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1. Layered supramolecular hydrogels from thioglycosides

   https://doi.org/10.1039/d2tb00037g  

   Wang, Yu-Cheng; Kegel, Laurel L.; Knoff, David S.; Deodhar, Bhushan S.; Astashkin, Andrei V.; Kim, Minkyu; Pemberton, Jeanne E. (April 2022, Journal of Materials Chemistry B)

   Low molecular weight hydrogels are made of small molecules that aggregate via noncovalent interactions. Here, comprehensive characterization of the physical and chemical properties of hydrogels made from thioglycolipids of the disaccharides lactose and cellobiose with simple alkyl chains is reported. While thiolactoside hydrogels are robust, thiocellobioside gels are metastable, precipitating over time into fibrous crystals that can be entangled to create pseudo-hydrogels. Rheology confirms the viscoelastic solid nature of these hydrogels with storage moduli ranging from 10–600 kPa. Additionally, thiolactoside hydrogels are thixotropic which is a desirable property for many potential applications. Freeze-fracture electron microscopy of xerogels shows layers of stacked sheets that are entangled into networks. These structures are unique compared to the fibers or ribbons typically reported for hydrogels. Differential scanning calorimetry provides gel-to-liquid phase transition temperatures ranging from 30 to 80 °C. Prodan fluorescence spectroscopy allows assignment of phase transitions in the gels and other lyotropic phases of high concentration samples. Phase diagrams are estimated for all hydrogels at 1–10 wt% from 5 to ≥ 80 °C. These hydrogels represent a series of interesting materials with unique properties that make them attractive for numerous potential applications. 

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2. Engineering Adhesive Hydrogels for Hemostasis and Vascular Repair

   https://doi.org/10.3390/polym17070959  

   Jeon, Juya; Subramani, Shri Venkatesh; Lee, Kok Zhi; Elizondo-Benedetto, Santiago; Zayed, Mohamed Adel; Zhang, Fuzhong (April 2025, Polymers)

   Adhesive hydrogels with tunable mechanical properties and strong adhesion to wet, dynamic tissues have emerged as promising materials for tissue repair, with potential applications in wound closure, hemorrhage control, and surgical adhesives. This review highlights the key design principles, material classifications, and recent advances in adhesive hydrogels designed for vascular repair. The limitations of existing adhesive hydrogels, including insufficient mechanical durability, suboptimal biocompatibility, and challenges in targeted delivery, are critically evaluated. Furthermore, innovative strategies—such as incorporating self-healing capabilities, developing stimuli-responsive systems, integrating functional nanocomposites, and employing advanced fabrication techniques like 3D bioprinting—are discussed to enhance adhesion, mechanical stability, and vascular tissue regeneration. While significant progress has been made, further research and optimization are necessary to advance these materials toward clinical translation, offering a versatile and minimally invasive alternative to traditional vascular repair techniques. 

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3. Accurate flow in augmented networks (AFAN): an approach to generating three-dimensional biomimetic microfluidic networks with controlled flow

   https://doi.org/10.1039/C8AY01798K  

   Guo, Jiaming; Keller, Keely A.; Govyadinov, Pavel; Ruchhoeft, Paul; Slater, John H.; Mayerich, David (January 2019, Analytical Methods)

   In vivo , microvasculature provides oxygen, nutrients, and soluble factors necessary for cell survival and function. The highly tortuous, densely-packed, and interconnected three-dimensional (3D) architecture of microvasculature ensures that cells receive these crucial components. The ability to duplicate microvascular architecture in tissue-engineered models could provide a means to generate large-volume constructs as well as advanced microphysiological systems. Similarly, the ability to induce realistic flow in engineered microvasculature is crucial to recapitulating in vivo -like flow and transport. Advanced biofabrication techniques are capable of generating 3D, biomimetic microfluidic networks in hydrogels, however, these models can exhibit systemic aberrations in flow due to incorrect boundary conditions. To overcome this problem, we developed an automated method for generating synthetic augmented channels that induce the desired flow properties within three-dimensional microfluidic networks. These augmented inlets and outlets enforce the appropriate boundary conditions for achieving specified flow properties and create a three-dimensional output useful for image-guided fabrication techniques to create biomimetic microvascular networks. 

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4. Elastin‐like protein hydrogels with controllable stress relaxation rate and stiffness modulate endothelial cell function

   https://doi.org/10.1002/jbm.a.37520  

   Shayan, Mahdis; Huang, Michelle S.; Navarro, Renato; Chiang, Gladys; Hu, Caroline; Oropeza, Beu P.; Johansson, Patrik K.; Suhar, Riley A.; Foster, Abbygail A.; LeSavage, Bauer L.; et al (March 2023, Journal of Biomedical Materials Research Part A)

   Abstract Mechanical cues from the extracellular matrix (ECM) regulate vascular endothelial cell (EC) morphology and function. Since naturally derived ECMs are viscoelastic, cells respond to viscoelastic matrices that exhibit stress relaxation, in which a cell‐applied force results in matrix remodeling. To decouple the effects of stress relaxation rate from substrate stiffness on EC behavior, we engineered elastin‐like protein (ELP) hydrogels in which dynamic covalent chemistry (DCC) was used to crosslink hydrazine‐modified ELP (ELP‐HYD) and aldehyde/benzaldehyde‐modified polyethylene glycol (PEG‐ALD/PEG‐BZA). The reversible DCC crosslinks in ELP‐PEG hydrogels create a matrix with independently tunable stiffness and stress relaxation rate. By formulating fast‐relaxing or slow‐relaxing hydrogels with a range of stiffness (500–3300 Pa), we examined the effect of these mechanical properties on EC spreading, proliferation, vascular sprouting, and vascularization. The results show that both stress relaxation rate and stiffness modulate endothelial spreading on two‐dimensional substrates, on which ECs exhibited greater cell spreading on fast‐relaxing hydrogels up through 3 days, compared with slow‐relaxing hydrogels at the same stiffness. In three‐dimensional hydrogels encapsulating ECs and fibroblasts in coculture, the fast‐relaxing, low‐stiffness hydrogels produced the widest vascular sprouts, a measure of vessel maturity. This finding was validated in a murine subcutaneous implantation model, in which the fast‐relaxing, low‐stiffness hydrogel produced significantly more vascularization compared with the slow‐relaxing, low‐stiffness hydrogel. Together, these results suggest that both stress relaxation rate and stiffness modulate endothelial behavior, and that the fast‐relaxing, low‐stiffness hydrogels supported the highest capillary density in vivo. 

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5. Engineering biomaterials by inkjet printing of hydrogels with functional particulates

   https://doi.org/10.1007/s44258-024-00024-4  

   Cheng, Cih; Williamson, Eric_J; Chiu, George_T-C; Han, Bumsoo (July 2024, Med-X)

   Abstract Hydrogels with particulates, including proteins, drugs, nanoparticles, and cells, enable the development of new and innovative biomaterials. Precise control of the spatial distribution of these particulates is crucial to produce advanced biomaterials. Thus, there is a high demand for manufacturing methods for particle-laden hydrogels. In this context, 3D printing of hydrogels is emerging as a promising method to create numerous innovative biomaterials. Among the 3D printing methods, inkjet printing, so-called drop-on-demand (DOD) printing, stands out for its ability to construct biomaterials with superior spatial resolutions. However, its printing processes are still designed by trial and error due to a limited understanding of the ink behavior during the printing processes. This review discusses the current understanding of transport processes and hydrogel behaviors during inkjet printing for particulate-laden hydrogels. Specifically, we review the transport processes of water and particulates within hydrogel during ink formulation, jetting, and curing. Additionally, we examine current inkjet printing applications in fabricating engineered tissues, drug delivery devices, and advanced bioelectronics components. Finally, the challenges and opportunities for next-generation inkjet printing are also discussed. Graphical Abstract 

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