Microfluidic synthesis of iron oxide nanoparticles for highly efficient intracellular delivery in stem cells and cancer cells

Microfluidic devices offer more accurate fluid flow control and lower reagent use for uniform nanoparticle synthesis than batch synthesis. Here, we propose a microfluidic device that synthesizes uniform iron oxide nanoparticles (IONPs) for highly efficient intracellular delivery. The 3D-printed device was fabricated, comprising two inlets in the T-shaped channel with an inner diameter of 2 mm, followed by a helical mixing channel with a single outlet. The unique geometries of this device enable accuracy and precision by allowing shortened reaction time and control fluid mixing, resulting in the production of homogenous NPs. By utilizing this device and using the co-precipitation method at room temperature, IONPs with an average cluster size of 90 nm were synthesized. The photothermal property of IONPs was explored through light-matter interaction using a nanosecond (ns) pulse laser at 1064 nm and a fluence of 35 mJ cm⁻², which helps to create transient cell membrane pores and deliver small to large biomolecules into cells by a simple diffusion process. We carried out highly efficient intracellular delivery using propidium iodide (PI) (668 Da), dextran (3 kDa), 6159 bp pcDNA3-enhanced green fluorescent protein (EGFP) and Cy-5-β-galactosidase enzyme (465 kDa) into mouse fibroblast (L929), human cervical (SiHa) cancer cells, LN229, a human glioblastoma cell line, and human mesenchymal stem cells (hMSCs). The best results achieved for Cy-5-β-galactosidase enzyme transfection in hMSCs were 98.6% transfection efficiency and 98.6% cell viability. Thus, our platform might have potential applications in cell therapeutics and diagnostics.