Fluorescence and chemiluminescence enzyme immunoassays of 17 alpha-hydroxyprogesterone in dried blood spotted on filter paper

Fluorescence imaging of the activity of glucose oxidase using a hydrogen-peroxide-sensitive europium probe

A method for optical imaging of the activity of glucose oxidase (GOx) using a fluorescent europium(III) tetracycline probe for hydrogen peroxide is presented. A decay time in the microsecond range and the large Stokes shift of 210 nm of the probe facilitate intensity-based, time-resolved, and decay-time-based imaging of glucose oxidase. Four methods for imaging the activity of GOx were compared, and rapid lifetime determination imaging was found to be the best in giving a linear range from 0.32 to 2.7 m Unit/mL. The detection limit is 0.32 m Unit/mL (1.7 ng mL(-1)) which is similar to that of the time-resolved (gated) imaging using a microtiterplate reader. Fluorescent imaging of the activity of GOx is considered to be a useful tool for GOx-based immunoassays with potential for high-throughput screening, immobilization studies, and biosensor array technologies.

Comparison of three methods for 17 alpha-hydroxyprogesterone

We compared the performance of three 17 alpha-hydroxyprogesterone kits: the double antibody method, the coated tube method (ACTIVE), both from Diagnostic Systems Laboratories, Inc. (DSL) and the coated tube method (COAT-A-COUNT) from Diagnostic Products Corporation (DPC). The assay performance of the two DSL kits was very similar in terms of sensitivity, intra- and inter-assay precision, linearity of dilution, recovery, and specificity. We also analyzed 190 samples for 17 alpha-hydroxyprogesterone values using the above three kits. Twenty-three subjects were from prepubertal population (ages 1 month-13 years), thirty subjects were normal adult males (ages 20-53 years) and the remaining subjects were females in different phase of menstrual cycle (n = 40), on oral contraceptives (n = 20), post-menopausal (n = 17), or pregnant women in their first, second, or third trimester (n = 60). In addition to these 60 pregnancy samples, we analyzed serial samples from 3 pregnancies. 17 alpha-OHP levels paralleled the progesterone levels in all three kits. Although there was reasonable correlation between the DPC and the two DSL kits, the 17 alpha-OHP values were found to be significantly higher with DPC kit during the 2nd and 3rd trimester of pregnancy indicating probable interference in the DPC assay by some structurally related steroids present during pregnancy. The DSL assays may be particularly well suited for measuring 17 alpha-OHP levels during pregnancy.

Chemiluminescence and immunoassays

The principles of chemiluminescence and the application of chemiluminescent labels and substrates in immunoassays are reviewed. Various immunoassay formats and all known classes of chemiluminescent molecules, including 1,2-dioxetanes, luminol and derivatives, acridinium esters, oxalate esters and firefly luciferins are described as well as the many sensitizers and fluorescent enhancers. Recent promising developments are discussed.

Immunoaffinity chromatography and a biotin-streptavidin amplified enzymeimmunoassay for sensitive and specific estimation of estradiol-17 beta

A sensitive test system has been developed for estimation of estradiol-17 beta (E2) in bovine plasma. Plasma extracts are first purified by a selective immunoaffinity chromatography (IAC) using an antibody raised against estradiol-6-carboxymethyloxime-bovine serum albumin and immobilized to Sepharose. The eluate was analysed by a competitive enzyme immunoassay (EIA) on microtitration plates. For the assay the wells of microtitration plates were coated with affinity purified sheep IgG (antirabbit IgG) that binds the hormone specific antibody raised in rabbits against estradiol-17-hemisuccinate-bovine serum albumin. E2 is estimated by displacement of biocytinyl-E2, that was produced by ligation of estradiol-17 beta, D-glucuronic acid and biocytin. Bound biocytinyl-E2 is detected after binding of streptavidin-peroxidase and colour production by the enzyme. A very high amplification was possible with this technique and the absolute detection limit amounted to approximately 120 fg/well at 94% relative binding. By combination of IAC and EIA the following levels of E2 were found in bovine plasma: male or female calves less than 2.7 pg/ml, cycling cow 0.5-7 pg/ml, cow during the last month of pregnancy 9-310 pg/ml, mature bull 5-30 pg/ml. However, up to 1110 pg E2/ml were found in plasma of a calf after treatment with an illicit hormone preparation used for growth promotion; after 21 days levels declined to 6 pg/ml which is hardly different from controls. In conclusion, the IAC/EIA can be used for sensitive estimation of estradiol-17 beta in plasma from all type of cattle and for control of improper use of E2 after commitment of a threshold level.