Controlled Monofunctionalization of Molecular Spherical Nucleic Acids on a Buckminster Fullerene Core

Abstract

An azide-functionalized 12-armed Buckminster fullerene has been monosubstituted in organic media with a substoichiometric amount of cyclooctyne-modified oligonucleotides. Exposing the intermediate products then to the same reaction (i.e., strain-promoted alkyne–azide cycloaddition, SPAAC) with an excess of slightly different oligonucleotide constituents in an aqueous medium yields molecularly defined monofunctionalized spherical nucleic acids (SNAs). This procedure offers a controlled synthesis scheme in which one oligonucleotide arm can be functionalized with labels or other conjugate groups (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, DOTA, and Alexa-488 demonstrated), whereas the rest of the 11 arms can be left unmodified or modified by other conjugate groups in order to decorate the SNAs’ outer sphere. Extra attention has been paid to the homogeneity and authenticity of the C 60 -azide scaffold used for the assembly of full-armed SNAs.

Synthesis of an Azide- and Tetrazine-Functionalized [60]Fullerene and Its Controlled Decoration with Biomolecules

“…C10 resulted in an 8 °C decrease in the T m value, when compared to the corresponding free duplex ( ON1 + ON2 ) ( Figure 2 ). This decreased duplex stability is consistent with the previous findings of SNAs, 8 , 28 − 31 caused by an electrostatic and steric repulsion between the densely packed oligonucleotides. Interestingly, C9 showed no melting at all in the measured temperature range of 10–90 °C.…”

“…We recently communicated that multiarm C 60 -branching units (e.g., 1 ) may be contaminated by structurally similar and hardly identified derivatives. 8 Therefore, prior to the assembly of C 60 -based macromolecules, in which plausible errors may remain hidden, the homogeneity and applicability of the cores should be evaluated with small molecular ligands. After a successful synthesis of the glycoconjugates ( C4 – C7 ), we validated the applicability of 1 for the assembly of a molecularly defined SNA, in which both strands of the double helices were covalently bound to the C 60 core ( C9 ).…”

“…For example, C 60 -based glycoballs have received marked interest as potential lectin binders . More recently, 12-armed fullerene has been used for the assembly of molecular spherical nucleic acids (SNAs), − which is an attractive delivery and formulation option for therapeutic oligonucleotides. In most of the applications above, one type of ligand (e.g., sugars and oligonucleotides) is multiplied on an appropriately functionalized C 60 hexakis adduct. − However, some biomolecular applications would need a combination of different biomolecules (i.e., heteroantennary C 60 bioconjugates).…”

Assembly of Bleomycin Saccharide-Decorated Spherical Nucleic Acids

“…On the gel electrophoresis, SNA1 alone resulted in a distinct and relatively sharp band ( Scheme 4 D). A trace of a faster eluting side product was also observed (may refer to an 11-armed SNA), 49 but the overall purity of SNA1 after single RP-HPLC purification proved high. Mixtures of SNA1 with ON5 – 8 [12 equiv, samples prepared in phosphate-buffered saline (PBS) at pH 7.4] resulted in slower eluting broad bands on the gel representing the formation of the hybridization-mediated SNAs: SNA2 – SNA5 .…”

Exploring the Bioactive Potentials of C60-AgNPs Nano-Composites against Malignancies and Microbial Infections

“…The C 60 molecule is a typical football-shaped structure with carbon (C) atoms in the pentagon and hexagon configurations. It has been named after the well-known scientist Buckminster Fuller, resembling its structure to geodesic domes [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. It has been previously reported that C 60 molecules can be prepared using bottom-up techniques using arch discharge, chemical route of Chemical Vapour Deposition (CVD), etc., where refined structures of C 60 when visualized under High electron microscopy such as HR-TEM, FE-SEM could be employed for visualizing and analyzing its native configurations.…”