Electron-beam patterning of biological molecules

We used a focused electron beam to crosslink hydroxyl- and amineterminated poly(ethylene glycol) to create nanosized hydrogels and thus present a new method to bring the attractive biocompatibility associated with macroscopic hydrogels into the submicron length-scale regime. Using poly(ethylene glycol) thin films on silicon and glass substrates, we generate nanohydrogels with lateral dimensions of order 200 nm which can swell by a factor of at least five, and high-density arrays of such nanohydrogels can be flexibly patterned onto silicon or glass surfaces. Significantly, the amine groups remain functional after e-beam exposure, and we show that they can be used to covalently bind proteins and other molecules. We use bovine serum albumin to amplify the number of amine groups, and we further demonstrate that different proteins can be covalently bound to different hydro gel pads on the same substrate to create multifunctional surfaces. This approach opens a new means for patterning of proteins and other biological molecules on surfaces and may be useful for controlling surface bioactivity in emerging bio/proteomic and sensor technologies.