Light-activated, highly efficient intracellular biomolecular delivery using a titanium nitride micro-array device

This study investigates the effectiveness of optoporation, activated by a titanium nitride micro-array device, in transporting a wide range of biomolecules into cells. Titanium nitride is a propitious plasmonic material exhibiting localised surface plasmon resonances within the near-infrared biological transparency window. Thin films of titanium nitride were deposited on a glass substrate via sputtering, and a periodic TiN micro-array device was fabricated (1 cm × 1 cm) through photolithography and chemical etching. When the device is irradiated with a laser at 1064 nm with a laser fluence of 10.28 mJ cm^-2 and a motorised scanning speed of 5 mm s^-1 in the presence of biomolecules, photothermal bubbles form near the plasma membrane and temporarily create pores that facilitate the smooth entry of biomolecules into the cells. Our TiN micro-array device with a laser-scanning setup can transfect more than a million cells within 1 minute. Utilising this device, a variety of biomolecules, including propidium iodide (PI) dye (668.4 Da), EGFP-plasmid DNA (229.4 kDa), and β-galactosidase enzyme (465 kDa), were efficiently delivered into several mammalian cell lines (L929, SiHa, and NIH/3T3), achieving high delivery efficiency and excellent cell viability. The results highlight that the maximum delivery efficiency for the PI dye is 95%, and the cell viability reaches 98% in L929 cells. Similarly, for large molecules like the β-galactosidase enzyme, the delivery efficiency is as high as 94%, with 97% cell viability. The MTT assay confirmed that the device exhibits no cytotoxicity during cell transfection. Thus, it holds potential for applications in cell therapy and diagnostics.