Soluble highly coloured phenylboronic acids and their use in glycohemoglobin quantification

Water soluble dye-phenylboronic acid conjugates (dye-PBAs) possessing strong absorption of visible light are introduced as new reagents for the determination of glycohemoglobin. Their functionality and prospective use are demonstrated in a semi-homogenous glycohemoglobin assay. The assay is based on cis-diol esterification of dye-PBA to glycohemoglobin followed by selective precipitation of hemoglobin from solution, co-precipitating bound dye-PBA. Quantification of the molar "dye-PBA/Hb"-ratio in redissolved precipitates using either absorption or fluorescence spectroscopy, reflects the glycation level of the blood samples used. Future development of the assay principle is illustrated in a filter based assay, collecting the precipitated hemoglobin on a filter followed by reflectometric readings directly on the precipitate. The significance of this work lies first, in the demonstration of a new principle for the determination of glycohemoglobin, and second, as an illustration of the prospective use of water soluble, signal-forming non-immobilised boronic acids in the determination of cis-diol containing analytes.