New phthalocyanines for photodynamic virus inactivation in red blood cell concentrates

Smart stimuli-responsive drug delivery systems in spotlight of COVID-19

The world has been dealing with a novel severe acute respiratory syndrome (SARS-CoV-2) since the end of 2019, which threatens the lives of many people worldwide. COVID-19 causes respiratory infection with different symptoms, from sneezing and coughing to pneumonia and sometimes gastric symptoms. Researchers worldwide are actively developing novel drug delivery systems (DDSs), such as stimuli-responsive DDSs. The ability of these carriers to respond to external/internal and even multiple stimuli is essential in creating "smart" DDS that can effectively control dosage, sustained release, individual variations, and targeted delivery. To conduct a comprehensive literature survey for this article, the terms "Stimuli-responsive", "COVID-19″ and "Drug delivery" were searched on databases/search engines like "Google Scholar", "NCBI", "PubMed", and "Science Direct". Many different types of DDSs have been proposed, including those responsive to various exogenous (light, heat, ultrasound and magnetic field) or endogenous (microenvironmental changes in pH, ROS and enzymes) stimuli. Despite significant progress in DDS research, several challenging issues must be addressed to fill the gaps in the literature. Therefore, this study reviews the drug release mechanisms and applications of endogenous/exogenous stimuli-responsive DDSs while also exploring their potential with respect to COVID-19.

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.

Photodynamic treatment of pathogens

The current viral pandemic has highlighted the compelling need for effective and versatile treatments, that can be quickly tuned to tackle new threats, and are robust against mutations. Development of such treatments is made even more urgent in view of the decreasing effectiveness of current antibiotics, that makes microbial infections the next emerging global threat. Photodynamic effect is one such method. It relies on physical processes proceeding from excited states of particular organic molecules, called photosensitizers, generated upon absorption of visible or near infrared light. The excited states of these molecules, tailored to undergo efficient intersystem crossing, interact with molecular oxygen and generate short lived reactive oxygen species (ROS), mostly singlet oxygen. These species are highly cytotoxic through non-specific oxidation reactions and constitute the basis of the treatment. In spite of the apparent simplicity of the principle, the method still has to face important challenges. For instance, the short lifetime of ROS means that the photosensitizer must reach the target within a few tens nanometers, which requires proper molecular engineering at the nanoscale level. Photoactive nanostructures thus engineered should ideally comprise a functionality that turns the system into a theranostic means, for instance, through introduction of fluorophores suitable for nanoscopy. We discuss the principles of the method and the current molecular strategies that have been and still are being explored in antimicrobial and antiviral photodynamic treatment.

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.

Photodynamic viral inactivation: Recent advances and potential applications

Antibiotic-resistant bacteria, which are growing at a frightening rate worldwide, has put the world on a long-standing alert. The COVID-19 health crisis reinforced the pressing need to address a fast-developing pandemic. To mitigate these health emergencies and prevent economic collapse, cheap, practical, and easily applicable infection control techniques are essential worldwide. Application of light in the form of photodynamic action on microorganisms and viruses has been growing and is now successfully applied in several areas. The efficacy of this approach has been demonstrated in the fight against viruses, prompting additional efforts to advance the technique, including safety use protocols. In particular, its application to suppress respiratory tract infections and to provide decontamination of fluids, such as blood plasma and others, can become an inexpensive alternative strategy in the fight against viral and bacterial infections. Diverse early treatment methods based on photodynamic action enable an accelerated response to emerging threats prior to the availability of preventative drugs. In this review, we evaluate a vast number of photodynamic demonstrations and first-principle proofs carried out on viral control, revealing its potential and encouraging its rapid development toward safe clinical practice. This review highlights the main research trends and, as a futuristic exercise, anticipates potential situations where photodynamic treatment can provide a readily available solution.

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.

Antiviral photodynamic therapy: Inactivation and inhibition of SARS-CoV-2 in vitro using methylene blue and Radachlorin

Introduction

Recently, the COVID-19 pandemic has spread globally, necessitating the development of new methods for its prevention and treatment. The purpose of this study was to evaluate the antiviral activity of photodynamic therapy (PDT) against SARS-CoV-2 in vitro.

Methods

Vero E6 cells and SARS-CoV-2 isolated in Russia were used for PDT with methylene blue (MB) and Radachlorin. A continuous laser with wavelength λ = 662 nm in doses of 16 J/cm² and 40 J/cm² laser irradiation was used for PDT of a viral suspension and SARS-CoV-2-infected cells. The direct cytopathogenic effect of SARS-CoV-2 was evaluated via light microscopy to calculate the TCID₅₀ in the samples and perform statistical analysis.

Results

Viral suspensions of SARS-CoV-2 that had a TCID₅₀ greater than 10³ were inactivated by PDT in the presence of MB and Radachlorin. Vero E6 cells were protected from 10⁴ TCID₅₀ of SARS-CoV-2 by PDT post infection. The range of protective concentrations was 1.0–10.0 μg/ml and 0.5–5.0 μg/ml for MB and Radachlorin, respectively. Additionally, it was found that MB and Radachlorin also possess significant antiviral activity even without PDT. The 50 % inhibitory concentration (IC₅₀) against 10² TCID₅₀ of SARS-CoV-2 was found to be 0.22 and 0.33 μg/mL with the addition of MB and Radachlorin, respectively, to cells concomitantly with virus, whereas in the case of applying the photosensitizers at 3.5 h post infection, the IC₅₀ was 0.6 and 2.0 μg/mL for MB and Radachlorin, respectively.

Conclusion

PDT shows high antiviral activity against SARS-CoV-2 when combined with MB and Radachlorin in vitro.

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.

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.

Tetrakis(ethyl-4(4-butyryl)oxyphenyl)porphyrinato zinc complexes with 4,4'-bpyridin: synthesis, characterization, and its catalytic degradation of Calmagite

This work reports on the synthesis and characterization of a new porphyrins complex:[Zn(TEBOP)(4,4'-bpy)](4,4'-bipyridine)(5,10,15,20-(tetraethyl-4(4-butyryl)oxyphenyl)porphyrinato)zinc(ii) (3). Single crystal X-ray diffraction, photophysical and electrochemical characteristics were studied. The prepared complex, penta-coordinated zinc(ii) porphyrin derivatives shows moderate ruffling distortion and the zinc atom is nearly planar with the porphyrin core. Tolyl and ethyl-4(4-butyryl)oxyphenyl) moieties at the meso positions present a bathochromic shift of the absorption bands, and a notable increase in the absorption coefficient of the Q(0,0) and Q(0,1) bands was observed with a higher fluorescence quantum yield and lifetime compared with the free base porphyrin. The electrochemical investigation shows a reversible reduction of the synthesized complexes. The catalytic power and the adsorption properties of the prepared complexes were studied for Calmagite degradation, an azoic organic dye. The results reveal that the studied compounds could be used as catalysts for the decolourisation of dyes in the presence of H2O2.

Axially Decorated SiIV -phthalocyanines Bearing Mannose- or Ammonium-conjugated Siloxanes: Comparative Bacterial Labeling and Photodynamic Inactivation<sup/>

Herein, we present a comparative study about the photoinactivation of Staphylococcus aureus (Gram-positive model) and Escherichia coli (Gram-negative model) employing a neutral and a dicationic axially functionalized Si^IV -phthalocyanine. Depending on the charge of the siloxane moiety (neutral monosaccharide or cationic ammonium salt), different interactions with the bacteria were observed, and a differential photoinactivation was facilitated. The intensity of the fluorescence labeling correlated with the photoinactivation of the two types of bacteria: While the neutral species only significantly affected the Gram-positive cells, we observed that the positively charged photosensitizer interacted both with the Gram-positive and with the Gram-negative models. The dicationic photosensitizer labeled both models with a characteristic deep-red fluorescence and photoinactivated both classes of prokaryotes. In general, our study clearly demonstrates that axially ammoniumsiloxane-functionalized Si(IV) phthalocyaninates constitute excellent photosensitizers due to their weak aggregation in aqueous environments. In particular, we also show that charge-based targeting with axial ammonium groups leads toward broad-spectrum Si^IV -phthalocyanines for photodynamic inactivation of bacteria.

Ground state charge transfer complex formation of some metalloporphyrins with aromatic solvents: Further theoretical and experimental investigations

In our earlier work (Chem. Phys. Letts. 592 (2014) 149-154), a new broad band was observed in the near infrared region (700-900nm) of the steady state absorption spectra of some metalloporphyrins (zinc tetraphenylporphyrin, zinc octaethylporphyrin and magnesium octaethylporphyrin) in aromatic solvents (chlorobenzene, 1,2-dichlorobenzene, benzonitrile, benzene and toluene) at high concentrations (~10^-4molL^-1). The band was ascribed to be due to ground state charge transfer complexation between solute and solvent molecules. In the present work, density functional theory calculations are carried out to study the possibility of such ground state charge transfer complex formation between zinc tetraphenylporphyrin and four aromatic solvents viz., benzene, toluene, chlorobenzene and benzonitrile with 1:1 and 2:1 solvent-solute stoichiometries. Also, we determined the association constants for the ground state charge transfer complex formation of zinc tetraphenylporphyrin and zinc octaethylporphyrin with two aromatic solvents (benzene and benzonitrile) by Benesi-Hildebrand method.

Recent Patents on Light-Based Anti-Infective Approaches

BACKGROUND

Antibiotic resistance is one of the most serious health threats to modern medicine. The lack of potent antibiotics puts us at a disadvantage in the fight against infectious diseases, especially those caused by antibiotic-resistant microbial strains. To this end, an urgent need to search for alternative antimicrobial approaches has arisen. In the last decade, light-based anti-infective therapy has made significant strides in this fight to combat antibiotic resistance among various microbial strains. This method includes utilizing antimicrobial blue light, antimicrobial photodynamic therapy, and germicidal ultraviolet irradiation, among others. Light-based therapy is advantageous over traditional antibiotics in that it eradicates microbial cells rapidly and the likelihood of light-resistance development by microbes is low.

METHODS

This review highlights the patents on light-based therapy that were filed approximately within the last decade and are dedicated to eradicating pathogenic microorganisms. The primary database that was used for the search was Google Patents. The searches were performed using the keywords including blue light, antimicrobial photodynamic therapy, ultraviolet irradiation, antibiotic resistance, disinfection, bacterium, fungus, and virus.

RESULTS

Forty-five patents were obtained in our search: 9 patents for the antimicrobial blue light approach, 21 for antimicrobial photodynamic therapy, 11 for UV irradiation, and lastly 4 for other light-based anti-infective approaches. The treatments and devices discussed in this review are interestingly enough able to be used in various different functions and settings, such as dental applications, certain eye diseases, skin and hard surface cleansing, decontamination of internal organs (e.g., the stomach), decontamination of apparel and equipment, eradication of pathogenic microorganisms from buildings and rooms, etc. Most of the devices and inventions introduce methods of destroying pathogenic bacteria and fungi without harming human cells and tissues.

CONCLUSIONS

Light-based antimicrobial approaches hold great promise for the future in regards to treating antibiotic-resistant infections and related diseases.

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.

Solvatochromic Stokes shift and determination of excited state dipole moments of free base and zinc octaethylporphyrin

Solvent effects on the photophysical properties of free base octaethylporphyrin and zinc octaethylporphyrin are investigated at the ambient temperature (300 K). Steady state electronic absorption and emission spectra of the porphyrins are recorded in different organic solvents of varying polarity. By using solvatochromic Stokes shift method, the dipole moments associated with the first excited singlet states of the presently used porphyrin molecules are determined for the first time, to the best of our knowledge, from Lippert-Mataga, Bakhshiev and Reichardt equations. The dipole moments associated with the singlet ground state of the porphyrin molecules are calculated theoretically by using density functional theory (DFT) method by adopting B3LYP/6-31G(d,p) level using Gaussian 03 package. Moreover, some other photophysical properties (fluorescence quantum yield, fluorescence lifetime, decay rates, etc.) of the porphyrins are measured in different solvents of varying polarity.

Photodynamic inactivation of bacteria and viruses using two monosubstituted zinc(II) phthalocyanines

A zinc(II) phthalocyanine substituted with a triamino moiety and its tri-N-methylated analogue have been prepared and characterized with various spectroscopic methods. Both compounds remain non-aggregated in N,N-dimethylformamide and in water containing 0.05% Cremophor EL (v/v), and can generate singlet oxygen effectively. The photodynamic activities of these compounds have been examined against a range of bacterial strains, including the Gram-positive methicillin-sensitive Staphylococcus aureus ATCC 25923 and methicillin-resistant Staphylococcus aureus ATCC BAA-43, and the Gram-negative Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 27853. Both photosensitizers are highly cytotoxic, particularly for the two Gram-positive strains, for which as low as 5 nM of dye is required to induce a 4-log reduction of their viability. The tri-N-methylated derivative has also been shown to be able to effectively inhibit the growth of a series of clinical strains of Staphylococcus aureus and Escherichia coli, and biofilms of methicillin-resistant Staphylococcus aureus ATCC 67928 and ATCC 68507, and Staphylococcus epidermidis ATCC 35984. In addition, the photodynamic inactivation of a range of viruses using these two compounds has also been investigated. Both compounds are highly photocytotoxic against the enveloped viruses influenza A virus (H1N1) and herpes simplex virus type 1 (HSV1), but exhibit no significant cytotoxicity toward the non-enveloped viruses adenovirus type 3 (Ad3) and coxsackievirus (Cox B1).

Photophysics of Soret-excited free base tetraphenylporphyrin and its zinc analog in solution

Photophysical properties of free base tetraphenylporphyrin and its zinc analog are investigated in detail in solvents of varying polarity by using steady state and time-resolved techniques. Both the porphyrins are excited at the Soret band to have better signal-to-noise ratio. Also, the fluorescence emission measurements are carried out by using dilute solutions (~10(-7)mol/L) of the fluorophores in order to minimize the self-quenching effect. It is observed that the steady state absorption and emission characteristics of the porphyrin molecules are mainly affected by polarizability (via refractive index) rather than polarity (via dielectric constant) of the moderate to highly polar solvents. As the molecules are highly symmetric in the ground state, the associated dipole moments are found to be very low from quantum chemical calculations performed by density functional theory method by using Gaussian 03 package. The dipole moments associated with the first excited singlet state of the porphyrins are computed by applying solvatochromic Stokes' shift method. To the best of our knowledge, this is the first attempt to calculate the excited state dipole moments of the porphyrins used in the present investigations. Also, fluorescence quantum yield, fluorescence lifetime of the first excited singlet state, radiative and non-radiative rate constants of the porphyrins are reported in solvents of varying polarity.

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.

Photodynamic therapy against achromic M6 melanocytes: phototoxicity of lipophilic axially substituted aluminum phthalocyanines and hexadecahalogenated zinc phthalocyanines

Lipophilic and axially substituted tri-n-hexylsiloxy aluminum phthalocyanine and cholesteryloxy diphenylsiloxy aluminum phthalocyanine were synthesized and assayed in PDT against M6 melanocytes. In the conditions used (λ > 480 nm , 10 mW cm-2, egg-yolk lecithin or cremophor EL formulation) they both exhibited a higher photodynamic effect than chloroaluminum phthalocyanine. They displayed 2% to 3.5% cell viability at 10-5M dose for 20 min irradiation. Hexadecafluoro zinc phthalocyanine was synthesized to increase the lipophilicity of zinc phthalocyanine, hexadecachloro zinc phthalocyanine was also included because it would theoretically enhance the phototoxicity. In all the delivery systems used, their photodynamic effect against M6 melanocytes was lower in comparison with zinc phthalocyanine and axially substituted aluminum phthalocyanines. A 2 h irradiation treatment with 3 × 10-6 M hexadecafluoro zinc phthalocyanine and 10-5 M hexadecachloro zinc phthalocyanine led to 60% and 15% cell viability respectively. In all cases, the cell killing effect was light-and dose-dependent and was higher in cremophor EL micelles than in the egg-yolk lecithin formulation.

Phthalocyanines as Photosensitizers in the Photodynamic Therapy of Cancer

The application of phthalocyanine derivatives in medicine as photosensitizers for photodynamic therapy of cancer diseases is reviewed. The emphasis is on the work of Russian authors, which is less covered in the scientific literature.

Differential sensitivities of pathogens in red cell concentrates to Tri-P(4)-photoinactivation

BACKGROUND AND OBJECTIVES

Photodynamic treatment (PDT) with the cationic porphyrin, mono-phenyl-tri-(N-methyl-4-pyridyl)-porphyrin chloride [Tri-P(4)], has previously been shown to be effective at inactivating vesicle stomatitis virus (VSV) in red cell concentrates (RCC) with limited damage to red blood cells (RBC). The aim of this study was to determine the pathogen-inactivating capacity of PDT with Tri-P(4) for a broader range of pathogens and to establish the associated effect on in vitro RBC quality.

MATERIALS AND METHODS

A series of viruses and bacteria was spiked into 60% RCC. Pathogen inactivation was determined after PDT with 25 microm Tri-P(4) and red light up to 360 kJ/m2. Human immunodeficiency virus (HIV)-infected cells were evaluated for cell death induction, and RCC were analysed for the induction of haemolysis and ATP content.

RESULTS

For the lipid-enveloped viruses bovine viral diarrhoea virus, HIV and pseudorabies virus, and for the Gram positive bacterium, Staphylococcus aureus, and the Gram-negative bacteria, Pseudomonas aeruginosa and Yersinia enterolitica, inactivation of > or = 5 log10 was measured after 60 min of PDT with Tri-P(4). The required treatment time to achieve this level of inactivation was four times longer than required for VSV. For cell-associated HIV, only 1.7 log10 of inactivation was found, despite clear induction of cell death of HIV-infected cells. The non-enveloped virus, canine parvovirus, was completely resistant to the treatment. PDT of RCC with Tri-P(4) for 60 min, and subsequent storage in AS-3, resulted in 4% haemolysis after 35 days of storage. The ATP content of untreated and treated RBC declined with similar kinetics during storage.

CONCLUSION

PDT of RCC with Tri-P(4) for 60 min inactivates a wide range of pathogens, but not cell-associated HIV and a non-enveloped virus, and compromises RBC quality. This reduces the suitability of PDT with Tri-P(4) for red cell sterilization. Therefore, further improvements in the treatment procedures to potentiate pathogen inactivation and to preserve RBC integrity will be required to generate an effective treatment for sterilizing RCC.

Use of merocyanine 540 for photodynamic inactivation of Staphylococcus aureus planktonic and biofilm cells

Photodynamic inactivation of Staphylococcus aureus planktonic and biofilm cells by a phtotosensitizer, merocyanine 540 (MC 540), was investigated. For the planktonic experiments, MC 540 binding efficiency to bacterial cells was found to increase with both increasing MC 540 concentration and increasing incubation time, but the binding became saturated following 10 min of incubation. The antimicrobial activity was enhanced with an increasing light dose, but an increase in the light dose could not further improve the antimicrobial activity if the maximum excitation level attainable was less than the necessary minimum threshold level. Complete inactivation was achieved when the excitation level of MC 540 was somewhere above the threshold level. The relationship between antimicrobial activity and the excitation level of MC 540 revealed that the more MC 540 was excited, the more S. aureus cells were killed. For the biofilm experiments, the antimicrobial activity was enhanced with an increase in the light dose. No viable cells were detected when organisms were exposed to 15 mug of MC 540 per ml and a light dose of 600 J/cm2 or to 20 mug of MC 540 per ml and a light dose of 450 J/cm2. A quantitative analysis of MC 540 bound to biofilms was also performed, and the images from confocal laser scanning microscopy provided direct evidence that revealed the difference between the MC 540 remaining in the biofilms prior to irradiation and the MC 540 remaining in the biofilms after irradiation. The results of both the planktonic and biofilm experiments suggest that the antimicrobial activity of photodynamic inactivation of S. aureus is closely related to the excitation level of MC 540.

Synthesis and Cellular Studies of Nonaggregated Water-Soluble Phthalocyanines

Water-soluble phthalocyanines are promising photosensitizers for application in cancer therapy and in the photoinactivation of viruses. The water-soluble zinc(II) phthalocyanines 5 and 6 were synthesized by converting the corresponding ester derivative 4 into the sodium carboxylate and carboxylic acid species. Compound 5 can be solubilized in water as a monomeric species, as demonstrated by UV/vis and fluorescence spectroscopy. These compounds were characterized by analytical and spectroscopic methods and, in the case of 4, by X-ray crystallography. The water-soluble phthalocyanines were found to have low dark cytotoxicity toward V79 hamster fibroblasts and human HEp2 cells, to be phototoxic at low light and drug doses, to be taken up by cells in culture, and to localize intracellularly, mainly in the cell lysosomes. Conjugation of the anionic phthalocyanines with positively charged LipoGen liposomes resulted in effective delivery of these compounds into the nuclei of cells. It is concluded that these highly water-soluble phthalocyanines are promising sensitizers for the photodynamic therapy of tumors.

Photodynamic effects of Radachlorin on cervical cancer cells

PURPOSE

Photodynamic therapy (PDT) is a novel treatment modality, which produces local tissue necrosis with laser light following the prior administration of a photosensitizing agent. Radachlorin has recently been shown to be a promising PDT sensitizer. In order to elucidate the antitumor effects of PDT using Radachlorin on cervical cancer, growth inhibition studies on a HPV-associated tumor cell line, TC-1 cells in vitro and animals with an established TC-1 tumor in vivo were determined.

MATERIALS AND METHODS

TC-1 tumor cells were exposed to various concentrations of Radachlorin and PDT, with irradiation of 12.5 or 25 J/cm(2) at an irradiance of 20 mW/cm(2) using a Won-PDT D662 laser at 662 nm in vitro. C57BL/6 mice with TC-1 tumor were injected with Radachlorin via different routes and treated with PDT in vivo. A growth suppression study was then used to evaluate the effects at various time points after PDT.

RESULTS

The results showed that irradiation of TC-1 tumor cells in the presence of Radachlorin induced significant cell growth inhibition. Animals with established TC-1 tumors exhibited significantly smaller tumor sizes over time when treated with Radachlorin and irradiation.

CONCLUSION

PDT after the application of Radachlorin appears to be effective against TC-1 tumors both in vitro and in vivo.

Novel processes for inactivation of leukocytes to prevent transfusion-associated graft-versus-host disease

Transfusion-associated graft-versus-host disease (TA-GVHD) is a serious complication of blood component transfusion therapy. Currently, cellular blood components for patients recognized at risk for TA-GVHD are irradiated prior to transfusion in order to prevent this complication. Considerable progress has been made in elucidating the pathophysiology of this highly morbid complication, but questions as to which patients are at risk and what is the most robust technology to prevent TA-GVHD remain. As new technologies for inactivating or modulating leukocyte function are introduced, the question of how to evaluate these technologies becomes relevant. Over the past two decades, a number of research groups have explored technology to inactivate infectious pathogens and leukocytes contaminating cellular blood components. Few clinicians have an in-depth understanding of the methods or the criteria for selection of how to approach new technologies for leukocyte inactivation with potential to replace current methods. This mini review focuses on the salient aspects of current and evolving technology for prevention of TA-GVHD.

Positively charged porphyrins: a new series of photosensitizers for sterilization of RBCs

BACKGROUND

Photodynamic treatment could be a way to inactivate pathogens in RBCs. The objective of this study was to characterize the virucidal activity and RBC-damaging activity of a series of cationic porphyrins. Using the most efficacious photosensitizer, various in-vitro human RBC quality variables and in-vivo RBC survival in Rhesus monkeys were evaluated.

STUDY DESIGN AND METHODS

RBCs, spiked with 5 log of extracellular VSV, were treated with porphyrins (25 micro mol/L) and red light (100 W/m2) and essayed for virucidal activity. In-vitro RBC quality variables were assessed during 5 weeks of storage in various ASs. In-vivo survival was investigated with autologous RBCs in Rhesus monkeys.

RESULTS

Tri-P(4) was by far the best sensitizer of a series tested, giving the least hemolysis under conditions that resulted in 5 log-kill of extracellular VSV. Under our experimental conditions, the percentage hemolysis in treated cells was 5.1 +/- 1.1 percent after 5 weeks of storage in SAG-M compared to 1.9 +/- 1.1 percent in the untreated control. Storage in AS-3 resulted hemolysis of 2.3 +/- 1.9 percent. With the exception of IgG binding and potassium leakage, RBC quality variables remained unchanged after photodynamic treatment. Addition of reduced glutathione (GSH) during treatment reduced IgG binding. The 24-hour recovery and T50 of treated RBCs in Rhesus monkeys were satisfactory.

CONCLUSION

Porphyrin Tri-P(4) may be a suitable photosensitizer for sterilization of RBCs. However, further exploration to optimize the method is necessary to reach clinically acceptable goals.

Laser-assisted optical rotational cell analyzer measurements reveal early changes in human RBC deformability induced by photodynamic treatment

BACKGROUND

The ability to deform is important for circulating RBCs in vivo, and earlier studies showed that this property can objectively be measured in vitro by the LORCA. In this study it was investigated whether photodynamic treatment of human RBCs (meant to inactivate contaminating pathogens) affects deformability.

STUDY DESIGN AND METHODS

WBC-reduced RBC suspensions (30% Hct) were treated with 1,9-dimethylmethylene blue (DMMB) and red light. Changes in deformability were analyzed by LORCA measurements, in which elongation of the cells is measured at increasing shear stress. The effect of DMMB concentration and light dose was determined as well as the interfering effect of two scavengers of reactive oxygen species, that is, dipyridamole and Trolox.

RESULTS

Photodynamic treatment with DMMB resulted in clear changes in RBC deformability. Deformability changes occurred before onset of hemolysis. Under relatively mild treatment conditions, especially deformability at low shear stress was decreased, whereas deformability changes at high shear stress only occurred under harsher treatment conditions. Inclusion of dipyridamole and/or Trolox primarily prevented deformability changes at high shear stress.

CONCLUSION

LORCA measurements can effectively be used to detect changes in deformability that are induced by photodynamic treatment of human RBCs. A change in deformability represents an early marker of RBC damage under these conditions.

Photosensitized inactivation of T7 phage as surrogate of non-enveloped DNA viruses: efficiency and mechanism of action

We investigated the efficiency and the mechanism of action of a tetraphenyl porphyrin derivative in its photoreaction with T7 phage as surrogate of non-enveloped DNA viruses. TPFP was able to sensitize the photoinactivation of T7 phage in spite of the lack of its binding to the nucleoprotein complex. The efficiency of TPFP photosensitization was limited by the aggregation and by the photobleaching of porphyrin molecules. Addition of sodium azide or 1,3-dimethyl-2-thiourea (DMTU) to the reaction mixture moderated T7 inactivation, however, neither of them inhibited T7 inactivation completely. This result suggests that both Type I and Type II reaction play a role in the virus inactivation. Optical melting studies revealed structural changes in the protein part but not in the DNA of the photochemically treated nucleoprotein complex. Polymerase chain reaction (PCR) also failed to demonstrate any DNA damage. Circular dichroism (CD) spectra of photosensitized nucleoprotein complex indicated changes in the secondary structure of both the DNA and proteins. We suggest that damages in the protein capsid and/or loosening of protein-DNA interaction can be responsible for the photodynamic inactivation of T7 phage. The alterations in DNA secondary structure might be the result of photochemical damage in phage capsid proteins.

Composition of the additive solution affects red blood cell integrity after photodynamic treatment

BACKGROUND AND OBJECTIVES

Photodynamic treatment is a promising technique for pathogen inactivation of red blood cell concentrates. For protocol optimization, the influence of the composition of the storage solution on the integrity of phototreated red cells was studied.

MATERIALS AND METHODS

Red blood cells were resuspended in the storage solutions SAG-M or AS-3 to a haematocrit (Hct) of 30%. After addition of the photosensitizer, 1,9-dimethylmethylene blue (DMMB) (25 microm), the suspensions were illuminated with red light, and potassium leakage and delayed haemolysis were determined. In some experiments, the cells were washed after illumination and resuspended in modified storage solutions.

RESULTS

Illumination of red cells in the presence of DMMB resulted in an immediate, light-dose-dependent increase in potassium leakage. The illumination conditions used induced no detectable haemolysis immediately after photodynamic treatment. Potassium leakage was higher when the illumination was performed in AS-3. In contrast, delayed haemolysis, measured after overnight storage, was considerably lower when cells were stored in AS-3. This protection was mainly a result of the presence of citrate in AS-3. In addition, other impermeant solutes protected against haemolysis.

CONCLUSIONS

The additive solution strongly influences the integrity of red cells after photodynamic treatment. Whereas the solution in which the cells are illuminated has a small effect on red cell integrity, the main influence of the additive solution is during post-treatment storage. Red cell integrity is best maintained when illumination is performed in SAG-M followed by storage in AS-3. The presence of non-permeant solutes, such as citrate, in the solution used for storage, prevents haemolysis of the phototreated, cation-permeable cells by counterbalancing the osmotic activity of haemoglobin.

Local treatment of viral disease using photodynamic therapy

Although reports of the photodynamic inactivation of viruses appeared in 1928, long before chemotherapeutic antiviral drugs, the first clinical trial in humans-the topical treatment of herpes genitalis-did not take place until the early 1970s. Trials were discontinued due to the transformation of healthy cells and concomitant incidence of Bowen's disease in some patients, probably due to the migration of infective sections of photodamaged viral nucleic acid. With the modern development of photodynamic therapy as a cancer treatment and the use of photosensitisers in the photodecontamination of blood products, a great deal of experience has been gained, both in the minimisation of side effects in humans and in the targeting and eradication of viruses. This suggests that the photodynamic approach to a range of virus-associated infections, lesions and cancer might now be revisited with greater success.

Prevention of poxvirus infection by tetrapyrroles

BACKGROUND

Prevention of poxvirus infection is a topic of great current interest. We report inhibition of vaccinia virus in cell culture by porphyrins and phthalocyanines. Most previous work on the inhibition of viruses with tetrapyrroles has involved photodynamic mechanisms. The current study, however, investigates light-independent inhibition activity.

METHODS

The Western Reserve (WR) and International Health Department-J (IHD-J) strains of vaccinia virus were used. Virucidal and antiviral activities as well as the cytotoxicity of test compounds were determined.

RESULTS

Examples of active compounds include zinc protoporphyrin, copper hematoporphyrin, meso(2,6-dihydroxyphenyl)porphyrin, the sulfonated tetra-1-naphthyl and tetra-1-anthracenylporphyrins, selected sulfonated derivatives of halogenated tetraphenyl porphyrins and the copper chelate of tetrasulfonated phthalocyanine. EC50 values for the most active compounds are as low as 0.05 microg/mL (40 nM). One of the most active compounds was the neutral meso(2,6-dihydroxyphenyl)porphyrin, indicating that the compounds do not have to be negatively charged to be active.

CONCLUSIONS

Porphyrins and phthalocyanines have been found to be potent inhibitors of infection by vaccinia virus in cell culture. These tetrapyrroles were found to be active against two different virus strains, and against both enveloped and non-enveloped forms of the virus, indicating that these compounds may be broadly effective in their ability to inhibit poxvirus infection.