Biocatalytically active microgels by precipitation polymerization of N-isopropyl acrylamide in the presence of an enzyme

Bactericidal and biocatalytic temperature responsive microgel based self-cleaning membranes for water purification

The present study focuses on creating an antimicrobial and biocatalytic smart gating membrane by synthesizing unique core-shell microgels. The core-shell microgels are synthesized by grafting short chains of poly(ethylenimine) (PEI) onto a poly((N-isopropyl acrylamide)-co-glycidyl methacrylate)) (P(NIPAm-co-GMA)) core. Subsequently, the produced microgels are utilized as a substrate for synthesizing and stabilizing silver nanoparticles (Ag NPs) through an in-situ approach. These Ag NPs immobilized microgels are then suction filtered over a polyethylene terephthalate (PET) track-etched support to create cross-linked composite microgel membranes (CMMs). After structural and permeation characterization of the prepared CMMs, the laccase enzyme is then covalently grafted to the surface of the membrane and tested for its effectiveness in degrading Reactive red-120 dye. The laccase immobilized biocatalytic CMMs show effective degradation of the Reactive red-120 by 71%, 48%, and 34% at pH 3, 4, and 5, respectively. Furthermore, the immobilized laccase enzyme showed better activity and stability in terms of thermal, pH, and storage compared to the free laccase, leading to increased reusability. The unique combination of Ag NPs and laccase on a thermoresponsive microgel support resulted in a responsive self-cleaning membrane with excellent antimicrobial and dye degradation capabilities for environmentally friendly separation technology.

Simple Enzyme Immobilization for Flow Chemistry? An Assessment of Available Strategies for an Acetaldehyde-Dependent Aldolase

Enzyme immobilization is a technology that enables (bio-)catalysts to be applied in continuous-flow systems. However, there is a plethora of immobilization methods available with individual advantages and disadvantages. Here, we assessed the influence of simple and readily available methods with respect to the performance of 2-deoxy-d-ribose-5-phosphate aldolase (DERA) in continuous-flow conditions. The investigated immobilization strategies cover the unspecific attachment to carriers via epoxides, affinity-based attachment via metal ion affinity, StrepTag™-StrepTactin™ interaction as well as the covalent affinity attachment of an enzyme to a matrix tethered by the HaloTag^®. The metal-ion-affinity-based approach outperformed the other methods in terms of immobilized activity and stability under applied conditions. As most enzymes examined today already have a HisTag for purification purposes, effective immobilization may be applied, as simple as a standard purification, if needed.

Regenerable temperature-responsive biocatalytic nanofiltration membrane for organic micropollutants removal

Biocatalytic nanofiltration membranes (BNMs) exhibit great potentials in organic micropollutants removal attributed to its synergistic effect between enzyme catalysis and membrane separation. However, the difficulties in regeneration of the BNMs halted their economic practicality. Inspired by cell membranes with stimuli-responsive channels, we have developed the temperature-responsive BNMs with nanogating function by poly(N-isopropyl acrylamide) (PNIPAM) modification. PNIPAM modification increases the geometric confinement of the support layer to enzymes, thus improving enzyme loading, inhibiting enzyme leakage, and preventing membrane permeability decline caused by enzyme excess migration and aggregation. By optimizing the concentration of reaction monomers, modification time, and strategies, the PNIPAM-based BNMs show high bisphenol A (BPA) removal efficiency and long-term stability. Furthermore, the PNIPAM-polyethyleneimine-based BNMs can be easily regenerated at 38°C, and the laccase activity and BPA removal efficiency are fully recovered. This work would promote the real application of BNMs in bioconversion, drug delivery, and biosensors.

DNase I functional microgels for neutrophil extracellular trap disruption

Neutrophil extracellular traps (NETs) are web-like chromatin structures produced and liberated by neutrophils under inflammatory conditions which also promote the activation of the coagulation cascade and thrombus formation. The formation of NETs is quite prominent when blood comes in contact with artificial surfaces like extracorporeal circuits, oxygenator membranes, or intravascular grafts. DNase I as a factor of the host defense system, digests the DNA backbone of NETs, which points out its treatment potential for NET-mediated thrombosis. However, the low serum stability of DNase I restricts its clinical/therapeutic applications. To improve the bioavailability of the enzyme, DNase I was conjugated to the microgels (DNase I MG) synthesized from highly hydrophilic N-(2-hydroxypropyl) methacrylamide (HPMA) and zwitterionic carboxybetaine methacrylamide (CBMAA). The enzyme was successfully conjugated to the microgels without any alternation to its secondary structure. The K_m value representing the enzymatic activity of the conjugated DNase I was calculated to be 0.063 μM demonstrating a high enzyme-substrate affinity. The DNase I MGs were protein repellant and were able to digest NETs more efficiently compared to free DNase in a biological media, remarkably even after long-term exposure to the stimulated neutrophils continuously releasing NETs. Overall, the conjugation of DNase I to a non-fouling microgel provides a novel biohybrid platform that can be exploited as non-thrombogenic active microgel-based coatings for blood-contacting surfaces to reduce the NET-mediated inflammation and microthrombi formation.

Thermocontrolled Reversible Enzyme Complexation-Inactivation-Protection by Poly(N-acryloyl glycinamide)

A prospective technology for reversible enzyme complexation accompanied with its inactivation and protection followed by reactivation after a fast thermocontrolled release has been demonstrated. A thermoresponsive polymer with upper critical solution temperature, poly(N-acryloyl glycinamide) (PNAGA), which is soluble in water at elevated temperatures but phase separates at low temperatures, has been shown to bind lysozyme, chosen as a model enzyme, at a low temperature (10 °C and lower) but not at room temperature (around 25 °C). The cooling of the mixture of PNAGA and lysozyme solutions from room temperature resulted in the capturing of the protein and the formation of stable complexes; heating it back up was accompanied by dissolving the complexes and the release of the bound lysozyme. Captured by the polymer, lysozyme was inactive, but a temperature-mediated release from the complexes was accompanied by its reactivation. Complexation also partially protected lysozyme from proteolytic degradation by proteinase K, which is useful for biotechnological applications. The obtained results are relevant for important medicinal tasks associated with drug delivery such as the delivery and controlled release of enzyme-based drugs.