Gold nanoparticles(Au NPs) have been extensively used in optical biosensing and bioimaging due to the unique optical properties. Biological applications including biosensing and cellular imaging based on optical properties of Au NPs will be reviewed in the paper. The content will focus on detection principles, advantages and challenges of these approaches as well as recent advances in this field.
There is an increasing demand for advanced optical imaging techniques that can detect and resolve nanosize objects at a spatial resolution below the optical diffraction limit, especially in three-dimensional （3D） cellular environments. In this study, using a polarization-activated localization scheme based on the orientation-dependent properties of anisotropic plasmonic metal nanoparticles （MNPs）, ＂photoswitchable＂ imaging of single gold nanorods （AuNRs） was accomplished not only in two dimensions but also in three dimensions. Moreover, the Rayleigh scattering background arising from the congested subcellular structures was efficiently suppressed. Thus, we obtained the 3D distributions of both the position and the orientation of the AuNRs inside the cells and investigated their intemalization kinetics. To our knowledge, this is the first demonstration of the confocal-like 3D imaging of non-fluorescence nanoparticles with a high resolution and almost zero background. This technique is easy to implement and should greatly facilitate MNP studies and applications in biomedicine and biology.
Xiaodong ChengXuan CaoBin XiongYan HeEdward S. Yeung
The Ru（bpy）3^2＋ doped graphene oxide-silica composite film（Ru/GO-SiCF） was synthesized by one pot hydrolysis and condensation of tetraethylorthosilicate（TEOS） in the water-alcohol solution of graphene oxide and Ru（bpy）3^2＋ at room temperature.The prepared Ru/GO-SiCF modified glassy carbon electrode（GCE） showed excellent electrochemiluminescence（ECL） behavior for the determination of tripropylamine（TPA） with high sensitivity and good stability.We expected this simple and novel material will find further application in construction of other targets sensors.
Gen-Ping YanXiao-Xiao HeKe-Min WangYong-Hong WangJin-Quan LiuLi-Xin JianYin-Fei Mao
The plasma membrane possesses a complicated structure, on which the protein clusters are randomly but orderly distributed to maintain the regular morphology and function of cells. Investigating the detailed dynamic behaviors of nanoparticles(NPs) on cytomembrane is of great importance to understand cellular mechanisms and advance the bio-nano technologies for drug delivery, photothermal therapy, immunotherapy, etc. In this work, to study the dynamic heterogeneous interactions between NPs and cell membrane with high resolution, we established a simple method to efficiently track the translational and rotational diffusion of individual gold nanorods(AuNRs) on cell membranes. This method is based on that an anisotropic AuNR appears as a colored spot under a darkfield microscope(DFM) equipped with a color camera. While obtaining its lateral position, the polar angle of the AuNR can be calculated simultaneously from intensity difference between the R and G channels. Careful analysis shows that the lateral motion of single AuNRs do not follow normal Brownian diffusion, which could be attributed to their hop diffusion in the dynamically varying picket-fence structure of the live cell membrane. Furthermore, 4 different rotationtranslation patterns of the AuNR are observed due to spatiotemporal heterogeneity of the cytomembrane. This simple but robust method for simultaneously obtaining the location and orientation of anisotropic plasmonic nanoparticles could be further applied to the analysis of complicated biological and biomedical processes.
In this paper,we proposed a facile and accurate way for controlling multiplex fluorescent logic gates through changing the exciting and the observing wavelengths.As proof-of-principle,a Pb2+-specific DNAzyme probe and a thymine(T)-rich DNA probe were introduced to a double-stranded(ds-)DNA.The addition style of the two ions served as the four inputs by changing the distance of the three fluorophores,6-carboxyfluorescein(FAM),ALEXA 532(ALEXA)and carboxytetramethylrhodamine(TAMRA),all of which were modified on the dsDNA probe.Compared with the previous methods,the present approach needed neither different inputs nor the change of sequence of the probe to achieve multiplex logic gates.Furthermore,the modularity of the strategy may allow it to be extended to other types of logic gates.
TAO JiaZHENG JingLI JiShanZHAO PengLI JuanPingMA ChengYI MeiYANG RongHua
We present here a pH-responsive activatable aptamer probe for targeted cancer imaging based on i-motif-driven conformation alteration. This pH-responsive activatable aptamer probe is composed of two single-stranded DNA. One was used for target recognition, containing a central, target specific aptamer sequence at the 3＇-end and an extension sequence at the 5＇-end with 5-carboxytetramethylrhodamine （TAMRA） label （denoted as strand A）. The other （strand ｜）, being competent to work on the formation of i-motif structure, contained four stretches of the cytosine （C） rich domain and was labeled with a Black Hole Quencher 2 （BHQ2） at the 3＇-end. At neutral or slightly alkaline pH, strand ｜ was hybridized to the extension sequence of strand A to form a double-stranded DNA probe, termed i-motif-based activatable aptamer probe （I-AAP）. Because of proximity- induced energy transfer, the I-AAP was in a ＂signal off＇ state. The slightly acidic pH enforced the strand I to form an intramo- lecular i-motif and then initiated the dehybridization of I-AAP, leading to fluorescence readout in the target recognition. As a demonstration, AS1411 aptamer was used for MCF-7 cells imaging. It was displayed that the I-AAP could be carried out for target cancer cells imaging after being activated in slightly acidic environment. The applicability of I-AAP for tumor tissues imaging has been also investigated by using the isolated MCF-7 tumor tissues. These results implied the I-AAP strategy is promising as a novel approach for cancer imaging.
