Engineering DNA/Fe-N-C single-atom nanozymes interface for colorimetric biosensing of cancer cells

Single atom nanozymes (SAzymes) represent the state-of-the-art technology in nanomaterial-based catalysis, which have attracted attentions in catalysis, cancer treatment, disinfection and biosensing fields. However, numerous SAzymes suffered from low aqueous dispersion and without recognition capacity, which impeded their applications in bioanalysis. Herein, we engineered DNA onto SAzymes to obtain the DNA/SAzymes conjugates, which significantly improved the aqueous dispersion and recognition ability of SAzymes. We synthesized iron SAzymes (Fe-N-C SAzymes) as the catalytic nanomaterials, and investigated the interactions between Fe-N-C SAzymes and DNA. We compared A₁₅, T₁₅ and C₁₅ adsorption of Fe-N-C SAzymes in HEPES containing 2 mM MgCl₂. We found that 50 μg mL^-1 Fe-N-C SAzymes produced nearly 100% A₁₅ adsorption, 90% T₁₅ adsorption and only 69% C₁₅ adsorption, indicating that adenine and thymine had higher adsorption affinity on Fe-N-C SAzymes. More importantly, DNA modification did not affect the peroxidase-like activity of Fe-N-C SAzymes and the bioactivity of the adsorbed DNA. Taking the advantage of the diblock DNA with one DNA sequence (adenine) binding to Fe-N-C SAzymes and the other DNA sequence (i.e., aptamer) binding to cancer cells, we designed Apt/Fe-N-C SAzymes for colorimetric detection of cancer cells, which offered new insights for the use of SAzymes in biomedicine.