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 b 4 h 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.

Background: Photodynamic therapy (PDT) with Metvix® is a good therapeutic option to treat actinic keratosis, but it presents drawbacks (pain, lesion recurrences, heterogeneous outcome), emphasizing the possible need to individualize treatment. Objective: We assessed whether PDT clinical outcome and pain during treatment were correlated with protoporphyrin IX fluorescence intensity and photobleaching. Methods: 25 patients were treated by Metvix PDT. The outcome was evaluated after 1.3 (±0.4), 7.6 (±1.8), 13.2 (±1.2) and 33.6 (±3.0) months. After administration of Metvix, red light (632 ± 10 nm) was delivered with a light-emitting diode panel device. The outcome was assessed on a cosmetoclinical scale. Results: All patients who showed a fluorescence level before PDT treatment above a certain threshold had a complete recovery at 33.6 (±3.0) months. Conclusion: Our approach could be used to individualize PDT treatment based on the pretreatment fluorescence level, and to predict its long-term outcome.

Aliphatic and ethylene glycol esters of 5-aminolevulinic acid (ALA) are very efficient precursors of the photosensitizer protoporphyrin IX (PpIX) for photodynamic therapy; however, they diffuse passively across the cell membrane and thus lack cell selectivity. We evaluated whether alpha-glucose, alpha-mannose, or beta-galactose esters of ALA would present improved properties as precursors of PpIX. Esterification was performed either at the position O-1 or O-6 of the sugars with or without an ethylene glycol linker, and these glycoside esters of ALA were evaluated in human cells. The results demonstrated that glycoside esters of ALA are efficient precursors of PpIX in human cancer and angiogenic endothelial cells, comparable to free ALA, but not in normal human fibroblasts. PpIX production was confirmed by fluorescence microscopy and photodynamic treatment of cells. The O-1 or O-6 positions of functionalization and the nature of the sugar moiety did not influence PpIX production. The presence of the ethylene glycol linker generally resulted in decreased PpIX production. The uptake of these glycoside esters of ALA by cells was not decreased in the presence of high concentrations of the related sugars. Inhibitors of alpha-glucosidases or alpha-mannosidases did not decrease PpIX production. These results suggest the involvement of active non-glycoside-specific membrane transporter(s) for uptake and of esterases rather than glycosidases in the release of ALA from the glycoside esters of ALA.

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Photodynamic therapy (PDT) is a promising therapeutic modality that utilizes a combination of a photosensitizer and visible light for the destruction of diseased tissues. Using human-pigmented melanoma cells, we examined the photokilling efficacy of new silicon-phthalocyanines (SiPc) that bore bulky axial substituents. The bis(cholesteryloxy) derivate (Chol-O-SiPc) displayed the best in vitro photokilling efficacy (LD(50) = 6-8 x 10(-9) M) and was seven to nine times more potent than chloro-aluminium Pc (ClAlPc), a known photosensitizer used as a reference. Although Chol-O-SiPc was half as potent as ClAlPc for promoting photo-oxidative membrane damage in a cell-free assay, early events of mitochondrion-mediated apoptosis upon PDT were triggered much faster, as demonstrated by kinetics studies examining cells with permeabilized mitochondrial membranes, cytochrome c release and caspase-9 activation. Inhibition of caspase-9 activity by a substrate analogue argued for its central role in the proapoptotic events leading to cell death by Chol-O-SiPc PDT. In addition, immunoblots showed that Bcl-2 antiapoptotic oncoprotein was not a primary target of Chol-O-SiPc in M3Dau cells treated with PDT. Conclusively, Chol-O-SiPc is a useful new photosensitizer with the property of triggering cell apoptosis mediated by mitochondria.