The development of high-performance electrochemical biosensors hinges on the integration of robust bioelectrochemical interfaces with tailored molecular architectures. In this work, a systematic investigation was conducted on core-shell guanosine-borate (GB) hydrogels to establish clear structure-property relationships governing their performance in detecting tumor markers such as alpha-fetoprotein (AFP). The study focused on four distinct GB hydrogel systems: GB-G, GB-Chx, GB-Fc, and GB-SH, each engineered with different functional groups to modulate interfacial interactions and charge transfer dynamics.
Electrochemical impedance spectroscopy (EIS) revealed that the stepwise modification of gold electrodes with hydrogels and aptamers led to progressive increases in charge transfer resistance (Rct), confirming successful immobilization.528-48-3 MedChemExpress Among all variants, GB-SH exhibited the highest Rct increase upon hydrogel coating (ΔRct,1 = 0.50-35-1 Synonym 34 kΩ), attributable to strong Au–S interactions between thiol groups and the gold surface. Similarly, GB-G and GB-SH showed significant ΔRct,2 values (0.23–0.24 kΩ) after aptamer adsorption, indicating strong hydrogen bonding between nucleobase motifs and the aptamer sequence. In contrast, GB-Chx and GB-Fc displayed minimal changes, suggesting poor aptamer binding due to hydrophobic fiber surfaces that hindered molecular recognition.
For AFP detection, the sensor response was quantified by ΔRct,3—the difference in resistance before and after antigen exposure. GB-SH and GB-G sensors demonstrated exceptional sensitivity, with ΔRct,3 values reaching 1.91 and 1.47 kΩ, respectively, at 0.0001 ng mL⁻¹ AFP. These results correlate directly with their high aptamer loading capacity and favorable surface affinity. Notably, the GB-Fc-based sensor, despite lower sensitivity, achieved a linear detection range spanning six orders of magnitude (0.0005–100 ng mL⁻¹), far exceeding that of non-redox systems. This broad dynamic range is attributed to the ferrocene moiety’s ability to mediate rapid electron transfer and amplify the electrochemical signal.
Further analysis revealed an inverse correlation between ΔRct,3 and limit of detection (LOD): higher signal change corresponded to lower LOD. The GB-SH sensor achieved an LOD of 0.076 pg mL⁻¹—among the lowest reported for AFP biosensors.PMID:30000687 However, increasing aptamer density beyond an optimal point reduced sensitivity, likely due to steric hindrance limiting conformational flexibility required for target binding. This suggests a trade-off between loading amount and accessibility.
These findings highlight that optimizing biosensor performance requires balancing multiple factors: surface chemistry for aptamer affinity, redox functionality for signal amplification, and nanostructure for mechanical stability. The data confirm that GB hydrogels are not merely passive scaffolds but active participants in the sensing process. Their tunable architecture enables rational design strategies for next-generation self-healing electrochemical platforms capable of ultra-sensitive, selective, and wide-range detection—critical for early disease diagnosis and real-time monitoring.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com