Abstract The overall goal of this proposal is to develop novel biomaterials for intracellular therapeutics delivery. While messenger RNAs (mRNAs) are recognized as promising candidates for RNA therapeutics (such as anti- inflammatory drugs) as well as research tools (such as delivering Cas9 mRNA for gene editing), unlike many chemical molecules or antibody proteins, mRNAs need to be delivered into cell cytoplasm to be functional. Various types of materials have been developed for successful intracellular delivery of small RNAs, but it is still a major challenge to achieve effective delivery of mRNAs at both cellular and systemic levels. We aim to overcome this by optimizing the biointerface properties of DNA-inspired Janus base biomaterials using computational methods for molecular design, with experimental validation. There are two important obstacles for effective mRNA delivery: at the cellular level, the delivered RNA cargos can be trapped and degraded inside cell endosomes after endocytosis (internalization by cells). For example, lipid nanoparticles (LNPs) are commonly used delivery vehicles for mRNA in both academic and industrial settings. However, the effectiveness of conventional LNPs is limited by their poor endosomal escape ability which leads to the destruction of a significant portion of RNA cargos. At the systemic level (when administrated intravenously), RNA delivery materials usually require surface modifications to reduce specific and non-specific binding of serum proteins (or formation of protein coronas), increase blood circulation time, and improve biodistribution. Polyethylene glycol (PEG) is a widely used surface modification polymer in clinics, but its efficacy is significantly restricted because it can cause undesired immunogenicity in patients. To overcome these limitations, we will develop a novel delivery technology by manipulating the biointerface properties of the DNA-inspired Janus base nanopieces (JBNps). JBNps are slimmer than conventional spherical particles, allowing for enhanced infiltration into tissue matrices and barriers. As a result, JBNps have a distinct advantage for delivery into “hard-to-penetrate” tissues such as articular cartilage and kidneys. Our central hypothesis of this study is that sidechain and zwitterionic modifications can manipulate biointerface properties of JBNps, accomplishing highly effective mRNA delivery into target tissues. Once our hypothesis is confirmed, we can use JBNps to deliver mRNA for articular cartilage and kidney applications such as anti- inflammatory mRNA therapeutics.