Non-competitive time-resolved immunofluorometric assays for determination of human insulin-like growth factor I and II.

Abstract

We present sensitive non-competitive time-resolved immunofluorometric assays (TR-IFMAs) for IGF-I and IGF-II based on monoclonal antibodies. Assays were performed in microtest-plate wells: the first antibodies were immobilized on the solid matrix, the second labelled with the chelate derivative of Europium (Eu3+). The obtained specificities and sensitivities were high: IGF-I and IGF-II cross-reactivity in heterologous assay was below 0.0002%. The detection limits were 0.0025 micrograms/l and 0.010 micrograms/l for the IGF-I and IGF-II assay, respectively. The operating range included upwards: 2.5 micrograms/l (IGF-I) and 10.0 micrograms/l (IGF-II). This implies that all clinically relevant serum concentrations could be measured in one final dilution (1:1066 for IGF-I and 1:2132 for IGF-II) after acid ethanol extraction. The high sample dilution with buffer made further neutralization or evaporation of serum acid ethanol extracts unnecessary. Interassay variation of the assays was below 10%.