Maiti Pradip, Saren Ujjal, Chakraborty Utsav, Singha Tanmoy, Paul Sharmistha, Paul Pabitra Kumar
Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032, India.
West Bengal State Council of Science and Technology, Department of Science and Technology and Biotechnology, Vigyan Chetana Bhavan, Sector-I, Salt Lake, Kolkata 700064, India.
ACS Omega. 2022 Aug 12;7(33):29013-29026. doi: 10.1021/acsomega.2c02725. eCollection 2022 Aug 23.
In this communication, we report the comparative and selective interaction of amino acid d-cysteine (d-Cys) with citrate caped gold nanoparticles (Au NPs) in the presence of a fluorescent dye, rhodamine B (RhB), in aqueous solution. Au NPs of size 27.5 nm could almost fully quench the steady-state fluorescence emission of RhB at their optimum concentrations in the mixed solution. The interactions of d-Cys, l-Cys, all other relevant d- and l-amino acids, neurotransmitters, and other relevant biological compounds with the Au NPs/RhB mixed solution have been explored by monitoring the fluorescence recovery efficiencies from the almost fully quenched state of RhB fluorescence via a simple steady-state spectrofluorometric method. The higher fluorescence recovery for the interaction of d-Cys with the Au NPs/RhB mixed system is accompanied by a distinct color change (red-wine to bluish-black) of the assay medium after the reaction compared to that of all other interfering compounds considered in this work. The sensitivity of this fluorometric response lies in a broad linear range of concentrations of d-Cys and the limit of detection (LOD) is found to be 4.2 nM, which is low compared to many other methods available in the literature. The different degrees of interaction of d-Cys and l-Cys with the Au NPs/RhB mixed sample have been further explored by circular dichroism (CD) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The selective interaction of d-Cys with the proposed Au NPs/RhB mixed system is also found to be correlated with interparticle cross-linking and aggregations of nanoparticles by the analysis of ζ potential and dynamic light scattering (DLS) study, transmission electron microscopy (TEM), atomic force microscopy (AFM), UV-vis absorption spectroscopy etc. The proposed interaction mechanism is further studied with a normal human urine sample to elucidate that the optimized combination of Au NPs and RhB may be realized as an efficient platform for detection of the amino acid d-Cys in a real biosample via a simple fluorometric approach.
在本通讯中，我们报道了在水溶液中，荧光染料罗丹明B（RhB）存在的情况下，氨基酸D-半胱氨酸（D-Cys）与柠檬酸盐包覆的金纳米颗粒（Au NPs）之间的比较性和选择性相互作用。尺寸为27.5 nm的Au NPs在混合溶液中的最佳浓度下几乎可以完全淬灭RhB的稳态荧光发射。通过一种简单的稳态荧光光谱法，监测RhB荧光从几乎完全淬灭状态的荧光恢复效率，研究了D-Cys、L-Cys、所有其他相关的D-和L-氨基酸、神经递质以及其他相关生物化合物与Au NPs/RhB混合溶液的相互作用。与本研究中考虑的所有其他干扰化合物相比，D-Cys与Au NPs/RhB混合体系相互作用时较高的荧光恢复伴随着反应后测定介质明显的颜色变化（从红酒色变为蓝黑色）。这种荧光响应的灵敏度在于D-Cys浓度的广泛线性范围，检测限（LOD）为4.2 nM，与文献中许多其他方法相比偏低。通过圆二色性（CD）光谱和傅里叶变换红外（FTIR）光谱进一步研究了D-Cys和L-Cys与Au NPs/RhB混合样品的不同相互作用程度。通过ζ电位分析、动态光散射（DLS）研究、透射电子显微镜（TEM）观察、原子力显微镜（AFM）成像以及紫外可见吸收光谱等手段，发现D-Cys与所提出的Au NPs/RhB混合体系的选择性相互作用还与纳米颗粒间的交联和聚集有关。用正常人尿液样本进一步研究了所提出的相互作用机制，以阐明Au NPs和RhB的优化组合可通过一种简单的荧光方法，作为检测真实生物样品中氨基酸D-Cys的有效平台得以实现。
