Philippe Arnoux

Inorganic Nanoparticles for Photodynamic Therapy.

Photodynamic therapy (PDT) is a well-established technique employed to treat aged macular degeneration and certain types of cancer, or to kill microbes by using a photoactivatable molecule (a photosensitizer, PS) combined with light of an appropriate wavelength and oxygen. Many PSs are used against cancer but none of them are highly specific. Moreover, most are hydrophobic, so are poorly soluble in aqueous media. To improve both the transportation of the compounds and the selectivity of the treatment, nanoparticles (NPs) have been designed. Thanks to their small size, these can accumulate in a tumor because of the well-known enhanced permeability effect. By changing the composition of the nanoparticles it is also possible to achieve other goals, such as (1) targeting receptors that are over-expressed on tumoral cells or neovessels, (2) making them able to absorb two photons (upconversion or biphoton), and (3) improving singlet oxygen generation by the surface plasmon resonance effect (gold nanoparticles). In this chapter we describe recent developments with inorganic NPs in the PDT domain. Pertinent examples selected from the literature are used to illustrate advances in the field. We do not consider either polymeric nanoparticles or quantum dots, as these are developed in other chapters.

Stability of folic acid under several parameters

Folic acid is a small molecule, also known as vitamin B9. It is an essential compound involved in important biochemical processes. It is widely used as a vector for targeted treatment and diagnosis especially in cancer therapeutics. Nevertheless, not many authors address the problem of folic acid degradation. Several researchers reported their observations concerning its denaturation, but they generally only took into account one parameter (pH, temperature, light or O2etc.). In this review, we will focus on five main parameters (assessed individually or in conjunction with one or several others) that have to be taken into account to avoid the degradation of folic acid: light, temperature, concentration, oxygen and pH, which are the most cited in the literature. Scrupulous bibliographic research enabled us to determine two additional degradation factors that are the influence of singlet oxygen and electron beam on folic acid stability, which are not considered as among the prime factors. Although these two factors are not commonly present as compared to the others, singlet oxygen and electron beams intervene in new therapeutic technologies and must be taken in consideration for further applications such photodynamic or X-rays therapies.

Folic acid conjugates with photosensitizers for cancer targeting in photodynamic therapy: Synthesis and photophysical properties

Recent researches in photodynamic therapy have focused on novel techniques to enhance tumour targeting of anticancer drugs and photosensitizers. Coupling a photosensitizer with folic acid could allow more effective targeting of folate receptors which are over-expressed on the surface of many tumour cells. In this study, different folic acid-OEG-conjugated photosensitizers were synthesized, characterized and their photophysical properties were evaluated. The introduction of an OEG does not significantly improve the hydrophilicity of the FA-porphyrin. All the FA-targeted photosensitizers present good to very good photophysical properties. The best one appears to be Ce6. Molar extinction coefficient, fluorescence and singlet oxygen quantum yields were determined and were compared to the corresponding photosensitizer alone.

Singlet Oxygen-Mediated Oxidation during UVA Radiation Alters the Dynamic of Genomic DNA Replication

UVA radiation (320–400 nm) is a major environmental agent that can exert its deleterious action on living organisms through absorption of the UVA photons by endogenous or exogenous photosensitizers. This leads to the production of reactive oxygen species (ROS), such as singlet oxygen (1O2) and hydrogen peroxide (H2O2), which in turn can modify reversibly or irreversibly biomolecules, such as lipids, proteins and nucleic acids. We have previously reported that UVA-induced ROS strongly inhibit DNA replication in a dose-dependent manner, but independently of the cell cycle checkpoints activation. Here, we report that the production of 1O2 by UVA radiation leads to a transient inhibition of replication fork velocity, a transient decrease in the dNTP pool, a quickly reversible GSH-dependent oxidation of the RRM1 subunit of ribonucleotide reductase and sustained inhibition of origin firing. The time of recovery post irradiation for each of these events can last from few minutes (reduction of oxidized RRM1) to several hours (replication fork velocity and origin firing). The quenching of 1O2 by sodium azide prevents the delay of DNA replication, the decrease in the dNTP pool and the oxidation of RRM1, while inhibition of Chk1 does not prevent the inhibition of origin firing. Although the molecular mechanism remains elusive, our data demonstrate that the dynamic of replication is altered by UVA photosensitization of vitamins via the production of singlet oxygen.

A 5-(difluorenyl)-1,10-phenanthroline-based Ru(II) complex as a coating agent for potential multifunctional gold nanoparticles

The synthesis and photophysical properties of small gold nanoparticles (NPs, AuNP-[Ru-PFF]) surface functionalized by 5-substituted-1,10-phenanthroline-ligand based Ru(II) complexes are described. Luminescence of the grafted and confined Ru(II) complexes is totally quenched on the gold surface. Nonlinear optical properties were determined via Z-scan measurements in the range 600-1300 nm for both the free Ru(II) complex and the related NPs. In the short wavelength range (around 600 nm) the behaviour switches from that of two-photon absorption (2PA) for the complex to saturable absorption for the NPs. 2PA applications such as optical power limiting or two-photon dioxygen sensitization can be anticipated for these nanoplatforms.

Sulfamethoxazole removal from polluted water by immobilized photocatalysis

The photocatalytic activity of TiO2 deposits (Degussa P25 and Millennium PC500) has been studied using sulfamethoxazole (SMX) as a model water pollutant and a UV fluorescent lamp as a light source (365 nm). Both catalysts have shown very similar properties in the photocatalytic degradation of SMX. Special attention has been given to the effect of the irradiation time, pH, and pollutant concentration. No mass-transfer limitations are observed. The degradation of SMX is accelerated at low concentration, and the photocatalytic degradation kinetics obey the Langmuir–Hinshelwood model, allowing the adsorption and apparent rate constants to be determined for both catalysts.

A Photosensitizer Lanthanide Nanoparticle Formulation that Induces Singlet Oxygen With Direct Light Excitation, But Not By Photon or X-ray Energy Transfer

We report the design and synthesis of europium‐doped gadolinium oxysulfide nanoscintillators Gd2O2S:Eu3+ conjugated with two different photosensitizers (PSs): a zinc chlorin (ZnTPC) and a zinc phtalocyanine (ZnPc) by covalent bonding through a layer of N‐(3‐trimethoxysilylpropyl)diethylenetriamine (TPDA). These conjugates were designed to be activated under X‐ray excitation to allow a photodynamic effect, although this desired outcome was not achieved in this study. The monodispersed nanoparticles of ∼70 nm diameter were pegylated to be stabilized in aqueous suspension. It was shown that the PSs conserved their photophysical properties once conjugated to the nanoscintillator and efficient singlet oxygen was obtained upon photo‐irradiation. However, no energy transfer was observed from the nanoscintillator to the photosensitizer neither under photo‐ nor X‐ray irradiation.

Chapter 10:Production of Singlet Oxygen by Nanoparticle-Bound Photosensitizers

New improvements in the field of targeted PDT concern the use of nanoparticles that can serve as carriers for anticancer agent delivery. Nanoparticles do indeed offer many advantages such as good colloidal stability, effective protection of encapsulated drugs against enzymes and hydrolysis, surface tailor ability and multipurpose, and easy, synthesis. More importantly, thanks to their size, nanoparticles are a means to allow selective accumulation of the PS in cancer cells due to the enhanced permeability and retention effect of tumor tissues. In this chapter, we will focus on the production of singlet oxygen (1O2*) after excitation of PS coupled or encapsulated into nanoparticles possessing a three-dimensional rigid matrix. We define three types of nano-objects: nanoparticles in which the ΦΔ of photosensitizers increases compared to free photosensitizers, nanoparticles in which the ΦΔ of the encapsulated PS decreases compared to ΦΔ of the free photosensitizer and systems in which ΦΔ of the encapsulated or free PS are similar.

Polymer-lipid-PEG hybrid nanoparticles as photosensitizer carrier for photodynamic therapy

Polymer-lipid-PEG hybrid nanoparticles were investigated as carriers for the photosensitizer (PS), 5,10,15,20-Tetrakis(4-hydroxy-phenyl)-21H,23H-porphine (pTHPP) for use in photodynamic therapy (PDT). A self-assembled nanoprecipitation technique was used for preparing two types of core polymers poly(d,l-lactide-co-glycolide) (PLGA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with lipid-PEG as stabilizer. The resulting nanoparticles had an average particle size of 88.5±3.4nm for PLGA and 215.0±6.3nm for PHBV. Both nanoparticles exhibited a core-shell structure under TEM with high zeta potential and loading efficiency. X-ray powder diffraction analysis showed that the encapsulated pTHPP molecules in polymeric nanoparticles no longer had peaks of free pTHPP in the crystalline state. The pTHPP molecules encapsulated inside the polymeric core demonstrated improved photophysical properties in terms of singlet oxygen generation and cellular uptake rate in a FTC-133 human thyroid carcinoma cell line, compared to non-encapsulated pTHPP. The pTHPP-loaded polymer-lipid-PEG nanoparticles showed better in vitro phototoxicity compared to free pTHPP, in both time- and concentration-dependent manners. Overall, this study provides detailed analysis of the photophysical properties of pTHPP molecules when entrapped within either PLGA or PHBV nanoparticle cores, and demonstrates the effectiveness of these systems for delivery of photosensitizers. The two polymeric systems may have different potential benefits, when used with cancer cells. For instance, the pTHPP-loaded PLGA system requires only a short time to show a PDT effect and may be suitable for topical PDT, while the delayed photo-induced cytotoxic effect of the pTHPP-loaded PHBV system may be more suitable for cancer solid tumors. Hence, both pTHPP-encapsulated polymer-lipid-PEG nanoparticles can be considered promising delivery systems for PDT cancer treatment.

New photodynamic molecular beacons (PMB) as potential cancer-targeted agents in PDT

Further improvements in Photodynamic therapy (PDT) necessitate that the dye targets more selectively tumour tissues or neovascularization than healthy cells. Different enzymes such as matrix metalloproteinases (MMPs) are overexpressed in tumour areas. Among these MMPs, gelatinases (MMP-2 and MMP-9) and its activator MMP-14 are known to play a key role in tumour angiogenesis and the growth of many cancers such as glioblastoma multiforme (GBM), an aggressive malignant tumour of the brain. These last years, the concept of photodynamic molecular beacons (PMB) became interesting for controlling the photosensitizers ability to generate singlet oxygen (1O2) close to target biomolecules as MMPs. We report herein novel PMBs triggered by MMP-2 and/or MMP-9 and/or MMP-14, comprising a photosensitizer and a singlet oxygen quencher linked by MMP cleavable peptide linker (H-GRIGFLRTAKGG-OH). First of all, we focused on the synthesis and the photophysical study of different derivatives photosensitizer-peptide. This preliminary work concluded on an influence of the nature and the distance from the peptide, but not of the position of the photosensitizer in these derivatives on the proteolytic enzymatic action. The nature of the quencher used (a blackberry quencher (BBQ-650) or a black hole quencher (BHQ3)) does not influence the enzymatic action. We also studied the influence of an additional PEG spacer. Finally, the synthesis, the singlet oxygen quenching efficiency and the enzymatic activation of these new MMP- cleavable-PMBs were compared.