Alginate-based magnetic nanosorbent immobilized with aptamer for selective and high adsorption of Hg2+ in water samples.

Alginate-coated magnetic nanocluster (MNC) immobilized with Hg2+-specific aptamer was synthesized to obtain the nanosorbent with high adsorption capacity and high selectivity for trace analysis of inorganic mercury (Hg2+) in water samples. Magnetite nanoparticle was first synthesized by a co-precipitation of iron precursors in the presence of alginate to obtain alginate-coated MNC, followed by immobilization with avidin. Hg2+-Specific DNA aptamer labeled with biotin was then conjugated on the MNC surface via specific avidin-biotin interaction to form aptamer-immobilized MNC. Coating the MNC with alginate can improve its water dispersibility and also increase its adsorption capacity toward Hg2+ (350 mg/g). It exhibited high selectivity through thymine-Hg2+-thymine (T-Hg2+-T) interaction with high tolerance to other foreign ions. This nanosorbent showed linearity over the Hg2+ concentration range of 0.2-10 µg/L with a correlation coefficient of 0.9977, limit of detection of 0.46 µg/L, and enrichment factor of 13. Moreover, it also showed a potential for detection of Hg2+ in drinking and tap water samples with satisfactory recoveries.

Poly(acrylic acid)-grafted magnetite nanoparticle conjugated with pyrrolidinyl peptide nucleic acid for specific adsorption with real DNA.

Magnetite nanoparticle conjugated with pyrrolidinyl peptide nucleic acid (MNP@PNA) was synthesized for use as both a magnetic nano-support and a probe for specific adsorption with complementary deoxyribonucleic acid (DNA). MNP@PNA with the size ranging between 120 and 170 nm in diameter was prepared via a free radical polymerization of acrylic acid in the presence of acrylamide-grafted MNP to obtain negatively charged magnetic nanoclusters, followed by ionic adsorption with PNA. According to fluorescence spectrophotometry and gel electrophoresis, this MNP@PNA can differentiate between fully matched, single-base mismatched and fully mismatched synthetic DNAs tagged with different fluorophores. UV-vis spectrophotometry and gel electrophoresis indicated that MNP@PNA can be used for specific adsorption with real DNA (zein gene of maize) having complementary sequence with the PNA probe. This novel anionic MNP conjugated with the PNA probe might be potentially applicable for use as a magnetic support for DNA base discrimination and might be a promising tool for testing genetic modification.