[Methodological study on magnetic affinity immunoassay for detecting chloramphenicol].

AIM: To establish a sensitive immunoassay for detection chloramphenicol using magnetic beads as solid phase. METHODS: This assay employs the competitive inhibition, the FITC conjugated with anti-chloramphenicol monoclonal antibodies and the alkaline phosphatase conjugated with chloramphenicol respectively. Magnetic beads were coupled with sheep anti-FITC antibodies as solid phase. And phenolphthalein monophosphate was used as substrate to set up MEIA for detection chloramphenicol. RESULTS: MEIA for detection chloramphenicol was Established, the reaction time is 40 minutes, the sensitivity is 0.03 microg/L, the liner range is 0.1-8.1 microg/L, the intra and inter coefficient variation (CV) was 3.9%-5.3% and 4.8%-8.1% respectively and the recovery is 97%-101.5%. Comparing with national standard method of liquid chromatography-mass spectrometry, the Correlation coefficient of test results is 0.9817 (r=0.9817). CONCLUSION: The chloramphenicol MEIA method is sensitive, accurate, and fast, it provides a new method of immunoassay for the monitoring of chloramphenicol residues in food.

[Application of magnetic particle antibody immunoassay in detection of anti-Schistosoma japonicum egg antibody].

OBJECTIVE: To establish a magnetic particle antibody immunoassay (MPAIA) for the detection of specific antibody in sera of schistosomiasis patients. METHODS: Fluorescein isothiocyanate (FITC) was used to label Schistosoma japonicum soluble egg antigen (Sj-SEA). Anti-human IgG coated with alkaline phosphatase (ALP) as enzyme-labeled second antibody, and magnetic beads were coupled with sheep anti-FITC antibody as solid phase. Phenolphthale in monophosphate was used as substrate to set up MPAIA for the detection. Serum samples from cases with schistosomiasis or other helminth infections were tested. RESULTS: The positive rate of MPAIA was 96.7% (116/120) with the sera of S. japonicum-infected cases. No cross reaction was observed with sera of trichinellosis, paragonimiasis or cysticercosis cases. The positive titer with reference sample was 1: 1,600. The precision was lower than 10%. The MPAIA tips can be stored at 4 degrees C for 12 months. CONCLUSION: MPAIA shows a high sensitivity, proper specificity and long-term validity for schistosomiasis detection.

[Establishment of the magnetic separation enzyme immunofluorescence method for detecting insulin].

AIM: To establish a convenient and sensitive magnetic separation enzyme immunofluorescence (MEIF) method for detecting human insulin. METHODS: Two monoclonal antibodies (mAbs) were conjugated with FITC and alkaline phosphatase (AP) respectively, which were incorporated magnetic solid phase separation. Magnetic beads were coupled with sheep anti-FITC antibody as solid phase and 4-Methylumbelliferyl-phosphoric acid (4-MUP) was used as substrate to set up MElF for detecting insulin. RESULTS: The sensitivity of this assay was 2.0 microIu/mL, the linear range was from 0 microIu/mL to 188.52 microIu/mL, and the intra-assay variation and inter-assay variation were 4.3%-5.2% and 2.6%-9.5%, respectively. The recovery rate of dilution was 92.6%-117% and the recovery rate of accession was 106%-121%.The result of the assay correlated well with that of magnetic enzyme chemiluminescence immunoassay system. CONCLUSION: The MEIF for detecting insulin is low at cost, sensitive, specific and stable, which can be widely used in clinical immune detection.

[Establishment of chemiluminescence immunoassay for detecting Staphylococcal enterotoxin B and C1].

AIM: To establish chemiluminescence immunoassay (CLIA) for detecting staphylococcal enterotoxin B (SEB) and C1 (SEC1) and compare its sensitivity and stability with ELISA. METHODS: The anti-SEB and SEC1 monoclonal antibodies (mAb) were purified by Q Sepharose Fast Flow chromatographic column. The alkaline phosphatase (AP) conjugated mAbs FMMU-SEB.D6 and FMMU-SEC1.C4 were used as detecting antibodies and the FMMU-SEB.B4 and FMMU-SEC1.G8 mAbs were used as coating antibodies in both methods. Phenolphthalein monophosphate (PMP) and lumigen APS-5 were employed as substrates for AP in ELISA and CLIA, respectively. The light was detected and measured by the GENios analyzer (TECAN Group Ltd.). The sensitivities and detect ranges of CLIA and ELISA methods were compared. RESULTS: Compared with ELISA, CLIA was more sensitive (0.1 ng/mL vs 0.39 ng/mL) and timesaving. Furthermore, the liner range of CLIA was broader than that of ELISA (0.78-50 ng/mL vs 3.125-50 ng/mL). CONCLUSION: CLIA for detecting SEB and SEC1 are established successfully which may be useful in food monitoring, epidemiology survey and detecting SE contaminated samples in environment.

[Methodological study on magnetic enzymic immunoassay for detecting free hCGbeta subunit].

AIM: To establish a novel magnetic enzyme immunoassay (MEIA) for detecting human choriogonadotropin free beta subunit (hCGbeta). METHODS: Two monoclonal antibodies (mAb) were used for conjugating with FITC and with alkaline phosphatase(AP) respectively, which incorporated magnetic solid phase separation. Magnetic beads were coupled with sheep anti-FITC antibody as solid phase, and phenolphthalein monophosphate was used as substrate to set up MEIA for detecting hCGbeta. RESULTS: The sensitivity of hCGbeta MEIA kit reached 0.1 IU/L. The intraassay variation and inter-assay variation was 8.5% and 14% respectively, with the average recovery rate of dilution of 92.5%. The kit showed no cross reactivity to LH, TSH and FSH, while a cross reactivity of 1.2% to intact hCG at concentration of 1000 IU/L. The time of efficacy of hCGbeta MEIA kit was longer than 14 months. CONCLUSION: hCGbeta MEIA kit is better than hCGbeta radio immunoassay and ELISA kit, which can provide a high-qualitative and cheap hCGbeta kit for market.