Synthesis of Novel Magnesium-Doped Hydroxyapatite/Chitosan Nanomaterial and Mechanisms for Enhanced Stabilization of Heavy Metals in Soil

A novel magnesium-doped hydroxyapatite/chitosan nanomaterial (MHAP@CS) was prepared as soil passivator for treatment of copper and cadmium contaminated soil. The mechanism of the immobilization performance improvement was proposed. According to the characterization, magnesium ions were successfully incorporated into hydroxyapatite (HAP), and chitosan (CS) was also supported on HAP. Toxicity characteristic leaching procedure (TCLP) and Tessier sequential extraction method were conducted to evaluate the immobilization efficiency of MHAP@CS, and MHAP@CS showed higher efficiency in the reduction of the mobility of Cu and Cd than HAP. Meanwhile, adsorption experiments and XPS characterization were used to investigate the passivation mechanism. The maximum removal amount of MHAP@CS for Cu(II) and Cd(II) was 133.49 mg g^?1 and 131.84 mg g^?1 respectively. According to XPS and Zeta potential, the stabilization of Cu(II) and Cd(II) by MHAP@CS involved ion exchange, electrostatic adsorption and surface complexation. After magnesium doping and CS modification, the electronegativity and ion exchange capacity of HAP were significantly improved. The excellent immobilization performance suggested that MHAP@CS is an effective, green and facile soil passivator.

     

Dynamically Reconstructed Collagen Fibers for Transmitting Mechanical Signals to Assist Macrophages Tracing Breast Cancer Cells

Constructing proper in vitro tumor immune microenvironment (TIME) is important for cancer immune-therapy studies, while the selection of biomaterials is critical. As innate immune cells, macrophages can target and kill cancer cells in vivo at the early stage of tumor development. However, this targeting phenomenon has not been observed in vitro. Herein, a quasi-3D in vitro cell culture model is constructed to mimic TIME by integrating hydrogel collagen as extracellular matrix for cells. In the collagen-based quasi-3D in vitro system, for the first time, it is found that macrophages can be attracted toward cancer cells along the dynamically reconstructed collagen fibers. By combining traction force microscopy and customized micro-manipulator system, it is revealed that the collagen matrix-transmitted tensile force signaling precisely guides the migration of macrophages toward cancer cells. The mechano-responsiveness mechanism is related to the activation of mechanosensitive ion channels, and the induced local increase of calcium signal, which is proved to enhance the F-actin assembly and to guide the cell migration. This novel mechanism advances the understanding of the role of collagen fibers in mechanotaxis of macrophages. Taken together, it has great potential for assisting biomaterial designs in developing new drug-screening models and clinical strategies for cancer immune-therapy.