Photodynamic Activities of Porphyrin Derivative-Cyclodextrin Complexes by Photoirradiation

Photoacoustic Imaging Using Polysaccharide-Porphyrin Complexes by Photoirradiation at Long Wavelengths

Photoacoustic (PA) imaging is a novel biological imaging technique with superior depth resolution compared to fluorescence imaging. The efficacy of PA imaging depends on contrast agents that possess considerable absorbance at longer wavelengths, coupled with high permeability in biological tissue and minimal fluorescence, achieved through mitigating aggregation-caused quenching (ACQ) that attenuates PA intensity. Despite the successful transfer of porphyrin 2 featuring amino moieties from polysaccharides to liposomes, most of 2 incorporated within λ-carrageenan (CGN-2 complex) remained in CGN under acidic lysosomal conditions (pH 5.0). Consequently, the CGN-2 complex exhibited a strong PA signal under 680 nm photoirradiation in Colon26 cells owing to the ACQ of 2. Moreover, the PA intensity of the CGN-2 complex was further enhanced under 780 nm photoirradiation owing to the increased absorbance at 780 nm facilitated by the redshift of the Q-band at pH 5.0.

Applications of supramolecular assemblies in drug delivery and photodynamic therapy

One of the world's serious health challenges is cancer. Anti-cancer agents delivered to normal cells and tissues pose several problems and challenges. In this connection, photodynamic therapy (PDT) is a minimally invasive therapeutic technique used for selectively destroying malignant cells while sparing the normal tissues. Development in photosensitisers (PSs) and light sources have to be made for PDT as a first option treatment for patients. In the pursuit of developing new attractive molecules and their formulations for PDT, researchers are working on developing such type of PSs that perform better than those being currently used. For the widespread clinical utilization of PDT, effective PSs are of particular importance. Host-guest interactions based on nanographene assemblies such as functionalized hexa-cata-hexabenzocoronenes, hexa-peri-hexabenzocoronenes and coronene have attracted increasing attention owing to less complicated synthetic steps and purification processes (gel permeation chromatography) during fabrication. Noncovalent interactions provide easy and facile approaches for building supramolecular PSs and enable them to have sensitive and controllable photoactivities, which are important for maximizing photodynamic effects and minimizing side effects. Various versatile supramolecular assemblies based on cyclodextrins, cucurbiturils, calixarenes, porphyrins and pillararenes have been designed in order to make PDT an effective therapeutic technique for curing cancer and tumours. The supramolecular assemblies of porphyrins display efficient electron transfer and fluorescence for use in bioimaging and PDT. The multifunctionalization of supramolecular assemblies is used for designing biomedically active PSs, which are helpful in PDT. It is anticipated that the development of these functionalized supramolecular assemblies will provide more fascinating advances in PDT and will dramatically expand the potential and possibilities in cancer treatments.

"On-Off" Switching of Functional Guest Molecules via Exchange of Natural Product Solubilizing Agents

For the development of delivery systems, the solubilization of hydrophobic guest molecules in water is an important yet challenging task. This can be achieved by preparing stable aqueous solutions with a high concentration of guest molecules using a natural product as a solubilizing agent and a mechanochemical high-speed vibration milling apparatus as a solubilizing method. Various solubilizing agent-guest molecule complexes can be obtained via the exchange between solubilizing agents, which enables the "on-off" switching of the properties of functional guest molecules, such as fluorescence intensity, and photodynamic activity. In the exchange method, guest molecules can transfer into cell membranes such as lysosomes and exosomes. Therefore, the exchange method of the solubilizing agents not only creates novel solubilizing agent-guest molecule complexes but also is applied to drug delivery systems.

A supramolecular nanoplatform for imaging-guided phototherapies via hypoxia tumour microenvironment remodeling

Photodynamic therapy (PDT) has emerged as an invasive and promising antitumour treatment, however, the hypoxia in deep tumour tissues and the poor water-solubility of photosensitizers as bottlenecks greatly hinder PDT efficiency. Herein, a tumour microenvironment (TME) activated supramolecular nanoplatform consisting of the pillar[5]arene-based amphiphilic polymer POPD, the phototherapeutic agent Cy7-CN, respiratory medication atovaquone (ATO) and chemotherapeutic drug pyridinyl camptothecin (CPT-Py) was constructed for imaging-guided hypoxia-ameliorated phototherapies. Owing to host-guest interaction, the photochemical and photophysical properties of cyanine were improved exceedingly due to the suppression of π-π stacking. Triggered by the acidic microenvironment in tumour sites, the supramolecular nanoplatform would dissociate and release CPT-Py and ATO which inhibits mitochondria-associated oxidative phosphorylation (OXPHOS) and encourages more oxygen to be used in enhanced PDT. In vitro and in vivo studies verified that the rational combination of ATO-enhanced PDT and PTT overcame the disadvantages of single phototherapy and formed mutual promotion, and simultaneously sensitized chemotherapeutic drugs, which resulted in high tumour inhibition. It is hoped that the supramolecular nanoplatform could shed light on the development of phototherapeutic agents.

Bioresponsive and multifunctional cyclodextrin-based non-viral nanocomplexes in cancer therapy: Building foundations for gene and drug delivery, immunotherapy and bioimaging

The interest towards application of nanomaterials in field of cancer therapy is that the drawbacks of conventional therapies including chemoresistance, radio-resistance and lack of specific targeting of tumor cells can be solved by nanotechnology. Cyclodextrins (CDs) are amphiphilic cyclic oligosaccharides that can be present in three forms of α-, β- and γ-CDs, and they can be synthesized from natural sources. The application of CDs in cancer shows an increasing trend due to benefits of these nanocomplexes in improving solubility and bioavailability of current bioactives and therapeutics for cancer. CDs are widely utilized in delivery of drugs and genes in cancer therapy, and by targeted delivery of these therapeutics into target site, they improve anti-proliferative and anti-cancer potential. The blood circulation time and tumor site accumulation of therapeutics can be improved using CD-based nanostructures. More importantly, the stimuli-responsive types of CDs including pH-, redox- and light-sensitive types can accelerate release of bioactive compound at tumor site. Interestingly, the CDs are able to mediate photothermal and photodynamic impact in impairing tumorigenesis in cancer, enhancing cell death and improving response to chemotherapy. In improving the targeting ability of CDs, their surface functionalization with ligands has been conducted. Moreover, CDs can be modified with green products such as chitosan and fucoidan, and they can be embedded in green-based nanostructures to suppress tumorigenesis. The internalization of CDs into tumor cells can occur through endocytosis and this can be clethrin-, caveolae- or receptor-mediated endocytosis. Furthermore, CDs are promising candidates in bioimaging, cancer cell and organelle imaging as well as isolating tumor cells. The main benefits of using CDs in cancer therapy including sustained and low release of drugs and genes, targeted delivery, bioresponsive release of cargo, ease of surface functionalization and complexation with other nanostructures. The application of CDs in overcoming drug resistance requires more investigation.

Supramolecular Assemblies based on Polymeric Cyclodextrin Nanosponges and a Cationic Porphyrin with Antimicrobial Photodynamic Therapy Action

Within of the increasing requirement of alternative approaches to fight emerging infections, nano-photosensitisers (nanoPS) are currently designed with the aim to optimize the antimicrobial photodynamic (aPDT) efficacy. The utilize of less expensive nanocarriers prepared by simple and eco-friendly methodologies and commercial photosensitisers are highly desiderable. In this direction, here we propose a novel nanoassembly composed of water soluble anionic polyester β-CD nanosponges (β-CD-PYRO hereafter named βNS) and the cationic 5,10,15,20-tetrakis(1-methylpyridinium-4- yl)porphine (TMPyP). Nanoassemblies were prepared in ultrapure water by mixing PS and βNS, by exploiting their mutual electrostatic interaction, and characterized by various spectroscopic techniques such as UV/Vis, Steady-State and Time Resolved Fluorescence, Dynamic Light Scattering and ζ-potential. NanoPS produce appreciable amount of single oxygen similar to free porphyrin and a prolonged stability after 6 days of incubations in physiological conditions and following photoirradiation. Antimicrobial photodynamic action against fatal hospital-acquired infections such as P. aeruginosa and S. aureus was investigated by pointing out the ability of cationic porphyrin loaded- CD nanosponges to photo-kill bacterial cells at prolonged time of incubation and following irradiation (MBC₉₉ = 3.75 µM, light dose = 54.82 J/cm²).

Fluorescence Turn-on of Tetraphenylethylene Derivative by Transfer from Cyclodextrin to Liposomes, HeLa Cells, and E. coli

Herein, trimethyl-β-cyclodextrin (TMe-β-CDx) and γ-cyclodextrin (γ-CDx) could dissolve a tetraphenylethylene derivative (TPE-OH₄ ) in water through high-speed vibration milling. The fluorescence intensity of the TMe-β-CDx-TPE-OH₄ complex was much higher than that of the γ-CDx-TPE-OH₄ complex, as the rotation of the central C=C double bond of TPE-OH₄ after photoactivation was inhibited in a smaller TMe-β-CDx cavity in comparison with the γ-CDx cavity. In contrast, the fluorescence intensity of the γ-CDx-TPE-OH₄ complex was very weak; nevertheless, it increased after the addition of liposomes due to the transfer of TPE-OH₄ from the γ-CDx cavity to the lipid membrane as a "turn-on" phenomenon. Furthermore, to apply temperature sensor, it was demonstrated that the fluorescence intensity in the liposomes depended on the phase-transition temperature. By using the fluorescence turn-on phenomenon, TPE-OH₄ could detect the presence of HeLa cells and E. coli by fluorescence.

Cyclodextrin-Based Nanoplatforms for Tumor Phototherapy: An Update

Tumor phototherapies are light-mediated tumor treatment modalities, which usually refer to tumor photothermal therapy (PTT) and photodynamic therapy (PDT). Due to the outstanding spatial-temporal control over treatment through light irradiation, tumor phototherapies display extremely low side effects during treatment and are believed to be a tumor treatment method with a clinical translation potential. However, current tumor phototherapy nanoplatforms face obstacles, including light irradiation-induced skin burning, tumor hypoxia microenvironments, limited light penetration depth, et al. Therefore, one important research direction is developing a tumor phototherapy nanoplatform with multifunctionality and enhanced pharmacological effects to overcome the complexity of tumor treatment. On the other hand, cyclodextrins (CDs) are starch-originated circular oligosaccharides with negligible toxicity and have been used to form supermolecular nanostructures through a host–guest interaction between the inner cavity of CDs and functional biomolecules. In the past few years, numerous studies have focused on CD-based multifunctional tumor phototherapy nanoplatforms with an enhanced photoeffect, responsive morphological transformation, and elevated drug bioavailability. This review focuses on the preparation methods of CD-based tumor phototherapy nanoplatforms and their unique physiochemical properties for improving anti-tumor pharmacological efficacy.

Novel liposome-like assemblies composed of phospholipid-porphyrin conjugates with photothermal and photodynamic activities against bacterial biofilms

Phospholipid-Porphyrin (PL-Por) conjugates are unique building blocks that can self assemble into liposome-like structures with improved photophysical properties compared to their monomeric counterparts. The high packing density of porphyrin moieties enables these assemblies to exhibit high photothermal conversion efficiency as well as photodynamic activity. Thus, PL-Por conjugates assemblies can be used for photodynamic therapy (PDT) and photothermal therapy (PTT) applications against resistant bacteria and biofilms. In order to tune the PD/PT properties of such nanosystems, we developed six different supramolecular assemblies composed of newly synthesized PL-Por conjugates bearing either pheophorbide-a (Ph_xLPC) or pyropheophorbide-a (Pyr_xLPC) photosensitizers (PSs) for combined PDT/PTT against planktonic bacteria and their biofilms. In this study, the influence of the chemical structure of the phospholipid backbone as well as that of the PS on the photothermal conversion efficiency, the photodynamic activity and the stability of these assemblies in biological medium were determined. Then their antimicrobial efficiency was assessed on S. aureus and P. aeruginosa planktonic cultures and biofilms. The two studied systems show almost the same photothermal effect against planktonic cultures and biofilms of S. aureus and P. aeruginosa. However, Ph_xLPC vesicles exhibit superior photodynamic activity, making them the best combination for PTT/PDT. Such results highlight the higher potential of the photodynamic activity of PL-Por nanoassemblies compared to their photothermal conversion in combating bacterial infections.

Cyclodextrin-Activated Porphyrin Photosensitization for Boosting Self-Cleavable Drug Release

Supramolecular prodrugs that combine the merits of stimuli-responsiveness and targeting ability in a controllable manner have shown appealing prospects in disease diagnostics and therapeutics. Herein, we report that a new theranostic agent with the host-guest-binding-activated photosensitization has been fabricated by a binary supramolecular assembly consisting of the permethyl-β-cyclodextrin-grafted hyaluronic acid and a combretastatin A-4-appended porphyrin derivative. Illuminated by a red-light source, the production efficiency of singlet oxygen (¹O₂) pronouncedly increases by ∼60-fold once the porphyrin core is encapsulated by cyclodextrins. Consequently, the cell-selective fluorescence emission is dramatically enhanced, the microtubule-targeted drug is rapidly and completely released, and the ¹O₂-involved combinational treatment is simultaneously achieved both in vitro and in vivo. To be envisaged, this complexation-boosted light-activatable photosensitizing prodrug delivery system with improved photophysical performance and remarkable phototheranostic outcomes will make a significant contribution to the creation of more advanced stimulus-based biomaterials.

Effect of meso Positioned Substituents on the Stability and Photodynamic Activity of Lipid-Membrane-Incorporated Porphyrin Derivatives

Here, we prepared aqueous solutions of lipid-membrane incorporated tetraarylporphyrins and tetrapyridylporphyrin (LMIPors) by the injection method using dimethyl sulfoxide. The porphyrins with proton-donor groups at the meso position afforded stable aqueous solutions of LMIPors. However, although tetrakis(carboxyphenyl)porphyrin was scarcely incorporated in lipid membranes, it was soluble in water. Among these LMIPors, the photodynamic activity of tetrakis(hydroxyphenyl)porphyrin was higher than that of tetrakis(aminophenyl)porphyrin. This was attributed to the self-aggregation of a part of tetrakis(aminophenyl)porphyrin in the liposomes, which induced self-quenching and the consequent decrease of its photodynamic activity.

Unsymmetrical, monocarboxyalkyl meso-arylporphyrins in the photokilling of breast cancer cells using permethyl-β-cyclodextrin as sequestrant and cell uptake modulator

In the search for photosensitizers with chemical handles to facilitate their integration into complex drug delivery nanosystems, new, unsymmetrically substituted, water insoluble meso-tetraphenylporphyrin and meso-tetra(m-hydroxyphenyl)porphyrin derivatives bearing one carboxyalkyl side chain were synthesized. Permethyl-β-cyclodextrin (pMβCD) was their ideal monomerizing host and highly efficient shuttle to transfer them into water. New assembly modes of the extremely stable (K_binding > 10¹² M^-2) 2:1 complexes were identified. The complexes are photostable and do not disassemble in FBS-containing cell culture media for 24 h. Incubation of breast cancer MCF-7 cells with the complexes results in intense intracellular fluorescence, strongly enhanced in the endoplasmic reticulum (ER), high photokilling efficiency (~90%) and low dark toxicity. pMβCD stands out as a very capable molecular isolator of mono-carboxyalkyl-arylporphyrins that increases uptake and modulates their localization in the cells. The most efficient porphyrins are envisaged as suitable photosensitizers that can be linked to biocompatible drug carriers for photo- and chemo-therapy applications.

Photoinduced Electron Transfer in Encapsulated Heterocycles by Cavitands

Host-guest complexation of small heterocyclic (guest) and macrocyclic cavitands (hosts) organic molecules is still to date a very popular, inexpensive approach that bypasses the burdens of conventional covalent synthesis. Understanding the selection criteria of these chemicals is crucial to the design and potential applications of their supramolecular assemblies. This review surveys examples within the last 15 years (2005-2020) of supramolecular complexes in which the interacting photoinduced electron transfer (PET)-based chromophore and quencher fragments are commonly used in the market with reported CAS numbers. It appears from this survey that the supramolecular effects can be directed to specifically disrupt PET when the nonemissive macrocycles separately encapsulate the fluorescent acceptor or donor molecules, among other specific factors, such as when inducing conformational changes or pK_a shift of the donor. On the contrary, synergetic encapsulation of both donor and acceptor molecules, formation of ternary self-assembly at the rim or encapsulation of one component while grafting the other onto the macrocycle, among other specific factors such as the modulation of the excited-state structure of donor, will lead to the enhancement of PET process. In the event the donor or acceptor molecules have multitopic structures, the PET process can repeatedly be switched on and off. It is generally concluded that understanding the criteria for the combination of these available products for the purpose of manipulating their PET efficiency should pave the way for the facile alternative generation of new noncovalently bonded host-guest supramolecular assemblies with a more specific design tailored for more advanced, diverse and economic applications such as chemical sensing, molecular gates, drug delivery and biolabeling.

An Anti-inflammatory Fe3 O4 -Porphyrin Nanohybrid Capable of Apoptosis through Upregulation of p21 Kinase Inhibitor Having Immunoprotective Properties under Anticancer PDT Conditions

We report the influence of Fe₃ O₄ nanoparticles (NPs) on porphyrins in the development of photosensitizers (PSs) for efficient photodynamic therapy (PDT) and possible post-PDT responses for inflicting cancer cell death. Except for Au, most metal-based nanomaterials are unsuitable for clinical applications. The US Food and Drug Administration and other agencies have approved Feraheme and a few other iron oxide NPs for clinical use, paving the way for novel biocompatible immunoprotective superparamagnetic iron oxide nanohybrids to be developed as nanotherapeutics. A water-soluble nanohybrid, referred to here as E-NP, comprising superparamagnetic Fe₃ O₄ NPs functionalised with tripyridyl porphyrin PS was introduced through a rigid 4-carboxyphenyl linker. As a PDT agent, the efficacy of E-NP toward the AGS cancer cell line showed enhanced photosensitising ability as determined through in vitro photobiological assays. The cellular uptake of E-NPs by AGS cells led to apoptosis by upregulating ROS through cell-cycle arrest and loss of mitochondrial membrane potential. The subcellular localisation of the PSs in mitochondria stimulated apoptosis through upregulation of p21, a proliferation inhibitor capable of preventing tumour development. Under both PDT and non-PDT conditions, this nanohybrid can act as an anti-inflammatory agent by decreasing the production of NO and superoxide ions in murine macrophages, thus minimising collateral damage to healthy cells.

Probing the Interactions of Porphyrins with Macromolecules Using NMR Spectroscopy Techniques

Porphyrinic compounds are widespread in nature and play key roles in biological processes such as oxygen transport in blood, enzymatic redox reactions or photosynthesis. In addition, both naturally derived as well as synthetic porphyrinic compounds are extensively explored for biomedical and technical applications such as photodynamic therapy (PDT) or photovoltaic systems, respectively. Their unique electronic structures and photophysical properties make this class of compounds so interesting for the multiple functions encountered. It is therefore not surprising that optical methods are typically the prevalent analytical tool applied in characterization and processes involving porphyrinic compounds. However, a wealth of complementary information can be obtained from NMR spectroscopic techniques. Based on the advantage of providing structural and dynamic information with atomic resolution simultaneously, NMR spectroscopy is a powerful method for studying molecular interactions between porphyrinic compounds and macromolecules. Such interactions are of special interest in medical applications of porphyrinic photosensitizers that are mostly combined with macromolecular carrier systems. The macromolecular surrounding typically stabilizes the encapsulated drug and may also modify its physical properties. Moreover, the interaction with macromolecular physiological components needs to be explored to understand and control mechanisms of action and therapeutic efficacy. This review focuses on such non-covalent interactions of porphyrinic drugs with synthetic polymers as well as with biomolecules such as phospholipids or proteins. A brief introduction into various NMR spectroscopic techniques is given including chemical shift perturbation methods, NOE enhancement spectroscopy, relaxation time measurements and diffusion-ordered spectroscopy. How these NMR tools are used to address porphyrin-macromolecule interactions with respect to their function in biomedical applications is the central point of the current review.

Water Solubilization and Thermal Stimuli-Triggered Release of Porphyrin Derivatives Using Thermoresponsive Polysaccharide Hydroxypropyl Cellulose for Mitochondria-Targeted Photodynamic Therapy

With minimal invasiveness and spatiotemporal therapeutic effects, photodynamic therapy is one of the most elegant strategies for achieving effective tumor therapy. Herein, a facile preparation and thermal process-triggered release of water-soluble photosensitizer 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) has been developed using a thermoresponsive polysaccharide, hydroxypropyl cellulose. Current systems using hydroxypropyl cellulose enable manipulation of the loading capacity of THPP into a polymer matrix and the size of the complex by varying the temperature of the solution in preparation. Furthermore, current systems have enabled the release of THPP using a heating process, mimicking the surrounding of mitochondria, and have resulted in THPP potency as a mitochondria-targeted photodynamic therapy.

Cucurbit[10]uril-Encapsulated Cationic Porphyrins with Enhanced Fluorescence Emission and Photostability for Cell Imaging

Porphyrins are widely applied for imaging, diagnosis, and treatment of diseases because of their excellent photophysical properties. However, porphyrins easily tend to aggregate driven by hydrophobic interaction and π-π stacking in an aqueous medium, which causes fluorescence quenching of the porphyrins as well as limitation of cell uptake and intracellular accumulation. Herein, cucurbit[10]uril (CB[10]) was used to fully encapsulate cationic porphyrin (CPor) in the large cavity with strong binding affinity in aqueous solutions, and the CPor aggregates were efficient disassembled, companying remarkable enhancing its fluorescence intensity. The CB[10]-based host-guest complex provided excellent protection to CPor, resulting in less susceptibility to oxidation and imparting higher photostability to CPor for cell imaging. In addition, by complexation with CB[10], it was found that the fluorescence signals and photostability of CPor were also effectively improved in cells with different reactive oxygen species levels. It is highly anticipated that the large macrocyclic host cavity-triggered large-guest encapsulation strategy in this work will provide a convenient and efficient method for designing supramolecular porphyrin dyes, thus broadening the diagnosis and imaging application in cells and microorganisms.

Cancer photocytotoxicity and anti-inflammatory response of cis-A2B2 type meso-p-nitrophenyl and p-hydroxyphenyl porphyrin and its zinc(ii) complex: a synthetic alternative to the THPP synthon

In comparison with the popular synthetic synthon THPP, the cis-A₂B₂ type of porphyrin derivative and its zinc(ii) complex PN₂(OH)₂Zn offer more promising photochemical and photobiological outcomes.

Mechanism toward Turn-on of Polysaccharide-Porphyrin Complexes for Fluorescence Probes and Photosensitizers in Photodynamic Therapy in Living Cells

β-(1,3-1,6)-D-Glucan, λ-carrageenan, tamarind gum, and pullulan can dissolve various porphyrin derivatives via the formation of complexes in water using a high-speed vibration milling method. The aqueous solutions of the resulting complexes exhibit long-term stability. Despite the adverse effects of the self-quenching process, notable fluorescence and improved photodynamic activity of the polysaccharide-complexed porphyrin derivatives were observed in the presence of liposomes, micelles, cyclodextrins, and HeLa cells. It was noted that the type of porphyrins was more important than the type of polysaccharides present in the complex. Porphyrin self-aggregates were monodispersed in the lipid membranes of the liposomes and lysosomes. The polysaccharide-complexed porphyrin derivatives showed increased photodynamic activity toward HeLa cells under photoirradiation between 610 and 740 nm.

Improved water solubility and photodynamic activity of hydroxy-modified porphyrins by complexation with cyclodextrin

Porphyrin derivatives with hydroxyphenyl or dihydroxyphenyl moieties in the meso-position were able to dissolve in water by complexation with two trimethyl-β-cyclodextrins (TMe-β-CDxs) without further chemical modification of porphyrins or addition of dimethyl sulfoxide as a co-solvent. TMe-β-CDx-complexed tetra(hydroxyphenyl)porphyrins (THPPs) with phenols in meso-positions have a much higher photodynamic activity than TMe-β-CDx-complexed tetrakis(dihydroxyphenyl)porphyrins (TDHPPs) with dihydroxyphenyl in the meso-position. The main reason for the different photoactivity is due to the intracellular uptakes of these complexes. Thus phenols in meso-positions of porphyrin derivatives in the complexes were recognized by HeLa cell receptors. Furthermore, the photodynamic activity of TMe-β-CDx-complexed THPP was much higher than that of THPP injected as a dimethyl sulfoxide solution.

Cyclodextrin as a magic switch in covalent and non-covalent anticancer drug release systems

Cancer has been a threat to human health, so its treatment is a huge challenge to the present medical field. One of commonly used methods is the controlled release of anticancer drug to reduce the dose for patients, increase the stability of drug treatment and minimize side effects. Cyclodextrin is a kind of cyclic oligosaccharide produced by amylase hydrolysis. Because cyclodextrin contains a cavity structure and active hydroxyl groups, it has a positive effect on the study of the controlled release of anticancer drugs. This article reviews the controlled release of current anticancer drugs based on cyclodextrins as a "flexible switch", and discusses the classification of different types of release systems, highlighting their role in cancer treatment. Moreover, the opportunities and challenges of cyclodextrin as a magic switch in the controlled release of anticancer drugs are discussed.

Carbohydrates: Potential Sweet Tools Against Cancer

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Cancer, one of the most devastating degenerative diseases nowadays, is one of the main targets in Medicinal Chemistry and Pharmaceutical industry. Due to the significant increase in the incidence of cancer within world population, together with the complexity of such disease, featured with a multifactorial nature, access to new drugs targeting different biological targets connected to cancer is highly necessary.

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Among the vast arsenal of compounds exhibiting antitumor activities, this review will cover the use of carbohydrate derivatives as privileged scaffolds. Their hydrophilic nature, together with their capacity of establishing selective interactions with biological receptors located on cell surface, involved in cell-to-cell communication processes, has allowed the development of an ample number of new templates useful in cancer treatment.

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Their intrinsic water solubility has allowed their use as of pro-drug carriers for accessing more efficiently the pharmaceutical targets. The preparation of glycoconjugates in which the carbohydrate is tethered to a pharmacophore has also allowed a better permeation of the drug through cellular membranes, in which selective interactions with the carbohydrate motifs are involved. In this context, the design of multivalent structures (e.g. gold nanoparticles) has been demonstrated to enhance crucial interactions with biological receptors like lectins, glycoproteins that can be involved in cancer progression.

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Moreover, the modification of the carbohydrate structural motif, by incorporation of metal complexes, or by replacing their endocyclic oxygen, or carbon atoms with heteroatoms has led to new antitumor agents.

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Such diversity of sugar-based templates with relevant antitumor activity will be covered in this review.

Synthesis of highly water soluble tetrabenzoporphyrins and their application toward photodynamic therapy

Novel tetraaryl-(pyridinium-4-yl)-tetrabenzoporphyrins have been successfully synthesized via a Heck-based sequence reaction. These tetrabenzoporphyrins were substituted with eight pyridyl groups at the fused benzene rings. Methylation of the pyridyl groups with methyl iodide afforded highly water soluble tetrabenzoporphyrins carrying eight ionic groups. The extended [Formula: see text]-conjugation broadened and red-shifted the absorption band of these porphyrins to 650–750 nm. These cationic tetrabenzoporphyrins showed non-toxicity in the dark up to 100 uM. High phototoxicity with IC[Formula: see text] values lower than 18 [Formula: see text]M were obtained for these tetrabenzoporphyrins.

Host–guest interaction based supramolecular photodynamic therapy systems: a promising candidate in the battle against cancer

This article summarizes recent advances in the development of supramolecular photodynamic therapy based on host–guest interactions.

Porphyrinoid-Cyclodextrin Assemblies in Biomedical Research: An Update

Porphyrinoids, well-known cofactors in fundamental processes of life, have stimulated interest as synthetic models of natural systems and integral components of photodynamic therapy, but their utilization is compromised by self-aggregation in aqueous media. The capacity of cyclodextrins to include hydrophobic molecules in their cavity provides porphyrinoids with a protective environment against oxidation and the ability to disperse efficiently in biological fluids. Moreover, engineered cyclodextrin-porphyrinoid assemblies enhance the photodynamic abilities of porphyrinoids, can carry chemotherapeutics for synergistic modalities, and can be enriched with functions including cell recognition, tissue penetration, and imaging. This Perspective includes synthetic porphyrinoid-cyclodextrin models of proteins participating in fundamental processes, such as enzymatic catalysis, respiration, and electron transfer. In addition, since porphyrinoid-cyclodextrin systems comprise third generation photosensitizers, recent developments for their utilization in photomedicine, that is, multimodal therapy for cancer (e.g., PDT, PTT) and antimicrobial treatment, and eventually in biocompatible therapeutic or diagnostic platforms for next-generation nanomedicine and theranostics are discussed.

Porphyrinoid-based photosensitizers for diagnostic and therapeutic applications: An update

Porphyrin-based molecules are actively studied as dual function theranostics: fluorescence-based imaging for diagnostics and fluorescence-guided therapeutic treatment of cancers. The intrinsic fluorescent and photodynamic properties of the bimodal molecules allows for these theranostic approaches. Several porphyrinoids bearing both hydrophilic and/or hydrophobic units at their periphery have been developed for the aforementioned applications, but better tumor selectivity and high efficacy to destroy tumor cells is always a key setback for their use. Another issue related to their effective clinical use is that, most of these chromophores form aggregates under physiological conditions. Nanomaterials that are known to possess incredible properties that cannot be achieved from their bulk systems can serve as carriers for these chromophores. Porphyrinoids, when conjugated with nanomaterials, can be enabled to perform as multifunctional nanomedicine devices. The integrated properties of these porphyrinoid-nanomaterial conjugated systems make them useful for selective drug delivery, theranostic capabilities, and multimodal bioimaging. This review highlights the use of porphyrins, chlorins, bacteriochlorins, phthalocyanines and naphthalocyanines as well as their multifunctional nanodevices in various biomedical theranostic platforms.

High photodynamic activities of water-soluble inclusion complexes of 5,15-diazaporphyrins in cyclodextrin

Inclusion complexes of 5,15-diazaporphyrin derivatives in trimethyl-β-cyclodextrin exhibited high photodynamic activity under visible-light irradiation at wavelengths greater than 620 nm.

Turn-on fluorescence and photodynamic activity of β-(1,3-1,6)-d-glucan-complexed porphyrin derivatives inside HeLa cells

β-1,3-Glucan-complexed tetra(aminophenyl)porphyrin changed from ‘off-state’ to ‘on-state’ with respect of fluorescence and showed photodynamic activity by intracellular uptake.

Stabilisation of lipid membrane-incorporated porphyrin derivative aqueous solutions and their photodynamic activities

A porphyrin derivative which exists on the hydrophilic surface of the liposomes showed high photodynamic activity.

Design and synthesis of a 4-aminoquinoline-based molecular tweezer that recognizes protoporphyrin IX and iron(iii) protoporphyrin IX and its application as a supramolecular photosensitizer

We report on the design and synthesis of a new type of 4-aminoquinoline-based molecular tweezer 1 which forms a stable host-guest complex with protoporphyrin IX (PPIX) via multiple interactions in a DMSO and HEPES buffer (pH 7.4) mixed solvent system. The binding constant for the 1 : 1 complex (K 11) between 1 and PPIX is determined to be 4 × 106 M-1. Furthermore, 1 also forms a more stable complex with iron(iii) protoporphyrin IX (Fe(iii)PPIX), the K 11 value for which is one order of magnitude greater than that for PPIX, indicating that 1 could be used as a recognition unit of a synthetic heme sensor. On the other hand, the formation of the stable PPIX·1 complex (supramolecular photosensitizer) prompted us to apply it to photodynamic therapy (PDT). Cell staining experiments using the supramolecular photosensitizer and evaluations of its photocytotoxicity indicate that the PDT activity of PPIX is improved as the result of the formation of a complex with 1.

Use of Cyclodextrins in Anticancer Photodynamic Therapy Treatment

Photodynamic therapy (PDT) is mainly used to destroy cancerous cells; it combines the action of three components: a photoactivatable molecule or photosensitizer (PS), the light of an appropriate wavelength, and naturally occurring molecular oxygen. After light excitation of the PS, the excited PS then reacts with molecular oxygen to produce reactive oxygen species (ROS), leading to cellular damage. One of the drawbacks of PSs is their lack of solubility in water and body tissue fluids, thereby causing low bioavailability, drug-delivery efficiency, therapeutic efficacy, and ROS production. To improve the water-solubility and/or drug delivery of PSs, using cyclodextrins (CDs) is an interesting strategy. This review describes the in vitro or/and in vivo use of natural and derived CDs to improve antitumoral PDT efficiency in aqueous media. To achieve these goals, three types of binding modes of PSs with CDs are developed: non-covalent CD⁻PS inclusion complexes, covalent CD⁻PS conjugates, and CD⁻PS nanoassemblies. This review is divided into three parts: (1) non-covalent CD-PS inclusion complexes, covalent CD⁻PS conjugates, and CD⁻PS nanoassemblies, (2) incorporating CD⁻PS systems into hybrid nanoparticles (NPs) using up-converting or other types of NPs, and (3) CDs with fullerenes as PSs.

Asymmetric Cationic Porphyrin as a New G-Quadruplex Probe with Wash-Free Cancer-Targeted Imaging Ability Under Acidic Microenvironments

Porphyrins are promising candidates for nucleic acid G-quadruplex-specific optical recognition. We previously demonstrated that G-quadruplex recognition specificity of porphyrins could be improved by introducing bulky side arm substituents, but the enhanced protonation tendency limits their applications in some cases, such as under acidic conditions. Here, we demonstrated that the protonation tendency of porphyrin derivatives could be efficiently overcome by increasing molecular asymmetry. To validate this, an asymmetric, water-soluble, cationic porphyrin FA-TMPipEOPP (5-{4-[2-[[(2 E)-3-[3-methoxy-4-[2-(1-methyl-1-piperidinyl)ethoxy]phenyl]-1-oxo-2-propenyl]oxy]ethoxy]phenyl},10,15,20-tri{4-[2-(1-methyl-1-piperidinyl)ethoxy]-phenyl}porphyrin) was synthesized by introducing a ferulic acid (FA) unit at one side arm, and its structure was well-characterized. Unlike its symmetric counterpart TMPipEOPP that has a tendency to protonate under acidic conditions, FA-TMPipEOPP remained in the unprotonated monomeric form under the pH range of 2.0-8.0. Correspondingly, FA-TMPipEOPP showed better G-quadruplex recognition specificity than TMPipEOPP and thus might be used as a specific optical probe for colorimetric and fluorescent recognition of G-quadruplexes under acidic conditions. The feasibility was demonstrated by two proof-of-concept studies: probing structural competition between G-quadruplexes and duplexes and label-free and wash-free cancer cell-targeted bioimaging under an acidic tumor microenvironment. As G-quadruplex optical probes, FA-TMPipEOPP works well under acidic conditions, whereas TMPipEOPP works well under neutral conditions. This finding provides useful information for G-quadruplex probe research. That is, porphyrin-based G-quadruplex probes suitable for different pH conditions might be obtained by adjusting the molecular symmetry.

Improving the carrier stability and drug loading of unimolecular micelle-based nanotherapeutics for acid-activated drug delivery and enhanced antitumor therapy

Nanomedicines based on unimolecular micelles (UMs) have shown unique advantages such as high micellar stability, programmed cargo delivery and enhanced therapeutic efficiency.