Enantioselective Activity of Hemin in Supramolecular Gels Formed by Co-Assembly with a Chiral Gelator

Bio-Inspired Far-From-Equilibrium Hydrogels: Design Principles and Applications

Inspired from dynamic living systems that operate under out-of-equilibrium conditions in biology, developing supramolecular hydrogels with self-regulating and autonomously dynamic properties to further advance adaptive hydrogels with life-like behavior is important. This review presents recent progress of bio-inspired supramolecular hydrogels out-of-equilibrium. The principle of out-of-equilibrium self-assembly for creating bio-inspired hydrogels is discussed. Various design strategies have been identified, such as chemical-driven reaction cycles with feedback control and physically oscillatory systems. These strategies can be coupled with hydrogels to achieve temporal and spatial control over structural and mechanical properties as well as programmable lifetime. These studies open up huge opportunities for potential applications, such as fluidic guidance, information storage, drug delivery, actuators and more. Finally, we address the challenges ahead of us in the coming years, and future possibilities and prospects are identified.

Supramolecular Polyaniline-Metal Ion as Chiral Nanozymes for Enantioselective Catalysis

Understanding origin of asymmetric information encoded on chiral nanozymes is important in mediating enantioselective catalysis. Herein, the supramolecular chiral nanozymes constructed from P/M-polyaniline (P/M-PANI) nanotwists and metal ions (M2+ , M = Cu, Ni, Co, and Zn) are designed through thioglycolic acid (TA) without chiral molecules to show the regulated catalytic efficiency and enantioselectivity. With combination of chiral environment from supramolecular scaffolds and catalytic center from metal ions, the P-PANI-TA-M2+ as nanozymes show preference to 3,4-dihydroxy-S-phenylalanine (S-DOPA) oxidation while the M-PANI-TA-M2+ show better selectivity to R-DOPA oxidation. Among them, though the Cu2+ doped supramolecular nanotwists show the highest catalytic efficiency, the Co2+ doped ones with moderate catalytic efficiency can exhibit the best enantioselectivity with select factor as high as 2.07. The molecular dynamic (MD) simulation clarifies the mechanism of enantioselective catalysis caused by the differential kinetics with S/R-DOPA enantiomers adsorbed on chiral PANI surface and free in solution. This work systematically studies the synergistic effect between the chiral supramolecular nanostructures assembled by achiral species and metal ions as peroxidase-like catalytic centers to regulate the enantioselectivity, providing deep understanding of the origin of asymmetric catalysis and serving as strong foundation to guide the design of nanozymes with high enantioselectivity.

Construction of Pt/Pt-Au doped chiral nanostructures using arginine and porphyrin assemblies as templates for enantioselective photocatalysis

Chiral nanomaterials with different functions have been widely developed, but the deep understanding of the structural effects of nanocatalysts on enantioselective photocatalytic efficiency is still highly demanded. Herein, Pt and Pt-Au-bimetal-doped chiral nanostructures with various morphologies and compositions are facilely constructed using L-/D-arginine (L-/D-Arg) and mono-sulfonate tetraphenyl porphyrin (H2TPPS) assemblies as chiral templates. Interestingly, these Pt and Pt-Au-doped chiral nanostructures, including nanorods (NR) and nanospheres (NS), can be well regulated by controlling pH, ionic strength, and reaction time of the assembling system of Arg and H2TPPS. More impressively, specific Au growth direction along the Pt-doped chiral NR (L-/D-Pt-NR) is observed (from tip to middle) during the preparation of Pt-Au-bimetal-doped chiral NR (L-/D-Pt-Au-NR) and their compositions can be finely controlled by simply adjusting the concentrations of HAuCl4. As expected, the chiral nanostructures exhibit superior enantioselective photocatalytic ability toward chiral organics under visible light: the oxidation rate of L-dihydroxy-phenylalanine (L-DOPA) catalyzed by L-Pt-NR (or D-DOPA catalyzed by D-Pt-NR) is about 60% higher than that of L-DOPA catalyzed by D-Pt-NR (or L-DOPA catalyzed by D-Pt-NR). This study provides a facile strategy to construct chiral nanostructures for the photocatalytic conversion of chiral organics.

Static Retention of Dynamic Chiral Arrangements for Achiral Shear Thinning Metal-Organic Colloids

Chiral compounds are known to be important not only because they are the fundamental components of living organisms, but also for their unique chiroptical properties. In recent years, scientists have fabricated several chiral organic supramolecular aggregates by using chiral physical fields, such as vortex flow. Herein, the relationship between dynamic chiroptical properties and rheological nature is discussed, suggesting the shear thinning properties of non-Newtonian fluids might help colloidal particles adopt a chiral arrangement in vortices. Furthermore, the storage modulus of colloids could be increased by adding a linking agent, which successfully kept the dynamic chiroptical properties in the static state. Moreover, the salt effect on the host-guest interaction involved in the colloids was studied, the results suggested a significant enhancement of the transferred dynamic circular dichroism for the achiral guest molecule.