Novel laser-based deposition of active protein thin films

This paper reports the deposition of active protein thin films by a novel l aser-based approach termed matrix-assisted pulsed laser evaporation (MAPLE) . We have deposited uniform 10 nm to nearly 1 mum thin films of insulin and horseradish peroxidase (HRP). We performed several experiments to characte rize the chemical integrity of the deposited films. Matrix assisted laser d esorption/ionization and liquid chromatography/electrospray ionization mass spectrometry experiments performed on MAPLE-deposited insulin films indica te that the laser-material interaction involved in this deposition techniqu e does not modify the protein's mass. Fourier transform infrared spectrosco py experiments show that the chemical functionality and secondary structure of MAPLE-deposited HRP are nearly identical to those of the native protein . We also find that deposited HRP films retain their ability to catalyze th e reduction of 3,3'-diaminobenzidine (DAB), suggesting that the active site of transferred proteins is unaffected by the MAPLE process. We also produc ed patterns and multilayers with feature sizes from 20 to 250 mum by deposi ting different biomaterials through a shadow mask. Patterns of physisorbed HRP were then protected from dissolution in an aqueous environment by a sem ipermeable polymer overlayer that was deposited in situ using pulsed laser deposition. This polymer membrane protects the protein pattern when it is e xposed to DAB solution and enables the optical observation of HRP activity for spots as small as 2000 mum(2). These results demonstrate that MAPLE is a preferred technique for depositing active biomolecules for applications r anging from microfluidic sensor devices to gene and protein recognition mic roarrays.