Drastic differences between the release kinetics of two highly related porphyrins in liposomal membranes: mTHPP and pTHPP

HYPOTHESIS

The release of hydrophobic compounds from liposomal membranes occurs by partitioning and is thus determined by the physicochemical properties (e.g. logP and water solubility) of the drug. We postulate that even minor structural differences, e.g. the position of the phenolic OH-group of the hydrophobic porphyrins mTHPP and pTHPP (meta vs. para substitution), distinctly affect their partitioning and release behavior from liposomes.

EXPERIMENTS

The release and redistribution of mTHPP and pTHPP from lecithin or POPC/POPG liposomes to different acceptor particles (DSPE-mPEG micelles and liposomes) was studied by asymmetrical flow field-flow fractionation to separate donor and acceptor particles. Reversed phase HPLC was applied to detect differences in partitioning. Molecular dynamics (MD) simulations were carried out to obtain molecular insight in the different behavior of the two compounds inside a lipid bilayer.

FINDINGS

Despite the minor differences in chemical structure, mTHPP is more hydrophobic and redistributes much slower to both acceptor phases than pTHPP. MD simulations indicate that compared to pTHPP, mTHPP makes stronger hydrogen bonds with the lipid head groups, is oriented more parallel to the lipid tails and is embedded slightly deeper in the membrane.

Nanoparticle Systems for Cancer Phototherapy: An Overview

Photodynamic therapy (PDT) and photothermal therapy (PTT) are photo-mediated treatments with different mechanisms of action that can be addressed for cancer treatment. Both phototherapies are highly successful and barely or non-invasive types of treatment that have gained attention in the past few years. The death of cancer cells because of the application of these therapies is caused by the formation of reactive oxygen species, that leads to oxidative stress for the case of photodynamic therapy and the generation of heat for the case of photothermal therapies. The advancement of nanotechnology allowed significant benefit to these therapies using nanoparticles, allowing both tuning of the process and an increase of effectiveness. The encapsulation of drugs, development of the most different organic and inorganic nanoparticles as well as the possibility of surfaces' functionalization are some strategies used to combine phototherapy and nanotechnology, with the aim of an effective treatment with minimal side effects. This article presents an overview on the use of nanostructures in association with phototherapy, in the view of cancer treatment.

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.

Immune Reprogramming Precision Photodynamic Therapy of Peritoneal Metastasis by Scalable Stem-Cell-Derived Extracellular Vesicles

The dissemination of tumor metastasis in the peritoneal cavity, also called peritoneal metastasis (PM) or carcinomatosis, represents a late stage of gastrointestinal and gynecological cancer with very poor prognosis, even when cytoreductive surgery is effective, due to residual microscopic disease. Photodynamic therapy (PDT) in the management of peritoneal metastasis has been clinically limited by the low tumor selectivity of photosensitizers (PS) and important adverse effects. Here, we propose extracellular nanovesicles (EVs) derived from mesenchymal stem/stromal cells (MSCs) as the fourth generation of immune active PS vectors that are able to target peritoneal metastasis with superior selectivity, potentiate PDT cytotoxicity at the tumor site without affecting healthy tissues, modulate the tumor microenvironment of immunocompetent colorectal and ovarian carcinomatosis models, and promote an antitumor immune response. A pioneering strategy was developed for high yield, large-scale production of MSC-EVs encapsulating the drug meta(tetrahydroxyphenyl)chlorin (mTHPC) (EVs-mTHPC) that is compatible with requirements of clinical translation and also preserves the topology and integrity of naturally produced EVs. Intraperitoneal injection of EVs-mTHPC showed an impressive enhancement of tumoral selectivity in comparison to the free drug and to the liposomal formulation Foslip (mean ratio of PS in tumors/organs of 40 for EVs-mTHPC versus 1.5 for the free PS and 5.5 for Foslip). PDT mediated by EVs-mTHPC permitted an important tumoral necrosis (55% of necrotic tumoral nodules versus 18% for Foslip (p < 0.0001)) and promoted antitumor immune cell infiltration, mainly proinflammatory M1-like CD80+ and CD8+ T cell effector. Intratumor proliferation was significantly decreased after PDT with EVs-mTHPC. Overall EVs vectorization of mTHPC afforded important tumoral selectivity while overcoming the PDT toxicity of the free drug and prolonged mice survival in the colorectal carcinomatosis model. MSC-EVs produced by our scalable manufacturing method appears like the clinically relevant fourth-generation PDT vehicle to overcome current limitations of PDT in the treatment of peritoneal metastasis and promote a hot tumor immune environment in PM.

Lipoparticles for Synergistic Chemo-Photodynamic Therapy to Ovarian Carcinoma Cells: In vitro and in vivo Assessments

PURPOSE

Lipoparticles are the core-shell type lipid-polymer hybrid systems comprising polymeric nanoparticle core enveloped by single or multiple pegylated lipid layers (shell), thereby melding the biomimetic properties of long-circulating vesicles as well as the mechanical advantages of the nanoparticles. The present study was aimed at the development of such an integrated system, combining the photodynamic and chemotherapeutic approaches for the treatment of multidrug-resistant cancers.

METHODS

For this rationale, two different sized Pirarubicin (THP) loaded poly lactic-co-glycolic acid (PLGA) nanoparticles were prepared by emulsion solvent evaporation technique, whereas liposomes containing Temoporfin (mTHPC) were prepared by lipid film hydration method. Physicochemical and morphological characterizations were done using dynamic light scattering, laser doppler anemometry, atomic force microscopy, and transmission electron microscopy. The quantitative assessment of cell damage was determined using MTT and reactive oxygen species (ROS) assay. The biocompatibility of the nanoformulations was evaluated with serum stability testing, haemocompatibility as well as acute in vivo toxicity using female albino (BALB/c) mice.

RESULTS AND CONCLUSION

The mean hydrodynamic diameter of the formulations was found between 108.80 ± 2.10 to 405.70 ± 10.00 nm with the zeta (ζ) potential ranging from -12.70 ± 1.20 to 5.90 ± 1.10 mV. Based on the physicochemical evaluations, the selected THP nanoparticles were coated with mTHPC liposomes to produce lipid-coated nanoparticles (LCNPs). A significant (p< 0.001) cytotoxicity synergism was evident in LCNPs when irradiated at 652 nm, using an LED device. No incidence of genotoxicity was observed as seen with the comet assay. The LCNPs decreased the generalized in vivo toxicity as compared to the free drugs and was evident from the serum biochemical profile, visceral body index, liver function tests as well as renal function tests. The histopathological examinations of the vital organs revealed no significant evidence of toxicity suggesting the safety and efficacy of our lipid-polymer hybrid system.

Effect of stroma on the behavior of temoporfin-loaded lipid nanovesicles inside the stroma-rich head and neck carcinoma spheroids

Background

Despite the highly expected clinical application of nanoparticles (NPs), the translation of NPs from lab to the clinic has been relatively slow. Co-culture 3D spheroids account for the 3D arrangement of tumor cells and stromal components, e.g., cancer-associated fibroblasts (CAFs) and extracellular matrix, recapitulating microenvironment of head and neck squamous cell carcinoma (HNSCC). In the present study, we investigated how the stroma-rich tumor microenvironment affects the uptake, penetration, and photodynamic efficiency of three lipid-based nanoformulations of approved in EU photosensitizer temoporfin (mTHPC): Foslip^® (mTHPC in conventional liposomes), drug-in-cyclodextrin-in-liposomes (mTHPC-DCL) and extracellular vesicles (mTHPC-EVs).

Results

Collagen expression in co-culture stroma-rich 3D HNSCC spheroids correlates with the amount of CAFs (MeWo cells) in individual spheroid. The assessment of mTHPC loading demonstrated that Foslip^®, mTHPC-DCL and mTHPC-EVs encapsulated 0.05 × 10^− 15 g, 0.07 × 10^− 15 g, and 1.3 × 10^− 15 g of mTHPC per nanovesicle, respectively. The mid-penetration depth of mTHPC NPs in spheroids was 47.8 µm (Foslip^®), 87.8 µm (mTHPC-DCL), and 49.7 µm (mTHPC-EVs), irrespective of the percentage of stromal components. The cellular uptake of Foslip^® and mTHPC-DCL was significantly higher in stroma-rich co-culture spheroids and was increasing upon the addition of serum in the culture medium. Importantly, we observed no significant difference between PDT effect in monoculture and co-culture spheroids treated with lipid-based NPs. Overall, in all types of spheroids mTHPC-EVs demonstrated outstanding total cellular uptake and PDT efficiency comparable to other NPs.

Conclusions

The stromal microenvironment strongly affects the uptake of NPs, while the penetration and PDT efficacy are less sensitive to the presence of stromal components. mTHPC-EVs outperform other lipid nanovesicles due to the extremely high loading capacity. The results of the present study enlarge our understanding of how stroma components affect the delivery of NPs into the tumors.

Stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles for drug delivery and theranostics

Liposomes represent one of the most successful nano-drug delivery systems among enormous nano-carriers. Although great progress has been made in conventional liposomes, the emerging shortcomings still impair the therapeutic index. The proposal of stimuli-responsive phospholipid-drug conjugates (PDCs)-based nanovesicles solves the challenges that conventional liposomes are faced with, showing great potential for cancer diagnosis and therapy. Herein, we intend to overview the current progress and unique advantages of stimuli-responsive PDCs-based nanovesicles. First, the challenges of conventional liposomes and the development of PDCs-based nanovesicles are summarized. Next, the stimuli-responsive elements used in current stimuli-responsive PDCs-based nanovesicles are outlined. Then, the unique superiorities of stimuli-responsive PDCs-based nanovesicles for drug delivery and theranostics are highlighted in detail. Finally, the future opportunities and challenges of stimuli-responsive PDCs-based nanovesicles for clinical translation are put forward.

Application of a polyelectrolyte complex based on biocompatible polysaccharides for colorectal cancer inhibition

Strategies for incorporating water-insoluble photosensitisers (PS) in drug delivery systems have been extensively studied. In this work, we evaluate the formation, characterisation, drug sorption studies, and cytotoxicity of chitosan (CHT)/chondroitin sulphate (CS) polyelectrolyte complexes (PECs) coated with polystyrene-block-poly(acrylic acid) (PS-b-PAA) nanoparticles (NPs) loaded with chloroaluminum phthalocyanine (AlClPc). The PECs were characterised by infrared spectroscopy (FTIR), differential scanning calorimetric (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The PS-b-PAA NPs on the PEC surface was confirmed by scanning electron microscopy (SEM). Additionally, optical images distinguished the PEC structures containing PS-b-PAA or PS-b-PAA/AlClPc from the unloaded PEC. Kinetic and equilibrium studies investigate the sorption capacity of the PEC/PS-b-PAA toward AlClPc. The encapsulation efficiency reached 95% at 190 μg mL^-1 AlClPc after only 15 min. The Brunauer-Emmett-Teller (BET) isotherm and pseudo-second-order kinetic fitted well to the experimental data. The PS-b-PAA NPs on the PEC surfaces increase the AlClPc bioavailability and the PEC structure stabilizes the PS-b-PAA/AlClPc nanostructures. The materials were cytocompatible upon healthy VERO (kidney epithelial cells), and cytotoxic against colorectal cancerous cells (HT-29 cells). For the first time, we associate PS-b-PAA/AlClPc with a hydrophilic and cytocompatible polysaccharide matrix. We suggest the use of these materials in strategies to treat cancer by using photodynamic therapy.

mTHPC-Loaded Extracellular Vesicles Significantly Improve mTHPC Diffusion and Photodynamic Activity in Preclinical Models

Extracellular vesicles (EVs), derived from the cell, display a phospholipid bilayer membrane that protects the cargo molecules from degradation and contributes to increasing their stability in the bloodstream and tumor targeting. EVs are interesting in regard to the delivery of photosensitizers (PSs) used in the photodynamic therapy (PDT), as they allow us to overcome the limitations observed with liposomes. In fact, liposomal formulation of meta-tetra(hydroxyphenyl)chlorin (mTHPC) (Foslip^®), one of the most potent clinically approved PSs, is rapidly destroyed in circulation, thus decreasing in vivo PDT efficacy. mTHPC-EV uptake was evaluated in vitro in a 3D human colon HT-29 microtumor and in vivo study was performed in HT-29 xenografted mice. The obtained data were compared with Foslip^®. After intravenous injection of the mTHPC formulations, biodistribution, pharmacokinetics and PDT-induced tumor regrowth were evaluated. In a 3D model of cells, mTHPC-EV uptake featured a deeper penetration after 24h incubation compared to liposomal mTHPC. In vivo results showed a considerable improvement of 33% tumor cure with PDT treatment applied 24h after injection, while 0% was observed after Foslip^®/PDT. Moreover, 47 days were required to obtain ten times the initial tumor volume after mTHPC-EVs/PDT compared to 30 days for liposomal mTHPC. In conclusion, compared to Foslip^®, mTHPC-EVs improved mTHPC biodistribution and PDT efficacy in vivo. We deduced that a major determinant factor for the improved in vivo PDT efficacy is the deep mTHPC intratumor penetration.

Optical properties of photodynamic therapy drugs in different environments: the paradigmatic case of temoporfin

Computational tools have been used to study the photophysical and photochemical features of photosensitizers in photodynamic therapy (PDT) - a minimally invasive, less aggressive alternative for cancer treatment. PDT is mainly based on the activation of molecular oxygen through the action of a photoexcited sensitizer (photosensitizer). Temoporfin, widely known as mTHPC, is a second-generation photosensitizer, which produces the cytotoxic singlet oxygen when irradiated with visible light and hence destroys tumor cells. However, the bioavailability of the mostly hydrophobic photosensitizer, and hence its incorporation into cells, is fundamental to achieve the desired effect on malignant tissues via PDT. In this study, we focus on the optical properties of the temoporfin chromophore in different environments -in vacuo, in solution, encapsulated in drug delivery agents, namely cyclodextrin, and interacting with a lipid bilayer.

Cyclodextrin nanosponge as a temoporfin nanocarrier: Balancing between accumulation and penetration in 3D tumor spheroids

As the intertissue delivery of hydrophobic temoporfin (mTHPC) remains inefficient, we propose the use of cyclodextrin-based nanosponges as a smart, advanced system for improved mTHPC delivery. Recently, we demonstrated that cyclodextrins (CDs) allow mTHPC to penetrate into tumor spheroids via a nanoshuttle mechanism. However, the CD complexes were very sensitive to the dilution, thus limiting their translation invivo. Hypercrosslinked CD monomers in a three-dimensional network (namely, CD nanosponges), however, may form both inclusion and non-inclusion complexes with drug molecules, providing controlled release and prolonged exposure to the drug. In the present work, we demonstrate that epichlorohydrin-crosslinked CD nanosponges based on β-CD (βCDp) and carboxymethyl-β-CD (CMβCDp) monomers efficiently encapsulated mTHPC. We calculated the apparent binding constants between mTHPC and CD polymers (K=(6.3-8.8) × 10⁶M^-1 and K=(1.2-1.7) × 10⁶M^-1 for βCDp and CMβCDp, respectively) using fluorescence titration curve fitting. The encapsulation of mTHPC in a CD polymer matrix had slower photosensitizer (PS) release compared to monomer CD units, providing deep penetration of mTHPC in 3D tumor spheroids in a concentration-dependent manner. However, the improvement of mTHPC penetration in 3D human pharynx squamous cell carcinoma (FaDu) spheroids using CD polymers was strongly accompanied by the inhibition of PS cellular uptake, demonstrating the delicate balance between the accumulation and the penetration of PS in FaDu spheroids. In summary, mTHPC-loaded CD nanosponges are a strong candidate for further invivo study in preclinical models, which could be considered as an advanced smart system for mTHPC delivery.

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.

Matryoshka-Type Liposomes Offer the Improved Delivery of Temoporfin to Tumor Spheroids

The balance between the amount of drug delivered to tumor tissue and the homogeneity of its distribution is a challenge in the efficient delivery of photosensitizers (PSs) in photodynamic therapy (PDT) of cancer. To date, many efforts have been made using various nanomaterials to efficiently deliver temoporfin (mTHPC), one of the most potent photosensitizers. The present study aimed to develop double-loaded matryoshka-type hybrid nanoparticles encapsulating mTHPC/cyclodextrin inclusion complexes in mTHPC-loaded liposomes. This system was expected to improve the transport of mTHPC to target tissues and to strengthen its accumulation in the tumor tissue. Double-loaded hybrid nanoparticles (DL-DCL) were prepared, characterized, and tested in 2D and 3D in vitro models and in xenografted mice in vivo. Our studies indicated that DL-DCL provided deep penetration of mTHPC into the multicellular tumor spheroids via cyclodextrin nanoshuttles once the liposomes had been destabilized by serum proteins. Unexpectedly, we observed similar PDT efficiency in xenografted HT29 tumors for liposomal mTHPC formulation (Foslip^®) and DL-DCL.

Current state of the nanoscale delivery systems for temoporfin-based photodynamic therapy: Advanced delivery strategies

Enthusiasm for photodynamic therapy (PDT) as a promising technique to eradicate various cancers has increased exponentially in recent decades. The majority of clinically approved photosensitizers are hydrophobic in nature, thus, the effective delivery of photosensitizers at the targeted site is the main hurdle associated with PDT. Temoporfin (mTHPC, medicinal product name: Foscan®), is one of the most potent clinically approved photosensitizers, is not an exception. Successful temoporfin-PDT requires nanoscale delivery systems for selective delivery of photosensitizer. Over the last 25 years, the number of papers on nanoplatforms developed for mTHPC delivery such as conjugates, host-guest inclusion complexes, lipid-and polymer-based nanoparticles and carbon nanotubes is burgeoning. However, none of them appeared to be "ultimate". The present review offers the description of different challenges and achievements in nanoparticle-based mTHPC delivery focusing on the synergetic combination of various nano-platforms to improve temoporfin delivery at all stages of biodistribution. Furthermore, the association of different nanoparticles in one nanoplatform might be considered as an advanced strategy allowing the combination of several treatment modalities.

Assessing Configurational Sampling in the Quantum Mechanics/Molecular Mechanics Calculation of Temoporfin Absorption Spectrum and Triplet Density of States

The absorption properties of Temoporfin, a second-generation photosensitizer employed in photodynamic therapy, are calculated with an electrostatic-embedding quantum mechanics/molecular mechanics (QM/MM) scheme in methanol. The suitability of several ensembles of geometries generated by different sampling techniques, namely classical-molecular-dynamics (MD) and QM/MM-MD thermal sampling, Wigner quantum sampling and a hybrid protocol, which combines the thermal and quantum approaches, is assessed. It is found that a QM description of the chromophore during the sampling is needed in order to achieve a good agreement with respect to the experimental spectrum. Such a good agreement is obtained with both QM/MM-MD and Wigner samplings, demonstrating that a proper description of the anharmonic motions of the chromophore is not relevant in the computation of the absorption properties. In addition, it is also found that solvent organization is a rather fast process and a long sampling is not required. Finally, it is also demonstrated that the same exchange-correlation functional should be employed in the sampling and in the computation of the excited states properties to avoid unphysical triplet states with relative energies close or below 0 eV.

mTHPC-loaded extracellular vesicles outperform liposomal and free mTHPC formulations by an increased stability, drug delivery efficiency and cytotoxic effect in tridimensional model of tumors

Efficient photodynamic therapy with meta-tetra(hydroxyphenyl)chlorine requires the application of specific nanoformulations. mTHPC liposomal formulation (Foslip®) demonstrated favorable pharmacokinetics properties. However, rapid liposomes destruction in circulation and rapid mTHPC release impedes Foslip® applications. Alternatively, mTHPC nanovectorization using extracellular vesicles (EVs) could be an attractive option. EVs are naturally secreted by the organism to play a role in intercellular communication due to the capacity to transport proteins and nucleic acids. EVs also possess a natural ability to deliver therapeutic molecules into cancer cells. The aim of the present study was to evaluate photophysical and photobiological properties of mTHPC loaded in endothelial EVs as nanocarriers. We also studied efficiency of nanovectorisation on mTHPC distribution and PDT activity in multicellular tumor spheroids (MCTSs). MCTS is a nonvascularized in vitro 3D model of cells that mimics a similar microenvironment to in vivo situation. mTHPC-EVs were characterized by means of spectroscopic techniques, flow cytometry and nanoparticle tracking analysis. Compared with Foslip®, mTHPC-EVs are stable in murine plasma. Better mTHPC accumulation and penetration (up to 100 µm) in MCTS was observed for mTHPC-EVs compared with liposomal mTHPC. These factors could explain enhanced photodynamic activity of mTHPC-EVs compared with free and liposomal mTHPC. The light dose inducing 50% of cell death with mTHPC-EVs was 4 and 2.5-times lower than that of free and liposomal mTHPC. The obtained results demonstrate that EVs should be considered as perspective nanocarriers for mTHPC-mediated PDT.

Stabilized tetraether lipids based particles guided prophyrins photodynamic therapy

Photodynamic therapy (PDT) that involves ergonomically delivered light in the presence of archetypical photosensitizer such as Protoporphyrin IX (PpIX) is a time-honored missile strategy in cancer therapeutics. Yet, the premature release of PpIX is one of the most abundant dilemma encounters the therapeutic outcomes of PDT due to associated toxicity and redistribution to serum proteins. In this study, ultrastable tetraether lipids (TELs) based liposomes were developed. PpIX molecules were identified to reside physically in the monolayer; thereby the inherent π-π stacking that leads to aggregation of PpIX in aqueous milieu was dramatically improved. TEL29.9 mol% and TEL62mol% based liposomes revealed PpIX sustained release diffusion pattern from spherical particles as confirmed by converged fitting to Baker & Lonsdale model. Stability in presence of human serum albumins, a key element for PDT accomplishment was emphasized. The epitome candidates were selected for vascular photodynamic (vPDT) in in-Ovo chick chorioallantoic membrane. Profoundly, TEL62mol% based liposomes proved to be the most effective liposomes that demonstrated localized effect within the irradiated area without eliciting quiescent vasculatures damages. Cellular photodynamic therapy (cPDT) revealed that various radiant exposure doses of 134, 202, 403 or 672 mJ.cm-2 could deliberately modulate the photo-responses of PpIX in TEL-liposomes.

Temoporfin-in-Cyclodextrin-in-Liposome-A New Approach for Anticancer Drug Delivery: The Optimization of Composition

The main goal of this study was to use hybrid delivery system for effective transportation of temoporfin (meta-tetrakis(3-hydroxyphenyl)chlorin, mTHPC) to target tissue. We suggested to couple two independent delivery systems (liposomes and inclusion complexes) to achieve drug-in-cyclodextrin-in-liposome (DCL) nanoconstructs. We further optimized the composition of DCLs, aiming to alter in a more favorable way a distribution of temoporfin in tumor tissue. We have prepared DCLs with different compositions varying the concentration of mTHPC and the type of β-cyclodextrin (β-CD) derivatives (Hydroxypropyl-, Methyl- and Trimethyl-β-CD). DCLs were prepared by thin-hydration technique and mTHPC/β-CD complexes were added at hydration step. The size was about 135 nm with the surface charge of (−38 mV). We have demonstrated that DCLs are stable and almost all mTHPC is bound to β-CDs in the inner aqueous liposome core. Among all tested DCLs, trimethyl-β-CD-based DCL demonstrated a homogenous accumulation of mTHPC across tumor spheroid volume, thus supposing optimal mTHPC distribution.

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.

Foscan and foslip based photodynamic therapy in osteosarcoma in vitro and in intratibial mouse models

Current osteosarcoma therapies cause severe treatment-related side effects and chemoresistance, and have low success rates. Consequently, alternative treatment options are urgently needed. Photodynamic therapy (PDT) is a minimally invasive, local therapy with proven clinical efficacy for a variety of tumor types. PDT is cytotoxic, provokes anti-vascular effects and stimulates tumor cell targeting mechanisms of the immune system and, consequently, has potential as a novel therapy for osteosarcoma patients. This study investigated the uptake and the dark- and phototoxicity and cytotoxic mechanisms of the photosensitizer (PS) 5,10,15,20-tetrakis(meta-hydroxyphenyl) chlorine (mTHPC, Foscan) and a liposomal mTHPC formulation (Foslip) in the human 143B and a mouse K7M2-derived osteosaroma cell line (K7M2L2) in vitro. Second, the tumor- and metastasis-suppressive efficacies of mTHPC formulations based PDT and associated mechanisms in intratibial, metastasizing osteosarcoma mouse models (143B/SCID and syngeneic K7M2L2/BALB/c) were studied. The uptake of Foscan and Foslip in vitro was time- and dose-dependent and resulted in mTHPC and light dose-dependent phototoxicity associated with apoptosis. In vivo, the uptake of both i.v. administered mTHPC formulations was higher in tumor than in healthy control tissue. PDT caused significant (Foscan p < 0.05, Foslip p < 0.001) tumor growth inhibition in both models. A significant (Foscan p < 0.001, Foslip p < 0.001) immune system-dependent suppression of lung metastasis was only observed in the K7M2L2/BALB/c model and was associated with a marked infiltration of T-lymphocytes at the primary tumor site. In conclusion, mTHPC-based PDT is effective in clinically relevant experimental osteosarcoma and suppresses lung metastasis in immunocompetent mice with beneficial effects of the liposomal mTHPC formulation Foslip.

Inclusion complexation with β-cyclodextrin derivatives alters photodynamic activity and biodistribution of meta-tetra(hydroxyphenyl)chlorin

Application of meta-tetra(hydroxyphenyl)chorin (mTHPC) one of the most effective photosensitizer (PS) in photodynamic therapy of solid tumors encounters several complications resulting from its insolubility in aqueous medium. To improve its solubility and pharmacokinetic properties, two modified β-cyclodextrins (β-CDs) methyl-β-cyclodextrin (M-β-CD) and 2-hydroxypropyl-β-cyclodextrin (Hp-β-CD) were proposed. The aim of this work was to evaluate the effect of β-CDs on mTHPC behavior at various stages of its distribution in vitro and in vivo. For this purpose, we have studied the influence of the β-CDs on mTHPC binding to the serum proteins, its accumulation, distribution and photodynamic efficiency in HT29 cells. In addition, the processes of mTHPC biodistribution in HT29 tumor bearing mice after intravenous injection of PS alone or with the β-CDs were compared. Interaction of mTHPC with studied β-CDs leads to the formation of inclusion complexes that completely abolishes its aggregation after introduction into serum. It was demonstrated that the β-CDs have a concentration-dependent effect on the process of mTHPC distribution in blood serum. At high concentrations, β-CDs can form inclusion complexes with mTHPC in the blood that can have a significant impact on PS distribution out of the vascular system in solid tissues. Besides, the β-CDs increase diffusion movement of mTHPC molecules that can significantly accelerate the delivery of PS to the targets cells and tissues. In vivo study confirms the fact that the use of β-CDs allows to modify mTHPC distribution processes in tumor bearing animals that is reflected in the decreased level of PS accumulation in skin and muscles, as well as in the increased PS accumulation in tumor. Further studies are underway to verify the optimal protocols of mTHPC/β-CD formulation for photodynamic therapy.

Factors affecting the selectivity of nanoparticle-based photoinduced damage in free and xenografted chorioallantoïc membrane model

BACKGROUND

Photodynamic therapy (PDT) is a minimally invasive treatment modality for selective destruction of tumours. Critical anatomical structures, like blood vessels in close proximity to the tumour, could be harmed during PDT.

PURPOSE

This study aims to discriminate the photoinduced response of normal and cancerous tissues to photodamage induced by liposomal formulations of meta-tetra(hydroxyphenyl)chlorin (mTHPC).

METHODS

Normal vascular and cancerous tissues were represented, respectively, by free and xenografted in vivo model of chick chorioallantoïc membrane (CAM). Eggs received an intravenous administration of plain (Foslip®) or stabilised formulations (Fospeg®). Drug release and liposome destruction were, respectively, determined by photoinduced quenching and nanoparticle tracking analysis. PDT was performed at different drug-light intervals (DLI) with further assessment of photothrombic activity, tumoritropism and photoinduced necrosis.

RESULTS

Compared to Foslip®, Fospeg® demonstrated significantly higher stability, slower drug release, better tumoricidal effect and lower damage to the normal vasculature at already 1 h DLI.

DISCUSSION

This work suggests that nanoparticle-based PDT selectivity could be optimised by analyzing the photoinduced damage of healthy and tumour tissues.

CONCLUSION

In fine, Fospeg® appeared to be the ideal candidate in clinical context due to its potential to destroy tumours and reduce vascular damage to normal tissues at short DLI.

Localization of liposomal mTHPC formulations within normal epithelium, dysplastic tissue, and carcinoma of oral epithelium in the 4NQO-carcinogenesis rat model

BACKGROUND AND OBJECTIVE

Foslip and Fospeg are liposomal formulations of the photosensitizer mTHPC (Foscan), which is used for photodynamic therapy (PDT) of malignancies. Literature suggests that liposomal mTHPC formulations have better properties and increased tumor uptake compared to Foscan. To investigate this, we used the 4NQO-induced carcinogen model to compare the localization of the different mTHPC formulations within normal, precancerous, and cancerous tissue. In contrast to xenograft models, the 4NQO model closely mimics the carcinogenesis of human oral dysplasia.

MATERIALS AND METHODS

Fifty-four rats drank water with the carcinogen 4NQO. When oral examination revealed tumor, the rats received 0.15 mg/kg mTHPC (Foscan, Foslip, or Fospeg). At 2, 4, 8, 24, 48, or 96 hours after injection the rats were sacrificed. Oral tissue was sectioned for HE slides and for fluorescence confocal microscopy. The HE slides were scored on the severity of dysplasia by the epithelial atypia index (EAI). The calibrated fluorescence intensity per formulation or time point was correlated to EAI.

RESULTS

Fospeg showed higher mTHPC fluorescence in normal and tumor tissue compared to both Foscan and Foslip. Significant differences in fluorescence between tumor and normal tissue were found for all formulations. However, at 4, 8, and 24 hours only Fospeg showed a significant difference. The Pearson's correlation between EAI and mTHPC fluorescence proved weak for all formulations.

CONCLUSION

In our induced carcinogenesis model, Fospeg exhibited a tendency for higher fluorescence in normal and tumor tissue compared to Foslip and Foscan. In contrast to Foscan and Foslip, Fospeg showed significantly higher fluorescence in tumor versus normal tissue at earlier time points, suggesting a possible clinical benefit compared to Foscan. Low correlation between grade of dysplasia and mTHPC fluorescence was found.

Photodynamic therapy with conventional and PEGylated liposomal formulations of mTHPC (temoporfin): comparison of treatment efficacy and distribution characteristics in vivo

A major challenge in the application of a nanoparticle-based drug delivery system for anticancer agents is the knowledge of the critical properties that influence their in vivo behavior and the therapeutic performance of the drug. The effect of a liposomal formulation, as an example of a widely-used delivery system, on all aspects of the drug delivery process, including the drug’s behavior in blood and in the tumor, has to be considered when optimizing treatment with liposomal drugs, but that is rarely done. This article presents a comparison of conventional (Foslip®) and polyethylene glycosylated (Fospeg®) liposomal formulations of temoporfin (meta-tetra[hydroxyphenyl]chlorin) in tumor-grafted mice, with a set of comparison parameters not reported before in one model. Foslip® and Fospeg® pharmacokinetics, drug release, liposome stability, tumor uptake, and intratumoral distribution are evaluated, and their influence on the efficacy of the photodynamic treatment at different light–drug intervals is discussed. The use of whole-tumor multiphoton fluorescence macroscopy imaging is reported for visualization of the in vivo intratumoral distribution of the photosensitizer. The combination of enhanced permeability and retention-based tumor accumulation, stability in the circulation, and release properties leads to a higher efficacy of the treatment with Fospeg® compared to Foslip®. A significant advantage of Fospeg® lies in a major decrease in the light–drug interval, while preserving treatment efficacy.

Current status of liposomal porphyrinoid photosensitizers

The complete eradication of various targets, such as infectious agents or cancer cells, while leaving healthy host cells untouched, is still a great challenge faced in the field of medicine. Photodynamic therapy (PDT) seems to be a promising approach for anticancer treatment, as well as to combat various dermatologic and ophthalmic diseases and microbial infections. The application of liposomes as delivery systems for porphyrinoids has helped overcome many drawbacks of conventional photosensitizers and facilitated the development of novel effective photosensitizers that can be encapsulated in liposomes. The development, preclinical studies and future directions for liposomal delivery of conventional and novel photosensitizers are reviewed.

Pharmacokinetics of temoporfin-loaded liposome formulations: correlation of liposome and temoporfin blood concentration

Liposomal formulations of the highly hydrophobic photosensitizer temoporfin were developed in order to overcome solubility-related problems associated with the current therapy scheme. We have incorporated temoporfin into liposomes of varying membrane composition, cholesterol content, and vesicle size. Specifically, two phosphatidyl oligoglycerols were compared to PEG2000-DSPE with respect to the ability to prolong circulation half life of the liposomal carrier. We measured the resulting pharmacokinetic profile of the liposomal carrier and the incorporated temoporfin in a rat model employing a radioactive lipid label and (14)C-temoporfin. The data for the removal of liposomes and temoporfin were analyzed in terms of classical pharmacokinetic theory assuming a two-compartment model. This model, however, does not allow in a straightforward manner to distinguish between temoporfin eliminated together with the liposomal carrier and temoporfin that is first transferred to other blood components (e. g. plasma proteins) before being eliminated from the blood. We therefore additionally analyzed the data based on two separate one-compartment models for the liposomes and temoporfin. The model yields the ratio of the rate constant of temoporfin elimination together with the liposomal carrier and the rate constant of temoporfin elimination following the transfer to e. g. plasma proteins. Our analysis using this model demonstrates that a fraction of temoporfin is released from the liposomes prior to being eliminated from the blood. In case of unmodified liposomes this temoporfin release was observed to increase with decreasing bilayer fluidity, indicating an accelerated temoporfin transfer from gel-phase liposomes to e. g. plasma proteins. Interestingly, liposomes carrying either one of the three investigated surface-modifying agents did not adhere to the tendencies observed for unmodified liposomes. Although surface-modified liposomes exhibited improved pharmacokinetic properties with regard to the liposomal carrier, an enhanced temoporfin loss and elimination from the PEGylated-liposomes was observed. This effect was more pronounced for PEGylated liposomes than for the two oligo-glycerols. Our combined experimental-theoretical approach for in vivo plasma re-distribution of liposomal drugs may help to optimize colloidal drug carrier systems.

Fully protected glycosylated zinc (II) phthalocyanine shows high uptake and photodynamic cytotoxicity in MCF-7 cancer cells

Phthalocyanine photosensitizers are effective in anticancer photodynamic therapy (PDT) but suffer from limited solubility, limited cellular uptake and limited selectivity for cancer cells. To improve these characteristics, we synthesized isopropylidene-protected and partially deprotected tetra β-glycosylated zinc (II) phthalocyanines and compared their uptake and accumulation kinetics, subcellular localization, in vitro photocytotoxicity and reactive oxygen species generation with those of disulfonated aluminum phthalocyanine. In MCF-7 cancer cells, one of the compounds, zinc phthalocyanine {4}, demonstrated 10-fold higher uptake, 5-fold greater PDT-induced cellular reactive oxygen species concentration and 2-fold greater phototoxicity than equimolar (9 μm) disulfonated aluminum phthalocyanine. Thus, isopropylidene-protected β-glycosylation of phthalocyanines provides a simple method of improving the efficacy of PDT.

Interaction of liposomal formulations of meta-tetra(hydroxyphenyl)chlorin (temoporfin) with serum proteins: protein binding and liposome destruction

mTHPC is a non polar photosensitizer used in photodynamic therapy. To improve its solubility and pharmacokinetic properties, liposomes were proposed as drug carriers. Binding of liposomal mTHPC to serum proteins and stability of drug carriers in serum are of major importance for PDT efficacy; however, neither was reported before. We studied drug binding to human serum proteins using size-exclusion chromatography. Liposomes destruction in human serum was measured by nanoparticle tracking analysis (NTA). Inclusion of mTHPC into conventional (Foslip(®)) and PEGylated (Fospeg(®)) liposomes does not affect equilibrium serum protein binding compared with solvent-based mTHPC. At short incubation times the redistribution of mTHPC from Foslip(®) and Fospeg(®) proceeds by both drug release and liposomes destruction. At longer incubation times, the drug redistributes only by release. The release of mTHPC from PEGylated vesicles is delayed compared with conventional liposomes, alongside with greatly decreased liposomes destruction. Thus, for long-circulation times the pharmacokinetic behavior of Fospeg(®) could be influenced by a combination of protein- and liposome-bound drug. The study highlights the modes of interaction of photosensitizer-loaded nanovesicles in serum to predict optimal drug delivery and behavior in vivo in preclinical models, as well as the novel application of NTA to assess the destruction of liposomes.

In vivo quantification of photosensitizer concentration using fluorescence differential path-length spectroscopy: influence of photosensitizer formulation and tissue location

In vivo measurement of photosensitizer concentrations may optimize clinical photodynamic therapy (PDT). Fluorescence differential path-length spectroscopy (FDPS) is a non-invasive optical technique that has been shown to accurately quantify the concentration of Foscan® in rat liver. As a next step towards clinical translation, the effect of two liposomal formulations of mTHPC, Fospeg® and Foslip®, on FDPS response was investigated. Furthermore, FDPS was evaluated in target organs for head-and-neck PDT. Fifty-four healthy rats were intravenously injected with one of the three formulations of mTHPC at 0.15 mg kg(-1). FDPS was performed on liver, tongue, and lip. The mTHPC concentrations estimated using FDPS were correlated with the results of the subsequent harvested and chemically extracted organs. An excellent goodness of fit (R(2)) between FDPS and extraction was found for all formulations in the liver (R(2)=0.79). A much lower R(2) between FDPS and extraction was found in lip (R(2)=0.46) and tongue (R(2)=0.10). The lower performance in lip and in particular tongue was mainly attributed to the more layered anatomical structure, which influences scattering properties and photosensitizer distribution.

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.

Improved in vivo delivery of m-THPC via pegylated liposomes for use in photodynamic therapy

Pegylated liposomal nanocarriers have been developed with the aim of achieving improved uptake of the clinical PDT photosensitiser, m-THPC, into target tissues through increased circulation time and bioavailability. This study investigates the biodistribution and PDT efficacy of m-THPC in its standard formulation (Foscan®) compared to m-THPC incorporated in liposomes with different degrees of pegylation (FosPEG 2% and FosPEG 8%), following i.v. administration to normal and tumour bearing rats. The plasma pharmacokinetics were described using a three compartmental analysis and gave elimination half lives of 90 h, 99 h and 138 h for Foscan®, FosPEG 2% and 8% respectively. The accumulation of m-THPC in tumour and normal tissues, including skin, showed that maximal tumour to skin ratios were observed at ≤ 24 h with FosPEG 2% and 8%, whilst skin photosensitivity studies showed Foscan® induces more damage compared to the liposomes at drug-light intervals of 96 and 168 h. PDT treatment at 24h post-administration (0.05 mg kg⁻¹) showed higher tumour necrosis using pegylated liposomal formulations in comparison to Foscan®, which is attributed to the higher tumour uptake and blood plasma concentrations. Clinically, this improved selectivity has the potential to reduce not only normal tissue damage, but the drug dose required and cutaneous photosensitivity.