Protein-directed synthesis of highly fluorescent gold ..
The size-dependent optical properties and good biocompatibility of the prepared GNPs, show us that they have potential in application (e.g. drug delivery, biodiagnostics, optical imaging, detection of ions and biomolecules),,,. Besides, the green-chemical reducing and stabilizing agents of proteins, which can withstand a wide range of pH conditions due to their complex 3D structures,, make the prepared GNPs being a great application prospect in many areas. Considering that the relative and absolute level of proteins in human body is directly related to specific disease states,,,, we are interested in seeking an efficient method to identify protein balances by using the size-dependent optic properties of GNPs. The prepared GNPs with different sizes and colors are investigated in the field of multidimensional sensing. Recently, multidimensional sensing platforms have been employed for pattern recognition analysis of multiple analytes, especially proteins,,,,,,,,,,,. For example, the GNPs modified by fluorescent polymer or proteins have been applied to detect proteins,. Liu et al. presented a multidimensional sensor for pattern recognition of proteins with DNA sequences modified GNPs (DNA−GNPs). Yan et al. reported the simultaneous exploration of the fluorescence, phosphorescence, and scattering properties of manganese-doped ZnS quantum dots as a multidimensional sensing device for the discrimination of proteins. The groups of He and Zhang prepared dual-ligand cofunctionalized gold nanodots and quantum dots to detect proteins via fluorescence response,, respectively. These efforts have made great progress toward developing the multidimensional sensing systems for the discrimination of proteins, however, they either require complicated modification process and/or need a variety of techniques (or instruments) to acquire sensing signals, thus limiting their widespread applications. It is important that such studies achieving the discrimination of proteins in the process of GNPs synthesis, without further modification and fluorescence excitation, are currently unavailable. In this paper, a multidimensional sensing platform is created based on the in-situ reduction method to produce the distinct color of GNPs and simultaneously differentiate proteins, simply by extracting the color changes of the Au(I) anions, luminol and H2O2 mixture in the absence and presence of different proteins. Compared with the reported sensor arrays, three obvious advantages of this sensor array might be particularly attractive: i) Protein can be immediately discriminated in the GNPs synthesis process, without further surface modification; ii) Protein discrimination can be achieved only by extracting color responses, without the utilization of expensive instruments; iii) The as-developed sensing platform also exhibits great potentials in semiquantitative analysis of individual protein with high sensitivity. In final, the as-developed multidimensional sensing platform is validated by analysis of the spiked proteins in human urine and determination of target proteins in complex matrix (e.g. lysozyme in human tear).
“Protein-directed synthesis of highly fluorescent gold ..
57. Wang C, Wang C, Xu L. . Protein-directed synthesis of pH-responsive red fluorescent copper nanoclusters and their applications in cellular imaging and catalysis. 2014;6:1775-81
Gold-based nanomaterials have attracted much attention in many areas of chemistry, physics, materials science, and biosciences because of their size- and shape-dependent optic, electric, and catalytic properties. Synthesis of spherical gold nanoparticles (GNPs) involves the chemical reduction of chloroauric acid (HAuCl4) typically using sodium borohydride (NaBH4) and sodium citrate as the reducing agents,, producing particles with sizes of 2–10 and 10–40nm, respectively. To date, seeded growth strategies are usually used to efficiently synthesize uniform GNPs larger than 40nm,,,. That is, small GNPs, obtained via NaBH4/citrate reduction, are employed as gold seeds and HAuCl4 is reduced to Au0 atop the seeds by using additional reducing agents, such as ascorbic acid,, hydroxylamine, mercaptosuccinic acid, hydroquinone, and N2H4·2HCl. However, most of these chemicals are highly active and have potential environmental and biological risks, which might be an issue for their wide applications. The environmental friendly approach to synthesize GNPs by using natural macromolecules has been attracted growing interest in the last few decades,,,,. For example, the groups of Yang used chitosan for reduction of Au3+ and stabilization of GNPs. Cellulose has been reported as reducing agent for the “green” synthesis of GNPs. The spider-silk fiber has been utilized as reducing agent to synthesize GNPs. The green natural compounds, plant extracts, were reported to synthesize well-dispersed GNPs,. Among the biomacromolecules, proteins that have been widely used in nanoclusters (nm) synthesis,, are the ideal candidate for synthesis of GNPs. Herein, we present the first reported an in-situ reduction method to synthesize the monodispersed and spherical GNPs with sizes of beyond 40nm by using proteins, the reducing powers of which are activated by H2O2 and the superoxide anion (). The in-situ reduction method to synthesize GNPs as shown in , addition of certain proteins (e.g. collagen (Col)) to HAuCl4 solution, turns Au(III) to Au(I) anions, which are further reduced by other proteins in the presence of luminol and H2O2, to form spherical GNPs with different sizes.