Trap-and-Lock Nano-Trap of Molecularly Imprinted Dendritic Mesoporous Core@Thermoresponsive Shield Enables Efficient Depletion of Free Biotin for Accurate Immunoassays.

The streptavidin-biotin system underpins numerous immunoassays for immobilization, labeling, and signal amplification, yet it is highly susceptible to interference from free biotin in biosamples, leading to inaccurate results and potential clinical misdiagnosis. Current countermeasures remain unsatisfactory, as antibody- or streptavidin-based scavenging strategies suffer from limited depletion capacity, poor assay compatibility, or separation-dependent workflows, making them difficult to broadly integrate into automated immunoassays. Herein, we present a rationally engineered nano-trap that ingeniously integrates a biotin-imprinted dendritic mesoporous core with a thermoresponsive shield, enabling efficient elimination of free biotin interference through a "trap-and-lock" strategy. At room temperature, the nano-trap remains in an "open" state, restricting proteins entry while allowing efficient and high-capacity trapping of free biotin, whereas at immunoassay temperature, it switches to a "close" state, firmly locking the captured biotin and preventing its rebinding to streptavidin. The thermoresponsive shield is grafted with phosphorylcholine to suppress protein adsorption, further making the nano-trap highly compatible with complex biosamples. Simply adding a trapping step prior to protein assays on a mainstream immunoassay workstation achieves an outstanding tolerance to free biotin up to 1000 ng/mL. This tolerance not only exceeds the reported biotin tolerance of many commercial immunoassays, including assays optimized for biotin interference, but also substantially covers the serum biotin levels associated with high-dose biotin therapy. The nano-trap is widely applicable to protein assays and compatible with commercial kits and instruments. Thus, this work provides an appealing approach with high translational potential for addressing biotin interference in immunoassays.