Direct detection of doxorubicin in whole blood using a hydrogel-protected electrochemical aptamer-based biosensor

Electrochemical aptamer-based biosensors (EABs) have been developed for multiple important biomarkers for their convenient and real-time features. However, the application of EABs in complex biological fluids has been limited by the rapid loss of sensitivity and selectivity due to inactivation and biofouling of aptamer probes and electrodes. To address this issue, we report the preparation of a simple hydrogel-protected aptamer-based biosensor (HP-EAB) for direct detection of Doxorubicin (DOX) in whole blood. The aptamer provides excellent selectivity for the electrochemical sensor, allowing the prepared sensor to accurately detect DOX in a 50-fold diluted whole blood sample. The agarose hydrogel coating on the electrode surface allows the passage of small molecules while hindering the adsorption of biomolecules from the whole blood matrix to the electrode surface. The experimental results show that the prepared HP-EAB has high stability compared with the unprotected EAB, and the HP-EAB maintains excellent detection performance after 7 days of storage. The hydrogel coating can effectively reduce the non-specific response to the whole blood matrix and prolong the life-time of the sensor. When used to detect DOX in rabbit whole blood, the HP-EAB exhibited excellent detection performance with a detection limit of 25.9 nM (S/N = 3) and a detection range of 0.1 μM-50 μM. The developed HP-EAB provides an excellent platform for the rapid and accurate determination of important analytes in complex biological fluids.