Impact of Ligand Concentration on the Properties of Nucleic-Acid-Encapsulated MOFs and Inflammation Modulation in Prostate Cancer Cells

The zeolitic imidazolate framework (ZIF) is one of the most explored metal-organic-framework-based systems for nucleic acid delivery to cancer cells. Current nucleic acid delivery tools exhibit several drawbacks, such as high manufacturing costs, endosomal entrapment, toxicity, and immunogenicity. However, the biomimetic mineralization of Zn-based ZIFs offers a low-cost and facile encapsulation of nucleic acids at room temperature in aqueous conditions. The efficiency of nucleic acid delivery and its subsequent impact on inflammation in cells are influenced by the physicochemical properties of the material. The imidazole content determines the formation and crystallinity of ZIF, and an optimal ratio ensures the formation of well-defined and highly crystalline structures. In this study, a series of siRNA-encapsulated ZIFs (siRNA@ZIF) were systematically prepared by varying ligand-to-metal (L/M) molar ratios. Our study demonstrates that variations in ligand concentrations influence the crystalline structures, particle size, and shape of siRNA@ZIF particles. At low L/M, two-dimensional siRNA@ZIF particles form with a size of 1 μm. As the L/M ratio increases gradually, the particle size decreases, resulting in three-dimensional particles ∼200 nm in size. We also observed better stability of siRNA@ZIF in water prepared using high L/M values and time-dependent cellular uptake by the cells. Additionally, no significant impact of the biocomposites on inflammation was found, indicating the lack of an unwanted immune response and nonimmunotoxic nature over longer periods (96 h). These findings highlight the necessity of fine-tuning ligand concentrations and synthesis chemistry in designing efficient and optimal ZIF-based systems as versatile delivery platforms for nucleic acids.