skip to main content

Explore Research Products in the NSF-PAR

Title: Temperature-responsive supramolecular hydrogels
Hydrogels comprise a class of soft materials which are extremely useful in a number of contexts, for example as matrix-mimetic biomaterials for applications in regenerative medicine and drug delivery. One particular subclass of hydrogels consists of materials prepared through non-covalent physical crosslinking afforded by supramolecular recognition motifs. The dynamic, reversible, and equilibrium-governed features of these molecular-scale motifs often transcend length-scales to endow the resulting hydrogels with these same properties on the bulk scale. In efforts to engineer hydrogels of all types with more precise or application-specific uses, inclusion of stimuli-responsive sol–gel transformations has been broadly explored. In the context of biomedical uses, temperature is an interesting stimulus which has been the focus of numerous hydrogel designs, supramolecular or otherwise. Most supramolecular motifs are inherently temperature-sensitive, with elevated temperatures commonly disfavoring motif formation and/or accelerating its dissociation. In addition, supramolecular motifs have also been incorporated for physical crosslinking in conjunction with polymeric or macromeric building blocks which themselves exhibit temperature-responsive changes to their properties. Through molecular-scale engineering of supramolecular recognition, and selection of a particular motif or polymeric/macromeric backbone, it is thus possible to devise a number of supramolecular hydrogel materials to empower a variety of future biomedical applications.  more » « less
Award ID(s):
1944875
NSF-PAR ID:
10215872
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Journal of Materials Chemistry B
Volume:
8
Issue:
40
ISSN:
2050-750X
Page Range / eLocation ID:
9197 to 9211
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ( , Advanced Functional Materials)
    Abstract

    Dynamic hydrogel crosslinking captures network reorganization and self‐healing of natural materials, yet is often accompanied by reduced mechanical properties compared to covalent analogs. Toughening is possible in certain materials with processing by directional freeze‐casting and salting‐out, producing hierarchically organized networks with directionally enhanced mechanical properties. The implications of including dynamic supramolecular crosslinking alongside such processes are unclear. Here, a supramolecular hydrogel prepared from homoternary crosslinking by pendant guests with a free macrocycle is subsequently processed by directional freeze‐casting and salting‐out. The resulting hydrogels tolerate multiple cycles of compression. Excitingly, supramolecular affinity dictates the mechanical properties of the bulk hydrogels, with higher affinity interactions producing materials with higher Young's modulus and enhanced toughness under compression. The importance of supramolecular crosslinking is emphasized with a supramolecular complex that is converted in situ into a covalent crosslink. While supramolecular hydrogels do not fracture and spontaneously self‐heal when cut, their covalent analogs fracture under moderate strain and do not self‐heal. This work shows a molecular‐scale origin of bulk hydrogel toughening attributed to affinity and dynamics of supramolecular crosslinking, offering synergy in combination with bulk post‐processing techniques to yield materials with enhanced mechanical properties tunable at the molecular scale for the needs of specific applications.

     
    more » « less
  2. ; ; ( , Angewandte Chemie)
    Abstract

    DNA is a true polymer that stores the genetic information of an organism. With its amazing biological and polymeric characteristics, DNA has been regarded as a universal building block for the construction of diverse materials for real‐world applications. Through various approaches including ligation, polymerization, chemical crosslinking, and physical crosslinking, both pure and hybrid DNA gels have been developed as generic materials. This Review discusses recent advances in the construction of DNA‐based networks without considering any of DNA′s genetic properties. In addition, we highlight the biomedical and non‐biomedical applications of DNA as generic materials. Owing to the superb molecular recognition, self‐assembly, and responsiveness of DNA, a mushrooming number of DNA materials with various properties have been developed for general utilization.

     
    more » « less
  3. ; ; ( , Angewandte Chemie International Edition)
    Abstract

    DNA is a true polymer that stores the genetic information of an organism. With its amazing biological and polymeric characteristics, DNA has been regarded as a universal building block for the construction of diverse materials for real‐world applications. Through various approaches including ligation, polymerization, chemical crosslinking, and physical crosslinking, both pure and hybrid DNA gels have been developed as generic materials. This Review discusses recent advances in the construction of DNA‐based networks without considering any of DNA′s genetic properties. In addition, we highlight the biomedical and non‐biomedical applications of DNA as generic materials. Owing to the superb molecular recognition, self‐assembly, and responsiveness of DNA, a mushrooming number of DNA materials with various properties have been developed for general utilization.

     
    more » « less
  4. ; ; ; ( , Macromolecular Bioscience)
    Abstract

    In an effort to augment the function of supramolecular biomaterials, recent efforts have explored the creation of hybrid materials that couple supramolecular and covalent components. Here, the benzenetricarboxamide (BTA) supramolecular polymer motif is modified to present a phenylboronic acid (PBA) in order to promote the crosslinking of 1D BTA stacks by PBA–diol dynamic‐covalent bonds through the addition of a multi‐arm diol‐bearing crosslinker. Interestingly, the combination of these two motifs serves to frustrate the resulting assembly process, yielding hydrogels with worse mechanical properties than those prepared without the multi‐arm diol crosslinker. Both systems with and without the crosslinker do, however, respond to the presence of a physiological level of glucose with a reduction in their mechanical integrity; repulsive electrostatic interactions in the BTA stacks occur in both cases upon glucose binding, with added competition from glucose with PBA–diol bonds amplifying glucose response in the hybrid material. Accordingly, the present results point to an unexpected outcome of reduced hydrogel mechanics, yet increased glucose response, when two disparate dynamic motifs of BTA supramolecular polymerization and PBA–diol crosslinking are combined, offering a vision for future preparation of glucose‐responsive supramolecular biomaterials.

     
    more » « less
  5. ; ; ; ( , Soft Matter)
    null (Ed.)
    Supramolecular hydrogels formed by noncovalent self-assembly of low molecular weight (LMW) agents are promising next-generation biomaterials. Thixotropic shear response and mechanical stability are two emergent properties of hydrogels that are critical for biomedical applications including drug delivery and tissue engineering in which injection of the hydrogel will be necessary. Herein, we demonstrate that the emergent thixotropic properties of supramolecular phenylalanine-derived hydrogels are dependent on the conditions in which they are formulated. Specifically, hydrogels formed from fluorenylmethoxycarbonyl (Fmoc) modified phenylalanine derivatives, 3-fluorophenylalanine (Fmoc-3F-Phe) and pentafluorophenylalanine (Fmoc-F5-Phe), were characterized as a function of gelation conditions to examine how shear response and mechanical stability properties correlate to mode of gelation. Two distinct methods of gelation were compared. First, spontaneous self-assembly and gelation was triggered by a solvent exchange method in which a concentrated solution of the gelator in dimethylsulfoxide was diluted in water. Second, gelation was promoted by dissolution of the gelator in water at basic pH followed by gradual pH adjustment from basic to mildly acidic by the hydrolysis of glucono-delta-lactone. Hydrogels formed under solvent exchange conditions were mechanically unstable and poorly shear-responsive whereas hydrogels formed by gradual acidification were temporally stable and had highly shear-responsive viscoelastic character. These studies confirm that gelation environment and mechanism have a significant influence on the emergent properties of supramolecular hydrogels and offer insight into how gelation conditions can be used to tune hydrogel properties for specific applications. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email