Preparation and evaluation of recombinant human ferritin light chain for quality control materials

Abstract

Objective To construct a prokaryotic expression system of human ferritin L which could be overexpressed in E.coli, and then prepare quality control materials of rFL and evaluate the homogeneity, stability, precision and application value of the rFL.Methods RT-PCR was used to clone ferritin L gene with total RNA from peripheral blood.Ferritin L gene was inserted into plasmid pGM-T to construct subclone plasmid pGM-T/ferritin L, which was identified by sequencing.The recombinant plasmid pET-30a/ferritin L was transformed into E.coli BL21 (DE3) and efficiently expressed under IPTG induction.rFL was identified by SDS-PAGE, and its antigenicity was examined by WB.The concentration of rFL was measured by ACCESS immunoassay system.Fifteen control samples were randomly selected using random number table.The homogeneity and stability of rFL were evaluated by one-way analysis of variance (ANOVA) and a linear regression model, respectively.The uncertainties of homogeneity, stability and the precision were evaluated.Results A prokaryotic expression system of ferritin L was successfully constructed.Sequence analysis showed that the ferritin L gene inserted was identical with the one from GenBank(NM_000146.3).The PCR products were 527 bp long, in complete agreement with length of ferritin L gene.The molecular weight of rFL highly expressed in E.coli induced by IPTG was 19 000 Da.The WB analysis indicated that this rFL protein had good antigenicity.The concentration of rFL(1 000 times dilution) measured by ACCESS immunoassay system was (1115.84±38.38) ng/ml.Homogeneity evaluation of low-concentration QC sample and high-concentration QC sample of rFL showed that there were no statistical significances in the within-groups and between-groups (for high-concentration F=2.336, P>0.05 and for low-concentration F=0.730, P>0.05).A linear regression based on the stability test indicated that there was no statistically significant trend of instability in five and a half months (F=1.755, P>0.05). Precision analysis showed the within-run CV, the between-run CV, the between-day CV and the total CV of high-concentration QC sample were 2.06%, 2.12%, 0% and 2.96% respectively; the within-run CV, the between-run CV, the between-day CV and the total CV of low-concentration QC sample 2.03%, 2.08%, 0% and 2.90%, respectively.Conclusion This rFL for quality control materials with independent intellectual property rights could meet the clinical requirement of homogeneity, stability and precision, and could provide raw materials for preparation of mixed ferritin for quality control. Key words: Ferritins; Escherichia coli; Recombination,genetic; Gene expression; Quality control