Department of Chemistry & Biochemisty, Calvin College, 1726 Knollcrest Circle SE, Grand Rapids, Michigan 49546, United States.
ACS Nano. 2012 Sep 25;6(9):8078-86. doi: 10.1021/nn303347k. Epub 2012 Aug 27.
Single-particle analysis of biosensors that use charge transfer as the means for analyte-dependent signaling with semiconductor nanoparticles, or quantum dots, was examined. Single-particle analysis of biosensors that use energy transfer show analyte-dependent switching of nanoparticle emission from off to on. The charge-transfer-based biosensors reported here show constant emission, where the analyte (maltose) increases the emission intensity. By monitoring the same nanoparticles under various conditions, a single charge-transfer-based biosensor construct (one maltose binding protein, one protein attachment position for the reductant, one type of nanoparticle) showed a dynamic range for analyte (maltose) detection spanning from 100 pM to 10 μM while the emission intensities increase from 25 to 175% at the single-particle level. Since these biosensors were immobilized, the correlation between the detected maltose concentration and the maltose-dependent emission intensity increase could be examined. Minimal correlation between maltose detection limits and emission increases was observed, suggesting a variety of reductant-nanoparticle surface interactions that control maltose-dependent emission intensity responses. Despite the heterogeneous responses, monitoring biosensor emission intensity over 5 min provided a quantifiable method to monitor maltose concentration. Immobilizing and tracking these biosensors with heterogeneous responses, however, expanded the analyte-dependent emission intensity and the analyte dynamic range obtained from a single construct. Given the wide dynamic range and constant emission of charge-transfer-based biosensors, applying these single molecule techniques could provide ultrasensitive, real-time detection of small molecules in living cells.
本文研究了基于电荷转移的生物传感器的单颗粒分析，该生物传感器使用半导体纳米粒子（或量子点）作为分析物依赖信号的手段。基于能量转移的生物传感器的单颗粒分析显示，纳米颗粒的发射从关闭到打开取决于分析物的切换。这里报道的基于电荷转移的生物传感器显示出恒定的发射，其中分析物（麦芽糖）增加了发射强度。通过在各种条件下监测相同的纳米粒子，一个基于单电荷转移的生物传感器结构（一个麦芽糖结合蛋白、一个还原剂的蛋白附着位置、一种类型的纳米粒子）显示出分析物（麦芽糖）检测的动态范围从 100 pM 到 10 μM，而发射强度在单颗粒水平上从 25%增加到 175%。由于这些生物传感器是固定的，因此可以检测到麦芽糖浓度与麦芽糖依赖的发射强度增加之间的相关性。观察到麦芽糖检测限与发射增加之间的最小相关性，表明存在各种还原剂-纳米粒子表面相互作用，控制麦芽糖依赖的发射强度响应。尽管存在异质响应，但监测生物传感器发射强度超过 5 分钟提供了一种可量化的方法来监测麦芽糖浓度。然而，固定化和跟踪这些具有异质响应的生物传感器，扩展了从单个结构获得的麦芽糖依赖的发射强度和分析物的动态范围。鉴于基于电荷转移的生物传感器具有宽的动态范围和恒定的发射，应用这些单分子技术可以提供对活细胞中小分子的超灵敏、实时检测。
