Immobilization of laccase on the functionalized methacrylate-acrylate copolymer microspheres was studied. Poly(glycidyl methacrylate-co-n-butyl acrylate) microspheres consisting of epoxy groups were synthesized using facile emulsion photocuring technique. The epoxy groups in poly(GMA-co-nBA) microspheres were then converted to amino groups. Laccase immobilization is based on covalent binding via amino groups on the enzyme surface and aldehyde group on the microspheres. The FTIR spectra showed peak at 1646 cm −1 assigned to the conformation of the polymerization that referred to GMA and nBA monomers, respectively. After modification of the polymer, intensity of FTIR peaks assigned to the epoxy ring at 844 cm −1 and 904 cm −1 was decreased. The results obtained from FTIR exhibit a good agreement with the epoxy content method. The activity of laccaseimmobilized microspheres increased upon increasing the epoxy content. Furthermore, poly(GMA-co-nBA) microspheres revealed uniform size below 2 m that contributes to large surface area of the microspheres to be used as a matrix, thus increasing the enzyme capacity and enzymatic reaction. Immobilized enzyme also shifted to higher pH and temperature compared to free enzyme.

Laccase enzyme, a commonly used enzyme for the construction of biosensors for phenolic compounds was used for the first time to develop a new biosensor for the determination of the azo-dye tartrazine. The electrochemical biosensor was based on the immobilization of laccase on functionalized methacrylate-acrylate microspheres. The biosensor membrane is a composite of the laccase conjugated microspheres and gold nanoparticles (AuNPs) coated on a carbon-paste screen-printed electrode. The reaction involving tartrazine can be catalyzed by laccase enzyme, where the current change was measured by differential pulse voltammetry (DPV) at 1.1 V. The anodic peak current was linear within the tartrazine concentration range of 0.2 to 14 μM (R2 = 0.979) and the detection limit was 0.04 μM. Common food ingredients or additives such as glucose, sucrose, ascorbic acid, phenol and sunset yellow did not interfere with the biosensor response. Furthermore, the biosensor response was stable up to 30 days of storage period at 4 °C. Foods and beverage were used as real samples for the biosensor validation. The biosensor response to tartrazine showed no significant difference with a standard HPLC method for tartrazine analysis.

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Magnetic copolymer based on poly(glycidyl methacrylate-co-N-isopropylacrylamide) microspheres was prepared by 2,2-dimethoxy-2-phenylacetophenone- (DMPP-) photo initiated and poly(vinyl alcohol)- (PVA-) stabilized single step suspension photopolymerization. The effect of chemical interaction, morphology, and thermal properties by adding 0.1% w/v Fe3O4in the copolymer was investigated. Infrared analysis (FTIR) showed that (C=C) band disappeared after copolymerization, indicating that the magnetic copolymer microspheres were successfully synthesized and two important bands at 908 cm−1and 1550 cm−1appear. These are associated with the epoxy group stretching of GMA and secondary amide (N–H/C–H) deformation vibration of NIPAAm in magnetic microspheres. The X-ray diffraction (XRD) result proved the incorporation of Fe3O4nanoparticles with copolymer microspheres as peak of Fe3O4was observed. Morphology study revealed that magnetic copolymer exhibited uniform spheres and smoother appearance when entrapped with Fe3O4nanoparticles. The lowest percentage of Fe3O4nanoparticles leached from the copolymer microspheres was obtained at pH 7. Finally, thermal property of the copolymer microspheres was improved by adding a small amount of Fe3O4nanoparticles that has been shown from the thermogram.