Characterization of Lactoperoxidase (LPO) Enzyme Thin Films for Volatile Organic Compound (VOC) Sensing

Spin-coated thin films of lactoperoxidase enzyme (LPO) were used on conjunction with the bio-composite (chitosan-gelatin), glutaraldehyde and cysteine as first-layers to characterize the interactions on the sensing characteristics. The prospect of tuning these three under-layers is to investigate the change of active vapor binding sites of LPO film after inter-layer interactions. Initially, spin-coated thin film properties of three under-layers and LPO are investigated by reporting deposited mass and layer thickness using the quartz crystal microbalance (QCM) frequency change. LPO spin-coated films with different under-layers are exposed to formic acid, acetic acid, chloroform, acetone and ethyl acetate vapors. The response characteristics of LPO films are investigated via QCM using time dependence frequency recording. LPO films are sensitive to those five vapors and the chemical and the physical properties of the analytes affect the sensitivity and the response rate. The results showed that the structural changes in the thin film affect the number of active binding sites of sensitive layer and thus the sensor response can be enhanced.