Mussel-inspired injectable hydrogel and its counterpart for actuating proliferation and neuronal differentiation of retinal progenitor cells

Incorporation of dumbbell-shaped and Y-shaped cross-linkers in adjustable pullulan/polydopamine hydrogels for selective adsorption of cationic dyes

Hydrogel adsorbents have attracted considerable attention due to their sludge minimization, good water permeability and renewable performance. Here, a promising strategy for the one-step preparation of pullulan/polydopamine hybird hydrogels (PPGels) was presented. Dumbbell-shaped cross-linker neopentyl glycol diglycidyl ether (NGDE, 2 arms) and Y-shaped cross-linker trimethylolpropane triglycidyl ether (TTE, 3 arms) were selected to study the relationship between cross-linker structure and hydrogel performances. The NGDE possessing less molecular repulsive force and higher reactivity demonstrated more effective cross-linking with the pullulan, which leaded to a decrease in pore size of the hydrogel. Meanwhile, the introduction of polydopamine significantly enhanced the adsorption ability and gave the resulting hybrid gel the specific selectivity toward cationic dyes (96 mg/g for crystal violet, 25.8 mg/g for methylene blue and barely not adsorption for azophloxine). Our data suggested that the electrostatic interaction played a vital role in the dye adsorption process, and the adsorption data could be explained by pseudo-second-order model and Langmuir isotherm model. Furthermore, the obtained PPGel could be easily separated after adsorption. This study describes the relationship between cross-linker structure and properties of pullulan/polydopamine hybrid gels, which provides a new strategy to create polysaccharide-based adsorbents for wastewater remediation.

Thiolated bone and tendon tissue particles covalently bound in hydrogels for in vivo calvarial bone regeneration

Bone regeneration of large cranial defects, potentially including traumatic brain injury (TBI) treatment, presents a major problem with non-crosslinking, clinically available products due to material migration outside the defect. Commercial products such as bone cements are permanent and thus not conducive to bone regeneration, and typical commercial bioactive materials for bone regeneration do not crosslink. Our previous work demonstrated that non-crosslinking materials may be prone to material migration following surgical placement, and the current study attempted to address these problems by introducing a new hydrogel system where tissue particles are themselves the crosslinker. Specifically, a pentenoate-modified hyaluronic acid (PHA) polymer was covalently linked to thiolated tissue particles of demineralized bone matrix (TDBM) or devitalized tendon (TDVT), thereby forming an interconnected hydrogel matrix for calvarial bone regeneration. All hydrogel precursor solutions exhibited sufficient yield stress for surgical placement and an adequate compressive modulus post-crosslinking. Critical-size calvarial defects were filled with a 4% PHA hydrogel containing 10 or 20% TDBM or TDVT, with the clinical product DBX^Ⓡ being employed as the standard of care control for the in vivo study. At 12 weeks, micro-computed tomography analysis demonstrated similar bone regeneration among the experimental groups, TDBM and TDVT, and the standard of care control DBX^Ⓡ. The group with 10% TDBM was therefore identified as an attractive material for potential calvarial defect repair, as it additionally exhibited a sufficient initial recovery after shearing (i.e., > 80% recovery). Future studies will focus on applying a hydrogel in a rat model for treatment of TBI. STATEMENT OF SIGNIFICANCE: Non-crosslinking materials may be prone to material migration from a calvarial bone defect following surgical placement, which is problematic for materials intended for bone regeneration. Unfortunately, typical crosslinking materials such as bone cements are permanent and thus not conducive to bone regeneration, and typical bioactive materials for bone regeneration such as tissue matrix are not crosslinked in commercial products. The current study addressed these problems by introducing a new biomaterial where tissue particles are themselves the crosslinker in a hydrogel system. The current study successfully demonstrated a new material based on pentenoate-modified hyaluronic acid with thiolated demineralized bone matrix that is capable of rapid crosslinking, with desirable paste-like rheology of the precursor material for surgical placement, and with bone regeneration comparable to a commercially available standard-of-care product. Such a material may hold promise for a single-surgery treatment of severe traumatic brain injury (TBI) following hemicraniectomy.

A super-stretchable, self-healing and injectable supramolecular hydrogel constructed by a host–guest crosslinker

Supramolecular hydrogels based on host–guest interactions have drawn considerable attention due to their unique properties and promising applications.

Sustained protein therapeutics enabled by self-healing nanocomposite hydrogels for non-invasive bone regeneration

The self-healing nanocomposite hydrogel for sustained release of BMP-2 to enhance bone regeneration.

In situ-forming, mechanically resilient hydrogels for cell delivery

Injectable, in situ-forming hydrogels can improve cell delivery in tissue engineering applications by facilitating minimally invasive delivery to irregular defect sites and improving cell retention and survival. Tissues targeted for cell delivery often undergo diverse mechanical loading including high stress, high strain, and repetitive loading conditions. This review focuses on the development of hydrogel systems that meet the requirements of mechanical resiliency, cytocompatibility, and injectability for such applications. First, we describe the most important design considerations for maintaining the viability and function of encapsulated cells, for reproducing the target tissue morphology, and for achieving degradation profiles that facilitate tissue replacement. Models describing the relationships between hydrogel structure and mechanical properties are described, focusing on design principles necessary for producing mechanically resilient hydrogels. The advantages and limitations of current strategies for preparing cytocompatible, injectable, and mechanically resilient hydrogels are reviewed, including double networks, nanocomposites, and high molecular weight amphiphilic copolymer networks. Finally, challenges and opportunities are outlined to guide future research in this developing field.

Enhanced proliferation and differentiation of retinal progenitor cells through a self-healing injectable hydrogel

Fabrication of self-healing injectable CS-Odex hydrogels via a dynamic Schiff-base linkage for RPC delivery.

In situ bone regeneration enabled by a biodegradable hybrid double-network hydrogel

The biodegradable hybrid double-network hydrogel for stem cell-enhanced bone regeneration.