Click synthesis of ionic strength-responsive polyphosphazene hydrogel for reversible binding of enzymes

Abstract

In this study, a chemically crosslinkable cationic polyphosphazene was synthesized and fabricated into ionic strength-responsive hydrogels for enzyme binding. This novel polyphosphazene was synthesized via the macromolecular substitution reaction of poly(dichlorophosphazene) with 2-dimethylaminoethylamine, followed by the quaternization to yield the allyl groups. Hydrogels were easily prepared via the thiol-ene click reaction between polyphosphazene and poly(ethylene glycol) dithiol (dithiol PEG) under UV radiation. The inner three-dimensional structure of the hydrogels was investigated by swelling experiments, mechanical property tests, and field emission-scanning electron microscopy. The resulting hydrogels exhibited sensitivity to the ionic strength of the surrounding environment. Lipase from Candida rugosa was selected as the model enzyme for the entrapment in these hydrogels, resulting in a maximum enzyme loading of 16.6 mg g À1 and activity retention as high as 61.6%. Furthermore, the cationic hydrogels were effectively used for reversible enzyme binding owing to the electrostatic interaction, regulated by the ionic strength.

Design of Immobilized Enzyme Biocatalysts: Drawbacks and Opportunities

“…[109][110][111] The microenvironment of free enzyme catalysis can be imitated by the hydrated hydrogel matrix, benefiting the mobility and flexibility of the immobilized enzymes, causing a high catalytic enzymatic activity. 111 Hydrogels gain space in biologically important areas such as drug delivery and release, [112][113][114] release of DNA, 115,116 entrapment and release of enzymes 117,118 and biosensor. 119 However, enzymes immobilized in hydrogels tend to pour out of the gel, because the enzyme is basically encapsulated in the small pores of the gel, against this, functional hydrogels utilize functional building blocks, such as proteins.…”

A printable hydrogel microarray for drug screening avoids false positives associated with promiscuous aggregating inhibitors

“…In the context of these challenges, hydrogel-based enzyme immobilization platforms offer particular promise. The high water-binding capacity of hydrogels can preserve enzyme hydration over a broad range of storage/application conditions 25 – 27 , promote high enzyme mobility and flexibility 28 , and maintain physiologically mimetic conditions for optimal enzyme-catalyzed reactions 29 . In addition, the tunable porosity of hydrogels can enable selective transport of substrates to and from the entrapped enzyme via size selectivity 30 , offering potential to sterically block a drug aggregate from reaching the enzyme-binding site and thus minimize (or even eliminate) issues associated with promiscuous inhibition.…”

Rapid swelling and deswelling of semi‐interpenetrating network poly(acrylic acid)/poly(aspartic acid) hydrogels prepared by freezing polymerization

“…Ionic‐strength‐responsive hydrogels hold great potential in applications such as biosensors and delivery systems for genes and proteins because they mimic the natural environment for biomolecules and ensure the stability of the biomolecules residing in their internal structure . An ionic‐strength‐responsive hydrogel was successfully used as a glucose sensor and in a reversible enzyme binding system . For example, glucose in the human body can trigger the swelling of polyacrylamide hydrogels embedded with glucose oxidase because of the increasing concentration of the anionic glucose oxidase flavin adenine dinucleotide prosthetic group .…”

“…A stimulus‐responsive hydrogel responds to changes in environmental conditions (e.g., pH, ionic strength, temperature, light, biomolecules, electric and magnetic fields) by undergoing abrupt changes in its volume . Ionic‐strength‐responsive hydrogels hold great potential in applications such as biosensors and delivery systems for genes and proteins because they mimic the natural environment for biomolecules and ensure the stability of the biomolecules residing in their internal structure . An ionic‐strength‐responsive hydrogel was successfully used as a glucose sensor and in a reversible enzyme binding system .…”