EMT Research Center, Institut National de la Recherche Scientifique (INRS), Varennes, Quebec J3X 1S2, Canada.
Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada.
Biomacromolecules. 2020 Jul 13;21(7):2705-2713. doi: 10.1021/acs.biomac.0c00401. Epub 2020 Jul 1.
In this study, an engineered M13 bacteriophage was examined as a biological template to create a well-defined spacing between very small gold nanoparticles (AuNPs 3-13 nm). The effect of the AuNP particle size on the enhancement of the nonlinear process of two-photon excitation fluorescence (2PEF) was investigated. Compared to conventional (one-photon) microscopy techniques, such nonlinear processes are less susceptible to scattering given that the density of background-scattered photons is too low to generate a detectable signal. Besides this, the use of very small AuNPs in 2PEF microscopy becomes more advantageous because individual "isolated" AuNPs of this size do not sufficiently enhance 2PEF to produce a detectable signal, resulting in even less background signal. To investigate the 2PEF of the AuNP-M13 assemblies, a variety of sample preparation approaches are tested, and surface-enhanced Raman spectroscopy (SERS) is employed to study the strength of plasmon coupling within the gaps of AuNPs assembled on the M13 template. Results indicate that assemblies prepared with 9-13 nm AuNP were able to clearly label cells and produce a 2PEF signal that was orders of magnitude higher than the isolated AuNP (below the threshold of detection). This study thus provides a better understanding of the opportunities and limitations relevant to the use of such small AuNPs within colloidal plasmonic assemblies, for applications in biodetection or as imaging contrast agents.
在这项研究中，我们考察了一种经过工程改造的 M13 噬菌体，将其作为一种生物模板，在非常小的金纳米粒子（3-13nm 的 AuNPs）之间创造出明确的间隔。研究了 AuNP 粒径对双光子激发荧光（2PEF）非线性过程增强的影响。与传统的（单光子）显微镜技术相比，由于背景散射光子的密度太低而无法产生可检测的信号，这种非线性过程不太容易受到散射的影响。此外，在 2PEF 显微镜中使用非常小的 AuNP 变得更加有利，因为这种尺寸的单个“孤立”AuNP 不足以增强 2PEF 以产生可检测的信号，从而导致更少的背景信号。为了研究 AuNP-M13 组装体的 2PEF，我们测试了多种样品制备方法，并采用表面增强拉曼光谱（SERS）研究了组装在 M13 模板上的 AuNP 间隙内等离子体耦合的强度。结果表明，用 9-13nm AuNP 制备的组装体能够清晰标记细胞，并产生比孤立 AuNP（低于检测阈值）高几个数量级的 2PEF 信号。因此，这项研究更好地理解了在胶体等离子体组装体中使用如此小的 AuNP 的相关机会和限制，这对于生物检测或作为成像对比剂的应用具有重要意义。
