Detection of choline in biological fluids from patients on haemodialysis by an amperometric biosensor based on a novel anti-interference bilayer

A new and highly selective amperometric biosensor able to analyse choline in clinical samples from patients suffering from renal diseases and receiving repetitive haemodialysis treatment is described. The proposed biosensor is based on choline oxidase immobilized by co-crosslinking onto a novel anti-fouling and anti-interferent membrane. Between the several polymeric films electrosynthesized on a Pt electrode whose permselective behaviours were here investigated, those based on overoxidized polypyrrole/poly(o-aminophenol) bilayer revealed the most effective in rejecting common interferents usually present in biological fluids. The so realized biosensor showed notably analytical performances, displaying linear choline responses up to 100 μM, a sensitivity of 156 nA mM−1 mm−2 and a limit of detection, calculated at a signal-to-noise ratio equal to 3, of 1 μM; further, the within-a-day coefficients of variation for replicate (n = 3) were 2.7% and 1.2% at 100 μM and 10 μM choline levels, respectively. The remarkable performances and anti-interference behaviour allowed us the use of the proposed biosensor for the selective and fouling-free detection of choline in dialysate coming from patients on haemodialysis and even in their unpretreated human sera. Preliminary results gave choline levels in good agreement with the expected values.