A Lab-in-Tube platform based on Ag+-coupled hairpin aptamer and gold nanoparticles-immobilized DNA hydrogel for portable and ultrasensitive biosensing

Background The overuse of ampicillin (AMP), a pivotal antibiotic, poses severe environmental and ecological risks, necessitating portable and precise monitoring. Results A highly integrated Lab-in-Tube biosensing platform based on Ag + -coupled hairpin (Ag@hairpin) aptamer and gold nanoparticles-immobilized DNA (AuNP@DNA) hydrogel for the portable and ultrasensitive detection of AMP was developed. In this pre-assembled tube platform, Ag@hairpin aptamers and AuNP@DNA hydrogels were immobilized on the inner bottom and cap of the tube, respectively. Upon introduction of AMP, the released Ag + triggered Ag-DNAzyme to cleave S-DNA, generating abundant AuNP. These AuNP were subsequently introduced into a glucose/FeNi-doped polydopamine nanozyme (FeNi@PDA) system to generate ultrasensitive colorimetric signals. The biosensing requires only a simple two-step upside down operation in the sealed tube, achieving an excellent limit of detection (LOD) of 1.02 pg/mL. The platform demonstrated high specificity (cross-reactivity less than 4.31%) and practical applicability in environmental samples. Furthermore, the advantages of miniaturized platform, simplified operation and portability had demonstrated. Significance By integrating accurate biosensing with an ultrasensitive enzyme cascade system, this Lab-in-Tube platform may offer an advanced strategy for the portable and on-site detection of other targets.