Multifunctional hydroxyapatite nanoparticle-based affinity adsorbent with sensing and fluorescence imaging capacity

Abstract

Nickel hydroxide/hydroxyapatite (Ni(OH)₂/HAP) nanoparticles (NPs) coated with rhodamine B hydrazide (RBH) were successfully synthesized in three steps. First, Ni(OH)₂/HAP-COOH NPs were synthesized by a facile hydrothermal route in the presence of citric acid. Second, rhodamine B was reacted with hydrazine hydrate to obtain rhodamine B hydrazide (RBH). Finally, RBH was conjugated on the surface of Ni(OH)₂/HAP-COOH NPs to form Ni(OH)₂/HAP-RBH. As affinity adsorbents, these NPs can directly purify histidine-tagged (His-tagged) proteins from a mixture of lysed cells, and exhibit high protein adsorption capacity with a maximum value of 115 mg g⁻¹. A prominent fluorescence enhancement at 578 nm was observed in the presence of Pt²⁺, accompanied by a change in absorption spectrum. These NPs display excellent selectivity and sensitive recognition of Pt²⁺ in comparison with other metal ions and anions with a detection limit of 0.03 μM. These NPs exhibit low cytotoxicity and can be used as a probe for Pt²⁺ and living cell imaging.