Magnetic nanoparticle decorated anodic alumina nanotubes for fluorescent detection of cathepsin B.

In this work, we present the process to provide anodic alumina nanotubes with magnetic responsivity based on magnetic nanoparticles. We demonstrate the possibility to cause the motion of these composite nanotubes under magnetic field, providing them with guided mobility. The obtained magnetic anodic alumina nanotubes are completely characterized and their potential to undergo selective and effective functionalization, and stimuli-responsive load release is demonstrated. For this purpose, protease-triggered release of fluorescent molecules loaded inside the magnetic anodic alumina nanotubes (MAANTs) by selective functionalization is performed. The inner walls of the MAANTs were selectively covered with protein padding of albumin-fluorescein isothiocyanate conjugate (FITC-BSA) through means of silanization. Protein functionalization was designed to undergo proteolytic hydrolysis in presence of cathepsin B- protease highly expressed during growth and initial stages of tumor metastasis - in order to cleave peptide bond of albumin and release fluorescent fragments of the protein. Proteolytic reaction with the enzyme is performed under acidic conditions. Presented arrangement is an exemplary combination of functionalities - which are vast - and of value for applications like drug delivery and biosensing applications.

Collagen and fibronectin surface modification of nanoporous anodic alumina and macroporous silicon for endothelial cell cultures.

BACKGROUND: The ability to direct the cellular response by means of biomaterial surface topography is important for biomedical applications. Substrate surface topography has been shown to be an effective cue for the regulation of cellular response. Here, the response of human aortic endothelial cells to nanoporous anodic alumina and macroporous silicon with collagen and fibronectin functionalization has been studied. METHODS: Confocal microscopy and scanning electron microscopy were employed to analyse the effects of the material and the porosity on the adhesion, morphology, and proliferation of the cells. Cell spreading and filopodia formation on macro- and nanoporous material was characterized by atomic force microscopy. We have also studied the influence of the protein on the adhesion. RESULTS: It was obtained the best results when the material is functionalized with fibronectin, regarding cells adhesion, morphology, and proliferation. CONCLUSION: These results permit to obtain chemical modified 3D structures for several biotechnology applications such as tissue engineering, organ-on-chip or regenerative medicine.

Low-cost fabrication technologies for nanostructures: state-of-the-art and potential.

In the last decade, some low-cost nanofabrication technologies used in several disciplines of nanotechnology have demonstrated promising results in terms of versatility and scalability for producing innovative nanostructures. While conventional nanofabrication technologies such as photolithography are and will be an important part of nanofabrication, some low-cost nanofabrication technologies have demonstrated outstanding capabilities for large-scale production, providing high throughputs with acceptable resolution and broad versatility. Some of these nanotechnological approaches are reviewed in this article, providing information about the fundamentals, limitations and potential future developments towards nanofabrication processes capable of producing a broad range of nanostructures. Furthermore, in many cases, these low-cost nanofabrication approaches can be combined with traditional nanofabrication technologies. This combination is considered a promising way of generating innovative nanostructures suitable for a broad range of applications such as in opto-electronics, nano-electronics, photonics, sensing, biotechnology or medicine.

Effect of pore diameter in nanoporous anodic alumina optical biosensors.

The influence of pore diameter over the optical response of nanoporous anodic alumina (NAA) films is analyzed by reflectance interference spectroscopy. NAA films manufactured by a two-step anodization procedure in oxalic acid exhibiting three well-defined pore diameter distributions with pores of 32 ± 4, 50 ± 3, and 73 ± 2 nm are studied. The optical detection of biomolecules is investigated by serially dosing protein A, human IgG and anti-human IgG into a nanoporous matrix using a custom-made flow cell. The results demonstrate that the transduction signal, the variation of effective optical thickness upon IgG binding to protein A (ΔEOT), depends on the nanopore diameter: for small pore diameter (32 nm) no significant differences in signals are observed for different protein concentrations whereas for larger pore diameters (50 nm and 73 nm) the signals increase for increasing concentrations from 10 to 100 µg mL(-1). Our experiments also show that this signal can be further enhanced by amplification with anti-human IgG due to the multiple binding events between the antigen and the antibody. These results will enable the development of more sensitive interferometric biosensors based on NAA.

All-silicon spherical-Mie-resonator photodiode with spectral response in the infrared region.

Silicon is the material of choice for visible light photodetection and solar cell fabrication. However, due to the intrinsic band gap properties of silicon, most infrared photons are energetically useless. Here, we show the first example of a photodiode developed on a micrometre scale sphere made of polycrystalline silicon whose photocurrent shows the Mie modes of a classical spherical resonator. The long dwell time of resonating photons enhances the photocurrent response, extending it into the infrared region well beyond the absorption edge of bulk silicon. It opens the door for developing solar cells and photodetectors that may harvest infrared light more efficiently than silicon photovoltaic devices that are so far developed.

ß-Phase Morphology in Ordered Poly(9,9-dioctylfluorene) Nanopillars by Template Wetting Method.

An efficient method based in template wetting is applied for fabrication of ordered Poly(9,9-dioctylfluorene) (PFO) nanopillars with ß-phase morphology. In this process, nanoporous alumina obtained by anodization process is used as template. PFO nanostructures are prepared under ambient conditions via infiltration of the polymeric solution into the pores of the alumina with an average pore diameter of 225 nm and a pore depth of 500 nm. The geometric features of the resulting structures are characterized with environmental scanning electron microscopy (ESEM), luminescence fluorimeter (PL) and micro µ-X-ray diffractometer (µ-XRD). The characterization demonstrates the ß-phase of the PFO in the nanopillars fabricated. Furthermore, the PFO nanopillars are characterized by Raman spectroscopy to study the polymer conformation. These ordered nanostructures can be used in optoelectronic applications such as polymer light-emitting diodes, sensors and organic solar cells.

Cobalt and Nickel Nanopillars on Aluminium Substrates by Direct Current Electrodeposition Process.

A fast and cost-effective technique is applied for fabricating cobalt and nickel nanopillars on aluminium substrates. By applying an electrochemical process, the aluminium oxide barrier layer is removed from the pore bottom tips of nanoporous anodic alumina templates. So, cobalt and nickel nanopillars are fabricated into these templates by DC electrodeposition. The resulting nanostructure remains on the aluminium substrate. In this way, this method could be used to fabricate a wide range of nanostructures which could be integrated in new nanodevices.