Karn-Orachai Kullavadee
National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Pathumthani 12120, Thailand.
Langmuir. 2021 Sep 14;37(36):10776-10785. doi: 10.1021/acs.langmuir.1c01556. Epub 2021 Aug 31.
The development of surface-enhanced Raman scattering (SERS) biosensor platforms based on the sandwich combination of an SERS substrate and Raman reporter coated gold nanoparticle (AuNP) labeled with antibody has been widely performed for highly sensitive detection of biomolecules. The size of biomolecules located between these SERS-active materials dictates the sensitivity enhancement of the sensor. However, no suitable molecular size is provided. In this study, we report the gap-dependent SERS enhancement model using the combination of two SERS-active materials of 2D arrays of gold core-silver shell nanoparticles (Au@Ag core-shell NPs) as SERS-active substrates and mercaptobenzoic acid (MBA)-labeled AuNPs as SERS probes. The distance between these two materials is finely tuned using layer-by-layer assembled polyelectrolyte multilayer films. The morphology of the polyelectrolyte spacer is controlled into a droplet nanostructure, which is assumed to have a comparable shape with globular biomolecules. The well-controlled height or thickness of polyelectrolyte nanodroplet was achieved by changing number of deposition cycles. By increasing the thickness of the polyelectrolyte nanodroplet, MBA SERS intensities gradually decreased until at 40 nm-thick nanodroplet film and maintained afterward. This spacer thickness defined the limit of plasmonic coupling effect from this SERS probe-substrate combination. The SERS enhancement capability of this model was compared to conventional SERS immunoassay using three different antigen-antibody complex sizes of prostate-specific antigen, carcinoembryonic antigen, and carbohydrate antigen 19-9. Good agreement of the limitation of plasmon coupling as a function of the distance between the SERS substrate-probe combination using this developed model and SERS immunoassay was found. The finding provides valuable guidelines for immune-system selection in SERS immunosensors based on SERS substrate-probe combination.
基于表面增强拉曼散射（SERS）基底与用抗体标记的拉曼报告分子包覆的金纳米颗粒（AuNP）的三明治组合构建的SERS生物传感器平台，已被广泛用于生物分子的高灵敏度检测。位于这些SERS活性材料之间的生物分子大小决定了传感器的灵敏度增强效果。然而，并未给出合适的分子大小。在本研究中，我们报道了一种基于间隙依赖性的SERS增强模型，该模型使用了两种SERS活性材料的组合，即金核-银壳纳米颗粒（Au@Ag核壳NP）的二维阵列作为SERS活性基底，以及巯基苯甲酸（MBA）标记的AuNP作为SERS探针。通过层层组装的聚电解质多层膜对这两种材料之间的距离进行精细调节。将聚电解质间隔层的形态控制为液滴纳米结构，假定其形状与球状生物分子相似。通过改变沉积循环次数实现了对聚电解质纳米液滴高度或厚度的良好控制。随着聚电解质纳米液滴厚度的增加，MBA的SERS强度逐渐降低，直到在40 nm厚的纳米液滴膜时达到稳定并保持不变。该间隔层厚度定义了这种SERS探针-基底组合的等离子体耦合效应的极限。使用三种不同抗原-抗体复合物大小的前列腺特异性抗原、癌胚抗原和糖类抗原19-9，将该模型的SERS增强能力与传统SERS免疫分析进行了比较。结果发现，使用该模型和SERS免疫分析得出的等离子体耦合极限与SERS基底-探针组合之间距离的函数关系具有良好的一致性。这一发现为基于SERS基底-探针组合的SERS免疫传感器中免疫系统的选择提供了有价值的指导。
