Chelate-functionalized magnetic micelles for sequestration of cisplatin.

Many cancer patients suffer permanent hearing loss due to accumulation of ototoxic cisplatin in the inner ear. In this study, two types of 100 nm magnetic micelles were developed to sequester cisplatin from aqueous solutions, with the goal of eliminating cochlear ototoxins via magnetic microsurgery. The micellar surface was quantitatively functionalized with anionic S-rich ligands and the micelle core encapsulated superparamagnetic iron oxide nanoparticles. Exceptionally effective sequestration is demonstrated, with removal of greater than 95 and 50% of solution Pt, by means of centrifugal filtration and magnetic extraction. Attraction between negatively charged micellar surfaces and cationic Pt-species played a critical role and was only partially screened by physiologic salt solution. Importantly, magnetic micelles introduce negligible impact on the integrity of inner ear hair cells, demonstrating excellent biocompatibility. This study showcases successful magnetic sequestration of Pt-based ototoxins using highly applicable nano-micellar materials. More generally, these examples highlight features of the micelle-water interfacial environment that are important in developing nanomaterials for metallo-medicinal applications.

Structure-Guided Design of a Potent and Specific Inhibitor against the Genomic Mutator APOBEC3A.

Nucleic acid structure plays a critical role in governing the selectivity of DNA- and RNA-modifying enzymes. In the case of the APOBEC3 family of cytidine deaminases, these enzymes catalyze the conversion of cytosine (C) to uracil (U) in single-stranded DNA, primarily in the context of innate immunity. DNA deamination can also have pathological consequences, accelerating the evolution of viral genomes or, when the host genome is targeted by either APOBEC3A (A3A) or APOBEC3B (A3B), promoting tumor evolution leading to worse patient prognosis and chemotherapeutic resistance. For A3A, nucleic acid secondary structure has emerged as a critical determinant of substrate targeting, with a predilection for DNA that can form stem loop hairpins. Here, we report the development of a specific nanomolar-level, nucleic acid-based inhibitor of A3A. Our strategy relies on embedding the nucleobase 5-methylzebularine, a mechanism-based inhibitor, into a DNA dumbbell structure, which mimics the ideal substrate secondary structure for A3A. Structure-activity relationship studies using a panel of diverse inhibitors reveal a critical role for the stem and position of the inhibitor moiety in achieving potent inhibition. Moreover, we demonstrate that DNA dumbbell inhibitors, but not nonstructured inhibitors, show specificity against A3A relative to the closely related catalytic domain of A3B. Overall, our work demonstrates the feasibility of leveraging secondary structural preferences in inhibitor design, offering a blueprint for further development of modulators of DNA-modifying enzymes and potential therapeutics to circumvent APOBEC-driven viral and tumor evolution.

Photoactivatable Circular Caged Oligonucleotides for Transcriptome In Vivo Analysis (TIVA).

Light activation is an effective way to impart spatiotemporal control over oligonucleotide probes that are widely applied for gene expression regulation and target function investigation. Among the major oligonucleotide caging strategies, cyclization with a photocleavable linker is an elegant design, which affords both atom efficiency and stability in many biological environments. Here, we introduce an improved protocol for circular oligonucleotide synthesis requiring only one round of HPLC purification. With a series of poly-U oligonucleotide strands of different sizes and backbone modifications, the pre-photolysis caging stability and post-photolysis target binding affinity were studied through a denaturing gel assay and melting temperature measurements. A 14U 2'-OMe RNA probe was selected, with strong potential application in transcriptome in vivo analysis (TIVA) for mRNA isolation.