Smart Lateral Flow Strip Biosensor for Visual and Portable Sensing of Antibiotic Residues Based on Cascaded Logic Circuits and DNA Biocomputations

A series of molecular logic gates with multiple biocomputing capabilities have been successfully fabricated by using four antibiotic residues [tetracycline (TET), chloramphenicol (CHL), kanamycin (KAN), and streptomycin (STR)] as inputs. The lateral flow strip biosensor was utilized to realize the visual and portable sensing of logic events. Four basic logic gates (OR, AND, XOR, and INHIBIT) and three cascade logic circuits (OR-INHIBIT-AND, 3AND-OR, and XOR-INHIBIT-OR-AND) were constructed. The red band on the test zone of the strip is used to indicate the signal output. In the logic operation, the aptamer sequence in the DNA probes was used to distinguish different antibiotic residues. Two hairpin DNAs (H1 and H2) were used as the assembly probes to improve the detection signals. Using gold nanoparticles (AuNPs) as the signal tracers, the logic results can be readily visualized with the naked eye. Our constructed logic system exhibited high specificity and good robustness, enabling the logic strip to operate even in complex seawater samples with correct biocomputing functions. With the advantages of simplicity, portability, and multiple biocomputing capabilities, the disposable logic strip can provide a promising candidate for intelligent and on-site monitoring of antibiotic residues in a resource-limited setting.