Poly(ethylene glycol)(PEG)-cryogels: A novel platform towards enzymatic electrochemiluminescence (ECL)-based sensor applications

Abstract

Enzymes-based electrochemical biosensors require the immobilisation of the enzymes on the electrode surfaces as well as their storage in aqueous environments to maintain the enzymatic activity. Herein, we described an enzyme-based electrochemiluminescence biosensor fabricated by incorporating oxidase enzymes (horseradish peroxidase, HRP; glucose, GOx, lactate, LOx, and cholesterol oxidases, ChOx) within poly(ethylene glycol)diacrylate (PEGDA) cryogels, which retain their activity when stored in dry conditions. The redox reactions between the oxidase enzymes and their corresponding substrates produce hydrogen peroxide that can be detected in the presence of a layer of polyluminol deposited on the electrode surface. These oxidases PEG-based cryogels were characterized using cyclic voltammetry and electrochemiluminescence (ECL) to assess the redox reactions between the enzymes and the corresponding substrates. The proposed biosensors were characterised by good stability and repeatability with a calculated limit of detections (LODs) in the micromolar concentration range. The performances of PEG cryogels over the time evidenced the stability of the as-prepared materials up to 30 days in dry conditions, confirming good retention of the encapsulated enzymes. Furthermore, the biosensors were tested in the presence of interferent species showing good selectivity. Finally, these oxidases-PEG cryogels were tested in real samples (commercial contact lenses, artificial sweat and commercial milk) confirming the suitability of such material for the detection of hydrogen peroxide with calculated LoDs as 10.37 ± 0.4 µM for HRP/contact lenses liquid; 3.87 ± 0.3 µM for GOx/artificial sweat; 1.09 ± 0.6 µM for LOx/artificial sweat; and 6.59 ± 0.5 for ChOx/milk.