LA-ICP-MS with microarray chip sampling to determine holoceruloplasmin in serum

An analytical method was developed to determine holoceruloplasmin (holo-CP) concentration in serum using laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). Since each holo-CP in serum contains six Cu ions, the concentration was estimated quantitatively by determining the Cu concentration. For small sample consumption, polydimethylsiloxane (PDMS) microarray chips with 150 mu m diameter pillars were manufactured. The surface of each pillar was immobilized by a ceruloplasmin (CP) antibody (IgG) for an antigen-antibody reaction to afford high selectivity for the sampling of total CP in the serum matrix. A calibration curve with a linear regression coefficient of 0.992 was obtained by standard addition methods. For demonstration, 126 pL of human serum was loaded on each pillar of the microarray chips and analyzed by LA-ICP-MS in single-shot mode. The determined concentration of holo-CP was compared with that of the total CP estimated by competitive enzyme linked immunosorbent assay (ELISA), from which the concentration of apoceruloplasmin (apo-CP) was deduced. In conclusion, this analytical method for determining holo-CP concentration with high selectivity and small sample volume can be used in the confirmative diagnosis of diseases related to copper deficiency in clinical samples.