Mathias Patrick C, Ganesh Nikhil, Cunningham Brian T
Department of Bioengineering, University of Illinois at Urbana-Champaign, IL, USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:1036-8. doi: 10.1109/IEMBS.2009.5335100.
Photonic crystal surfaces are demonstrated as a means for enhancing the detection sensitivity and resolution for assays that use a fluorescent tag to quantify the concentration of an analyte protein molecule in a liquid test sample. Computer modeling of the spatial distribution of resonantly coupled electromagnetic fields on the photonic crystal surface are used to estimate the magnitude of enhancement factor compared to performing the same fluorescent assay on a plain glass surface, and the photonic crystal structure is fabricated and tested to experimentally verify the performance using a sandwich immunoassay for the protein Tumor Necrosis Factor-alpha (TNF-alpha). The demonstrated photonic crystal fabrication method utilizes a nanoreplica molding technique that allows for large-area inexpensive fabrication of the structure in a format that is compatible with confocal microarray laser scanners. The signal-to-noise ratio for fluorescent spots on the photonic crystal is increased by at least five-fold relative to the glass slide, allowing a TNF-alpha concentration of 1.6 pg/ml to be distinguished from noise on a photonic crystal surface. In addition, the minimum quantitative limit of detection on the photonic crystal surface is one-third the limit on the glass slide - a decrease from 18 pg/ml to 6 pg/ml. The increased performance of the immunoassay allows for more accurate quantitation of physiologically relevant concentrations of TNF-alpha in a protein microarray format that can be expanded to multiple cytokines.
光子晶体表面被证明是一种提高检测灵敏度和分辨率的手段，用于那些使用荧光标记来定量液体测试样品中分析物蛋白质分子浓度的检测方法。通过对光子晶体表面共振耦合电磁场的空间分布进行计算机建模，来估计与在普通玻璃表面进行相同荧光检测相比的增强因子大小。制造并测试了光子晶体结构，使用针对蛋白质肿瘤坏死因子-α（TNF-α）的夹心免疫分析法通过实验验证其性能。所展示的光子晶体制造方法采用了纳米复制成型技术，该技术能够以与共聚焦微阵列激光扫描仪兼容的形式大面积廉价地制造该结构。相对于载玻片，光子晶体上荧光点的信噪比提高了至少五倍，使得在光子晶体表面能够将1.6 pg/ml的TNF-α浓度与噪声区分开来。此外，光子晶体表面的最低定量检测限是载玻片上检测限的三分之一——从18 pg/ml降至6 pg/ml。免疫分析性能的提高使得能够以蛋白质微阵列形式更准确地定量生理相关浓度的TNF-α，并且该形式可以扩展到多种细胞因子。
