A Novel Approach of Combining Methylene Blue Photodynamic Inactivation, Photobiomodulation and Oral Ingested Methylene Blue in COVID-19 Management: A Pilot Clinical Study with 12-Month Follow-Up

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 virus was first recognized in late 2019 and remains a significant threat. We therefore assessed the use of local methylene blue photodynamic viral inactivation (MB-PDI) in the oral and nasal cavities, in combination with the systemic anti-viral, anti-inflammatory and antioxidant actions of orally ingested methylene blue (MB) and photobiomodulation (PBM) for COVID-19 disease. The proposed protocol leverages the separate and combined effects of MB and 660nm red light emitted diode (LED) to comprehensively address the pathophysiological sequelae of COVID-19. A total of eight pilot subjects with COVID-19 disease were treated in the Bahamas over the period June 2021-August 2021, using a remote care program that was developed for this purpose. Although not a pre-requisite for inclusion, none of the subjects had received any COVID-19 vaccination prior to commencing the study. Clinical outcome assessment tools included serial cycle threshold measurements as a surrogate estimate of viral load; serial online questionnaires to document symptom response and adverse effects; and a one-year follow-up survey to assess long-term outcomes. All subjects received MB-PDI to target the main sites of viral entry in the nose and mouth. This was the central component of the treatment protocol with the addition of orally ingested MB and/or PBM based on clinical requirements. The mucosal surfaces were irradiated with 660 nm LED in a continuous emission mode at energy density of 49 J/cm2 for PDI and 4.9 J/cm2 for PBM. Although our pilot subjects had significant co-morbidities, extremely high viral loads and moderately severe symptoms during the Delta phase of the pandemic, the response to treatment was highly encouraging. Rapid reductions in viral loads were observed and negative PCR tests were documented within a median of 4 days. These laboratory findings occurred in parallel with significant clinical improvement, mostly within 12-24 h of commencing the treatment protocol. There were no significant adverse effects and none of the subjects who completed the protocol required in-patient hospitalization. The outcomes were similarly encouraging at one-year follow-up with virtual absence of "long COVID" symptoms or of COVID-19 re-infection. Our results indicate that the protocols may be a safe and promising approach to challenging COVID-19 disease. Moreover, due its broad spectrum of activity, this approach has the potential to address the prevailing and future COVID-19 variants and other infections transmitted via the upper respiratory tract. Extensive studies with a large cohort are warranted to validate our results.

Capturing Protein-Nucleic Acid Interactions by High-Intensity Laser-Induced Covalent Crosslinking

Interactions of DNA with structural proteins such as histones, regulatory proteins, and enzymes play a crucial role in major cellular processes such as transcription, replication and repair. The in vivo mapping and characterization of the binding sites of the involved biomolecules are of primary importance for a better understanding of genomic deployment that is implicated in tissue and developmental stage-specific gene expression regulation. The most powerful and commonly used approach to date is immunoprecipitation of chemically cross-linked chromatin (XChIP) coupled with sequencing analysis (ChIP-seq). While the resolution and the sensitivity of the high-throughput sequencing techniques have been constantly improved little progress has been achieved in the crosslinking step. Because of its low efficiency the use of the conventional UVC lamps remains very limited while the formaldehyde method was established as the "gold standard" crosslinking agent. Efficient biphotonic crosslinking of directly interacting nucleic acid-protein complexes by a single short UV laser pulse has been introduced as an innovative technique for overcoming limitations of conventionally used chemical and photochemical approaches. In this survey, the main available methods including the laser approach are critically reviewed for their ability to generate DNA-protein crosslinks in vitro model systems and cells.

Photodynamic disinfection of SARS-CoV-2 clinical samples using a methylene blue formulation

Abstract

The amplitude of the coronavirus disease 2019 (COVID-19) pandemic motivated global efforts to find therapeutics that avert severe forms of this illness. The urgency of the medical needs privileged repositioning of approved medicines. Methylene blue (MB) has been in clinical use for a century and proved especially useful as a photosensitizer for photodynamic disinfection (PDI). We describe the use of MB to photo-inactivate SARS-CoV-2 in samples collected from COVID-19 patients. One minute of treatment can reduce the percentage inhibition of amplification by 99.99% under conditions of low cytotoxicity. We employed a pseudotyped lentiviral vector (LVs) encoding the luciferase reporter gene and exhibiting the S protein of SARS-CoV-2 at its surface, to infect human ACE2-expressing HEK293T cells. Pre-treatment of LVs with MB-PDI prevented infection at low micromolar MB concentrations and 1 min of illumination. These results reveal the potential of MB-PDI to reduce viral loads in the nasal cavity and oropharynx in the early stages of COVID-19, which may be employed to curb the transmission and severity of the disease.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s43630-022-00202-6.

Methylene Blue has a potent antiviral activity against SARS-CoV-2 and H1N1 influenza virus in the absence of UV-activation in vitro

Methylene blue is an FDA (Food and Drug Administration) and EMA (European Medicines Agency) approved drug with an excellent safety profile. It displays broad-spectrum virucidal activity in the presence of UV light and has been shown to be effective in inactivating various viruses in blood products prior to transfusions. In addition, its use has been validated for methemoglobinemia and malaria treatment. In this study, we first evaluated the virucidal activity of methylene blue against influenza virus H1N1 upon different incubation times and in the presence or absence of light activation, and then against SARS-CoV-2. We further assessed the therapeutic activity of methylene blue by administering it to cells previously infected with SARS-CoV-2. Finally, we examined the effect of co-administration of the drug together with immune serum. Our findings reveal that methylene blue displays virucidal preventive or therapeutic activity against influenza virus H1N1 and SARS-CoV-2 at low micromolar concentrations and in the absence of UV-activation. We also confirm that MB antiviral activity is based on several mechanisms of action as the extent of genomic RNA degradation is higher in presence of light and after long exposure. Our work supports the interest of testing methylene blue in clinical studies to confirm a preventive and/or therapeutic efficacy against both influenza virus H1N1 and SARS-CoV-2 infections.

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.

Photosensitization Reactions of Biomolecules: Definition, Targets and Mechanisms

Photosensitization reactions have been demonstrated to be largely responsible for the deleterious biological effects of UV and visible radiation, as well as for the curative actions of photomedicine. A large number of endogenous and exogenous photosensitizers, biological targets and mechanisms have been reported in the past few decades. Evolving from the original definitions of the type I and type II photosensitized oxidations, we now provide physicochemical frameworks, classifications and key examples of these mechanisms in order to organize, interpret and understand the vast information available in the literature and the new reports, which are in vigorous growth. This review surveys in an extended manner all identified photosensitization mechanisms of the major biomolecule groups such as nucleic acids, proteins, lipids bridging the gap with the subsequent biological processes. Also described are the effects of photosensitization in cells in which UVA and UVB irradiation triggers enzyme activation with the subsequent delayed generation of superoxide anion radical and nitric oxide. Definitions of photosensitized reactions are identified in biomolecules with key insights into cells and tissues.

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.

Recent Advancement in SARS-CoV-2 Diagnosis, Treatment, and Vaccine Formulation: a New Paradigm of Nanotechnology in Strategic Combating of COVID-19 Pandemic

Purpose of Review

The coronavirus disease-2019 (COVID-19) is a global pandemic which has not been seen in recent history, leaving behind deep socioeconomic damages and huge human losses with the disturbance in the healthcare sector. Despite the tremendous international effort and the launch of various clinical trials for the containment of this pandemic, no effective therapy has been proven yet.

Recent Findings

This review has highlighted the different traditional therapeutic techniques, along with the potential contribution of nanomedicine against the severe acute respiratory syndrome corovirus-2 (SARS-CoV-2). Repositioning of the drugs, such as remdesivir and chloroquine, is a rapid process for the reach of safe therapeutics, and the related clinical trials have determined effects against COVID-19. Various protein-based SARS-CoV-2 vaccine candidates have successfully entered clinical phases, determining positive results. The self-assembled and metallic nanovaccines mostly based on the antigenic properties of spike (S) protein are also approachable, feasible, and promising techniques for lowering the viral burden.

Summary

There are number of NP-based diagnostic systems have been reported for coronaviruses (CoVs) and specifically for SARS-CoV-2. However, extensive studies are still necessary and required for the nanoparticle (NP)-based therapy.

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.

Risk of Cirrhosis and Hepatocellular Cancer in Patients With NAFLD and Normal Liver Enzymes

BACKGROUND AND AIMS

The long-term risk of disease for patients with nonalcoholic fatty liver disease (NAFLD) in the absence of elevated enzymes is unclear. We conducted a retrospective cohort study using the Corporate Data Warehouse of the Veterans Health Administration.

APPROACH AND RESULTS

We classified patients into three groups: patients with steatosis/normal alanine aminotransferase (ALT), steatosis/elevated ALT, and no steatosis/normal ALT. We examined incidence rates for cirrhosis and hepatocellular carcinoma (HCC) and conducted cause-specific hazard models to evaluate the risk of cirrhosis and HCC. We identified 3,522 patients with steatosis/normal ALT, 15,419 patients with steatosis/elevated ALT, and 9,267 patients with no steatosis/normal ALT. The mean age in each group was 58.9, 54.7 and 59.3 years, respectively; over 90% were men. Compared to patients with hepatic steatosis/normal ALT, those with steatosis/elevated ALT were younger and more likely to be obese (both P < 0.01). In patients with steatosis/normal ALT, the incidence rates of cirrhosis and HCC were 1.22 (95% confidence interval [CI]: 0.83-1.74) and 0.20 (95% CI: 0.06-0.46) per 1,000 person-years, respectively; this was lower than in patients with steatosis/elevated ALT (cirrhosis: 3.85; 95% CI: 3.50-4.23, and HCC: 0.37; 95% CI: 0.26-0.49). Patients with steatosis/elevated ALT had a higher risk of developing cirrhosis (adjusted hazard ratio: 3.37; 95% CI:  2.34-4.86; P < 0.01) than patients with steatosis/normal ALT; they also had a higher risk of HCC, although it did not reach statistical significance (hazard ratio: 2.07; 95% CI: 0.82-5.28; P = 0.13). The risk of cirrhosis and HCC in patients with steatosis/normal ALT and those without steatosis was not significantly different.

CONCLUSIONS

Patients with hepatic steatosis with persistently normal ALT are at lower risk for cirrhosis compared to those with steatosis and elevated ALT and not different from the risk in a clinical cohort without hepatic steatosis.

Can nanotechnology help in the fight against COVID-19?

INTRODUCTION

The current COVID-19 pandemic caused by the SARS-CoV-2 virus demands the development of strategies not only to detect or inactivate the virus, but to treat it (therapeutically and prophylactically). COVID-19 is not only a critical threat for the population with risk factors, but also generates a dramatic economic impact in terms of morbidity and the overall interruption of economic activities.

AREAS COVERED

Advanced materials are the basis of several technologies that could diminish the impact of COVID-19: biosensors might allow early virus detection, nanosized vaccines are powerful agents that could prevent viral infections, and nanosystems with antiviral activity could bind the virus for inactivation or destruction upon application of an external stimulus. Herein all these methods are discussed under the light of cutting-edge technologies and the previously reported prototypes targeting enveloped viruses similar to SARS-CoV-2. This analysis was derived from an extensive scientific literature search (including pubmed) performed on April 2020.

EXPERT OPINION

Perspectives on how biosensors, vaccines, and antiviral nanosystems can be implemented to fight COVID-19 are envisioned; identifying the approaches that can be implemented in the short term and those that deserve long term research to cope with respiratory viruses-related pandemics in the future.

Functional inactivation of lymphocytes by methylene blue with visible light

Upon visible light excitation, MB can cause damage to pathogen nucleic acids, thereby inhibiting lymphocyte proliferation and cytokine secretion.

SDS-PAGE and IR spectroscopy to evaluate modifications in the viral protein profile induced by a cationic porphyrinic photosensitizer

Reactive oxygen species can be responsible for microbial photodynamic inactivation due to its toxic effects, which include severe damage to proteins, lipids and nucleic acids. In this study, the photo-oxidative modifications of the proteins of a non-enveloped T4-like bacteriophage, induced by the cationic porphyrin 5,10,15-tris(1-methylpyridinium-4-yl)-20-(pentafluorophenyl)porphyrin tri-iodide were evaluated. Two methods were used: sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and infrared spectroscopy. SDS-PAGE analysis showed that the phage protein profile was considerably altered after photodynamic treatment. Seven protein bands putatively corresponding to capsid and tail tube proteins were attenuated and two other were enhanced. Infrared spectroscopy confirmed the time-dependent alteration on the phage protein profile detected by SDS-PAGE, indicative of a response to oxidative damage. Infrared analysis showed to be a promising and rapid screening approach for the analysis of the modifications induced on viral proteins by photosensitization. In fact, one single infrared spectrum can highlight the changes induced to all viral molecular structures, overcoming the delays and complex protocols of the conventional methods, in a much simple and cost effective way.

Subtle differences in virus composition affect disinfection kinetics and mechanisms

Viral disinfection kinetics have been studied in depth, but the molecular-level inactivation mechanisms are not understood. Consequently, it is difficult to predict the disinfection behavior of nonculturable viruses, even when related, culturable viruses are available. The objective of this work was to determine how small differences in the composition of the viral genome and proteins impact disinfection. To this end, we investigated the inactivation of three related bacteriophages (MS2, fr, and GA) by UV254, singlet oxygen ((1)O2), free chlorine (FC), and chlorine dioxide (ClO2). Genome damage was quantified by PCR, and protein damage was assessed by quantitative matrix-assisted laser desorption ionization (MALDI) mass spectrometry. ClO2 caused great variability in the inactivation kinetics between viruses and was the only treatment that did not induce genome damage. The inactivation kinetics were similar for all viruses when treated with disinfectants possessing a genome-damaging component (FC, (1)O2, and UV254). On the protein level, UV254 subtly damaged MS2 and fr capsid proteins, whereas GA's capsid remained intact. (1)O2 oxidized a methionine residue in MS2 but did not affect the other two viruses. In contrast, FC and ClO2 rapidly degraded the capsid proteins of all three viruses. Protein composition alone could not explain the observed degradation trends; instead, molecular dynamics simulations indicated that degradation is dictated by the solvent-accessible surface area of individual amino acids. Finally, despite the similarities of the three viruses investigated, their mode of inactivation by a single disinfectant varied. This explains why closely related viruses can exhibit drastically different inactivation kinetics.

Susceptibility of non-enveloped DNA- and RNA-type viruses to photodynamic inactivation

The comparative susceptibility of DNA- and RNA-type viruses to photodynamic inactivation has not yet been clearly addressed. In this study the effect of the tricationic porphyrin Tri-Py(+)-Me-PF on the inactivation of four DNA and three RNA non-enveloped phages was compared. The results obtained show that the photodynamic efficiency varied with the phage type, the RNA-type phages being much more easily photoinactivated than the DNA-type ones.

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.

Serendipitous findings while researching oxygen free radicals

This review is based on the honor of receiving the Discovery Award from the Society of Free Radical Biology and Medicine. The review is reflective and presents our thinking that led to experiments that yielded novel observations. Critical questioning of our understanding of oxygen free radicals in biomedical problems led us to use and develop more direct and extremely sensitive methods. This included nitrone free radical spin trapping and HPLC-electrochemical detection. This technology led to the pioneering use of salicylate to trap hydroxyl free radicals and show increased flux in ischemia/reperfused brain regions and also to first sensitively detect 8-hydroxyl-2-deoxyguanosine in oxidatively damaged DNA and help assess its role in cancer development. We demonstrated that methylene blue (MB) photoinduces formation of 8-hydroxyguanine in DNA and RNA and discovered that MB sensitively photoinactivates RNA viruses, including HIV and the West Nile virus. Studies in experimental stroke led us serendipitously to discover that alpha-phenyl-tert-butylnitrone (PBN) was neuroprotective if given after the stroke. This led to extensive commercial development of NXY-059, a PBN derivative, for the treatment of stroke. More recently we discovered that PBN nitrones have potent anti-cancer activity and are active in preventing hearing loss caused by acute acoustical trauma.

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.

Methylene blue photoinactivation of RNA viruses

We present a review of the current status of the use of methylene blue (MB) photoinactivation of viruses starting with the first early observations up to its current use to inactivate HIV-1 in blood products. Basic mechanism of action studies conducted with model bacteriophages indicate that MB-photomediated viral RNA-protein crosslinkage is a primary lesion and that oxygen, specifically singlet oxygen, is very important also. Basic studies on the mechanism of action with HIV are lacking; however, we do show new data illustrating that viral reverse transcriptase inactivation per se cannot account for MB-mediated photoinactivation. We also show data illustrating that MB photomediates the inactivation of West Nile Virus, a flavivirus, which poses a significant new threat to the continental US. MB photoinactivation of viruses show significant promise because the technology not only offers significant potency but the history of safe MB use in human therapy makes it attractive also.

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.

Photocytotoxicity of lipofuscin in human retinal pigment epithelial cells

Lipofuscin accumulates with age in a variety of highly metabolically active cells, including the retinal pigment epithelium (RPE) of the eye, where its photoreactivity has the potential for cellular damage. The aim of this study was to assess the phototoxic potential of lipofuscin in the retina. RPE cell cultures were fed isolated lipofuscin granules and maintained in basal medium for 7 d. Control cells lacking granules were cultured in an identical manner. Cultures were either maintained in the dark or exposed to visible light (2.8 mWcm2) at 37 degrees C for up to 48 h. Cells were subsequently assessed for alterations in cell morphology, cell viability, lysosomal stability, lipid peroxidation, and protein oxidation. Exposure of lipofuscin-fed cells to short wavelength visible light (390-550 nm) caused lipid peroxidation (increased levels of malondialdehyde and 4-hydroxy-nonenal), protein oxidation (protein carbonyl formation), loss of lysosomal integrity, cytoplasmic vacuolation, and membrane blebbing culminating in cell death. This effect was wavelength-dependent because light exposure at 550 to 800 nm had no adverse effect on lipofuscin-loaded cells. These results confirm the photoxicity of lipofuscin in a cellular system and implicate it in cell dysfunction such as occurs in ageing and retinal diseases.

Photoinduced inactivation of T7 phage sensitized by symmetrically and asymmetrically substituted tetraphenyl porphyrin: comparison of efficiency and mechanism of action

We investigated the efficiency and the mechanism of action of two--one symmetrically and one asymmetrically substituted--glycoconjugated tetraphenyl porphyrins in their photoreaction with T7 phage as a model of nucleoprotein (NP) complexes. A correlation was found between the dark inactivation of T7 and the binding of porphyrins determined by fluorescence spectroscopy. Both types of porphyrin sensitized the photoinactivation of T7, but the slopes of inactivation kinetics were markedly different. There was no correlation between the dark binding and the photosensitizing efficacy of the two derivatives. Inactivation was moderated by 1,3-diphenylisobenzofuran and 1,3-dimethyl-2-thiourea; however, neither of them inhibited T7 inactivation completely. This result suggests that both Type-I and Type-II reactions 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 NP complex. Polymerase chain reaction analysis of a 555 bp segment of gene 1 and a 3826 bp segment of genes 3 and 4 failed to demonstrate any DNA damage.

Methylene blue derivatives--suitable photoantimicrobials for blood product disinfection?

Photodynamic antimicrobial agents based on the well-established phenothiazinium biological stain methylene blue offer a simple method for the inactivation or destruction of pathogens contained in donated blood and blood products. The technique is currently concentrated on viruses and the disinfective procedure can be carried out in blood bags using basic low-power light sources. Pathogens of the bacterial, yeast and protozoal classes are also susceptible to phenothiaziniums. The photoantimicrobial mode of action is usually via oxidative damage to cellular components, either due to redox reactions between the agent and a biomolecular target or by the action of reactive oxygen species generated in situ by photodynamic action. The targeting of various microbial species is discussed in relation to the physicochemical make-up of the photosensitizers, and future directions are suggested.

Simultaneous photoconjugation of methylene blue and cis-Rh(phen)2Cl2+ to DNA via a synergistic effect

Irradiation of the red-light absorbing dye, methylene blue (MB), in the presence of the metal complex, cis-Rh(phen)2Cl2+ (BISPHEN), leads to irreversible photobinding of both reagents to DNA. Evidence from absorption and emission spectroscopy indicates that the dye is strongly complexed to the DNA at the concentrations used in the experiments and that this complex is unaffected by the presence of BISPHEN. The level of covalent binding is proportional to the absorbed light dose, with the quantum efficiency for covalent binding of BISPHEN to the DNA with 633 nm light equal to 3.5 x 10(-4). Electrospray ionization mass spectrum of a mixture of DNA fragments created by enzymatic degradation of DNA isolated following irradiation indicates that purine adducts are formed with both BISPHEN and the dye. In addition, UV-Vis and high-performance liquid chromatography analyses of the irradiated MB/BISPHEN/DNA mixture and isolated adducts show extensive conversion of the dye and metal complex to the corresponding N-demethylated and aquated derivatives, respectively. Triplet quenchers for MB, for example oxygen and benzoquinone, inhibit both the photoconjugation and the photochemistry of BISPHEN. A mechanism for the synergistic interaction is proposed that involves photoconjugation of both partners to the DNA following oxidation and reduction via electron transfer between 1MB*/DNA and 3MB*/BISPHEN.