Microgels in Tandem with Enzymes: Tuning Adsorption of a pH‐ and Thermoresponsive Microgel for Improved Design of Enzymatic Biosensors

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Abstract
The benefits of stimuli‐responsiveness of microgels for surface modification and further engineering of microgel‐enzyme biosensor constructs are highlighted. Accordingly, the adsorption behavior of the pH‐ and temperature‐sensitive poly(N‐isopropylacrylamide‐co‐N‐(3‐dimethylaminopropyl)methacrylamide) microgel (P(NIPAM‐co‐DMAPMA) microgel) is examined by means of atomic force microscopy (AFM) and quartz‐crystal microbalance with dissipation monitoring (QCM‐D). An enhanced adsorption of the microgel onto relatively hydrophobic surfaces is observed at elevated pH and temperature as manifested by a high surface coverage and a large adsorbed mass. This is a consequence of pronounced hydrophobization of the microgel as revealed by means of dynamic light scattering (DLS) and turbidimetry (cloud points). The subsequent electrostatic loading of the surface‐bound microgel with enzymes is examined by means of QCM‐D and demonstrates a highly‐capacious integration of biomolecules into the microgel films. Finally, the biosensor responses of the microgel‐enzyme films fabricated onto screen‐printed graphite electrodes are assessed to demonstrate a biorelated application. Thus, a comprehensive conceptual understanding is attained on the key points: (1) how the stimuli‐responsive properties of the microgel correlate with its amount deposited onto the surface, (2) what determines the highly‐capacious loading of the surface‐bound microgel with the enzymes, and ultimately (3) how the tandem of the stimuli‐sensitive microgels and enzymes can be used for easy engineering of biosensor systems.
Funding Information
  • Deutsche Forschungsgemeinschaft (SFB 985)
  • Russian Foundation for Basic Research (19‐08‐00483)

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