Construction of NM88B(Fe)-POR/Rf equipped with hyperoxia microenvironment as a cascade nanozyme for ultrasensitive electrochemical detection of sarcosine

Abstract

High detection stability makes sarcosine oxidase (SOx) nanozyme as natural enzyme substitute, a promising sensor for prostate cancer biomarker Sarcosine (Sar). However, its limited catalytic capacity towards product (H2O2) and the following weak signal response significantly restrict the detection sensitivity of Sar. Herein, a novel NH2-MIL88B(Fe)-porphyrin/riboflavin (NM88B-POR/Rf) electrochemical sensor with a hyperoxia microenvironment and cascade reaction functions is proposed to promote catalytic H2O2 production and cascade signal amplification (from H2O2 to •OH). Fe-porphyrin implantation in NM88B-POR/Rf as bionic heme enhanced the O2-carrying capacity, thus effectively improving the sensor's utilization rate of dissolved oxygen and the catalytic H2O2 production ability of Rf. Based on enzymatic cascade strategy, NM88B in NM88B-POR/Rf as peroxidase nanozyme further catalyzed H2O2 to generate •OH. Methyl blue was used to capture •OH and enhance Sar detection sensitivity. Detection results revealed that NM88B-POR/Rf presented as low limit of detection (LOD) as 3.31 pM with detection range of 10 pM∼1 mM. The synergistic effect of the hyperoxia microenvironment and enzyme cascade make LOD about 4 orders of magnitude lower than reported state-of-the-art biosensors. Moreover, NM88B-POR/Rf has good selectivity and stability and hence also be applied to the detection of Sar in real urine.