Direct-Write Fabrication of Functional Protein Matrixes Using a Low-Cost Q-Switched Laser

We report the use of an inexpensive, small, and “turn-key” Q-switched 532-nm Nd:YAG laser as a source for
nonlinear, direct-write protein microfabrication. In this
approach, microJoule pulses (pulse widths, ∼600 ps) are
focused using high numerical aperture optics to submicrometer focal spots, creating instantaneous intensities
great enough to promote multiphoton excitation of a
photosensitizer and subsequent intermolecular cross-linking of protein molecules. By scanning the femtoliter
focal volume through reagent solution, extended protein-based structures can be fabricated with precise, three-dimensional topographies. As with earlier studies using
a femtosecond titanium:sapphire laser costing more than
$100K, physically robust and chemically responsive
microstructures can be fashioned rapidly with feature
sizes smaller than 0.5 μm, and cross-linking can be
achieved using both biologically benign sensitizers (e.g.,
flavins) and by using the proteins themselves to sensitize
cross-linking. We demonstrate in situ fabrication to corral
neurite outgrowth and show the ability to functionalize
avidin structures with biotinylated reagents, an approach
that enables chemical sensing to be performed in specified
microenvironments. Characterization of this inexpensive,
low-power source will greatly broaden access to direct-write protein microfabrication.