Histidine–dialkoxyanthracene dyad for selective and sensitive detection of mercury ions

<p>Histidine-dialkoxyanthracene (HDA) was synthesised as a turn off type fluorescent sensor for fast and sensitive detection of mercury ions (Hg²⁺) in aqueous media. The two histidine moieties act as ‘claws’ to selectively complex Hg²⁺. The binding ratio of HDA to Hg²⁺ was 1:1 (metal-to-ligand ratio). The association constant for Hg²⁺ towards the receptor HDA obtained from Benesi–Hildebrand plot was found to be 3.22 × 10⁴ M⁻¹ with detection limit as low as 4.7 nM (0.94 μg/L).</p

Tunable and Linker Free Nanogaps in Core–Shell Plasmonic Nanorods for Selective and Quantitative Detection of Circulating Tumor Cells by SERS

Controlling the size, number, and shape of nanogaps in plasmonic nanostructures is of significant importance for the development of novel quantum plasmonic devices and quantitative sensing techniques such as surface-enhanced Raman scattering (SERS). Here, we introduce a new synthetic method based on coordination interactions and galvanic replacement to prepare core–shell plasmonic nanorods with tunable enclosed nanogaps. Decorating Au nanorods with Raman reporters that strongly coordinate Ag⁺ ions (e.g., 4-mercaptopyridine) afforded uniform nucleation sites to form a sacrificial Ag shell. Galvanic replacement of the Ag shell by HAuCl₄ resulted in Au–AgAu core–shell structure with a uniform intra-nanoparticle gap. The size (length and width) and morphology of the core–shell plasmonic nanorods as well as the nanogap size depend on the concentration of the coordination complexes formed between Ag⁺ ions and 4-mercaptopyridine. Moreover, encapsulating Raman reporters within the nanogaps afforded an internal standard for sensitive and quantitative SERS analysis. To test the applicability, core–shell plasmonic nanorods were functionalized with aptamers specific to circulating tumor cells such as MCF-7 (Michigan Cancer Foundation-7, breast cancer cell line). This system could selectively detect as low as 20 MCF-7 cells in a blood mimicking fluid employing SERS. The linking DNA duplex on core–shell plasmonic nanorods can also intercalate hydrophobic drug molecules such as Doxorubicin, thereby increasing the versatility of this sensing platform to include drug delivery. Our synthetic method offers the possibility of developing multifunctional SERS-active materials with a wide range of applications including biosensing, imaging, and therapy

Impact of Pore–Walls Ligand Assembly on the Biodegradation of Mesoporous Organosilica Nanoparticles for Controlled Drug Delivery

Porous materials with molecular-scale ordering have attracted major attention mainly because of the possibility to engineer their pores for selective applications. Periodic mesoporous organosilica is a class of hybrid materials where self-assembly of the organic linkers provides a crystal-like pore wall. However, unlike metal coordination, specific geometries cannot be predicted because of the competitive and dynamic nature of noncovalent interactions. Herein, we study the influence of competing noncovalent interactions in the pore walls on the biodegradation of organosilica frameworks for drug delivery application. These results support the importance of studying self-assembly patterns in hybrid frameworks to better engineer the next generation of dynamic or “soft” porous materials