Exploring multifaceted and highly sensitive biosensors is a major challenge in biotechnology and medical diagnosis. Here, we create a new iridium (Ir) cluster-anchored metal-organic framework (MOF, namely, IrNCs@Ti-MOF via a coordination-assisted strategy) as a peroxidase (POD)-mimetic nanoreactor for colorimetrically diagnosing hydrogen peroxide-related biomarkers. Owing to the IrNCs-N/O coordination of Ti-MOF and unique enzymatic properties of Ir clusters, the IrNCs@Ti-MOF exhibits exceptional and exclusive POD-mimetic activities (Km = 3.94 mM, Vmax = 1.70 μM s-1, and turnover number = 39.64 × 10-3 s-1 for H2O2), thus demonstrating excellent POD-mimetic detecting activity and also super substrate selectivity, which is considerably more efficient than recently reported POD mimetics. Colorimetric studies disclose that this IrNCs@Ti-MOF-based nanoreactor shows multifaceted and efficient diagnosing activities and substrate selectivity, such as a limit of detection (LOD): 14.12 μM for H2O2 at a range of 0-900 μM, LOD: 3.41 μM for l-cysteine at a range of 0-50 μM, and LOD: 20.0 μM for glucose at a range of 0-600 μM, which enables an ultrasensitive and visual determination of abundant H2O2-related biomarkers. The proposed design will not only provide highly sensitive and cheap colorimetric biosensors in medical resource-limited areas but also offer a new path to engineering customizable enzyme-mimetic nanoreactors as a powerful tool for accurate and rapid diagnosis.
Keywords: biosensor and diagnosis; iridium clusters; metal−organic frameworks; nanoreactors; peroxidase mimetics.