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An acid-resistant DNA hydrogel that is stable in an extremely acidic environment with pH as low as 1.2 has not been reported before, largely due to the instability of DNA-hybridized structures. To achieve this, adenine (A)-rich and cytosine (C)-rich oligonucleotides are rationally designed and integrated to form copolymers with acrylamide monomers via free-radical polymerization. In an acidic environment (pH 1.2–6.0), the generated copolymers form a hydrogel state, which is cross-linked by parallel A-motif duplex configurations (pH 1.2–3.0) and quadruplex i-motif structures (pH 4.0–6.0) due to the protonation of A and C bases, respectively. Specifically, the protonated A-rich sequences under pH 1.2–3.0 form a stable parallel A-motif duplex cross-linking unit through reverse Hoogsteen interaction and electrostatic attraction. Hemi-protonated C bases under mildly acidic pH (4.0–6.0) form quadruplex i-motif cross-linking configuration via Hoogsteen interaction. Under physiological pH, both A and C bases deprotonated, resulting in the separation of A-motif and i-motif to A-rich and C-rich single strands, respectively, and thereby the dissociation of the DNA hydrogel into the solution state. The acid-resistant and physiological pH-responsive DNA hydrogel was further developed for oral drug delivery to the hostile acidic environment in the stomach (pH 1.2), duodenum (pH 5.0), and small intestine (pH 7.2), where the drug would be released and absorbed. As a proof of concept, insulin was encapsulated in the DNA hydrogel and orally administered to diabetic rats. In vitro and in vivo studies demonstrated the potential usage of the DNA hydrogel for oral drug delivery.

Ions are transported across membrane mostly via carrier or channel mechanisms.H erein, au nique class of molecular-machine-inspired membrane transporters,t ermed molecular swings is reported that utilize ap reviously unexplored swing mechanism for promoting ion transport in ah ighly efficient manner.I np articular,t he molecular swing, which carries a1 5-crown-5 unit as the ion-binding and transporting unit, exhibits extremely high ion-transport activities with EC 50 values of 46 nm (a channel:lipid molar ratio of 1:4800 or 0.021 mol %relative to lipid) and 110 nm for K + and Na + ions,r espectively.R emarkably,s uch ion transport activities remain high in ac holesterol-riche nvironment, with EC 50 values of 130 (0.045 mol %r elative to lipid/cholesterol) and 326 nm for K + and Na + ions,r espectively.

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ZIF nano-dagger coated gauze was used for antibiotic-free and biocompatible wound dressing with a lower haemolytic activity, less cytotoxicity and improved wound healing performance.

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