Yi-Hsuan Tang

Metallodendrimers and Dendrimer Nanocomposites

Dendrimers are polymeric compounds with highly branched structures and functionally tunable peripheral groups. Because of their low polydispersity, high degree of molecular uniformity, and precisely controlled structure, dendrimers are excellent models for demonstrating a variety of biological activities. With the attachment of metals ions and/or metals, metallodendrimers or dendrimer nanocomposites, respectively, provide diverse characters for a variety of applications. Functionalization with additional moieties, such as targeted peptides or chromophores, yields metallodendrimers that can find powerful applications and exceed the capabilities of nondendritic molecules or small molecule analogs. This review introduces the background of metallodendrimers and dendrimer nanocomposites. Biomedical applications of metallodendrimers and dendrimer nanocomposites will be discussed, including biomimetic catalysts, imaging contrast agents (especially for MRI imaging), or biomedical sensors and therapeutic agents.

Extraction of Cupric Ions with Ionic Liquids Containing Polypyridine-type Small Molecules or Peripherally Pyridine-modified Dendrimers

The hydrophobic ionic liquid N-butyl-N-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide (BMP-TFSA IL), which contains a series of flexible ionophores of polypyridine-type small molecules or two rigid ionophores of peripherally pyridine-modified PAMAM dendrimers, was used to extract cupric ions from aqueous solutions. The polypyridine-type ionophores show good selectivity toward cupric ions at pH 2. The selectivity is affected by the spacing between the two amino groups. However, the pyridine-modified dendrimers showed poor selectivity, although their extraction efficiency still depended on the pH of the aqueous solution. The ionic liquids that contained small molecular ionophores and their dendrimer analogs were reused after acid washing or electrochemical reduction. During acid washing, the nitrogen atoms of the ionophores were protonated to release the cupric ions into the aqueous phase, and the copper atoms were deposited onto the electrode surface during the electrochemical reduction accompanied by the regeneration of the ionophores.

Mannosyl electrochemical impedance cytosensor for label-free MDA-MB-231 cancer cell detection

A label-free and ultrasensitive electrochemical impedance cytosensor was developed to specifically detect the breast cancer cells MDA-MB-231 via the interaction between the mannosyl glassy carbon electrode (GCE) and the overexpressed mannose receptors on the target cell surface. The mannosyl GCE was prepared through electrografting of the amino-functionalized mannose derivatives on GCE surface in which a covalent bond was formed between carbon of the electrode and the amino group of the mannose derivative. The fluorescent microscopy indicated that the electrode is specific for MDA-MB-231 cells, with good biocompatibility for viable captured cells. The derivative with a shorter alkyl linker, mannose-C2NH2, showed a better sensitivity than that with a longer linker, mannose-C6NH2. GCE modified with amino-functionalized galactose derivative, galactose-C2NH2, shows no function to the detection of MDA-MB-231 cells. The specific interaction between the mannosyl GCE and Con A (a mannose-binding lectin) or MDA-MB-231 breast cancer cells with overexpressed mannose receptors was determined through the change of peak separation in the cyclic voltammogram or the change of charge transfer resistance in the electrochemical impedance spectra (Nyquist plot) in the electrolytes containing a reversible redox couple [Fe(CN)6]3-/[Fe(CN)6]4-. The charge transfer resistance in the Nyquist plots linearly depended on the concentration of MDA-MB-231 cells (1.0 × 10-1.0 × 105 cells mL-1, with 10 cells mL-1 being the lower detection limit). Introducing 0.1% polyethylene glycol-200 (PEG-200) was able to prevent the interference caused by 1.0 × 103 HEK-293T cells mL-1, a non-cancer cell line (control).