Therapeutic potential of nanoparticulate systems for macrophage targeting.

The use of non-viral nanoparticulate systems for the delivery of therapeutic agents is receiving considerable attention for medical and pharmaceutical applications. This increasing interest results from the fact that these systems can be designed to meet specific physicochemical requirements, and they display low toxic and immunogenic effects. Among potential cellular targets by drug-loaded nanoparticles, macrophages are considered because they play a central role in inflammation and they act as reservoirs for microorganisms that are involved with deadly infectious diseases. The most common and potent drugs used in macrophage-mediated diseases treatment often induce unwanted side effects, when applied as a free form, due to the necessity of high doses to induce a satisfactory effect. This could result in their systemic spreading, a lack of bioavailability at the desired sites, and a short half-life. Therefore, the use of drug-loaded nanoparticles represents a good alternative to avoid, or at least decrease, side effects and increase efficacy. In this manuscript, we present an overview of the usefulness of nanoparticles for macrophage-mediated therapies in particular. We discuss, though not exhaustively, the potential of therapeutic agent-loaded nanoparticles for some macrophage-mediated diseases. We also underline the most important parameters that affect the interaction mechanisms of the macrophages and the physicochemical aspects of the particulate systems that may influence their performance in macrophage-targeted therapies.

Metalloproteinase and cytokine production by THP-1 macrophages following exposure to chitosan-DNA nanoparticles.

The use of nanoparticles for gene therapy is gaining more and more interest for medical applications. Chitosan is among the candidate polymers that have a potential application as a gene delivery system. Before using chitosan-DNA nanoparticles in vivo, one must study their interaction and cell's behavior. Since macrophages play an important role in inflammatory processes, this study was performed to investigate the effects of chitosan-DNA nanoparticles on human THP-1 cell line. Cytokine (TNF-alpha, IL-1beta, IL-6 and IL-10) and metalloproteinase (MMP-2 and MMP-9) release as well as their inhibitors (TIMP-1 and TIMP-2) were assessed after time course incubation with different amount of nanoparticles. Their secretion was quantified by enzyme-linked immunosorbent assay. Gelatinolytic activity of MMP-2 and MMP-9 was determined by zymography in cell supernatants and lysates. Cytokine secretion was not detected even in the presence of high amount of nanoparticles. On the contrary, the secretion of MMP-9 in cell supernatants increased significantly after 24 and 48 h in comparison with non-treated cells. MMP-2 secretion was augmented only after 48 h for the highest concentrations of nanoparticles (10 and 20 microg/ml DNA content). However, zymography studies showed that the secreted MMPs were in the proactive forms, while the active form of MMP-9, but not MMP-2, was detected in cell lysates when 10 and 20 microg/ml DNA containing nanoparticles were used. In conclusion, exposure of THP-1 macrophages to Ch-DNA nanoparticles did not induce release of proinflammatory cytokines. The presence of active MMP-9 within the macrophages could possibly be related to nanoparticle phagocytosis and degradation rather than to inflammatory reactions.

In vitro cytotoxicity evaluation of a 50.8% NiTi single crystal.

To our knowledge, the biocompatibility of nickel-titanium (NiTi) single crystals has not been reported. Yet certain orientations of single crystals present several advantages over the polycrystalline form in terms of maximal strain, fatigue resistance, and temperature range of superelasticity. Therefore we tested the in vitro biocompatibility of 50.8% NiTi single crystals in the orientation <001> after four different heat treatments in a helium atmosphere followed by mechanical polishing. The study was performed on the material extracts after immersion of the specimens in cell culture medium (DMEM) for 7 days at 37 degrees C. Cytotoxicity studies were performed on L-929 mouse fibroblasts using the MTT assay. J-774 macrophages were used to assess the potential inflammatory effect of the extracts by IL1-beta and TNF-alpha dosages (sandwich ELISA method). Exposure of L-929 to material extracts did not affect cell viability. In addition, IL1-beta and TNF-alpha secretion was not stimulated after incubation with NiTi extracts compared to the negative controls. These results were predictable since atomic absorption spectroscopy did not detect nickel ions in the extracts with a resolution of 1 ppm. Within the limits of in vitro testing, our results demonstrate that the TiNi(50.8%) single crystals do not trigger a cytotoxic reaction.

Mesenchymal stem cells, MG63 and HEK293 transfection using chitosan-DNA nanoparticles.

Chitosan-DNA nanoparticles were synthesized from the complexation of the cationic polymer with a ss-gal DNA plasmid, in order to study the efficacy of chitosan to develop a non-viral gene delivery system that can be optimized for efficient gene therapy. The optimal binding conditions were determined with the fluorescamine and PicoGreen assays. DNA distribution within the nanoparticle was visualized by electron transmission microscopy, while the size and morphology were assessed by atomic force microscopy. The transfection potential was evaluated for the first time on human mesenchymal stem cells (MSCs), on human osteosarcoma cells (MG63) and on human embryonic kidney cells (HEK293). The LipofectAMINE(TM) 2000 (LF) reagent was used in comparison. The effect of chitosan-DNA nanoparticles on cell viability was illustrated with the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. The nanoparticles formed are of a diameter inferior to 100nm with a homogenous distribution of DNA. The transfection of HEK293 cells is superior to that seen with MG63 cells and MSCs, however not surpassing that seen with LF. Minimal cytotoxicity is seen with the polyplexes compared to greater than 50% toxicity with LF. These results suggest that chitosan-DNA nanoparticles have favorable characteristics for non-viral gene delivery, are cell type dependent and not cytotoxic.

Natural coral exoskeleton as a bone graft substitute: a review.

Natural coral graft substitutes are derived from the exoskeleton of marine madreporic corals. Researchers first started evaluating corals as potential bone graft substitutes in the early 1970s in animals and in 1979 in humans. The structure of the commonly used coral, Porites, is similar to that of cancellous bone and its initial mechanical properties resemble those of bone. The exoskeleton of these high content calcium carbonate scaffolds has since been shown to be biocompatible, osteoconductive, and biodegradable at variable rates depending on the exoskeleton porosity, the implantation site and the species. Although not osteoinductive or osteogenic, coral grafts act as an adequate carrier for growth factors and allow cell attachment, growth, spreading and differentiation. When applied appropriately and when selected to match the resorption rate with the bone formation rate of the implantation site, natural coral exoskeletons have been found to be impressive bone graft substitutes. The purpose of this article is to review and summarize all the pertinent work that has been published on natural coral as a bone graft including in vitro, animal and clinical human studies. Preliminary report of our own experiments as well as our recommendations on the use of coral are also included.