Effect of surface chemistry on gene transfer efficiency mediated by surface-induced DNA-doped nanocomposites

Mineralized vectors for gene therapy

There is an intense interest in developing materials for safe and effective delivery of polynucleotides using non-viral vectors. Mineralization of organic templates has long been used to produce complex materials with outstanding biocompatibility. However, a lack of control over mineral growth has limited the applicability of mineralized materials to a few in vitro applications. With better control over mineral growth and surface functionalization, mineralized vectors have advanced significantly in recent years. Here, we review the recent progress in chemical synthesis, physicochemical properties, and applications of mineralized materials in gene therapy, focusing on structure-function relationships. We contrast the classical understanding of the mineralization mechanism with recent ideas of mineralization. A brief introduction to gene delivery is summarized, followed by a detailed survey of current mineralized vectors. The vectors derived from calcium phosphate are articulated and compared to other minerals with unique features. Advanced mineral vectors derived from templated mineralization and specialty coatings are critically analyzed. Mineral systems beyond the co-precipitation are explored as more complex multicomponent systems. Finally, we conclude with a perspective on the future of mineralized vectors by carefully demarcating the boundaries of our knowledge and highlighting ambiguous areas in mineralized vectors. STATEMENT OF SIGNIFICANCE: Therapy by gene-based medicines is increasingly utilized to cure diseases that are not alleviated by conventional drug therapy. Gene medicines, however, rely on macromolecular nucleic acids that are too large and too hydrophilic for cellular uptake. Without tailored materials, they are not functional for therapy. One emerging class of nucleic acid delivery system is mineral-based materials. The fact that they can undergo controlled dissolution with minimal footprint in biological systems are making them attractive for clinical use, where safety is utmost importance. In this submission, we will review the emerging synthesis technology and the range of new generation minerals for use in gene medicines.

Biomaterial substrate modifications that influence cell-material interactions to prime cellular responses to nonviral gene delivery

IMPACT STATEMENT

This review summarizes how biomaterial substrate modifications (e.g. chemical modifications like natural coatings, ligands, or functional side groups, and/or physical modifications such as topography or stiffness) can prime the cellular response to nonviral gene delivery (e.g. affecting integrin binding and focal adhesion formation, cytoskeletal remodeling, endocytic mechanisms, and intracellular trafficking), to aid in improving gene delivery for applications where a cell-material interface might exist (e.g. tissue engineering scaffolds, medical implants and devices, sensors and diagnostics, wound dressings).

Correlation of the composition of biominerals with their ability of stimulating intracellular DNA sensors and inflammatory cytokines

Biominerals (or microcalcification) deposited in soft tissues are associated with a number of pathogeneses and cancer progressions. Biominerals have also shown promise for DNA delivery and tissue engineering. Biominerals themselves may stimulate NALP3 inflammasomes, and DNA delivered by biominerals can potentially engage with intracellular DNA sensors, resulting in unwanted inflammatory responses. In this study, a library of biominerals doped with or without DNA is formed through surface-induced biomineralization. It is demonstrated that empty biominerals stimulate NALP3 inflammasomes and induce the production of IL-1β. They are also able to activate mouse embryonic fibroblasts (MEFs) and induce inflammatory cytokines, i.e. IL-6. DNA delivered by biominerals escapes the detection of TLR9, but activates DAI and inflammasomes. Furthermore, it is shown that the level of both IL-1β and IL-6 is correlated with the composition of biominerals, in particular the ratio of Mg(Sr) to Ca, and the pH sensitivity of biominerals. These results provide insights into the design of safe and effective DNA delivery systems and biocompatible implants as well as the understanding of the pathogeneses of biominerals deposited in soft tissues.

3-D Scaffold Platform for Optimized Non-viral Transfection of Multipotent Stem Cells

Optimization of non-viral gene delivery from biomaterials is of critical importance, as several material parameters are known to influence non-viral transfection efficiency. A series of previous studies have achieved screening of gene delivery vectors on two dimensional (2D) substrates, which have direct relevance to cell culture applications. There is an additional need to create screening systems that are 3-dimensional (3D), and can thus be applied to emerging tissue engineering applications. Here, we report an enhanced throughput, 3D scaffold platform to screen for the influence of mineral coating properties on stem cell transfection. Mineral coatings with a range of physicochemical properties were formed on the scaffolds within a 96-well plate format, while maintaining an interconnected macroporous scaffold structure. A series of general gene delivery parameters, including plasmid amount, N/P ratio, and cell density, were efficiently screened in scaffolds using a luciferase-encoding plasmid as a reporter. In addition, human mesenchymal stem cell (hMSC) transfection with a plasmid encoding bone morphogenetic protein-2 (BMP-2) was successfully optimized by screening a library of mineral coatings, resulting in over 5-fold increases in BMP-2 production when compared to standard techniques. Notably, the majority of BMP-2 was incorporated into the mineral coating following secretion from the cells. The 3D mineral coated scaffold platform described here may accelerate gene delivery optimization and improve the predictability of the screening systems, which could facilitate translation of gene delivery to clinical applications.

Biomineralization of hydroxyapatite on DNA molecules in SBF: morphological features and computer simulation

The hydroxyapatite (HA) formation on the DNA molecules in SBF was examined. After immersion for four weeks in SBF at 36.5 °C, the HA crystallites of ~1-14 μm in diameter grew on the surface of DNA molecules. Various morphologies were successfully observed through scanning electron microscopy analysis. The Ca/P mol ratio (1.1-1.5) in HA was estimated by energy dispersive X-ray analysis. Original peaks of both of DNA and HA were characterized by Fourier transform infrared spectroscopy. The molecular orbital computer simulation has been used to probe the interaction of DNA with two charge-balancing ions, i.e., CaOH(+) and CaH2PO4(+). The adsorption enthalpy of the two ions on ds-DNA and/or ss-DNA having large negative value (~ -60 kcal/mol per charge-balancing ion) was the evidence for the interface in mineralization of HA in SBF.