A novel simple optical sensor based on fast protein liquid chromatograph (FPLC) was developed and tested for monitoring end stage renal disease (ESRD) patients on continuous ambulatory peritoneal dialysis (CAPD). The device provides direct determination of proteins and lower molecular weight metabolites in effluent peritoneal dialysate using low-cost PD-10 columns and photometric detection at the wavelengths 285 nm or 260 nm with deep ultraviolet light-emitting diodes (UV LED).
The sensor was calibrated with bovine serum albumin (BSA), adenosine triphosphate (ATP), inosine monophosphate (IMP), inosine (Ino), and hypoxanthine (Hx) standard solutions. Chromatograms of effluent peritoneal dialysate taken from 28 ESRD patients were processed and approximated by a set of split-Gaussian functions; UV absorption spectra of the samples were recorded in parallel.
All chromatograms show three overlapping peaks: the first one represents proteins; the other two peaks probably correspond to mid- and low molecular weight metabolites. Strong correlation (R2 = 0,947) was reveled between the area of the first peak and total protein (TP) concentration determined by a standard biochemical assay, this makes possible estimation of peritoneal protein loss with a reasonable precision less than 15%.
The elution time of the second peak was close the elution time of IMP (M=348 Da). The area of the second peak correlated relatively weakly with dialysate optical density at a wavelength 355-365 nm, associated with the UV absorption of advanced glycation end (AGE) products, but there is still not enough evidence to attribute confidently this peak to AGE. The third peak showed the elution time close to Hx (M=136 Da), the area of this peak correlated with the optical density of the eluate at a wavelength 255-265 nm, associated with the UV absorption of purines and pyrimidines.
Thus, we demonstrated the possibility of estimation of proteins and lower molecular weight metabolites in effluent peritoneal dialysate with the compact and affordable chromatographic optical sensor.