Pulsed laser deposition of bovine serum albumin protein thin films

Thin films of the bovine serum albumin protein (BSA) were prepared by pulsed laser deposition (PLD). Using a KrF excimer laser beam focused on a target made of pressed powder with a fluence in the 1-2 J cm ^-2 range, films of about 1μm thickness and low roughness could be obtained on silica substrates at room temperature and under a pressure of about 10 ^-5 mbar. The Fourier transform infrared (FTIR) spectra of the films, recorded in attenuated total reflection (ATR) configuration, are nearly identical to those of the starting powders. For fluences lower than 0.6 J cm ^-2 , however, the structure of the molecule is not preserved. Atomic force microscopy (AFM) images show the protein to be deposited as particles of about 100 nm diameter without clear ordering and the films to have low roughness. Refractive index and thickness of the films were measured by m-lines spectroscopy.