturation times for the same PS. All of the presented results support the idea that a properly designed PS is suitable for specific cancer at a specific time to achieve the best therapeutic effect.