Study of the pO2-Sensitivity of the Dendrimeric and Free Forms of Pd-meso-tetra(4-carboxyphenyl)porphyrin, Incorporated or not in Chitosan-Based Nanoparticles

The concentration of oxygen and its rate of consumption are important factors in certain medical treatments, such as radiotherapy and photodynamic therapy (PDT). Measuring the tissue concentration of oxygen or its partial pressure (pO2) can be achieved by taking advantage of the oxygen-dependent luminescence lifetime of certain molecules, including metallo-porphyrin derivatives, due to the oxygen-dependent quenching of their triplet state. Unfortunately, most of these porphyrin derivatives are phototoxic due to the O21? produced in the pO2 measurement procedure. The aim of this work was to characterize new nanoparticle oxygen sensors, where the palladium-porhyrin molecule (Pd-meso-tetra(4-carboxyphenyl)porphyrin) or its dendrimer form, is incorporated into an oxygen permeable matrix of chitosan-based colloidal particles. It was hypothesized that the reactive O21? produced during the pO2 measurement would react inside the particle thus reducing its toxicity for the surrounding tissue, whereas the 3? ground state of O2, that is to be measured, would diffuse freely in the peptide. We observed that the incorporation of the porphyrin in the nanoparticles resulted in a reduction of the phosphorescence lifetime sensitivity to pO2 by about one order of magnitude. Our studies of these new sensors indicate that the oxygen concentration can be measured in aqueous solutions with a precision of ±20% for oxygen concentrations ranging between 0% and 25%

Chitosan-based nanogels for selective delivery of photosensitizers to macrophages and improved retention in and therapy of articular joints.

Macrophages play key roles in inflammatory disorders. Therefore, they are targets of treatments aiming at their local destruction in inflammation sites. However, injection of low molecular mass therapeutics, including photosensitizers, in inflamed joints results in their rapid efflux out of the joints, and poor therapeutic index. To improve selective uptake and increase retention of therapeutics in inflamed tissues, hydrophilic nanogels based on chitosan, of which surface was decorated with hyaluronate and which were loaded with one of three different anionic photosensitizers were developed. Optimal uptake of these functionalized nanogels by murine RAW 264.7 or human THP-1 macrophages as models was achieved after <4h incubation, whereas only negligible uptake by murine fibroblasts used as control cells was observed. The uptake by cells and the intracellular localization of the photosensitizers, of the fluorescein-tagged chitosan and of the rhodamine-tagged hyaluronate were confirmed by fluorescence microscopy. Photodynamic experiments revealed good cell photocytotoxicity of the photosensitizers entrapped in the nanogels. In a mouse model of rheumatoid arthritis, injection of free photosensitizers resulted in their rapid clearance from the joints, while nanogel-encapsulated photosensitizers were retained in the inflamed joints over a longer period of time. The photodynamic treatment of the inflamed joints resulted in a reduction of inflammation comparable to a standard corticoid treatment. Thus, hyaluronate-chitosan nanogels encapsulating therapeutic agents are promising materials for the targeted delivery to macrophages and long-term retention of therapeutics in leaky inflamed articular joints