Using self-assembled aptamers and fibrinogen-conjugated gold nanoparticles to detect DNA based on controlled thrombin activity.

We have developed a colorimetric probe, based on the aggregation of gold nanoparticles (Au NPs), for the detection of DNA and for the analysis of single-nucleotide polymorphism (SNP); this probe functions through the modulation of the activity of thrombin (Thr) in the presence of bivalent thrombin-binding aptamers (TBAs). The bivalent TBAs were formed from TBA(27') (comprising a 27-base sequence providing TBA(27) functionality, a T(5) linker, and an 11-base sequence for hybridization) and TBA(15') (comprising a 15-base sequence providing TBA(15) functionality, a T(5) linker, and a 12-base sequence for hybridization) through their hybridization with perfectly matched DNA (DNA(pm)). The bivalent TBAs interacted specifically with thrombin, suppressing its activity toward fibrinogen-modified Au NPs (Fib-Au NPs).

Label-free colorimetric detection of picomolar thrombin in blood plasma using a gold nanoparticle-based assay.

We unveil a novel, label-free, colorimetric assay--using fibrinogen (Fib) and gold nanoparticles (Au NPs)--for the highly selective and sensitive detection of thrombin. Addition of fibrinogen to a solution of Au NPs (average diameter: 56 nm) led to ready conjugation, forming Fib-Au NPs through electrostatic and hydrophobic interactions. Introduction of thrombin (a serine protease) into the Fib-Au NPs solutions in the presence of excess fibrinogen induced the formation of insoluble fibrillar fibrin-Au NPs agglutinates through the polymerization of the unconjugated and conjugated fibrinogen.

Separation of amino acids and amines by capillary electrophoresis using poly(ethylene oxide) solution containing cetyltrimethylammonium bromide.

We describe simultaneous analysis of naphthalene-2,3-dicarboxaldehyde (NDA)-amino acid and amine derivatives by capillary electrophoresis in conjunction with light-emitting diode-induced fluorescence (LEDIF) detection using poly(ethylene oxide) (PEO) containing cetyltrimethylammonium bromide (CTAB). In the presence of CTAB and acetonitrile (ACN), adsorption of PEO on the capillary wall is suppressed, leading to generation of a fast and reproducible electroosmotic flow (EOF). In order to optimize separation resolution and speed, 100 mM Tris-borate solution (pH 7.