Microwave-mediated ‘click-chemistry’ synthesis of glycoporphyrin derivatives and in vitro photocytotoxicity for application in photodynamic therapy

Clicking in harmony: exploring the bio-orthogonal overlap in click chemistry

In the quest to scrutinize and modify biological systems, the global research community has continued to explore bio-orthogonal click reactions, a set of reactions exclusively targeting non-native molecules within biological systems. These methodologies have brought about a paradigm shift, demonstrating the feasibility of artificial chemical reactions occurring on cellular surfaces, in the cell cytosol, or within the body - an accomplishment challenging to achieve with the majority of conventional chemical reactions. This review delves into the principles of bio-orthogonal click chemistry, contrasting metal-catalyzed and metal-free reactions of bio-orthogonal nature. It comprehensively explores mechanistic details and applications, highlighting the versatility and potential of this methodology in diverse scientific contexts, from cell labelling to biosensing and polymer synthesis. Researchers globally continue to advance this powerful tool for precise and selective manipulation of biomolecules in complex biological systems.

CuAAC ensembled 1,2,3-triazole linked nanogels for targeted drug delivery: a review

Copper(i) catalyzed alkyne azide cycloaddition (CuAAC), the quintessential example of 'click chemistry', provides an adaptable and adequate platform for the synthesis of nanogels for sustained drug release at targeted sites because of their better biocompatibility. The coupling of drugs, carried out via various synthetic routes including CuAAC, into long-chain polymeric forms like nanogels has exhibited considerable assurance in therapeutic advancements and intracellular drug delivery due to the progression of water solubility, evacuation of precocious drug release, and improved upthrust of the pharmacokinetics of the nanogels, thereby rendering them as better and efficient drug carriers. The inefficiency of drug transmission to the target areas due to the resistance of complex biological barriers in vivo is a major hurdle that impedes the therapeutic translation of nanogels. This review compiles the data of nanogels synthesized specifically via CuAAC 'click' methodology, as scaffolds for targeted drug delivery and their assimilation into nanomedicine. In addition, it elaborates the ability of CuAAC to graft specific moieties and conjugating biomolecules like proteins and growth factors, onto orthogonally functionalized polymer chains with various chemical groups resulting in nanogels that are not only more appealing but also more effective at delivering drugs, thereby enhancing their site-specific target approach and initiating selective therapies.

Erlotinib-Modified BODIPY Photosensitizers for Targeted Photodynamic Therapy

Photodynamic therapy (PDT) is an innovative, non-invasive and highly selective therapeutic modality for tumours and non-malignant diseases. BODIPY based molecules can function as new generation photosensitizers (PSs) in various PDT applications. Despite numerous conjugated PS systems are available, BODIPYs containing erlotinib lagged behind other photosensitizer units. In this study, smart photosensitizers containing BODIPY, erlotinib and hydrophilic units were prepared for the first time, their physicochemical properties and PDT effects were investigated. Compared with non-halogenated compound, halogenated derivatives possessed much lower fluorescence profile as well as the good ROS generation ability under red light. In vitro PDT studies were performed on both healthy (PNT1a) and prostate cancerous cells (PC3) to determine the selectivity of the compounds on cancerous cells and their effects under light. The halogenated conjugates, exposed to low dose of light illumination exhibited potent activity on cancer cell viability and the calculated IC₅₀ values proved the high phototoxicity of the photosensitizers. It was also determined that the PSs have very low dark toxicity and that the light illumination and ROS formation are required for the initiation of the cell death mechanism. As a result, erlotinib modified BODIPYs could serve as promising agents in anticancer photodynamic therapy.

New porphyrin photosensitizers-Synthesis, singlet oxygen yield, photophysical properties and application in PDT

This research on porphyrin-based photosensitizer system has a very important theoretical and practical significance in the photodynamic therapy (PDT) treatment of cancer. Based on this, in this article, a series of porphyrin derivatives were first designed and synthesized, and a "push-pull" porphyrin photosensitizer with two symmetrical ethanethioate groups was finally constructed. Based on the characterization of their chemical structures (¹H and¹³C NMR, MS, IR, and UV-Vis spectroscopy) and the use of the density functional theory (DFT) and time-dependent DFT (TDDFT) to address the nature of the excited states as well as the dark/phototoxicity, the results have indicated the relationship between the porphyrin structure and properties. The experimental and theoretical UV-Vis absorption properties of porphyrins were discussed. The four porphyrin compounds synthesized all demonstrated a high capacity to generate singlet oxygen under long-wavelength (590 nm) light and low dark toxicity. Compared with the conventional porphyrin photosensitizers, P4 with a CT band (from 580 to 750 nm) is beneficial to the penetration of the light, presenting the potential for applications in PDT.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

Synthesis, Characterization and Photodynamic Activity against Bladder Cancer Cells of Novel Triazole-Porphyrin Derivatives

Novel triazole-porphyrin derivatives (TZ-PORs) were synthesized through the Heck reaction and then incorporated into polyvinylpyrrolidone (PVP) micelles. After verifying that this incorporation did not compromise the photophysical and chemical features of TZ-PORs as photosensitizers, the phototoxicity of the formulations towards cancer cells was screened. Biological studies show high photodynamic activity of all PVP-TZ-POR formulations against a bladder cancer cell line with a particular highlight to PVP-TZ-POR 7e and 7f that are able to significantly reduce HT-1376 cell viability, while they had no effect on control ARPE-19 cells.

Synthesis of Porphyrin and Bacteriochlorin Glycoconjugates through CuAAC Reaction Tuning

Rapid and reproducible access to a series of unique porphyrin and bacteriochlorin glycoconjugates, including meso-glycosylated porphyrins and bacteriochlorins, and beta-glycosylated porphyrins, via copper catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) is reported for the first time. The work presented highlights the system-dependent reaction conditions required for glycosylation to porphyrins and bacteriochlorins based on the unique electronic properties of each ring system. Attenuated reaction conditions were used to synthesize fifteen new glycosylated porphyrin and bacteriochlorin analogs in 74 - 99% yield, and were extended to solid support to produce the first oligo(amidoamine)-based porphyrin glycoconjugate. These compounds hold significant potential as next generation water soluble catalysts and photodynamic therapy/photodynamic inactivation (PDT/PDI) agents.

Water-dispersible glycosylated poly(2,5'-thienylene)porphyrin-based nanoparticles for antibacterial photodynamic therapy

Here we report the preparation of water-dispersible glycosylated poly(2,5'-thienylene)porphyrin based nanoparticles by a nanoprecipitation method and demonstrate the application of these nanoparticles in antibacterial photodynamic therapy. The diameter of the nanoparticles is in the range of 50-80 nm and the resulting nanoparticles are stable in water without precipitation at least for a month. They have high singlet oxygen efficiency and display light-triggered biocidal activity against both Gram negative bacteria (Escherichia coli, E. coli) and Gram positive bacteria (Bacillus subtilis, B. subtilis). Upon white light irradiation for 10 min with a flux of 22 mW cm-2 of the E. coli suspension incubated with NPs (18 μg mL-1), a killing efficiency of 99% is achieved, whereas in the dark the effect is recorded as only around 8%.

Synthesis and Characterization of Oligothiophene-Porphyrin-Based Molecules That Can Be Utilized for Optical Assignment of Aggregated Amyloid-β Morphotypes

Molecular tools for fluorescent imaging of protein aggregates are essential for understanding the significance of these pathological hallmarks in proteopathic neurodegenerative diseases, such as Alzheimer's disease. Here, we report the synthesis of a series of oligothiophene porphyrin hybrids, OTPHs, and the evaluation of these dyes for fluorescent imaging of beta-amyloid aggregates in tissue sections from a transgenic mouse model with Alzheimer's disease pathology. The OTPHs proved to be successful for spectral and lifetime imaging assessment of protein deposits and our findings confirm that the enhanced spectral range and distinct lifetime diversity of these novel tools allow a more precise assessment of heterogeneous amyloid morphology compared with the corresponding oligothiophene dye. In addition, the chemical identity of the porphyrin moiety, as well as the spacing between the two optical active moieties, influenced the OTPHs performance for fluorescent assignment of the protein deposits. We foresee that our findings will aid in the chemical design of dyes that can be utilized as optical tools for studying the polymorphic nature of protein aggregates associated with proteopathic neurodegenerative diseases.

Synthesis and Characterization of Novel Fluoro-glycosylated Porphyrins that can be Utilized as Theranostic Agents

Small molecules with modalities for a variety of imaging techniques as well as therapeutic activity are essential, as such molecules render opportunities to simultaneously conduct diagnosis and targeted therapy, so called theranostics. In this regard, glycoporphyrins have proven useful as theranostic agents towards cancer, as well as noncancerous conditions. Herein, the synthesis and characterization of heterobifunctional glycoconjugated porphyrins with two different sugar moieties, a common monosaccharide at three sites, and a 2-fluoro-2-deoxy glucose (FDG) moiety at the fourth site are presented. The fluoro-glycoconjugated porphyrins exhibit properties for multimodal imaging and photodynamic therapy, as well as specificity towards cancer cells. We foresee that our findings might aid in the chemical design of heterobifunctional glycoconjugated porphyrins that could be utilized as theranostic agents.

Carbon-1 versus Carbon-3 Linkage of d-Galactose to Porphyrins: Synthesis, Uptake, and Photodynamic Efficiency

The use of glycosylated compounds is actively pursued as a therapeutic strategy for cancer due to the overexpression of various types of sugar receptors and transporters on most cancer cells. Conjugation of saccharides to photosensitizers such as porphyrins provides a promising strategy to improve the selectivity and cell uptake of the photosensitizers, enhancing the overall photosensitizing efficacy. Most porphyrin-carbohydrate conjugates are linked via the carbon-1 position of the carbohydrate because this is the most synthetically accessible approach. Previous studies suggest that carbon-1 galactose derivatives show diminished binding since the hydroxyl group in the carbon-1 position of the sugar is a hydrogen bond acceptor in the galectin-1 sugar binding site. We therefore synthesized two isomeric porphyrin-galactose conjugates using click chemistry: one linked via the carbon-1 of the galactose and one linked via carbon-3. Free base and zinc analogs of both conjugates were synthesized. We assessed the uptake and photodynamic therapeutic (PDT) activity of the two conjugates in both monolayer and spheroidal cell cultures of four different cell lines. For both the monolayer and spheroid models, we observe that the uptake of both conjugates is proportional to the protein levels of galectin-1 and the uptake is suppressed after preincubation with an excess of thiogalactose, as measured by fluorescence spectroscopy. Compared to that of the carbon-1 conjugate, the uptake of the carbon-3 conjugate was greater in cell lines containing high expression levels of galectin-1. After photodynamic activation, MTT and lactate dehydrogenase assays demonstrated that the conjugates induce phototoxicity in both monolayers and spheroids of cancer cells.

trans-A2B-corrole bearing 2,3-di(2-pyridyl)quinoxaline (DPQ)/phenothiazine moieties: synthesis, characterization, electrochemistry and photophysics

Singlet–singlet energy transfer and electron transfer processes in corrole–phenothiazine and corrole–DPQ dyads were demonstrated by using electrochemical and fluorescence (steady-state and time-resolved) spectral studies.

Amphiphilic BODIPY-Hydroporphyrin Energy Transfer Arrays with Broadly Tunable Absorption and Deep Red/Near-Infrared Emission in Aqueous Micelles

BODIPY-hydroporphyrin energy transfer arrays allow for development of a family of fluorophores featuring a common excitation band at 500 nm, tunable excitation band in the deep red/near-infrared window, and tunable emission. Their biomedical applications are contingent upon retaining their optical properties in an aqueous environment. Amphiphilic arrays containing PEG-substituted BODIPY and chlorins or bacteriochlorins were prepared and their optical and fluorescence properties were determined in organic solvents and aqueous surfactants. The first series of arrays contains BODIPYs with PEG substituents attached to the boron, whereas in the second series, PEG substituents are attached to the aryl at the meso positions of BODIPY. For both series of arrays, excitation of BODIPY at 500 nm results in efficient energy transfer to and bright emission of hydroporphyrin in the deep-red (640-660 nm) or near-infrared (740-760 nm) spectral windows. In aqueous solution of nonionic surfactants (Triton X-100 and Tween 20) arrays from the second series exhibit significant quenching of fluorescence, whereas properties of arrays from the first series are comparable to those observed in polar organic solvents. Reported arrays possess large effective Stokes shift (115-260 nm), multiple excitation wavelengths, and narrow, tunable deep-red/near-IR fluorescence in aqueous surfactants, and are promising candidates for a variety of biomedical-related applications.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Synthesis and Functionalization of Porphyrins through Organometallic Methodologies

This review focuses on the postfunctionalization of porphyrins and related compounds through catalytic and stoichiometric organometallic methodologies. The employment of organometallic reactions has become common in porphyrin synthesis. Palladium-catalyzed cross-coupling reactions are now standard techniques for constructing carbon-carbon bonds in porphyrin synthesis. In addition, iridium- or palladium-catalyzed direct C-H functionalization of porphyrins is emerging as an efficient way to install various substituents onto porphyrins. Furthermore, the copper-mediated Huisgen cycloaddition reaction has become a frequent strategy to incorporate porphyrin units into functional molecules. The use of these organometallic techniques, along with the traditional porphyrin synthesis, now allows chemists to construct a wide range of highly elaborated and complex porphyrin architectures.

Cu-Catalyzed Click Reaction in Carbohydrate Chemistry

Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC), popularly known as the "click reaction", serves as the most potent and highly dependable tool for facile construction of simple to complex architectures at the molecular level. Click-knitted threads of two exclusively different molecular entities have created some really interesting structures for more than 15 years with a broad spectrum of applicability, including in the fascinating fields of synthetic chemistry, medicinal science, biochemistry, pharmacology, material science, and catalysis. The unique properties of the carbohydrate moiety and the advantages of highly chemo- and regioselective click chemistry, such as mild reaction conditions, efficient performance with a wide range of solvents, and compatibility with different functionalities, together produce miraculous neoglycoconjugates and neoglycopolymers with various synthetic, biological, and pharmaceutical applications. In this review we highlight the successful advancement of Cu(I)-catalyzed click chemistry in glycoscience and its applications as well as future scope in different streams of applied sciences.

New Peptide-Conjugated Chlorin-Type Photosensitizer Targeting Neuropilin-1 for Anti-Vascular Targeted Photodynamic Therapy

Photodynamic therapy (PDT) is a cancer treatment modality that requires three components, namely light, dioxygen and a photosensitizing agent. After light excitation, the photosensitizer (PS) in its excited state transfers its energy to oxygen, which leads to photooxidation reactions. In order to improve the selectivity of the treatment, research has focused on the design of PS covalently attached to a tumor-targeting moiety. In this paper, we describe the synthesis and the physico-chemical and photophysical properties of six new peptide-conjugated photosensitizers designed for targeting the neuropilin-1 (NRP-1) receptor. We chose a TPC (5-(4-carboxyphenyl)-10,15, 20-triphenyl chlorine as photosensitizer, coupled via three different spacers (aminohexanoic acid, 1-amino-3,6-dioxaoctanoic acid, and 1-amino-9-aza-3,6,12,15-tetraoxa-10-on-heptadecanoic acid) to two different peptides (DKPPR and TKPRR). The affinity towards the NRP-1 receptor of the conjugated chlorins was evaluated along with in vitro and in vivo stability levels. The tissue concentration of the TPC-conjugates in animal model shows good distribution, especially for the DKPPR conjugates. The novel peptide-PS conjugates proposed in this study were proven to have potential to be further developed as future NRP-1 targeting photodynamic therapy agent.

Click made porphyrin–corrole dyad: a system for photo-induced charge separation

The preparation of the first porphyrin–corrole dyad through click chemistry is described.

Huisgen-based conjugation of water-soluble porphyrins to deprotected sugars: towards mild strategies for the labelling of glycans

Fully deprotected alkynyl-functionalised mono- and oligosaccharides undergo CuAAC-based conjugation with water-soluble porphyrin azides in aqueous environments.

Carbohydrate-conjugated porphyrin dimers: synthesis and photobiological evaluation for a potential application in one-photon and two-photon photodynamic therapy

We report the synthesis of bioconjugated zinc porphyrin dimers 1a-e designed as photosensitizers for one-photon and two-photon excited photodynamic therapy. These macrocycles are substituted with carbohydrate units (glucose, mannose, lactose) in order to target tumor cells over-expressing lectin membrane receptors. Polarity, singlet oxygen production and in vitro photocytotoxicity are studied to determine their photodynamic therapy potentiality.

Tumor targeting in photodynamic therapy. From glycoconjugated photosensitizers to glycodendrimeric one. Concept, design and properties

In this paper, we discuss the evolution over the last 15 years in the Curie Institute of the concept, the development of the design and some properties of glycoconjugated photosensitizers with the aim to optimize the tumor targeting in photodynamic therapy. By this research, we have shown that specific interactions between a mannose-lectin and trimannosylglycodendrimeric porphyrins contributed to a larger extent than non-specific ones to the overall interaction of a glycosylated tetraarylporphyrin with a membrane. The studies of in vitro photocytotoxicity showed the relevance of the global geometry of the photosensitizer, the number and position of the linked glycopyranosyl groups on the chromophore and their lipophilicity. The two best compounds appeared to be porphyrins bearing three α-glycosyl groups on para-position of meso-phenyl via a flexible linker. Compound bearing α-manosyl moieties was evaluated successfully in two in vivo xenografted animal models of human retinoblastoma and colorectal cancers. Conversely, the presence on the chromophore of three sugars via a glycodendrimeric moiety induced a potential cluster effect, but decreased the in vitro photoefficiency despite a good affinity for a mannose-lectin.

mTHPC--a drug on its way from second to third generation photosensitizer?

5,10,15,20-Tetrakis(3-hydroxyphenyl)chlorin (mTHPC, Temoporfin) is a widely investigated second generation photosensitizer. Its initial use in solution form (Foscan®) is now complemented by nanoformulations (Fospeg®, Foslip®) and new chemical derivatives related to the basic hydroxyphenylporphyrin framework. Advances in formulation, chemical modifications and targeting strategies open the way for third generation photosensitizers and give an illustrative example for the developmental process of new photoactive drugs.