Paper-based genetic assays with bioconjugated gold nanorods and an automated readout pipeline

• Published in: Scientific reports Vol. 12; no. 1; pp. 6223 - 12
• Main Authors: Borri, Claudia, Centi, Sonia, Chioccioli, Sofia, Bogani, Patrizia, Micheletti, Filippo, Gai, Marco, Grandi, Paolo, Laschi, Serena, Tona, Francesco, Barucci, Andrea, Zoppetti, Nicola, Pini, Roberto, Ratto, Fulvio
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13.04.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 631/114; 631/61; 639/301; 639/624; 692/308; 692/700; Biosensing Techniques - methods; Biosensors; COVID-19 - diagnosis; Data processing; Deoxyribonucleic acid; Digoxigenin; DNA; Gold; Humanities and Social Sciences; Humans; Metal Nanoparticles; multidisciplinary; Nanoparticles; Nanotubes; SARS-CoV-2 - genetics; Science; Science (multidisciplinary); Severe acute respiratory syndrome coronavirus 2
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-022-10227-7

Paper-based biosensors featuring immunoconjugated gold nanoparticles have gained extraordinary momentum in recent times as the platform of choice in key cases of field applications, including the so-called rapid antigen tests for SARS-CoV-2. Here, we propose a revision of this format, one that may leverage on the most recent advances in materials science and data processing. In particular, we target an amplifiable DNA rather than a protein analyte, and we replace gold nanospheres with anisotropic nanorods, which are intrinsically brighter by a factor of ~ 10, and multiplexable. By comparison with a gold-standard method for dot-blot readout with digoxigenin, we show that gold nanorods entail much faster and easier processing, at the cost of a higher limit of detection (from below 1 to 10 ppm in the case of plasmid DNA containing a target transgene, in our current setup). In addition, we test a complete workflow to acquire and process photographs of dot-blot membranes with custom-made hardware and regression tools, as a strategy to gain more analytical sensitivity and potential for quantification. A leave-one-out approach for training and validation with as few as 36 sample instances already improves the limit of detection reached by the naked eye by a factor around 2. Taken together, we conjecture that the synergistic combination of new materials and innovative tools for data processing may bring the analytical sensitivity of paper-based biosensors to approach the level of lab-grade molecular tests.