Multiphoton fabrication of flexible photo-thermally active proteinaceous microstructures

Two-photon and single photon laser writing are used here to fabricate 3D proteinaceous microstructures with photothermal functionality in the near-infrared spectral region and tunable elasticity. The photo-cross-linking is initiated in bovine serum albumin (BSA) by Rose Bengal and the photo-thermal effect arises from gold nanostars dispersed in the ink. Massive energy transfer of the plasmonic resonances of the gold nanostars to the photo-initiator is avoided by employing an anionic photo-initiator, allowing to obtain effective photo-crosslinking of BSA and to retrieve a substantial photo-thermal efficiency of the fabricated structures. On these microstructures, with a gold atom concentration as low as 1% w/w, a highly localized temperature increase can be quickly (≅1 s) reached and maintained under continuous wave laser irradiation at 800 nm. The photothermal efficiency under continuous wave laser irradiation depends on the thickness of the microstructure and can reach 12.2 +/- 0.4 °C/W. The Young modulus of the fabricated structures is estimated from the measurement of their bending under steady flow and falls in the range of most typical tissues, suggesting that they can be adopted as promising platform for future applications in regenerative nanomedicine.