Synthetic Strategies for mRNA Encapsulation and Delivery with MOFs

Study Background and Research Question

The rapid development and deployment of mRNA therapeutics—exemplified by mRNA vaccines—has highlighted the need for efficient, safe, and stable gene delivery platforms. Traditional viral vectors, while effective, face clinical constraints such as immune activation, production complexity, and limited cargo capacity. Non-viral vectors, including lipid nanoparticles and polymers, have broadened the toolbox for nucleic acid delivery, but the encapsulation and long-term stabilization of large transcripts like mRNA remain challenging. Metal-organic frameworks (MOFs), crystalline materials composed of metal ions and organic linkers, have recently emerged as versatile carriers in biomedical applications. However, until now, MOF-based systems had not demonstrated successful mRNA encapsulation and delivery in biological settings. The study by Lawson et al. (DOI:10.1002/adfm.202504465) directly addresses this knowledge gap.

Key Innovation from the Reference Study

The seminal innovation of this research lies in the development of a robust MOF-based platform, specifically leveraging zeolitic imidazole framework-8 (ZIF-8), for the encapsulation, delivery, and stabilization of mRNA. The authors demonstrate, for the first time, that by integrating polyethyleneimine (PEI) as a polymeric core, ZIF-8 can efficiently encapsulate mRNA into a core-shell nanoparticle, preserving its integrity and enabling functional delivery to mammalian cells and in vivo tissues. Importantly, this strategy not only ensures mRNA protection in physiological conditions but also facilitates long-term storage at room temperature, directly addressing stability issues that have hindered translation of mRNA therapeutics.

Methods and Experimental Design Insights

The research employed a stepwise synthetic strategy. Initially, attempts to directly encapsulate mRNA within ZIF-8 resulted in rapid loss of nucleic acid in biological media—a major hurdle for practical applications. To overcome this, the team incorporated PEI, forming a PEI-mRNA polyplex, which then served as a template for ZIF-8 growth. This resulted in hybrid nanoparticles with a PEI/mRNA core and ZIF-8 shell.

• Encapsulation was performed under mild aqueous conditions to preserve mRNA stability.
• Physicochemical characterization confirmed the formation of uniform nanoparticles and successful mRNA loading.
• In vitro transfection assays were conducted in multiple mammalian cell lines, comparing MOF-based delivery to standard lipid-based reagents.
• In vivo experiments involved intramuscular injection of encapsulated mRNA in mice, assessing both expression and biodistribution.
• Stability assessments evaluated mRNA integrity and expression after prolonged storage at room temperature.

Protocol Parameters

• PEI concentration for mRNA complexation: Typically 2:1 to 3:1 (PEI:RNA, w/w) for stable core formation before ZIF-8 mineralization.
• ZIF-8 shell synthesis: 2-methylimidazole and zinc nitrate supplied at 160:1 ligand:metal molar ratio in aqueous buffer, with gentle mixing at room temperature for 30 minutes.
• Storage stability assay: Encapsulated mRNA nanoparticles stored at 25°C for up to 3 months; in vivo activity confirmed after 1 month of ambient storage.
• Transfection in cell culture: 24-hour incubation with nanoparticles at 0.5–2 µg mRNA per well, followed by luciferase reporter assay.
• Animal dosing: Intramuscular injection of 5–10 µg mRNA-equivalent nanoparticles per mouse, with bioluminescence imaging at 24–48 hours post-injection.

Core Findings and Why They Matter

The core findings from Lawson et al. (reference study) are multifold:

• Efficient mRNA encapsulation and delivery: The PEI core–ZIF-8 shell architecture enabled high encapsulation efficiency and delayed mRNA release, overcoming previous limitations of MOF-based nucleic acid carriers.
• Robust protein expression: Transfection of mammalian cell lines and in vivo mouse muscle tissue resulted in protein expression levels comparable to commercial lipid nanoparticle systems, validating the platform’s functional delivery capability.
• Thermal stability: Encapsulated mRNA maintained functional activity after storage at room temperature for three months (in vitro) and one month (in vivo), representing a significant advance for cold-chain-independent mRNA therapeutics.
• Biocompatibility and tunability: The use of non-viral, inorganic–organic hybrid particles with customizable surface properties offers advantages for immunogenicity suppression and targeted delivery.

Collectively, these results point to the feasibility of using MOF-based carriers for in vivo mRNA delivery and long-term storage—two critical hurdles for clinical translation and global distribution of mRNA-based therapies.

Comparison with Existing Internal Articles

Several recent internal articles have explored the design and application of advanced mRNA reporters for delivery and imaging, such as EZ Cap™ Cy5 Firefly Luciferase mRNA (5-moUTP) and its role in quantifying gene delivery efficacy and suppressing innate immune activation. These resources discuss the use of 5-moUTP modified mRNA with Cap1 capping and Cy5 fluorescent labeling, enabling real-time tracking of mRNA uptake and translation efficiency in mammalian cells. While the Lawson et al. study focuses on the carrier system (MOFs), the internal articles emphasize reporter mRNA design and dual-mode detection strategies, such as combining fluorescence and bioluminescence imaging for in vivo studies (see here).

Both approaches are synergistic: robust mRNA encapsulation (as in MOF-based vectors) and advanced reporter mRNA (such as Cy5-labeled Firefly Luciferase mRNA) together enable high-throughput, quantitative translation efficiency assays and detailed tracking of mRNA fate in biological systems. The integration of such technologies stands to accelerate mRNA delivery research and translational applications.

Limitations and Transferability

Despite these advances, several limitations warrant consideration. The use of PEI, while effective for complex stabilization, may raise concerns about cytotoxicity at higher doses or with repeated administration. The study primarily evaluates intramuscular delivery; broader biodistribution and targeting studies remain necessary. Additionally, the MOF formulation's compatibility with chemically modified mRNAs, such as those containing 5-methoxyuridine for immunogenicity suppression, has not been directly addressed in this study, though the principles are likely transferable. Scale-up, regulatory hurdles, and batch-to-batch reproducibility also require further validation before clinical application.

Why this cross-domain matters, maturity, and limitations

This research bridges the fields of materials science, gene therapy, and pharmaceutical formulation, demonstrating that MOF-based carriers—long established in catalysis and gas storage—can be repurposed for nucleic acid delivery with functional outcomes in living systems. The maturity of the platform is promising for preclinical studies, but its translation to diverse therapeutic contexts and regulatory approval will depend on further safety and efficacy data.

Research Support Resources

For researchers aiming to develop or benchmark mRNA delivery and transfection workflows, the use of dual-reporter, chemically modified mRNA can be invaluable. EZ Cap™ Cy5 Firefly Luciferase mRNA (5-moUTP) (SKU R1010) from APExBIO provides a Cap1-capped, 5-moUTP–modified, and Cy5-labeled reporter mRNA, supporting direct quantitation of translation efficiency and real-time tracking of intracellular mRNA fate. This resource is particularly compatible with bioluminescence and fluorescence imaging platforms, complementing MOF-based or other advanced carrier studies. For detailed workflow integration and application strategies, researchers may consult recent in-depth analyses (see here).