Metrics & MoreArticle Recommendations CONSPECTUS: Chirality exits from molecular-level, supramolecular, and nanoscaled helical structures to the macroscopic level in biological life. Among these various levels, as the central structural motifs in living systems (e.g., double helix in DNA, α-helix, β-sheet in proteins), supramolecular helical systems arising from the asymmetrical spatial stacking of molecular units play a crucial role in a wide diversity of biochemical reactions (e.g., gene replication, molecular recognition, ion transport, enzyme catalysis, and so on). However, the importance of supramolecular chirality and its potential biofunctions has not yet been fully explored. Thus, generating chiral assembly to transfer nature's chiral code to artificial biomaterials is expected to be utilized for developing novel functional biomaterials. As one of the most commonly used biomaterials, supramolecular hydrogels have attracted considerable research interest due to their resemblance to the structure and function of the native extracellular matrix (ECM). Therefore, the performance and manipulation of chiral assembled nanoarchitectures in supramolecular hydrogels may provide useful insights into understanding the role of supramolecular chirality in biology.In this Account, recent progress on chiral supramolecular hydrogels is presented, including how to construct and regulate assembled chiral nanostructures in hydrogels with controllable handedness and then use them to develop chiral hydrogels that could be applied in biology, biochemistry, and medicine. First, a brief introduction is provided to present the basic concept related to supramolecular chirality and the importance of supramolecular chirality in living systems. The chiral assemblies in supramolecular hydrogels are strongly driven by noncovalent interactions between molecular building blocks (such as hydrogen bonding, π−π stacking, hydrophobic, and van der Waals interactions). Consequently, the handedness of these chiral assemblies can be regulated by many extra stimuli including solvents, temperature, pH, metal ions, enzymes, and photoirradiation, which is presented in the second section. This manipulation of the chirality of nanoarchitectures in supramolecular hydrogels can result in the development of potential biofunctions. For example, specific supramolecular chirality-induced biological phenomena (such as controlled cell adhesion, proliferation, differentiation, apoptosis, protein adsorption, drug delivery, and antibacterial adhesion) are presented in detail in the third section. Finally, the outlook of open challenges and future developments of this rapidly evolving field is provided. This account that highlights the diverse chirality-dependent biological phenomena not only helps us to understand the importance of chirality in life but also provides new ideas for designing and preparing chiral materials for more bioapplications.

Supramolecular fluorescent hydrogelators (SFH) have emerged as a promising system for bio-imaging applications, such as detecting molecules/signals and sensing markers of diseases with the highest specificity, mapping molecular events, in vivo tracking and understanding cell behavior, in the past few years.

No abstract

Hydrazide derivatives are known to display a wide range of biological properties including antimicrobial activities, hence making them desirable candidates for soft biomaterials. Herein, we report chiral supramolecular coassembled hydrogels obtained from two phenylalanine gelators (L/DPF and B2L/D) and two dicarbohydrazide molecules (pyridine-2,6-dicarbohydrazide (PDH) and (2,2′-bipyridine)-5,5′-dicarbohydrazide (BDH)) that exhibited enhanced mechanical properties, chirality modulation, and antimicrobial activity. Four lines of coassembled hydrogels were obtained (i.e., L/DPF–PDH, L/DPF–BDH, B2L/D–PDH, and B2L/D–BDH) through hydrogen bonding and π–π stacking with some level of an interpenetrating network, as revealed by the structural characterization analysis. Mechanical properties were significantly improved, especially in the case of hybrid gels involving BDH, with improved average elastic modulus (G′) values of 3430 and 3167 Pa for DPF–BDH and B2D–BDH (1:3, molar concentration) over 140 and 1680 Pa for DPF and B2D gelators, respectively. This was attributed to the improved π–π stacking and interpenetrating network due to the bipyridine group and its ease to form fibrous precipitates in the process of heating and cooling to room temperature. PDH, on the other hand, was able to modulate chirality in the L/DPF gelator due to its more planar and less bulky nature and showed antimicrobial activity against Pseudomonas aeruginosa (Gram-negative). Interestingly, when PDH was coassembled with the B2L/D gelator, the hybrid gels exhibited antimicrobial activity against Staphylococcus aureus (Gram-positive) and P. aeruginosa (Gram-negative) by virtue of a synergistic effect of the gelator and the azomethine group of PHD. Hence, by moving from bipyridine (BDH) to pyridine (PDH) as a core structure in the hydrazide molecules, the resulting hybrid hydrogels exhibited desirable properties of antimicrobial activity and improved mechanical attributes.

No abstract

For porous protein scaffolds to be employed in tissue-engineered structures, the development of cost-effective, macroporous, and mechanically improved protein-based hydrogels, without compromising the original properties of native protein, is crucial. Here, we introduced a facile method of albumin methacryloyl transparent hydrogels and opaque cryogels with adjustable porosity and improved mechanical characteristics via controlling polymerization temperatures (room temperature and −80 °C). The structural, morphological, mechanical, and physical characteristics of both porous albumin methacryloyl biomaterials were investigated using FTIR, CD, SEM, XRD, compression tests, TGA, and swelling behavior. The biodegradation and biocompatibility of the various gels were also carefully examined. Albumin methacryloyl opaque cryogels outperformed their counterpart transparent hydrogels in terms of mechanical characteristics and interconnecting macropores. Both materials demonstrated high mineralization potential as well as good cell compatibility. The solvation and phase separation owing to ice crystal formation during polymerization are attributed to the transparency of hydrogels and opacity of cryogels, respectively, suggesting that two fully protein-based hydrogels could be used as visible detectors/sensors in medical devices or bone regeneration scaffolds in the future.

No abstract

Molecular recognition of simple sugars is crucial due to their essential roles in most living organisms. However, it remains extremely challenging to achieve a visual recognition of simple sugars like sucrose in water media under physiological conditions. In this article, the visual recognition of sucrose is accomplished by a chiral supramolecular hydrogel formation through the co-assembly of a two-component fibrous solution (l-phenylalanine based gelator co-diaminopyridine, LDAP) and sucrose. H-bonding between the amino group of LDAP and the hydroxyl group of sucrose facilitates the gelation by loading sucrose into the LDAP solution. The formed hydrogel showed an amplified inversion of circular dichroism (CD) signals as compared to the corresponding LDAP solution. In addition, the effective chirality transfer was accompanied by a bathochromic shift in UV-Vis and FL spectra of the gel. Such a simple and straightforward chiral co-assembled strategy to visually recognize sucrose will have the potential use of smart gelators in saccharides separation and proteomics to be further applied in medical diagnostics and cell imaging.