Hydrogels are hydrophilic polymer-based materials with high water content and physical characteristics that resemble the native extracellular matrix. Because of their remarkable properties, hydrogel systems are used for a wide range of biomedical applications, such as three-dimensional (3D) matrices for tissue engineering, drug-delivery vehicles, composite biomaterials, and as injectable fillers in minimally invasive surgeries. In addition, the rational design of hydrogels with controlled physical and biological properties can be used to modulate cellular functionality and tissue morphogenesis. Here, the development of advanced hydrogels with tunable physiochemical properties is highlighted, with particular emphasis on elastomeric, light-sensitive, composite, and shape-memory hydrogels. Emerging technologies developed over the past decade to control hydrogel architecture are also discussed and a number of potential applications and challenges in the utilization of hydrogels in regenerative medicine are reviewed. It is anticipated that the continued development of sophisticated hydrogels will result in clinical applications that will improve patient care and quality of life.

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25th Anniversary Article: Rational Design and Applications of Hydrogels in Regenerative Medicine

3D printing alias additive manufacturing can transform 3D virtual models created by computer-aided design (CAD) into physical 3D objects in a layer-by-layer manner dispensing with conventional molding or machining. Since the incipiency, significant advancements have been achieved in understanding the process of 3D printing and the relationship of component, structure, property and application of the created objects. Because hydrogels are one of the most feasible classes of ink materials for 3D printing and this field has been rapidly advancing, this Review focuses on hydrogel designs and development of advanced hydrogel-based biomaterial inks and bioinks for 3D printing. It covers 3D printing techniques including laser printing (stereolithography, two-photon polymerization), extrusion printing (3D plotting, direct ink writing), inkjet printing, 3D bioprinting, 4D printing and 4D bioprinting. It provides a comprehensive overview and discussion of the tailorability of material, mechanical, physical, chemical and biological properties of hydrogels to enable advanced hydrogel designs for 3D printing. The range of hydrogel-forming polymers covered encompasses biopolymers, synthetic polymers, polymer blends, nanocomposites, functional polymers, and cell-laden systems. The representative biomedical applications selected demonstrate how hydrogel-based 3D printing is being exploited in tissue engineering, regenerative medicine, cancer research, in vitro disease modeling, high-throughput drug screening, surgical preparation, soft robotics and flexible wearable electronics. Incomparable by thermoplastics, thermosets, ceramics and metals, hydrogel-based 3D printing is playing a pivotal role in the design and creation of advanced functional (bio)systems in a customizable way. An outlook on future directions of hydrogel-based 3D printing is presented.

3D printing of hydrogels: Rational design strategies and emerging biomedical applications

Crosslinked ionic polysaccharides for stimuli-sensitive drug delivery.

Sodium alginate/graphene oxide composite films with enhanced thermal and mechanical properties

The rapid development of modern industry and excessive consumption of petroleum-based polymers have triggered a double crisis presenting a shortage of nonrenewable resources and environmental pollution However, this has provided an opportunity to stimulate researchers to harness native biobased materials for novel advanced materials and applications Nanocellulose-based aerogels, using abundant and sustainable cellulose as raw material, present a third-generation of aerogels that combine traditional aerogels with high porosity and large specific surface area, as well as the excellent properties of cellulose itself Currently, nanocellulose aerogels provide a highly attention-catching platform for a wide range of functional applications in various fields, eg, adsorption, separation, energy storage, thermal insulation, electromagnetic interference shielding, and biomedical applications Here, the preparation methods, modification strategies, composite fabrications, and further applications of nanocellulose aerogels are summarized, with additional discussions regarding the prospects and potential challenges in future development

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202005569

Recent Progress on Nanocellulose Aerogels: Preparation, Modification, Composite Fabrication, Applications

pH-sensitive sodium alginate/poly(vinyl alcohol) hydrogel beads prepared by combined Ca2+ crosslinking and freeze-thawing cycles for controlled release of diclofenac sodium.

Xun Li

Papers

pH-sensitive sodium alginate/poly(vinyl alcohol) hydrogel beads prepared by combined Ca2+ crosslinking and freeze-thawing cycles for controlled release of diclofenac sodium.