A novel aptamer-based online magnetic solid phase extraction method for the selective determination of 8-hydroxy-2′-deoxyguanosine in human urine

In this work, an innovative magnetic aptamer adsorbent (Fe3O4-aptamer MNPs) was synthesized for the selective extraction of 8-hydroxy-2′-deoxyguanosine (8-OHdG). Amino-functionalized-Fe3O4 was crosslinked with 8-OHdG aptamer by glutaraldehyde and fixed into a steel stainless tube as the sorbent of magnetic solid phase extraction (MSPE). After selective extraction by the aptamer adsorbent, the adsorbed 8-OHdG was desorbed dynamically and online analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS). The synthesized sorbent presented outstanding features, including specific selectivity, high enrichment capacity, stability and biocompatibility. Moreover, this proposed MSPE-HPLC-MS can achieve adsorption and desorption operation integration, greatly simplify the analysis process and reduce human errors. When compared with offline MSPE, a sensitivity enhancement of 800 times was obtained for the online method. Some experimental parameters such as the amount of the sorbent, sample flow rate and sample volume, were optimized systematically. Under the optimal conditions, low limit of detection (0.01 ng mL−1, S/N = 3), limit of quantity (0.03 ng mL−1, S/N = 10) and wide linear range with a satisfactory correlation coefficient (R2 ≥ 0.9992) were obtained. And the recoveries of 8-OHdG in the urine samples varied from 82% to 116%. All these results revealed that the method is simple, rapid, selective, sensitive and automated, and it could be expected to become a potential approach for the selective determination of trace 8-OHdG in complex urinary samples.