Transition-frequency dielectrophoresis for antibiotic detection through binding-induced interfacial charge modulation.

Frequency-domain electrokinetic readouts that directly translate small-molecule recognition into experimentally robust analytical signals remain underdeveloped. Herein, we establish transition-frequency dielectrophoresis (DEP) as a sensing modality in which binding-induced interfacial charge modulation at microparticle interfaces is converted into a measurable shift in the levitation-to-sedimentation transition frequency. Molecular recognition by surface-immobilized oligonucleotide probes perturbs the interfacial electrical state of the particles, thereby changing their frequency-dependent DEP response under an alternating-current electric field. The analytical output is defined as the shift in the frequency at which particle sedimentation is completed. Using this framework, kanamycin and streptomycin were detected with concentration-dependent responses in deionized water and drinking water, and in 1000-fold diluted samples of lysogeny broth and human serum. Distinct probe-particle populations further enabled multiplexed detection within a single measurement. Moreover, a complementary DNA-based competitive design extended the same transduction principle to the neutral antibiotic chloramphenicol, for which direct binding generates only limited interfacial perturbation. These results establish transition-frequency DEP sensing as a mechanistically grounded electrokinetic framework for antibiotic detection and, potentially, broader small-molecule sensing.