An amino acid-based gelator for injectable and multi-responsive hydrogel

Nonionic Water-Soluble Oligo(ethylene glycol)-Modified Polypeptides with a β-Sheet Conformation

The secondary structures of polypeptides, such as an α-helix and a β-sheet, often impart specific properties and functions, making the regulation of their secondary structures of great significance. Particularly, water-soluble polypeptides bearing a β-sheet conformation are rare and challenging to achieve. Here, a series of oligo(ethylene glycol)-modified lysine N-carboxylic anhydrides (EGmK-NCA, where m = 1-3) and the corresponding polymers EGmKn are synthesized, with urethane bonds as the linker between the side-chain EG and lysine. The secondary structure of EGmKn is delicately regulated by both m and n, the length (number of repeating units) of EG and the degree of polymerization (DP), respectively. Among them, EG2Kn adopts a β-sheet conformation with good water solubility at an appropriate DP and forms physically cross-linked hydrogels at a concentration as low as 1 wt %. The secondary structures of EG1Kn can be tuned by DP, exhibiting either a β-sheet or an α-helix, whereas EG3Kn appears to a adopt pure and stable α-helix with no dependence on DP. Compared to previous works reporting EG-modified lysine-derived polypeptides bearing exclusively an α-helix conformation, this work highlights the important and unexpected role of the urethane connecting unit and provides useful case studies for understanding the secondary structure of polypeptides.

Gelatin - glucosamine hydrochloride/crosslinked-Cyclodextrin Metal-organic frameworks @IBU composite hydrogel long-term sustained drug delivery system for osteoarthritis treatment

Osteoarthritis is a disease of articular cartilage degradation and inflammation of the joint capsule. Combining anti-inflammatory therapy with nutritional supplement is an effective means for the treatment of osteoarthritis. In this study, we prepared gelatin (Gel) - glucosamine hydrochloride (GH) mixed crosslinked-cyclodextrin metal-organic material (G-GH/CL-CD-MOF) composite hydrogel. Polyethylene glycol diglycidyl ether (PEGDE) was the crosslinking agent of GH and Gel to solve the problem of poor mechanical properties and water solubility at 37 ℃. CL-CD-MOF was fabricated through a simple one-step chemical reaction to crosslink the hydrophilic hydroxyl groups in CD-MOF with diphenyl carbonate (DPC). Electron microscopy and X-ray diffraction analysis of CL-CD-MOF showed perfect porous morphology with a chaotic internal structure. CL-CD-MOF@IBU was prepared by immersing CL-CD-MOF in high-concentration ibuprofen (IBU) solution. CL-CD-MOF@IBU was uniformly dispersed in Gel and GH mixed solution to prepare G-GH/CL-CD-MOF@IBU composite hydrogel long-term sustained drug delivery system. The compression curve of G-GH/CL-CD-MOF composite hydrogel showed a non-linear elastic behavior. The cyclic loading-unloading compression showed that the shape of the G-GH/CL-CD-MOF composite hydrogel can be kept intact under 50% strain. On the day 14, the G-GH/CL-CD-MOF@IBU composite hydrogel was degraded by 87.1%, 61% of IBU was released. G-GH/CL-CD-MOF@IBU exhibited good biocompatibility during co-culture with MC3T3-E1 cells. Briefly, the certain mechanical properties, sustained drug release behavior, and good biocompatibility of G-GH/CL-CD-MOF@IBU composite hydrogel showed that it has potential application in osteoarthritis treatment of long-term sustained nutritional supplement and anti-inflammatory synchronously.

Super-Strong, Nonswellable, and Biocompatible Hydrogels Inspired by Human Tendons

Fabricating artificial materials that mimic the structures and properties of tendons is of great significance. Possessing a tensile stress of approximately 10.0 MPa and a water content of around 60%, human tendons exhibit excellent mechanical properties to support daily functions. In contrast to tendons, most synthetic hydrogels with similar water content typically exclude qualified strength, swelling resistance, and biocompatibility. Herein, a facile strategy based on poly(vinyl alcohol) (PVA) and tannic acid (TA) is demonstrated to tackle this problem via a combination of sequential steps including freezing-thawing PVA aqueous solutions to form crystalline regions, prestretching and air drying in confined conditions to induce anisotropic structures, soaking in TA solutions to form multiple hydrogen bondings between PVA and TA, and finally dialyzing against water for the removal of residual TA molecules and the rearrangements and homogenization of multiple hydrogen bonds. The obtained PVA hydrogels possess hierarchically anisotropic structures, where the alignment of PVA bundles promotes high modulus, while the hydrogen bonding between PVA and TA endows them with an energy dissipation mechanism. Benefitting from the synergy of material composition and structural engineering, the obtained hydrogel displays super-strong mechanics (a tensile stress of 19.3 MPa and a toughness of 32.1 MJ/m³), outperforming most tough hydrogels. Remarkably, this hydrogel demonstrates excellent swelling resistance. It barely expands after immersion in deionized water, phosphate-buffered saline (PBS), and SBF aqueous solutions for 7 days with the strength and volume nearly the same as their initial values. All of the features, combined with excellent cytocompatibility, make it an ideal material for biotechnological and biomedical applications.

Multi-stimuli-responsive hydrogels and their medical applications

This review highlights the medical applications of multi-stimuli-responsive hydrogels as self-healing hydrogels, antibacterial materials and drug-delivery systems.

Synthesis and self-assembly of photo-responsive polypeptoid-based copolymers containing azobenzene side chains

Photo-responsive polypeptoid-based copolymers containing azobenzene side chains have been well synthesized and they could self-assemble into tunable nanostructures with reversible light-switched behaviors.

A self-healing supramolecular hydrogel with temperature-responsive fluorescence based on an AIE luminogen

In this work, an AIE luminogen-based hydrogel with temperature-responsive fluorescence was designed and synthesized. The polymeric hydrogel consisted of a supramolecular network through coordination and ionic interactions. When the temperature was decreased, due to the motion restriction of the polyacrylic acid macromolecular segments and the enhancement in ionic interaction, the hydrogel exhibited a blue-shift in the fluorescence emission peak and increase in the fluorescence intensity, resulting in the visualization of fluorescence changes. The hydrogel network benefitted from non-covalent crosslinking and thus possessed self-healing properties at room temperature with good toughness and resiliency. Therefore, this fluorescent supramolecular hydrogel might be used as a temperature-responsive material.

A supramolecular hydrogel was synthesized by using tetra(4-(pyridin-4-yl)phenyl)ethylene (TPPE) as AIE luminogen. The gel not only featured self-healing performance, but also exhibited the temperature-responsive fluorescence with thermochromism.

Synthesis of modifiable photo-responsive polypeptides bearing allyloxyazobenzene side-chains

A photo-responsive and modifiable polypeptide with stable helical conformation was synthesized. The self-assembly and liquid crystalline phase structure were subsequently studied.

In situ fabrication of a composite hydrogel with tunable mechanical properties for cartilage tissue engineering

A composite hydrogel with tunable mechanical properties has been fabricated and characterized in this study.

Encapsulation of Curcumin Nanoparticles with MMP9-Responsive and Thermos-Sensitive Hydrogel Improves Diabetic Wound Healing

Impaired wound healing in diabetics usually leads to life-threatening complications. To develop a system for fastening skin wound healing efficiently and safely in diabetics, thermos-sensitive hydrogel containing the nanodrug, loaded in the form of gelatin microspheres (GMs), was designed to deliver curcumin (Cur) as a therapeutic drug. Cur is a naturally existing polyphenolic compound with a broad range of biological functions useful for potential therapies. Because Cur molecule has weakness in both bioavailability and in vivo stability, delivery of Cur requires assistance from other molecules to act as carrier vehicles in a sustained manner for therapeutic use. At first, self-assembly of Cur nanoparticles (CNPs) was done to improve bioavailability. The CNPs were further enclosed into GMs for responding to the matrix metalloproteinases (MMPs) that usually overexpress at diabetic nonhealing wound sites. The GMs containing CNPs were loaded into the thermos-sensitive hydrogel and were finally proved for the capacity of specially induced drug release at the wound bed, which promoted the efficacy in healing the standardized skin wounds in streptozotocin-induced diabetic mice. Our results indicated that the successfully developed CNP delivery system had the capacity to significantly promote skin wound healing, which suggested that it could have the potential to become a wound dressing with the properties of antioxidants and promotions of cell migration.