Detection of metallothionein as a melanoma marker by LA-ICP-MS combined with sample pretreatment by using magnetic particles coated with an imprinted polymeric layer

Effective detection and sensitive quantification of disease markers enable a better understanding of processes leading to disease development. Therefore, we present an approach that combines the excellent selective recognition capabilities of molecularly imprinted polymers (MIPs) and sensitive elemental detection using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Dopamine was used as a functional monomer, and metallothionein (MT), a metal-containing protein (Zn and Cd), was the targeted tumor marker. Iron oxide magnetic particles were exploited as a carrier of the polymeric layer. Due to the agglomeration of the particles in the presence of an external magnet, the prepared molecularly imprinted polymers (Mag-MIPs(MT)) were capable of isolating MT molecules from a tissue sample. A sandwich immunoassay with antibodies labeled by using silver nanoparticles was used to confirm the binding of MT to Mag-MIPs(MT). The calculated efficiency of isolation from a standard MT solution (73.5 & mu;M) was 63.3% (46.5 & mu;M). Casein was used to verify the selectivity of the prepared Mag-MIPs. The prepared particles were used for sensitive quantification of MT in melanoma and healthy skin of the melanoma-bearing Libechov minipig (MeLiM), which confirms that this method is applicable for the investigation of the tumor microenvironment. We found a significantly higher content of Zn in tumor tissue than in healthy skin.