Synthesis, Photophysical Properties, and Biological Evaluation of trans-Bisthioglycosylated Tetrakis(fluorophenyl)chlorin for Photodynamic Therapy

A silyl porphyrin derivative conjugated with 6-deoxy-6-sulfo-α-d-glucopyranose functions as an efficient photosensitizer for photodynamic therapy

We synthesized a new silyl porphyrin derivative conjugated with 6-deoxy-6-sulfo-α-d-glucopyranose (SGlc). Conjugation with SGlc improved A549 cellular uptake without significant changes in the photophysical and photochemical properties and subcellular localization. This improved cellular uptake led to enhanced photodynamic activity. Furthermore, conjugation with SGlc suppressed dark toxicity. These advantages were not observed for a conjugate with a glucose molecule. These results indicated that the conjugation with SGlc is a promising strategy for enhancing photodynamic efficacy.

Synthesis of novel zinc porphyrins with bioisosteric replacement of Sorafenib: Efficient theranostic agents for anti-cancer application

Novel zinc porphyrins (trans-A2B2 and A3B type) are reported containing pharmacophoric groups derived from Sorafenib at the meso-positions. The pharmacophoric and bioisosteric modification of Sorafenib was done with 2-methyl-4-nitro-N-phenylaniline. The in-vitro photo-cytotoxicity studies of zinc porphyrins on HeLa cells revealed excellent PDT based autophagy inhibition of cancer cells, with IC50 values between 6.2 to 15.4 μM. The trans-A2B2 type zinc porphyrin with two bioisosteric groups gave better cytotoxicity than A3B type. Molecular docking studies revealed excellent binding with mTOR protein kinase of the designed porphyrins. The confocal studies indicated significant ER localization of trans-A2B2 type zinc porphyrin in HeLa cells along with ROS generation. trans-A2B2 type zinc porphyrin induced ER stress in cancer cells, thereby causing elevation of Ca+2 ions in cytoplasm, which led to cancer cell death via autophagy pathway. The studies suggested that trans-A2B2 and A3B type zinc porphyrins can be developed as theranostic agents for anti-cancer applications.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Charge density distribution effect in pyrrolidine-fused chlorins on microbial uptake and antimicrobial photoinactivation of microbial pathogens

Two novels structurally related pyrrolidine-fused chlorins were synthesized from 5,10,15,20-tetrakis(pentafluorophenyl)chlorin by nucleophilic aromatic substitution of the para-fluoro groups. The reaction with 2-dimethylaminoethanol produced TPCF₁₆-NMe₂ in 77% yield, while TPCF₁₆-NBu was obtained using butylamine in 87% yield. The latter was extensively methylated to form TPCF₁₆-N⁺Bu in 92% yield. The synthetic strategy was designed to compare the effect of charge density distribution on chlorin in the efficacy to induce photodynamic inactivation of pathogens. TPCF₁₆-NMe₂ has five tertiary amines that can acquire positive charges in aqueous medium by protonation. Furthermore, four of the cationic groups are located in amino groups linked to the chlorine macrocycle by an aliphatic structure of two carbon atoms, which gives it greater movement capacity. In contrast, TPCF₁₆-N⁺Bu presents intrinsic positive charges on aromatic rings. Absorption and fluorescence emission properties were not affected by the peripheral substitution on the chlorin macrocycle. Both photosensitizers (PSs) were able to form singlet molecular oxygen and superoxide anion radical in solution. Uptake and photodynamic inactivation mediated by these chlorins were examined on Staphylococcus aureus and Escherichia coli. Both phototherapeutic agents produced efficient photoinactivation of S. aureus. However, only TPCF₁₆-NMe₂ was rapidly bound to E. coli cells and this chlorin was effective to photoinactivate both strains of bacteria using lower concentrations and shorter irradiation periods. Our outcomes reveal that the charge density distribution is a key factor to consider in the development of new PSs. Accordingly, this work stands out as a promising starting point for the design of new tetrapyrrolic macrocycles with application in PDI.

Applications of Fluorous Porphyrinoids: An Update†

Porphyrins and related macrocycles have been studied broadly for their applications in medicine and materials because of their tunable physicochemical, optoelectronic and magnetic properties. In this review article, we focused on the applications of fluorinated porphyrinoids and their supramolecular systems and summarized the reports published on these chromophores in the past 5-6 years. The commercially available fluorinated porphyrinoids: meso-perfluorophenylporphyrin (TPPF₂₀ ) perfluorophthalocyanine (PcF₁₆ ) and meso-perfluorophenylcorrole (CorF₁₅ ) have increased photo and oxidative stability due to the presence of fluoro groups. Because of their tunable properties and robustness toward oxidative damage these porphyrinoid-based chromophores continue to gain attention of researchers developing advanced functional materials for applications such as sensors, photonic devices, component for solar cells, biomedical imaging, theranostics and catalysts.

Application of phototherapeutic-based nanoparticles in colorectal cancer

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second leading cause of cancer death, which accounts for approximately 10% of all new cancer cases worldwide. Surgery is the main method for treatment of early-stage CRC. However, it is not effective for most metastatic tumors, and new treatment and diagnosis strategies need to be developed. Photosensitizers (PSs) play an important role in the treatment of CRC. Phototherapy also has a broad prospect in the treatment of CRC because of its low invasiveness and low toxicity. However, most PSs are associated with limitations including poor solubility, poor selectivity and high toxicity. The application of nanomaterials in PSs has added many advantages, including increased solubility, bioavailability, targeting, stability and low toxicity. In this review, based on phototherapy, we discuss the characteristics and development progress of PSs, the targeting of PSs at organ, cell and molecular levels, and the current methods of optimizing PSs, especially the application of nanoparticles as carriers in CRC. We introduce the photosensitizer (PS) targeting process in photodynamic therapy (PDT), the damage mechanism of PDT, and the application of classic PS in CRC. The action process and damage mechanism of photothermal therapy (PTT) and the types of ablation agents. In addition, we present the imaging examination and the application of PDT / PTT in tumor, including (fluorescence imaging, photoacoustic imaging, nuclear magnetic resonance imaging, nuclear imaging) to provide the basis for the early diagnosis of CRC. Notably, single phototherapy has several limitations in vivo, especially for deep tumors. Here, we discuss the advantages of the combination therapy of PDT and PTT compared with the single therapy. At the same time, this review summarizes the clinical application of PS in CRC. Although a variety of nanomaterials are in the research and development stage, few of them are actually on the market, they will show great advantages in the treatment of CRC in the near future.

Synthesis of Water-Soluble Thioglycosylated trans-A2B2 Type Porphyrins: Cellular Uptake Studies and Photodynamic Efficiency

The synthesis of water-soluble thioglycosylated A₂B₂ type porphyrins and their zinc(II) complexes is reported. The water-soluble trans-A₂B₂ porphyrins were synthesized in two steps, via [2+2] condensation between thioglycosylated dipyrromethanes and aromatic aldehydes in 15-21% yields. The thioglycosylated trans-A₂B₂ porphyrins showed decent in vitro singlet oxygen generation, which was supported by the intracellular DCFDA study. The in vitro cellular investigations of thioglycosylated A₂B₂ porphyrins were carried out in lung cancer cells (A549) to test their photodynamic therapeutic (PDT) activity. The PDT study revealed significant cytotoxicities of porphyrins with IC₅₀ values between 23.3 and 44.2 μM in the dark, whereas, after visible light exposure, the photosensitizers exhibited IC₅₀ values around 11.1-23.8 μM. The water-soluble thioglycosylated zinc(II) porphyrins having two meso-N-butylcarbazole groups exhibited an excellent degree of photocytotoxicity (IC₅₀ = 4.6-8.8 μM). The flow cytometry analysis revealed that cellular uptake and ROS (reactive oxygen species) generation efficiency of water-soluble thioglycosylated zinc(II) porphyrins were considerably higher than nonmetalated porphyrins. Confocal microscopy images displayed substantial distribution in the endoplasmic reticulum with partial colocalization in mitochondria and lysosomes of water-soluble thioglycosylated zinc(II) porphyrins in A549 cells.

PEGylated Purpurin 18 with Improved Solubility: Potent Compounds for Photodynamic Therapy of Cancer

Purpurin 18 derivatives with a polyethylene glycol (PEG) linker were synthesized as novel photosensitizers (PSs) with the goal of using them in photodynamic therapy (PDT) for cancer. These compounds, derived from a second-generation PS, exhibit absorption at long wavelengths; considerable singlet oxygen generation and, in contrast to purpurin 18, have higher hydrophilicity due to decreased logP. Together, these properties make them potentially ideal PSs. To verify this, we screened the developed compounds for cell uptake, intracellular localization, antitumor activity and induced cell death type. All of the tested compounds were taken up into cancer cells of various origin and localized in organelles known to be important PDT targets, specifically, mitochondria and the endoplasmic reticulum. The incorporation of a zinc ion and PEGylation significantly enhanced the photosensitizing efficacy, decreasing IC50 (half maximal inhibitory compound concentration) in HeLa cells by up to 170 times compared with the parental purpurin 18. At effective PDT concentrations, the predominant type of induced cell death was apoptosis. Overall, our results show that the PEGylated derivatives presented have significant potential as novel PSs with substantially augmented phototoxicity for application in the PDT of cervical, prostate, pancreatic and breast cancer.

Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

Maleimide-containing fluorinated porphyrins and chlorins were prepared based on the reaction of Zn(II) or Ni(II) complexes of 5,10,15,20-tetrakis(4-amino-2,3,5,6-tetrafluorophenyl)porphyrin and chlorin with maleic anhydride. Porphyrin maleimide derivatives were also prepared by the reaction of 5,10,15,20-tetrakis(4-azido-2,3,5,6-tetrafluorophenyl)porphyrinato Zn(II) or Ni(II) with N-propargylmaleimide via the CuAAC click reaction to afford fluorinated porphyrin-triazole-maleimide conjugates. New maleimide derivatives were isolated in reasonable yields and identified by UV-vis, 1H NMR, 19F NMR spectroscopy and mass-spectrometry.

Overview of Recent Strategic Advances in Medicinal Chemistry

Introducing novel strategies, concepts, and technologies that speed up drug discovery and the drug development cycle is of great importance both in the highly competitive pharmaceutical industry as well as in academia. This Perspective aims to present a "big-picture" overview of recent strategic innovations in medicinal chemistry and drug discovery.

One-Pot Synthesis of Four Chlorin Derivatives by a Divergent Ylide

Chlorins have unique photophysical properties that are exploited in diverse biological and materials applications. De novo chlorin synthesis with specific exocyclic motifs can be challenging and many are not stable to photobleaching and/or oxidation. A facile approach to a stable synthetic chlorin with a fused N-methyl pyrrolidine uses cyclo addition of a sarcosine-based azomethine ylide on 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)-porphyrin (TPPF₂₀) is reported, but this approach has limitations. We report the synthesis of stable chlorin scaffolds starting with TPPF₂₀ using a new glycine-based N-(hydroxymethyl)- N-methelenemethanideaminium ylide. Careful control of the 1,3-dipolar cycloaddition reaction allows a divergent use of the glycine derived ylide to yield four new chlorins, including the fused NH-pyrrolidine, two dimers, and the same N-methyl chlorin product from the sarcosine ylide reaction. The mechanism begins with the formation of a bis(hydroxymethyl)glycine, which then dehydrates and decarboxylates to form the active N-(hydroxymethyl)- N-methelenemethanideaminium ylide, which then reacts with TPPF₂₀ to form a key N-(hydroxymethyl)-17,18-pyrrolidinyl-chlorin intermediate. Deformylation of this intermediate affords the (17,18-pyrrolidinyl)-chlorin, whereas a Cannizzaro-type reaction promotes a hydride attack to an imine chlorin cation to yield the N-methyl chlorin. The exocyclic NH-pyrrolidine provides a unique mode of attaching chiral moieties that avoids formation of diasteromers at the bridgehead carbons.

A review and outlook in the treatment of osteosarcoma and other deep tumors with photodynamic therapy: from basic to deep

Photodynamic therapy, one of the most promising minimally invasive treatments, has received increasing focus in tumor therapy research, which has been widely applied in treating superficial tumors. Three basic factors - photosensitizer, the light source, and oxidative stress - are responsible for tumor cell cytotoxicity. However, due to insufficient luminous flux and peripheral tissue damage, the utilization of photodynamic therapy is facing a huge limitation in deep tumor therapy. Osteosarcoma is the typical deep tumor, which is the most commonly occurring malignancy in children and adolescents. Despite developments in surgery, high risks of the amputation still threatens the health of osteosarcoma patients. In this review, we summarize recent developments in the field of photodynamic therapy and specifically PDT research in OS treatment modalities. In addition, we also provide some novel suggestions, which could potentially be a breakthrough in PDT-induced OS therapies. PDT has the potential to become an effective therapy while the its limitations still present when applied on the treatment of OS or other types of deep tumors. Thus, more researches and studies in the field are required.

Applications of functionalized nanomaterials in photodynamic therapy

Specially designed functionalized nanomaterials such as superparamagnetic iron oxide, gold, quantum dots and up- and down-conversion lanthanide series nanoparticles have consistently and completely revolutionized the biomedical environment over the past few years due to their specially inferring properties, such as specific drug delivery, plasmonic effect, optical and imaging properties, therapeutic thermal energy productionand excellent irresistible cellular penetration. These properties have been used to improve many existing disease treatment modalities and have led to the development of better therapeutic approaches for the advancement of the treatment of critical human diseases, such as cancers and related malaise. In photodynamic therapy, for example, where the delivery of therapeutic agents should ideally avoid toxicity on nearby healthy cells, superparamagnetic iron oxide nanoparticles have been shown to be capable of making photodynamic therapy (PDT) prodrugs and their associative targeting moieties tumor-specific via their unique response to an external magnetic fields. In this review, the nanomaterials commonly employed for the enhancement of photodynamic therapy are discussed. The review further describes the various methods of synthesis and characterization of these nanomaterials and highlights challenges for improving the efficacy of PDT in the future.

Mitochondrial Reactive Oxygen Species and Photodynamic Therapy

Worldwide, the number of cancer cases is increasing. Typically, they are treated by either surgery or chemotherapy. However, these treatments may be undesirable in elderly patients or those who are under medication with antiplatelet drugs. Photodynamic therapy (PDT) represents a potentially attractive treatment option for these types of patients, since it does not involve surgery and has considerably reduced side effects compared to chemotherapy. Porphyrin, one of the most commonly used photosensitizers, has the convenient property of cancer-specific accumulation and therefore, is commonly used in PDT. However, the mechanism by which this cancer-specific accumulation occurs remains unclear. We previously reported that a heme-transport protein, HCP1, was capable of transporting porphyrin compounds. HCP1 expression is associated with increased hypoxia, although the detailed mechanism by which this regulation occurs is also unknown. Here, we review available data on the mechanism of regulation of HCP1 expression through mitochondrial reactive oxygen species (mitROS). Specifically, cancer cells show increased expression of HCP1 compared to normal cells and this over-expression is reduced in cancer cells over-expressing the mitROS scavenging enzyme manganese superoxide dismutase (MnSOD). Thus we conclude that mitROS is involved in regulating HCP1 expression.