Liquid-colloid-solid modular assembly for three-dimensional electrochemical biosensing of small molecules.

Electrochemical biosensors hold promise for advanced analytical applications in modern life analysis due to their miniaturization and cost-effectiveness. Nevertheless, their implementation in complex biological systems necessitates overcoming challenges related to timeliness, sensitivity, and interference resistance. Here, we developed a novel DNA hydrogel three-dimensional electron transporter through liquid-colloid-solid assembly, integrating electronic mediators and employing porous electrode covers with 3D printing technology. Our approach facilitated the fabrication of a high-performance electrochemical sensor for small molecule detection, leveraging target-specific aptamers and catalytic hairpin assembly (CHA) elements within the DNA hydrogel, which exhibited outstanding selectivity, sensitivity, and universality, achieving detection limits of 0.047 nM for kanamycin and 2.67 pM for ATP. Furthermore, this sensor could detect kanamycin in real samples, demonstrating good accuracy and robust anti-interference capabilities in human serum. Our work not only possesses substantial application value in clinical sample analysis but also represents a breakthrough in traditional strategies, thereby contributing to advancements in the application of electrochemical biosensors for life analysis.

Paper Sensor Coated with a Poly(carboxybetaine)-Multiple DOPA Conjugate via Dip-Coating for Biosensing in Complex Media.

Cellulose paper is an ideal diagnostic platform for low-cost, easily disposable and lightweight implementation, but requires surface modification to achieve detection with high sensitivity and specificity in complex media. In this work, a polymer-catechol conjugate containing a superhydrophilic nonfouling poly(carboxylbetaine) (pCB) and four surface-binding l-3,4-dihydroxyphenylalanine (DOPA) groups, pCB-(DOPA)4, were applied onto a paper-based sensor surface via a simple "graft-to" immersion process to render the surface with both nonfouling and protein functionalizable properties. This dip-coating technique is effective, convenient and robust as compared to the "graft-from" techniques reported previously with similar nonfouling properties. The coated paper sensor showed both increased analyte diffusion rate and improved sensitivity of glucose detection in human blood serum. The capability of pCB-(DOPA)4-modified paper sensor for specific antigen-antibody detection was demonstrated via the covalent immobilization of bovine serum albumin antibody (anti-BSA) and fibrinogen antibody (anti-Fg) onto the pCB-coated surface via simple 1-ethyl-3-(3-(dimethylamino)propyl)-carbodiimide and N-hydroxysuccinimide (EDC/NHS) chemistry.