Jet Printing Enzymes with MOF Precursors: A Novel Technique of Immobilization

By Yunpeng Bai

As a type of micro-ordered material, metal-organic frameworks (MOFs) have shown their powerful and promising applications in various fields such as storage, sensing, separation and catalysis. One particularly attractive application is to immobilize functional proteins (e.g., enzymes) within or on the surfaces of MOFs.1-3 As one of the pioneers in this field, Ge's lab in Tsinghua University firstly reported the embedment of cytochrome C (Cyt C) into ZIF-8 via de novo encapsulation.4-7 This technique allows the facial incorporation of active proteins during the MOF preparation process. Now, a new question: what is the limit of this rapid in-situ enzyme-encapsulation technique?

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Scheme 1 Illustration of printing patterned Enzyme-MOF composites using an ink-jetting printer.

Recently, Ge et al has brought with a more ambitious work: print enzymes with MOF precursors (Bioresour. Bioprocess. 2017, 4: 40;! The authors fabricated patterned enzyme-MOF composites on different substrates (e.g., paper and polymer films) with a commercially available color ink-jet printer (scheme 1), which was readily achieved by jet printing bio-inks containing protein molecules, metal ions, and organic ligands, respectively, in different cartridges. Previously, a well-defined enzyme-jet printing had been achieved to position enzymes on papers for biosensors in Ge’s lab.8 However, patterning MOFs with functional catalytic properties in a controllable manner has not been reported. Ge firstly provides a new possibility of constructing a designable, macro-ordered MOFs-containing substrate for biosensors, bioelectronics and biomedical devices. This scalable technique opens a new avenue for MOF research and gives rise to designing novel point-of-care devices with enhanced sensitivity. One can imagine that the patterned surface has arrayed MOFs ranging from nanometer to micrometer, with even a single enzyme-MOF composite resolution in the future.

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