Single-atom nanozyme immunoassay with electron-rich property for clinical patient cancer detection

Biocatalytic activity of artificial nanozymes is strongly correlated with the detection sensitivity of lateral flow immunoassays (LFIA). Modulating the electronic structure is a promising and effective strategy to improve the catalytic activity of nanozymes, but remains a challenge. In this study, we develop a single-atom nanozyme LFIA platform with high active and electron-rich Pt single atoms onto AuPd support (Pt₁/PA). The Pt₁/PA nanozymes exhibit superior peroxidase (POD)-like activity with the catalytic efficiency (K_cat/K_m) of 9.29 × 10⁶ mM⁻¹·min⁻¹, which is 315-fold higher than natural horseradish peroxidase (HRP). Density Functional Theory calculations reveal that the remarkable activity is attributed to the formation of electron-rich site of Pt single atoms through electron transfer from support to Pt 5d orbitals, as well as d-band center modulation. Moreover, more electron transfer numbers are available for Pt single atoms at the surface in the lattice than outside the lattice. Benefiting from excellent biocatalytic activity, the limits of detection (LOD) of Pt₁/PA-LFIA for carcinoembryonic antigen (CEA) and prostate-specific antigen (PSA) are 1.21 pg mL⁻¹ and 0.6 pg mL⁻¹, which are 20.4 and 13.3-fold lower than commercial enzyme-linked immunosorbent assay kits (CEA: ab264604, 24.68 pg mL⁻¹; PSA: ab264615, 8 pg mL⁻¹), respectively. More importantly, Pt₁/PA-LFIA achieves the accurate detection of prostate cancer and lung cancer clinical patients. This work presents a paradigm for ultrasensitive biomarker diagnostics based on single-atom nanozyme immunoassays.