Yun-Xiang Ci

Thermally Reversible Hydrogel Based Fluoroimmunoassay of Methyltestosterone

ABSTRACT A novel immunoassay of methyltestosterone (MT) in serum is developed. We synthesized the antigen of MT (AgMT) by covalently bonding it to BSA and raised its antibody (AbMT) from rabbit. AbMT was conjugated to poly-N-isopropylacrylamide (p-NIPAAm) to form AbMT bound thermally reversible hydrogel (p-NIPAAm-AbMT). A competitive immunoassay method based on the competition of fluorescein isothiocyanate (FITC) labeled MT antigen (FITC-AgMT) and MT with limited amounts of p-NIPAAm-AbMT was established. The separation in the assay process was achieved by precipitation of the immuno-complex above its critical solution temperature. The detection limit of MT is 50 ng/ml. The recoveries of MT in human serum are above 93%.

RICIN DETERMINATION BY TEMPERATURE CONTROLLED PHASE-SEPARATION IMMUNOASSAY

A novel immunoassay of ricin in serum was developed. The antigen of ricin (Agricin)was labeled with isothiocyno-fluorecein (FITC). The antibody of Agricin (Abricin)was conjugated to poly-N-isopropylacrylamide (PNIP) to form Abricin bound thermally reversible hydrogel PNIP-Abricin. A competitive immunoassay method based on the competition of FITC-Agricin and free ricin with limited amount of PNIP-Abricin was established. The separation in the assay process was achieved by precipitation of the immuno-complex above its lower critical solution temperature (LCST). The fluorescence intensity was determined and the standard curve was obtained. The linear range was 30–200 ng/ml. The detection limit was 30 ng/ ml. The recoveries of ricin from serum were satisfactory.

Determination of platinum(IV) with silver(I) and 4,4′-Bis(diethylamino)thiobenzophenone

Abstract A supersensitive color reaction of platinum(IV) with silver(I) and 4,4′-Bis(diethylamino)thiobenzophenone in the presence of ascorbic acid and Triton X-100 has been investigated. The complexation is complete instantaneously after making up to final volume at room temperature. The orange-red complex exhibits an absorption maximum at 500 nm with a molar absorptivity of 1.3 × 107 (in the presence of 30 μg of Ag(I)) and 1.1 × 108 liters · mol−1 · cm−1 (in the presence of 60 μg of Ag(I)). Beers law is obeyed over the concentration range 0–1.6 and 2–16 ng/ml of Pt(IV) in the presence of 30 and 60 μg of Ag(I), respectively. The optimal conditions of the color reaction and interference of diverse ions are reported. The proposed method has been used successfully for the determination of platinum in synthetic samples.

Selective Determination of Cytosine Based on Its Fluorogenic Reaction with Triethylamine/Chloroacetonitrile

Abstract A sensitive fluorometric method is described For selective determination of cytosine in nucleobases. The method is based on chemical derivatization of cytosine by triethylamine/chloroacetonitrile. The effects of solvent, reaction temperature, reaction time and concentration of reagents on the efficiency of the reaction were studied. A good linear relationship between fluorescence intensities and cytosine concentrations in the range of 2.0–800 ng/mt was observed. The detection limit for cytosine is 0.6 ng/ml (S/N=3). The relative standard deviations (7 replicates) for measurements of 50 and 500 ng/ml cytosine were 2.1 and 2.5%, respectively.