Photoinactivation of Hepatitis A Virus by Synthetic Porphyrins¶

Antimicrobial activity of cationic water-soluble porphyrin against multidrug-resistant bacteria in biofilms and canine skin samples

Multidrug-resistant (MDR) microorganisms pose a threat to animal health, particularly in integumentary diseases, which can be caused by multiple organisms and often manifest as biofilms, hindering treatment effectiveness. We evaluated the antimicrobial activity of antimicrobial photodynamic therapy (aPDT) using a water-soluble tetra-cationic porphyrin (4-H2TMeP) against MDR bacteria cultured in biofilm and in mono and polyculture grown on canine skin samples. We utilized 4-H2TMeP porphyrin against MDR Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus pseudintermedius. A non-cytotoxic concentration of 4-H2TMeP (40 µM), previously shown to be effective in vitro against these bacteria cultured in solution, was employed. Biofilms were treated with 4-H2TMeP and subjected to light irradiation for 30, 60, and 90 min. Monocultures on canine skin samples were treated with 4-H2TMeP and irradiated for 30 (S. pseudintermedius), 60 (E. coli), or 60 and 90 min (P. aeruginosa). Polycultures of S. pseudintermedius and E. coli were treated with light for 60 and 90 min. The efficacy of aPDT was evaluated by plating light-exposed biofilms, mono and polycultures of bacteria obtained from skin samples exposed to light and kept in the dark. Colony-forming units were counted after 24 h of incubation at 37 °C. aPDT using 4-H2TMeP reduced bacterial concentrations of S. pseudintermedius and E. coli biofilms. Additionally, it significantly reduced bacterial concentrations cultivated on skin samples, with a particular emphasis on S. pseudintermedius. These findings indicate that aPDT with 4-H2TMeP is a promising alternative treatment against MDR bacteria in animal skin infections and should be further explored through in vivo research.

Antibiofilm action using water-soluble tetra-cationic porphyrin and antibacterial photodynamic therapy against Moraxella spp. from cattle

Infectious bovine keratoconjunctivitis (IBK) is the most important eye disease in ruminants worldwide. Moraxella bovis and Moraxella bovoculi can form biofilm and are frequently isolated from affected animals. Antimicrobials are used worldwide to treat clinical cases of IBK, although they have limited success in clearing the infection. Therefore, photodynamic therapy using porphyrins as photosensitizing molecules is an alternative method to eliminate microorganisms, including biofilms. We evaluated the antibacterial activity of a zinc(II) metalloporphyrin (ZnTMeP) against M. bovis and M. bovoculi biofilms since this compound can efficiently inactivate planktonic Moraxella spp. This study was carried out with two reference strains of Moraxella spp. (M. bovis: ATCC® 10900 and M. bovoculli: ATCC® BAA1259). The antibacterial activity of 4.0 μM of the ZnTMeP porphyrin was evaluated based on its ability to form and consolidate biofilms with three 30-min cycles of white-light exposure for three days. The ZnTMeP porphyrin reduced M. bovis and M. bovoculi biofilm formation. In addition, ZnTMeP partially destroyed consolidated M. bovoculi biofilms in the second white-light irradiation cycle, although the porphyrin had no effect against the consolidated biofilm of M. bovis. Despite the biofilm still not being completely inactivated, our findings are promising and encourage further experiments using the phototherapy protocol.

Translational feasibility and efficacy of nasal photodynamic disinfection of SARS-CoV-2

The lack of therapeutic options to fight Covid-19 has contributed to the current global pandemic. Despite the emergence of effective vaccines, development of broad-spectrum antiviral treatment remains a significant challenge, in which antimicrobial photodynamic therapy (aPDT) may play a role, especially at early stages of infection. aPDT of the nares with methylene blue (MB) and non-thermal light has been successfully utilized to inactivate both bacterial and viral pathogens in the perioperative setting. Here, we investigated the effect of MB-aPDT to inactivate human betacoronavirus OC43 and SARS-CoV-2 in vitro and in a proof-of-principle COVID-19 clinical trial to test, in a variety of settings, the practicality, technical feasibility, and short-term efficacy of the method. aPDT yielded inactivation of up to 6-Logs in vitro, as measured by RT-qPCR and infectivity assay. From a photo-physics perspective, the in vitro results suggest that the response is not dependent on the virus itself, motivating potential use of aPDT for local destruction of SARS-CoV-2 and its variants. In the clinical trial we observed variable effects on viral RNA in nasal-swab samples as assessed by RT-qPCR attributed to aPDT-induced RNA fragmentation causing falsely-elevated counts. However, the viral infectivity in clinical nares swabs was reduced in 90% of samples and undetectable in 70% of samples. This is the first demonstration based on quantitative clinical viral infectivity measurements that MB-aPDT is a safe, easily delivered and effective front-line technique that can reduce local SARS-CoV-2 viral load.

Pulsed blue light, saliva and curcumin significantly inactivate human coronavirus

In a recent study, we showed that pulsed blue light (PBL) inactivates as much as 52.3% of human beta coronavirus HCoV-OC43, a surrogate of SARS-CoV-2, and one of the major strains of viruses responsible for the annual epidemic of the common cold. Since curcumin and saliva are similarly antiviral and curcumin acts as blue light photosensitizer, we used Qubit fluorometry and WarmStart RT-LAMP assays to study the effect of combining 405 nm, 410 nm, 425 nm or 450 nm wavelengths of PBL with curcumin, saliva or a combination of curcumin and saliva against human beta coronavirus HCoV-OC43. The results showed that PBL, curcumin and saliva independently and collectively inactivate HCoV-OC43. Without saliva or curcumin supplementation 21.6 J/cm2 PBL reduced HCoV-OC43 RNA concentration a maximum of 32.8% (log10 = 2.13). Saliva supplementation alone inactivated the virus, reducing its RNA concentration by 61% (log10 = 2.23); with irradiation the reduction was as much as 79.1%. Curcumin supplementation alone decreased viral RNA 71.1%, and a maximum of 87.8% with irradiation. The combination of saliva and curcumin reduced viral RNA to 83.1% and decreased the RNA up to 90.2% with irradiation. The reduced levels could not be detected with qPCR. These findings show that PBL in the range of 405 nm to 450 nm wavelength is antiviral against human coronavirus HCoV-OC43, a surrogate of the COVID-19 virus. Further, it shows that with curcumin as a photosensitizer, it is possible to photodynamically inactivate the virus beyond qPCR detectable level using PBL. Since HCoV-OC43 is of the same beta coronavirus family as SARS-CoV-2, has the same genomic size, and is often used as its surrogate, these findings heighten the prospect of similarly inactivating novel coronavirus SARS-CoV-2, the virus responsible for COVID-19 pandemic.

3,6,13,16-Tetraalkylporphycenes: Synthesis and Exploration of Effect of Alkyl Groups on Structure, Photophysical Properties, and Basicity

Two new 3,6,13,16-tetraalkylporphycenes were synthesized following rational approach. The reason behind lower yield of the desired β,β'-bipyrroles was unraveled. The σ-donating effect of alkyl-substituents was more profound than reported positional...

Antimicrobial Photodynamic Approach in the Inactivation of Viruses in Wastewater: Influence of Alternative Adjuvants

Pathogenic viruses are frequently present in marine and estuarine waters, due to poor wastewater (WW) treatments, which consequently affect water quality and human health. Chlorination, one of the most common methods used to ensure microbiological safety in tertiarily treated effluents, may lead to the formation of toxic chemical disinfection by-products on reaction with organic matter present in the effluents. Antimicrobial photodynamic therapy (aPDT) can be a promising disinfecting approach for the inactivation of pathogens, without the formation of known toxic by-products. Additionally, some studies have reported the potentiator effect on aPDT of some compounds, such as potassium iodide (KI) and hydrogen peroxide (H2O2). In the present study, the aPDT efficiency of a PS formulation constituted of five cationic porphyrins (Form) in the inactivation of E. coli T4-like bacteriophage, a model of mammalian viruses, in different aqueous matrices with different organic matter content, was evaluated. Photoinactivation studies were performed at different concentrations of Form and in the presence of the adjuvants KI and H2O2. The results showed that the efficiency of bacteriophage photoinactivation is correlated with the Form concentration, the amount of the organic matter in WW, and the adjuvant type. Form can be an effective alternative to controlling viruses in WW, particularly if combined with H2O2, allowing to significantly reduce PS concentration and treatment time. When combined with KI, the Form is less effective in inactivating T4-like bacteriophage in WW.

A Comparison of Porphyrin Photosensitizers in Photodynamic Inactivation of RNA and DNA Bacteriophages

Effective broad-spectrum antiviral treatments are in dire need as disinfectants and therapeutic alternatives. One such method of disinfection is photodynamic inactivation, which involves the production of reactive oxygen species from dissolved oxygen in response to light-stimulated photosensitizers. This study evaluated the efficacy of functionalized porphyrin compounds for photodynamic inactivation of bacteriophages as human virus surrogates. A blue-light light emitting diode (LED) lamp was used to activate porphyrin compounds in aqueous solution (phosphate buffer). The DNA bacteriophages ΦX174 and P22 were more resistant to porphyrin TMPyP photodynamic inactivation than RNA bacteriophage fr, with increasing rates of inactivation in the order: ΦX174 << P22 << fr. Bacteriophage ΦX174 was therefore considered a resistant virus suitable for the evaluation of three additional porphyrins. These porphyrins were synthesized from TMPyP by inclusion of a central palladium ion (PdT4) and/or the addition of a hydrophobic C14 chain (PdC14 or C14). While the inactivation rate of bacteriophage ΦX174 via TMPyP was similar to previous reports of resistant viruses, ΦX174 inactivation increased by a factor of approximately 2.5 using the metalloporphyrins PdT4 and PdC14. The order of porphyrin effectiveness was TMPyP < C14 < PdT4 < PdC14, indicating that both Pd²⁺ ligation and C14 functionalization aided virus inactivation.

Novel Cationic Meso-Arylporphyrins and Their Antiviral Activity against HSV-1

This work is devoted to the search for new antiherpes simplex virus type 1 (HSV-1) drugs among synthetic tetrapyrroles and to an investigation of their antiviral properties under nonphotodynamic conditions. In this study, novel amphiphilic 5,10,15,20-tetrakis(4-(3-pyridyl-n-propanoyl)oxyphenyl)porphyrin tetrabromide (3a), 5,10,15,20-tetrakis(4-(6-pyridyl-n-hexanoyl)oxyphenyl)porphyrin tetrabromide (3b) and known 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetraiodide (TMePyP) were synthesized, and their dark antiviral activity in vitro against HSV-1 was studied. The influence of porphyrin’s nanosized delivery vehicles based on Pluronic F127 on anti-HSV-1 activity was estimated. All the received compounds 3a, 3b and TMePyP showed virucidal efficiency and had an effect on viral replication stages. The new compound 3b showed the highest antiviral activity, close to 100%, with the lowest concentration, while the maximum TMePyP activity was observed with a high concentration; porphyrin 3a was the least active. The inclusion of the synthesized compounds in Pluronic F-127 polymeric micelles had a noticeable effect on antiviral activity only at higher porphyrin concentrations. Action of the received compounds differs by influence on the early or later reproduction stages. While 3a and TMePyP acted on all stages of the viral replication cycle, porphyrin 3b inhibited viral replication during the early stages of infection. The resulting compounds are promising for the development of utilitarian antiviral agents and, possibly, medical antiviral drugs.

Light-based technologies for management of COVID-19 pandemic crisis

The global dissemination of the novel coronavirus disease (COVID-19) has accelerated the need for the implementation of effective antimicrobial strategies to target the causative agent SARS-CoV-2. Light-based technologies have a demonstrable broad range of activity over standard chemotherapeutic antimicrobials and conventional disinfectants, negligible emergence of resistance, and the capability to modulate the host immune response. This perspective article identifies the benefits, challenges, and pitfalls of repurposing light-based strategies to combat the emergence of COVID-19 pandemic.

The Application of Porphyrins and Their Analogues for Inactivation of Viruses

The problem of treating viral infections is extremely relevant due to both the emergence of new viral diseases and to the low effectiveness of existing approaches to the treatment of known viral infections. This review focuses on the application of porphyrin, chlorin, and phthalocyanine series for combating viral infections by chemical and photochemical inactivation methods. The purpose of this review paper is to summarize the main approaches developed to date in the chemical and photodynamic inactivation of human and animal viruses using porphyrins and their analogues and to analyze and discuss the information on viral targets and antiviral activity of porphyrins, chlorins, of their conjugates with organic/inorganic compounds obtained in the last 10–15 years in order to identify the most promising areas.

In vitro antimicrobial photodynamic therapy using tetra-cationic porphyrins against multidrug-resistant bacteria isolated from canine otitis

Antimicrobial-resistant bacteria have been frequently isolated from canine otitis. Photodynamic therapy using porphyrins as photosensitizing molecules is an alternative therapy against microorganisms in localized infections. Therefore, we evaluated the antibacterial activity of two tetra-cationic porphyrins (H₂TMeP and ZnTMeP) against gram-positive and -negative bacteria isolated from canine otitis, as well as its putative action mechanism. For this, two gram-positive and two gram-negative bacteria frequently detected in cases of canine otitis (coagulase-positive and -negative staphylococci [CPS and CNS], Pseudomonas aeruginosa, and Proteus mirabilis) were used in antibacterial activity assays. Each porphyrin at a non-cytotoxic dose was incubated with a fixed concentration of each bacterium and exposed to white-light irradiation for 0, 30, 60, and 90 min. Clinical isolates of CPS and CNS were photo-inactivated after 30 min of white-light exposure by both porphyrins (p < 0.05). Gram-negative bacteria were also photo-inactivated after 30 min (p < 0.05), reaching complete inactivation after 60 and 90 min of white-light irradiation by H₂TMeP and ZnTMeP, respectively. Antibacterial assays using standard bacterial strains (ATCCs) demonstrated similar results to those obtained with clinical isolates, except for P. aeruginosa, which was completely inactivated by ZnTMeP at 60 min, and the absence of a significant reduction in P. mirabilis concentration when irradiated for 30 min. Similar assays were conducted using reactive oxygen species scavengers showing that the putative mechanism for bacterial inactivation is through the production of singlet oxygen species. These results indicated that H₂TMeP and ZnTMeP tetra-cationic porphyrins were effective against bacteria isolated from canine otitis.

Antibacterial activity of Cu(II) and Co(II) porphyrins: role of ligand modification

In this study, we report antibacterial activity of metalloporphyrins; 5, 10, 15, 20-tetrakis (para-X phenyl)porphyrinato M (II) [where X = H, NH₂ and COOMe for M = Cu and X = COOH  and OMe for M = Co]. The activity study of the as-synthesized metalloporphyrins toward two Gram-positive (S. aureus and S. pyogenes) and two Gram-negative (E. coli and K. pneumoniae) bacteria showed a promising inhibitory activity. Among the complexes under study, the highest antibacterial activity is observed for 5, 10, 15, 20-tetrakis (p-carboxyphenyl)porphyrinato cobalt (II), with inhibition zone of 16.5 mm against Staphylococcus aureus (S. aureus). This activity could be attributed to the high binding ability of COOH group to cellular components, membranes, proteins, and DNA as well as the lipophilicity of the complex. Moreover, consistent with literature report, the study revealed that metalloporphyrins with electron withdrawing group at para-positions have better antibacterial activity than metalloporphyrin which possess electron donating group at para position.

Water-soluble tetra-cationic porphyrins display virucidal activity against Bovine adenovirus and Bovine alphaherpesvirus 1

Porphyrins are photoactive compounds that can absorb the energy of light and transfer it to oxygen molecules, producing reactive oxygen species (ROS). Once produced, ROS may alter biological molecules and cellular mechanisms, leading to cell apoptosis or inactivation of microorganisms, such as bacteria, fungi, and viruses. Therefore, the objective of this study was to evaluate the in vitro virucidal activity of six tetra-cationic porphyrins against two bovine viruses (Bovine alphaherpesvirus 1, BoHV-1, enveloped; and Bovine adenovirus, BAV, non-enveloped). For this, viral suspensions were incubated with each porphyrin (H₂TMeP, ZnTMeP, and CuTMeP at 4.0 μM, NiTMeP at 5.0 μM, and CoClTMeP and MnClTMeP at 1.0 μM) and exposed to white-light irradiation for 0, 60, 120, and 180 min (BAV) or 0, 30, 60, 90, and 120 min (BoHV-1). Then, the remaining viral titers were determined by limiting dilution and compared with the control (virus + porphyrins without light exposition). The porphyrins H₂TMeP and ZnTMeP showed the highest virucidal activity against both viruses. ZnTMeP inactivated BoHV-1 after 30 min of photoactivation and H₂TMeP after 60 min. The BAV was photo-inactivated by both porphyrins at 180 min of white-light exposition. CuTMeP, NiTMeP, and CoClTMeP porphyrins had weak virucidal activity against BoHV-1 and MnClTMeP showed no virucidal activity against both viruses. These results indicated that free-base H₂TMeP and ZnTMeP porphyrins present virucidal activity against non-enveloped and enveloped viruses, opening the possibility for their use to inactivate viruses on surfaces, biological substrates, and solutions.

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.

Photodynamic inactivation of selected bovine viruses by isomeric cationic tetra-platinated porphyrins

Porphyrin-based photodynamic processes have been used for the inactivation of microorganisms and treatment of tumors. The virucidal activity of porphyrins 3-PtTPyP and 4-PtTPyP was investigated against bovine viruses representative of the main structural groups (enveloped/non-enveloped, DNA/RNA: BVDV, BoHV-1, BAV and BEV), and against two epitheliotropic viruses (VSV and VACV). Viral suspensions were incubated at 0.91 [Formula: see text]mol [Formula: see text] L[Formula: see text] and exposed to a white-light LED array source (25 mW [Formula: see text] cm[Formula: see text]; 90 J [Formula: see text] cm[Formula: see text] for 0, 15, 30 and 60 min followed by determination of the remaining virus titers. Porphyrin 3-PtTPyP reduced almost 6 log of VSV and 3.5 log of BVDV titers after 15 min and complete virus photoinactivation was achieved after 30 min. 4-PtTPyP at 0.91 [Formula: see text]mol [Formula: see text] L[Formula: see text] produced reduction of titers of all enveloped virus depending on the time of light irradiation. No virucidal activity of any of the porphyrins was observed for non-enveloped viruses and these results showed the potential of porphyrins to inactivate viruses in premises.

Photodynamic inactivation for in vitro decontamination of Staphylococcus aureus in whole blood

BACKGROUND

Blood can be the target of microbial cells in the human body. Erythrocytes, platelets, and plasma concentrates in blood bags used in hemotherapy for blood transfusion are contamination targets, which can trigger serious diseases in blood. These infections can cause septicemia that can lead to death if not recognized rapidly and treated adequately. The aim of this study was to evaluate the photodynamic inactivation in the in vitro decontamination of Staphylococcus aureus in whole blood, erythrocytes and platelet-rich plasma.

METHODS

Photodynamic inactivation using light doses of 10, 15 and 30 J/cm² at 630 nm and an hematoporphyrin-derivative photosensitizer (Photogem®) solutions at 25 and 50 μg/mL were evaluated. Toxicity of treatment was determined by hemolysis and cell viability assays.

RESULTS

The S. aureus reduction in phosphate buffered saline (PBS), whole blood, erythrocytes and platelet-rich plasma at 15 J/cm² and 50 μg/mL were 7.2, 1.0, 1.3 and 0.4 log CFU/mL, respectively. Quantitative and qualitative analyses were performed in whole blood samples, and Photogem® showed a low risk of hemolysis (10.7%) in whole blood. However, 100% of erythrocytes suffered hemolysis in the absence of plasma. The cell viability assay showed 13.9% of apoptosis in erythrocytes, but normal platelet viability.

CONCLUSION

S. aureus inactivation of whole blood samples using 50 μg/mL Photogem® and 15 J/cm² resulted in better outcomes, providing promising indications for treatment of bacterial contamination of blood, and in this work, alternative possibilities to apply the technique for blood decontamination are discussed.

Trends and targets in antiviral phototherapy

Photodynamic therapy (PDT) is a well-established treatment option in the treatment of certain cancerous and pre-cancerous lesions. Though best-known for its application in tumor therapy, historically the photodynamic effect was first demonstrated against bacteria at the beginning of the 20^th century. Today, in light of spreading antibiotic resistance and the rise of new infections, this photodynamic inactivation (PDI) of microbes, such as bacteria, fungi, and viruses, is gaining considerable attention. This review focuses on the PDI of viruses as an alternative treatment in antiviral therapy, but also as a means of viral decontamination, covering mainly the literature of the last decade. The PDI of viruses shares the general action mechanism of photodynamic applications: the irradiation of a dye with light and the subsequent generation of reactive oxygen species (ROS) which are the effective phototoxic agents damaging virus targets by reacting with viral nucleic acids, lipids and proteins. Interestingly, a light-independent antiviral activity has also been found for some of these dyes. This review covers the compound classes employed in the PDI of viruses and their various areas of use. In the medical area, currently two fields stand out in which the PDI of viruses has found broader application: the purification of blood products and the treatment of human papilloma virus manifestations. However, the PDI of viruses has also found interest in such diverse areas as water and surface decontamination, and biosafety.

Advances in aPDT based on the combination of a porphyrinic formulation with potassium iodide: Effectiveness on bacteria and fungi planktonic/biofilm forms and viruses

The increasing world-wide rate of antibiotic resistance as well as the capacity of microorganisms to form biofilms, have led to a higher incidence of mortal infections that require alternative methods for their control. Antimicrobial photodynamic therapy (aPDT) emerged as an effective solution against resistant strains. The present work aims to evaluate the aPDT efficiency of a photosensitizer (PS) based on a low-cost formulation constituted by five cationic porphyrins (FORM) and its potentiation effect by KI on a broad spectrum of microorganisms under white light (380–700 nm, 25 W/m[Formula: see text]. The aPDT assays were performed with different concentrations of FORM (0.1 to 5.0 [Formula: see text]M) and 100 mM of KI on planktonic and biofilm forms of gram-positive (methicillin resistant Staphylococcus aureus–MRSA) and gram-negative (Escherichia coli resistant to chloramphenicol and ampicillin) bacteria, of the fungi Candida albicans and on a T4-like bacteriophage as a mammalian virus model. The results indicate that the FORM alone is an efficient PS to photoinactivate not only gram-negative and gram-positive bacteria, but also C. albicans, in planktonic and biofilm forms, and T4-like phage at low concentrations (<5.0 [Formula: see text]M). The presence of KI enhanced the photodynamic effect of this FORM for all microorganisms on the planktonic form, allowing the reduction of PS concentration and treatment time. The results also show that the combination FORM/KI is highly efficient in the elimination of already well-established biofilms of E. coli,S. aureus and C. albicans. This effect is probably associated with longer-lived iodine reactive species produced during the aPDT treatment.

Antimicrobial activity and safety applications of meso-tetra(4-pyridyl)platinum(II) porphyrin

Tetra-platinated(II) porphyrin hexafluorophosphate compound (4-PtTPyPor) was synthetized and along 5,10,15,20-tetrakis(4-pyridyl)porphyrin (4-TPyPor), evaluated about the antimicrobial activity and safety. The effect was evaluated with and without light exposition. The antimicrobial activity was analyzed by microdilution and growth curve method. The assays showed an increase of antimicrobial potential caused by porphyrins with light exposition comparing the treatment without light irradiation. The biocompatibility was tested by MTT, ROS production, dsDNA on culture medium and hemolysis. All platinum porphyrin concentrations showed hemolytic activity under light exposition. The ROS measurement doesn't showed statistic difference between treatments and control. The picogreen assay demonstrates a reduction of dsDNA on culture medium with cells treated with porphyrins under light irradiation. The study demonstrated that the platinated porphyrins might be promising microbial photodynamic inactivation with potential applications in wastewater treatment, biofilm control and bioremediation.

Photodynamic inactivation of bacteriophage MS2: The A-protein is the target of virus inactivation

Singlet oxygen mediated oxidation has been shown to be responsible for photodynamic inactivation (PDI) of viruses in solution with photosensitisers such as 5, 10, 15, 20-tetrakis (1-methyl-4-pyridinio) porphyrin tetra p-toluenesulfonate (TMPyP). The capsids of non-enveloped viruses, such as bacteriophage MS2, are possible targets for viral inactivation by singlet oxygen oxidation. Within the capsid (predominantly composed of coat protein), the A-protein acts as the host recognition and attachment protein. The A-protein has two domains; an α-helix domain and a β-sheet domain. The α-helix domain is attached to the viral RNA genome inside the capsid while the β-sheet domain, which is on the surface of the capsid, is believed to be the site for attachment to the host bacteria pilus during infection. In this study, 4 sequence-specific antibodies were raised against 4 sites on the A-protein. Changes induced by the oxidation of singlet oxygen were compared to the rate of PDI of the virus. Using these antibodies, our results suggest that the rate of PDI is relative to loss of antigenicity of two sites on the A-protein. Our data further showed that PDI caused aggregation of MS2 particles and crosslinking of MS2 coat protein. However, these inter- and intra-capsid changes did not correlate to the rate of PDI we observed in MS2. Possible modes of action are discussed as a means to gaining insight to the targets and mechanisms of PDI of viruses.

Mechanisms of Vesicular Stomatitis Virus Inactivation by Protoporphyrin IX, Zinc-Protoporphyrin IX, and Mesoporphyrin IX

Virus resistance to antiviral therapies is an increasing concern that makes the development of broad-spectrum antiviral drugs urgent. Targeting of the viral envelope, a component shared by a large number of viruses, emerges as a promising strategy to overcome this problem. Natural and synthetic porphyrins are good candidates for antiviral development due to their relative hydrophobicity and pro-oxidant character. In the present work, we characterized the antiviral activities of protoprophyrin IX (PPIX), Zn-protoporphyrin IX (ZnPPIX), and mesoporphyrin IX (MPIX) against vesicular stomatitis virus (VSV) and evaluated the mechanisms involved in this activity. Treatment of VSV with PPIX, ZnPPIX, and MPIX promoted dose-dependent virus inactivation, which was potentiated by porphyrin photoactivation. All three porphyrins inserted into lipid vesicles and disturbed the viral membrane organization. In addition, the porphyrins also affected viral proteins, inducing VSV glycoprotein cross-linking, which was enhanced by porphyrin photoactivation. Virus incubation with sodium azide and α-tocopherol partially protected VSV from inactivation by porphyrins, suggesting that singlet oxygen (¹O₂) was the main reactive oxygen species produced by photoactivation of these molecules. Furthermore, ¹O₂ was detected by 9,10-dimethylanthracene oxidation in photoactivated porphyrin samples, reinforcing this hypothesis. These results reveal the potential therapeutic application of PPIX, ZnPPIX, and MPIX as good models for broad antiviral drug design.

Porphyrin-based cationic amphiphilic photosensitisers as potential anticancer, antimicrobial and immunosuppressive agents

Photodynamic therapy (PDT) combines a photosensitiser, light and molecular oxygen to induce oxidative stress that can be used to kill pathogens, cancer cells and other highly proliferative cells. There is a growing number of clinically approved photosensitisers and applications of PDT, whose main advantages include the possibility of selective targeting, localised action and stimulation of the immune responses. Further improvements and broader use of PDT could be accomplished by designing new photosensitisers with increased selectivity and bioavailability. Porphyrin-based photosensitisers with amphiphilic properties, bearing one or more positive charges, are an effective tool in PDT against cancers, microbial infections and, most recently, autoimmune skin disorders. The aim of the review is to present some of the recent examples of the applications and research that employ this specific group of photosensitisers. Furthermore, we will highlight the link between their structural characteristics and PDT efficiency, which will be helpful as guidelines for rational design and evaluation of new PSs.

An effective and potentially safe blood disinfection protocol using tetrapyrrolic photosensitizers

Aim: Conventional disinfection techniques, considered safe for plasma, are usually associated with collateral damages on concentrated platelets and erythrocytes. Alternative methods are required and antimicrobial photodynamic therapy (aPDT) seems promising. In this study the effectiveness of two photosensitizers (PS), a porphyrin and a phthalocyanine, to disinfect blood products was evaluated. Results: The cationic porphyrin was more effective in the photoinactivation of bacteria. Also, no significant osmotic stress was found for samples treated with PS at 5.0 µM in isotonic conditions after antimicrobial photodynamic therapy. Conclusion: Effective reduction of Gram-positive bacteria at 5.0 µM of PS provided promising indications toward its safe use to disinfect blood samples. For Gram-negative bacteria, lower PS concentrations, between 5.0 and 10 µM, must be tested.

Fine-tuning recA expression in Staphylococcus aureus for antimicrobial photoinactivation: importance of photo-induced DNA damage in the photoinactivation mechanism

Bacterial cell envelope is generally accepted as the primary target for a photo-induced oxidative stress. It is plausible that DNA damage occurs during the antimicrobial photoinactivation. Here we investigate the correlation between DNA damage and photoinactivation by evaluating the level of RecA-based DNA repair system in Staphylococcus aureus. By using exogenous photosensitizers (new methylene blue (NMB), toluidine blue O (TBO), 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP), zinc phthalocyanine (ZnPc), Rose Bengal (RB)) and ALA-induced endogenous porphyrin-dependent blue light (405 nm), several outcomes were observed: (i) an increase of DNA damage (from gel electrophoresis in DNA damage assay), (ii) an increase of recA expression (luminescence assay in recA-lux strain), and (iii) an increase of RecA protein level (Western blotting). When recA expression was repressed by novobiocin, or abolished by deleting the gene, S. aureus susceptibility towards photoinactivation was increased at approximately a hundred-fold. The absence of RecA increases DNA damage to yield bactericidal effect. In novobiocin-resistant mutant (gyrB), as opposed to wild type, neither RecA protein level nor cell’s susceptibility was affected by photoinactivation (when novobiocin is present). This is to suggest that GyrB-dependent inhibition mediated recA repression. Therefore, we have established the role of RecA in DNA damage during photoinactivation. With the use of rifampicin mutation frequency and Ames tests, we demonstrated that photoinactivation did not increase S. aureus mutagenesis and potentially is not mutagenic toward eukaryotic cells. The results suggest that the treatment is considered safe. In conclusion, we provide an evidence that recA inhibitor may serve as therapeutic adjuvant for antimicrobial photoinactivation. Clinical relevance of our findings warrants further investigations.

Theoretical investigation of the absorption spectra and singlet-triplet energy gap of positively charged tetraphenylporphyrins as potential photodynamic therapy photosensitizers

DFT and TD-DFT calculations have been performed on a series of positively charged tetraphenylporphyrins with the aim to check whether these compounds can be used as photosensitizers in photodynamic therapy (PDT). Absorption spectra and singlet-triplet energy gaps have been computed by using the BP86, PBE0, and ωB97XD exchange-correlation functionals. Polarizable continuum model (PCM) has been used to take into account solvent effects. A careful analysis has been made on the Q-band, localized in the near-red visible region of the spectrum, since it plays a fundamental role in the drug design of new photodynamic therapy photosensitizers. Our results show that all the examined molecules have an adsorption band that falls in the so-called therapeutic window and possess a singlet-triplet energy gap able to promote the excitation of molecular oxygen from its ground triplet to the excited singlet state. The use of the ωB97XD exchange correlation functional, which accounts for dispersion interactions, allows calculating excitation energy values close to the experimental values.

Effect of support pore size on antiviral activity of the heterogeneous photosensitizer with phthalocyanine covalently linked to aminopropyl silica gel

New heterogeneous photodynamic sensitizers, in which the active phase, (polycholinyl)tetra-3-phenylthiophthalocyanine of aluminum, grafted to aminopropylated silica gels with pore sizes of 10, 25 and 75 nm, were tested in MS2 coli phage and poliovirus photoinactivation. In aqueous suspensions of the photosensitizers, the photoantiviral activity of the active phase was observed. It was found that both phthalocyanine and viruses cannot penetrate into 10 and 25 nm pores. In the sample with 75 nm pores, both the active phase and virus localize predominantly inside pores, providing conditions for most efficient photovirucidal activity.

Photodynamic inactivation of mammalian viruses and bacteriophages

Photodynamic inactivation (PDI) has been used to inactivate microorganisms through the use of photosensitizers. The inactivation of mammalian viruses and bacteriophages by photosensitization has been applied with success since the first decades of the last century. Due to the fact that mammalian viruses are known to pose a threat to public health and that bacteriophages are frequently used as models of mammalian viruses, it is important to know and understand the mechanisms and photodynamic procedures involved in their photoinactivation. The aim of this review is to (i) summarize the main approaches developed until now for the photodynamic inactivation of bacteriophages and mammalian viruses and, (ii) discuss and compare the present state of the art of mammalian viruses PDI with phage photoinactivation, with special focus on the most relevant mechanisms, molecular targets and factors affecting the viral inactivation process.

Light-activated nanotube-porphyrin conjugates as effective antiviral agents

Porphyrins have been used for photodynamic therapy (PDT) against a wide range of targets like bacteria, viruses and tumor cells. In this work, we report porphyrin-conjugated multi-walled carbon nanotubes (NT-P) as potent antiviral agents. Specifically, we used Protoporphyrin IX (PPIX), which we attached to acid-functionalized multi-walled carbon nanotubes (MWNTs). We decided to use carbon nanotubes as scaffolds because of their ease of recovery from a solution through filtration. In the presence of visible light, NT-P was found to significantly reduce the ability of Influenza A virus to infect mammalian cells. NT-P may be used effectively against influenza viruses with little or no chance of them developing resistance to the treatment. Furthermore, NT-P can be easily recovered through filtration which offers a facile strategy to reuse the active porphyrin moiety to its fullest extent. Thus NT-P conjugates represent a new approach for preparing ex vivo reusable antiviral agents.

Reducing Vibrio load in Artemia nauplii using antimicrobial photodynamic therapy: a promising strategy to reduce antibiotic application in shrimp larviculture

We propose antimicrobial photodynamic therapy (aPDT) as an alternative strategy to reduce the use of antibiotics in shrimp larviculture systems. The growth of a multiple antibiotic resistant Vibrio harveyi strain was effectively controlled by treating the cells with Rose Bengal and photosensitizing for 30 min using a halogen lamp. This resulted in the death of > 50% of the cells within the first 10 min of exposure and the 50% reduction in the cell wall integrity after 30 min could be attributed to the destruction of outer membrane protein of V. harveyi by reactive oxygen intermediates produced during the photosensitization. Further, mesocosm experiments with V. harveyi and Artemia nauplii demonstrated that in 30 min, the aPDT could kill 78.9% and 91.2% of heterotrophic bacterial and Vibrio population respectively. In conclusion, the study demonstrated that aPDT with its rapid action and as yet unreported resistance development possibilities could be a propitious strategy to reduce the use of antibiotics in shrimp larviculture systems and thereby, avoid their hazardous effects on human health and the ecosystem at large.

Vicente MG, Luguya R, Norton J, Fronczek FR, Smith KM. Effect of overall charge and charge distribution on cellular uptake, distribution and phototoxicity of cationic porphyrins in HEp2 cells

Five cationic porphyrins bearing one to four -N(CH(3))(3)(+) groups linked to the p-phenyl positions of 5,10,15,20-tetraphenylporphyrin (TPP) were synthesized in order to study the effect of overall charge and its distribution on the cellular uptake, phototoxicity and intracellular localization using human carcinoma HEp2 cells. The di-cationic porphyrins DADP-o and DADP-a accumulated the most within cells and preferentially localize within vesicular compartments and in mitochondria. Of these two only DADP-a was phototoxic to the cells (IC(50)=3 microM at 1 J/cm(2)). The mono-cationic porphyrin MAP was found to be the most phototoxic of the series, and it localized mainly in lipid membranes, including the plasma membrane, ER, mitochondria, and Golgi. Both the tri-cationic porphyrin TRAP and the tetra-cationic porphyrin TEAP localized subcellularly mainly in the mitochondria, but of the two only TEAP showed moderate phototoxicity (IC(50)=8 microM at 1 J/cm(2)). Our results suggest that MAP is the most promising PDT photosensitizer, and that both DADP-o and TRAP might find application as transport vehicles for therapeutics into cells.

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.

Phage therapy and photodynamic therapy: low environmental impact approaches to inactivate microorganisms in fish farming plants

Owing to the increasing importance of aquaculture to compensate for the progressive worldwide reduction of natural fish and to the fact that several fish farming plants often suffer from heavy financial losses due to the development of infections caused by microbial pathogens, including multidrug resistant bacteria, more environmentally-friendly strategies to control fish infections are urgently needed to make the aquaculture industry more sustainable. The aim of this review is to briefly present the typical fish farming diseases and their threats and discuss the present state of chemotherapy to inactivate microorganisms in fish farming plants as well as to examine the new environmentally friendly approaches to control fish infection namely phage therapy and photodynamic antimicrobial therapy.

Sewage bacteriophage photoinactivation by cationic porphyrins: a study of charge effect

Photodynamic therapy has been used to inactivate microorganisms through the use of targeted photosensitizers. Recently the inactivation of bacteria in residual waters has been reported, but nothing is known about photoinactivation of environmental bacteriophages, which are often used as indicators of human enteric viruses. In this study we tested the effect of six cationic porphyrin derivatives with two to four charges on the photoinactivation of a sewage bacteriophage. A phage suspension of 5 x 10(7) PFU mL(-1) was exposed to white light (40 W m(-2)), during 270 min, at three photosensitizer concentrations (0.5, 1.0 and 5.0 microM). Tetra- and tricationic porphyrins inactivated the T4-like sewage phage to the limits of detection, but dicationic porphyrins did not lead to a significant decrease in phage viability. At the highest photosensitizer concentration (5.0 microM), the phage was completely inactivated (>99.9999% of inactivation, reduction of 7.2 log) after 270 min by the tetracationic porphyrin. Two of the tricationic derivatives also led to phage inactivation to the limit of detection. The rate of bacteriophage photoinactivation and the efficiency of the photosensitizer appeared to vary with the charge and with the substituents in the meso-positions of the porphyrin macrocycle. Tetra- and tricationic porphyrins can, therefore, be used as a new method for inactivating sewage bacteriophages that are frequently used as human enteric virus indicators. The complete inactivation of viruses with low light intensity means that this methodology can be used even on cloudy days and during winter, opening the possibility to develop new technologies for wastewater treatment.

Comparison of the efficiency and the specificity of DNA-bound and free cationic porphyrin in photodynamic virus inactivation

The risk of transmitting infections by blood transfusion has been substantially reduced. However, alternative methods for inactivation of pathogens in blood and its components are needed. Application of photoactivated cationic porphyrins can offer an approach to remove non-enveloped viruses from aqueous media. Here we tested the virus inactivation capability of meso-Tetrakis(4-N-methylpyridyl)porphyrin (TMPyP) and meso-Tri-(4-N-methylpyridyl)monophenylporphyrin (TMPyMPP) in the dark and upon irradiation. T7 bacteriophage, as a surrogate on non-enveloped viruses was selected as a test system. TMPyP and TMPyMPP reduce the viability of T7 phage already in the dark, which can be explained by their selective binding to nucleic acid. Both compounds proved to be efficient photosensitizers of virus inactivation. The binding of porphyrin to phage DNA was not a prerequisite of phage photosensitization, moreover, photoinactivation was more efficiently induced by free than by DNA bound porphyrin. As optical melting studies and agarose gel electrophoresis of T7 nucleoprotein revealed, photoreactions of TMPyP and TMPyMPP affect the structural integrity of DNA and also of viral proteins, despite their selective DNA binding.

Interaction of cationic meso-porphyrins with liposomes, mitochondria and erythrocytes

Two series of cationic porphyrins meso-(3N-methylpyridinium)phenylporphyrin (3P1, 3P2c, 3P2t, 3P3 and 3P4) and meso-(4N-methylpyridinium)phenylporphyrin (4P1, 4P2c, 4P2t, 4P3 and 4P4) were studied to obtain a comprehensive understanding of factors that influence the binding of cationic porphyrins to liposomes and mitochondria, as well as their photodynamic efficiencies in erythrocytes. Binding and photodynamic efficiency were found to be inversely proportional to the number of positively charged groups and directly proportional to n-octanol/water partition coefficients (log P(OW)), except for the cis molecules 3P2c and 4P2c. In the cis molecules, binding and photodynamic efficiency were much higher than expected, indicating that specific interactions not accounted by log P(OW) enhance photodynamic efficiency. The effect of mitochondrial transmembrane electrochemical potentials on cationic porphyrin binding constants was estimated to be as large as 15%, and may be useful to selectively target this organelle when promoting photodynamic therapy to induce apoptosis.

Real-time fluorogenic reverse transcription-PCR assays for detection of bacteriophage MS2

Bacteriophage MS2 is used in place of pathogenic viruses in a wide variety of studies that range from testing of compounds for disinfecting surfaces to studying environmental transport and fate of pathogenic viruses in groundwater. MS2 is also used as a pathogen simulant in the research, development, and testing (including open air tests) of methods, systems, and devices for the detection of pathogens in both the battlefield and homeland defense settings. PCR is often used as either an integral part of such detection systems or as a reference method to assess the sensitivity and specificity of microbial detection. To facilitate the detection of MS2 by PCR, we describe here a set of real-time fluorogenic reverse transcription-PCR assays. The sensitivity of the assays (performed with primer pairs and corresponding dye-labeled probes) ranged from 0.4 to 40 fg of MS2 genomic RNA (200 to 20,000 genome equivalents). We also demonstrate the usefulness of the primer pairs in assays without dye-labeled probe that included the DNA-binding dye SYBR green. None of the assays gave false-positive results when tested against 400 pg of several non-MS2 nucleic acid targets.