Functionalized pNIPAM-DNA Hydrogel Colorimetric Platform for Visual Detection of Low-Mass Soluble β-Amyloid Oligomers

Low-mass soluble β-amyloid oligomers (LSAβO) are critical Alzheimer’s disease (AD) biomarkers with significant diagnostic and therapeutic potential. However, their application in early screening and detection is limited by the reliance on complex analytical instruments and procedures. To address this, we developed a visual sensing platform for LSAβO detection using a functionalized pNIPAM-DNA hydrogel. Exploiting the temperature-responsive nature of pNIPAM, the hydrogel selectively incorporates and enriches LSAβO from solution via temperature-induced expansion and contraction. LSAβO binding to aptamers on the hydrogel triggers the formation of G-quadruplex DNAzymes, which catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine to generate a visible colorimetric signal. The hydrogel’s small pore size further enhances selectivity by excluding larger oligomers during real sample analysis. This sensor exhibits a linear detection range of 0.1–7.5 nM for LSAβO and a detection limit of 50 pM. Combining LSAβO enrichment and size exclusion, this functionalized pNIPAM-DNA hydrogel platform provides a cost-effective, highly sensitive, selective, and high-throughput approach for preliminary LSAβO screening and detection.