Atomic force microscopy is a novel method for imaging and characterization in biomedicine. However, high-resolution imaging of living samples from cells to tissues still remains a challenge. In this paper, two types of AFM working mode (contact mode and tapping mode) which are utilized for the imaging of living cells and tissues are discussed. A new magnetic tapping mode (MAC mode), which is more suitable for living samples, and a novel data collecting system named TREC, are also introduced.
近些年来，纳米铁粉（nano—scale iron particle，N—Fe）由于它们特殊的性能，正被广泛用于环境保护等领域，因此也日益引起了人们的重视。据报道，纳米铁的催化能力是微米级铁的数10倍，它还是很强的还原剂，可用于多氯联苯、滴滴涕和二氧芑等废物的降解，大多数情况下几天就可以中和生物降解方法需几年才能降解的污染物。虽然目前国内外对纳米二氧化钛、碳纳米管、C60的毒理作用及纳米铁粉的吸入毒性已有一定研究，但高浓度人造纳米铁颗粒的经口一般毒理学数据仍少之又少。我们有必要在纳米材料大量投入使用之前，就评估它对环境的潜在风险是否大于它所带来的经济效益。因此，本研究的目的就是获取纳米铁颗粒的安全性数据，
Many of the applications proposed for bioassays, scaffolds for tissue engineering, filtrations, and supports for catalysts require polymeric membranes with large specific surface areas. Polycarbonate (PC) is a possible candidate for these applications because of its excellent mechanical performance and good biocompatibility. Electrospinning is a simple and effective method for large-scale fabrication of micro-/nanofibrous membranes with large specific surface areas. How to control the morphology of electrospun PC fibers, however, has not been systematically investigated. We describe the controllable fabrication of continuous and uniform PC fibers. We electrospin PC/chloroform solutions doped with different types of surfactants including anionic, zwitterionic, nonionic and cationic surfactants. Only cationic surfactants can lead to the successful fabrication of uniform PC fibers. After the analysis of the correlation between solution properties such as viscosity, surface tension, and conductivity and the morphology of electrospun fibers, we conclude that the addition of cationic surfactants such as cetane trimethyl ammonium bromide (CTAB) that leads to a decrease in viscosity is the main factor responsible for the formation of PC fibers. The demonstration of the fabrication of uniform PC fibers will lend experience to processing other polymers into fibers via electrospinning.
YANG Da YongWANG YangZHANG DongZhouLIU YingYiJIANG XingYu
