Photoinactivation Of Microorganisms Research Articles

Photoinactivation of microorganisms using bacteriochlorins as photosensitizers.

In recent years, some microorganisms have shown resistance to conventional treatments. Considering this increase in resistant pathogens, treatment alternatives are needed to promote greater treatment efficiency. In this sense, antimicrobial photodynamic therapy (aPDT) has been an alternative treatment. This technique uses a photosensitizer that is activated by light with a specific wavelength producing reactive species, leading to the death of pathogenic microorganisms. In this study, bacteriochlorophyll derivatives such as bacteriochlorin metoxi (Bchl-M) and bacteriochlorin trizma (Bchl-T) obtained from purple bacterium (Rhodopseudomonas faecalis), were evaluated as photosensitizers in the aPDT. Photodynamic inactivation (PDI) of the microorganisms Staphylococcus aureus, Micrococcus luteus, Candida albicans and Pseudomonas aeruginosa was investigated with both bacteriochlorins (Bchl-M and Bchl-T) at different concentrations (1, 15 and 30µM for S. aureus; 1, 15, 30, 45, 60 and 75µM for M. luteus; 30, 60, 90, 105, 120 and 150µM for C. albicans; and 200µM for P. aeruginosa) and different doses of light (20 and 30J/cm2 for S. aureus and M. luteus; 30 and 45J/cm2 for C. albicans; and 45J/cm2 for P. aeruginosa) to inactivate them. Both photosensitizers showed good activation against S. aureus and for M. luteus, we observed the inactivation of these microorganisms at approximately 3 log, showing to be a good photosensitizers for these microorganisms.

Photoinactivation of microorganisms and photodegradation of pollutants using phthalocyanines supported on nanofibers and glass wool

Neutral and cationic zinc and indium phthalocyanines (Pcs) are anchored onto polyacrylonitrile nanofibers (NFs) and glass wools (GWs). The properties of these composites were evaluated and compared. Thermal gravimetric analysis showed that GWs had higher stability than NFs. The nanofibers had a higher loading of > 50 % compared to < 35 % for glass wools. The singlet oxygen quantum yield was proportional to the loading. The degradation of 4-chlorophenol, methyl orange, and methylene blue, and the antimicrobial activity (photodynamic antimicrobial chemotherapy) of the composites were evaluated. It was revealed that the NFs showed a combination of photocatalytic and adsorption properties against methylene blue. The NFs degraded the organic pollutants faster than GWs. The cationic composites showed higher antimicrobial activities than their neutral derivates. The results show a promising application window of the cationic Pc-nanofibers.

Adsorption and Inactivation of SARS-CoV-2 on the Surface of Anatase TiO2(101)

We investigated the adsorption of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), the virus responsible for the current pandemic, on the surface of the model catalyst TiO2(101) using atomic force microscopy, transmission electron microscopy, fluorescence microscopy, and X-ray photoelectron spectroscopy, accompanied by density functional theory calculations. Three different methods were employed to inactivate the virus after it was loaded on the surface of TiO2(101): (i) ethanol, (ii) thermal, and (iii) UV treatments. Microscopic studies demonstrate that the denatured spike proteins and other proteins in the virus structure readsorb on the surface of TiO2 under thermal and UV treatments. The interaction of the virus with the surface of TiO2 was different for the thermally and UV treated samples compared to the sample inactivated via ethanol treatment. AFM and TEM results on the UV-treated sample suggested that the adsorbed viral particles undergo damage and photocatalytic oxidation at the surface of TiO2(101) which can affect the structural proteins of SARS-CoV-2 and denature the spike proteins in 30 min. The role of Pd nanoparticles (NPs) was investigated in the interaction between SARS-CoV-2 and TiO2(101). The presence of Pd NPs enhanced the adsorption of the virus due to the possible interaction of the spike protein with the NPs. This study is the first investigation of the interaction of SARS-CoV-2 with the surface of single crystalline TiO2(101) as a potential candidate for virus deactivation applications. Clarification of the interaction of the virus with the surface of semiconductor oxides will aid in obtaining a deeper understanding of the chemical processes involved in photoinactivation of microorganisms, which is important for the design of effective photocatalysts for air purification and self-cleaning materials.

Ultra-high irradiance (UHI) blue light: highlighting the potential of a novel LED-based device for short antifungal treatments of food contact surfaces.

Microbial food spoilage is an important cause of health and economic issues and can occur via resilient contamination of food surfaces. Novel technologies, such as the use of visible light, have seen the light of day to overcome the drawbacks associated with surface disinfection treatments. However, most studies report that photo-inactivation of microorganisms with visible light requires long time treatments. In the present study, a novel light electroluminescent diode (LED)-based device was designed to generate irradiation at an ultra-high power density (901.1 mW/cm2). The efficacy of this technology was investigated with the inactivation of the yeast S. cerevisiae. Short-time treatments (below 10 min) at 405 nm induced a ~4.5 log reduction rate of the cultivable yeast population. The rate of inactivation was positively correlated to the overall energy received by the sample and, at a similar energy, to the power density dispatched by the lamp. A successful disinfection of several food contact surfaces (stainless steel, glass, polypropylene, polyethylene) was achieved as S. cerevisiae was completely inactivated within 5 min of treatments. The disinfection of stainless steel was particularly effective with a complete inactivation of the yeast after 2 min of treatment. This ultra-high irradiance technology could represent a novel cost- and time-effective candidate for microbial inactivation of food surfaces. These treatments could see applications beyond the food industry, in segments such as healthcare or public transport. KEY POINTS : • A novel LED-based device was designed to emit ultra-high irradiance blue light • Short time treatments induced high rate of inhibition of S. cerevisiae • Multiple food contact surfaces were entirely disinfected with 5-min treatments.

Synthesis, spectroscopic properties and photodynamic activity of Zn(II) phthalocyanine-polymer conjugates as antimicrobial agents

Conjugates of Zn(II) phthalocyanine to chitosan (CS) and polyethylenimine (PEI) were synthetized through the following stages: first a phthalonitrile substituted by a (carbomethoxy)phenoxy group (Pn 1) was obtained by nucleophilic aromatic substitution reaction, then a AB3 Zn(II) phthalocyanines (ZnPc 2) was synthesized by the ring expansion reaction of boron(III) subphthalocyanine (SubPc) chloride with Pn 1. After hydrolysis of ZnPc 2, a Zn(II) phthalocyanine bearing a carboxylic acid group (ZnPc 3) was obtained, which was conjugated to CS (CH-ZnPc 4) and PEI (PEI-ZnPc 5) by amide bond. UV–visible absorption and fluorescence spectra presented the characteristic bands of the Zn(II) phthalocyanine in N,N-dimethylformamide (DMF), with appropriate fluorescence quantum yield. Also, the conjugation of Zn(II) phthalocyanine to polymers was confirmed by IR spectra. These conjugates were able to photosensitize singlet molecular oxygen in DMF and aqueous medium. Moreover, they induced the formation of superoxide anion radical in the presence of NADH. The results showed that type II pathway is involved in the photodecomposition of Trp sensitized by these conjugates, although there is also a contribution from the type I mechanism. Photoinactivation of microorganisms was investigated in Candida albicans, Staphylococcus aureus and Escherichia coli and, varying the concentration of CH-ZnPc 4 and PEI-ZnPc 5 and the irradiation times. Both conjugates were efficient in the eradication of S. aureus by PDI, while that PEI-ZnPc 5 was the most effective for photokilling C. albicans. These conjugates were little active to photoinactivation of E. coli. However, the addition of CS allowed to improve the photocytotoxicity towards this Gram-negative bacterium. These results indicate that PEI-ZnPc 5 is an efficient photosensitizer to inactivate S. aureus and C. albicans. In addition, it is capable of killing E. coli cells in the presence of CS.

Emerging Perspectives on Applications of Porphyrinoids for Photodynamic Therapy and Photoinactivation of Microorganisms

Emerging Perspectives on Applications of Porphyrinoids for Photodynamic Therapy and Photoinactivation of Microorganisms

Singlet Oxygen Photosensitizing Materials for Point‐of‐Use Water Disinfection with Solar Reactors

AbstractSinglet molecular oxygen (1O2) is a potent electrophile and a strong oxidizing agent and can be easily generated by photosensitization via illumination of appropriate dyes with visible light. This short‐lived reactive oxygen species is able to photooxidize many electron‐rich organic compounds and, therefore, 1O2 can damage many cellular components, such as membrane lipids, proteins and DNA, causing the photoinactivation of microorganisms in water. This Review summarises the most relevant work to date on solar water disinfection by photocatalytic 1O2 production, using photosensitizing materials suitable for their use in solar reactors for water treatment. The prototypes were equipped with compound parabolic collectors of sunlight and designed for point‐of‐use water treatment. The choice of the type of dye (RuII complexes or fullerenes) and polymeric support for the preparation of the 1O2 photosensitizing material, as well as the most important photophysical and operational parameters to be optimized to achieve efficient water disinfection with solar reactors, will be discussed.

Photoinactivation of Pseudomonas syringae pv. actinidiae in kiwifruit plants by cationic porphyrins

The studied cationic porphyrins formulation allows an effective photoinactivation of Pseudomonas syringae pv. actinidiae in kiwifruit leaves under sunlight irradiation, without damaging the plant. Pseudomonas syringae pv. actinidiae (Psa) is a Gram-negative phytopathogenic bacterium responsible for canker on kiwifruit plant. Over the last decade, this bacterium dramatically affected the production of this fruit worldwide, causing significant economic losses. In general, Psa control consists in the application of copper which are toxic and persist in the environment. The application of antimicrobial photodynamic therapy (aPDT) as an alternative to inactivate Psa has already been demonstrated in recent studies that showed a 4 log Psa reduction using the cationic porphyrin Tetra-Py+-Me as photosensitizer (PS) and 3 consecutive cycles of treatment with a light irradiance of 150 mWcm-2. The present work aimed to evaluate the photodynamic efficiency of a new formulation constituted with five cationic porphyrins as PS in Psa inactivation. This new formulation was prepared to have as main component the tri-cationic porphyrin which is considered one of the most efficient photosensitizers in the photoinactivation of microorganisms. The in vitro study with a PS concentration of 5.0µM and low irradiance, showed a 7.4 log photoinactivation after 60min. Posteriorly, several assays were performed with the PS at 50µM on kiwifruit leaves (ex vivo), under different conditions of light and inoculation. The ex vivo assays with artificially contaminated leaves showed a 2.8 and 4.5 log inactivation with low irradiance and sunlight, respectively, after 90min. After a second treatment with sunlight, a 6.2 log inactivation was achieved. The photoinactivation on naturally contaminated leaves was about 2.3 log after 90min sunlight irradiation. Ten consecutive cycles of phototreatment in sub-lethal conditions showed that Psa does not develop resistance, nor recover viability. The results suggest that aPDT can be an alternative to the current methods used to control Psa, since it was possible to inactivate this bacterium under sunlight, without damaging the leaves.

"Photo­antibiotics" ­ the light in the photoinactivation of microorganisms

"Photo­antibiotics" ­ the light in the photoinactivation of microorganisms

Sewage bacteriophage inactivation by cationic porphyrins: influence of light parameters

Photodynamic therapy has been used to inactivate microorganisms through the use of targeted photosensitizers. Although the photoinactivation of microorganisms has already been studied under different conditions, a systematic evaluation of irradiation characteristics is still limited. The goal of this study was to test how the light dose, fluence rate and irradiation source affect the viral photoinactivation of a T4-like sewage bacteriophage. The experiments were carried out using white PAR light delivered by fluorescent PAR lamps (40 W m(-2)), sun light (600 W m(-2)) and an halogen lamp (40-1690 W m(-2)). Phage suspensions and two cationic photosensitizers (Tetra-Py(+)-Me, Tri-Py(+)-Me-PF) at concentrations of 0.5, 1.0 and 5.0 microM were used. The results showed that the efficacy of the bacteriophage photoinactivation is correlated not only with the sensitizer and its concentration but also with the light source, energy dose and fluence rate applied. Both photosensitizers at 5.0 microM were able to inactivate the T4-like phage to the limit of detection for each light source and fluence rate. However, depending of the light parameters, different irradiation times are required. The efficiency of photoinactivation is dependent on the spectral emission distribution of the light sources used. Considering the same light source and a fixed light dose applied at different fluence rates, phage inactivation was significantly higher when low fluence rates were used. In this way, the light source, fluence rate and total light dose play an important role in the effectiveness of the antimicrobial photodynamic therapy and should always be considered when establishing an optimal antimicrobial protocol.

Heterogeneous photocatalysis in titania-containing liquid foam.

The possibility of effective photodegradation of chemical substrates and photoinactivation of microorganisms in liquid foam containing colloidal TiO(2) has been demonstrated.