Bio-Hybrid Materials for Immunoassay-Based Sensing
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0915-R01-01
Bio-Hybrid Materials for Immunoassay-Based Sensing Jonathan Fang1, Esther H. Lan2, Jing C. Zhou1, and Bruce Dunn2 1 Department of Biomedical Engineering IDP, University of California, Los Angeles, Los Angeles, CA, 90095 2 Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, 90095 ABSTRACT The process of encapsulating antibodies in sol-gel was used for sensing various hormones, specifically cortisol, insulin, and C-peptide. A sol-gel optical biosensor for cortisol has been developed for monitoring of crew health on-orbit during space missions. Our studies involving silica sol-gel materials with competitive immunoassays demonstrated linear calibration for cortisol in the range of 2-60 µg/dL, which covers the physiological range of cortisol blood concentration for an adult (2-28 µg/dL). The method of standard additions was used to analyze human serum samples sent to us from a NASA laboratory. Our sol-gel immunosensor values were typically within 20% of the values obtained using traditional immuno-binding techniques, with some values having less than a 5% error. Initial results are presented for sensing the hormones insulin and C-peptide.
INTRODUCTION Sol-gel encapsulation of biomolecules for immunoassays has become of increasing interest over the last decade [1-4]. Optimal analyte detection by immunoassays requires combining maximum retention of the structure and activity of the biomolecule with effective signal transduction. Traditional methods for detection of biomolecules involve radioimmunoassays (RIA) [5-7] and enzyme-linked immunosorbent assays (ELISA) [8-9]. A problematic issue for traditional immunoassays is that certain biomolecules, such as proteins, lose their stability or functionality upon immobilization [1]. Some common immobilization techniques are physical adsorption and covalent bonding [1]. Physical adsorption of the biomolecule to the surface utilizes weak bonding. Covalent bonding provides a strong attachment of the biomolecule to the surface but there are difficulties in isolating the biomolecule for analysis and detection. To resolve these issues, we employed an alternative method, the encapsulation of biomolecules in sol-gel matrices. The sol-gel process is a low-temperature method for making ceramics, gels, and glass materials. It is based on the hydrolysis and condensation of a metal alkoxide precursor [1012]. The sol, which is a stable suspension of colloidal solid particles in a liquid, will solidify and form a gel, or a porous 3-dimensional interconnected matrix [1]. There are several advantages to using the process of biomolecular encapsulation in sol-gel as an immobilization technique. They include the preservation of the structure and activity of the biomolecule, prevention of self-aggregation, protection from outside environmental conditions, improved thermal resistance and storage capability, good mechanical durability, and good optical properties [1]. The sol-gel process can be utilized for synthesis of
transparent sil
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