Preparation of smart soft materials using molecular complexes

Abstract

This article provides a short overview of our research regarding the preparation of smart soft materials using molecular complexes that reversibly associate and dissociate in response to environmental changes. Stimuli-responsive hydrogels that show swelling/shrinking in response to pH and temperature were prepared by copolymerization of a monomer bearing a phosphate group and other various monomers. Hydrogels with phosphate groups were useful tools for the construction of self-regulated drug delivery systems. Furthermore, we proposed a strategy for the preparation of biomolecule-responsive hydrogels that use reversible crosslinks in the networks of biomolecular complexes. Based on this strategy, we have prepared two types of biomolecule-responsive hydrogel that undergo changes in volume in response to target biomolecules. This was accomplished using biomolecular complexes such as antigen-antibody complexes and saccharide-lectin complexes and both a biomolecule-crosslinked hydrogel and a biomolecule-imprinted hydrogel have been synthesized with this approach. Biomolecule-crosslinked hydrogels, such as glucose-and antigen-responsive hydrogels, swelled in the presence of a target biomolecule due to the dissociation of biomolecular complexes that act as reversible crosslinks. On the other hand, biomolecule-imprinted hydrogels, such as tumor marker glycoprotein-responsive hydrogels, shrank in response to a target biomolecule due to the formation of a complex between ligands (lectin and antibody) and the target biomolecule. Thus, biomolecule-responsive hydrogels have many potential applications as smart biomaterials in biomedical fields. Although most smart soft materials prepared using molecular complexes still require further research, they are likely to become important materials in the future.

Molecular imprinting: perspectives and applications

“…291 Recently, biomolecule-responsive hydrogels which undergo changes in the volume in accordance with the concentration of a target biomolecule, such as glucose and protein, have become increasingly important as smart biomaterials for drug delivery systems and molecular diagnostics, because they can sense the target biomolecule and undergo structural changes. 292 In 2012, Miyata 293 prepared tumor-marker-imprinted hydrogels that shrank in the presence of a target-tumor marker glycoprotein by using various cross-linkers such as low-molecular-weight and high-molecular-weight cross-linkers. This design not only provided a basis for the development of useful biomoleculeresponsive hydrogels as smart biomaterials but also provided more insight into key factors of molecular imprinting.…”

Self‐healing biomaterials

“…Reversible supramolecular interactions in polymers are generally achieved through numerous mechanisms,95, 107, 113 including: hydrogen bonding, exemplified by the ureidopyrimidinone unit of Sijbesma and Meijer;95 metal coordination chemistry, for example silver complexation by tridentate heterocyclic peptides114 or calcium‐bridged carboxylates;115 or π‐stacking, such as that seen with triphenylene motifs 116. Other synthetic supramolecular motifs are known to function in biological environments, but an even greater repository of useful structures is likely found in biology itself; for example, peptide‐peptide, ligand‐receptor, and nucleic acid‐based interactions 103, 117–121…”

Preparation of Molecule-Responsive Microsized Hydrogels via Photopolymerization for Smart Microchannel Microvalves

“…However, very few studies have addressed molecule‐responsive hydrogels that exhibit volume changes in response to a target molecule despite their potential applications. We have developed several biomolecule‐responsive hydrogels that undergo volume changes in the presence of target biomolecules, such as glucose and proteins . The swelling/shrinking behavior of hydrogel is governed by the hydrophilicity of the polymer chains, osmotic pressure induced by charged groups, and the number of cross‐links.…”