Solvent and pH effects on fast and ultrasensitive 1,1′-oxalyldi(4-methyl)imidazole chemiluminescence

AIEgens-based fluorescent covalent organic framework in construction of chemiluminescence resonance energy transfer system for serum uric acid detection

A covalent organic framework (COF) with aggregation-induced emission (AIE) property was successfully synthesized through in situ marriage of a commonly used AIE molecule tetraphenylethylene (TPE) with Schiff base network (SNW-1) through a simple one-pot method. The TPE@SNW-1 was characterized with different techniques of Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and nitrogen adsorption/desorption experiments. The fluorescence of the TPE@SNW-1 strongly depends on the composition of tetrahydrofuran-water binary system. The AIE property of TPE@SNW-1 was directly supported with particle size distribution by dynamic light scattering technique. With the TPE@SNW-1 as an energy acceptor, a chemiluminescence resonance energy transfer (CRET) system was constructed with bis(2,4,6-trichlorophenyl) oxalate (TCPO)-hydrogen peroxide (H₂O₂) reaction as an energy donor. The chemiluminescence (CL) signal displays a good linear relationship with concentration of H₂O₂ in the 5.0-1000.0 μmol·L^-1 range, and a detection limit of 2.34 μmol L^-1. The system was further exploited to determine uric acid based on the fact that equal stoichiometric amount of H₂O₂ can be concurrently generated under the catalysis of uricase. The procedure exhibits a linear response to uric acid concentration in the range 10.0-150.0 μmol·L^-1 and a detection limit of 4.94 μmol·L^-1. The practicability of the method was demonstrated  in the determination of uric acid in human serum samples.

Chitosan-modified silver@ruthenium hybrid nanoparticles: evaluation of physico-chemical properties and bio-affinity with sialic acid

A hybrid nanoparticle system composed of silver, ruthenium and chitosan for selective recognition of sialic acid based on fluorescence quenching.

Development of 1,1'-oxalyldiimidazole chemiluminescent biosensor using the combination of graphene oxide and hairpin aptamer and its application

Highly sensitive biosensor with 1,1'-oxalyldiimidazole chemiluminescence (ODI-CL) detection was developed to rapidly quantify Vibrio (V) parahaemolyticus without time-consuming procedures such as multiple long-incubations and washings. When V. parahaemolyticus in Tris-HCl (pH 7) and hairpin DNA aptamer conjugated with TEX615 in DNA free deionized water were consecutively added in PBS buffer (pH 7.4) containing graphene oxides (GOs), V. parahaemolyticus and GOs bind competitively to hairpin DNA aptamer conjugated with TEX615 during 10 min of incubation at room temperature. Brightness of light immediately emitted with the addition of ODI-CL reagents (e.g., ODI, H2O2) after the incubation was dependent on the concentration of V. parahaemolyticus in a sample. The dynamic range of linear calibration curve for the quantification of V. parahaemolyticus in a sample was from 4375 to 70,000 cells/ml. The limit of detection (LOD = background + 3 × standard deviation, 2230 cells/ml) of the biosensor operated with good accuracy, precision, and recovery was lower than those of conventional assay methods such as time-consuming and expensive enzyme-linked immunosorbent assays.

Role of background observed in aptasensor with chemiluminescence detection

One-step chemiluminescent aptasensor was developed using chemically initiated electron exchange luminescence (CIEEL) between high-energy intermediate formed from 1,1'-oxalyldiimidazole chemiluminescence (ODI-CL) reaction and G-quadruplex (ochratoxin A (OTA)-bound aptamer conjugated with TEX615) generated. The sensitivity of chemiluminescent aptasensor, optimized with various variables (e.g., property of microfibers fabricated with 3,4,9,10-perylenetetracarboxylic dimide, determination of fluorescent dye labeled with aptamer, physical properties of buffer solution), was dependent on the background (concentration of high-energy intermediate) generated in ODI-CL reaction. The limit of detection (LOD=background+3×standard deviation, 0.5 nM) of ODI-CL aptasensor with lower background was lower than that (3.7 nM) with 20 times higher background. Also, the ratio of signal to background (S/B) of ODI-CL aptasensor with low background was about 5-fold higher than that with high background. The sensitivities of ODI-CL aptasensors, with low as well as high background, capable of accurately and precisely quantifying OTA within 10 min, were better than those of fluorescent aptasensors and as good as those of highly sensitive but time-consuming competitive enzyme-linked immune-sorbent assays (ELISAs) using expensive antibody produced with the sacrifice of small animals.

Fieldable flow injection analysis system with chemiluminescence detection capable of quantifying

We developed a highly sensitive biosensor for quantifying acetylcholine (ACh) using flow injection analysis system with 1,1'-oxalyldiimidazole chemiluminescence (ODI-CL) detection designed based on the principle of liquid core waveguide. ACh in Tris-HCl (pH 8.5) was incubated with the mixture of 1.0 U/ml acetylcholinesterase, 0.5 U/ml choline oxidase, 0.04 U/ml horseradish peroxidase, and 1.0 μM Amplex Red in PBS (pH 7.4) for 15 min at room temperature. The concentration of resorufin formed from the consecutive enzyme reactions was proportional to the concentration of ACh in analytical sample. The dynamic range of linear calibration curve (y = 12444x + 11617, R2 = 0.998) for the quantification of ACh using the biosensor with ODI CL detection was 0.7∼11.3 μM. The limit of detection (LOD = background noise + 3σ) of the biosensor was as low as 0.14 μM. Based on the results of recovery test and linearity study, finally, we confirmed that FIA system with ODI CL detection is accurate, precise, and reproducible.

Rapid monitoring of alkaline phosphatase in raw milk using chemiluminescence detection

A simple biosensor with 1,1'-oxalyldiimidazole chemiluminescence (ODI-CL) detection capable of rapidly quantifying and screening alkaline phosphatase (ALP) in raw and pasteurized milk was developed as an indicator for confirming whether commercial milk is properly pasteurized. Fluorescein was formed when standards containing 1.0% milk with different activities of ALP and samples containing 1.0% raw milk were incubated with fluorescein diphosphate (FDP) for 15 min at room temperature. The relative CL intensity of fluorescein measured with the addition of 80 mM H2O2 and ODI formed from the reaction of 2.0 μM bis(2,4,6-trichlorophenyl) oxalate and 10.0 μM 4-methyl imidazole in ethyl acetate was proportional to the concentration of ALP in milk. The range (39∼2500 mU/L) of linear calibration curve (R2 = 0.998) for the quantification of ALP in milk using ODI-CL detection was wider than those using currently applied fluorescence and 1,2-dioxetane CL detections. Also, the limit of detection (3.7 mU/L) determined using the former detection, which has good precision, was lower than those reported using the latter detections. In conclusion, the cost-effective and highly sensitive biosensor with ODI-CL detection can be applied to monitor whether milk is pasteurized according to acceptable ALP activities threshold level (350 mU/L) for public safety newly adopted by US and EU and the internal investigation level (100 mU/L) proposed by EU.