HRP@ZIF-8/DNA Hybrids: Functionality Integration of ZIF‑8 via Biomineralization and Surface Absorption

Zeolitic imidazolate framework-8 (ZIF-8) has been successfully employed as a protective coating to encapsulate enzyme via various immobilization strategies by recent works. However, in all of the research, ZIF-8 only acts as the enzyme-immobilization matrix. In this work, by exploiting the fluorescence quenching properties of the ZIF-8 surface, we for the first time properly amalgamated the basic functionalities of ZIF-8 for horseradish peroxidise (HRP) encapsulation and fluorescence quencher by constructing HRP@ZIF-8/DNA hybrids and gave the successive detection of Hg²⁺ and phenol. Specifically, we introduced a biomimetic mineralization approach for facile encapsulation of HRP by ZIF-8 with high HRP-encapsulation efficiency (98.4%). Indeed, the HRP@ZIF-8 biocomposite functioned as an active biocatalyst under biologically challenging conditions, such as alkaline condition, high temperature, organic solvent, long-term storage, and continuous operation. After addition of FAM-labeled single-stranded DNA (ssDNA), the HRP@ZIF-8/DNA hybrid system could achieve rapid, specific, and sensitive detection of Hg²⁺ with a detection limit as low as 0.22 nM. Subsequently, benefiting from excellent catalytic activity of as-obtained HRP@ZIF-8 biocomposite, which could be successively utilized as a colorimetric sensor for sensitive measurement of phenol in micromolar level. It is believed that our strategy provides a convenient and efficient method for functionality integration of ZIF-8 without any complex modification. To the field of biosensing, our discovery broadens up the potential of bio-ZIF-8 composite for successive detection of two pollutants.