Deposition of Intact and Active Proteins In Vacuo Using Large Argon Cluster Ion Beams

Providing inert materials with a biochemical function, for example using proteins, is a cornerstone technology underlying many applications. However, the controlled construction of protein thin films remains a major challenge. Here, an innovative solvent-free approach for protein deposition is reported, using lysozyme as a model. By diverting a time-of-flight secondary ion mass spectrometer (ToF-SIMS) from its standard analytical function, large argon clusters were used to achieve protein transfer. A target consisting of a pool of proteins was bombarded with 10 keV Ar₅₀₀₀⁺ ions, and the ejected proteins were collected on a silicon wafer. The ellipsoidal deposition pattern was evidenced by ToF-SIMS analysis, while SDS-PAGE electrophoresis confirmed the presence of intact lysozyme on the collector. Finally, enzymatic activity assays demonstrated the preservation of the three-dimensional structure of the transferred proteins. These results pave the way to well-controlled protein deposition using ion beams and to the investigation of more complex multilayer architectures.