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.

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.

Systems biology approach for in vivo photodynamic therapy optimization of ruthenium-porphyrin compounds.

Two arene ruthenium porphyrin compounds showing interesting photodynamic activity in vitro, [Ru(η(6)-p-Pr(i)C(6)H(4)Me)(PMP)Cl(2)] (PMP=5-(3-pyridyl)-10,15,20-triphenylporphyrin) and [Ru(4)(η(6)-p-Pr(i)C(6)H(4)Me)(4)(PTP)Cl8] (PTP=5,10,15,20-tetra(3-pyridyl)porphyrin) coined Rut1 and Rut4 respectively, have been evaluated in vivo. Porphyrins alone and the arene ruthenium porphyrin derivatives (Rut1 and Rut4) showed comparable spectroscopic and photophysical properties. The in vivo study consisted in selecting the optimal arene ruthenium porphyrin photosensitizer by using an original experimental design approach on mice bearing an ectopic human oral carcinoma xenograft. The model of experimental design demonstrated to be well suited to the empirical model-building of photodynamic therapy (PDT) response. Arene ruthenium porphyrins concentration and fluence level demonstrated no statistically significant influence on the tumor growth. On the contrary, the presence of ruthenium groups improved the in vivo photodynamic efficiency. By optical fiber fluorimetry, we demonstrated that both compounds exhibited enhanced accumulation in KB tumors from 24h to 96 h post-intravenous injection. These experiments were completed by inductively coupled plasma mass spectrometry quantification of ruthenium in different organs including tumor tissue. Despite a statistically significant in vivo photodynamic efficiency for Rut4, cellular localization in human oral carcinoma KB cells using fluorescence microscopy demonstrated that both conjugates Rut1 and Rut4 accumulated only in cytoplasm of KB cells but not in the nucleus.

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.

Optimization and characterization of liposome formulation by mixture design.

This study presents the application of the mixture design technique to develop an optimal liposome formulation by using the different lipids in type and percentage (DOPC, POPC and DPPC) in liposome composition. Ten lipid mixtures were generated by the simplex-centroid design technique and liposomes were prepared by the extrusion method. Liposomes were characterized with respect to size, phase transition temperature, ζ-potential, lamellarity, fluidity and efficiency in loading calcein. The results were then applied to estimate the coefficients of mixture design model and to find the optimal lipid composition with improved entrapment efficiency, size, transition temperature, fluidity and ζ-potential of liposomes. The response optimization of experiments was the liposome formulation with DOPC: 46%, POPC: 12% and DPPC: 42%. The optimal liposome formulation had an average diameter of 127.5 nm, a phase-transition temperature of 11.43 °C, a ζ-potential of -7.24 mV, fluidity (1/P)(TMA-DPH)((¬)) value of 2.87 and an encapsulation efficiency of 20.24%. The experimental results of characterization of optimal liposome formulation were in good agreement with those predicted by the mixture design technique.

Redistribution of meta-tetra(hydroxyphenyl)chlorin (m-THPC) from conventional and PEGylated liposomes to biological substrates.

We used the phenomenon of previously described photoinduced fluorescence quenching and fluorescence polarization to evaluate the transfer of meta-tetra(hydroxyphenyl)chlorin (m-THPC) from commercial high-drug load liposomes to plasma proteins and model membranes. Fluorescence quenching of m-THPC in liposomes by iodide indicates that part of m-THPC in PEGylated liposomes is localized in the PEG shell, while the rest is bound to the lipid bilayer. It was shown that the two molecule pools in the commercial PEGylated liposomal formulation Fospeg® condition the characteristics of the m-THPC release kinetics. A substantial percentage of m-THPC from Fospeg® is released much faster than from the conventional liposomal formulation Foslip®. Using the technique of resonance light scattering, it was shown that partial m-THPC aggregation is present in liposomes with very high drug loads, higher in PEGylated liposomes compared to conventional ones.