Visible fluorescence of biological fluids as a renal failure marker: New integrative approach

Abstract

Solid phases of visible°uorescence substance (VFS) of biological°uids (blood, urine, hemodialysate) which was proposed earlier as a morbidity and mortality marker by renal failure and diabetes were investigated in-depth by the methods of electron and confocal microscopy, optical spectroscopy and matrix assisted laser desorption-ionization (MALDI) mass spectroscopy. It is shown that dry VFS exists predominantly in the form of carbon-oxygen-nitrogen (N % 8:7 wt. %) nanoparticles (NPs) (5 d 100 nm). For the¯rst time the existence of the threshold energy E g % 2:15 eV for excitation of VFS was observed experimentally and con¯rmed by semi-empirical calculations of the bathochromic shift. A good accordance with the earlier autonomous theoretical calculations was achieved. Thus, the long wavelength limit (575 nm) of the spectral range where the VFS can be used as a°uorescent marker was reliably determined. A pilot MALDI comparative study of graphene oxide (GO) and urine VFS was carried out. Six kinds of nitrogenfree particles (412 M 456 Da) were observed in each substance and possible computer models of those have been composed. It is established that along with nitrogen-containing advanced glycation end products (AGEs) also nitrogen-free carbon-oxygen-hydrogen particles (probably toxic) with the composition and structure related to GO can exist in bio°uids. Both types of particles should be taken into account in search for the reasons of high mortality among end stage renal disease patients.