| Osteoporosis is a common degenerative disease that causes bones to become abnormally thin, easily fragile, and more likely to fracture due to an imbalance in bone absorption and replacement.To prevent and cure bone loss, there are medications available to reduce the risk of broken bones. These medicines either slow or stop bone loss or rebuild bones. Most current osteoporosis treatments are anti-resorptive, inhibiting osteoclastic bone resorption but not promoting new bone formation.Statins, especially simvastatin(SIM), in tissue culture and in rat and mouse models, have been shown to be potent compounds that increase BMP-2 mRNA expression in osteoblasts and inducing osteoblast activity leading to new bone formation.The administration of statins generally includes oral administration, multiple local injections into lesions, and delivery with, specific devices. The statin concentration produced at local sites through oral administration is too low for bone formation. Multiple injections of statin can augment osteoblastic function, increase new bone formation, and reduce soft tissue swelling. However, it is not suitable for the systemic disease such as Osteoporosis. Therefore, a suitable delivery device will be more beneficial for patients.The study is to construct a compatibility nanoparticle base on poly (lactic-co-glycolic acid) (PLGA), with the tetracycline targeting grafted, to realize the effective delivery of drug SIM to bone. The TC-PLGA2000 was successfully synthesized by direct conjugation of COOH of PLGA with OH of TC via esterification reaction. The product was evaluated by 1H NMR spectroscopy. The results indicate that the synthesis of the TC-PLGA was successful. PLGA NPs and TC-PLGA NPs were prepared by the solvent emulsification method. The size of PLGA NPs, TC-PLGA NPs, SIM/PLGA NPs and SIM/PLGA NPs are all about 200nm and the TC-graft had no significant effect on size. Transmission electron microscopy (TEM) presents the TEM images of blank and SIM loaded NPs, indicating the nanoparticles of spherical morphology, with average sizes similar to those obtained by dynamic light scattering. The entrapment efficiency (EE%) of SIM/PLGA NPs and SIM/TC-PLGA NPs was above 75%. The TC-grafled had no significant effect on EE%. The drug release behavior of PLGA NPs was similar with that of TC-PLGA NPs. The TC would be considered to negligibly interfere with the drug release. After 72 h, the cumulative drug released percentage reached 80%."With the murine nontransformed osteoblast-like cell (MC3T3-E1) as model cells, in vitro cellular uptake results showed, the PLGA NPs and TC-PLGA NPs had excellent internalization ability and could reduce the cytotoxiciry of drug at high concentration. We tested the effect of SIM/NPs on osteoblast differentiation as evidenced by mineralization. SIM/NPs treatment yielded increased in cell mineralization over that of the differentiation medium-treated cells and with the increase of concentration increase. The TC would be considered to negligibly interfere with the osteogenic differentiation.The adhesion between bone-like substrates and bone-targeting NP was demonstrated in vitro with the hydroxyapatite powder. The data presented demonstrated that the proportion of the TC-PLGA NPs bound to HAp (87.94%) was greater than the bound proportion of PLGA NPs (18.59%). The bone-targeting capacities of PLGA NPs and TC-PLGA NPs labeled with DiR lipophilicity fluorescence dye were evaluated in vivo using ICR mice. The tissue distributions of the fluorescence intensities clearly indicate that 80.5% more DiR/TC-PLGA NPs were present in the femur and tibia than in the case of the DiR/PLGA NPs. Meanwhile TC-PLGA NPs can reduce NPs trapping in liver and spleen, despite the relatively small differences in size being obtained between PLGA NPs and TC-PLGA NPs. The in vivo pharmacodynamics results showed that SIM/TC-PLGA NPs treatment could effectively increase the bone mineral density compared with the same dose of SIM or SIM/PLGA NPs. |
