Preparation of Poly[lactic-co-glycolic] Acid Nanospheres and Its Role in Hepatoma Cells.

Poly[lactic-co-glycolic] acid (PLGA) targeting nanoparticles AFP/PLGA/Dt386, loaded with Dt386 plasmid of diphtheria toxin gene, modified by Alpha fetoprotein (AFP) monoclonal antibody, is prepared. Its physical and chemical properties and its effect on HepG2 cells are studied. Firstly, Dt386 expression plasmid pET11a/Dt386 is constructed and PLGA nanoparticles are prepared by emulsion solvent evaporation (ESE). Scanning electron microscope (SEM) is used to observe its morphology. Laser Particle Sizer is used to measure the particle size. In addition, the encapsulation efficiency, drug loading and in vitro release rate of PLGA nanoparticles are measured. Carboxy fluorescein and rhodamine fluorescein are used to double label IgG/PLGA/Dt386 and AFP/PLGA/Dt386 nanospheres, respectively, the entry of nanospheres into HepG2 cells are observed at 3 h and 12 h. The effect of AFP/PLGA/Dt386 nanospheres on the migration of HepG2 cells is examined by wounding healing assay. Transwell chamber experiment is used to detect the effect of AFP/PLGA/Dt386 nanospheres on the invasion of HepG2 cells. MTT method is utilized to determine the inhibitory activity of nanoparticles on HepG2 cell proliferation. After treated with IgG/PLGA/Dt386 and AFP/PLGA/Dt386 nanoparticles for 48 hours, flow cytometry is used to detect the apoptosis rate and cell cycle of HepG2 cells in each group. The results show that the prepared nanospheres have regular morphology, flat surface, average particle size of 265.72±12.46 nm, zeta potential of -18.15 mV. The average entrapment efficiency and drug loading are 78.48±1.71% and 3.16±0.35%, respectively. The nanoparticles release slowly and stably in vitro. At the 10th day, the release rate reaches 75.13%. PLGA nanospheres can effectively protect DNA from nuclease degradation. The results show that AFP/PLGA/Dt386 nanospheres have biological targeting effect and can be enriched in cells. AFP/PLGA/Dt386 nanoparticles can significantly inhibit the migration, invasion and proliferation of HepG2 cells, and promote apoptosis.

Novel standardized massive bone defect model in rats employing an internal eight-hole stainless steel plate for bone tissue engineering.

Massive bone defects are a challenge in orthopaedic research. Defective regeneration leads to bone atrophy, non-union of bone, and physical morbidity. Large animals are important models, however, production costs are high, nursing is complex, and evaluation methods are limited. A suitable laboratory animal model is required to explore the underlying molecular mechanism and cellular process of bone tissue engineering. We designed a stainless steel plate with 8 holes; the middle 2 holes were used as a guide to create a standardized critical size defect in the femur of anaesthetized rats. The plate was fixed to the bone using 6 screws, serving as an inner fixed bracket to secure a tricalcium phosphate implant seeded with green fluorescent protein-positive rat bone marrow mesenchymal stem cells within the defect. In some animals, we also grafted a vessel bundle into the lateral side of the implant, to promote vascularized bone tissue engineering. X-ray, microcomputed tomography, and histological analyses demonstrated the stainless steel plate resulted in a stable large segmental defect model in the rat femur. Vascularization significantly increased bone formation and implant degradation. Moreover, survival and expansion of green fluorescent protein-positive seeded cells could be clearly monitored in vivo at 1, 4, and 8 weeks postoperation via fluorescent microscopy. This standardized large segmental defect model in a small animal may help to advance the study of bone tissue engineering. Furthermore, availability of antibodies and genetically modified rats could help to dissect the precise cellular and molecular mechanisms of bone repair.