Photodynamic Inactivation Of Candida Albicans Research Articles

Extracts of Trichocline sinuata (Asteraceae) as natural sensitizers in the photodynamic inactivation of Candida albicans.

Despite significant progress in the development of phototherapy drugs, it is widely recognized that natural products remain the primary source of new photoactive compounds. Exploring uncharted flora in the east-central region of Argentina may offer a vast array of opportunities to isolate new photoactive molecules or plant extracts with high potential for use in antimicrobial photodynamic therapy (aPDT) against Candida albicans. To assess the photofungicidal potential of T. sinuata ("contrayerba") against C. albicans, the extracts underwent spectroscopic and chromatographic analysis, resulting in the identification of furanocoumarin metabolites with similar spectrophotometric properties in all extracts. The extract profiles were created using UHPLC-DAD, and seven furanocoumarins (FCs) were detected. The highest photoinactivation against C. albicans was observed for dicholormethanic extracts (MFC = 62.5 μg/mL), equal to xanthotoxin employed as a positive control. Furthermore, we determine that photochemical mechanisms dependent on oxygen (type I and type II processes) and mechanisms independent of oxygen (photoadduct formation) are involved in the death of these yeasts. These results support the use of native plants of the east-central region of Argentina as potent sensitizers for aPDT and suggest that they can replace xanthotoxin in treating superficial yeast infections of the skin.

Spatial Distribution of a Porphyrin-Based Photosensitizer Reveals Mechanism of Photodynamic Inactivation of Candida albicans.

The antimicrobial photodynamic therapy (aPDT) is a promising approach for the control of microbial and especially fungal infections such as mucosal mycosis. TMPyP [5,10,15, 20-tetrakis(1-methylpyridinium-4-yl)-porphyrin tetra p-toluenesulfonate] is an effective photosensitizer (PS) that is commonly used in aPDT. The aim of this study was to examine the localization of TMPyP in Candida albicans before and after irradiation with visible light to get information about the cellular mechanism of antifungal action of the photodynamic process using this PS. Immediately after incubation of C. albicans with TMPyP, fluorescence microscopy revealed an accumulation of the PS in the cell envelope. After irradiation with blue light the complete cell showed red fluorescence, which indicates, that aPDT is leading to a damage in the cell wall with following influx of PS into the cytosol. Incubation of C. albicans with Wheat Germ Agglutinin (WGA) could confirm the cell wall as primary binding site of TMPyP. The finding that the porphyrin accumulates in the fungal cell wall and does not enter the interior of the cell before irradiation makes it unlikely that resistances can emerge upon aPDT. The results of this study may help in further development and modification of PS in order to increase efficacy against fungal infections such as those caused by C. albicans.

Development and in vitro evaluation of buccal mucoadhesive films for photodynamic inactivation of Candida albicans.

Candidiasis is one of the most common diseases that occur in the oral cavity, caused mainly by the species Candida albicans. Methylene blue (MB) has a potential for microbial photoinactivation and can cause the destruction of fungi when applied in Photodynamic Therapy (PDT). Mucoadhesive films are increasingly being studied as a platform for drug application due to their advantages when compared to other pharmaceutical forms. The aim of this work was to develop mucoadhesive buccal film containing poloxamer 407 (P407), alcohol polyvinyl (PVA) and polyvinylpyrrolidone (PVP) for the release of MB aiming the photoinactivation of Candida albicans in buccal infections. Different amounts of P407 were added to the binary polymeric blends composed PVA and PVP. Formulations were characterized as morphology, thickness, density, bending strength, mechanical properties, water vapor transmission, disintegration time, mucoadhesion, DSC, ATR-FTIR, in vitro drug release profile and photodynamic inactivation. The films displayed physicochemical characteristics dependent of polymeric composition, mucoadhesive properties, fast MB release and were effective in photo inactivate the local growth of Candida albicans isolates. The formulation containing the lowest PVA and P407 amounts displayed the best performance. Therefore, data obtained from the film system show its potentially useful role as a platform for buccal MB delivery in photoinactivation of C. albicans, showing its potential for in vivo evaluation.

Efficient photodynamic inactivation of Candida albicans by porphyrin and potassium iodide co-encapsulation in micelles.

Photodynamic inactivation of bacterial and fungal pathogens is a promising alternative to the extensive use of conventional single-target antibiotics and antifungal agents. The combination of photosensitizers and adjuvants can improve the photodynamic inactivation efficiency. In this regard, it has been shown that the use of potassium iodide (KI) as adjuvant increases pathogen killing. Following our interest in this topic, we performed the co-encapsulation of a neutral porphyrin photosensitizer (designated as P1) and KI into micelles and tested the obtained nanoformulations against the human pathogenic fungus Candida albicans. The results of this study showed that the micelles containing P1 and KI displayed a better photodynamic performance towards C. albicans than P1 and KI in solution. It is noteworthy that higher concentrations of KI within the micelles resulted in increased killing of C. albicans. Subcellular localization studies by confocal fluorescence microscopy revealed that P1 was localized in the cell cytoplasm, but not in the nuclei or mitochondria. Overall, our results show that a nanoformulation containing a photosensitizer plus an adjuvant is a promising approach for increasing the efficiency of photodynamic treatment. Actually, the use of this strategy allows a considerable decrease in the amount of both photosensitizer and adjuvant required to achieve pathogen killing.

Mechanistic aspects in the photodynamic inactivation of Candida albicans sensitized by a dimethylaminopropoxy porphyrin and its equivalent with cationic intrinsic charges.

Photocytotoxic effect induced by 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (TAPP) and 5,10,15,20-tetrakis[4-(3-N,N,N-trimethylaminepropoxy)phenyl]porphyrin (TAPP+4) was examined in Candida albicans to obtain information on the mechanism of photodynamic action and cell damage. For this purpose, the photokilling of the yeast was investigated under anoxic conditions and cell suspensions in D2O. Moreover, photoinactivation of C. albicans was evaluated in presence of reactive oxygen species scavengers, such as sodium azide and d-mannitol. The results indicated that singlet molecular oxygen was the main reactive species involved in cell damage. On the other hand, the binding and distribution of these porphyrins in the cells was observed by fluorescence microscopy. Morphological damage was studied by transmission electron microscopy (TEM), indicating modifications in the cell envelopment. Furthermore, deformed cells were observed after photoinactivation of C. albicans by toluidine blue staining. In addition, modifications in the cell envelope due to the photodynamic activity was found by scanning electron microscopy (SEM). Similar photodamage was observed with both porphyrin, which mainly produced alterations in the cell barriers that lead to the photoinactivation of C. albicans.

The effect of glucose and human serum on 5-aminolevulinic acid mediated photodynamic inactivation of Candida albicans.

In response to the growing number of life-threatening infections caused by opportunistic Candida albicans fungi we have examined and discussed the effect of glucose and human serum on the efficiency of photosensitization of C. albicans cells with 5-aminolevulinic acid (5-ALA) used as a precursor of protoporphyrin IX (PpIX). We used 630 nm laser diode as an excitation source to enhance the penetration depth and diminish unwanted light scattering, additionally the experiments were performed in planktonic and biofilm cultures to differentiate the results obtained for cells showing various phenotypic characteristics. Based on performed experiments it became obvious that the incubation of C. albicans fungal cells with 5-ALA in the presence of glucose caused a significant increase in concentration of intracellular PpIX, resulting in a higher efficacy of photo-toxic effect. The observed results were rationalized by the role of glucose as an energy source, which supported the active transport of 5-ALA into cells. In contrary to glucose, the presence of human serum caused a significant reduction in PpIX concentration in C. albicans cells with exogenous delivery of 5-ALA, resulting in a less efficient photo-fungicidal effect. In general, the obtained results contributed to the current search for efficient, light activated anti-fungal treatments of high efficiency.

Photodynamic Inactivation of Candida albicans in Blood Plasma and Whole Blood.

The few approved disinfection techniques for blood derivatives promote damage in the blood components, representing risks for the transfusion receptor. Antimicrobial photodynamic therapy (aPDT) seems to be a promising approach for the photoinactivation of pathogens in blood, but only three photosensitizers (PSs) have been approved, methylene blue (MB) for plasma and riboflavin and amotosalen for plasma and platelets. In this study, the efficiency of the porphyrinic photosensitizer Tri-Py(+)-Me and of the porphyrinic formulation FORM was studied in the photoinactivation of Candida albicans in plasma and in whole blood and the results were compared to the ones obtained with the already approved PS MB. The results show that FORM and Tri-Py(+)-Me are promising PSs to inactivate C. albicans in plasma. Although in whole blood the inactivation rates obtained were higher than the ones obtained with MB, further improvements are required. None of these PSs had promoted hemolysis at the isotonic conditions when hemolysis was evaluated in whole blood and after the addition of treated plasma with these PSs to concentrates of red blood cells.

Singlet oxygen production by a polypyridine ruthenium (II) complex with a perylene monoimide derivative: A strategy for photodynamic inactivation of Candida albicans

We report the synthesis, optical, electrochemical and electronic properties of a new perylene derivative and its Ru(II) complex, namely N,-(5-amino-1,10-phenantroline)perylene-3,4,9,10-tetracarboximonoimide (pPDI) and Bis(1,10-phenanthroline)(N-(5-amin-1,10-phenantroline)perylene-3,4,9,10-tetracarboxi monoimide)ruthenium(II) hexafluorophosphate, [Ru(phen)2(pPDI)]2+ ([PF6]−)2. The molecular structures of the compounds were elucidated by FTIR, mass spectrometry, elemental analysis (CHN) and DFT calculations. Their optical and electrochemical properties were investigated by absorption and fluorescence spectroscopy and cyclic voltammetry. The spectroscopic and electrochemical studies for both the pPDI and the perylene monoimide metal complex show that Ru2+ coordination does not affect the optical and electrochemical properties of the free perylene bisimide ligand. The Ru complex exhibits emission lifetimes of 5.06 ns (48.1%) and 156 ns (51.9%), resulting from emission of the pPDI ligand and 3MLCT, respectively. The pPDI triplet excited state in the title chromophore is able to sensitize the production of singlet oxygen (1O2). Using a time-resolved laser system, we measured the quantum yield for the production of singlet oxygen (ΦΔ) to be 0.26 for cis-[Ru(phen)2(pPDI)]2+. Candida albicans is recognized as the most common fungal pathogens, causing superficial infections of the skin and mucous membranes. Resistance of C. albicans strains against classical antifungal agents such as fluconazole has increased considerably, which drives the search for new therapeutic alternatives. In the present study, we report that our new Ru-perylene complex can indeed be used to kill the bacterium C. albicans. The fungicidal activity of cis-[Ru(phen)2(pPDI)]2+ against C. albicans was evaluated in the presence of C. albicans cultures in the dark and in the presence of light. After exposure to 12.5 μM of cis-[Ru(phen)2(pPDI)]2 in the presence of light for 180 s, C. albicans showed a decrease of 50% in its concentration compared to the same experimental conditions in the dark.

Poly(propylene)-based Films Modified with a Tetracationic Phthalocyanine with Applications in Photodynamic Inactivation of Candida albicans

ABSTRACTPhotoactive films based on polymer-like poly(propylene) were generated and utilized as support of zinc(II)tetramethyltetrapyridino[2,3-b:2′,3′-g:2″,3″-l:2″′,3″′-q]porphyrazinium salt (ZnTM2,3PyPz). Using a photograft polymerization of acrylic acid, the poly(propylene) film was functionalized with carboxyl groups (PP-g-PAAc), which attached ZnTM2,3PyPz by electrostatic bond to form PP-g-PAAc-Pc films. In vitro investigations indicated that PP-g-PAAc-Pc films produced photodynamic inactivation of Candida albicans cells, mainly mediated by a contribution of type II process. According to the results, the photodynamic activity produced by the PP-g-PAAc-Pc film and visible light irradiation can successfully inactivate C. albicans deposited on the surface of the films.

Spray layer-by-layer films for photodynamic inactivation

BackgroundA novel approach for photodynamic inactivation of Candida albicans is proposed. This method consists of realizing inactivation using ultraviolet light (254nm) combined with spraying layer-by-layer films of acridine orange. MethodsTo evaluate the effectiveness of the approach, the C. albicans were immobilized on quartz slices and covered with the spray layer-by-layer films. The fungi were analyzed using experiments to determine cell viability, as well as by fluorescence and atomic force microscopy. ResultsViability analysis of C. albicans after photodynamic inactivation assisted by the films indicates cell death. The extent of cell death increases as the number of film layers increases. Fluorescence and atomic force microscopy analyses corroborated the cell death of C. albicans, which is posited to be due to damages to the fungi cell wall. ConclusionsOur approach has the potential to be used as an alternative for photodynamic inactivation of C. albicans. In addition, this method could be used in clinical procedures, such as for the decontamination of medical devices.

Photodynamic inactivation of Candida albicans by hematoporphyrin monomethyl ether.

To evaluate the capacity of hematoporphyrin monomethyl ether (HMME) in the presence of light to cause photodynamic inactivation (PDI) of Candida albicans. HMME photoactivity was evaluated against azole-susceptible and -resistant C. albicans. The mechanisms by which PDI of C. albicans occurred were also investigated. HMME-mediated PACT caused a dose-dependent inactivation of azole-susceptible and -resistant C. albicans. Incubation with 10 μM HMME and irradiation with 72 J cm(-2) light decreased the viability of C. albicans by 7 log10, induced damage of genomic DNA, led to loss of cellular proteins and damaged the cell wall, membrane and intracellular targets. Candida albicans can be effectively inactivated by HMME in the presence of light, and HMME-mediated PACT shows its potential as an antifungal treatment.

Photodynamic inactivation of Candida albicans by a tetracationic tentacle porphyrin and its analogue without intrinsic charges in presence of fluconazole

The photodynamic inactivation mediated by 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (TAPP) and 5,10,15,20-tetrakis[4-(3-N,N,N-trimethylaminepropoxy)phenyl]porphyrin (TAPP4+) were compared in Candida albicans cells. A strong binding affinity was found between these porphyrins and the yeast cells. Photosensitized inactivation of C. albicans increased with both photosensitizer concentration and irradiation time. After 30min irradiation, a high photoinactivation (∼5 log) was found for C. albicans treated with 5μM porphyrin. Also, the photoinactivation of yeast cells was still elevated after two washing steps. However, the photocytotoxicity decreases with an increase in the cell density from 106 to 108 cells/mL. The high photodynamic activity of these porphyrins was also established by growth delay experiments. This C. albicans strain was susceptible to fluconazole with a MIC of 1.0μg/mL. The effect of photosensitization and the action of fluconazole were combined to eradicate C. albicans. After a PDI treatment with 1μM porphyrin and 30min irradiation, the value of MIC decreased to 0.25μg/mL. In addition, a complete arrest in cell growth was found by combining both effects. TAPP was similarly effective to photoinactivate C. albicans than TAPP4+. This porphyrin without intrinsic positive charges contains basic amino groups, which can be protonated at physiological pH. Moreover, an enhancement in the antifungal action was found using both therapies because lower doses of the agents were required to achieve cell death.

In vitro photodynamic inactivation of Candida albicans by phenothiazine dye (new methylene blue) and Indocyanine green (EmunDo®)

The application of a new generation of photosensitizers to increase the efficacy of antifungal photodynamic therapy (aPDT) is an important aspect of PDT. Thus, this in vitro study is aimed to evaluate the antifungal efficacy of the photo-elimination of Candida albicans with photothermal and antifungal photodynamic therapy. aPDT with new methylene blue and photothermal therapy with EmunDo® were applied to a fungal suspension, which was then subcultured in Sabouraud dextrose agar (SDA). The C. albicans colonies were counted and are expressed as colony-forming unit per milliliter (CFU/ml). aPDT with either EmunDo® or new methylene blue (NMB) considerably diminished the viability of inoculated C. albicans (P<0.001) by log reduction of 1.9 and 3.37, respectively, compared with the control group respectively, compared with the control group. The antifungal potency or dark toxicity of the two photosensitizers alone did not significantly differ (P=0.70). The same trend was observed for the light sources (λ: 810nm vs. λ: 630nm), which also did not significantly differ (P=0.78). The photo-elimination of C. albicans with either new methylene blue or EmunDo® as a photosensitizer can reduce the viability of fungal cells. Although the result of this study is encouraging, further investigations are warranted to determine clear protocols for the reliable and safe application of this method in clinical practice.

Photodynamic inactivation of Candida albicans mediated by a low density of light energy

Shorter times and lower energies of application of light sources are desirable to use photodynamic antimicrobial chemotherapy (PACT) to the clinical control of candidiasis, especially among babies and children. Light energies ranging from 39.5 to 100 J/cm(2) were previously applied to kill Candida albicans by PACT. The present study evaluated the efficacy of a combination of 0.05 mg/mL toluidine blue O (TBO) and a short time of application (60 s) and a low density of light energy (18 J/cm(2)) of a red light-emitting diode (LED) in killing C. albicans planktonic cells. Standard suspensions of C. albicans were randomly assigned for four treatment groups: control (L-P-), LED alone (L+P-), TBO alone (L-P+), and PACT (L+P+). After treatments, serial dilutions of suspensions were prepared and streaked on Sabouraud dextrose agar to determine colony-forming units of C. albicans per milliliter (CFU/mL). The results were analyzed by ANOVA and Tukey's post-hoc test (P < 0.05). PACT significantly reduced CFUs of C. albicans in comparison to other three treatments. Our results demonstrated a fungicidal effect of PACT mediated by a shorter time of application of LED on C. albicans planktonic cells. Further in vivo studies are needed to elucidate the efficacy of PACT to treat human fungal infections.

Mechanistic aspects of the photodynamic inactivation of Candida albicans induced by cationic porphyrin derivatives

Photodynamic inactivation of Candida albicans produced by 5-(4-trifluorophenyl)-10,15,20-tris(4-N,N,N-trimethylammoniumphenyl)porphyrin (TFAP3+), 5,10,15,20-tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TMAP4+) and 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP4+) was investigated to obtain insight about the mechanism of cellular damage. In solution, absorption spectroscopic studies showed that these cationic porphyrins interact strongly with calf thymus DNA. The electrophoretic analysis indicated that photocleavage of DNA induced by TFAP3+ took place after long irradiation periods (>5 h). In contrast, TMAP4+ produced a marked reduction in DNA band after 1 h irradiation. In C. albicans, these cationic porphyrins produced a ∼3.5 log decrease in survival when the cell suspensions (107 cells/mL) were incubated with 5 μM photosensitizer and irradiated for 30 min with visible light (fluence 162 J/cm2). After this treatment, modifications of genomic DNA isolated from C. albicans cells were not found by electrophoresis. Furthermore, transmission electron microscopy showed structural changes with appearance of low density areas into the cells and irregularities in cell barriers. However, the photodamage to the cell envelope was insufficient to cause the release of intracellular biopolymers. Therefore, modifications in the cytoplasmic biomolecules and alteration in the cell barriers could be mainly involved in C. albicans photoinactivation.

Photodynamic inactivation of Candida albicans sensitized by a series of novel axially di-substituted silicon (IV) phthalocyanines

The photodynamic activities against Candida albicans have been evaluated for seven silicon (IV) phthalocyanines modified axially by different functional groups. The effects of the axial substituents on the spectroscopic, photochemical, cellular uptake, and photobiological properties of these silicon phthlaocyanines have been revealed. The dicationic compounds 2 and 4 , having two quaternary ammonium groups at the axial positions, exhibit the highest antifungal photocytotoxicity with an IC 90 of 61–66 μM, which can be ascribed to their high singlet oxygen quantum yield , non-aggregation nature, effective cellular uptake, and intracellular distribution pattern (localizing preferentially in the mitochondria). By comparison, compounds 2 and 4 show a higher photodynamic inactivation of C. albicans cells than methylene blue (MB), a known antifungal photosensitizer . The IC 90 values against C. albicans for 2 and 4 are ca. 8 times lower than that for MB. These results indicate that the dicationic silicon phthalocyanines 2 and 4 are interesting candidates as antifungal photosensitizers for future studies. ► Photodynamic inactivation of Candida albicans by a series of SiPcs was studied. ► The structure–activity relationship of these silicon phthalocyanines was discussed. ► The dicationic SiPcs 2 and 4 exhibit the highest antifungal photocytotoxicity. ► 2 and 4 show ca. 8 times higher photoactivities than methylene blue.

Photodynamic inactivation of Candida albicans using bridged polysilsesquioxane films doped with porphyrin

Novel photoactive bridged polysilsesquioxane films were prepared by doped with a porphyrin derivative. The films were formed by acid-catalyzed polycondensation reaction of a precursor of a bridged silsesquioxane, based on the reaction product of (glycidoxypropyl)trimethoxysilane with n-dodecylamine in the presence of 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl)porphyrin, followed by solvent evaporation. This procedure allowed obtaining flexible thin films. Absorption and fluorescence spectroscopic analysis showed the characteristic bands of the porphyrin in the visible region indicating that the photosensitizer is mainly embedded as monomer in the films. Photodynamic properties of the polymeric films were studied in solution containing photooxidizable substrates. Singlet molecular oxygen, O2(1Δg), production was observed by the reaction with 9,10-dimethylanthracene and 9,10-anthracenediyl-bis(methylene)dimalonic acid in different media. Also, these films photosensitized the decomposition of l-tryptophan. In vitro investigations showed that these films produce photodynamic inactivation of Candida albicans cells in aqueous suspensions and on their surfaces. These films exhibit a photosensitizing activity causing a ∼2.5 log (99.7%) decrease of cellular survival after 60min of irradiation with visible light. Also, the photocytotoxicity of the surfaces was tested under condition of microbial growth. Yeast cells exposed to the film and illuminated showed growth delay compared with controls. Studies of photodynamic action mechanism showed that the photoinactivation increased in D2O, while cells were protected in the presence of azide ion. In contrast, the addition of mannitol produced a negligible effect on the cellular phototoxicity. These results provide evidence that O2(1Δg) produced by the polymeric film doped with porphyrin can successfully inactivate C. albicans in cell suspensions and deposited on the film surface.

Influence of multidrug efflux systems on methylene blue-mediated photodynamic inactivation of Candida albicans

To investigate whether the major fungal multidrug efflux systems (MESs) affect the efficiency of methylene blue (MB)-mediated antimicrobial photodynamic inactivation (APDI) in pathogenic fungi and test specific inhibitors of these efflux systems to potentiate APDI. Candida albicans wild-type and mutants that overexpressed two classes of MESs [ATP-binding cassette (ABC) and major facilitator superfamily (MFS)] were tested for APDI using MB as the photosensitizer with and without addition of MES inhibitors. The uptake and cytoplasm localization of photosensitizer were achieved using laser confocal microscopy. ABC MES overexpression reduced MB accumulation and APDI killing more than MFS MES overexpression. Furthermore, by combining MB APDI with the ABC inhibitor verapamil, fungal killing and MB uptake were potentiated, while by combining MB APDI with the MFS inhibitor INF(271), fungal killing and MB uptake were inhibited. This latter surprising finding may be explained by the hypothesis that the MFS channel can also serve as an uptake mechanism for MB. The ABC pumps are directly implicated in MB efflux from the cell cytoplasm. Both the influx and efflux of MB may be regulated by MFS systems, and blocking this gate before incubation with MB can decrease the uptake and APDI effects. An ABC inhibitor could be usefully combined with MB APDI for treating C. albicans infections.

Photodynamic inactivation of Candida albicans sensitized by tri- and tetra-cationic porphyrin derivatives

The photodynamic action of 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide (TFAP 3+) and 5,10,15,20-tetra(4- N, N, N-trimethylammonium phenyl)porphyrin p-tosylate (TMAP 4+) has been studied in vitro on Candida albicans. The results of these cationic porphyrins were compared with those of 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS 4−), which characterizes an anionic sensitizer. In vitro investigations show that these cationic porphyrins are rapidly bound to C. albicans cells, reaching a value of ∼1.4 nmol/10 6 cells, when the cellular suspensions were incubated with 5 μM sensitizer for 30 min. In contrast, TPPS 4− is poorly uptaken by yeast cells. The fluorescence spectra of these sensitizers into the cells confirm this behaviour. The amount of porphyrin binds to cells is dependent on both sensitizer concentrations (1–5 μM) and cells densities (10 6–10 8 cells/mL). Photosensitized inactivation of C. albicans cellular suspensions increases with sensitizer concentration, causing a ∼5 log decrease of cell survival, when the cultures are treated with 5 μM of cationic porphyrin and irradiated for 30 min. However, the photocytotoxicity decreases with an increase in the cell density, according to its low binding to cells. Under these conditions, the photodynamic activity of TFAP 3+ is quite similar to that produced by TMAP 4+, whereas no important inactivation effect was found for TPPS 4 −. The high photodynamic activity of cationic porphyrins was confirmed by growth delay experiments. Thus, C. albicans cell growth was not detected in the presence of 5 μM TFAP 3+. Photodynamic inactivation capacities of these sensitizers were also evaluated on C. albicans cells growing in colonies on agar surfaces. Cationic porphyrins produce a growth delay of C. albicans colonies and viability of cells was not observed after 3 h irradiation, indicating a complete inactivation of yeast cells. Therefore, these results indicate that these cationic porphyrins are interesting sensitizers for photodynamic inactivation of yeasts in liquid suspensions or in localized foci of infection.