Comparative cell behavior on carbon-coated TiO2 nanotube surfaces for osteoblasts vs. osteo-progenitor cells

Surface engineering approaches that alter the topological chemistry of a substrate could be used as an effective tool for directing cell interactions and their subsequent function. It is well known that the physical environment of nanotopography has positive effects on cell behavior, yet direct comparisons of nanotopographic surface chemistry have not been fully explored. Here we compare TiO(2) nanotubes with carbon-coated TiO(2) nanotubes, probing osteogenic cell behavior, including osteoblast (bone cells) and mesenchymal stem cell (MSC) (osteo-progenitor cells) interactions with the different surface chemistries (TiO(2) vs. carbon). The roles played by the material surface chemistry of the nanotubes did not have an effect on the adhesion, growth or morphology, but had a major influence on the alkaline phosphatase (ALP) activity of osteoblast cells, with the original TiO(2) chemistry having higher ALP levels. In addition, the different chemistries caused different levels of osteogenic differentiation in MSCs; however, it was the carbon-coated TiO(2) nanotubes that had the greater advantage, with higher levels of osteo-differentiation. It was observed in this study that: (a) chemistry plays a role in cell functionality, such as ALP activity and osteogenic protein gene expression (PCR); (b) different cell types may have different chemical preferences for optimal function. The ability to optimize cell behavior using surface chemistry factors has a profound effect on both orthopedic and tissue engineering in general. This study aims to highlight the importance of the chemistry of the carrier material in osteogenic tissue engineering schemes.     

Critical areas of cell adhesion on micropatterned surfaces

The adhesive area is important to modulate cell behaviors on a substrate. This paper aims to semi-quantitatively examine the existence of the characteristic areas of cell adhesion on the level of individual cells. We prepared a series of micropatterned surfaces with adhesive microislands of various sizes on an adhesion-resistant background, and cultured cells of MC3T3-E1 (osteoblast), BMSC (bone mesenchymal stem cell) or NIH3T3 (fibroblast) on those modeled surfaces. We have defined seven characteristic areas of an adhesive microisland and confirmed that they are meaningful to describe cell adhesion behaviors. Those parameters are (1) the critical adhesion area from apoptosis to survival denoted as A? or A(c?), (2) the critical area from adhesion of a single cell to adhesion of multiple cells (A(c?)), (3) the basic area for one more cell to adhere (A(Δ)), (4) and (5) the characteristic areas of a microisland most probably occupied by one cell (A(peak?) and two cells (A(peak?)), (6) and (7) the characteristic areas of a microisland occupied by one cell (A(N?)) or two cells (A(N?)) on average. Besides the introduction of those basic parameters, the present paper demonstrates how to determine them experimentally. We further discussed the relationship between those characteristic areas and the spreading area on a non-patterned adhesive surface.     

Improved bone-forming functionality on diameter-controlled TiO2 nanotube surface

The titanium dioxide (TiO₂) nanotube surface enables significantly accelerated osteoblast adhesion and exhibits strong bonding with bone. We prepared various sizes (30–100 nm diameter) of titanium dioxide (TiO₂) nanotubes on titanium substrates by anodization and investigated the osteoblast cellular behavior in response to these different nanotube sizes. The unique and striking result of this study is that a change in osteoblast behavior is obtained in a relatively narrow range of nanotube dimensions, with small diameter (～30 nm) nanotubes promoting the highest degree of osteoblast adhesion, while larger diameter (70–100 nm) nanotubes elicit a lower population of cells with extremely elongated cellular morphology and much higher alkaline phosphatase levels. Increased elongation of nuclei was also observed with larger diameter nanotubes. By controlling the nanotopography, large diameter nanotubes, in the ～100 nm regime, induced extremely elongated cellular shapes, with an aspect ratio of 11:1, which resulted in substantially enhanced up-regulation of alkaline phosphatase activity, suggesting greater bone-forming ability than nanotubes with smaller diameters. Such nanotube structures, already being a strongly osseointegrating implant material, offer encouraging implications for the development and optimization of novel orthopedics-related treatments with precise control toward desired cell and bone growth behavior.     

Adhesion of biocompatible and biodegradable micropatterned surfaces

We studied the effects of pillar dimensions and stiffness of biocompatible and biodegradable micropatterned surfaces on adhesion on different compliant substrates. The micropatterned adhesives were based on biocompatible polydimethylsiloxane (PDMS) and biodegradable poly(lactic-co-glycolic) acid (PLGA) polymer systems. Micropatterned and non-patterned compliant PDMS did not show significant differences in adhesion on compliant mice ear skin or on gelatin-glycerin model substrates. However, adhesion measurements for micropatterned stiff PLGA on compliant gelatin-glycerin model substrates showed significant enhancement in pull-off strengths compared to non-patterned controls.     

Schwann cell response to micropatterned laminin surfaces.

In the peripheral nervous system, Schwann cells are closely associated with, and play key roles in, the development, maintenance, and regeneration of peripheral neurons. Following injury, Schwann cell orientation may also play a role in guiding regenerating axons. To aid in the investigation of these interactions between Schwann cells and growing neurites, we have developed a method of controlling Schwann cell placement and orientation in vitro by using microlithographically patterned laminin substrates, alternating 20-microm regions of laminin with bovine serum albumin (BSA) stripes. The Schwann cells predominantly attached and elongated on the laminin stripes and organized into multicellular aggregates that were oriented with the micropattern. A detailed analysis of Schwann cell aggregate orientation and shape demonstrated a strong dependence on time. At 1 h after seeding the cells, 70% of the aggregates were oriented with respect to the micropattern; 94% were oriented at 24 h. Variations in laminin concentration and seeding density were also investigated. The only significant differences in Schwann cell response occurred 1 h after seeding (the earliest time point the cultures were observed), and the main factor controlling the cellular orientation appeared to be the presence of the laminin-BSA interface. This ability to control cell orientation and placement provides a tool for future investigations of Schwann cell-neuronal interactions in vitro.     

Effect of nano- and micro-roughness on adhesion of bioinspired micropatterned surfaces

In this work, the adhesion of biomimetic polydimethylsiloxane (PDMS) pillar arrays with mushroom-shaped tips was studied on nano- and micro-rough surfaces and compared to unpatterned controls. The adhesion strength on nano-rough surfaces invariably decreased with increasing roughness, but pillar arrays retained higher adhesion strengths than unpatterned controls in all cases. The results were analyzed with a model that focuses on the effect on adhesion of depressions in a rough surface. The model fits the data very well, suggesting that the pull-off strength for patterned PDMS is controlled by the deepest dimple-like feature on the rough surface. The lower pull-off strength for unpatterned PDMS may be explained by the initiation of the pull-off process at the edge of the probe, where significant stress concentrates. With micro-rough surfaces, pillar arrays showed maximum adhesion with a certain intermediate roughness, while unpatterned controls did not show any measurable adhesion. This effect can be explained by the inability of micropatterned surfaces to conform to very fine and very large surface asperities.     

Retinal pigment epithelial cell function on substrates with chemically micropatterned surfaces

Model substrates with desired chemical micropatterns were fabricated using a microcontact printing technique. The substrate surfaces contained organized arrays of circular glass domains with a diameter of either 10 or 50 microm surrounded and separated by regions modified with octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs). The effects of surface patterning on in vitro cell attachment, proliferation, morphology, and cytoskeletal organization were evaluated using a human retinal pigment epithelium (RPE) cell line. Both micropatterns affected initial RPE cell attachment, limited cell spreading, and promoted the characteristic cuboidal cell morphology throughout the culture period. In contrast, RPE cells on plain glass control were elongated and appeared fibroblast-like prior to confluence. In addition, cells seeded at 30,000 cell/cm2 on the patterned surfaces maintained a normal pattern of actin and cytokeratin expression, and formed confluent monolayers within 4 days of culture. The cell density increased about 30-fold on both micropatterns by day 7. These results show that it is feasible to control RPE cell shape and expression of differentiated phenotype using micropatterned surfaces.     

Repositioning of cells by mechanotaxis on surfaces with micropatterned Young's modulus

Adherent cells are strongly influenced by the mechanical aspects of biomaterials, but little is known about the cellular effects of spatial variations in these properties. This work describes a novel method to produce polymeric cell culture surfaces containing micrometer-scale regions of variable stiffness. Substrates made of acrylamide or poly(dimethylsiloxane) were patterned with 100- or 10-microm resolution, respectively. Cells were cultured on fibronectin-coated acrylamide having Young's moduli of 34 kPa and 1.8 kPa, or fibronectin-coated PDMS having moduli of 2.5 MPa and 12 kPa. Over several days, NIH/3T3 cells and bovine pulmonary arterial endothelial cells accumulated preferentially on stiffer regions of substrates. The migration, not proliferation, of cells in response to mechanical patterning (mechanotaxis) was responsible for the accumulation of cells on stiffer regions. Differential remodeling of extracellular matrix protein on stiff versus compliant regions was observed by immunofluorescence staining, and may have been responsible for the observed mechanotaxis. These results suggest that mechanically patterned substrates might provide a general means to study mechanotaxis, and a new approach to patterning cells.     

In vitro generation of differentiated cardiac myofibers on micropatterned laminin surfaces

Cardiac muscle fibers consist of highly aligned cardiomyocytes containing myofibrils oriented parallel to the fiber axis, and successive cardiomyocytes are interconnected at their ends through specialized junctional complexes (intercalated disks). Cell culture studies of cardiac myofibrils and intercalated disks are complicated by the fact that cardiomyocytes become extremely flattened and exhibit disorganized myofibrils and diffuse intercellular junctions with neighboring cells. In this study we sought to direct the organization of cultured cardiomyocytes to more closely resemble that found in vivo. Lanes of laminin 5-50 microm wide were microcontact-printed onto nonadhesive (BSA-coated) surfaces. Adherent cardiomyocytes responded to the spatial constraints by forming elongated, rod-shaped cells whose myofibrils aligned parallel to the laminin lanes. Patterned cardiomyocytes displayed a striking, bipolar localization of the junction molecules N-cadherin and connexin43 that ultrastructurally resembled intercalated disks. When laminin lanes were widely spaced, each lane of cardiomyocytes beat independently, but with narrow-spacing cells bridged between lanes, yielding aligned fields of synchronously beating cardiomyocytes. Similar cardiomyocyte patterns were achieved on the biodegradable polymer PLGA, suggesting that patterned cardiomyocytes could be used in myocardial tissue engineering. Such highly patterned cultures could be used in cell biology and physiology studies, which require accurate reproduction of native myocardial architecture.     

Hepatocyte and kupffer cells co-cultured on micropatterned surfaces to optimize hepatocyte function

One strategy for temporarily extending the lives of patients with liver failure is the use of bioartificial liver (BAL) support devices. The functional components of BALs are the parenchymal liver cells known as hepatocytes. One design option for further improving current BAL performance levels is to include the non-parenchymal cells of the liver (e.g., Kupffer cells) in the design. In the current study, the effect of Kupffer cells on hepatocyte function was investigated using micropatterned co-cultures of these two liver cell populations. With traditional co-culture methods, the user is unable to control the relative proximity of one cell type to another. In this study, two different micropatterning techniques were used to engineer macro and fine micropatterned configurations for evaluating hepatocyte-Kupffer cell co-cultures. The ratio of one cell population to the other was also adjusted to evaluate the effects on hepatocyte function. The micropatterned co-cultures were maintained for ten days to evaluate for morphological and functional (e.g., albumin, urea) changes. The results illustrate that micropatterning hepatocytes, in the arrangements of this study, significantly improved hepatocyte function.     

Engineering micropatterned surfaces for the coculture of hepatocytes and Kupffer cells

Bioartificial liver (BAL) devices are used for applications ranging from pharmaceutical testing to temporary liver replacement. The capabilities of these devices can be improved by optimizing the range of hepatocyte functions that the BAL is able to perform. One means of achieving this is to design the BAL such that it establishes communication between hepatocytes and nonparenchymal cells. To understand how these heterotypic interactions can be favorably utilized in BAL design, it is first necessary to establish a culture environment that permits the controlled interactions of multiple cell types. This is the goal of the current study, which focuses on micropatterned cocultures of hepatocytes with Kupffer cells. The micropatterning technique relies on a polydimethylsiloxane (PDMS) membrane to achieve various two-dimensional configurations of the ECM prior to seeding the cell populations. The easy and inexpensive method of making the PDMS membranes differs from that reported in the literature and is detailed in the current study. To demonstrate the success of the method, surface characterization of the resultant micropatterns, as well as morphological and functional results are also presented.     

Human erythrocyte adhesion and spreading on protein-coated polymer surfaces

Protein adsorption is the first event which occurs when polymer surfaces are exposed to blood. The adsorption of proteins modifies the surface properties of the substrates and therefore influences subsequent cell-surface interactions. In an attempt to elucidate the fundamental mechanisms governing cell-proteinated-surface interactions, the extent of fresh human erythrocyte adhesion and spreading on protein-coated surfaces was examined. Five human serum proteins (albumin, fibrinogen, immunoglobulin G, fibronectin, and transferrin) were used at bulk concentrations ranging from 0.01 mg/mL to 50 mg/mL. Polymer substrates covering a wide range of wettability were employed. Protein adsorption significantly reduces erythrocyte adhesion and spreading on all test surfaces with minimum adhesion observed on fibrinogen: IgG greater than albumin greater than fibronectin greater than transferrin greater than fibrinogen. The extent of these effects is dependent on the nature of the adsorbed protein, the protein bulk concentration, and the surface properties of the underlying polymer substrates.     

Retinal pigment epithelial cell adhesion on novel micropatterned surfaces fabricated from synthetic biodegradable polymers

Novel synthetic biodegradable polymer substrates with specific chemical micropatterns were fabricated from poly(DL-lactic-coglycolic acid) (PLGA) and diblock copolymers of poly(ethylene glycol) and poly(DL-lactic acid) (PEG/PLA). Thin films of PLGA and PEG/PLA supported and inhibited, respectively, retinal pigment epithelial (RPE) cell proliferation, with a corresponding cell density of 352,900 and 850 cells/cm2 after 7 days (from an initial seeding density of 15,000 cells/cm2). A microcontact printing technique was used to define arrays of circular (diameter of 50 microm) PLGA domains surrounded and separated by regions (width of 50 microm) of PEG/PLA. Reversed patterns composed of PEG/PLA circular domains surrounded by PLGA regions were also fabricated. Both micropatterned surfaces were shown to affect initial RPE cell attachment, limit cell spreading, and promote the characteristic cuboidal cell morphology during the 8-h period of the experiments. In contrast, RPE cells on plain PLGA (control films) were elongated and appeared fibroblast-like. The reversed patterns had continuous PLGA regions that allowed cell-cell interactions and thus higher cell adhesion. These results demonstrate the feasibility of fabricating micropatterned synthetic biodegradable polymer surfaces to control RPE cell morphology.     

A fluorophore-tagged RGD peptide to control endothelial cell adhesion to micropatterned surfaces

The long-term patency rates of vascular grafts and stents are limited by the lack of surface endothelialisation of the implanted materials. We have previously reported that GRGDS and WQPPRARI peptide micropatterns increase the endothelialisation of prosthetic materials in vitro. To investigate the mechanisms by which the peptide micropatterns affect endothelial cell adhesion and proliferation, a TAMRA fluorophore-tagged RGD peptide was designed. Live cell imaging revealed that the micropatterned surfaces led to directional cell spreading dependent on the location of the RGD-TAMRA spots. Focal adhesions formed within 3 h on the micropatterned surfaces near RGD-TAMRA spot edges, as expected for cell regions experiencing high tension. Similar levels of focal adhesion kinase phosphorylation were observed after 3 h on the micropatterned surfaces and on surfaces treated with RGD-TAMRA alone, suggesting that partial RGD surface coverage is sufficient to elicit integrin signaling. Lastly, endothelial cell expansion was achieved in serum-free conditions on gelatin-coated, RGD-TAMRA treated or micropatterned surfaces. These results show that these peptide micropatterns mainly impacted cell adhesion kinetics rather than cell proliferation. This insight will be useful for the optimization of micropatterning strategies to improve vascular biomaterials.     

骨科钛板表面TiO2纳米管阵列的制备和结构表征

目的 在骨科钛板表面制备TiO2纳米管阵列,并对其表征,为骨科内植物表面修饰或涂层提供载体,也为防治骨科内植物感染寻求一新途径.方法 利用阳极氧化法,以甘油体系为电解液,骨科临床钛板为阳极,铂电极为阴极,通过调整一定的参数,在骨科钛板表面制备TiO2纳米管阵列,并对其表征.利用X射线光电子能谱仪(XPS)分析纳米管元素组成,并通过X射线衍射仪(XRD)观察其在300 ℃高温下形态是否变化.结果 以甘油体系为电解液,使用阳极氧化法24 h可在骨科临床钛板表面制备出管径为100～200 nm、管长在3μm以内的TiO2纳米管阵列.宏观直视下可见骨科钛板表面由银白色变为深蓝色.XPS分析骨科钛板表面的TiO2纳米管阵列主要由Ti元素(75.88％)、O元素(20.16％)和F元素(3.96％)组成.此外,经马弗炉加温至300℃的TiO2纳米管阵列形态稳定.结论 利用阳极氧化法可制备出表面均匀的TiO2纳米管阵列.该阵列形态稳定,内部中空状,底部封闭,具有较大的比表面积,且可耐受高温,可为骨科内植物表面修饰或涂层提供载体.     

Supercritical CO2-assisted embossing for studying cell behaviour on microtextured surfaces

Recently, cell responses to micro- and nanoscale structures have attracted much attention. Although interesting phenomena have been observed, we have encountered some difficulties in elucidating purely topographical effects on cell behaviour. These problems are partially attributable to the introduction of functional groups and the persistence of chemicals during surface processing. In this study, we introduced supercritical CO(2)-assisted embossing, which plasticizes a polycarbonate plate by dissolving supercritical CO(2) and thus can emboss wide-scale patterns onto the plate at a lower temperature than the polycarbonate glass transition temperature. Uniform micro- and nanopatterned surfaces were observed across the whole area of the polycarbonate plate surfaces. Nickel, fluorine, and nitrogen were not detected on the fabricated surfaces, and the surface carbon-to-oxygen ratios were equivalent to the theoretical ratio (C:O=84.2:15.8) calculated from the polycarbonate molecular structure. Human mesenchymal stem cells were cultured on the fabricated microlens and nanogroove substrata. Cell-adhered areas became smaller on the microlens than on non-treated polycarbonate. Meanwhile, cells aligned along the ridges of nanogrooves with valleys deeper than 90 nm. This supercritical CO(2)-assisted embossing can produce fine substrates for studying the effects of surface topography of synthetic materials on cell behaviours.     

Morphological alterations of T24 cells on flat and nanotubular TiO2 surfaces

Aim

To investigate morphological alterations of malignant cancer cells (T24) of urothelial origin seeded on flat titanium (Ti) and nanotubular titanium dioxide (TiO₂) nanostructures.

Methods

Using anodization method, TiO₂ surfaces composed of vertically aligned nanotubes of 50-100 nm diameters were produced. The flat Ti surface was used as a reference. The alteration in the morphology of cancer cells was evaluated using scanning electron microscopy (SEM). A computational model, based on the theory of membrane elasticity, was constructed to shed light on the biophysical mechanisms responsible for the observed changes in the contact area of adhesion.

Results

Large diameter TiO₂ nanotubes exhibited a significantly smaller contact area of adhesion (P < 0.0001) and had more membrane protrusions (eg, microvilli and intercellular membrane nanotubes) than on flat Ti surface. Numerical membrane dynamics simulations revealed that the low adhesion energy per unit area would hinder the cell spreading on the large diameter TiO₂ nanotubular surface, thus explaining the small contact area.

Conclusion

The reduction in the cell contact area in the case of large diameter TiO₂ nanotube surface, which does not enable formation of the large enough number of the focal adhesion points, prevents spreading of urothelial cells.The material and topographical characteristics of the contact surface affect the functional activity of cells (1-7). Titanium is the most widely used material in numerous medical applications, because it is non-toxic. The titanium surface has recently been modified by a self-assembled layer of vertically oriented titanium oxide (TiO₂) nanotubes with diameters between 15 nm and 100 nm (8-10). It was revealed that cell adhesion, spreading, growth, and differentiation was maximally induced on 15 nm nanotubes, but hindered on 100 nm nanotubes, which facilitated cell death (8,9). These results suggest that magnitude of TiO₂ nanotube diameter has an important role in cell adhesion and cell growth, and that the mechanics of the formation of focal adhesions is similar between different types of cells. The aim of the present study is to analyze effects of flat titanium and nanotubular TiO₂ surfaces on the morphology of malignant cancer cells (T24) of urothelial origin.Using anodization method, vertically aligned TiO₂ nanotubular surfaces were produced (Figure 1). The produced nanotubes had a large diameter (50-100 nm). The T24 cells grown on the nanotubular surface had a smaller top view diameter and more membrane protrusions than the counterpart on the flat titanium surface. A computational model was constructed to shed light on the biophysical mechanism underlying the observed morphologic changes. The underlying hypothesis is that the low density of TiO₂ nanotube edges could not facilitate the cell adhesion, ie, the formation of large enough number of focal adhesion points. Mathematically, the density of negative charges is predicted to be greatest at sharp edges (7), which would then facilitate the mediated electrostatic interactions between the TiO₂ nanotube surface and membrane proteins at the focal contact. Using numerical simulations of membrane dynamics, it is revealed that low adhesion of the membrane to the large diameter nanotubular surface is not sufficient to counterbalance the loss of entropic energy during the clustering of proteins at a focal contact, and consequently, the increased membrane bending energy does not favor intensive spread of cancer cells on the large diameter TiO₂ nanotube surface underneath.Open in a separate windowFigure 1Scanning electron microscopy images of surface layers of self-assembled vertically aligned TiO₂ nanotubes synthesized by anodization method. Ethylene glycol solution with 0.3 wt % NH₄F and 1% volume water was used in preparation. High-resolution scanning electron microscopy FEG-SEM 7600F from JEOL was used. Images were taken at 100000× magnitude using low accelerating voltage of 2kV. The internal TiO₂ tube diameter was around 50-60 nm (A-D) and 100 nm (E-F) while the length could be up to 10 micrometers (B).     

制备TiO2-xNx薄膜陶瓷托槽的抗菌性能

BACKGROUND: Enamel demineralization has been plaguing doctors and patients in the fixed orthodontic treatment, so we attempt to seek an effective method of reducing its incidence. OBJECTIVE: To prepare TiO₂-xNx thin films at different thicknesses on the ceramic bracket surface by sol-gel method followed by detection of antibiotic performance. METHODS: TiO₂-xNx thin films at different thicknesses were prepared on the ceramic bracket surface by sol-gel method. The crystal structure, surface morphology and attachment force of these thin films were analyzed by X-ray diffraction, scanning electron microscope and multi-function material surface tester, respectively. The color changes of ceramic brackets before and after coating were evaluated through German VITA Easyshade Advance 4.0 photoelectric color comparator. Antibiotic performance of the ceramic bracket coated with TiO₂-xNx thin film for Candida albicans and Streptococcus mutans was evaluated by the flat colony counting method. RESULTS AND CONCLUSION:The prepared TiO₂-xNx thin film was anatase type, which had uniform and compact structure, and its X-ray diffraction peaks were elevated with the increase of film thickness. The attachment force of the thickest film was 18.37 N, indicating the thin film has a good adhesion to the ceramic bracket and can withstand the friction in the oral cavity. The antibiotic performance of TiO₂-xNx thin film for Candida albicans and Streptococcus mutans was also enhanced as the thickness of the thin film tended to increase, while the color changes of the ceramic brackets coated with different thickness of TiO₂-xNx thin films were not significant. To conclude, the ceramic bracket coated with TiO₂-xNx film that does not affect the appearance has high antibacterial activity to common oral cariogenic bacteria and opportunistic pathogens, and the film can adhere well to the bracket.     

Preparation and analysis of macroporous TiO2 films on Ti surfaces for bone-tissue implants

This article describes the preparation and analysis of macroporous TiO2 films on Ti surfaces, for application in bone tissue-Ti implant interfaces. These TiO2 bioceramic films have a macroporous structure consisting of monodisperse, three-dimensional, spherical, interconnected pores adjustable in the micron size range. Micron-sized polystyrene (PS) bead templates are used to precisely define the pore size, creating macroporous TiO2 films with 0.50, 16, and 50 microm diameter pores, as shown by scanning electron microscopy. X-ray photoelectron spectroscopy shows the films to be predominantly composed of TiO2, with approximately 10% carbon. X-ray diffraction reveal rutile as the main phase when fired to the optimal temperature of 950 degrees C. Preliminary experiments find that the in vitro proliferation of human bone-derived cells (HBDC) is similar on all three pore sizes. However, higher [3H]thymidine incorporation by the HBDC is observed when they are grown on 0.50- and 16-microm pores compared to the 50-microm pores, suggesting an enhanced cell proliferation for the smaller pores.     

纳米氧化铁、纳米TiO2、碳纳米管的毒理学研究进展

纳米材料的广泛应用使研究者、生产者和消费者将有更多的机会接触纳米材料。纳米粒子可经多种途径进入人体,其是否会影响人类健康引起了广泛关注。纳米TiO2和碳纳米管在工业及商业有着广泛的应用前景,纳米氧化铁是磁共振成像诊断、磁性药物载体及肿瘤靶向定位治疗的热门生物材料。分析综述了纳米氧化铁、纳米TiO2和碳纳米管三种材料的毒理学研究结果,并提出了在纳米毒理学研究目前亟待解决的重要问题。