Fabrication of Collagen-Hyaluronic Acid Cryogels by Directional Freezing Mimicking Cartilage Arcade-like Structure.

The internal architecture of tissue-like constructs is fundamental to their structural and biological functions. Here, we introduce a simple and robust method to fabricate cryogels based on derivatized extracellular matrix (ECM) macromolecules with porosity arranged according to the typical Benninghoff zonal architecture of articular cartilage. To obtain this arcade-like structure, the technique used the growth of ice crystals from copper pins at cryogenic temperatures. The directional cryogel formation enabled the organized growth of ice crystals over a large distance (>4 mm). The compositional properties were achieved by forming double networks (DNs) of hyaluronic acid and collagen derivatives (MeHA and CollGTA, respectively), which also served to improve the mechanical properties of the otherwise weak collagen scaffolds. Compositionally biomimetic and more resilient MeHA-CollGTA DNs (Young's modulus ≈ 200 kilopascals) were therefore produced. The technique presented expands the fabrication methods available for providing ECM macromolecules with architectural elements mimicking cartilage complexity.

Double trouble for viruses: a hydrogel nanocomposite catches the influenza virus while shrinking and changing color.

We report a virus responsive hydrogel with a dual response. The method utilizes the optical properties of gold nanoparticles (AuNPs) and the high swelling capacity of polyol-based hydrogels to form a nanocomposite of AuNPs and polyols that produces both color changes and shrinkage in the presence of Influenza A virus particles.

Matrix Stiffness Regulates Chemosensitivity, Stemness Characteristics, and Autophagy in Breast Cancer Cells.

The biomechanical environment of natural or synthetic extracellular matrices (ECMs) is identified to play a considerable role in embryonic development in stem cell fate and also in cancer development and fibrotic diseases. However, rare evidence shows the impact of biomechanical signals such as ECM stiffness on cancer cell stemness and autophagy, which makes huge contributions to cancer and many developmental and physiological processes. Furthermore, the influence and mechanism of ECM stiffness on autophagy in cancer cells remains unclear. Herein, we employed fibronectin-coated polyacrylamide hydrogels as the substrates for culturing breast cancer cells. We found that a soft environment was beneficial for the maintenance of cancer stem cell (CSC) population in breast cancer cells, which likely led to aggravated chemoresistance. Conversely, nutritional deprivation-induced autophagy was elevated along with increasing matrix stiffness. In addition, we found that though the central regulator of mechanotransduction, the yes-associated protein, YAP, was beneficial for autophagy activation, unexpectedly, it was not the main cause of rigid substrate promoting autophagy. In contrast, the YAP was crucial for a compliant environment for maintaining breast cancer stem cells and promoting chemotherapeutic resistance. We also found that the Rho-ROCK-ERK signal pathway and actin cytoskeleton were essential for the regulation of autophagy by matrix stiffness. Taken together, our study showed the important influence of ECM stiffness on stemness and autophagy in breast cancer cells and revealed the possible signal pathway involved in the mechanotransduction in autophagy activation, which provides significant implications for the study of cancer progression and design of hydrogels for tissue engineering in clinical therapy.

Nonwoven Carboxylated Agarose-Based Fiber Meshes with Antimicrobial Properties.

Hydrogel forming polysaccharides, such as the seaweed derived agarose, are well suited for wound dressing applications as they have excellent cell and soft tissue compatibility. For wound dressings, fibrous structure is desirable as the high surface area can favor adsorption of wound exudate and promote drug delivery. Although electrospinning offers a straightforward means to produce nonwoven fibrous polymeric structures, processing agarose and its derivatives into fibers through electrospinning is challenging as it has limited solubility in solvents other than water. In this study we describe the processing of carboxylated agarose (CA) fibers with antibacterial properties by electrospinning from a solution of the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([Bmim]+Cl-) possessing antimicrobial properties. The extent of carboxylation was found to impact fiber diameter, mesh elastic modulus, fiber swelling, and the loading and release of IL. IL-bearing CA fibers inhibited the growth of Staphylococcus aureus and Pseudomonas aeruginosa, bacteria commonly found in wound exudate. In sum, nonwoven CA fibers processed from IL are promising as biomaterials for wound dressing applications.