Surface Modification of Nanoporous Alumina Surfaces with Poly(ethylene glycol)

Abstract

Nanoporous alumina surfaces have a variety of applications in biosensors, biofiltration, and targeted drug delivery. However, the fabrication route to create these nanopores in alumina results in surface defects in the crystal lattice. This results in inherent charge on the porous surface causing biofouling, that is, nonspecific adsorption of biomolecules. Poly(ethylene glycol) (PEG) is known to form biocompatible nonfouling films on silicon surfaces. However, its application to alumina surfaces is very limited and has not been well investigated. In this study, we have covalently attached PEG to nanoporous alumina surfaces to improve their nonfouling properties. A PEG-silane coupling technique was used to modify the surface. Different concentrations of PEG for different immobilization times were used to form PEG films of various grafting densities. X-ray photoelectron spectroscopy (XPS) was used to verify the presence of PEG moieties on the alumina surface. High-resolution C1s spectra show that with an increase in concentration and immobilization time, the grafting density of PEG also increases. Further, a standard overlayer model was used to calculate the thickness of PEG films formed using the XPS intensities of the Al2p peaks. The films formed by this technique are less than 2.5 nm thick, suggesting that such films will not clog the pores which are in the range of 70-80 nm.

Rapid and Sensitive Detection of Lung Cancer Biomarker Using Nanoporous Biosensor Based on Localized Surface Plasmon Resonance Coupled with Interferometry

“…The AAO chips can be synthesized via anodization of metal aluminum. Using this procedure, precise control of the pore diameter and length can be achieved [20]. Owing to these fairly welldefined nanopores, AAO chips have been used in popular applications in many areas, such as nanostructured-material preparation and biological and chemical separations [21,22].…”

Biocompatibility of nanoporous alumina membranes for immunoisolation

“…Poly (ethylene glycol) (PEG) immobilization on the alumina surface was achieved using a covalent coupling technique described by Popat et al [18,19]. This technique forms more stable films compared to physical adsorption on the surface.…”

“…Inorganic membranes are much more chemically and mechanically stable, and important features such as the pore size and pore size distribution can be easily controlled by varying the fabrication parameters [5,[8][9][10][14][15][16][17]. Further, the surface of inorganic membranes can be chemically tailored to resist the adhesion of blood proteins and immune cells that may block the pores and reduce the diffusion of therapeutic agents [18,19].…”

Surface Modification of Alumina Nanoparticles: A Dispersion Study in Organic Media

“…Popat and co-workers have covalently attached PEG to nano-porous alumina surfaces to improve their non-fouling properties. 21 A PEG-silane coupling technique was used to modify the surface.…”