Magnetically Responsive Enzyme and Hydrogen-Bonded Organic Framework Biocomposites for Biosensing

Abstract

The one-pot synthesis of multicomponent hydrogen-bonded organic framework (HOF) biocomposites is reported. The co-immoblization of enzymes and magnetic nanoparticles (MNPs) into the HOF crystals yielded biocatalysts (MNPs-enzyme@BioHOF-1) with dynamic localization properties. Using a permanent magnet, it is possible to separate the MNPs-enzyme@BioHOF-1 particles from a solution. Catalase (CAT) and glucose oxidase (GOx) show increased retention of their activity when coimmobilized with MNPs. MNPs-GOx@BioHOF-1 biocomposites are used to prepare a proof-of-concept glucose microfluidic biosensor, where a magnet allow to position and keep in place the biocomposite inside a microfluidic chip. The magnetic response of these biocatalysts can pave the way for new applications for the emerging HOF biocomposites.

Keywords: HOF; biocatalysis; biocomposite; biosensor; enzyme.

Figure 1

Schematic view of the precursors (left) of the one‐pot synthetic procedure and of the resulting micrometric crystals in water (center) that can be recovered with the help of a permanent magnet (right).

Figure 2

a) XRD patterns of MNPs‐CAT@BioHOF‐1, CAT@BioHOF‐1, and BioHOF‐1. b) FTIR spectra of MNPs‐CAT@BioHOF‐1, CAT@BioHOF‐1, BioHOF‐1, MNPs, and CAT. c) SEM, and d) STEM micrographs of MNPs‐CAT@BioHOF‐1.

Figure 3

a) H₂O₂ and b) O₂ consumption rates catalyzed (a) by MNPs‐CAT@BioHOF‐1, CAT@BioHOF‐1, and free CAT, and b) by MNPs‐GOx@BioHOF‐1, GOx@BioHOF‐1, and free GOx. Bar charts that summarize the Encapsulation Efficiency (EE%) and Effectiveness factors (η) of the c) CAT‐containing samples, and d) GOx containing samples.

Figure 4

a–d) Schematic view of the different working steps of the proof‐of‐concept glucose flow sensor. e) Recyclability of the biosensor reported as cycle number (note: 1 cycle = time requested to process a flow of the analyte equal to the volume of the reaction cavity). The trend line (black) is qualitatively representative of the decrease in performance during the exposure to continuous glucose flow. f) Biosensor calibration curve in the glucose concentration range 0.2–2 mm (linear fit: y=(11.7 ± 0.5)+(27.1 ± 0.5)^*x, R²=0.997). g) Biosensor calibration curve in the glucose concentration range 6–20 mm (linear fit: y=(24 ± 2)+(6.7 ± 0.2)^*x, R²=0.997). Typically, after reaching the steady state, the oxygen concentration was recorded over 10 min: the final value of ΔO₂ was averaged on the steady state reached.