Photodynamic therapy has been applied endoscopically to treat early esophageal cancer. However, the long-term survival outcome of this treatment option is unknown in literature. Patients and Method: The patients of early esophageal cancer (clinical stage I) treated with photophrin based photodynamic therapy were analyzed for their long-term survival outcome and compared to those patients undergoing esophagectomy by a single surgeon for stage I disease. Results: There were 15 and 16 patients undergoing PDT and esophagectomy enrolled in the current study respectively. Complete response was achieved in 10 (66.7%) patients after PDT. After adjuvant chemoradiation (CCRT) complete response was achieved in 13 patients (86%). There is no mortality after PDT. Severe complication was detected in 3 patients including trachea-esophageal fistulae, esophageal stenosis and skin photosensitivity respectively. With a median follow-up duration of 110.2 months (+9.6 months) for the patients after PDT, there were 4 and 3 recurrence in the primary tumor site and regional lymph node respectively with 73.3% of successful local control rate of the primary tumor. There were 7 (46.7%) patients died during clinical follow-up of this cohort with 5 (33.3%) from disease progression of esophageal cancer and two from other diseases respectively. The five-year survival rate after PDT is 64.3%, whereas 70.9% of the patients after esophagectomy without significant difference of these two group of patients (P=0.72). Conclusion: Our preliminary results suggested that PDT might provide an equivalent long-term oncological outcome as compared to that done by esophagectomy for early esophageal cancer. A prospective randomized clinical trial comparing the results with esophagectomy and other endoscopic abrasive therapies is warrant in the future.

A single-site, randomized clinical trial was designed to determine the efficacy of regular home use of Lumoral® dual-light antibacterial aPDT in periodontitis patients. For the study, 200 patients are randomized to receive non-surgical periodontal treatment (NSPT), including standardized hygiene instructions and electric toothbrush, and scaling and root planing, or NSPT with adjunctive Lumoral® treatment. A complete clinical intraoral examination is conducted in the beginning, at three months, and at six months. This report presents the three-month results of the first 59 consecutive randomized subjects. At three months, bleeding on probing (BoP) was lower in the NSPT+Lumoral®-group than in the NSPT group (p=0.045), and more patients in the NSPT+Lumoral®-group had their BoP below 10% (52% vs. 29%, respectively, p=0.008). Patients in the NSPT+Lumoral®-group improved their oral hygiene by visible-plaque-index (p=0.0002), while the NSPT group showed no statistical improvement as compared to baseline. Both groups significantly reduced the number of deep periodontal pockets, but more patients with a reduction in their deep pocket number were found in the NSPT+Lumoral® group (92% vs. 63%, p=0.01). Patients whose number of deep pockets was reduced by 50% or more were also more frequent in the NSPT+Lumoral®-group (70% vs. 33%, p=0.01). Patients with initially less than ten deep pockets had fewer deep pockets at three-month follow-up in the Lumoral® group (p=0.02). In conclusion, adjunctive use of Lumoral® in NSPT results in improved treatment outcomes at three months post-therapy.

Photodynamic therapy (PDT) with a suitable photosensitizer molecule is a promising anticancer treatment. We evaluated two chlorin molecules as potential photosensitizers, methyl pyropheophorbide a (MPPa) and N-methoxyl purpurinimide (NMPi), against A549 human lung adenocarcinoma cells in vitro as well as in A549 tumor-bearing mice in vivo. Cell viability, microscopy, and FACS analyses were performed for the in vitro studies. MPPa and NMPi showed high phototoxicity in vitro, which was dependent on the concentration of the photosensitizers as well as the light irradiation time. In the animal study, tumor volume change, tumor surface alterations, and H&E and TUNEL staining analyses were performed and compared between small (tumor volume of <50 mm³) and large (tumor volume of >50 mm³) size of initial tumors. MPPa and NMPi showed high anticancer efficacy against small-size tumors, indicating that early treatment with PDT is effective. Especially, repeated two times PDT with NMPi allowed almost complete eradication against small-size tumors. However, MPPa and NMPi were not effective against large-size tumors. In conclusion, the two chlorin derivatives, MPPa and NMPi, show good anticancer efficacy as promising photosensitizers for PDT in vitro and in vivo. Moreover, their activity in vivo was significantly dependent on the initial tumor size in mice, which confirms the importance of early cancer treatment.

Photodynamic therapy (PDT) of cancer is dependent on three primary components: photosensitizer (PS), light, and oxygen. Because these components are interdependent and vary during the dynamic process of PDT, assessing PDT efficacy may not be trivial. Therefore, it has become necessary to develop pre-treatment planning, on-line monitoring and dosimetry strategies during PDT, which become more critical for two or more chromophore systems, e.g. PS-CD conjugates developed in our laboratory for fluorescence-imaging and PDT of cancer. In this study, we observed a significant impact of variable light dosimetry; (i) high light fluence and fluence rate (light dose: 135 J/cm², fluence rate: 75 mW/cm²) and (ii) low light fluence and fluence rate (128 J/cm² and 14 mW/cm² and 128 J/cm² and 7 mW/cm²) in photobleaching of the individual chromophores and their long-term tumor response. The fluorescence at the near-infrared (NIR) region of the PS-NIR fluorophore conjugate was assessed intermittently via fluorescence imaging. The loss of fluorescence, photobleaching, caused by singlet oxygen from the PS was mapped continuously during PDT. The tumor responses (BALB/c mice bearing Colon26 tumors) were assessed after PDT by measuring tumor sizes daily. Our results showed distinctive photobleaching kinetics rates between the PS and CD. Interestingly, compared to higher light fluence, the tumors exposed at low light fluence showed reduced photobleaching and enhanced long-term PDT efficacy. The presence of NIR fluorophore in PS-CD conjugates provides an opportunity of fluorescence imaging and monitoring the photobleaching rate of the CD moiety for large and deeply seated tumors and assessing PDT tumor response in real-time.

Background: The extended-spectrum beta-lactamase (ESBL) Klebsiella pneumoniae is one of the leading causes of health-associated infections (HAI), whose antibiotic treatments have been severely reduced. Besides, HAI bacteria may harbor pathogenic factors such as siderophores, enzymes, or capsules, which increase the virulence of these strains. Thus, new therapies such as antimicrobial photodynamic inactivation (aPDI) are needed. Method: A collection of 118 clinical isolates of K. pneumoniae were characterized susceptibility and virulence through the determination of the minimum inhibitory concentration (MIC) of Amk, Cfx, Cfz, Imp, Mer, and Pip-taz, and by PCR, the frequency of the virulence genes, K2, magA, rmpA, entB, ybtS, and allS. Susceptibility to innate immunity, such as human serum, macrophages, and polymorphonuclear cells, was tested. All the strains were tested for sensitivity to the photosensitizer PSIR-3 (4µg/mL) in a 17µW/cm2 for 30 min aPDI. Results: A significantly higher frequency of virulence genes in ESBL than non-ESBL bacteria were observed. The isolates of the genotype K2+, ybtS+, and allS+ display enhanced virulence since they showed higher resistance to human serum as well as to phagocytosis. All strains are susceptible to the aPDI with PSIR-3 decreasing viability in 3log10. The combined treatment with Cfx improved the aPDI to 6log10 for the ESBL strains. The combined treatment is synergistic as it showed an FIC index value of 0.15. Conclusions: The aPDT effectively inhibits clinical isolates of K. pneumoniae, including the more risky strains of ESBL-producing bacteria and the K2+, ybtS+, and allS+ genotype. The aPDI with PSIR-3 is synergistic with Cfx.

The rapid rise in research and development following the discovery of photodynamic therapy to establish novel photosensitizers and overcome the limitations of the technology soon after its clinical translation has given rise to a few significant milestones. These include several novel generations of photosensitizers, the widening of the scope of applications, leveraging of the offerings of nanotechnology for greater efficacy, selectivity for the disease over host tissue and cells, the advent of combination therapies with other similarly minimally invasive therapeutic technologies, the use of stimulus-responsive delivery and disease targeting, and greater penetration depth of the activation energy. Brought together, all these milestones have contributed to significant enhancement of what is still arguably a novel technology. Yet the major applications of photodynamic therapy still remain firmly located in neoplasms, from where most of the new innovations appear to launch to other areas, such as microbial, fungal, viral, acne, wet age-related macular degeneration, atherosclerosis, psoriasis, environmental sanitization, pest control, and dermatology. The core value proposition of combinations of photodynamic therapy is that they enhance the leading alternative and are proposed to overcome challenges of the leading clinical anticancer and antibacterial methods, mainly due to its inherent barriers against the emergence of resistance and its rapid development of targeted and high precision therapy. Combinations with chemotherapy and radiotherapy and demonstrated applications in mop-up surgery adventitiously promise to repurpose these top three clinical tools. This review will navigate the vast and increasing innovations that have been created so as to obviate novel areas of further innovation.

BODIPY dyes have recently raised attention as potential photosensitizers. In this work, commercial and novel photosensitizers (PSs) based on BODIPY chromophores (haloBODIPYs and orthogonal dimers strategically designed with intense bands in the blue, green or red region of the Visible spectra and high singlet oxygen production) were covalently linked to mesoporous silica nanoparticles (MSNs) further functionalized with PEG and folic acid (FA). MSNs of approximately 50 nm in size with different functional groups were synthesized to allow multiple alternatives of PS-PEG-FA decoration of their external surface. Different combinations varying the type of PS (commercial Rose Bengal, Thionine and Chlorine e6 or custom-made BODIPY-based), the linkage design and the length of PEG are detailed. All the nanosystems were physicochemically characterized (morphology, diameter, size distribution and PS loaded amount) and photophysically studied (absorption capacity, fluorescence efficiency, and singlet oxygen production) in suspension. For the most promising PS-PEG-FA silica nanoplatforms, the biocompatibility in dark conditions and the phototoxicity under suitable irradiation wavelengths (blue, green, or red) at regulated light doses (10-15 J/cm2) were compared with PSs free in solution in HeLa cells in vitro.

Cervical cancer is a significant global health concern, with human papillomavirus (HPV) infection being a crucial risk factor. Photodynamic therapy (PDT) is an attractive, minimally invasive treatment for HPV-related cervical lesions, which uses photosensitizers and light to selectively de-stroy abnormal cells. We aim to provide an overview of the various sorts of dyes that are utilized in PDT for decreasing the incidence and mortality of cervical cancer. Besides, the article discusses ongoing clinical trials for PDT in low-grade squamous intraepithelial neoplasia (LSIL) and high-grade squamous intraepithelial lesions (HSIL), as well as preclinical approaches for PDT in cervical cancer using various dyes. Moreover, it highlights potential dyes for PDT, examine them in in-silico condition, their pros and cons and also the solutions for enhancing their anticancer com-patibility. We also display that PDT is a promising therapeutic strategy for the diagnosis and treatment of HPV-associated cervical lesions. Moreover, it shows that using different classes of dyes improves the anticancer effects of PDT. Finally, among all dyes which are used in PDT, Fullerene demonstrated high tendency to over expressed receptors in cervical cancer cells and seems to be a proper candidate for be used in PDT more than before, but further research is necessary to assess its long-term efficacy and safety.

Millions of people use public transportation daily worldwide and frequently touch surfaces, thereby producing a reservoir of microorganisms on surfaces increasing the risk of transmission. Constant occupation makes sufficient cleaning difficult to achieve. Thus, an autonomous, perma-nent antimicrobial coating (AMC) could keep down the microbial burden on such surfaces. A photodynamic AMC was applied to frequently touched surfaces in buses. The microbial burden (colony forming units, cfu) was determined weekly and compared to equivalent surfaces in buses without AMC (references). The microbial burden ranged from 0 – 209 cfu/cm² on references and from 0 – 54 cfu/cm² on AMC. The means were 13.4 ± 29.6 cfu/cm² on references and 4.5 ± 8.4 cfu/cm² on AMC (p<0.001). The difference of microbial burden on AMC and references was al-most constant throughout the study. Considering a hygiene benchmark of 5 cfu/cm², the data yield an absolute risk reduction of 22.6 % and a relative risk reduction of 50.7 %. In conclusion, photo-dynamic AMC kept down the microbial burden, reducing the risk of transmission of microor-ganisms. AMC permanently and autonomously contributes to hygienic conditions on surfaces in public transportation. Photodynamic AMC therefore are suitable for reducing the microbial load and closing hygiene gaps in public transportation.

Metallic nanoparticles (NPs), among polymeric NPs, liposomes, micelles, quantum dots, dendrimers, or fullerenes, are becoming more and more important due to their potential use in the novel medical therapies. Titanium dioxide (titanium(IV) oxide, titania, TiO2) is an inorganic compound that owes its recent rise in scientific interest to photoactivity. After the illumination in aqueous media with UV light, TiO2 produces an array of reactive oxygen species (ROS). The capability to produce ROS and thus induce cell death has found application in the photodynamic therapy (PDT) for the treatment of a wide range of maladies, from psoriasis to cancer. Titanium dioxide NPs were studied as photosensitizing agents in the treatment of malignant tumors as well as in photodynamic inactivation of antibiotic-resistant bacteria. Both TiO2 NPs themselves, as well as their composites with other molecules, can be successfully used as photosensitizers in PDT. Moreover, various organic compounds can be grafted on TiO2 NPs, leading to hybrid materials. These nanostructures can reveal increased light absorption allowing their further use in targeted therapy in medicine. In order to improve efficient anticancer therapy, many approaches utilizing titanium dioxide were tested. The most significant studies are discussed in this review.

Photodynamic inactivation (PDI) combines the nontoxic photosensitizer (PS) and visible light to generate reactive oxygen species (ROS), which can cause oxidative damages in (on) microbial organisms. Previously, we have shown that chitosan can augment the bactericidal efficacy mediated by PDI against bacteria and Candida. In this study, we showed that the antimicrobial action of chitosan to augment PDI relates to the enlargement of cell surface destruction. The microbial cell surfaces exhibit severe irregular shapes after PDI in the presence of chitosan. Furthermore, increase in the concentrations or incubation time of chitosan significantly reduce the amounts of photosensitizers TBO required, indicating that chitosan could be a synergistic agent with PDI against human pathogens. A prolonged lag phase was found in PDI surviving microbial cells, in which chitosan can act to synergistically eradicate the cells. Once the impaired cells rebuild their cellular functions from PDI-induced damage, the increased cytotoxic effect of chitosan disappeared. Together, our results suggest that chitosan with an augmented bactericidal activity after PDI is to inhibit the rehabilitation of PDI surviving cells, leading to microbial death.

A Pacific brittle star Ophiura sarsii has previously been shown to produce a chlorin (3S,4S)-14-Ethyl-9-(hydroxymethyl)-4,8,13,18-tetramethyl-20-oxo-3-phorbinepropanoic acid (ETPA) (1) with potent phototoxic activities making it applicable to photodynamic therapy. Using extensive LC-MS metabolite profiling, molecular network analysis and targeted isolation with de novo NMR structure elucidation, we here identify five additional chlorin compounds from O. sarsii and its deep-sea relative O. ooplax: 10S-Hydroxypheophorbide a (2), Pheophorbide a (3), Pyropheophorbide a (4), (3S,4S,21R)-14-Ethyl-9-(hydroxymethyl)-21-(methoxycarbonyl)-4,8,13,18-tetramethyl-20-oxo-3-phorbinepropanoic acid (5), and (3S,4S,21R)-14-Ethyl-21-hydroxy-9-(hydroxymethyl)-4,8,13,18-tetramethyl-20-oxo-3-phorbinepropanoic acid (6). Chlorins 5 and 6 have not been previously reported in natural sources. Interestingly, low amounts of chlorins 1-4 and 6 could also be identified in a distant species, the basket star Gorgonocephalus cf. eucnemis, demonstrating that chlorins are produced by a wide spectrum of marine invertebrates of the class Ophiuroidea. Following purification of these major Ophiura chlorin metabolites, we discovered the high singlet oxygen quantum yield upon their photoinduction and their strong phototoxicity against a panel of cancer cell lines. These studies identify an arsenal of brittle star chlorins as powerful natural photosensitizers with potential photodynamic therapy applications.

The increasing popularity of porphyrins and hydroporphyrins for application in a variety of biomedical (photodynamic therapy, fluorescence tagging and imaging, photoacoustic imaging) and technical (chemosensing, catalysis, light harvesting) applications is also associated with the growing number of methodologies that enable their solubilization in aqueous media. Natively, the vast majority of synthetic porphyrinic compounds are not water-soluble. Moreover, any water-solubility imposes several restrictions on the synthetic chemist on when to install solubilizing groups in the synthetic sequence, and how to isolate and purify these compounds. This review summarizes the chemical modifications to render synthetic porphyrins water-soluble, with a focus on the work since 2000. Where available, practical data such as solubility, indicators for the degree of aggregation, and special notes for the practicioner are listed. We hope that this review will guide synthetic chemists through the many strategies known to make porphyrins and hydroporphyrins water soluble.

Herpes simplex virus (HSV) infections can be treated with direct acting antivirals like acyclovir and foscarnet, but long-term use can lead to drug resistance, which motivates research into broadly-acting antivirals that can provide a greater genetic barrier to resistance. Photodynamic inactivation (PDI) employs a photosensitizer, light, and oxygen to create a local burst of reactive oxygen species that inactivate microorganisms. The botanical plant extract Orthoquin^TM is a powerful photosensitizer with antimicrobial properties. Here we report that Orthoquin also has antiviral properties. Photoactivated Orthoquin inhibited herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) infection of target cells in a dose-dependent manner, across a broad range of sub-cytotoxic concentrations. HSV inactivation required direct contact between Orthoquin and the inoculum, whereas pre-treatment of target cells had no effect. Orthoquin did not cause appreciable damage to viral capsids or pre-mature release of viral genomes as measured by qPCR for the HSV-1 genome. By contrast, immunoblotting for HSV-1 antigens in purified virion preparations suggested that higher doses of Orthoquin had a physical impact on certain HSV-1 proteins that altered protein mobility or antigen detection. Orthoquin PDI also inhibited the non-enveloped adenovirus (AdV) in a dose-dependent manner, whereas Orthoquin-mediated inhibition of the enveloped vesicular stomatitis virus (VSV) was light-independent. Together, these findings suggest that broad antiviral effects of Orthoquin-mediated PDI may stem from damage to viral attachment proteins.

The kinetics and optimal efficacy conditions of photoinitiated polymerization are theoretically presented. Analytic formulas are derived for the crosslink time, crosslink depth and efficacy function. The roles of photosensitizer (PS) concentration, diffusion depth and light intensity on the polymerization spatial and temporal profiles, for both uniform and non-uniform cases, are presented . For optimal efficacy, a strategy via controlled PS concentration is proposed, where re-supply of PS in high light intensity may achieve a combined-efficacy similar to low light intensity, but has a much faster procedure. A new criterion of efficacy based on the polymerization (crosslink) [strength] and [depth] is introduced.

Different therapeutic strategies have been investigated to target and eliminate HIV-1-infected cells by using armed antibodies specific to viral proteins, with varying degrees of success. Herein, we propose a new strategy by combining photodynamic therapy (PDT) with HIV Env-targeted immunotherapy, and refer to it as HIV photoimmunotherapy (PIT). A human anti-gp41 antibody (7B2) was conjugated to two photosensitizers with different charges through different linking strategies; “Click” conjugation by using an azide-bearing porphyrin attached via a disulfide bridge linker with a drug-to-antibody ratio (DAR) of exactly 4, and “Lysine” conjugation by using phthalocyanine IRDye 700DX dye with average DARs of 2.1, 3.0 and 4.4. These photo-immunoconjugates (PICs) were compared via biochemical and immunological characterizations regarding the dosimetry, solubility, and cell targeting. Photo-induced cytotoxicity of the PICs were compared using assays for apoptosis, reactive oxygen species (ROS), photo-cytotoxicity, and confocal microscopy. Targeted phototoxicity seems to be primarily dependent on the binding of PS-antibody to the HIV antigen on the cell membrane, whilst being independent of the PS type. This is the first report of the application of PIT for HIV immunotherapy by killing HIV Env-expressing cells.

Microbial diseases have been declared one of the main threats to humanity, which is why, in recent years, great interest has been generated in the development of nanocomposites with antimicrobial capacity. In the present work, two magnetic nanocomposites, based on Graphene Oxide (GO) and Multiwall Carbon Nanotubes (MWCNTs) were studied. The synthesis of these magnetic nanocomposites consisted of three phases: first, the synthesis of Iron Magnetic Nanoparticles (MNPs) was carried out in the presence of MWCNTs and GO using the Co-precipitation method. The second phase consisted of the adsorption of photosensitizer menthol-Zinc phthalocyanine (ZnMintPc) into MWCNTs and GO, and the third phase was the encapsulation in poly (N-vinylcaprolactam-co-poly(ethylene glycol diacrylate)) poly (VCL-co-PEGDA) polymer VCL/PEGDA a biocompatible hydrogel, in order to obtain the magnetic nanocomposites: VCL/PEGDA-MNPs-MWCNTs-ZnMintPc and VCL/PEGDA-MNPs-GO-ZnMintPc. In vitro studies were carried out using Escherichia coli and Staphylococcus aureus bacteria and the Candida albicans yeast based on the PTT/PDT effect. This research describes the optical, morphological, magnetic and photophysical characterizations of nanocomposites and their application as antimicrobial agents. It was evaluated the antimicrobial effect of magnetics nanocomposites based on the Photodynamic/Photothermal (PDT/PTT) effect; for this purpose, doses of 65 mW cm-2 at 630 nm of light were used. The VCL/PEGDA-MNPs-GO-ZnMintPc nanocomposite was able to eliminate colonies of E. coli and S. aureus, while VCL/PEGDA-MNPs-MWCNTs-ZnMintPc nanocomposite was able to eliminate the three types of microorganisms; consequently, the latter is considered a broad-spectrum of antimicrobial agent in PDT and PTT.

The CAALA (Complex Augmentation of ALA) regimen was developed with the goal of redressing some of the weaknesses of 5-aminolevulinic acid (5-ALA) use in glioblastoma treatment as it now stands. 5-ALA is approved for use prior to glioblastoma surgery to better demarcate tumor from brain tissue. 5-ALA is also used in intraoperative photodynamic treatment of glioblastoma by virtue of uptake of 5-ALA and its selective conversion to protoporphyrin IX in glioblastoma cells. Protoporphyrin IX becomes cytotoxic after exposure to 410 nm or 635 nm light. CAALA uses four currently marketed drugs - the antibiotic ciprofloxacin, the iron chelator deferiprone, the antimetabolite 5-FU, and the xanthine oxidase inhibitor febuxostat - that all have evidence of ability to both increase 5-ALA mediated intraoperative glioblastoma demarcation and photodynamic cytotoxicity of in situ glioblastoma cells. Data from testing the full CAALA on living minipigs xenotransplanted with human glioblastoma cells will determine safety and potential for benefit in advancing CAALA to a clinical trial.

Collagen has been accepted in drug delivery structures due to its biocompatible chemical, physicochemical and curative actions. The study aims to evaluate the effects of a bovine collagen hydrolysate (Clg) on the main photophysical and photodynamic properties of a new gallium (III) phthalocyanine (GaPc). The absorbance of GaPc and the conjugate GaPc-Clg showed a decrease of the intensive Q-band (681 nm) and a blue shift of the maximum (678 nm) with loss of UV-band (354 nm) for 40 mg/mL Clg. The fluorescence of GaPc was evaluated with strong emission peak at 694 nm (exc: 615 nm) which was lower for GaPc-Clg (691 nm). The quantum yield of 0.23 was obtained for GaPc which was reduced for GaPc-Clg (0.012). Photo- and dark cytotoxicity was studied by NRU-assay on pigmented melanoma cells (SH-4) and normal cell lines (BJ and HaCaT). The results suggested a slight reduction of cytotoxicity for the conjugate but almost double for the selectivity index (SI: 0.71 vs. 1.49 for HaCaT cells). The study showed that bovine collagen hydrolysate can lower the PDT activity of a powerful photosensitizer with phototherapeutic index: 819 to 360, but also minimized its dark toxicity as a positive effect in the photodynamic treatment.

The design of more efficient photosensitizers is a matter of great importance in the field of cancer treatment by means of photodynamic therapy. One of the main processes involved in the activation of apoptosis in cancer cells is the oxidative stress on DNA once a photosensitizer is excited by light. As a consequence, it is a matter of great relevance to investigate in detail the binding modes of the chromophore with DNA, and the nature of the electronically excited states that participate in the induction of DNA damage, for example, charge-transfer states. In this work, we investigate the electronic structure of the anthraquinone photosensitizer intercalated into a double-stranded poly(dG-dC) decamer model of DNA. First, the different geometric configurations are analyzed by means of classical molecular dynamics simulations. Then, the excited states for the most relevant poses of anthraquinone inside the binding pocket are computed by an electrostatic-embedding quantum mechanics/molecular mechanics approach, where anthraquinone and one of the nearby guanine residues are described quantum mechanically to take into account intermolecular charge-transfer states. The excited states are characterized as monomer, exciton, excimer and charge-transfer states based on the analysis of the transition density matrix, and each of these contributions to the total density of states and absorption spectrum is discussed in terms of the stacking interactions. These results are relevant as they represent the footing for future studies on the reactivity of anthraquinone derivatives with DNA and give insights on possible geometrical configurations that potentially favor the oxidative stress of DNA.

Within this work we review the metal coordination effect on the photophysics of metal dipyrrinato complexes. Dipyrrinato complexes are promising candidates in the search for alternative transition metal photosensitizers for application in photodynamic therapy (PDT). These complexes can be activated by irradiation with light of a specific wavelength, after which cytotoxic reactive oxygen species (ROS) are generated. The metal coordination allows for the use of the heavy atom effect, which can enhance the triplet generation necessary for generation of ROS. Additionally, the flexibility of these complexes for metal ions, substitutions and ligands allows the possibility to tune their photophysical properties. A general overview of the mechanism of photodynamic therapy and the properties of the triplet photosensitizers is given, followed by further details of dipyrrinato complexes described in the literature that show relevance as photosensitizers for PDT. In particular, the photophysical properties of Re(I), Ru(II), Ir(III), Ni(II), Cu(II), Pd(II), Pt(II), Zn(II), Ga(III), In(III), Al(III), Sn(II), and P dipyrrinato complexes are discussed. The potential for future development in the field of (dipyrrinato)metal complexes is addressed and several new research topics are suggested throughout this work. We propose that significant advances could be made for heteroleptic bis(dipyrrinato)zinc(II) and homoleptic bis(dipyrrinato)palladium(II) complexes and their application as photosensitizers for PDT.