Photosensitizer Concentration Research Articles

Enhancement of Photogalvanic Effect of Toluidine Blue Dye using Sodium Lauryl Sulphate as an Efficient Additive for Solar Energy Conversion and Storage

In photogalvanic cells, electron transfer reactions can lead to the inexpensive production of solar power with an inherent storage capacity because in solution, the ions involved act as mobile charges through diffusion. This study improved the storage capacity and solar power of photogalvanic cells comprising ethylenediamine acetic acid (EDTA), toluidine blue and sodium lauryl sulphate (NaLS) as a reductant, photosensitizer and surfactant, respectively. The observed maximum photocurrent, photopotential, and open circuit voltage, of the photogalvanic cell were 150 A, 743 mV and 1065 mV, respectively. The efficiency of conversion cells was approximately 0.2630%. In the dark, the storage capacity (t0.5) was 124 min for the photogalvanic cell. The optimization of the influence of different parameters such as variation in photosensitizer concentration, surfactant, reductant, pH, and temperature as well as the electrical output was performed. A mechanism was proposed for photocurrent generation in the photogalvanic cell.

Klorin e6’nın Etanol yardımıyla Metisiline Dirençli Stafilokok aureus üzerindeki Fotodinamik Etkisi

Aim: The random use of antimicrobials for years has led to bacterial DNA mutation and a result of that, bacteria have become resistant to antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA) is among these types of resistant bacteria that can easily infect when the immune system of the host is suppressed, and it significantly delays the wound healing. Different treatment methods are being investigated to overcome this problem. Antimicrobial photodynamic therapy is a candidate to become an alternative treatment for the destruction of MRSA. The aim of this study was to investigate the effect of chlorin e6 for the photoinactivation of MRSA and the synergetic role of ethanol in this mechanism.
 Methods: 655 nm laser light and Chlorin e6 as photosensitizer were examined for the photoinactivation of MRSA. Besides, 20% ethanol was used to increase the total antimicrobial efficacy with lower light energy densities and photosensitizer concentrations. The colony counting method was used to determine viable bacterial cells after each application.
 Results: 25 J/cm2 energy density with 20 μM Chlorin e6 and 50 J/cm2 energy density with 10 μM Chlorin e6 showed the highest bactericidal activity. When 20% ethanol was used as an adjuvant, 25 J/cm2 energy dose with 2 μM Chlorin e6 resulted in a better killing effect. 
 Conclusion: Chlorin e6-mediated photodynamic therapy was successful to destroy MRSA and the addition of ethanol provided the opportunity to obtain higher antibacterial activity with lower light intensities and photosensitizer concentrations.

The application of antimicrobial photodynamic inactivation on methicillin-resistant S. aureus and ESBL-producing K. pneumoniae using porphyrin photosensitizer in combination with silver nanoparticles.

As resistance of bacterial strains to antibiotics is a major problem, there is a need to look for alternative treatments. One option is antimicrobial photodynamic inactivation (aPDI). The pathogenic cells are targeted by a nontoxic photosensitizer while the surrounding healthy tissue is relatively unaffected. The photosensitizer is activated by light of t appropriate wavelength resulting in the generation of reactive oxygen species that are cytotoxic for the pathogens. In this work, the photosensitizer TMPyP and silver nanoparticles (AgNPs) were investigated for their synergistic antibacterial effect. We tested these two substances on two bacterial strains, methicillin-resistant Staphylococcus aureus 4591 (MRSA) and extended-spectrum beta-lactamases-producing Klebsiella pneumoniae 2486 (ESBL-KP), to compare their effectiveness. The bacteria were first incubated with TMPyP for 45 min or 5 h, then irradiated with a LED source with the total fluence of 10 or 20 J/cm2 and then placed in a microbiological growth medium supplemented with AgNPs. To accomplish the synergistic effect, the optimal combination of TMPyP and AgNPs was estimated as 1.56-25 μM for TMPyP and 3.38 mg/l for AgNPs in case of MRSA and 1.56-50 μM for TMPyP and 3.38 mg/l for AgNPs in case of ESBL-KP at 45 min incubation with TMPyP and fluence of 10 J/cm2. Longer incubation and/or longer irradiation led to a decrease in the maximum values of the photosensitizer concentration to produce the synergistic effect. From this work it can be concluded that the combination of antimicrobial photodynamic inactivation with a treatment including silver nanoparticles could be a promising approach to treat bacterial infection.

Attenuation correction technique for fluorescence analysis of biological tissues with significantly different optical properties.

During intraoperative fluorescence navigation to remove various neoplasms and during pharmacokinetic studies of photosensitizers in laboratory animals, in many cases, the ratio of photosensitizer accumulation in the tumor and normal tissue can reach ⩾ 10-fold, which inevitably changes their optical properties. At the same time, the tumor formation process causes various metabolic and structural changes at cellular and tissue levels, which lead to changes in optical properties. A hardware-software complex for the spectral-fluorescence studies of the content of fluorochromes in biological tissues with significantly different optical properties was developed, and it was tested on optical phantoms with various concentrations of photosensitizers, absorbers, and scatterers. To correct the influence of optical properties on the photosensitizer concentration analysis by fluorescence spectroscopy, we propose the spectrum-processing algorithm, which combines empirical and theory-based approaches.

Combinatory Effect of ALA-PDT and Itraconazole Treatment for Trichosporon asahii.

Trichosporiosis is an opportunistic infection that includes superficial infections, white piedra, hypersensitivity pneumonitis, and invasive trichosporonosis. The effect of antifungal agents against these infections is largely weakened by drug resistance and biofilms-related virulence. Photodynamic therapy (PDT) is a new therapeutic approach developed not only to combat cancerous lesions but also to treat infectious diseases such as fungal infections. However, there are few studies on the antimicrobial mechanism of 5-aminolevulinic acid PDT (ALA-PDT) in treating Trichosporon. In this work, we explored the possibility of combining ALA-PDT with an antifungal agent to enhance the therapeutic efficacy of Trichosporon asahii (T. asahii) in a clinical setting and in vitro. The biofilms of T. asahii were constructed by a 96-well plate-based method in vitro. The planktonic and adherent T. asahii were exposed to different concentrations of photosensitizers and different light doses. After PDT treatment, counting colony-forming units and tetrazolium (XTT) reduction assay were used to estimate the antifungal efficacy. The minimal inhibitory concentration of itraconazole before and after PDT treatment was determined by the broth dilution method, and XTT viability assay was used to detect and evaluate the synergistic potential of ALA-PDT and itraconazole combinations in inhibiting biofilms. Scanning electron microscopy (SEM) was performed to assess the disruption of biofilms. Using combination therapy, we have successfully treated a patient who had a T. asahii skin infection. Further in vitro studies showed that the antifungal effect of ALA-PDT on planktonic and adherent T. asahii was dependent on the concentration of ALA and light dosages used. We also found that the sensitivity of both planktonic and biofilm cells to itraconazole were increased after ALA-PDT. Synergistic effect were observed for biofilms in ALA-PDT and itraconazole-combined treatment. The disruption of biofilms was confirmed by SEM, suggesting that ALA-PDT effectively damaged the biofilms and the destruction was further enhanced by ALA-PDT combination of antifungal agents. In conclusion, these data suggest that ALA-PDT could be an alternative strategy for controlling infections caused by Trichosporon. The combination therapy of ALA-PDT with itraconazole could result in increased elimination of planktonic cells and biofilms compared with single therapy. All these findings indicate that it could be a promising treatment against trichosporonosis. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

PH interferes in photoinhibitory activity of curcumin nanoencapsulated with pluronic® P123 against Staphylococcus aureus.

Microbial contamination control is a public health concern and challenge for the food industry. Antimicrobial technologies employing natural agents may be useful in the food industry for these purposes. This work aimed to investigate the effect of photodynamic inactivation using curcumin in Pluronic® P123 nanoparticles (Cur/P123) at different pH and blue LED light against Staphylococcus aureus. Bacterial photoinactivation was conducted using different photosensitizer concentrations and exposure times at pH 5.0, 7.2 and 9.0. A mixture design was applied to evaluate the effects of exposure time (dark and light incubation) on the photoinhibitory effect. S. aureus was completely inactivated at pH 5.0 by combining low concentrations of Cur/P123 (7.80-30.25 μmol/L) and light doses (6.50-37.74 J/cm2). According to the mathematical model, dark incubation had low significance in bacterial inactivation at pH 5.0 and 9.0. No effect in bacterial inactivation was observed at pH 7.2. Cur/P123 with blue LED was effective in inactivating S. aureus. The antimicrobial effect of photodynamic inactivation was also pH-dependent.

Antimicrobial photodynamic therapy against Propionibacterium acnes biofilms using hypericin (Hypericum perforatum) photosensitizer: in vitro study.

Acne vulgaris is the most recurring skin condition in the world, causing great harm to the physical and psychological well-being of many patients. Antimicrobial photodynamic therapy (aPDT) has broad therapeutic applicability. The purpose was to evaluate in vitro the photodynamic inactivation against Propionibacterium acnes (P. acnes) biofilms by using different concentrations of hypericin (Hypericum perforatum) photosensitizer associated with different energies of low-level laser. The biofilms were placed in 96-well microplates with a 6.4-mm diameter surface, by using standard suspensions (2 × 107CFU/mL) and grown in brain heart infusion broth (BHI) for 48h in anaerobic chamber. Subsequently, the control group received application of 0.9% sterile saline solution for 3min; the photosensitising groups received hypericin at concentrations of 5 and 15μg/mL for 3min; the laser groups received irradiation of energies of 3 and 5J (660nm, continuous output, 100mW, 30 and 50s and 100J/cm2 and 166J/cm2, respectively); the aPDT groups received 5 and 15μg/mL concentrations of hypericin associated with energies of 3 and 5J of low-level laser irradiation. After the biofilms were broken up and seeded for CFU counting. The results showed a reduction in P. acnes biofilms after aPDT emphasising that 15μg/mL hypericin associated with 3 and 5J laser irradiation reduced biofilms by 14.1 and 27.9%, respectively. In addition, all groups of aPDT demostrated statistically significant reductions. In vitro photodynamic inactivation against P. acnes biofilms using different concentration of hypericin photosensitizer associated with different energies of low-level laser promoted effective antimicrobial action.

Light Energy Dose and Photosensitizer Concentration Are Determinants of Effective Photo-Killing against Caries-Related Biofilms.

Caries-related biofilms and associated complications are significant threats in dentistry, especially when biofilms grow over dental restorations. The inhibition of cariogenic biofilm associated with the onset of carious lesions is crucial for preventing disease recurrence after treatment. This in vitro study defined optimized parameters for using a photosensitizer, toluidine blue O (TBO), activated via a red light-emitting diode (LED)-based wireless device to control the growth of cariogenic biofilms. The effect of TBO concentrations (50, 100, 150, and 200 μg/mL) exposed to light or incubated in the dark was investigated in successive cytotoxicity assays. Then, a mature Streptococcus mutans biofilm model under sucrose challenge was treated with different TBO concentrations (50, 100, and 150 μg/mL), different light energy doses (36, 108, and 180 J/cm2), and different incubation times before irradiation (1, 3, and 5 min). The untreated biofilm, irradiation with no TBO, and TBO incubation with no activation represented the controls. After treatments, biofilms were analyzed via S. mutans colony-forming units (CFUs) and live/dead assay. The percentage of cell viability was within the normal range compared to the control when 50 and 100 μg/mL of TBO were used. Increasing the TBO concentration and energy dose was associated with biofilm inhibition (p < 0.001), while increasing incubation time did not contribute to bacterial elimination (p > 0.05). Irradiating the S. mutans biofilm via 100 μg/mL of TBO and ≈180 J/cm2 energy dose resulted in ≈3-log reduction and a higher amount of dead/compromised S. mutans colonies in live/dead assay compared to the control (p < 0.001). The light energy dose and TBO concentration optimized the bacterial elimination of S. mutans biofilms. These results provide a perspective on the determining parameters for highly effective photo-killing of caries-related biofilms and display the limitations imposed by the toxicity of the antibacterial photodynamic therapy’s chemical components. Future studies should support investigations on new approaches to improve or overcome the constraints of opportunities offered by photodynamic inactivation of caries-related biofilms.

Spectrophotometrical purity and stability testing of a photosensitizer based on an indotricarbocyanine dye

The express method for testing purity and stability of an indotricarbocyanine dye based photosensitizer for photodynamic therapy was developed. Storage of the hydrophilic photosensitizer under unfavorable conditions resulted in contamination with a hydrophobic dye. The absorption spectrum of the hydrophobic dye was characterized by a new band at 514 nm that was absent in the absorption spectrum of the photosensitizer. There was no spectral overlap between this absorption band and the absorbance of the photosensitizer. Therefore, presence of the band at 514 nm allowed us to detect contamination of the photosensitizer substance with the hydrophobic dye. It was established that the optimal photosensitizer concentration for purity testing is ca. 0.8 mmol/L, when as little as 0.6 wt. % of the impurity can be detected. The developed method is not time consuming and requires accessible equipment only. Data obtained with this method was verified with the aid of liquid chromatography-mass spectrometry.

Antibacterial Properties of Synthetic Cationic Bacteriochlorin Derivatives as Photosensitizers

Antibacterial photodynamic therapy (APDT) is a promising method of treatment of local infections, based on photochemical reaction of photosensitizer (PS) under irradiation with visible or near infra-red light of appropriate wavelength. A molecule of PS is activated by light energy and as a result singlet oxygen and other reactive oxygen species, which are toxic for microbes, are generated. Antibacterial action of new PS (synthetic polycationic bacteriochlorin derivatives with spectral maximum of absorbance at 760 nm) with improved features was investigated in vitro in this work. Tetra- and octacationic bacteriochlorins with lower molecular mass, as compared with ones previously proposed, turned out to be highly effective against Pseudomonas aeruginosa and Staphylococcus aureus in plankton and biofilm state: reduction of viable bacteria in biofilms reached 5log10. The dependence of the effect on PS concentration, the time of incubation with PS and light dose was ascertained. Light microscopy of biofilms after photodynamic treatment and Live/Dead staining confirmed the death of bacteria or damage of their membranes after exposure to PS and irradiation.

Tumor Microenvironment-Responsive Nanomaterials as Targeted Delivery Carriers for Photodynamic Anticancer Therapy.

Photodynamic therapy (PDT), as an alternative approach to treat tumors through reactive oxygen species (ROS) produced by the activated photosensitizers (PS) upon light irradiation, has attracted wide attention in recent years due to its low invasive and highly efficient features. However, the low hydrophilicity and poor targeting of PS limits the clinical application of PDT. Stimuli-responsive nanomaterials represent a major class of remarkable functional nanocarriers for drug delivery. In particular, tumor microenvironment-responsive nanomaterials (TMRNs) can respond to the special pathological microenvironment in tumor tissues to release the loaded drugs, that allows them to control the release of PS within tumor tissues. Recent studies have demonstrated that TMRNs can achieve the targeted release of PS at tumor sites, increase the concentration of PS in tumor tissues, and reduce side effects of PDT. Hence, in the present paper, we review TMRNs, mainly including pH-, redox-, enzymes-, and hypoxia-responsive smart nanomaterials, and focus on the application of these smart nanomaterials as targeted delivery carriers of PS in photodynamic anticancer therapy, to further boost the development of PDT in tumor therapy.

Metal center ion effects on photoinactivating rapidly growing mycobacteria using water-soluble tetra-cationic porphyrins.

Rapidly growing mycobacteria (RGM) are pathogens that belong to the mycobacteriaceae family and responsible for causing mycobacterioses, which are infections of opportunistic nature and with increasing incidence rates in the world population. This work evaluated the use of six water-soluble cationic porphyrins as photosensitizers for the antimicrobial photodynamic therapy (aPDT) of four RGM strains: Mycolicibacterium fortuitum, Mycolicibacterium smeagmatis, Mycobacteroides abscessus subs. Abscessus, and Mycobacteroides abscessus subsp. massiliense. Experiments were conducted with an adequate concentration of photosensitizer under white-light irradiation conditions over 90min and the results showed that porphyrins 1 and 2 (M = 2H or ZnII ion) were the most effective and significantly reduced the concentration of viable mycobacteria. The present work shows the result is dependent on the metal-center ion coordinated in the cationic porphyrin core. Moreover, we showed by atomic force microscopy (AFM) the possible membrane photodamage caused by reactive oxygen species and analyzed the morphology and adhesive force properties. Tetra-positively charged and water-soluble metalloporphyrins may be promising antimycobacterial aPDT agents with potential applications in medical clinical cases and bioremediation.

Antimicrobial photodynamic efficacy of selected natural photosensitizers against food pathogens: Impacts and interrelationship of process parameters.

Photodynamic treatment (PDT) could be a viable option to decontaminate food or food contact surfaces. Such applications require a rigorous method to assess the efficacy of different photosensitizer-light source systems. It is also essential to determine suitable treatment conditions to achieve desirable microbial inhibition for a given process. In this connection, we evaluated and compared the antimicrobial activity of two natural photosensitizers (aloe emodin, curcumin) under PDT based on the number of absorbed photons. The degree of bacterial inactivation was then correlated to the absorbed photons as well as the process parameters through kinetics study. The results showed that aloe emodin was more effective than curcumin against both S. aureus and E. coli when the number of absorbed photons was matched. Aloe emodin reduced about 2.3 log units of S. aureus and 1.1 log units of E. coli more than curcumin. E. coli was more resistant to PDT than S. aureus. Inactivation kinetics of S. aureus and E. coli as a function of the number of absorbed photons can be described by the Weibull model with D values of 1.296 × 1017 photons/cm2 and 2.446 × 1018 photons/cm2, R2 of 0.969 and 0.968, respectively. The interrelationship between the concentration of photosensitizer, radiant fluence, and degree of bacterial inactivation could be used to determine and optimize treatment conditions of PDT processes.

Spectroscopic features of PHOTOGEM® in human Rhabdomyosarcoma (RD) cellular model

Our study demonstrated the biological changes produced in the Rhabdomyosarcoma (RD) cell line triggered by the photochemical reaction between PHOTOGEM® (photosensitizing agent) and He-Ne laser light (wavelength = 632.8 nm of red light). The basic parameters of photodynamic therapy were optimized to study photosensitizer localization/uptake, PHOTOGEM® absorption spectra, cytotoxic effects, phototoxic effects, and morphological changes in the RD cell line. The experiment included three steps. First, spectrometric measurements were obtained to optimize the absorbance and optimal density of PHOTOGEM® in the experimental biological model (RD cell line). A neutral red assay was used to estimate the loss of cellular viability. Second, the RD cell line containing PHOTOGEM® was irradiated with laser light (dose up to 100 J/cm2). In addition, a non-fluorescent compound was used to determine the intracellular production of reactive oxygen species. The treated cells were examined and photographed. The optical density of the PHOTOGEM®-exposed RD cell line was insignificant after 0–2 h but increased significantly after 20 and 24 h. A photosensitizer concentration of 120 μg/ml and a red He-Ne laser dose of 100 J/cm2 having wavelength 632.8 nm produced the maximum phototoxic effect in the RD cell line. The cell viability of the PHOTOGEM®-labeled RD cells decreased to 65% in the absence of the laser dose, but there was significant cell viability loss under suitable laser exposure (100 J/cm2).

Peripheral tetra-cationic Pt(II) porphyrins photo-inactivating rapidly growing mycobacteria: First application in mycobacteriology

In this manuscript, we report, for the first time, the photoinactivation evaluation of tetra-cationic porphyrins with peripheral Pt (II)-bpy complexes in the photodynamic inactivation (PDI) of rapidly growing mycobacterial strains (RGM). Two different isomeric Pt (II)-porphyrins were synthetized and applied. PDI experiments in the strains of Mycobacteroides abscessus subsp. Abscessus (ATCC 19977), Mycolicibacterium fortuitum (ATCC 6841), Mycobacteroides abscessus subsp. Massiliense (ATCC 48898), and Mycolicibacterium smegmatis (ATCC 700084) conducted with adequate concentration (without aggregation) of photosensitizers (PS) under white-light illumination for 90 min showed that the most effective PS significantly reduced the concentration of viable mycobacteria. The present results show that positively charged porphyrins at the meta position (3-PtTPyP) are more efficient PS against M. abscessus, M. fortuitum, M. massiliense, and M. smegmatis. The effectiveness of the molecule as PS for PDI studies is also clear with mycobacteria, which is strongly related with the porphyrin peripheral charge and coordination platinum (II) compounds and consequently their solubility in physiological media. Tetra-cationic PS may be promising anti-mycobacterial PDI agents with potential applications in medical clinical cases and bioremediation.

Antibacterial photodynamic activity of photosensitizer-embedded alginate-pectin-carboxymethyl cellulose composite biopolymer films.

Antimicrobial photodynamic therapy (APDT) is a promising approach for treatment of wounds infected with antibiotic-resistant bacteria. In this approach, delivery of appropriate concentration of photosensitizer (PS) at the infected site is a critical step; it is therefore essential that PS need to be administered at the infected site in a suitable formulation. Here, we report preparation of PS-embedded composite biopolymer films and their photobactericidal properties against methicillin-resistant Staphylococcus aureus (MRSA) and biocompatibility. Sodium alginate (SA), pectin (PC), and carboxymethyl cellulose (CMC) were used for preparing films containing chlorin p6 (Cp6, anionic PS) or methylene blue (MB, cationic PS). Films containing 1% CMC (15 mm diameter; 110 ± 09 μm thickness) showed ~ 55% light transmission in 500 to 750 nm region and high swelling rate as indicated by ~ 38% increase in diameter within 1 h. Absorption spectroscopic studies of PS-embedded films revealed that while Cp6 existed mainly in monomeric state, MB existed in both dimeric and monomeric forms. MRSA incubated with the film for 1 h displayed substantial uptake of Cp6 and MB as indicated by the presence of Cp6 fluorescence and MB staining in cells under the microscope. Furthermore, photodynamic treatment (660 nm, 10 J/cm2) of MRSA with Cp6 embedded in film or free Cp6 resulted in ~ 3 log reduction in colony-forming units (cfu), whereas decrease in cfu was less (~ 1 log) for MB-embedded film than for free MB (~ 6 logs). Studies on human keratinocyte (HaCaT) cells showed that there was no significant change in the viability of cells when they were incubated with solubilized films (plain) for 24 h or subjected to treatment with PS-containing films followed by PDT. These results suggest that films are biocompatible and have potential application in photodynamic treatment of MRSA-infected wounds.

Reactive oxygen species explicit dosimetry to predict local tumor growth for Photofrin-mediated photodynamic therapy.

Although photodynamic therapy (PDT) is an established modality for cancer treatment, current dosimetric quantities, such as light fluence and PDT dose, do not account for the differences in PDT oxygen consumption for different fluence rates (ϕ). A macroscopic model was adopted to calculate reactive oxygen species concentration ([ROS]rx) to predict Photofrin-PDT outcome in mice bearing radiation-induced fibrosarcoma (RIF) tumors. Singlet oxygen is the primary cytotoxic species for ROS, which is responsible for cell death in type II PDT, although other type I ROS is included in the parameters used in our model. Using a combination of fluences (50-250 J∕cm2) and ϕ (75 or 150 mW∕cm2), tumor regrowth rate, k, was determined for each condition by fitting the tumor volume versus time to V0 *exp(k*t). Treatment was delivered with a collimated laser beam of 1 cm diameter at 630 nm. Explicit dosimetry of light fluence rate on tissue surface, tissue oxygen concentration, tissue optical properties, and Photofrin concentration were performed. Light fluence rate at 3 mm depth (ϕ 3mm) was determined for the treatment volume based on Monte-Carlo simulations and measured tissue optical properties. Initial tissue oxygenation [3 O 2]0 was measured by an Oxylite oxygen probe before PDT and used to calculate [ROS]rx,calc. This value was compared to [ROS]rx,meas as calculated with the entire tissue oxygen spectrum [3 O 2](t), measured over the duration of light delivery for PDT. Cure index, CI = 1-k/kctr , for tumor growth up to 14 days after PDT was predicted by four dose metrics: light fluence, PDT dose, and [ROS]rx,calc, and [ROS]rx,meas. PDT dose was defined as the product of the time-integral of photosensitizer concentration and ϕ at a 3 mm tumor depth. These studies show that [ROS]rx,meas best correlates with CI and is an effective dosimetric quantity that can predict treatment outcome.

Investigation of isomeric tetra-cationic porphyrin activity with peripheral [Pd(bpy)Cl]+ units by antimicrobial photodynamic therapy.

In this work, we report the antimicrobial photoinactivation using tetra-cationic porphyrins with peripheral palladium(II) complexes against bacterial strains. Two different isomeric Pd(II)-porphyrins were used and applied in PDI experiments in the strains Gram negative bacilli Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa and a Gram positive cocci Staphylococcus aureus. All experiments are conducted with adequate concentration (without aggregation) of photosensitizer under white-light irradiation over 2 h . We showed that the most effective PS caused a significative reduction in the concentration of viable bacteria. The present results show that porphyrin with positively charge at meta position (3-PtTPyP) are more efficient photosensitizer against bacteria strains. In this way, tetra-cationic porphyrins might be promising antibacterial PDI agents with potential applications in clinical cases.

Vaterite submicron particles designed for photodynamic therapy in cells.

Calcium carbonate (CaCO3) is one of the most abundant materials in the world. It has several different crystalline phases as present in the minerals: calcite, aragonite and vaterite, which are anhydrous crystalline polymorphs. Regarding the preparation of these microparticles, the most important aspect is the control of the polymorphism, particle size and material morphology. This study aimed to develop porous microparticles of calcium carbonate in the vaterite phase for the encapsulation of chloro-aluminum phthalocyanine (ClAlPc) as a photosensitizer (PS) for application in Photodynamic Therapy (TFD). In this study, spherical vaterite composed of microparticles are synthesized by precipitation route assisted by polycarboxylate superplasticizer (PSS). The calcium carbonate was prepared by reacting a mixed solution of Na2CO3 with a CaCl2 solution at an ambient temperature, 25 °C, in the presence of polycarboxylate superplasticizer as a stabilizer. The photosensitizer was incorporated by adsorption technique in the CaCO3 microparticles. The CaCO3 microparticles were studied by scanning electron microscopy, steady-state, and their biological activity was evaluated using in vitro cancer cell lines by trypan blue exclusion method. The intracellular localization of ClAlPc was examined by confocal microscopy. The CaCO3 microparticles obtained are uniform and homogeneously sized, non-aggregated, and highly porous microparticles. The calcium carbonate microparticles show an average size of 3 μm average pore size of about 30-40 nm. The phthalocyanine derivative loaded-microparticles maintained their photophysical behavior after encapsulation. The captured carriers have provided dye localization inside cells. The in vitro experiments with ClAlPc-loaded CaCO3 microparticles showed that the system is not cytotoxic in darkness, but exhibits a substantial phototoxicity at 3 μmol.L-1 of photosensitizer concentration and 10 J.cm-2 of light. These conditions are sufficient to kill about 80 % of the cells. All the performed physical-chemical, photophysical, and photobiological measurements indicated that the phthalocyanine-loaded CaCO3 microparticles are a promising drug delivery system for photodynamic therapy and photoprocesses.

The effect of indocyanine green-based photodynamic therapy on healthy fibroblast and keratinocyte cells.

Photodynamic therapy is a promising invention to treat infections and cancer where conventional treatments are insufficient and have many side effects. Photodynamic therapy is mainly emphasized as having minimal side effects on healthy cells during local applications, even so photosensitizer can accumulate in any cell and unwanted deaths may occur upon irradiation. This study focused on the degree of photodynamic action with indocyanine green against healthy cells, when it has phototoxic effects on pathogens. Healthy mouse skin fibroblast and human skin keratinocyte cells were exposed to energy densities of 84 and 252 J/cm2 with 4, 10, 25, 50,100, 125 and 150 μg/mL indocyanine green which have efficiently killed gram-positive and gram-negative pathogens. Cell Viability, Lipid Peroxidation and Live/Dead Cell Staining analysis were performed to assess the phototoxicity with defined parameters on the healthy cells. 84 J/cm2 energy density was quite safe for keratinocytes with indocyanine green concentrations ranging from 4 to 125 μg/mL. When 252 J/cm2 energy density was used, most of the keratinocytes were damaged with any photosensitizer concentration. Fibroblasts only tolerate these energy densities together with 4 and 10 μg/mL indocyanine green. Increasing photosensitizer concentrations resulted in high phototoxic effect on them. Photodynamic therapy applications, which destroy pathogens, may also kill healthy eukaryotic cells. While some energy densities are safe, but others cause serious mortality rate on fibroblasts and keratinocytes. Therefore, harm to healthy cells related to photodynamic therapy parameters should be minimized by the optimization of energy densities and photosensitizer concentration properly.