Department of Bioengineering, McGill University, Montreal, Quebec H3A 0E9, Canada.
Biological Sciences, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario M4N 3M5, Canada.
ACS Appl Mater Interfaces. 2020 May 20;12(20):23298-23310. doi: 10.1021/acsami.0c02654. Epub 2020 May 7.
Hierarchical 3D gold nano-/microislands (NMIs) are favorably structured for direct and probe-free capture of bacteria in optical and electrochemical sensors. Moreover, their unique plasmonic properties make them a suitable candidate for plasmonic-assisted electrochemical sensors, yet the charge transfer needs to be improved. In the present study, we propose a novel plasmonic-assisted electrochemical impedimetric detection platform based on hybrid structures of 3D gold NMIs and graphene (Gr) nanosheets for probe-free capture and label-free detection of bacteria. The inclusion of Gr nanosheets significantly improves the charge transfer, addressing the central issue of using 3D gold NMIs. Notably, the 3D gold NMIs/Gr detection platform successfully distinguishes between various types of bacteria including () K12, (), and (. ) when electrochemical impedance spectroscopy is applied under visible light. We show that distinguishable and label-free impedimetric detection is due to dissimilar electron charge transfer caused by various sizes, morphologies, and compositions of the cells. In addition, the finite-difference time-domain (FDTD) simulation of the electric field indicates the intensity of charge distribution at the edge of the NMI structures. Furthermore, the wettability studies demonstrated that contact angle is a characteristic feature of each type of captured bacteria on the 3D gold NMIs, which strongly depends on the shape, morphology, and size of the cells. Ultimately, exposing the platform to various dilutions of the three bacteria strains revealed the ability to detect dilutions as low as ∼20 CFU/mL in a wide linear range of detection of 2 × 10-10, 2 × 10-10, and 1 × 10-1 × 10 CFU/mL for , , and , respectively. The proposed hybrid structure of 3D gold NMIs and Gr, combined by novel plasmonic and conventional impedance spectroscopy techniques, opens interesting avenues in ultrasensitive label-free detection of bacteria with low cost and high stability.
分层 3D 金纳米-/微岛（NMI）结构有利于在光学和电化学传感器中直接且无需探针捕获细菌。此外，其独特的等离子体特性使其成为等离子体辅助电化学传感器的合适候选者，但需要改进电荷转移。在本研究中，我们提出了一种基于 3D 金 NMI 和石墨烯（Gr）纳米片的混合结构的新型等离子体辅助电化学阻抗检测平台，用于无需探针捕获和无标记检测细菌。Gr 纳米片的包含显著提高了电荷转移，解决了使用 3D 金 NMI 的核心问题。值得注意的是，当在可见光下应用电化学阻抗谱时，3D 金 NMI/Gr 检测平台成功区分了各种类型的细菌，包括（）K12、（）和（）。我们表明，由于细胞的大小、形态和组成的不同，导致了不同的电子电荷转移，从而实现了可区分的无标记阻抗检测。此外，电场的有限差分时间域（FDTD）模拟表明了 NMI 结构边缘的电荷分布强度。此外，润湿性研究表明，接触角是每种类型的细菌在 3D 金 NMI 上的捕获特征，这强烈依赖于细胞的形状、形态和大小。最终，将该平台暴露于三种细菌菌株的不同稀释度中，表明该平台能够在检测范围内检测低至约 20 CFU/mL 的稀释度，检测范围为 2×10-10、2×10-10 和 1×10-1×10 CFU/mL ，分别为、和。3D 金 NMI 和 Gr 的这种混合结构，结合了新颖的等离子体和传统的阻抗光谱技术，为低成本、高稳定性的细菌无标记超灵敏检测开辟了新途径。
