Multiphoton Fabrication of Proteinaceous Nanocomposite Microstructures with Photothermal Activity in the Infrared

Abstract

Two‐photon laser writing is 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 or methylene blue and the photo‐thermal effect arises from gold non‐spherically symmetric nanoparticles dispersed in the ink. Massive energy transfer of the plasmonic resonances of the gold nanoparticles to methylene blue prevents effective photo‐crosslinking of BSA. However, stable microstructures with photo‐thermal functionality can be fabricated in the rose bengal proteinaceous inks. 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−1 These proteinaceous microstructures represent therefore a promising platform for future applications in the fields like physical stimulation of cells for regenerative nanomedicine.

Harvesting Light To Produce Heat: Photothermal Nanoparticles for Technological Applications and Biomedical Devices

“…[205,206] Finally, the ability of the synthetic chemist to tailor the composition, shape dimensions and coating of NPs, and consequently their optical properties, photothermal response, and stability, allows complex, highly technological niche applications to be attained. These encompass the printing of photothermal anticounterfeit tags (e. g., for luxury goods or for encrypted writing), [199][200][201] the preparation of proteinaceous micropatterns with embedded photothermal NPs (suitable for high spatial resolution thermal stimulation of cells), [207] annealing of optical-fiber sensors bearing molecularly imprinted polymers with embedded plasmonic nanoparticles, [208,209] or photothermally driven tuning of the pore dimensions in polysulfone membranes for water filtration. [210]…”

Multiphoton Laser Fabrication of Hybrid Photo-Activable Biomaterials

“…Our group has recently used Rose Bengale as a photosensitizer to polymerize bovine serum albumin (BSA) doped with gold nanoparticles [ 30 ]. Typical laser and writing parameters were 200–300 mW over a diffraction limited spot size ( 1 ) of a Ti:Sapphire laser tuned at 780–800 nm.…”

“…Rose Bengal co-injected with fluorescent dextran 10kDa acted as a PS with 500 pJ/pulse and 40–100 raster scanning repetitions. These studies paved the path towards a series of more recent works on proteinaceous structures, again based on BSA [ 30 , 52 , 53 ]. As an example of hybrid fabrication, Su et al used BSA to fabricate micro-optics on a substrate of PDMS [ 14 ].…”

“…In this case ( 100 fs, 80 MHz), no visible plasma is formed and the optical breakdown occurs via the sudden deposition of excited electron energy. In polymers and liquids, this leads also to the formation of cavitation bubbles, particularly relevant in surgery [ 78 ] but detrimental when photo-cross-linking polymers [ 30 ].…”

“…Among the first studies of the photothermal effect in hydrogels, Palermo et al [ 142 ] demonstrated the possibility to photo-synthesize in situ spherical gold nanoparticles in PVA gels that, when irradiated at 532 nm, showed a photothermal effect ranging from 6.8 to 45 °C/W. Our group more recently fabricated microstructured proteinaceous hydrogels embedding gold nanostars and having photothermal efficiency of up to 10 under continuous wave irradiation at 800 nm [ 30 ]. It is worth mentioning that an essential step to obtain photothermally active photoresists is to avoid any chemical interaction or energy transfer between the nanoparticles and the PI in the photoresist.…”