Biomolecules of Similar Charge Polarity Form Hybrid Gel

ABSTRACT We report intermolecular gelation of deoxyribonucleic acid (DNA) and folic acid (FA, 1% (w/v) and DNA, 0.1–0.5% (w/v)) in Dimethyl Sulfoxide (DMSO)-water solution despite both having similar net charge. Zeta potential ζ of the biopolymers was, ζDNA = −58 and ζFA = −18 mV, therefore, formation of a self-organized hybrid network structure to assign sufficient rigidity to the gel must happen in the environment of electrostatic repulsion persisting between the inter and intra polymer segments. Regardless, a stable supramolecular hydrogel was formed at room temperature of 25° C with the DNA–FA complex displaying a zeta potential of ζcomplex = −21 mV. The gel strength (low frequency storage modulus, G 0) was tunable from ≈ 500 to 50 Pa, and gelation temperature T gel from 70 to 60° C, decreasing with DNA content. These soft gels were systematically characterized over several decades of time (dynamic light scattering), and length scales (small angle neutron scattering), rheology and scanning electron microscopy to obtain a deeper understanding of the self-assembly of the DNA in the FA-dominant solution. These gels formed of same polarity biopolymers, and in a milieu of strong electrostatic repulsion, make these belong to a special class of soft matter not well studied in the past.