Antigen-presenting systems at the single-cell and ensemble levels provide key insights into T-cell activation, but tools for single-molecule manipulation are lacking. We introduce a biomimetic antigen-presenting system (bAPS) using hexapod heterostructures with a hematite core and silica branches. At single-molecule resolution, we demonstrate T-cell activation by a single peptide-loaded MHC, distinct TCR responses to peptides differing by one amino acid, and superior TCR antigen sensitivity compared to CARs. Magnetic rotation of hexapods enhances immune responses in T and CAR-T cells. Our bAPS offers a precise, scalable method for identifying stimulatory TCRs, providing a unique tool for T-cell research.

The natural excitability in mammalian tissues has been extensively exploited for drug-free electroceutical therapies. However, it is unclear whether bacterial residents on the human body are equally excitable and whether their excitability can also be leveraged for drug-free bioelectronic treatment. Using a microelectronic platform, we examined the electrical excitability of Staphylococcus epidermidis, a skin-residing bacterium responsible for widespread clinical infections. We discovered that a non-lethal electrical stimulus could excite S. epidermidis, inducing reversible changes in membrane potential. Intriguingly, S. epidermidis became excitable only under acidic skin pH, indicating that the bacteria were “selective” about the environment in which they display excitability. This selective excitability enabled programmable suppression of biofilm formation using benign stimulation voltages. Lastly, we demonstrated the suppression of S. epidermidis on a porcine skin model using a flexible electroceutical patch. Our work shows that the innate excitability of resident bacteria can be selectively activated for drug-free bioelectronic control.