Metal-organic frameworks (MOFs) are extensively investigated and have been explored for various applications such as chromatography separation, MALDI TOF matrix, energy storage and photodynamic therapy. Recently, MOFs were utilized in the biomimetic applications, such as mimicking enzymes activity. Enzymes are recognized as one of the most effective catalysts for their high affinities towards substrates, superior catalytic efficiency and unrivalled selectivity. However, the applications of enzymes in industry are limited because of the high cost, specific reaction conditions and the fragile nature of enzymes themselves. To overcome these problems, nanoscaled UiO-66 were utilized by us as a nanoenzyme to mimic the activity of alkaline phosphatase. The nanoscaled UiO-66 showed high catalytic activity towards the substrate 4-nitrophenyl phosphate (PNPP). Meanwhile, the activity of nanoscaled UiO-66 could be modulated with different pH. We supposed that the possible mechanism is that the UiO-66 defects were totally exposed by either acid (pH ≤ 3) or base (pH = 8) treatment. Meanwhile, these defects acted as accessible active sites for the hydrolysis reaction. Actually, the micro-to-millimeter sized bulk MOFs usually give inhomogeneous dispersion and the nanoscaled MOFs are easy to form aggregates in aqueous solution, which would hinder their biomimetic applications. To overcome these shortages, very recently, two–dimensional (2–D) MOFs nanosheets with unique physical and chemical properties have attracted considerable attention. The ultrathin thickness of 2–D MOFs nanosheets makes them easily to give homogeneous dispersion in water. We demonstrated a 2-D Cu(bpy)2(OTf)2 (Cu-MOF) nanosheets (100 μg mL−1) to inhibit the activity of α-Chymotrypsin (ChT) with 96.9% of inhibition. We supposed the material can act as an effective enzyme inhibitor through competitive binding of the active site of ChT, instead of changing the enzyme’s native conformation. The competitive inhibition resulted from not only the electrostatic interaction between the nanosheets and the enzyme but also irreversible coordination interactions. The modulation of enzyme activity by 2-D MOF nanosheets will open a new direction for exploration of the MOF–bio interface in physiological and catalytic systems.

Metal-organic frameworks in biomimetic applications

256th National Meeting (2018)

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