Department of Chemistry, University of British Columbia , 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
Anal Chem. 2013 Sep 17;85(18):8817-25. doi: 10.1021/ac4020066. Epub 2013 Aug 27.
Paper-based assays are a promising diagnostic format for point-of-care applications, field deployment, and other low-resource settings. To date, the majority of efforts to integrate nanomaterials with paper-based assays have utilized gold nanoparticles. Here, we show that semiconductor quantum dots (QDs), in combination with Förster resonance energy transfer (FRET), are also suitable nanomaterials for developing paper-based assays. Paper fibers were chemically modified with thiol ligands to immobilize CdSeS/ZnS QDs, the QDs were self-assembled with dye-labeled peptides to generate efficient FRET, and steady-state and fluorescence lifetime imaging microscopy (FLIM) were used for characterization. Peptides were selected as substrates for three different proteases and a series of kinetic assays for proteolytic activity was carried out, including multiplexed assays and pro-enzyme activation assays. Quantitative results were obtained within 5-60 min at levels as low as 1-2 nM of protease. These assays were possible using simple optical readout platforms that did not negate the low cost, ease of use, and overall accessibility advantages of paper-based assays. A violet light-emitting diode (LED) excitation source and color imaging with either a digital camera, consumer webcam, or smartphone camera were sufficient for analysis on the basis of a red/green color intensity ratio. At most, a universal serial bus (USB) connection to a computer was required and the instrumentation cost orders of magnitude less than that typically utilized for in vitro bioanalyses with QDs. This work demonstrates that QDs are valuable probes for developing a new generation of paper-based diagnostics.
基于纸的分析物是一种有前途的即时诊断格式，适用于现场部署和其他资源匮乏的环境。迄今为止，将纳米材料与基于纸的分析物集成的大多数努力都利用了金纳米颗粒。在这里，我们表明，半导体量子点（QD）与Förster 共振能量转移（FRET）结合使用，也是开发基于纸的分析物的合适纳米材料。纸纤维经过化学修饰，接上硫醇配体来固定 CdSeS/ZnS QD，然后 QD 与染料标记的肽自组装，生成高效的 FRET，利用稳态和荧光寿命成像显微镜（FLIM）进行表征。选择肽作为三种不同蛋白酶的底物，并进行一系列的酶活性动力学测定，包括多重测定和酶原激活测定。在低至 1-2 nM 蛋白酶的水平下，在 5-60 分钟内即可获得定量结果。这些分析物可以使用简单的光学读出平台进行分析，这些平台不会否定基于纸的分析物的低成本、易用性和整体可及性优势。基于红/绿颜色强度比，只需使用紫光发光二极管（LED）激发源和数字相机、消费级网络摄像头或智能手机摄像头进行彩色成像即可进行分析。最多只需要通过通用串行总线（USB）与计算机连接，仪器成本比通常用于 QD 进行体外生物分析的成本低几个数量级。这项工作表明，QD 是开发新一代基于纸的诊断方法的有价值的探针。
