Authors: M.G. Bothara, R.K. Reddy, T. Barrett, J. Carruthers, S. Prasad
Affilation: Portland State University, United States
Pages: 344 - 347
Keywords: nanoporous, alumina, membrane, immunoassays, proteins
This research focuses on using the electrical and chemical properties of nanoporous alumina membranes to improve the sensitivity and performance of Si-based microdevices for protein sensing. The integration of nanoporous membranes with the microdevice results in nanoscale well-like structures, also known as nanowells which exhibit size matching with respect to proteins. The trapping of proteins within the nanowells is an experimental demonstration of “molecular crowding” phenomenon whereby the functionality of the proteins is retained due to confinement in small spaces i.e. nanowells. These alumina nanopores are electrically insulating and isolated resulting in grouping of nanowells for capacitance based detection of proteins. Conjugation of proteins into the nanowells results in a charge perturbation in the electrical double layer at the interface between the biomolecule and the gold electrode, thus causing a measurable change in the capacitance. The nanoporous alumina membrane is fabricated using electrochemical techniques – two step anodization. The dimensions of the pores can be tailored by varying the empirical parameters. The pores are cylindrical with typical dimensions of 200 nm in diameter and 250 nm in height. This porous membrane forms an overlayer on silicon/silicon dioxide surface with pre-fabricated gold electrodes. We have demonstrated the detection of two inflammatory proteins, C-reactive protein (CRP) and Myeloperoxidase (MPO), from purified samples as well as human serum. The device performance metrics - sensitivity, selectivity, dynamic range of detection for each protein and speed of detection - have been measured to quantify the efficacy of these nanomonitors and compared to standard immunoassays.