Development of aptamer-conjugated magnetic graphene/gold nanoparticle hybrid nanocomposites for specific enrichment and rapid analysis of thrombin by MALDI-TOF MS

Simple, rapid and sensitive analysis of thrombin (a tumor biomarker) in complex samples is quite clinical relevant and essential for the development of disease diagnosis and pharmacotherapy. Herein, we developed a novel method based on aptamer-conjugated magnetic graphene/gold nanoparticles nanocomposites (MagG@Au) for specific enrichment and rapid analysis of thrombin in biological samples using MALDI-TOF-MS. At first, gold nanoparticles were compactly deposited on PDDA functionalized magnetic graphene through electrostatic interaction. Afterwards, aptamer was easily conjugated to gold nanoparticles via Au-S bond formation. The as-made aptamer-conjugated nanocomposites took advantage of the magnetism of magnetic graphene, the high affinity and specificity of aptamer, facilitating a high-efficient separation and enrichment of thrombin. More importantly, due to the large surface area of the hybrid substrate, the average coverage density of aptamer achieved 0.34 nmol/mg, which enhanced the thrombin binding capacity and the recovery of thrombin in real samples. In turn, the enriched thrombin attributed to the sensitive output of MALDI-TOF mass spectrometry signal, 0.085 ng μL−1 (2.36 nM) thrombin could be detected. This proposed method has a relatively wide linear relation ranging from 0.1 ng μL−1 to 10 ng μL−1, and satisfactory specificity. The proposed high-throughput method based on MALDI-TOF MS is expected to the application in the disease biomarker detection and clinical diagnosis.