RESUMEN
17ß-estradiol is abused in the food industry. Excess 17ß-estradiol can disturb the endocrine system or cause many diseases including obesity, diabetes, cardiac-cerebral vascular disease, and cancers in the human body. A "turn-on" fluorescence resonance energy transfer (FRET) aptasensor based on carbon dots (CDs) and gold nanoparticles (AuNPs) was developed for the detection of 17ß-estradiol. A thiol-modified oligonucleotide was conjugated to AuNPs and amino modified oligonucleotide was linked to CDs. The 17ß-estradiol aptamer was hybridized with the two oligonucleotides, shortening the distance between CDs and AuNPs. With 360 nm UV light excitation, FRET occurred between CDs and AuNPs. The system was "turn-off". When 17ß-estradiol was detected, the aptamer specifically bound to 17ß-estradiol, and the FRET system was destroyed, leading to the "turn-on" phenomenon. The fluorescence intensity recovery was detected in the concentration range of 400 pM to 5.5 µM. The limit of detection (LOD) was 245 pM. The FRET aptasensor demonstrated good selectivity for 17ß-estradiol detection. Reasonable spiked recoveries were obtained in sea salt samples. It showed the potential for estrogen detection in food safety and environmental applications.
RESUMEN
8-hydroxy-2'-deoxyguanosine (8-OHdG) is a sensitive and stable biomarker for evaluating DNA oxidative damage. A rapid and sensitive colloidal gold immunochromatographic strip was developed for 8-OHdG detection by a competitive method. The sample pad (glass cellulose film), bonding pad (glass cellulose film), nitrocellulose film and absorbent pad were pasted on the polyvinyl chloride (PVC) base plate to construct the test strip. Colloidal gold (AuNPs) was prepared by the reduction of chloroauric acid with sodium citrate. 8-OHdG antibody (Ab) was coated on the outer layer of AuNPs to form Ab@AuNPs as a probe. Bovine serum albumin (BSA) and 8-OHdG were conjugated with carbodiimide hydrochloride to prepare an artificial antigen, which was used as the coating antigen of detection line. Goat anti mouse polyclonal antibody IgG was used as the coating antibody of control line. The experimental parameters were optimized including the type of nitrocellulose membrane, the formula of loading solution, and the spraying amount of gold labeled antibody. The results showed that the appropriate nitrocellulose membrane was CN 95. The optimal loading solution included BSA (1%), Tween-20 (3%), sucrose (3%) and NaCl (0.9%). The optimal spraying amount of gold labeled antibody was 4 µL. 8-OHdG can be detected by the strip under visible light, and the level of 8-OHdG in urine can be preliminarily determined by comparing the color intensity of T line and C line. The 8-OHdG concentration in urine was further calculated by the gray value of T line and the threshold of detection was 2.55 µg/L. This colloidal gold immunochromatographic strip is simple, rapid and specific for detecting 8-OHdG in human urine to preliminarily evaluate the human status.
