273. The development of an immunoassay to measure progestogen using printed biosensors, and its application to the assessment of ovarian function in the Numbat (Myrmecobius fasciatus)

Abstract

A biosensor system using screen printed sensors was developed to measure progesterone as an index of ovarian function, and compared with a standard enzymeimmunoassay (EIA). The sensors were coated with a monoclonal progesterone antibody which cross-reacts with a wide range of progestogens, and incubated in a mixture of sample/standard and progesterone-3-CMO-horseradish peroxidise (Prog/HRP). The endpoint was the change in potential read following the addition of sodium perborate. The assay was optimised in terms of the Prog/HRP concentration, the antibody dilution and incubation times. It was then used to measure progestogen in the urine of five female Numbats (Myrmecobius fasciata). Results were available using the sensors within 20 min compared with the standard EIA protocol of 2 h. The serial dilution of a urine sample taken at the diestrus stage showed parallelism with the serially diluted standard. There was a significant rise in progesterone (mean ± sem) after mating compared with that seen before for both the EIA (1.31 ± 0.20 to 3.70 ± 0.13 ng/mL) and the sensor (1.83 ± 0.33 to 4.02 ± 0.61 ng/mL), and there were no significant differences between the sensor and EIA results at either stage (all P > 0.1). A comparison of the values obtained with the sensors to those obtained with the conventional EIA showed a significant correlation for each of the animals (r = 0.82 to 0.99). It is concluded that the biosensor system is a viable alternative to conventional EIA, and provides the advantage of (a) a shorter assay time and (b) greater potential for use in the field.