Non-ceruloplasmin-bound copper and copper speciation in serum with extraction using functionalized dendritic silica spheres followed by ICP-MS detection

Abstract

The quantification of non-ceruloplasmin-bound copper (NCBC) and total copper in biological fluids is highly required for understanding the correlation of copper with various physiological processes and diseases. In the present work, we developed dendritic spherical silica particles functionalized with EDTA, shortly as DMSPs-EDTA, from the hydrolysis of tetraethyl orthosilicate with the aid of structure-directing agents and subsequent modification of EDTA. DMSPs-EDTA serves as adsorbent with abundant binding sites to facilitate efficient extraction of NCBC. The retained NCBC on DMSPs-EDTA may be readily recovered by stripping with HNO3 (2 mol L−1). By hyphenating with ICP-MS detection, it provides a limit of detection of 1.3 pmol for NCBC. The degradation of ceruloplasmin with 200 mmol L−1 H2O2 releases the bound copper as NCBC to distribute among other ligands, which may be efficiently retained by the adsorbent and facilitate the detection of total copper. The linear ranges of 0.21–10 μmol L−1 and 0.42–30 μmol L−1 were derived for the detection of NCBC and total copper. The recovery rates for spiked NCBC or total copper in serum were derived to be 97–108% and 94–102%, respectively. The analysis of serum for a healthy subject resulted in 1.8 μmol L−1 NCBC and 9.5 μmol L−1 total copper. In addition, the proportions of 8.5–12% for NCBC were derived from the serum of healthy adults, while those for the patients with lung, hepatocellular and esophageal carcinoma were found to be 10–12%, illustrating no obvious difference against the normal group.