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Granular hydrogels are a promising biomaterial for a wide range of biomedical applications, including tissue regeneration, drug/cell delivery, and 3D printing. These granular hydrogels are created by assembling microgels through the jamming process. However, current methods for interconnecting the microgels often limit their use due to the reliance on postprocessing for crosslinking through photoinitiated reactions or enzymatic catalysis. To address this limitation, we incorporated a thiol-functionalized thermo-responsive polymer into oxidized hyaluronic acid microgel assemblies. The rapid exchange rate of thiol-aldehyde dynamic covalent bonds allows the microgel assembly to be shear-thinning and self-healing, with the phase transition behavior of the thermo-responsive polymer serving as secondary crosslinking to stabilize the granular hydrogels network at body temperature. This two-stage crosslinking system provides excellent injectability and shape stability, while maintaining mechanical integrity. In addition, the aldehyde groups of the microgels act as covalent binding sites for sustained drug release. These granular hydrogels can be used as scaffolds for cell delivery and encapsulation, and can be 3D printed without the need for post-printing processing to maintain mechanical stability. Overall, our work introduces thermo-responsive granular hydrogels with promising potential for various biomedical applications., (© 2023 Wiley Periodicals LLC.)

Granular hydrogels have recently emerged as promising biomaterials for tissue engineering and 3D-printing applications, addressing the limitations of bulk hydrogels while exhibiting desirable properties such as injectability and high porosity. However, their structural stability can be improved with post-injection interparticle cross-linking. In this study, we developed granular hydrogels with interparticle cross-linking through reversible and dynamic covalent bonds. We fragmented photo-cross-linked bulk hydrogels to produce aldehyde or hydrazide-functionalized microgels using chondroitin sulfate. Mixing these microgels facilitated interparticle cross-linking through reversible hydrazone bonds, providing shear-thinning and self-healing properties for injectability and 3D printing. The resulting granular hydrogels displayed high mechanical stability without the need for secondary cross-linking. Furthermore, the porosity and sustained release of growth factors from these hydrogels synergistically enhanced cell recruitment. Our study highlights the potential of reversible interparticle cross-linking for designing injectable and 3D printable therapeutic delivery scaffolds using granular hydrogels. Overall, our study highlights the potential of reversible interparticle cross-linking to improve the structural stability of granular hydrogels, making them an effective biomaterial for use in tissue engineering and 3D-printing applications.

Two-dimensional (2D) nanomaterials are ultrathin, layered materials with a high surface-to-volume ratio that can deliver various therapeutics including small-molecule drugs, peptides, and large proteins. Their high surface area allows for high therapeutic loading and sustained therapeutic release over time. Some 2D nanomaterials respond to external stimuli, providing control over triggered or on-demand therapeutic release. 2D nanomaterials explored for biomedical applications include carbon-based (graphene), nanoclays, black phosphorous, layered double hydroxides, metal organic frameworks, covalent organic framework, 2D metal carbides and nitrides, transition metal dichalcogenides, transition metal oxides, polymer nanosheets, and hexagonal boron nitride. Most of these nanomaterials are biocompatible and degrade into nontoxic products, which is advantageous for therapeutic delivery systems. In this article, we will evaluate these nanomaterials for therapeutic delivery. We will highlight some of their unique physical and chemical characteristics, discuss their biological stability, and investigate their ability to deliver various therapeutics. Recent developments in 2D nanomaterials as drug delivery systems will also be discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

The Sun derives its energy from fusion reactions in which hydrogen is transformed into helium. Every time four protons are turned into a helium nucleus, two neutrinos are produced. These neutrinos take only two seconds to reach the surface of the Sun and another eight minutes or so to reach the Earth. Thus, neutrinos tell us what happened in the center of the Sun eight minutes ago. The Sun produces one-third as many neutrinos as predicted by the standard solar model of particle physics. The author's pioneering work proved that nothing was wrong with the experiments or the theory; something was "wrong" with the neutrinos, in the sense that they behave in ways beyond the standard model.

The argon radioactivities (37)Ar and (39)Ar were obtained by vacuum melting from interior and exterior portions of rock 10057 and from a portion of the fines from the bulk sample container. The release of argon and tritium as a function of the temperature was followed for the fine material. A comparison is made of the activities observed in the lunar samples with those expected from the spallation of iron, titanium, and calcium. From these data and the (38)Ar content, the cosmic ray exposure age of rock 10057 is deduced as 110 x 10(6) years.