Background/Objectives: Prostate cancer is the most commonly diagnosed cancer in men and a leading cause of cancer-related mortality, highlighting the need for delivery systems capable of efficiently transporting both chemotherapeutic drugs and therapeutic genes to tumor cells. Generation-3 diaminobutyric polypropylenimine (DAB) dendrimers display low toxicity, high drug loading capacity and efficient gene delivery, and can be engineered as camptothecin-bearing PEGylated carriers complexed with plasmid DNA. The aim of this study was to compare microfluidic processing with conventional hand mixing for the preparation of camptothecin-bearing PEGylated DAB dendriplexes and to evaluate the impact of formulation methods and microfluidic parameters on their physicochemical properties, cellular uptake and gene expression in prostate cancer cells. Methods: Camptothecin-bearing PEGylated DAB dendrimers were synthesized and complexed with plasmid DNA to form dendriplexes. Formulations were prepared either by microfluidics, using different total flow rates and aqueous: organic flow rate ratios, or by conventional hand mixing. The resulting dendriplexes were characterized for DNA condensation, particle size, polydispersity index and zeta potential. Morphology was assessed by transmission electron microscopy. Cellular uptake of fluorescein-labelled DNA and β-galactosidase reporter gene expression were evaluated in PC3-Luc and DU145 prostate cancer cells. Results: Both microfluidic and hand-mixed methods produced stable, nanosized, positively charged dendriplexes with efficient and sustained DNA condensation (more than 99% over 24 h). Microfluidic processing, particularly at an aqueous: organic flow rate ratio of 3:1, yielded dendriplexes with hydrodynamic diameters and zeta potentials comparable to or slightly improved over hand-mixed formulations. These microfluidic conditions significantly enhanced cellular uptake in both PC3-Luc and DU145 cells. In PC3-Luc cells, this translated into β-galactosidase expression levels comparable to hand-mixed dendriplexes and higher than naked DNA, whereas in DU145 cells, transfection efficiencies remained modest for all formulations despite increased uptake. Conclusions: Microfluidic processing enables the reproducible and scalable preparation of camptothecin-bearing PEGylated DAB dendriplexes with tunable physicochemical properties. Under selected conditions, in vitro cellular uptake and gene expression were comparable to conventional hand mixing, supporting microfluidics as a robust alternative platform for the manufacture of dendrimer-based systems for combined chemo–gene delivery in prostate cancer.

Background: An efficient formulation of lipid nanoparticles (LNPs) is often considered crucial in the successful development of nucleic acid therapeutics. This study explores the impact of varying the lipid and payload concentrations as starting materials on key LNP properties. Results: The outcomes of the study revealed that the desired particle properties could be retained even at a starting lipid mixture concentration of 70 mg/mL. Particle size remained largely unchanged despite changes in lipid mixture concentration, with polydispersity index values below 0.2. CryoTEM analysis revealed that LNPs prepared using higher lipid mixture concentrations were more uniform and more abundant in solid core morphologies. Buffer composition was shown to influence the LNP particle size, surface charge, and gene expression, as well as storage stability. In vivo studies in mice showed enhanced gene expression and biodistribution for LNPs formulated at higher lipid and RNA concentrations, with LNPs in Tris-sucrose eliciting superior gene expression compared to LNPs in PBS. Conclusions: This study demonstrated that intensified mixing processes based on confined jet-impingement allow the use of elevated starting material concentrations in LNP formulations, resulting in improved biological performance and stability of mRNA-LNPs, as well as enhanced scalability and throughput.