A label-free method for the detection of specific DNA sequences using gold nanoparticles bifunctionalized with a chemiluminescent reagent and a catalyst as signal reporters

Sensitive, specific, simple, fast, and low-cost DNA detection methods are extremely important in clinical diagnostics, gene therapy, and a variety of biomedical studies. In this work, we developed a general method for the detection of specific DNA sequences from Mycobacterium tuberculosis (TB), hepatitis B virus (HBV), and myelocytomatosis viral oncogene (v-myc) using gold nanoparticles bifunctionalized with both a chemiluminescent (CL) reagent and a catalytic metal complex as signal reporters and a DNA strand complementary to the target as the capture probe. In this CL method, a biotinylated single-strand DNA capture probe was immobilized in a streptavidin-coated microwell. Upon the addition of the target single-strand DNA, the capture probe hybridized with the target DNA. After adding the bifunctionalized gold nanoparticles and H₂O₂, a well-defined CL signal was obtained, and the CL intensity was observed to change as the target DNA concentration was increased. It was possible to determine the concentration of the target TB single-strand DNA in the range 1.0 × 10^-13-1.0 × 10^-8 M with a detection limit of 4.8 × 10^-14 M. HBV single-strand DNA and v-myc single-strand DNA could also be determined in the range 1.0 × 10^-11-1.0 × 10^-8 M with detection limits of 5.9 × 10^-12 M and 8.0 × 10^-12 M, respectively, using this CL technique. The method reported in this paper is the first label-free CL method for the determination of specific DNA sequences to utilize gold nanoparticles bifunctionalized with both a CL reagent and a catalytic metal complex. The sensitivity of this CL method is superior to those of most previously reported label-free methods. Compared with methods that use polymerase chain reaction amplification, this label-free CL method is much simpler, faster, and more economic. This work has thus demonstrated a simple and fast scanning strategy for the detection of specific DNA sequences related to diseases. Graphical Abstract Schematic illustration of label-free CL method for detection of specific DNA sequences.

Determination of the binding constant of specific interactions and binding target concentration simultaneously using a general chemiluminescence method

The measurement of the binding constant of specific interactions and concentration of a target is of considerable importance in clinical diagnosis, therapy, bioassays and drug design.

A general chemiluminescence strategy for measuring aptamer-target binding and target concentration

Although much effort has been made for studies on aptamer-target interactions due to promising applications of aptamers in biomedical and analytical fields, measurement of the aptamer-target binding constant and binding site still remains challenging. Herein, we report a sensitive label-free chemiluminescence (CL) strategy to determine the target concentration and, more importantly, to measure the target-aptamer binding constant and binding site. This approach is suitable for multiple types of targets, including small molecules, peptides, and proteins that can enhance the CL initiated by N-(aminobutyl)-N-ethylisoluminol functionalized gold colloids, making the present method a general platform to investigate aptamer-target interactions. This approach can achieve extremely high sensitivity with nanogram samples for measuring the target-aptamer binding constant. And the measurement could be rapidly performed using a simple and low-cost CL system. It provides an effective tool for studying the binding of biologically important molecules to nucleic acids and the selection of aptamers. Besides, we have also discovered that the 14-mer aptamer fragment itself split from the ATP-binding aptamer could selectively capture ATP. The binding constant, site, and conformation between ATP and the 14-mer aptamer fragment were obtained using such a novel CL strategy and molecular dynamic simulation.

5-hydroxytryptophan is a more potent in vitro hydroxyl radical scavenger than melatonin or vitamin C

Hydroxyl radicals are involved in direct damage of important biomolecules. Potent radical scavengers such as vitamin C and indoles of the tryptophan family can avert the potential damage. Melatonin and its precursor 5-hydroxytryptophan (5-HTP) were compared with water-soluble vitamin C. Different scavenger concentrations were measured in a steady-state luminol chemiluminescence system (SLCL-system) with combined Fe(II) chloride (0.1 mm) and hydrogen peroxide (1.0 mm) as hydroxyl radical generators. 5-HTP showed highest hydroxyl radical scavenging effects with a 50% inhibition concentration (IC50) of 1.8 microm. For vitamin C an IC50 of 12.7 microm was measured, whereas melatonin in pure demineralized water was much less efficient (IC50=724 microm). A comparison between melatonin in aqueous solution and melatonin in ethanol solution revealed that melatonin was significantly more effective in pure demineralized water.