All other reagents were of analytical reagent grade or better and were used directly without further purification. Strep- tavidin magnespheres paramagnetic particles (SA-PMPs) were purchased from Promega Corporation (Madison, USA). A commer- cially available glucose meter (ACCU-CHEK Avia) and test strips were received from Roche Diagnostics India Pvt. Ltd. (Mannheim, Germany) and used at room temperature. The photographs were taken with a Panasonic DMC-FX35 digital camera (Panasonic, Japan). The sequence of PDGF-BB-binding primary aptamer and secondary aptamer (left to right: 50 to 30) used herein was synthesized and purified by Shanghai Sangon Biotech. Co. Ltd. (Shanghai, China). The sequence is shown below: