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Display Omitted Pit-patterned PDMS substrates were fabricated.Effect of bi-directional topographical cues on cellular behavior of HeLa cells was investigated.The pit-patterned substrates with rectangular pits could promote cell alignment.Cell elongation was reduced on the pit-patterned substrates.The HeLa cells responded to the patterns in a coordinated manner. The study of cell migration is valuable for the understanding of various physiological and pathological processes. Microgrooved/microridged substrates have been intensively studied to reveal the effect of single topographical cues on cellular behavior. However, cells in vivo are usually surrounded by multidirectional topography signals. This study investigated the effect of bi-directional topographical cues on cellular behavior of mammalian cells. In this study, bi-directional pit patterned poly(dimethylsiloxane) (PDMS) substrates were fabricated with different sizes but same depth (1µm). The fabricated patterns were then used to study cellular response to bi-directional cues of mammalian cell line, in this case HeLa cells. After seeding cells for 48h, the PDMS substrates were examined by SEM. Cell alignment angle and aspect ratio were measured from the SEM images. The results show that the cells on the patterned substrates with square pits did not align along either x- or y-axis. However the patterns with rectangular pits could promote cell alignment along the longer sides of pits. Moreover, comparing to the cell elongation on the control flat substrate, the elongation of cells was decreased on all the patterned substrates. These results are helpful for a deeper understanding of the mechanism of bi-directional topographical cues on cellular behavior of mammalian cell line.

Gold/iron oxide nanocomposites offer the promise of combining the unique traits of both gold and iron oxide nanomaterials to enable new applications. In this work, a simple and safe method has been established whereby the morphology of gold material in gold/iron oxide nanocomposites can be controlled to be nanowire or nanosphere by adjusting the initial molar ratio of citrate-coated iron oxide nanoparticles to auric acid. Gold/iron oxide nanowires and nanospheres were synthesized through this method. Their structural, optical, and magnetic properties were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), ultraviolet-visible spectroscopy (UV-Vis), and vibrating sample magnetometry (VSM). These materials substantially maintained the optical properties of gold nanomaterials and magnetic features of iron oxide magnetic nanoparticles.

Octahedron-like Au/Fe3O4 magnetic nanoparticles are synthesized using decomposition of FeO(OH) and HAuCl4 with the presence of oleic acid in 1-octadecene solvent. In the octahedron-like hybrid particles, Fe3O4 mainly displayed the octahedral morphology and spherical Au nanoparticles partially embedded into one side of Fe3O4 octahedron. The size of particle could be tuned from 25 to 240 nm for the whole particle (mainly for Fe3O4) and 10 to 40 nm for Au by changing the proportion of the starting materials. The hybrid particles showed the magnetic properties of Fe3O4 with dependence on the size of Fe3O4 octahedron composite and the proportion of Fe3O4 to Au. Coercivity is observed in the hybrid Au/Fe3O4 octahedron-like nanoparticles (55 Oe for 25 nm, 135 Oe for 100 nm, and 159 Oe for 240 nm) at room temperature. These size-controllable hybrid Au/Fe3O4 magnetic octahedron-like particles, inheriting the advantages of Au and Fe3O4 nanoparticles, may evolve as useful building blocks for nano- and micro-electronic applications.

Dextran-coated magnetic iron oxide nanoparticles (DMNPs) have attracted significant attention for their many applications in biomedical area such as diagnostic magnetic resonance imaging (MRI), and gene therapy. For biomedical applications, nanoparticles must be sterile, and several terminal sterilization methods can be used. However, very little is known regarding the effect of sterilization methods on the properties of DMNPs. It is crucial to find out whether the DMNPs are affected by the sterilization process. This paper reported the influences on the physicochemical properties of DMNPs from four different methods: autoclaving, sterile filtration, UV irradiation and chemical sterilization with ethanol. In addition, cell viability was also studied. Our results indicate that filter sterilization changes the iron oxide/dextran ratio in DMNPs sample significantly. Besides, the autoclaving and ethanol treatment affected the polydispersity index of DMNPs sample. Thus, caution must be taken when choosing an appropriate method to perform sterilization for DMNPs.

Material surface topography is an important factor for regulating cellular behaviour. Understanding the mechanism of how surface topography influences mammalian cells is critical for the development of medical implants and tissue engineering. In this study, we investigated the influences of nanoporous and microgrooved substrates on the morphology and migration of hepatic cell line, BEL-7402 cells. Cells were cultured on nanoporous (140nm in diameter) anodized alumina membrane (AAM), nanoporous (140nm in diameter) polydimethylsiloxane (PDMS), and microgrooves (10@mm, 30@mm, and 50@mm in width, and 2@mm in depth) patterned PDMS, then imaged by fluorescent microscopy, time-lapse microscopy, and scanning electron microscopy (SEM). Cell morphology and migration were investigated through image analysis. The results suggest that the nanoporous and microgrooved surface structure induced totally different changes on BEL-7402 cells. Compared to the well-spread cells on the flat surface plate, the cells formed spheroids on the nanoporous AAM surface and nanoporous PDMS surface with no elongation and alignment, while the cells grew with elongated and aligned morphology along the microgrooves on the PDMS substrates. The BEL-7402 cell migration speed was significantly higher on the nanoporous substrates than on the flat surfaces. On the microgrooved PDMS substrates, the cells migrated along the groove direction and showed relatively small difference of the overall velocity compared to the cells on the flat PDMS surface. Our findings provide insights into the control of cell morphological features and migratory behaviour by using artificial nanoporous or microgrooved substrates, which can benefit the research on hepatocellular carcinoma metastasis, tissue engineering, and medical implant design.

Citric acid is a widely accepted coating material in nanoparticle fabrication for biomedical applications while iron oxide is one popular magnetic material with excellent properties for use in nanoparticle form. However, the effect of synthesis conditions on the properties of iron oxide nanoparticles is not sufficiently understood. Here, citric-acid coated iron oxide nanoparticles were synthesized based on the co-precipitation method through both one-step and two-step process, respectively. The citric acid was added at different stages, and various coating temperatures were used in the two-step process. The nanoparticles were characterized by multiple techniques including Fourier transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, and vibrating sample magnetometry. It was found that the addition of citric acid at different stages can alter the nanoparticle core size, while the coating temperature affects citric acid adsorption around nanoparticles surface and alters the nanoparticle hydrodynamic size. The effect of citric-acid coating on the magnetic behavior was also investigated on 9nm and 25nm iron oxide nanoparticles.

We demonstrated the use of exchange-biased giant magnetoresistance (GMR) sensors in Wheatstone bridge for the detection of 10-nm superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs were synthesized via coprecipitation method, exhibiting a superparamagnetic behavior with saturation magnetization of 57 emu/g. The output voltage signal of the Wheatstone bridge exhibits log-linear function of the concentration of SPIONs (from 10 ng/ml to 0.1 mg/ml), making the sensors suitable for use as a SPION concentration detector. Thus the combination of 10 nm SPIONs and the exchange-biased GMR sensors has potential to be used in the bio-detection applications where ultra-small bio-labels are needed.

Magnetic nanoparticles functionalized with carboxyl-group have considerable potential to be used as bio-labels due to their conjugation abilities with proteins. Here, we synthesized the iron oxide nanoparticles functionalized with carboxyl groups through self-assembled monolayer coating using citric acid and self-assembled bilayer coating using fatty acids. Their dimension, hydrodynamic size, surface property, and magnetic behavior were characterized through transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and vibrating sample magnetometry. We also confirmed the binding ability of these nanoparticles with bovine serum albumin on thin gold film.