Current status of liposomal porphyrinoid photosensitizers

Functional nanomaterials as photosensitizers or delivery systems for antibacterial photodynamic therapy

Bacterial infection is a global health problem that closely related to various diseases threatening human life. Although antibiotic therapy has been the mainstream treatment method for various bacterial infectious diseases for decades, the increasing emergence of bacterial drug resistance has brought enormous challenges to the application of antibiotics. Therefore, developing novel antibacterial strategies is of great importance. By producing reactive oxygen species (ROS) with photosensitizers (PSs) under light irradiation, antibacterial photodynamic therapy (aPDT) has emerged as a non-invasive and promising approach for treating bacterial infections without causing drug resistance. However, the insufficient therapeutic penetration, poor hydrophilicity, and poor biocompatibility of traditional PSs greatly limit the efficacy of aPDT. Recently, studies have found that nanomaterials with characteristics of favorable photocatalytic activity, surface plasmonic resonance, easy modification, and high drug loading capacity can improve the therapeutic efficacy of aPDT. In this review, we aim to provide a comprehensive understanding of the mechanism of nanomaterials-mediated aPDT and summarize the representative nanomaterials in aPDT, either as PSs or carriers for PSs. In addition, the combination of advanced nanomaterials-mediated aPDT with other therapies, including targeted therapy, gas therapy, and multidrug resistance (MDR) therapy, is reviewed. Also, the concerns and possible solutions of nanomaterials-based aPDT are discussed. Overall, this review may provide theoretical basis and inspiration for the development of nanomaterials-based aPDT.

Advances in liposomes loaded with photoresponse materials for cancer therapy

Cancer treatment is presently a significant challenge in the medical domain, wherein the primary modalities of intervention include chemotherapy, radiation therapy and surgery. However, these therapeutic modalities carry side effects. Photothermal therapy (PTT) and photodynamic therapy (PDT) have emerged as promising modalities for the treatment of tumors in recent years. Phototherapy is a therapeutic approach that involves the exposure of materials to specific wavelengths of light, which can subsequently be converted into either heat or Reactive Oxygen Species (ROS) to effectively eradicate cancer cells. Due to the hydrophobicity and lack of targeting of many photoresponsive materials, the use of nano-carriers for their transportation has been extensively explored. Among these nanocarriers, liposomes have been identified as an effective drug delivery system due to their controllability and availability in the biomedical field. By binding photoresponsive materials to liposomes, it is possible to reduce the cytotoxicity of the material and regulate drug release and accumulation at the tumor site. This article provides a comprehensive review of the progress made in cancer therapy using photoresponsive materials loaded onto liposomes. Additionally, the article discusses the potential synergistic treatment through the combination of phototherapy with chemo/immuno/gene therapy using liposomes.

Polymyxin B-targeted liposomal photosensitizer cures MDR A. baumannii burn infections and accelerates wound healing via M1/M2 macrophage polarization

Multidrug-resistant (MDR) Acinetobacter baumannii infections pose a significant challenge in burn wound management, necessitating the development of innovative therapeutic strategies. In this work, we introduced a novel polymyxin B (PMB)-targeted liposomal photosensitizer, HMME@Lipo-PMB, for precise and potent antimicrobial photodynamic therapy (aPDT) against burn infections induced by MDR A. baumanni. HMME@Lipo-PMB-mediated aPDT exhibited enhanced antibacterial efficacy by specifically targeting and disrupting bacterial cell membranes, and generating increased intracellular ROS. Remarkably, even at low concentrations, this targeted approach significantly reduced bacterial viability in vitro and completely eradicated burn infections induced by MDR A. baumannii in vivo. Additionally, HMME@Lipo-PMB-mediated aPDT facilitated burn infection wound healing by modulating M1/M2 macrophage polarization. It also effectively promoted acute inflammation in the early stage, while attenuated chronic inflammation in the later stage of wound healing. This dynamic modulation promoted the formation of granulation tissue, angiogenesis, and collagen regeneration. These findings demonstrate the tremendous potential of HMME@Lipo-PMB-mediated aPDT as a promising alternative for the treatment of burn infections caused by MDR A. baumannii.

Liposomes loaded with dual clinical photosensitizers for enhanced photodynamic therapy of cervical cancer

Photodynamic therapy (PDT) has become a potential anti-cancer strategy owing to its negligible invasiveness, low toxicity, and high selectivity. The photosensitizer (PS) plays an indispensable role in PDT. Herein, a novel type of PS (Ce6-MB@Lips) which can be excited by a near-infrared (NIR) laser was designed and synthesized. Methylene blue (MB) and Chlorin e6 (Ce6), two organic dyes approved by the Food and Drug Administration (FDA), were used to prepare Ce6-MB@Lips by thin-film dispersion method, which improve the water solubility of Ce6 and reduce the cytotoxicity of MB. The Ce6-MB@Lips were shown to have a spherical nanostructure with an average particle size of 160.3 nm and excellent water solubility. Then the optical properties of Ce6-MB@Lips were further studied. Ce6-MB@Lips showed absorption peaks at 413 nm/670 nm and fluorescence peak at 697 nm. Compared with Ce6@Lips and MB@Lips, Ce6-MB@Lips showed better stability, stronger fluorescence intensity, and higher singlet oxygen (1O2) generation ability. Cell experimental analysis exhibited that the stable Ce6-MB@Lips showed low cytotoxicity, high phototoxicity and high reactive oxygen species (ROS) production capacity. After effective cell internalization, the prepared Ce6-MB@Lips showed excellent ability to promote tumor cell apoptosis in vitro. The Ce6-MB@Lips could be a promising candidate for PDT of cervical cancer.

Secure transplantation by tissue purging using photodynamic therapy to eradicate malignant cells

The field of photodynamic therapy (PDT) for treating various malignant neoplasms has been given researchers' attention due to its ability to be a selective and minimally invasive cancer therapy strategy. The possibility of tumor cell infection and hence high recurrence rates in cancer patients tends to restrict autologous transplantation. So, the photodynamic tissue purging process, which consists of selective photoinactivation of the malignant cells in the graft, is defined as a compromising strategy to purify contaminated tissues before transplantation. In this strategy, the direct malignant cells' death results from the reactive oxygen species (ROS) generation through the activation of a photosensitizer (PS) by light exposure in the presence of oxygen. Since new PS generations can effectively penetrate the tissue, PDT could be an ideal ex vivo tissue purging protocol that eradicates cancer cells derived from various malignancies. The challenge is that the applied pharmacologic ex vivo tissue purging should efficiently induce tumor cells with minor influence on normal tissue cells. This review aims to provide an overview of the current status of the most effective PDT strategies and PS development concerning their potential application in ex vivo purging before hematopoietic stem cell or ovarian tissue transplantation.

Zinc(II), Palladium(II), and Metal-Free Phthalocyanines Bearing Nipagin-Functionalized Substituents against Candida auris and Selected Multidrug-Resistant Microbes

Due to the rapidly increasing problem of antibiotic resistance in recent years, the use of phthalocyanines as photosensitizers with their superior properties in photodynamic antimicrobial therapy (PACT) applications has become important. In this study, magnesium(II) 1,4,8,11,15,18,22,25-octakis(4-[4-butoxycarbonylphenoxy]butyloxy)phthalocyanine was used in the demetalation reaction in trifluoroacetic acid, and subsequently subjected to metalation reaction in dimethylformamide with zinc(II) acetate and bis(benzonitrile)palladium(II) chloride towards zinc(II) and palladium(II) derivatives. Three phthalocyanines, including a demetalated one as well as two metalated, in the core with zinc(II) and palladium(II) were characterized using 1D and 2D NMR spectroscopy and mass spectrometry. In addition, all macrocycles were subjected to absorption and emission studies as well as photostability tests. In a photochemical study, zinc(II) and palladium(II) phthalocyanine complexes appeared to be efficient singlet oxygen generators. There were noted quantum yields of singlet oxygen generation for zinc(II) phthalocyanine derivative in DMF and DMSO at 0.55 and 0.72, whereas for palladium(II) complex at 0.73 and 0.77, respectively. Liposomal formulations of phthalocyanine derivatives were prepared, and their activity was evaluated against a broad spectrum of antibiotic-resistant microorganisms, such as methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (ESBL+), Candida albicans resistant to fluconazole, C. auris, and against dermatophytes. Phthalocyanine palladium(II) complex showed the highest bactericidal activity against all antibiotic-resistant microorganisms, including reducing C. auris growth at 3.54 log.

Zinc(II) Sulfanyltribenzoporphyrazines with Bulky Peripheral Substituents—Synthesis, Photophysical Characterization, and Potential Photocytotoxicity

The study’s aim was to synthesize new unsymmetrical sulfanyl zinc(II) porphyrazines and subject them to physicochemical and electrochemical characterization and also an initial acute toxicity assessment. The procedure was initiated from a commercially available dimercaptomaleonitrile disodium salt and o-phthalonitrile using Linstead’s macrocyclization reaction conditions, which led to magnesium(II) tribenzoporphyrazine with 4-(3,5-dibutoxycarbonylphenoxy)butylthio substituents. The obtained macrocycle was demetallated with trifluoroacetic acid and subsequently remetallated with zinc(II) acetate toward the zinc(II) porphyrazine derivative. The zinc(II) tribenzoporphyrazine with 4-(3,5-dibutoxycarbonylphenoxy)butylthio substituents was then subjected to the reduction reaction with LiAlH4, yielding zinc(II) tribenzoporphyrazine with 4-[3,5-di(hydroxymethyl)phenoxy]butylthio substituents. The new zinc(II) tribenzoporphyrazines were characterized by UV-Vis spectroscopy, various NMR techniques (1HNMR, 13CNMR, 1H-1H COSY, 1H-13C HSQC, and 1H-13C HMBC), and mass spectrometry. In the UV-Vis spectra, both macrocycles revealed characteristic Soret and Q-bands, whose positions were dependent on the solvent used for the measurements. Zinc(II) tribenzoporphyrazines were studied using electrochemical and photochemical methods, including the singlet oxygen generation assessment. Both zinc(II) porphyrazines revealed high singlet oxygen generation quantum yield values of up to 0.59 in DMSO, which indicates their potential photosensitizing potential for photodynamic therapy. In addition, new derivatives were subjected to a Microtox® bioluminescence assay.

Porphyrins and Phthalocyanines on Solid-State Mesoporous Matrices as Catalysts in Oxidation Reactions

The review presents recent examples of heterogenic catalysts based on porphyrins and phthalocyanines loaded on mesoporous materials, such as MCM-41, SBA-15, MCM-48, SBA-16 or Al-MCM-41. Heterogenic approach to catalysis eases recovery, reuse and prevent macrocycle aggregation. In this application, mesoporous silica is a promising candidate for anchoring macrocycle and obtaining a new catalyst. Introduction of porphyrin or phthalocyanine into the mesoporous material may be performed through adsorption of the macrocycle, or by its in situ formation—by reaction of substrates introduced to the pores of the catalytic material. Catalytic reactions studied are oxidation processes, focused on alkane, alkene or arene as substrates. The products obtained are usually epoxides, alcohols, ketones, aldehydes or acids. The greatest interest lies in oxidation of cyclohexane and cyclohexene, as a source of adypic acid and derivatives. Some of the reactions may be viewed as biomimetic processes, resembling processes that occur in vivo and are catalyzed by cytochrome P450 enzyme family.

A Review of Liposomes as a Drug Delivery System: Current Status of Approved Products, Regulatory Environments, and Future Perspectives

Liposomes have been considered promising and versatile drug vesicles. Compared with traditional drug delivery systems, liposomes exhibit better properties, including site-targeting, sustained or controlled release, protection of drugs from degradation and clearance, superior therapeutic effects, and lower toxic side effects. Given these merits, several liposomal drug products have been successfully approved and used in clinics over the last couple of decades. In this review, the liposomal drug products approved by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) are discussed. Based on the published approval package in the FDA and European public assessment report (EPAR) in EMA, the critical chemistry information and mature pharmaceutical technologies applied in the marketed liposomal products, including the lipid excipient, manufacturing methods, nanosizing technique, drug loading methods, as well as critical quality attributions (CQAs) of products, are introduced. Additionally, the current regulatory guidance and future perspectives related to liposomal products are summarized. This knowledge can be used for research and development of the liposomal drug candidates under various pipelines, including the laboratory bench, pilot plant, and commercial manufacturing.

Photodynamic cancer therapy using liposomes as an advanced vesicular photosensitizer delivery system

The multidisciplinary field of photodynamic therapy (PDT) is a combination of photochemistry and photophysics sciences, which has shown tremendous potential for cancer therapy application. PDT employs a photosensitizing agent (PS) and light to form cytotoxic reactive oxygen species and subsequently oxidize light-exposed tissue. Despite numerous advantages of PDT and enormous progress in this field, common PSs are still far from ideal treatment because of their poor permeability, non-specific phototoxicity, side effects, hydrophobicity, weak bioavailability, and tendency to self-aggregation. To circumvent these limitations, PS can be encapsulated in liposomes, an advanced drug delivery system that has demonstrated the ability to enhance drug permeability into biological membranes and loading both hydrophobic and lipophilic agents. Moreover, liposomes can also be coated by targeting agents to improve delivery efficiency. The present review aims to summarize the principles of PDT, various PS generations, PS-loaded nanoparticles, liposomes, and their impact on PDT, then discuss recent photodynamic cancer therapy strategies using liposomes as PS-loaded vectors, and highlight future possibilities and perspectives.

Photosensitizers Mediated Photodynamic Inactivation against Fungi

Superficial and systemic fungal infections are essential problems for the modern health care system. One of the challenges is the growing resistance of fungi to classic antifungals and the constantly increasing cost of therapy. These factors force the scientific world to intensify the search for alternative and more effective methods of treatment. This paper presents an overview of new fungal inactivation methods using Photodynamic Antimicrobial Chemotherapy (PACT). The results of research on compounds from the groups of phenothiazines, xanthanes, porphyrins, chlorins, porphyrazines, and phthalocyanines are presented. An intensive search for a photosensitizer with excellent properties is currently underway. The formulation based on the existing ones is also developed by combining them with nanoparticles and common antifungal therapy. Numerous studies indicate that fungi do not form any specific defense mechanism against PACT, which deems it a promising therapeutic alternative.

Application of Asymmetrical Flow Field-Flow Fractionation for Characterizing the Size and Drug Release Kinetics of Theranostic Lipid Nanovesicles

Liposome size and in vitro release of the active substance belong to critical quality attributes of liposomal carriers. Here, we apply asymmetric flow field-flow fractionation (AF4) to characterize theranostic liposomes prepared by thin lipid film hydration/extrusion or microfluidics. The vesicles' size was derived from multi-angle laser light scattering following fractionation (AF4) and compared to sizes derived from dynamic light scattering measurements. Additionally, we adapted a previously developed AF4 method to study zinc phthalocyanine (ZnPc) release/transfer from theranostic liposomes. To this end, theranostic liposomes were incubated with large acceptor liposomes serving as a sink (mimicking biological sinks) and were subsequently separated by AF4. During incubation, ZnPc was transferred from donor to acceptor fraction until reaching equilibrium. The process followed first-order kinetics with half-lives between 119.5-277.3 min, depending on the formulation. The release mechanism was postulated to represent a combination of Fickian diffusion and liposome relaxation. The rate constant of the transfer was proportional to the liposome size and inversely proportional to the ZnPc/POPC molar ratio. Our results confirm the usefulness of AF4 based method to study in vitro release/transfer of lipophilic payload, which may be useful to estimate the unwanted loss of drug from the liposomal carrier in vivo.

Fluorescent Carbon Dot-Curcumin Nanocomposites for Remarkable Antibacterial Activity with Synergistic Photodynamic and Photothermal Abilities

Photosensitizer (PS)-mediated photodynamic therapy (PDT) has attracted more and more attention as an alternative to traditional antibiotic therapy. Nevertheless, the limitations of traditional photosensitizers seriously hinder their practical application, as a result, the methods to improve the antibacterial properties of traditional photosensitizers have become a hot topic in the field of photomedicine. Herein, a compound nano-PS system has been constructed with synergistic photodynamic and photothermal (PTT) antibacterial effects, triggered by a dual-wavelength illumination. Fluorescent carbon dots (CDs) were synthesized and employed as carriers for the delivery of curcumin (Cur) to obtain CDs/Cur. Upon combined near-infrared and 405 nm visible dual-wavelength irradiation, CDs/Cur could simultaneously generate ROS and a moderate temperature increase, triggering synergistic antibacterial effects against both Gram-positive and Gram-negative bacteria. The results of scanning electron microscopy and fluorescence confocal imaging showed that the combined effect of CDs/Cur with PDT and PTT caused more serious damage to the cell membrane. In addition, CDs/Cur exhibited low cytotoxicity and negligible hemolytic activity, showing great biocompatibility. Therefore, the construction of CDs/Cur by employing CDs as photosensitizer delivery carriers provides a strategy for the improvement of the antibacterial effect of the photosensitizer and the design of next-generation antibacterial agents in photomedicine.

Micro- and Nano-Based Transdermal Delivery Systems of Photosensitizing Drugs for the Treatment of Cutaneous Malignancies

Photodynamic therapy is one of the more unique cancer treatment options available in today’s arsenal against this devastating disease. It has historically been explored in cutaneous lesions due to the possibility of focal/specific effects and minimization of adverse events. Advances in drug delivery have mostly been based on biomaterials, such as liposomal and hybrid lipoidal vesicles, nanoemulsions, microneedling, and laser-assisted photosensitizer delivery systems. This review summarizes the most promising approaches to enhancing the photosensitizers’ transdermal delivery efficacy for the photodynamic treatment for cutaneous pre-cancerous lesions and skin cancers. Additionally, discussions on strategies and advantages in these approaches, as well as summarized challenges, perspectives, and translational potential for future applications, will be discussed.

Multi-Functional Liposome: A Powerful Theranostic Nano-Platform Enhancing Photodynamic Therapy

Although photodynamic therapy (PDT) has promising advantages in almost non-invasion, low drug resistance, and low dark toxicity, it still suffers from limitations in the lipophilic nature of most photosensitizers (PSs), short half-life of PS in plasma, poor tissue penetration, and low tumor specificity. To overcome these limitations and enhance PDT, liposomes, as excellent multi-functional nano-carriers for drug delivery, have been extensively studied in multi-functional theranostics, including liposomal PS, targeted drug delivery, controllable drug release, image-guided therapy, and combined therapy. This review provides researchers with a useful reference in liposome-based drug delivery.

Smart Stimuli-Responsive and Mitochondria Targeting Delivery in Cancer Therapy

Dysfunction in the mitochondria (Mc) contributes to tumor progression. It is a major challenge to deliver therapeutic agents specifically to the Mc for precise treatment. Smart drug delivery systems are based on stimuli-responsiveness and active targeting. Here, we give a whole list of documented pathways to achieve smart stimuli-responsive (St-) and Mc-targeted DDSs (St-Mc-DDSs) by combining St and Mc targeting strategies. We present the formulations, targeting characteristics of St-Mc-DDSs and clarify their anti-cancer mechanisms as well as improvement in efficacy and safety. St-Mc-DDSs usually not only have Mc-targeting groups, molecules (lipophilic cations, peptides, and aptamers) or materials but also sense the surrounding environment and correspondingly respond to internal biostimulators such as pH, redox changes, enzyme and glucose, and/or externally applied triggers such as light, magnet, temperature and ultrasound. St-Mc-DDSs exquisitely control the action site, increase therapeutic efficacy and decrease side effects of the drug. We summarize the clinical research progress and propose suggestions for follow-up research. St-Mc-DDSs may be an innovative and sensitive precision medicine for cancer treatment.

Co-encapsulation of sodium diethyldithiocarbamate (DETC) and zinc phthalocyanine (ZnPc) in liposomes promotes increases phototoxic activity against (MDA-MB 231) human breast cancer cells

There has been considerable interest in the development of novel photosensitisers for photodynamic therapy (PDT). The use of liposomes as drug delivery systems containing simultaneously two or more drugs is an attractive idea to create a new platform for PDT application. Therefore, the aim of this study was to evaluate the synergistic effect of diethyldithiocarbamate (DETC) and zinc phthalocyanine (PDT) co-encapsulated in liposomes. The reverse-phase evaporation method resulted in the successful encapsulation of DETC and ZnPc in liposomes, with encapsulation efficiencies above 85 %, mean size of 308 nm, and zeta potential of - 36 mV. The co-encapsulation decreased the cytotoxic effects in mouse embryo fibroblast (NIH3T3) cells and inhibited damage to human erythrocytes compared to free DETC + ZnPc. In addition, both the free drugs and co-encapsulated ones promoted more pronounced phototoxic effects on human breast cancer cells (MDA-MB231) compared to treatment with ZnPc alone. This synergistic effect was determined by DETC-induced decreases in the antioxidant enzyme activity of superoxide dismutase (SOD) and glutathione (GSH).

Conjugated Photosensitizers for Imaging and PDT in Cancer Research

Early cancer detection and perfect understanding of the disease are imperative toward efficient treatments. It is straightforward that, for choosing a specific cancer treatment methodology, diagnostic agents undertake a critical role. Imaging is an extremely intriguing tool since it assumes a follow up to treatments to survey the accomplishment of the treatment and to recognize any conceivable repeating injuries. It also permits analysis of the disease, as well as to pursue treatment and monitor the possible changes that happen on the tumor. Likewise, it allows screening the adequacy of treatment and visualizing the state of the tumor. Additionally, when the treatment is finished, observing the patient is imperative to evaluate the treatment methodology and adjust the treatment if necessary. The goal of this review is to present an overview of conjugated photosensitizers for imaging and therapy.

Photocytotoxicity of liposomal zinc phthalocyanine in oral squamous cell carcinoma and pharyngeal carcinoma cells

Aim: Photodynamic therapy utilizes a light-sensitive molecule that produces reactive oxygen species following irradiation. Photodynamic activities of free Zn phthalocyanine (ZnPc) and its liposomal formulations on human oral squamous cell carcinoma and pharyngeal carcinoma cells were assessed. Materials & methods: ZnPc was incorporated in extruded and nonextruded liposomes composed of palmitoyloleoylphosphatidylglycerol (POPG):palmitoyloleoylphosphatidylcholine (POPC) or POPG:dioleoylphosphatidylethanolamine liposomes and incubated with CAL 27 or FaDu cells. Cell viability was assessed following illumination and further incubation. Results: ZnPc incorporated in extruded POPG:POPC liposomes caused extensive cytotoxicity, while ZnPc in extruded or nonextruded POPG:dioleoylphosphatidylethanolamine liposomes or in multilamellar POPG:POPC liposomes were not effective. Conclusion: Extruded POPG:POPC liposomes are a useful delivery vehicle for ZnPc in photodynamic therapy of oral and pharyngeal cancers.

Photo-physicochemical properties of water-soluble non-aggregated indium(III) phthalocyanines

Phthalocyanines have interesting optoelectronic properties but typically suffer from aggregation in aqueous solution, which can limit their applicability, especially in photodynamic therapy. In this study, indium(III) phthalocyanine peripherally substituted with eight triazolyl-containing phenoxy groups (InOAc) and its water-soluble analogue (Q-InOAc) were synthesised and structurally characterised. Heavy metal effects, exerted by the central indium ion, on the photosensitising and photophysical properties (singlet oxygen quantum yield, singlet state lifetime and quantum yield, and triplet state lifetime) were investigated in both DMF and D₂O. Highly efficient generation of the triplet excited state (T1), induced by the incorporation of a large atom, enhanced singlet oxygen formation, as revealed by both chemical and physical methods. Correspondingly, the singlet oxygen quantum yield (Φ_Δ) of Q-InOAc was 0.603 in DMF and 0.433 in D₂O. These values are higher than those previously reported for the corresponding metal-free, Mg-based, and Zn-based water-soluble phthalocyanines (HH, Mg, and Zn). Consequently, Q-InOAc is expected to be an excellent photosensitiser for photodynamic therapy.

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.

Liposomal formulations of photosensitizers

Photodynamic therapy (PDT) is a clinical ablation modality to treat cancers and other diseases. PDT involves administration of a photosensitizer, followed by irradiation of target tissue with light. As many photosensitizers are small and hydrophobic, solubilization approaches and nanoscale delivery vehicles have been extensively explored. Liposomes and lipid-based formulations have been used for the past 30 years, and in some cases have been developed into well-defined commercial PDT products. This review provides an overview of common liposomal formulation strategies for photosensitizers for PDT and also photothermal therapy. Furthermore, research efforts have examined the impact of co-loading therapeutic cargo along with photosensitizers within liposomes. Additional recent approaches including imaging, overcoming hypoxia, upconversion and activatable liposomal formulations are discussed.

Photodynamic therapy of cancer with liposomal photosensitizers

The photodynamic reaction involves the light-induced generation of an excited state in a photosensitizer molecule (PS), which then results in the formation of reactive oxygen species in the presence of oxygen, or a direct modification of a cellular molecule. Most PSs are porphyrinoids, which are highly lipophilic, and are administered usually in liposomes to facilitate their effective delivery to target cells. The currently available liposomal formulations are Visudyne^® and Fospeg^®. Novel PSs were developed and tested for their photodynamic activity against cancer cells. Several compounds were highly phototoxic to oral cancer cells both in free and liposome-encapsulated form, with nanomolar IC₅₀ values. The lowest IC₅₀s (7-13 nM) were obtained with a PS encapsulated in cationic liposomes.

Porphyrinoid photosensitizers mediated photodynamic inactivation against bacteria

The multi-drug resistant bacteria have become a serious problem complicating therapies to such a degree that often the term "post-antibiotic era" is applied to describe the situation. The infections with methicillin-resistant S. aureus, vancomycin-resistant E. faecium, third generation cephalosporin-resistant E. coli, third generation cephalosporin-resistant K. pneumoniae and carbapenem-resistant P. aeruginosa have become commonplace. Thus, the new strategies of infection treatment have been searched for, and one of the approaches is based on photodynamic antimicrobial chemotherapy. Photodynamic protocols require the interaction of photosensitizer, molecular oxygen and light. The aim of this review is to provide a comprehensive overview of photodynamic antimicrobial chemotherapy by porphyrinoid photosensitizers. In the first part of the review information on the mechanism of photodynamic action and the mechanism of the bacteria resistance to the photodynamic technique were described. In the second one, it was described porphyrinoids photosensitizers like: porphyrins, chlorins and phthalocyanines useable in photodynamic bacteria inactivation.

Biotinylated-cationic zinc(II) phthalocyanine towards photodynamic therapy

Targeting biotin receptors in cancer cells can improve specifying of photosensitizers (PSs) for cancer treatment by photodynamic therapy (PDT) applications. Consequently, there has been extensive research focusing mainly on the design of PSs with optimized pharmaceutical properties and better targeting toward cancer cells. Herein a tailored mono-biotinylated zinc(II) phthalocyanine (Pc-1) substituted with six phenoxy-bis(triazolyl) substituents has been synthesized. This Pc-1 has been further modified to its cationic version (Pc-2) through quaternizing of the triazole moiety to gain water solubility. Both non-ionic zinc(II) phthalocyanine (Pc-1) and its cationic derivative (Pc-2) were characterized by standard spectroscopic techniques, namely; FT-IR, 1H and [Formula: see text]C NMR, UV-Vis and MALDI-TOF, and by elemental analysis. The photophysical and photochemical properties were evaluated in DMSO for the non-ionic Pc-1 and in both DMSO and water for the cationic Pc-2.

Lipid vesicle-loaded meso-substituted chlorins of high in vitro antimicrobial photodynamic activity

Photodynamic inactivation potential against bacteria of four chlorin derivatives with phenyl or fluorophenyl substituents was evaluated. The quantum yield values of singlet oxygen formation were in the range of 0.16-0.86. Compounds were characterized by high quantum yields of fluorescence (0.15-0.44) and moderate photostability in DMF solutions. Irradiation of chlorins in DMSO resulted in their phototransformation and then photodecomposition. Photodynamic inactivation of bacteria was performed after the compounds had been loaded into lipid vesicles. The following log reductions of growth values were obtained: Enterococcus faecalis >5.44; Staphylococcus aureus 2.74-5.34; Escherichia coli 0.01-2.14. No activity of meso-substituted chlorins was noticed against Pseudomonas aeruginosa and fungi Candida albicans and Trichophyton mentagrophytes.

Photodynamic inactivation of Enterococcus faecalis by non-peripherally substituted magnesium phthalocyanines entrapped in lipid vesicles

Photophysical properties and photodynamic antibacterial potential of magnesium phthalocyanines bearing 2-propoxy, benzyloxy, 3,5-bis(benzyloxy)benzyloxy substituents at non-peripheral positions were studied. The UV-Vis absorption spectra of researched phthalocyanine derivatives were found typical. Extension of peripheral substituent size from 2-propoxy to benzyloxy and finally 3,5-bis(benzyloxy)benzyloxy was accompanied by the rise of quantum yield of fluorescence up to 0.17 and 0.04 in DMF and DMSO, respectively. Similarly, the expansion of the phthalocyanine periphery from the 2-propoxy to benzyloxy and 3,5-bis(benzyloxy)benzyloxy groups resulted in a detectable increase of the singlet oxygen quantum yield values to 0.04, 0.12, 0.14 respectively, which was assessed following direct method of singlet oxygen phosphorescence measurement at 1270 nm. Studied phthalocyanines undergo photobleaching process with the quantum yields at the level of 10^-6 in DMSO and 10^-5 in DMF. The size of phthalocyanine impacted the process of liposomal formulation. Small liposome vesicles containing non-peripherally substituted phthalocyanines with 2-propoxy and benzyloxy substituents were obtained following extrusion method. The unification process of the liposomes loaded with 3,5-bis(benzyloxy)benzyloxy non-peripherally substituted phthalocyanines was not possible. In in vitro antimicrobial photodynamic inactivation study, log reduction values of bacterial (Enterococcus faecalis) growth at 3.61 and 2.99 were achieved for liposomal formulations containing phthalocyanines with 2-propoxy and benzyloxy substituents respectively, whereas phthalocyanine with 3,5-bis(benzyloxy)benzyloxy substituents was inactive. Phthalocyanine with 2-propoxy substituents exhibited relatively low toxicity in Vibrio fischeri bioluminescence test, whereas phthalocyanine with benzyloxy substituents revealed intense bioluminescence, which could be associated with hormesis phenomenon.

Hydrogen Bonding Regulates the Rigidity of Liposome-Encapsulated Chlorin Photosensitizers

Liposomal formulations facilitate the administration of hydrophobic drugs, avoiding precipitation and aggregation phenomena when injected in polar solvents. The integration of the photosensitizer into the liposome may alter the fluidity of the system and, thus, modify the delivery process of the drug. Such a change has been observed for the liposomal formulation of Temoporfin, which is one of the most potent chlorin photosensitizers employed in photodynamic therapy. Here, all-atom molecular dynamics simulations have been performed to identify the nature of the intermolecular interactions that might be responsible of the different lipids freedom of motion when the drug is introduced in the bilayer. It is found that Temoporfin participates as a hydrogen donor in strong hydrogen-bonding interactions with the polar groups of the phospholipids. The theoretical analysis suggests that the rigidity of drug/liposome complexes can be modulated by considering the different hydrogen-bond ability of the photosensitizer and the carrier material.

Liposomal formulations of magnesium sulfanyl tribenzoporphyrazines for the photodynamic therapy of cancer

Photodynamic therapy of cancer comprises the activation of photosensitizer molecules delivered to cancer cells, to generate reactive oxygen species that mediate cytotoxicity. In this study, previously synthesized dendritic magnesium tribenzoporphyrazines were incorporated into four types of liposomes containing either 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) as the zwitterionic lipids. The addition of either l-α-phosphatidyl-dl-glycerol (PG) or 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP) imparted a negative or positive charge, respectively. Novel formulations were tested in oral squamous cell carcinoma cell lines (CAL 27, HSC-3) as well as cervical adenocarcinoma cells (HeLa). Positively charged DOTAP:POPC liposomes were the most effective carriers for all tested tribenzoporphyrazines. Calculated IC₅₀ values for DOTAP:POPC liposomes indicated that the incorporation of tribenzoporphyrazines into these liposomes can improve photocytotoxicity up to 50-fold compared to the free forms of macrocycles. Oral cancer cells (CAL 27 and HSC-3) were more sensitive to liposomal photodynamic treatment than HeLa cells.

Nanotechnology for Cancer Therapy Based on Chemotherapy

Chemotherapy has been widely applied in clinics. However, the therapeutic potential of chemotherapy against cancer is seriously dissatisfactory due to the nonspecific drug distribution, multidrug resistance (MDR) and the heterogeneity of cancer. Therefore, combinational therapy based on chemotherapy mediated by nanotechnology, has been the trend in clinical research at present, which can result in a remarkably increased therapeutic efficiency with few side effects to normal tissues. Moreover, to achieve the accurate pre-diagnosis and real-time monitoring for tumor, the research of nano-theranostics, which integrates diagnosis with treatment process, is a promising field in cancer treatment. In this review, the recent studies on combinational therapy based on chemotherapy will be systematically discussed. Furthermore, as a current trend in cancer treatment, advance in theranostic nanoparticles based on chemotherapy will be exemplified briefly. Finally, the present challenges and improvement tips will be presented in combination therapy and nano-theranostics.

Photophysical properties and photocytotoxicity of free and liposome-entrapped diazepinoporphyrazines on LNCaP cells under normoxic and hypoxic conditions

5,7-Diaryl-substituted symmetrical diazepinoporphyrazine and tribenzodiazepinoporphyrazine were synthesized and characterized using UV-Vis, MS MALDI, and various NMR techniques. The expected photosensitizing potentials of these porphyrazines were evaluated by measuring their abilities to generate singlet oxygen in organic solvents and by comparing them with that of the recently obtained dendrimeric G1-type diazepinoporhyrazine. Absorbance and fluorescence measurements were performed to study the aggregation properties of the novel macrocycles. The photocytotoxicity of tribenzodiazepinoporphyrazine towards LNCaP cells in its free form and after its incorporation into liposomes was examined using MTT assay under normoxic and hypoxic conditions. It is interesting that all tested liposome formulations maintained their phototoxic activity in hypoxia. Also, tribenzodiazepinoporphyrazine incorporated into liposomes revealed better photocytotoxic effect (IC₅₀ values of 0.600 ± 0.357 μM and 0.378 ± 0.002 μM) than its free form (IC₅₀ values of 3.135 ± 0.156 μM). Following the in vitro experiments, the most promising liposomal formulation containing l-α-phosphatidyl-DL-glycerol for tribenzodiazepinoporphyrazine was found. Moreover, tribenzodiazepinoporphyrazine incorporated into liposomes containing 1,2-dioleoyl-3-trimethylammonium-propane (chloride salt) revealed moderate phototoxicity at 5 × 10^-5 μM for antibacterial photodynamic therapy. It was established that an irradiation of planktonic bacterial strains significantly reduced CFUs of Staphylococcus aureus ATCC 25923 in comparison to tribenzodiazepinoporphyrazine containing l-α-phosphatidyl-DL-glycerol liposomes.

Porphyrinoid biohybrid materials as an emerging toolbox for biomedical light management

The present article reviews the most important developing strategies in light-induced nanomedicine, based on the combination of porphyrinoid photosensitizers with a wide variety of biomolecules and biomolecular assemblies.

Strategies for optimizing the delivery to tumors of macrocyclic photosensitizers used in photodynamic therapy (PDT)

This review briefly summaries the principles and mechanisms of action of photodynamic therapy (PDT) as concerns its application in the oncological field, highlighting its drawbacks and some of the strategies that have been or are being explored to overcome them. The major aim is to increase the efficiency and selectivity of the photosensitizer (PS) uptake in the cancer cells for optimizing the PDT effects on tumors while sparing normal cells. Some attempts to achieve this are based on the conjugation of the PS to biomolecules (small ligands, peptides) functioning as carriers with the ability to efficiently penetrate cells and/or specifically recognize and bind proteins/receptors overexpressed on the surface of cancer cells. Alternatively, the PS can be entrapped in nanocarriers derived from various types of materials that can target the tumor by exploiting the enhanced permeability and retention (EPR) effects. The use of nanocarriers is particularly attractive because it allows the simultaneous delivery of more than one drug with the possibility of combining PDT with other therapeutic modalities.

Phthalocyanines and Tetrapyrazinoporphyrazines with Two Cationic Donuts: High Photodynamic Activity as a Result of Rigid Spatial Arrangement of Peripheral Substituents

High photodynamic activity was observed for hexadeca-cationic zinc, magnesium, and metal-free phthalocyanines (Pcs) and tetrapyrazinoporphyrazines with EC₅₀ values as low as 5 nM (MCF-7 cells) for the best compound; this activity was several times better than that of clinically established photosensitizers verteporfin, temoporfin, S₃AlOHPc, or protoporphyrin IX. This lead compound was characterized by low dark toxicity (TC₅₀ = 369 μM), high efficiency against other cell lines (HCT 116 and HeLa), and possible activation by light above 680 nm. The excellent photodynamic activity resulted from the rigid spatial arrangement of the quaternized triazole moieties above and below the Pc core, as confirmed by X-ray crystallography. The triazole moieties thus formed two "cationic donuts" that protected the hydrophobic core against aggregation in water. The lysosomes were found to be the site of subcellular localization and were consequently the primary targets of photodynamic injury, resulting in predominantly necrotic cell death.

Phototoxicity of Liposomal Zn- and Al-phthalocyanine Against Cervical and Oral Squamous Cell Carcinoma Cells In Vitro

Background

Photodynamic therapy (PDT) utilizes light to activate a photosensitizer in the presence of oxygen, and leads to local photodamage by the generation of highly reactive oxygen species (ROS). Liposomal delivery of photosensitizers is adaptable to the treatment of cancers. We examined the phototoxicity of free or liposome-embedded phthalocyanine photosensitizers using HeLa cervical carcinoma and HSC-3 oral squamous cell carcinoma cells.

Material/Methods

Liposomes were composed of palmitoyloleoyphosphatidylcholine (POPC): phosphatidylglycerol (PG), and contained either zinc phthalocyanine (ZnPc) or aluminum phthalocyanine chloride (AlPc). Free or liposomal ZnPc and AlPc were incubated with cells for 24 h at 37°C. Cells incubated with ZnPc were exposed to broadband visible light (350–800 nm; light dose 43.2 J/cm²), whereas cells treated with AlPc were exposed to light at 690 nm (light dose 3.6 J/cm²). The effect of folate receptor-targeted liposomal ZnPc was evaluated with HeLa cells. Cytotoxicity was analyzed by the Alamar Blue assay.

Results

Cell viability, expressed as a percentage of control cells, was calculated according to the formula [(A570–A600) of test cells]×100/[(A570–A600) of control cells]. The relative percentage changes then defined the phototoxic efficacy of the experimental conditions. In HeLa cells, 1 μM free ZnPc and AlPc, reduced cell viability to 52.7±2.1 and 15.4±8.0%, respectively. Liposomal phthalocyanines, at 0.1, 0.5, and 1.0 μM, reduced the viability to 68.0±8.6, 15.1±9.9 and 0% (ZnPc), and to 25.8±8.2, 0 and 0% (AlPc), respectively. In HSC-3 cells, 1 μM free ZnPc and AlPc, reduced cell viability to 22.1±2.8 and 56.6±8.6%, respectively. With 1 μM liposomal ZnPc and AlPc, the viability was reduced to 0 and 21.3±0.3%, respectively.

Conclusions

The embedding of phthalocyanines in liposomes enhanced their phototoxicity and this effect was dependent on cell type.

The Smart Drug Delivery System and Its Clinical Potential

With the unprecedented progresses of biomedical nanotechnology during the past few decades, conventional drug delivery systems (DDSs) have been involved into smart DDSs with stimuli-responsive characteristics. Benefiting from the response to specific internal or external triggers, those well-defined nanoplatforms can increase the drug targeting efficacy, in the meantime, reduce side effects/toxicities of payloads, which are key factors for improving patient compliance. In academic field, variety of smart DDSs have been abundantly demonstrated for various intriguing systems, such as stimuli-responsive polymeric nanoparticles, liposomes, metals/metal oxides, and exosomes. However, these nanoplatforms are lack of standardized manufacturing method, toxicity assessment experience, and clear relevance between the pre-clinical and clinical studies, resulting in the huge difficulties to obtain regulatory and ethics approval. Therefore, such relatively complex stimulus-sensitive nano-DDSs are not currently approved for clinical use. In this review, we highlight the recent advances of smart nanoplatforms for targeting drug delivery. Furthermore, the clinical translation obstacles faced by these smart nanoplatforms have been reviewed and discussed. We also present the future directions and perspectives of stimuli-sensitive DDS in clinical applications.