A promising CdSe@CdS-quantum dots-cysteine for the determination of trace IgE by solid substrate room temperature phosphorescence immunoassay.

The labelling reagent CdSe@CdS-QDs-Cys (QDs-Cys) with the grain diameter of 4.5 nm was synthesized by modifying CdSe@CdS quantum dots (QDs) with cysteine (Cys). At the same time, QDs-Cys-Ab(IgE), a phosphorescent quantum dot probe, was developed based on the labelling reaction between -COOH of QDs-Cys and -NH(2) of goat anti human IgE antibody (Ab(IgE)). This probe with excellent biocompatibility and high specificity could not only emit strong and stable room temperature phosphorescence (RTP), but also could carry out specific immunoassay (IA) with immunoglobulin E (IgE), causing the RTP of the system to sharply enhance. Thus, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of IgE was established. The limit of quantification (LOQ) of the method was 0.12 fg spot(-1), corresponding concentration was 3.0 × 10(-13) g mL(-1) and sampling quantity was 0.40 µL spot(-1). This highly selective, sensitive and accurate SSRTPIA has been applied to determine IgE in biological samples and diagnose diseases, and the results agreed well with those obtained by enzyme-link immunoassay (ELISA). Meanwhile, the mechanisms of QDs-Cys labelling Ab(IgE) and the determination of IgE by SSRTPIA were also discussed.

Preparation for nitrocellulose membrane-poly (vinyl alcohol)-ionic imprinting and its application to determine trace copper by room temperature phosphorimetry.

Nitrocellulose membrane-poly (vinyl alcohol)-ionic imprinting (NCM-PVA-I-I) was prepared using Cu2+ as template. The cavity in NCM-PVA-I-I matched Cu2+ very well and the selectivity was high. Cu2+ entered the cavity and then could form ionic association ([Cu2+] x [(Fin-)2]) with the anion of fluorescein (Fin-) outside the cavity by electrostatic effect. [Cu2+] x [(Fin-)2] could emit strong and stable room temperature phosphorescence on NCM-PVA-I-I. Its DeltaI(p) was proportional to the content of Cu2+. Based on the above facts, a new method for the determination of trace copper by solid substrate-room temperature phosphorimetry (NCM-PVA-I-I-SS-RTP, SS-RTP is the abbreviation of solid substrate-room temperature phosphorimetry) using NCM-PVA-I-I technique has been established. The linear range of this method was 2.00-144.00 fg Cu2+ spot(-1) (sample volume: 0.40 microL spot(-1), corresponding concentration: 5.00-360.00 pg mL(-1)), and the detection limit calculated by 3Sb/k was 0.43 fg Cu2+ spot(-1) (corresponding concentration: 1.1 x 10(-12) g mL(-1), n=11). Samples containing 2.00 and 144.00 fg Cu2+spot(-1) were measured, respectively, for seven times and R.S.D.s were 3.5% and 4.7%. NCM-PVA-I-I-SS-RTP could combine very well the characteristics of both the high sensitivity of SS-RTP and the high match and selectivity of NCM-PVA-I-I, and it was rapid, accurate, sensitive and with good repeatability. It has been successfully applied to determine trace copper in human hair and tea samples.

Solid substrate-room temperature phosphorescence method for the determination of trace Mn(II) based on oxidizing reaction of hydrogen peroxide using alpha,alpha'-bipyridine as sensitizer.

A new solid substrate-room temperature phosphorescence (SS-RTP) method for the determination of trace manganese (II) has been established. It bases on the fact that fullerol (R) emits strong and stable room temperature phosphorescence (RTP) on filter paper substrate. H2O2 can oxidize R to cause the SS-RTP quenching. But manganese (II) can obstruct H2O2 to oxidize R, and enhance the RTP of R. alpha,alpha'-Bipyridine (Bipy) can sensitize the RTP. After adding Bipy, the DeltaI(p) enhances 7 times than that without Bipy. Under the optimum conditions, the linear dynamic range of this method is 0.016-1.12 pg spot(-1) with a detection limit (L.D.) of 4.6 fg spot(-1) (m(Mn(2+) is the absolute mass of Mn(2+)), and the regression equation of working curve is DeltaI(p)=25.20 + 63.55 m(Mn(2+) (pg spot(-1)), n=6, r=0.9983. For 0.016 and 1.12 pg spot(-1) Mn(2+), RSDS are 4.3 and 4.8%, respectively (n=7). This method has been applied to the determination of trace manganese (II) in actual sample with high sensitivity and good selection. And the reaction mechanism of SS-RTP is discussed.

Determination of trace selenium by solid substrate-room temperature phosphorescence enhancing method based on potassium chlorate oxidizing phenyl hydrazine-1,2-dihydroxynaphthalene-3,6-disulfonic acid system.

A new method for the determination of trace selenium based on solid substrate-room temperature phosphorimetry (SS-RTP) has been established. This method was based on the fact that in HCl-KCl buffer solution, potassium chlorate could oxidize phenyl hydrazine to form chloridize diazo-ion after being heated at 100 degrees C for 20 min, and then the diazo-ion reacted with 1,2-dihydroxynaphthalene-3,6-disulfonic acid to form red azo-compound which could emit strong room temperature phosphorescence (RTP) signal on filter paper. Selenium could catalyze potassium chlorate oxidizing the reaction between phenyl hydrazine and 1,2-dihydroxynaphthalene-3,6-disulfonic acid, which caused the sharp enhancement of SS-RTP. Under the optimum condition, the relationship between the phosphorescence emission intensity (DeltaIp) and the content of selenium obeyed Beer's law when the concentration of selenium is within the range of 1.60-320 fg spot-1 (or 0.0040-0.80 ng ml-1 with a sample volume of 0.4 microl). The regression equation of working curve can be expressed as DeltaIp=13.12+0.4839CSe(IV) (fg spot-1) (n=6), with correlation coefficient r=0.9991 and a detection limit of 0.28 fg spot-1 (corresponding to a concentration range of 7.0x10(-13) g ml-1 Se(IV), n=11). After 11-fold measurement, R.S.D. were 2.8 and 3.5% for the samples containing 0.0040 and 0.80 ng ml-1 of Se(IV), respectively. This accurate and sensitive method with good repeatability has been successfully applied to the determination of trace selenium in Chinese wolfberry and egg yolk with satisfactory results. The mechanism of the enhancement of phosphorescence was also discussed.

Determination of alkaline phosphatase based on affinity adsorption solid-substrate room temperature phosphorimetry using rhodamine 6G-dibromoluciferin luminescent nanoparticle to label lectin and prediction of diseases.

In the presence of heavy atom perturber LiAc, the silicon dioxide nanoparticle containing rhodamine 6G (R) and dibromoluciferin (D) (R-D-SiO(2)) can emit strong and stable solid-substrate room temperature phosphorescence signal of R (lambda(ex)/lambda(em)=481/648 nm) and D (lambda(ex)/lambda(em)=457/622 nm) on the surface of acetyl cellulose membrane (ACM). R-D-SiO(2) is used to label triticum vulgare lectin (WGA). Then two types of affinity adsorption reactions, R-D-SiO(2)-WGA- alkaline phosphatase (ALP) (direct method) and WGA-ALP-WGA-R-D-SiO(2) (sandwich method), are carried out on ACM. The conditions and the analytical characteristics for the determination of ALP using affinity adsorption solid-substrate room temperature phosphorimetry (AA-SS-RTP) were studied. For a 0.40-microl drop of sample, results show that the detection limits of the sandwich method are 0.16 ag spot(-1)(457/622 nm) and 0.17 ag spot(-1)(481/648 nm), and the detection limits of the direct method are 0.41 ag spot(-1) (457/622 nm) and 0.44 ag spot(-1) (481/648 nm). The contents of ALP in human serum correlated well with those obtained by enzyme-linked immunoassay. This study shows that AA-SS-RTP whether by the sandwich method or the direct method, can combine very well the characteristics of both high sensitivity of SS-RTP and specificity of the immunoreaction. Simultaneously, whether the phosphorescence excitation/emission wavelength of either R or D in R-D-SiO(2) is chosen to determine ALP, this can promote the agility and widen the adaptability of AA-SS-RTP.