Microfluidic assembly of "Turtle-Like" shaped solid lipid nanoparticles for lysozyme delivery

After two decades of research in the field of nanomedicine, nanoscale delivery systems for biologicals are becoming clinically relevant tools. Microfluidic-based fabrication processes are replacing conventional tech-niques based on precipitation, emulsion, and homogenization. Here, the focus is on solid lipid nanoparticles (SLNs) for the encapsulation and delivery of lysozyme (LZ) as a model biologic. A thorough analysis was con-ducted to compare conventional versus microfluidic-based production techniques, using a 3D-printed device. The efficiency of the microfluidic technique in producing LZ-loaded SLNs (LZ SLNs) was demonstrated: LZ SLNs were found to have a lower size (158.05 +/- 4.86 nm vs 180.21 +/- 7.46 nm) and higher encapsulation efficacy (70.15 +/- 1.65 % vs 53.58 +/- 1.13 %) as compared to particles obtained with conventional methods. Cryo-EM studies highlighted a peculiar turtle-like structure on the surface of LZ SLNs. In vitro studies demonstrated that LZ SLNs were suitable to achieve a sustained release over time (7 days). Enzymatic activity of LZ entrapped into SLNs was challenged on Micrococcus lysodeikticus cultures, confirming the stability and potency of the biologic. This sys-tematic analysis demonstrates that microfluidic production of SLNs can be efficiently used for encapsulation and delivery of complex biological molecules.