Reliable and specific biosensing on single- and double-stranded aptamer functionalized remote dual-gate organic...

Organic field-effect transistors (OFETs) integrated with commercial transistors are promising sensing platforms characterized by enhanced device uniformity, functional diversity, and electrical output stability. Aptamers with charged backbones and a high affinity for target molecules are anticipated to mitigate the limitations imposed by Debye screening in physiological environments with high ionic strength, thereby facilitating specific biological recognition in complex surroundings. This study presents two reliable OFET aptasensors for vascular endothelial growth factor (VEGF) and offers a systematic comparison of their performance. The poly[3-(3-carboxypropyl) thiophene-2,5-diyl] (PT-COOH) transducer films on remote dual gates were functionalized with VEGF aptamer (VEap), either alone or in conjunction with its complementary single-stranded DNA (PT-VEap vs. PT-VEap/CS). The single-stranded and double-stranded aptamer-based sensors exhibited opposite changes in threshold voltage in response to VEGF, and the contribution of CS pairing to signaling was evidenced by the lower detection limit of PT-VEap/CS sensors (0.1 ng/mL) compared to that of PT-VEap sensors (1 ng/mL). PT-VEap sensors demonstrated a faster response, while PT-VEap/CS sensors provided more stable and reliable signals. Both sensors maintained high sensitivity to VEGF across a broad pH range (5-9) and ionic strength (0.05-1.0 × PBS), with a slight advantage for PT-VEap in pH resistance and for PT-VEap/CS in salt resistance. The observed differences in sensing performance can be elucidated through the field effect and double electrical layer models. Additionally, the real-time responses and specific molecular recognition of VEGF were analyzed. This study quantifies the differences between single- and double-stranded aptamer-functionalized OFET biosensors, providing foundational data for the design of cost-effective and high-performance FET aptasensors applicable in various real-world scenarios.