A sample processing method for immunoassay of whole blood tacrolimus.

Current sample processing (SP) methods for tacrolimus (FK506) immunoassays are mainly based on extraction of drug by organic solvent and divalent metal ions. Although these methods are effective for drug extraction and interference elimination, they suffer from drawbacks including inconvenience for operation, difficulties for automation and potential measurement bias. To overcome these limitations, this study describes a new SP reagent for blood cell lysis and protein denaturation. A TRFIA (time-resolved fluorescence immunoassay) was developed by using this SP reagent for whole blood FK506 quantification. Results show that blood samples could be turned into homogeneous solution after being treated by this SP reagent, and so could be directly applied to immunoassays without centrifugation. The analytical sensitivity of the FK506-TRFIA was 0.57 ng/mL, the within-run and between-run coefficient of variations (CVs) were both less than 10%. The FK506 values of 126 samples obtained by FK506-TRFIA correlated excellently with that obtained by ABBOTT FK506-CMIA (R2 = 0.982). Comparison studies also show that the FK506-TRFIA was highly resistant to endogenous interferences. These results suggest that the present SP method is a more promising chose for FK506 immunoassay, and in the meantime, its simplicity makes the whole-process immunoassay automation more feasible by obviating the necessary for centrifugation.

Flavonoids from Matteuccia struthiopteris and Their Anti-influenza Virus (H1N1) Activity.

Seven new flavonoid glycosides (1-7), matteflavosides A-G, together with 12 known flavonoids (8-19) were isolated from the rhizomes of Matteuccia struthiopteris (L.) Todar. Their structures were established via the analyses of extensive spectroscopic data. All compounds were evaluated for their anti-influenza virus (H1N1) activity using the neuraminidase inhibition assay. The results showed that compound 7 exhibited significant inhibitory activity against the H1N1 influenza virus neuraminidase with an EC50 value of 6.8 ± 1.1 µM and an SI value of 34.4, and compounds 8 and 17 showed moderate inhibitory activity.

Double-antigen sandwich time-resolved immunofluorometric assay for the detection of anti-hepatitis C virus total antibodies with improved specificity and sensitivity.

Current anti-hepatitis C virus (HCV) antibody screening immunoassays are routinely based on an indirect format. Although their use for anti-HCV antibody detection has achieved a very high specificity and sensitivity, false-positive results are still a problem especially among populations with a low prevalence of HCV infection. One strategy to obviate this problem is to adapt the assay from an indirect format to a double-antigen sandwich one to further improve its specificity. In this study, a double-antigen sandwich time-resolved immunofluorometric assay (DAS-TRIFMA) has been developed to detect total anti-HCV antibodies based on biotin-streptavidin interaction. For comparison, 1025 samples were analysed by the DAS-TRIFMA and three indirect anti-HCV antibody detection methods. For samples with discordant results, PCR-ELISA and Inno-LIA were employed as supplementary assays to analyse the presence of HCV antibodies. With regard to the 1025 clinical samples, the overall concordance between the DAS-TRIFMA and the three indirect methods was 99.41, 98.93 and 98.93 % for Ortho ELISA 3.0, WAT ELISA and I-TRIFMA, respectively. The specificity/sensitivity of the DAS-TRIFMA, Ortho HCV ELISA 3.0, WAT HCV ELISA and I-TRIFMA were 100/99.09, 99.34/98.18, 99.23/97.27 and 99.01 %/98.18 %, respectively. The DAS-TRIFMA was able to detect HCV antibodies at a concentration about 1/10 of that detectable by indirect methods. From the obtained results and their comparison, it is concluded that the DAS-TRIFMA is a more specific and reliable method for screening anti-HCV antibodies, and weakly positive S/Co values by the DAS-TRIFMA were more predictive of HCV infection than those by indirect methods.

A new europium beta-diketone chelate for ultrasensitive time-resolved fluorescence immunoassays.

4,4'-Bis(1",1",1"-trifluoro-2",4"-butanedione-6"-yl)-chlorosulfo-o-terphenyl (BTBCT) was synthesized by modifying the structure of the reported BHHCT. In comparison with the original BHHCT, the detection sensitivity of BTBCT-Eu chelate in aqueous solution was improved approximately 8 times by time-resolved fluorescence measurement. To construct sensitive TRFIAs with the use of BTBCT-Eu chelate as the fluorescent label, streptavidin-BSA conjugate was prepared by the maleimide-thiol method and labeled by BTBCT. The streptavidin-BSA conjugate and its BTBCT-labeled complex were affinity-purified using 2-iminobiotin-agarose as binding reagent. With streptavidin-BSA-BTBCT-Eu complex as signal generation reagent, a highly sensitive indirect serum hTSH TR-IFMA was developed. The low limit of detection (LLD) of the TSH TR-IFMA was 0.011 mIU/L with 10 microl of sample volume, corresponding to approximately 337,900 molecules per test. To evaluate the utility of BTBCT-Eu label in direct TRFIAs, a competitive serum T4 TRFIA was developed with T4-BSA-BTBCT-Eu complex as competing tracer. The measurements obtained by the present TSH TR-IFMA or T4 TRFIA correlated well with those obtained by commercial Wallac TSH DELFIA Ultra or T4 DELFIA, respectively. Primary results show that BTBCT can be employed as a powerful labeling material for constructing ultrasensitive TRFIAs.

Time-resolved immunofluorometry of serum hTSH with enhanced sensitivity.

Sensitive TSH immunoassays offer a clear advance in discriminating the TSH concentrations in serum between hyperthyroid and euthyroid individuals; they have been proposed as the best single screening test for thyroid disorders. We have developed a highly sensitive serum TSH TRFIA based on DELFIA technology. Three monoclonal antibodies (McAbs) directed against different epitopes of the TSH molecule were involved in this assay, of which, one McAb was used to coat clear microwells, and the other two were biotinylated' for signal generation after being bound by the europium labeled streptavidin. The europium label captured on the well surface was quantified by a routine dissociation-enhancement procedure. The fluorescence intensity was directly proportional to the serum hTSH concentration. The assay required two steps and could be completed within 5 h. The analytical sensitivity reached 0.002 mIU/L with a sample volume of 100 microL, the function sensitivity was 0.017 mIU/L. Measurements by the present method correlated well with that obtained by the ACS-180 chemi-luminescence immunoassay (CLIA). The discrimination of hyperthyroid patients from clinically euthyroid patients by the present method was much better than that by the routine IRMA.

Synthesis of a highly fluorescent beta-diketone-europium chelate and its utility in time-resolved fluoroimmunoassay of serum total thyroxine.

A new highly fluorescent beta-diketone-europium chelate was synthesized and employed as a tracer to develop a time-resolved fluoroimmunoassay (TRFIA) for detection of serum total thyroxine (T4). The tetradentate beta-diketone chelator, 1,10-bis(thiophene-2'-yl)-4,4,5,5,6,6,7,7-octafluorodecane-1,3,8,10-tetraone (BTOT), was structurally composed of two units of thenoyltrifluoroacetone (TTA) derivatives but expressed fluorescence that was greatly enhanced, as compared to the original TTA molecules, in the presence of excess amount of Eu3+. The luminescence properties of the europium chelate of BTOT werestudied in aqueous solution. Chlorosulfonylation of BTOT afforded 1, 10-bis(5'-chlorosulfo-thiophene-2'-yl)-4,4,5,5,6,6,7,7-octafluorodecane-1,3,8,10-tetraone (BCTOT), which could be coupled to proteins (i.e., streptavidin or the BSA-T4 conjugate) and used as a tracer for TRFIA. Although the BCTOT-Eu complex could be detected at a very low level (approximately 1.07 x 10(-12) mol/L) in buffered aqueous solution (50 mmoVLTris-HCl; pH, 8.0), the application of the chelate label in direct serum T4 TRFIA experienced a problem of matrix interference, which was probably caused by some unknown chelating components in the samples as a result of the fact that the fluorescence of the BCTOT-Eu chelate was prone to quenching or enhancement by some chelating reagents. To remove this problem, an indirect serum T4 TRFIA was proposed with the use of BCTOT-Eu-labeled streptavidin (SA) as signal generation reagent. The concentrations of T4 in 27 human serums were determined by indirect T4 TRFIA, and the assay results correlated well with those obtained by commercial Coming-CLIA (r = 0.955) and Wallac-DELFIA (r 0.965).

Sensitive time-resolved fluoroimmunoassay for simultaneous detection of serum thyroid-stimulating hormone and total thyroxin with Eu and Sm as labels.

Based on a novel cocoating strategy and dissociation enhancement lanthanide fluorescence immunoassay technique, a sensitive time-resolved fluoroimmunoassay (TRFIA) has been developed for simultaneous quantification of human serum thyroid-stimulating hormone (TSH) and thyroxin (T4) in a one-and-the-same assay procedure. The new cocoating strategy for preparing highly active surface anti-TSH and anti-T4 monoclonal antibodies (McAbs) was performed by a three-step protocol. Namely, anti-TSH McAb at high concentration (10 micro g/ml) and extensively biotinylated bovine serum albumin (BSA) at low concentration (0.5 micro g/ml) were coated on microwells by passive adsorption, then streptavidin was captured by the surface BSA-biotin, and finally biotinylated anti-T4 McAb was immobilized by the remnant binding sites of the bound streptavidin. In the present TSH/T4 TRFIA, both sandwich- and competitive-type configurations were involved, and Eu(3+) and Sm(3+) were used as labels for TSH and T4 detection, respectively. The method showed rapid kinetics; the equilibrium was reached within 30min at 37 degrees C due to the use of high concentrations of reaction reagents, rapid agitation, and small reaction volume. The lower limits of detection of the method were 0.028 mIU/L for TSH and 4.1 nmol/L for T4 with 20 micro L of sample volume. The assay ranges for TSH and T4 were 0.21-80.00 mIU/L and 20-300 nmol/L, respectively. The correlation between the TSH/T4 values obtained by the present TSH/T4 TRFIA and those obtained by commercial chemiluminescence immunoassay was satisfactory.

A study of commercial sex and HIV/STI-related risk factors among hospitality girls in entertainment establishments in Wuhan, China.

BACKGROUND: Commercial sex is illegal in China but there are still many hospitality girls (HGs) working at licenced entertainment establishments in many places in the country. Hospitality girls can be categorised as sex-HGs and non-sex-HGs. OBJECTIVE: To understand the proportion of sex-HGs and non-sex-HGs, the prevalence of HIV and sexually transmitted infections, and the high-risk behaviours among HGs. METHODS: A total of 257 HGs at 29 entertainment establishments (13 sauna/massage parlors, 10 dancing/karaoke bars and six barbershops) from seven urban districts in Wuhan were investigated and studied with a two-step sampling frame during November and December 1999. Information on sexual practices, drug abuse, condom use and other related factors were collected by anonymous interviewer-administered questionnaires. Anonymous laboratory testing was performed on 185 (72%) serum samples obtained for HIV-1 and HSV-2 by enzyme-linked immunosorbent assay. RESULTS: Of the 257 HGs, the mean age was 22.7 years (range 16-36 years); 147 (57.2%) stated they were sex-HGs, 15 (5.8%) were drug users, of whom 12 (80%) were injecting and 3 (20%) were inhaling. Sex-HGs was significantly correlated with drug abuse (P < 0.01, OR = 11.47). Among the 147 sex-HGs, 29 (19.7%) had sex with male clients more than seven times per week, 76 (51.7%) claimed to have used condoms consistently. The sero-prevalence survey of 185 HGs revealed that none tested HIV seropositive, and 40 (21.6%) were HSV-2 seropositive, which was positively correlated with sex-HGs (P < 0.01, OR = 3.13). CONCLUSIONS: Although the HIV epidemic in Wuhan has not yet reached a high level, HIV/AIDS prevention and control must be taken into account in entertainment establishments because of the existing high risk-taking behaviours and high STI incidence among HGs. It is feasible to carry out epidemiological investigations, which are concerned with sensitive topics such as sex, drug abuse, etc, among community-based female sex workers if designed and implemented prudently.