Comparative study on Pulsed Laser Deposition and Matrix Assisted Pulsed Laser Evaporation of urease thin films

Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition from two types of targets: frozen water solutions of urease with different concentrations (1–10% m/v) and pure urease pellets. The fluence of the ablating KrF excimer laser was varied between 300 and 2200 mJ/cm2. Fourier transform infrared spectra of the deposited films showed no difference as compared to the original urease. Morphologic studies proved that the films consist of a smooth “base” layer with embedded micrometer-sized droplets. Absorption-coefficient measurements contradicted the traditional “absorptive matrix” model for MAPLE deposition. The laser energy was absorbed by urease clusters leading to a local heating-up and evaporation of the frozen matrix from the uppermost layer accompanied by the release of dissolved urease molecules. Significant enzymatic activity of urease was preserved only during matrix assisted transfer.