Personalized wound dressings provide enhanced healing for different wound types; however multicomponent wound dressings with discretely controllable delivery of different biologically active agents are yet to be developed. Here we report 3D-printed multicomponent biocomposite hydrogel wound dressings that have been selectively loaded with small molecules, metal nanoparticles, and proteins for independently controlled release at the wound site. Hydrogel wound dressings carrying antibacterial silver nanoparticles and vascular endothelial growth factor with predetermined release profiles were utilized to study the physiological response of the wound in a mouse model. Compared to controls, the application of dressings resulted in improvement in granulation tissue formation and differential levels of vascular density, dependent on the release profile of the growth factor. Our study demonstrates the versatility of the 3D-printed hydrogel dressings that can yield varied physiological responses in vivo and can further be adapted for personalized treatment of various wound types.

In the search for new building blocks of nanofibrillar hydrogels, cellulose nanocrystals (CNCs) have attracted great interest because of their sustainability, biocompatibility, ease of surface functionalization, and mechanical strength. Making these hydrogels fluorescent extends the range of their applications in tissue engineering, bioimaging, and biosensing. We report the preparation and properties of a multifunctional hydrogel formed by CNCs and graphene quantum dots (GQDs). We show that although CNCs and GQDs are both negatively charged, hydrogen bonding and hydrophobic interactions overcome the electrostatic repulsion between these nanoparticles and yield a physically cross-linked hydrogel with tunable mechanical properties. Owing to their shear-thinning behavior, the CNC-GQD hydrogels were used as an injectable material in 3D printing. The hydrogels were fluorescent and had an anisotropic nanofibrillar structure. The combination of these advantageous properties makes this hybrid hydrogel a promising material and fosters the development of new manufacturing methods such as 3D printing.

We report a nanocolloidal hydrogel that combines the advantages of molecular hydrogels and nanoparticle-based scavengers of heavy metal ions. The hydrogel was formed by the chemical cross-linking of cellulose nanocrystals and graphene quantum dots. Over a range of hydrogel compositions, its structure was changed from lamellar to nanofibrillar, thus enabling the control of hydrogel permeability. Using a microfluidic approach, we generated nanocolloidal microgels and explored their scavenging capacity for Hg, Cu, Ni, and Ag ions. Due to the large surface area and abundance of ion-coordinating sites on the surface of nanoparticle building blocks, the microgels exhibited a high ion-sequestration capacity. The microgels were recyclable and were used in several ion scavenging cycles. These features, in addition to the sustainable nature of the nanoparticles, make this nanocolloidal hydrogel a promising ion-scavenging material.

Compositional and structural patterns play a crucial role in the function of many biological tissues. In the present work, for nanofibrillar hydrogels formed by chemically cross-linked cellulose nanocrystals (CNC) and gelatin, we report a microextrusion-based 3D printing method to generate structurally anisotropic hydrogel sheets with CNCs aligned in the direction of extrusion. We prepared hydrogels with a uniform composition, as well as hydrogels with two different types of compositional gradients. In the first type of gradient hydrogel, the composition of the sheet varied parallel to the direction of CNC alignment. In the second hydrogel type, the composition of the sheet changed orthogonally to the direction of CNC alignment. The hydrogels exhibited gradients in structure, mechanical properties, and permeability, all governed by the compositional patterns, as well as cytocompatibility. These hydrogels have promising applications for both fundamental research and for tissue engineering and regenerative medicine.

Polymer hydrogels exhibit actuation properties that result in reversible shape transformations and have promising applications in soft robotics, drug delivery systems, sensors, and microfluidic devices. Actuation occurs due to differential hydrogel swelling and is generally achieved by modulating hydrogel composition. Here a different approach to hydrogel actuation that originates solely from its structural anisotropy is reported. For 3D-printed single-layer hydrogels formed by cellulose nanocrystals (CNCs) and gelatin methacryloyl it is shown that shear-induced orientation of CNCs results in anisotropic mechanical and swelling properties of the hydrogel. Upon swelling in water, planar hydrogels acquire multiple complex 3D shapes that are achieved by i) varying CNC orientation with respect to the shape on the hydrogel sheet and ii) patterning the hydrogel with the regions of shearmediated and random CNC orientation. This study shows the capability to generate multiple shapes from the same hydrogel actuator based on the degree of its structural anisotropy. In addition, it introduces a biocompatible nanocolloidal ink with shear-thinning and self-healing properties for additive manufacturing of hydrogel actuators.