Confined Microenvironments from Thermoresponsive Dendronized Polymers

Confined microenvironments in biomacromolecules arising from molecular crowding account for their well-defined biofunctions and bioactivities. To mimick this, synthetic polymers to form confined structures or microenvironments are of key scientific value, which have received significant attention recently. To create synthetic confined microenvironments, molecular crowding effects and topological cooperative effects have been applied successfully, and the key is balance between self-association of structural units and self-repulsion from crowding-induced steric hindrance. In this article, formation of confined microenvironments from stimuli-responsive dendronized polymers carrying densely dendritic oligoethylene glycols (OEGs) moieties in their pendants is presented. These wormlike thick macromolecules exhibit characteristic thermoresponsive properties, which can provide constrained microenvironments to encapsulate effectively guest molecules including dyes, proteins, or nucleic acids to prevent their protonation or biodegradation. This efficient shielding effect can also mediate chemical reactions in aqueous phase, and even enhance chirality transferring efficiency. All of these can be switched off simply through the thermally-induced dehydration and collapse of OEG dendrons due to the amphiphilicity of OEG chains. Furthermore, the switchable encapsulation and release of guests can be greatly enhanced when these dendronized polymers are used as major constituents for fabricating bulk hydrogels or nanogels, which provide a higher-level confinement.

Glycosaminoglycan-Inspired Biomaterials for the Development of Bioactive Hydrogel Networks

Glycosaminoglycans (GAG) are long, linear polysaccharides that display a wide range of relevant biological roles. Particularly, in the extracellular matrix (ECM) GAG specifically interact with other biological molecules, such as growth factors, protecting them from proteolysis or inhibiting factors. Additionally, ECM GAG are partially responsible for the mechanical stability of tissues due to their capacity to retain high amounts of water, enabling hydration of the ECM and rendering it resistant to compressive forces. In this review, the use of GAG for developing hydrogel networks with improved biological activity and/or mechanical properties is discussed. Greater focus is given to strategies involving the production of hydrogels that are composed of GAG alone or in combination with other materials. Additionally, approaches used to introduce GAG-inspired features in biomaterials of different sources will also be presented.

Polysaccharide-based recoverable double-network hydrogel with high strength and self-healing properties

Polysaccharide-based hydrogels (PSBHs) have received significant attention for numerous bio-applications due to their biocompatibility and non-immunogenic performance. However, the construction of PSBH with superior mechanical properties by a simple method is rarely adequately researched. This study focuses on the construction of a novel PSBH with superior mechanical and recoverable properties by integrating the synergistic and complementary interactions of covalent bond-associated oxidized sodium alginate (SA-CHO) gel and hydrogen bond-associated agarose (Aga) gel. With the synergy and complementarity of the SA-CHO and Aga networks, the hydrogel exhibited 17 and 15 times (20 and 9 times) greater compressive stress and modulus, respectively, compared with the SA-CHO gel (Aga gel). The hydrogel also displayed excellent fatigue resistance, recurrent shapeability, acid resistance and recovery ability, as well as self-healing ability. This study provides a unique perspective for enhancing the mechanical properties of PSBH through the synergy and complementarity of different kinds of polysaccharides without sacrificing the functionality of the PSBH.

Water-soluble polyglycerol-dendronized poly(norbornene)s with functional side-chains

High molecular weight polyglycerol-dendronized poly(norbornene)s (PGD-PNBs) were prepared via ring-opening metathesis polymerization of norbornene monomers containing amine functional groups on the side-chains followed by dendron growth from the olefins of PNB backbones using iterative dihydroxylation and allylation. The fourth-generation PGD-PNB with a degree of polymerization of ca. 500 is thus functionalized with 16 peripheral hydroxyl groups as well as a single amine on each repeat unit of the PNB backbone. Furthermore, the amine functionality could be used to install hydrophobic fluorophores such as coumarin and pyrene, thereby obtaining the final PGD-PNB structures which are highly water-soluble and fluorescent.

Thermo-responsive polymers: Applications of smart materials in drug delivery and tissue engineering

Synthetic polymers are attracting great attention in the last decades for their use in the biomedical field as nanovectors for controlled drug delivery, hydrogels and scaffolds enabling cell growth. Among them, polymers able to respond to environmental stimuli have been recently under growing consideration to impart a "smart" behavior to the final product, which is highly desirable to provide it with a specific dynamic and an advanced function. In particular, thermo-responsive polymers, materials able to undergo a discontinuous phase transition or morphological change in response to a temperature variation, are among the most studied. The development of the so-called controlled radical polymerization techniques has paved the way to a high degree of engineering for the polymer architecture and properties, which in turn brought to a plethora of sophisticated behaviors for these polymers by simply switching the external temperature. These can be exploited in many different fields, from separation to advanced optics and biosensors. The aim of this review is to critically discuss the latest advances in the development of thermo-responsive materials for biomedical applications, including a highly controlled drug delivery, mediation of cell growth and bioseparation. The focus is on the structural and design aspects that are required to exploit such materials for cutting-edge applications in the biomedical field.

Synthesis of water soluble and multi-responsive selenopolypeptides via ring-opening polymerization of N-carboxyanhydrides

Synthesis of selenopolypeptides via ring opening polymerization of N-carboxyanhydrides.

Thermoresponsive dendronized chitosan-based hydrogels as injectable stem cell carriers

A combination of dendronization and Schiff-base chemistry endows injectable chitosan hydrogels with thermoresponsiveness, self-healing abilities and enhanced mechanical properties under physiological conditions.

Thermoresponsive double network cryogels from dendronized copolymers showing tunable encapsulation and release of proteins

Thermoresponsive double network cryogels were prepared from OEG-based dendronized copolymers with PVA, which can reversibly capture and release proteins.