Performance of 3D printing biomimetic conch shell and pearl shell hybrid design composites under quasi-static three-point bending load.

The failure process of biomimetic hybrid design composite composed of layers of conch shell and pearl shell was studied through quasi-static three-point bending experiments and numerical simulations. The biomimetic conch shell structure with inclined angles serves as the upper layer of the hybrid structure, while the biomimetic pearl shell structure with traditional brick and mud structure serves as the lower layer of the hybrid structure, forming a hybrid design structure. Four inclined angles were designed for the structural units of the conch shell, namely 15°, 30°, 45°, and 60°. Twenty-four specimens (six specimens for each inclined angle) were prepared using 3D printing technology using both soft and hard matrix materials. The influence of different inclined angles on the fracture strength, fracture toughness, and energy absorption of hybrid design structures was experimentally studied. The biomimetic hybrid design composite specimen with a notch is placed between two supporting rollers, and a loading indenter acts at mid-span. All twenty-four specimens were notched with a triangular tip and a rectangular bottom. A loading rate of 1 mm/min is used to avoid the viscoelastic effect of the composite materials. Details of the specimens, the experimental set-up and procedure are discussed in this paper. Complementary to the experimental studies, an extensive numerical investigation was carried out to study the influence of the aspect ratio of brick and mud units on the fracture initiation and failure of hybrid design structures. The causes of crack initiation and propagation, and failure modes in biomimetic hybrid design structures were postulated. These numerical findings help in reinforcing the experimental results and provide crucial information to enhance further research in this exciting area.

Research on the establishment of a TPM3 monoclonal stable transfected PANC-1 cell line and the experiment of the EMT occurrence in human pancreatic cancer.

Background: Pancreatic cancer is one of the most aggressive human malignancies that is associated with early metastasis and chemoresistance. Tropomyosin (TPM) is an indispensable regulatory protein for muscle contraction, Abnormal expressions of TPM gene are closely related to the carcinogenesis and metastasis of malignant tumors. Purpose: In this experiment, a monoclonal stable transfected cell line was established by the knock-down of TMP3 expression in PANC-1 cells with the lentivirus method, and the impacts of the downregulated TPM3 gene expression on the EMT-related molecules and biological behaviors of PANC-1 cells were explored. Methods: Based on the TPM3 gene sequence, we designed the RNA interference sequence, constructed and screened out the recombinant plasmid segment TPM3-shRNA with the optimal silencing effect, and carried out lentivirus titer determination and packaging. The recombinant lentiviral interference vector LV-TPM3-shRNA was transfected into PANC-1 cells; the transfection efficiency was then evaluated to screen out the monoclonal stable transfected PANC-1 cell line with downregulated TPM3 expression. The qRT-PCR and Western blot were used to detect the changes in the gene- and protein-levels expressions of EMT-related transcription factors in the target cell line and to respectively test the variations of the invasion and proliferation capacities. Results: It is shown that the monoclonal stable transfected PANC-1 cell line with downregulated TPM3 expression was successfully established with the recombinant lentiviral vector. After knocking down the expression of TPM3 gene in PANC-1 cells, EMT occurred in the cells; the cell phenotype showed malignant transformation, and the in vitro biological behaviors of the cells (such as proliferation and invasion) were enhanced to different degrees. Conclusion: It is indicated that the TPM3 gene can be a potential target spot for the treatment of pancreatic cancer.

Osteogenic Ability Detection of Human Bone Morphogenetic Protein-2 Gene-activated Nano Bone Putty by Reusable Double-Cavity Bone Harvest Chamber.

OBJECTIVE: To explore the feasibility of implanting a self-designed reusable double-cavity bone harvest chamber into Guizhou mini-pigs for observation of the osteogenic effect of human bone morphogenetic protein-2 (hBMP-2) gene-activated nano bone putty on bone in growth. METHODS: Eight healthy 12-month-old female Guizhou mini-pigs were used for the present experiment. In the first operation, empty double-cavity bone harvest chambers (n = 8) were implanted into the femoral metaphysis of the animals as a blank control group. In the second operation, the femoral metaphyses were implanted with the chambers filled by the nano bone putty+hBMP-2 plasmid in one cavity and nothing in the other cavity, respectively (experiment group, n = 8). The time interval between every operation was 3 months. The cavity materials were retrieved and replaced for assessment by gross observation, histological examination, and bone morphology metrology analysis to compare osteogenesis ability and alkaline phosphatase. RESULTS: Three months after surgery, the nano bone putty+hBMP-2 plasmid in one cavity of the chambers had hard gray and white tissues inside, while the cavities pre-installed with nothing were filled with soft brown tissues. Light microscopy showed new generated bone tissue around the filled material, but only fibrous tissues in the empty cavities. Osteogenesis ability and alkaline phosphatase of the nano bone putty+hBMP-2 plasmid group were significantly higher than those of the blank control group (P < 0.05). CONCLUSION: The reusable double-cavity bone harvest chamber can be used to observe the osteogenic potential of the hBMP-2 gene-activated nano bone putty.

Mitochondrial genome of a spontaneous multiple myeloma bone cancer model mouse C57BL/KaLwRij strain.

We sequenced the complete mitochondrial genome of a multiple myeloma bone cancer model mouse C57BL/KaLwRij strain for the first time. The total length of the mitogenome was 16,297 bp, with 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes. This mitochondrial genome sequence contains 127 SNPs compared with the house mouse reference sequence.

Controlled MoS2 layer etching using CF4 plasma.

A few-layered molybdenum disulfide (MoS2) thin film grown by plasma enhanced chemical vapor deposition was etched using a CF4 inductively coupled plasma, and the possibility of controlling the MoS2 layer thickness to a monolayer of MoS2 over a large area substrate was investigated. In addition, damage and contamination of the remaining MoS2 layer surface after etching and a possible method for film recovery was also investigated. The results from Raman spectroscopy and atomic force microscopy showed that one monolayer of MoS2 was etched by exposure to a CF4 plasma for 20 s after an initial incubation time of 20 s, i.e., the number of MoS2 layers could be controlled by exposure to the CF4 plasma for a certain processing time. However, XPS data showed that exposure to CF4 plasma induced a certain amount of damage and contamination by fluorine of the remaining MoS2 surface. After exposure to a H2S plasma for more than 10 min, the damage and fluorine contamination of the etched MoS2 surface could be effectively removed.