Optical Properties of Bound Antigen Monolayers for Biomolecular Microsensors

Abstract

REPORT DOCUMENTATION PAGEForm Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. REPORT TYPE AND DATES COVEREDFinal Aug 01 -Sep 03 TITLE AND SUBTITLE OPTICAL PROPERTIES OF BOUND ANTIGEN MONOLAYERS FOR BIOMOLECULAR MICROSENSORS AUTHOR(S)Daniel A. Cohen FUNDING NUMBERSC -F30602-01-2-0538 PE -61101E PR -E117 TA -00 WU -67 PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)University 12b. DISTRIBUTION CODE ABSTRACT (Maximum 200 Words)The formalism of molar refraction was extended to cover the wavelength range of 200 nm -2500 nm, in order to predict the index of refraction and index increment of a wide range of molecules of biochemical interest. Data for the model was obtained using a unique interferometer cell within a standard laboratory spectrophotometer. The resulting models for protein index increment suggest that both the sensitivity and specificity of refractometric sensors may be improved by operating at ultraviolet wavelengths and that measurement at two wavelengths may be used to quantify the total protein present and distinguish between similar proteins, of potential use to reduce false positive responses in affinity assays. The impact of refractive index and particle size on semiconductor-based evanescent field sensors was analyzed, along with the magnitude of optical scattering. The results are particularly important in quantitatively explaining the benefits of using a nanoparticle-enhanced assay, and of using high-index nanoparticles for enhancement. For particles below 100 nm in diameter, optical scattering will be negligible. For particles larger than 100 nm, scattering becomes measurable, and single one-micron diameter particles were detected in a novel monolithic evanescent field sensor. NUMBER OF PAGES 26