Lutetium texaphyrin (PCI-0123): a near-infrared, water-soluble photosensitizer

Photoinduced Isomerization of [N2]2- in a Bimetallic Lutetium Complex

The first lanthanide dinitrogen photoswitch [(C5Me4H)2(THF)Lu]2(μ-η2:η2-N2), 1, is reported. 1 is a unique example of controlled isomerization between side-on and end-on coordination modes of [N2]2- in a bimetallic lutetium dinitrogen complex that results in photochromism. Near-infrared light (NIR) was used to promote this effect, as evidenced by single X-ray diffraction (XRD) connectivity and Raman data, generating the [N2]2- end-on bound isomer, [(C5Me4H)2(THF)Lu]2(μ-η1:η1-N2), 2. Although different ligands and coordinating solvents were studied to replicate and control the optical properties in 1/2, only the original configuration with C5Me4H ligands and THF as the coordinating solvent worked. Supported by the first-principles calculations, the electronic structures along with the mechanistic details of the side-on to end-on isomerization were unraveled. Preliminary reactivity studies show that 2 formed with NIR light reacts with anthracene, generating dihydroanthracene and anthracene dimers, indicating new redox reaction pathways.

Lutetium Texaphyrin-Celecoxib Conjugate as a Potential Immuno-Photodynamic Therapy Agent

Immuno-photodynamic therapy (IPDT) has emerged as a new modality for cancer treatment. Novel photosensitizers can help achieve the promise inherent in IPDT, namely, the complete eradication of a tumor without recurrence. We report here a small molecule photosensitizer conjugate, LuCXB. This IPDT agent integrates a celecoxib (cyclooxygenase-2 inhibitor) moiety with a near-infrared absorbing lutetium texaphyrin photocatalytic core. In aqueous environments, the two components of LuCXB are self-associated through inferred donor-acceptor interactions. A consequence of this intramolecular association is that upon photoirradiation with 730 nm light, LuCXB produces superoxide radicals (O2-•) via a type I photodynamic pathway; this provides a first line of defense against the tumor while promoting IPDT. For in vivo therapeutic applications, we prepared a CD133-targeting, aptamer-functionalized exosome-based nanophotosensitizer (Ex-apt@LuCXB) designed to target cancer stem cells. Ex-apt@LuCXB was found to display good photosensitivity, acceptable biocompatibility, and robust tumor targetability. Under conditions of photoirradiation, Ex-apt@LuCXB acts to amplify IPDT while exerting a significant antitumor effect in both liver and breast cancer mouse models. The observed therapeutic effects are attributed to a synergistic mechanism that combines antiangiogenesis and photoinduced cancer immunotherapy.

Lutetium texaphyrin: A photocatalyst that triggers pyroptosis via biomolecular photoredox catalysis

Photon-controlled pyroptosis activation (PhotoPyro) is a promising technique for cancer immunotherapy due to its noninvasive nature, precise control, and ease of operation. Here, we report that biomolecular photoredox catalysis in cells might be an important mechanism underlying PhotoPyro. Our findings reveal that the photocatalyst lutetium texaphyrin (MLu) facilitates rapid and direct photoredox oxidation of nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate, and various amino acids, thereby triggering pyroptosis through the caspase 3/GSDME pathway. This mechanism is distinct from the well-established role of MLu as a photodynamic therapy sensitizer in cells. Two analogs of MLu, bearing different coordinated central metal cations, were also explored as controls. The first control, gadolinium texaphyrin (MGd), is a weak photocatalyst but generates reactive oxygen species (ROS) efficiently. The second control, manganese texaphyrin (MMn), is ineffective as both a photocatalyst and a ROS generator. Neither MGd nor MMn was found to trigger pyroptosis under the conditions where MLu was active. Even in the presence of a ROS scavenger, treating MDA-MB-231 cells with MLu at concentrations as low as 50 nM still allows for pyroptosis photo-activation. The present findings highlight how biomolecular photoredox catalysis could contribute to pyroptosis activation by mechanisms largely independent of ROS.

Unleashing the power of porphyrin photosensitizers: Illuminating breakthroughs in photodynamic therapy

This comprehensive review provides the current trends and recent developments of porphyrin-based photosensitizers. We discuss their evolution from first-generation to third-generation compounds, including cutting-edge nanoparticle-integrated derivatives, and explores their pivotal role in advancing photodynamic therapy (PDT) for enhanced cancer treatment. Integrating porphyrins with nanoparticles represents a promising avenue, offering improved selectivity, reduced toxicity, and heightened biocompatibility. By elucidating recent breakthroughs, innovative methodologies, and emerging applications, this review provides a panoramic snapshot of the dynamic field, addressing challenges and charting prospects. With a focus on harnessing reactive oxygen species (ROS) through light activation, PDT serves as a minimally invasive therapeutic approach. This article offers a valuable resource for researchers, clinicians, and PDT enthusiasts, highlighting the potential of porphyrin photosensitizers to improve the future of cancer therapy.

A near-infrared light-activatable Ru(ii)-coumarin photosensitizer active under hypoxic conditions

Photodynamic therapy (PDT) represents a promising approach for cancer treatment. However, the oxygen dependency of PDT to generate reactive oxygen species (ROS) hampers its therapeutic efficacy, especially against hypoxic solid tumors. In addition, some photosensitizers (PSs) have dark toxicity and are only activatable with short wavelengths such as blue or UV-light, which suffer from poor tissue penetration. Herein, we developed a novel hypoxia-active PS with operability in the near-infrared (NIR) region based on the conjugation of a cyclometalated Ru(ii) polypyridyl complex of the type [Ru(C^N)(N^N)₂] to a NIR-emitting COUPY dye. The novel Ru(ii)-coumarin conjugate exhibits water-solubility, dark stability in biological media and high photostability along with advantageous luminescent properties that facilitate both bioimaging and phototherapy. Spectroscopic and photobiological studies revealed that this conjugate efficiently generates singlet oxygen and superoxide radical anions, thereby achieving high photoactivity toward cancer cells upon highly-penetrating 740 nm light irradiation even under hypoxic environments (2% O₂). The induction of ROS-mediated cancer cell death upon low-energy wavelength irradiation along with the low dark toxicity exerted by this Ru(ii)-coumarin conjugate could circumvent tissue penetration issues while alleviating the hypoxia limitation of PDT. As such, this strategy could pave the way to the development of novel NIR- and hypoxia-active Ru(ii)-based theragnostic PSs fuelled by the conjugation of tunable, low molecular-weight COUPY fluorophores.

Coordination Compounds of Cu, Zn, and Ni with Dicarboxylic Acids and N Donor Ligands, and Their Biological Activity: A Review

Complexes of carboxylic acids are very often studied due to their interesting structural, spectral, and magnetic properties. This review is focused on complexes of four dicarboxylic acids, namely, 2,2'-thiodioacetic, 3,3'-thiodipropionic, 3,3'-dithiodipropionic, and fumaric acid. Many of the complexes were characterized by single crystal X-ray analyses. Without the analyses, it is very difficult to predict the coordination mode of carboxylate groups or nitrogen ligands on central atoms. Thus, structural properties are also discussed, as well as potential applications.

Photodynamic therapy for prostate cancer: Recent advances, challenges and opportunities

Over the past two decades, there has been a tendency toward early diagnosis of prostate cancer due to raised awareness among the general public and professionals, as well as the promotion of prostate-specific antigen (PSA) screening. As a result, patients with prostate cancer are detected at an earlier stage. Due to the risks of urine incontinence, erectile dysfunction, etc., surgery is not advised because the tumor is so small at this early stage. Doctors typically only advise active surveillance. However, it will bring negative psychological effects on patients, such as anxiety. And there is a higher chance of cancer progression. Focal therapy has received increasing attention as an alternative option between active monitoring and radical therapy. Due to its minimally invasive, oncological safety, low toxicity, minimal effects on functional outcomes and support by level 1 evidence from the only RCT within the focal therapy literature, photodynamic treatment (PDT) holds significant promise as the focal therapy of choice over other modalities for men with localized prostate cancer. However, there are still numerous obstacles that prevent further advancement. The review that follows provides an overview of the preclinical and clinical published research on PDT for prostate cancer from 1999 to the present. It focuses on clinical applications of PDT and innovative techniques and technologies that address current problems, especially the use of nanoparticle photosensitizers in PDT of prostate cancer.

Photomedicine based on heme-derived compounds

Photoimaging and phototherapy have become major platforms for the diagnosis and treatment of various health complications. These applications require a photosensitizer (PS) that is capable of absorbing light from a source and converting it into other energy forms for detection and therapy. While synthetic inorganic materials such as quantum dots and gold nanorods have been widely explored for their medical diagnosis and photodynamic (PDT) and photothermal (PTT) therapy capabilities, translation of these technologies has lagged, primarily owing to potential cytotoxicity and immunogenicity issues. Of the various photoreactive molecules, the naturally occurring endogenous compound heme, a constituent of red blood cells, and its derivatives, porphyrin, biliverdin and bilirubin, have shown immense potential as noteworthy candidates for clinically translatable photoreactive agents, as evidenced by previous reports. While porphyrin-based photomedicines have attracted significant attention and are well documented, research on photomedicines based on two other heme-derived compounds, biliverdin and bilirubin, has been relatively lacking. In this review, we summarize the unique photoproperties of heme-derived compounds and outline recent efforts to use them in biomedical imaging and phototherapy applications.

Lanthanide-tetrapyrrole complexes: synthesis, redox chemistry, photophysical properties, and photonic applications

Tetrapyrrole derivatives such as porphyrins, phthalocyanines, naphthalocyanines, and porpholactones, are highly stable macrocyclic compounds that play important roles in many phenomena linked to the development of life. Their complexes with lanthanides are known for more than 60 years and present breath-taking properties such as a range of easily accessible redox states leading to photo- and electro-chromism, paramagnetism, large non-linear optical parameters, and remarkable light emission in the visible and near-infrared (NIR) ranges. They are at the centre of many applications with an increasing focus on their ability to generate singlet oxygen for photodynamic therapy coupled with bioimaging and biosensing properties. This review first describes the synthetic paths leading to lanthanide-tetrapyrrole complexes together with their structures. The initial synthetic protocols were plagued by low yields and long reaction times; they have now been replaced with much more efficient and faster routes, thanks to the stunning advances in synthetic organic chemistry, so that quite complex multinuclear edifices are presently routinely obtained. Aspects such as redox properties, sensitization of NIR-emitting lanthanide ions, and non-linear optical properties are then presented. The spectacular improvements in the quantum yield and brightness of Yb^III-containing tetrapyrrole complexes achieved in the past five years are representative of the vitality of the field and open welcome opportunities for the bio-applications described in the last section. Perspectives for the field are vast and exciting as new derivatizations of the macrocycles may lead to sensitization of other Ln^III NIR-emitting ions with luminescence in the NIR-II and NIR-III biological windows, while conjugation with peptides and aptamers opens the way for lanthanide-tetrapyrrole theranostics.

Pyrrole-based photosensitizers for photodynamic therapy — a Thomas Dougherty award paper

Photodynamic therapy (PDT) is a therapeutic modality that uses light to treat malignant or benign diseases. A photosensitizer, light, and oxygen are the three main components needed to generate a cytotoxic effect. Pyrrole-based photosensitizers have been widely used for PDT. Many of the photosensitizers within this class are macrocyclic. This is particularly true for systems that have received regulatory approval or been the subject of clinical trials. However, in recent years, a number of boron dipyrromethanes (BODIPY) have been studied as photosensitizers. Herein, we review examples of some of the most relevant pyrrole-based photosensitizers.

From molecules to nanovectors: Current state of the art and applications of photosensitizers in photodynamic therapy

Photodynamic therapy (PDT) is a concept based on a selective activation by light of drugs called photosensitizers (PS) leading to reactive oxygen species production responsible for cell destruction. Mechanisms of photodynamic reaction and cell photo-destruction following direct or indirect mechanisms will be presented as well as PS classification, from first generation molecules developed in the 1960 s to third generation vectorized PS with improved affinity for tumor cells. Many clinical applications in dermatology, ophthalmology, urology, gastroenterology, gynecology, neurosurgery and pneumology reported encouraging results in human tumor management. However, this interesting technique needs improvements that are currently investigated in the field of PS excitation by the design of new PS intended for two-photon excitation or for X-ray excitation. The former excitation technique is allowing better light penetration and preservation of healthy tissues while the latter is combining PDT and radiotherapy so that external light sources are no longer needed to generate the photodynamic effect. Nanotechnology can also improve the PS to reach the tumor cells by grafting addressing molecule and by increasing its aqueous solubility and consequently its bioavailability by encapsulation in synthetic or biogenic nanovector systems, ensuring good drug protection and targeting. Co-internalization of PS with magnetic nanoparticles in multifunctional vectors or stealth nanoplatforms allows a theranostic anticancer approach. Finally, a new category of inorganic PS will be presented with promising results on cancer cell destruction.

Synthesizing and evaluating the photodynamic efficacy of asymmetric heteroleptic A7B type novel lanthanide bis-phthalocyanine complexes

In this study heteroleptic A₇B type novel Lu(iii) and Eu(iii) lanthanide phthalocyanines (LnPc(Pox)[Pc′(AB₃SH)]) with high extinction coefficients have been synthesized as candidate photosensitizers with reaction yields higher than 33%. The singlet oxygen quantum yields of LuPc(Pox)[Pc′(AB₃SH)] and EuPc(Pox)[Pc′(AB₃SH)], respectively, were measured 17% and 1.4% by the direct method in THF. The singlet oxygen quantum yield of LuPc(Pox)[Pc′(AB₃SH)] in THF is the highest among lutetium(iii) bis-phthalocyanine complexes to date. The photodynamic efficacy of the heteroleptic lanthanide phthalocyanines was evaluated by measuring cell viabilities of A549 and BEAS-2B lung cells, selected to representing in vitro models for testing cancer and normal cells against potential drugs. The cell viabilities demonstrated concentration dependent behavior and were varied by the type of phthalocyanines complexes. Irradiation of the cells for 30 minutes with LED array at 660 nm producing flux of 0.036 J cm⁻² s⁻¹ increased cell death for LuPcPox-OAc, LuPc(Pox)[Pc′(AB₃SH)] and ZnPc. The IC₅₀ concentrations of LuPc(Pox)[Pc′(AB₃SH)] and ZnPc were determined to be below 10 nM for both cell lines, agreeing very well with the singlet oxygen quantum yield measurements. These findings suggest that LuPc(Pox)[Pc′(AB₃SH)] and particularly LuPcPox-OAc are promising drug candidates enabling lowered dose and shorter irradiation time for photodynamic therapy.

Novel bis-lanthanide Lu(iii) and Eu(iii) phthalocyanine complexes have been designed/synthesized and tested their photodynamic efficacy for A549 and BEAS-2B cells in vitro conditions as candidate photosensitizers in PDT.

Role of Photoactive Phytocompounds in Photodynamic Therapy of Cancer

Cancer is one of the greatest life-threatening diseases conventionally treated using chemo- and radio-therapy. Photodynamic therapy (PDT) is a promising approach to eradicate different types of cancers. PDT requires the administration of photosensitisers (PSs) and photoactivation using a specific wavelength of light in the presence of molecular oxygen. This photoactivation exerts an anticancer effect via apoptosis, necrosis, and autophagy of cancer cells. Recently, various natural compounds that exhibit photosensitising potentials have been identified. Photoactive substances derived from medicinal plants have been found to be safe in comparison with synthetic compounds. Many articles have focused on PDT mechanisms and types of PSs, but limited attention has been paid to the phototoxic activities of phytocompounds. The reduced toxicity and side effects of natural compounds inspire the researchers to identify and use plant extracts or phytocompounds as a potent natural PS candidate for PDT. This review focusses on the importance of common photoactive groups (furanocoumarins, polyacetylenes, thiophenes, curcumins, alkaloids, and anthraquinones), their phototoxic effects, anticancer activity and use as a potent PS for an effective PDT outcome in the treatment of various cancers.

Advances in nanomaterials for photodynamic therapy applications: Status and challenges

Photodynamic therapy (PDT), as a non-invasive therapeutic modality that is alternative to radiotherapy and chemotherapy, is extensively investigated for cancer treatments. Although conventional organic photosensitizers (PSs) are still widely used and have achieved great progresses in PDT, the disadvantages such as hydrophobicity, poor stability within PDT environment and low cell/tissue specificity largely limit their clinical applications. Consequently, nano-agents with promising physicochemical and optical properties have emerged as an attractive alternative to overcome these drawbacks of traditional PSs. Herein, the up-to-date advances in the fabrication and fascinating applications of various nanomaterials in PDT have been summarized, including various types of nanoparticles, carbon-based nanomaterials, and two-dimensional nanomaterials, etc. In addition, the current challenges for the clinical use of PDT, and the corresponding strategies to address these issues, as well as future perspectives on further improvement of PDT have also been discussed.

Effects of the Peripheral Substituents, Central Metal, and Solvent on the Photochemical and Photophysical Properties of 5,15-Diazaporphyrins

Metal complexes of 3,7,13,17-tetrakis(di(4-carboxyphenyl)amino)-5,15-diazaporphyrin (MDAP-COOH; M=Pd, Cu) and their ethyl ester precursors (MDAP-COOEt; M=Pd, Cu) have been synthesized for use as near-infrared (NIR)-light-responsive photosensitizers. Under irradiation with visible or NIR light, PdDAP-COOEt in toluene generated singlet oxygen (¹ O₂ ) with an excellent quantum yield (Φ_Δ =0.99), whereas CuDAP-COOEt exhibited a lower efficiency (Φ_Δ =0.21). The water-soluble Pd^II complex PdDAP-COOH also behaved as a photosensitizer (Φ_Δ =0.20) in a micellar solution. The photophysical properties of these dyes were measured by transient absorption techniques. It was found that the efficiency of the energy transfer from the triplet state of MDAP-COOR (R=Et, H) to the ground state of dioxygen was highly dependent on the peripheral substituents, the central metal, and the solvent. Furthermore, the phototoxicity of PdDAP-COOH toward HeLa cells under irradiation of NIR light (720 nm) was evaluated. As expected, PdDAP-COOH exhibited good photodynamic activity, and control experiments confirmed that ¹ O₂ was generated as the active oxygen species.

Photodynamic Therapy for Cancer: What's Past is Prologue

Thomas J Dougherty from Roswell Park Cancer Center played a major role in the progress of photodynamic therapy (PDT) from a laboratory science into a real-world clinical therapy to treat patients with cancer. Nevertheless over the succeeding 45 years, it is fair to say that the overall progress of clinical PDT for cancer has been somewhat disappointing. The goal of this perspective article is to summarize some of the clinical trials run by various companies using photosensitizers with different structures that have been conducted for different types of cancer. While some have been successful, others have failed, and several are now ongoing. I will attempt to touch on some factors, which have influenced this checkered history and look forward to the future of clinical PDT for cancer.

Efficacy and safety of photodynamic therapy with amino-5-laevulinate nanoemulsion versus methyl-5-aminolaevulinate for actinic keratosis: A meta-analysis

BACKGROUND

Photodynamic therapy is an effective treatment for actinic keratosis. 5-aminolevulinic acid nanoemulsion (BF-200 ALA) and methyl-5-aminolevulinate (MAL) are both prodrugs for the treatment of actinic keratosis with photodynamic therapy. A comparison of the efficacy and safety between the drugs is critical for clinical practice.

OBJECTIVES

To investigate if photodynamic therapy in combination with BF-200 ALA is superior to photodynamic therapy with MAL for actinic keratosis.

METHODS

We performed a meta-analysis to investigate the combination of photodynamic therapy with BF-200 ALA and with MAL. The PubMed, Cochrane Library, Web of Science and EMBASE databases were searched to select eligible randomized controlled trials. Our search was conducted on April 1, 2019, and included the search terms "5-aminolevulinic acid nanoemulsion or BF-200 ALA", "methyl-5-aminolevulinate or methyl aminolaevulinate" and "actnic keratosis". Cochrane Risk of Bias Tool was used to estimate the risk of bias.

RESULTS

The meta-analysis consisted of 5988 actinic keratosis lesions in five eligible randomized controlled trials, with a total of 2953 actinic keratosis lesions treated with BF-200 ALA and 3035 actinic keratosis lesions treated with MAL. BF-200 ALA in combination with photodynamic therapy showed significantly higher overall complete clearance rates (RR: 1.07, 95% CI 1.02-1.12, p = 0.01) and 3 month complete clearance rates (RR: 1.09, 95% CI 1.06-1.12, p < 0.00001) compared to MAL. A subgroup analysis was performed for photodynamic therapy combined with BF-200 ALA, revealing increased complete clearance rates of grade II-III lesions in comparison with MAL (RR: 1.24, 95% CI 1.05-1.46, p = 0.01). Compared with MAL, the pooled relative risk for the meta-analysis for recurrence was 0.67 (95% CI 0.48-0.92, p = 0.01) at 12 month after BF-200 ALA treatment.

CONCLUSION

Photodynamic therapy with BF-200 ALA has a 9% better chance of complete clearance at 3 months and a 24% better chance of grade II-III lesions after treatment than with MAL for patients with actinic keratosis.

Mixed and Matched Metallo-Nanotexaphyrin for Customizable Biomedical Imaging

The discovery and synthesis of multifunctional organic building blocks for nanoparticles have remained challenging. Texaphyrin macrocycles are multifunctional, all-organic compounds that possess versatile metal-chelation capabilities and unique theranostics properties for biomedical applications. Unfortunately, there are significant difficulties associated with the synthesis of texaphyrin-based subunits capable of forming nanoparticles. Herein, the detailed synthesis of a texaphyrin-phospholipid building block is reported via a key 1,2-dinitrophenyl-phospholipid intermediate, along with stable chelation of two clinically relevant metal ions into texaphyrin-lipid without compromising their self-assembly into texaphyrin nanoparticles or nanotexaphyrin. A postinsertion methodology to quantitatively insert a variety of metal-ions into preformed nanotexaphyrins is developed and employed to synthesize a structurally stable, mixed ¹¹¹ indium-manganese-nanotexaphyrin for dual modal single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI). In vivo dual SPECT/MRI imaging of ¹¹¹ In-Mn-nanotexaphyrins in an orthotopic prostatic PC3 mouse model demonstrates complementary signal enhancement in the tumor with both modalities at 22 h post intravenous administration. This result highlights the utility of hybrid metallo-nanotexaphyrins to achieve sensitive and accurate detection of tumors by accommodating multiple imaging modalities. The power of this mixed and matched metallo-nanotexaphyrin strategy can be unleashed to allow a diverse range of multifunctional biomedical imaging.

Diazachlorin and diazabacteriochlorin for one- and two-photon photodynamic therapy

Diazachlorin and diazabacteriochlorin have been prepared through reduction of diazaporphyrin and their in vitro and in vivo activity in photodynamic therapy has been investigated.

An updated overview on the development of new photosensitizers for anticancer photodynamic therapy

Photodynamic therapy (PDT), based on the photoactivation of photosensitizers (PSs), has become a well-studied therapy for cancer. Photofrin®, belonging to the first generation of PS, is still widely used for the treatment of different kinds of cancers; however, it has several drawbacks that significantly limit its general clinical use. Consequently, there has been extensive research on the design of PS molecules with optimized pharmaceutical properties, with aiming of overcoming the disadvantages of traditional PS, such as poor chemical purity, long half-life, excessive accumulation into the skin, and low attenuation coefficients. The rational design of novel PS with desirable properties has attracted considerable research in the pharmaceutical field. This review presents an overview on the classical photosensitizers and the most significant recent advances in the development of PS with regard to their potential application in oncology.

The first water coordination sphere of lanthanide(iii) motexafins (Ln-Motex2+, Ln = La, Gd, Lu) and its effects on structures, reduction potentials and UV-vis absorption spectra. Theoretical studies

An explicit treatment of strongly bound water molecules is mandatory to calculate correct UV-vis absorption spectra of lanthanide(iii) motexafins.

On the Potential Use of Squaraine Derivatives as Photosensitizers in Photodynamic Therapy: A TDDFT and RICC2 Survey

A time-dependent density functional theory (TDDFT) and the second-order approximated coupled-cluster model with the resolution of identity approximation (RICC2) studies are reported here for some classes of squaraine derivatives. These compounds have a sharp electronic band, ranging from the visible to near-red part of the spectrum, with an high molar absorption coefficient. These features make them potential photosensitizers in the photodynamic therapy of cancer (PDT), in which a light source, a photosensitizer, and molecular oxygen ((3)O2) are combined to give cytotoxic singlet oxygen ((1)O2) as a final result in a photochemical process. For the examined structures, the introduction of different substituents (electron donating, electron withdrawing, or fused rings) in the parent molecule, in order to give different squaraine derivatives, changes the maximum absorption wavelength (λmax) from 620 to 730 nm, giving a near-red absorbing photosensitizer that can better penetrate human tissue to damage tumor cells. Theoretical results, obtained from both TDDFT/PBE0 and RICC2, are able to reproduce qualitatively the substitution effect on λmax, resulting in a useful tool for testing different structure modifications and, in general, for the molecular design of PDT photosensitizers. Calculated vertical excitation energies (singlet-singlet transitions) generally agree with experimental data within 0.3 eV. The singlet oxygen generation ability of these compounds requires that their triplet energy, for a type II reaction mechanism, should be greater than 0.98 eV. Theoretical triplet energies from the RICC2 method suggests that this requisite is fulfilled for all compounds, though the results are generally overestimated with respect to experiment by 0.7 eV, whereas TDDFT/PBE0 triplet energies, which are underestimated within 0.2 eV in few cases, lie close to the above-mentioned limit and can be considered suitable for PDT applications.

Parts per billion detection of uranium with a porphyrinoid-containing nanoparticle and in vivo photoacoustic imaging

Chemical tools that can report radioactive isotopes would be of interest to the defense community. Here we report ∼250 nm polymeric nanoparticles containing porphyrinoid macrocycles with and without pre-complexed depleted uranium and demonstrate that the latter species may be detected easily and with high sensitivity via photoacoustic imaging. The porphyrinoid macrocycles used in the present study are non-aromatic in the absence of the uranyl cation, but aromatic after cation complexation. We solubilized both the freebase and metalated forms of the macrocycles in poly(lactic-co-glycolic acid) and found a peak in the photoacoustic spectrum at 910 nm excitation in the case of the uranyl complex. The signal was stable for at least 15 minutes and allowed detection of uranium concentrations down to 6.2 ppb (5.7 nM) in vitro and 0.57 ppm (19 fCi; 0.52 μM) in vivo. To the best of our knowledge, this is the first report of a nanoparticle that detects an actinide cation via photoacoustic imaging.

Aminolevulinic acid dendrimers in photodynamic treatment of cancer and atheromatous disease

ALA dendrimers are taken up by caveolae-mediated endocytosis in macrophages. Intracellular ALA release gives rise to PpIX synthesis and subsequent photosensitization of key cells in atheromas and tumour diseases.

Luminescent europium and terbium complexes of dipyridoquinoxaline and dipyridophenazine ligands as photosensitizing antennae: structures and biological perspectives

Luminescent europium and terbium complexes of quinoxaline and phenazine ligands were studied for their structures, luminescence properties, interaction with DNA, and photo-induced DNA cleavage activity.

Photosensitizers in clinical PDT

Photosensitizers in photodynamic therapy allow for the transfer and translation of light energy into a type II chemical reaction. In clinical practice, photosensitizers arise from three families-porphyrins, chlorophylls, and dyes. All clinically successful photosensitizers have the ability to a greater or lesser degree, to target specific tissues or their vasculature to achieve ablation. Each photosensitizer needs to reliably activate at a high enough light wavelength useful for therapy. Their ability to fluoresce and visualize the lesion is a bonus. Photosensitizers developed from each family have unique properties that have so far been minimally clinically exploited. This review looks at the potential benefits and consequences of each major photosensitizer that has been tried in a clinical setting.

Ion responsive near-IR BODIPY dyes: two isomers, two different signals

Different responses of two isomeric tetrastyryl-BODIPY's were studied, shedding light on the path to near IR sensors for metal ions.

Bisanthracene bis(dicarboxylic imide)s as potential photosensitizers in photodynamic therapy: a theoretical investigation

The electronic structures and spectroscopic properties of four bisanthracene bis(dicarboxylic imide)s (M1-M4) have been investigated theoretically by using density functional theory (DFT) and its time-dependent extension (TDDFT) in view of their potential use as photosensitizers in photodynamic therapy (PDT). The optimized geometries, electronic absorption transitions, singlet-triplet energy gaps, spin-orbit matrix elements, ionization potentials, and electron affinities have been determined in gas phase and in solvent. Both type I and II PDT mechanisms have been considered. In addition, the variation of a series of relevant properties upon heavy atom substitution (Br and I) have been determined and discussed. Results show that only M4 is able to support the type I reaction, and one of its brominated and iodinated derivatives can produce cytotoxic singlet oxygen (type II reaction).

Zinc coproporphyrin I derived from meconium has an antitumor effect associated with singlet oxygen generation

INTRODUCTION

Zinc coproporphyrin I (ZnCP-I) is a photosensitive molecule and a major component of meconium. Here, we examined the effects of ZnCP-I as a potential photosensitizer in photodynamic therapy for tumors.

MATERIALS AND METHODS

(1) Aqueous ZnCP-I was irradiated with a pulsed YAG-SHG laser (wavelength: 532 nm)/YAG-SHG dye laser (wavelength: 566 nm). (2) HeLa cells were incubated in 200 mM ZnCP-I, and accumulation of ZnCP-I in HeLa cells was evaluated with ZnCP-I-specific fluorescence over 500 nm. (3) Aqueous ZnCP-I was administered intravenously to HeLa tumor-bearing mice at a dose of 10.2 mg/kg body weight. The tumors were irradiated with a filtered halogen lamp (wavelength: 580 nm) at 100 J/cm(2) 20 min after administration.

RESULTS

(1) An intense near-infrared emission spectrum was observed at around 1,270 nm after irradiation. The emission intensity was proportional to the laser power between 10 and 80 mW and was completely inhibited by addition of NaN3, a singlet oxygen scavenger. (2) ZnCP-I-specific fluorescence was detected in the HeLa cell cytoplasm. (3) Irradiated tumors treated with ZnCP-I were mostly necrotized.

CONCLUSION

ZnCP-I accumulated in tumor cells, produced singlet oxygen upon irradiation, and necrotized the tumor cells. These results suggest that ZnCP-I may be an effective photosensitizer.

Application of near-infrared dyes for tumor imaging, photothermal, and photodynamic therapies

Near-infrared (NIR) dyes, small organic molecules that function in the NIR region, have received increasing attention in recent years as diagnostic and therapeutic agents in the field of tumor research. They have been demonstrated great successes in imaging and treating tumors both in vitro and in vivo. And their different applications in clinical practices have made rapid gains. This review primarily focuses on the progress of the application of NIR dyes in tumor imaging and therapy. In particular, advances in the use of different NIR dyes in tumor-specific imaging, photothermal, and photodynamic therapies are discussed. Limitations and prospects associated with NIR dyes in diagnostic and therapeutic application are also reviewed.

Motexafin gadolinium: a promising radiation sensitizer in brain metastasis

INTRODUCTION

Motexafin gadolinium is a radiation sensitizer that is in the class of drugs known as texaphyrins. Though this drug is currently not FDA approved in the management of brain tumors, several prospective studies have been done showing promise with this agent, which this review highlights.

AREAS COVERED

This paper provides a clinical context by reviewing the background of radiosensitizers, followed by a review of the preclinical discovery of motexafin gadolinium and its clinical testing. We also highlight its most promising applications and comment on the reasons for the observed clinical outcomes.

EXPERT OPINION

Motexafin gadolinium is a novel radiosensitizer with clearly documented efficacy, particularly in patients with brain metastases. If this agent had been tested upfront in patients diagnosed with brain metastases from NSCLC who had not been delayed by the administration of systemic chemotherapy, it may have become part of the standard of care in this setting. Continued investigations using this agent are under way and remain promising.

Texaphyrins: a new approach to drug development

The texaphyrins are prototypical metal-coordinating expanded porphyrins. They represent a burgeoning class of pharmacological agents that show promise for an array of medical applications. Currently, two different water-soluble lanthanide texaphyrins, namely motexafin gadolinium ( Gd-Tex , 1) and motexafin lutetium ( Lu-Tex , 2), are involved in multi-center clinical trials for a variety of indications. The first of these agents, XCYTRIN® (motexafin gadolinium) Injection, is being evaluated as a potential X-ray radiation enhancer in a randomized Phase III clinical trial in patients with brain metastases. The second, in various formulations, is being evaluated as a photosensitizer for use in: (i) the photodynamic treatment of recurrent breast cancer (LUTRIN® Injection; now in Phase IIb clinical trials); (ii) photoangioplastic reduction of atherosclerosis involving peripheral and coronary arteries (ANTRIN® Injection; now in Phase II and Phase I clinical trials, respectively); and (iii) light-based age-related macular degeneration (OPTRIN™ Injection; currently under Phase II clinical evaluation), a vision-threatening disease of the retina. In this article, these developments, along with fundamental aspects of the underlying chemistry are reviewed.

Pharmaceutical development and medical applications of porphyrin-type macrocycles

The current state of pharmaceutical development of porphyrin-type macrocycles in medicine is highlighted. Currently, several porphyrinoid-based drugs are under various stages of development as phototherapeutic agents, X-ray radiation enhancers and boron neutron capture agents. These compounds represent a burgeoning class of pharmacological agents that are potentially useful in an array of treatment areas.

Photosensitization by the Near-IR-absorbing Photosensitizer Lutetium Texaphyrin: Spectroscopic, In Vitro and In Vivo Studies

The spectroscopic and biological properties of the new photosensitizer lutetium texaphyrin (Lu-Tex) were assessed in vitro and in vivo on a C26 colon carcinoma model, in comparison with hematoporphyrin (Hp), photofrin II (PII) and chlorin e 6( Chl ). Strong binding of Lu-Tex to lipid bilayer membranes was observed. The results of confocal fluorescence microscopy on C26 cells showed that Lu-Tex was localized in small vesicles in the cytoplasm, possibly in the lysosomes, while Chl and Hp were distributed in larger cytoplasmic vesicles attributed to mitochondria. Scanning electron microscopy and X-ray microanalysis revealed that photodynamic therapy with Lu-Tex induced only slight damage to the cell membrane, leading to a delayed cell response. Chl and Hp caused significant structural damage to the outer cell membrane, resulting in ionic imbalance and fast cell death. The in vitro quantitative assessment of the relative efficiency per absorbed photon of the sensitizers revealed that Lu-Tex was less effective than Chl and Hp . However, the results of our in vivo study showed that at the same light and drug doses the anti-tumor efficiency of the agents was in the following order: Lu-Tex > Chl > PII . The strong in vivo anti-tumor effect of Lu-Tex can be explained by its higher integrated absorption in the long-wavelength range.