Delivering quantum dots into cells: strategies,progress and remaining issues

The use of semiconductor quantum dots (QDs) in biological sensing and labeling continues to grow with each year. Current and projected applications include use as fluorescent labels for cellular labeling, intracellular sensors, deep-tissue and tumor imaging agents, sensitizers for photodynamic therapy, and more recently interest has been sparked in using them as vectors for studying nanoparticle-mediated drug delivery. Many of these applications will ultimately require the QDs to undergo targeted intracellular delivery, not only to specific cells, but also to a variety of subcellular compartments and organelles. It is apparent that this issue will be critical in determining the efficacy of using QDs, and indeed a variety of other nanoparticles, for these types of applications. In this review, we provide an overview of the current methods for delivering QDs into cells. Methods that are covered include facilitated techniques such as those that utilize specific peptide sequences or polymer delivery reagents and active methods such as electroporation and microinjection. We critically examine the benefits and liabilities of each strategy and illustrate them with selected examples from the literature. Several important related issues such as QD size and surface coating, methods for QD biofunctionalization, cellular physiology and toxicity are also discussed. Finally, we conclude by providing a perspective of how this field can be expected to develop in the future.     

双级微结构上二氧化硅粒子对微注压成型PP表面润湿特性的影响

提出一种柔性复制法,采用微注射压缩(μ-ICM)成型具有微拓扑结构的仿生聚丙烯(PP)表面.通过复制模板上的双级微结构,所成型的PP材料表面上呈现具有锥形顶面的双级微结构,即微棱和高纵横比的微锥体.由于微锥体之间的间隙较大,水滴浸润其间隙的上方,这使该表面呈现中等黏附的超疏水特性.在μ-ICM过程中,涂覆在模板上的二氧化硅纳米粒子(SNPs)被转移到熔体中,并牢牢附着于微结构表层,赋予其表面亚微米或微米粗糙度,形成多层次微结构.在附着有亲水SNPs的微结构上,高表面自由能使水滴完全浸润微锥体之间的间隙,表面的水接触角为161.9°、滚动角大于90°,呈现极高黏附的超疏水特性(花瓣效应);在附着有疏水SNPs的微结构上,水滴受疏水SNPs的排斥而减弱与表面之间的黏附作用,表面的水接触角为163.5°、滚动角为3.5°,呈现极低黏附的超疏水特性(荷叶效应).     

Experimental study on viscosity properties of cyclic olefin copolymer (COC) flowing through micro capillary dies

As an emerging polymer, COC has been commonly used to make microfluidic chips by microinjection molding; and in this process, COC melt flows in a trans-scale cavity in which macro and micro scales coexist. Thus, in such a circumstance, understanding viscosity property of COC melt would be helpful to mold design, parameter determination of injection molding and prediction of molding quality. In this paper, viscosity properties of COC melt flowing in three dies with different diameters (500 μm, 200 μm, 100 μm) were investigated at three different temperatures (240 °C, 260 °C, 280 °C) by a capillary rheometer. The results showed that viscosity of COC melt flowing in different micro dies can be reduced significantly by increasing temperature, and visco-temperature property of COC melt could be described by Vogel equation in a considerable accuracy. It was found that temperature sensitivity of viscosity of COC melt varies with shear rate. Besides, as die diameter decreased, viscosity of COC melt was also reduced greatly. Moreover, in 500 μm die, viscosity of COC decreased constantly with shear rate; however, in 200 μm and 100 μm dies, viscosity witnessed an increase within a certain shear rate range. It implies that behavior of COC molecular chains might varies in different micro-scales.     

Self-organized ZnO nanorod with photooxidative cell membrane perforation enables large-scale cell manipulation

Various devices have been developed for verification and application of cellular functions in recent years. In our previous study, we found that local oxidation reactions in the cell membrane could produce submicron sizes of reversible membrane perforations in cells, while more than 80% of treated cells were viable even after perforations; therefore, to date, we have attempted some applications of this mechanism and analyzed their feasibility. In the present study, we developed a rod-shaped device in which the function of membrane perforation is added by utilizing a photosensitizer and, using the device, we have attempted to produce membrane perforations in a large number of cells. Zinc oxide nanorods were synthesized on the basis of the vapor–liquid–solid mechanism and α-terthienyl (photosensitizer) was adsorbed onto gold at the top of the rods to add a membrane perforation function. We studied the effect of the oxidation catalytic ability of the rods on rat PC12 cells after pressing and making the rods’ growth side come into contact with the base plate pressed onto the cells in a culture plate followed by photoexcitation of the photosensitizer for a certain period of time. It was revealed that water-soluble fluorescent marker molecules added extracellularly were taken up by the cells when the rods were applied at a pressure of 70 g/cm², with a light intensity of 0.82 W/cm², and with light irradiation for 30 s, as found in the case of the conventional photochemical cell membrane perforation method targeted at a single cell. These results suggest that cell membrane perforation can be successfully achieved in a large number of cells at a time. Figure Large-scale cell membrane perforation process using self-organized nanorods     

Screening and evaluation of antioxidants from lees by micro-injector systems combined with a fluorescent probe,N-borylbenzyloxycarbonyl-3,7-dihydroxyphenoxazine,in living Drosophila

A HPLC-UV-FLD system and a micro-injector imaging system were used in the study of antioxidants from natural products.     

Analysis of filling distance in cylindrical microfeatures for microinjection molding

In the injection molding of plastic components with cylindrical microfeatures, the ability for the polymer melt to flow into the microchannels is a crucial factor for successful molding. Penetration distance of the polymer melt into the microstructure depends on several factors as the melt flow rate and the cooling rate in the microfeatures, which depends on the materials and geometric dimensions. In this study, a simplified analytical model was constructed to estimate the filling distance into the cylindrical microchannels. The effects of the mold temperature, injection rate, heat transfer coefficient, and microchannel dimension on the filling distance were investigated. The filling distance decreases dramatically with respect to the decrease of the channel radius. In molding of plastic components with cylindrical microfeatures as those analyzed in this study, decrease of the part thickness could also increase the filling distance in the microfeatures.     

Crystallization Behavior and Mechanical Properties of Microinjection Molded High Density Polyethylene Parts

Ultra-thin high density polyethylene (HDPE) parts with two different molecular weights were prepared by microinjection molding (MIM). The dependence of crystalline morphology and orientation, as well as the resulting mechanical properties of the samples, on molecular weight is described. The toughness of the high-molecular-weight (HMW) sample was over 2 times that of the low-molecular-weight (LMW) one, in parallel with a significant increase of tensile strength. Microstructure characterizations, including differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS), were performed to investigate the variations of the microstructure. It is suggested that the increased crystallinity and higher degree of both molecular and lamellar orientation were beneficial to the enhancement of strength of the HMW sample. SAXS results showed that a highly oriented crystalline structure, i.e. shish-kebabs, were formed in parts of both of the two HDPE. Furthermore, a larger number of shish and kebab structure or lamellae was formed in the HMW sample due to the fact that the crystallinity was increased and the lamellar thickness and lateral crystallite size was reduced. Therefore, a stronger physical cross-linking network was formed in the HMW sample because of the increased connection points, which was in favor of the notable improvement of toughness. We suggest this issue is of great significance for achieving materials with high performance by tailoring the microstructure.     

聚乙烯醇/纳米羟基磷灰石复合材料微型注塑研究

结合固相剪切碾磨和分子复合技术制备了适合于微型注塑加工的聚乙烯醇/纳米羟基磷灰石(PVA/n-HA)复合材料,实现了n-HA含量达30%的PVA/n-HA复合材料的微型注塑加工。采用差示扫描量热法(DSC)、热重分析仪(TGA)和高压毛细管流变仪研究了PVA/n-HA复合材料的热性能和流变性能,结果表明:改性PVA/n-HA复合材料的熔点降低,热分解温度升高,获得120℃以上的热塑加工窗口;PVA/n-HA复合材料呈现剪切变稀特性,在高剪切速率下具有较低的熔体粘度,适合微型注塑加工,具有良好的充模性能。采用扫描电子显微镜(SEM)和X射线衍射(XRD)研究了PVA/n-HA微型注塑样品的结构与性能,结果表明n-HA均匀分散于PVA基体中,提高了复合材料的尺寸稳定性;受微型注塑过程中高剪切应力诱导结晶作用的影响,PVA/n-HA微型注塑样品的结晶度高于常规注塑样品的结晶度。     

Dispersive Liquid–Liquid Microextraction of Nickel Prior to Its Determination by Microsample Injection System-Flame Atomic Absorption Spectrometry

A sensitive and simple method for the determination of trace nickel was developed by the combination of dispersive liquid–liquid microextraction (DLLME) and microsample injection system–flame atomic absorption spectrometry (MIS–FAAS). Trace nickel was preconcentrated as the 8-hydroxyquinoline chelate by DLLME, and the conditions were optimized by a Plackett-Burman design. Quantitative recovery of nickel (98 ± 1%) was obtained by a sample volume of 7.5 mL at a pH of 6.0. The enrichment factor was 52.5, and the limits of detection and quantitation were 0.1 µ g L^?1 and 3.0 µ g L^?1, respectively. The method was validated by the analysis of a wastewater standard reference material, water samples, and a wire sample. The reported method has superior analytical figures of merit compared with similar methods reported in the literature.     

Filling and wear behaviors of micro-molded parts made with nanomaterials

Microinjection molding technology and its various modifications represent established processes for micro-molded parts with high accuracy under large scale production. Recently, the use of plastic material with added reinforced fillers has become a potential alternative approach due to its high strength and the ease of batch fabrication. This paper investigates the moldability and wear properties of a polymer with added nanoceramic materials during microinjection molding. In this study, parts with micro-features were successfully manufactured using a custom-made injection machine. The results show that the polymer with added nanomaterials effectively increased the hardness achieved. In addition, a nanoceramic material, such as ZnO, improved wear resistance by 70% when nanoparticles were uniformly dispersed in the polymer and a suitable surfactant solvent was chosen. However, wear resistance decreased significantly if the nanoparticles were not processed well and a proper surfactant solvent was not chosen. The results also show that high hardness did not result in reinforced parts with high wear resistance.