Quantum Dots–Ligand Complex as Ratiometric Fluorescent Nanoprobe for Visual and Specific Detection of G‑Quadruplex

By complexing a nonionic G-quadruplex ligand with hybrid dual-emission quantum dots (QDs), a ratiometric fluorescent nanoprobe is developed for G-quadruplex detection in a sensitive and specific manner. The QDs nanohybrid comprised of a green-emission QD (gQD) and multiple red-emission QDs (rQDs) inside and outside of a silica shell, respectively, is utilized as the signal displaying unit. Only the presence of G-quadruplex can displace the ligand from QDs, breaking up the QDs–ligand complexation, and inducing the restoration of the rQDs fluorescence. Since the fluorescence of embedded gQD stays constant, variations of the dual-emission intensity ratios display continuous color changes from green to bright orange, which can be clearly observed by the naked eye. Furthermore, by utilizing competitive binding of a cationic ligand versus the nonionic ligand toward G-quadruplex, the nanoprobe is demonstrated to be applicable for assessing the affinity of a G-quadruplex-targeted anticancer drug candidate, exhibiting ratiometric fluorescence signals (reverse of that for G-quadruplex detection). By making use of the specificity of the ligand binding with G-quadruplex against a double helix, this nanoprobe is also demonstrated to be capable of sensitive detection of one-base mutation, exhibiting sequence-specific ratiometric fluorescence signals. By functionalizing with a nuclear localization peptide, the nanoprobe can be used for visualization of G-quadruplex in the nucleus of human cells

Coating Urchinlike Gold Nanoparticles with Polypyrrole Thin Shells To Produce Photothermal Agents with High Stability and Photothermal Transduction Efficiency

Photothermal therapy using inorganic nanoparticles (NPs) is a promising technique for the selective treatment of tumor cells because of their capability to convert the absorbed radiation into heat energy. Although anisotropic gold (Au) NPs present an excellent photothermal effect, the poor structural stability during storage and/or upon laser irradiation still limits their practical application as efficient photothermal agents. With the aim of improving the stability, in this work we adopted biocompatible polypyrrole (PPy) as the shell material for coating urchinlike Au NPs. The experimental results indicate that a several nanometer PPy shell is enough to maintain the structural stability of NPs. In comparison to the bare NPs, PPy-coated NPs exhibit improved structural stability toward storage, heat, pH, and laser irradiation. In addition, the thin shell of PPy also enhances the photothermal transduction efficiency (η) of PPy-coated Au NPs, resulting from the absorption of PPy in the red and near-infrared (NIR) regions. For example, the PPy-coated Au NPs with an Au core diameter of 120 nm and a PPy shell of 6.0 nm exhibit an η of 24.0% at 808 nm, which is much higher than that of bare Au NPs (η = 11.0%). As a primary attempt at photothermal therapy, the PPy-coated Au NPs with a 6.0 nm PPy shell exhibit an 80% death rate of Hela cells under 808 nm NIR laser irradiation

Polypyrrole-Coated Chainlike Gold Nanoparticle Architectures with the 808 nm Photothermal Transduction Efficiency up to 70%

Aqueous Au nanoparticles (NPs) are employed as the building blocks to construct chainlike self-assembly architectures, which greatly enhance the photothermal performance at 808 nm. Biocompatible polypyrrole (PPy) is further adopted as the package material to coat Au NP chains, producing stable photothermal agents. As a result of contributions from chainlike Au, the PPy shell, as well as the Au–PPy composite structures, the capability of photothermal transduction at 808 nm is greatly enhanced, represented by the high photothermal transduction efficiency up to 70%. Primary animal experiment proves that the current composite photothermal agents are efficient in inhibiting tumor growth under an 808 nm irradiation, showing the potentials for in vivo photothermal therapy