Characterization of structures and molecular interactions of RNA and lipid carriers using atomic force microscopy

Ribonucleic acid (RNA) and lipid are essential biomolecules in many biological processes, and hold a great prospect for biomedical applications, such as gene therapy, vaccines and therapeutic drug delivery. The char-acterization of morphology and intra-/inter-molecular interactions of RNA and lipid molecules is critical for understanding their functioning mechanisms. Atomic force microscopy (AFM) is a sophisticated technique for characterizing biomolecules featured by its piconewton force sensitivity, sub-nanometer spatial resolution, and flexible operation conditions in both air and liquid. The goal of this review is to highlight the representative and outstanding discoveries of the characterization of RNA and lipid molecules through morphology identification, physicochemical property determination and intermolecular force measurements by AFM. The first section in-troduces the AFM imaging of RNA molecules to obtain high-resolution morphologies and nanostructures in air and liquid, followed by the discussion of employing AFM force spectroscopy in understanding the nano -mechanical properties and intra-/inter-molecular interactions of RNA molecules, including RNA-RNA and RNA-biomolecule interactions. The second section focuses on the studies of lipid and RNA encapsulated in lipid carrier (RNA-lipid) by AFM as well as the sample preparation and factors influencing the morphology and structure of lipid/RNA-lipid complexes. Particularly, the nanomechanical properties of lipid and RNA-lipid characterized by nanomechanical imaging and force measurements are discussed. The future perspectives and remaining chal-lenges on the characterization of RNA and lipid offered by the versatile AFM techniques are also discussed. This review provides useful insights on the characterization of RNA and lipids nanostructures along with their mo-lecular interactions, and also enlightens the application of AFM techniques in investigating a broad variety of biomolecules.

Automated summary

This article highlights the importance of characterizing the morphology and intermolecular interactions of RNA and lipid molecules using atomic force microscopy (AFM), as well as the application of AFM in this field. The first section introduces the use of AFM imaging to obtain high-resolution morphologies and nanostructures of RNA molecules in air and liquid, and discusses the application of AFM force spectroscopy to understand the nanomechanical properties and molecular interactions of RNA molecules. The second section focuses on the studies of lipid and RNA-lipid complexes using AFM, including sample preparation and factors influencing their morphology and structure. The future perspectives and challenges in the characterization of RNA and lipid using AFM techniques are also discussed.