ROS-activatable nanocomposites for CT imaging tracking and antioxidative protection of mesenchymal stem cells in idiopathic pulmonary fibrosis therapy.

Mesenchymal stem cell (MSC) transplantation is emerging as a promising approach in the treatment of idiopathic pulmonary fibrosis (IPF), while it is still impeded by several challenges, including unsatisfactory treatment outcomes due to the poor survival of transplanted MSCs, and the lack of non-invasive and long-term imaging modality for tracking the behavior of MSCs. Herein, copper-based nanozyme (CuxO NPs) and gold nanoparticles (Au NPs) were encapsulated in oxidation-sensitive dextran (Oxi-Dex), a dextran derivative with reactive oxygen species (ROS)-responsiveness, forming a kind of novel nanocomposites (assigned as RSNPs) to act as ROS scavengers and computer tomography (CT) imaging tracers. After being internalized by MSCs, RSNPs enabled continuous CT imaging tracking of the transplanted MSCs for 21 days in IPF treatment, obtaining the location and distribution of the transplanted MSCs. Once MSCs were attacked by oxidative stress, the intracellular RSNPs could activate ROS clearance on demand by releasing CuxO NPs, thereby enhancing the therapeutic efficacy against IPF by improving cell survival. Taken together, a novel multifunctional RSNP was fabricated to label MSCs for CT imaging tracking and clearing superfluous ROS, presenting a promising high-efficient IPF therapy.

Inhibited astrocytic differentiation in neural stem cell-laden 3D bioprinted conductive composite hydrogel scaffolds for repair of spinal cord injury.

The emergence of three-dimensional (3D) bioprinting technology has attracted ever-increasing attention in engineered tissue fabrication for stem cell-based tissue repair. However, the in vivo performance of transplanted stem cells in the tissue engineering scaffolds is still a major concern for regenerative medicine researches. Especially for neural stem cell (NSC) transplantation, the uncontrollable differentiation of the NSCs in host often leads to a poor therapeutic effect in nerve tissue repair, such as spinal cord injury (SCI) repair. To address this issue, we have fabricated a conductive composite hydrogel (CCH) scaffold loading with NSCs by 3D bioprinting, for delivering the NSCs to injured spinal cord and repairing the propriospinal nerve circuit. In our strategy, a novel conductive polymer (PEDOT:CSMA,TA) was synthesized and introduced into a photocrosslinkable gelatin/polyethylene glycol physical-gel matrix, thereby forming a composite bioink with well shear-thinning and self-healing properties. The composite bioink we prepared was then printed into the NSC-laden CCH scaffold with high shape fidelity and similar physicochemical properties to native spinal cord tissues. The NSCs encapsulated in the bioprinted CCH scaffold extended their neurites to form superior physical contact with the neighboring cells as well as the electroconductive matrix, and maintained a predominant in vivo neuronal differentiation, accompanying with few astrocytic production in the lesion area after transplantation into the SCI sites. As a result, the removal of glial scar tissues and the regeneration of well-developed nerve fibres sequentially happened, which not only facilitated nerve tissue development, but also accelerated locomotor function recovery in the SCI rats. By exploring the application of conductive biomaterials in stem cell-based SCI therapy, this work represents a feasible, new approach to precisely construct tissue engineering scaffolds for stem cell-based therapy in traumatic SCI and other nervous system diseases.

Au-Pt nanozyme-based multifunctional hydrogel dressing for diabetic wound healing.

Diabetic chronic wound healing is a critical clinical challenge due to the particularity of wound microenvironment, including hyperglycemia, excessive oxidative stress, hypoxia, and bacterial infection. Herein, we developed a multifunctional self-healing hydrogel dressing (defined as OHCN) to regulate the complex microenvironment of wound for accelerative diabetic wound repair. The OHCN hydrogel dressing was constructed by integrating Au-Pt alloy nanoparticles into a hydrogel (OHC) that formed through Schiff-base reaction between oxidized hyaluronic acid (OHA) and carboxymethyl chitosan (CMCS). The dynamic cross-linking of OHA and antibacterial CMCS imparted the OHCN hydrogel dressing with excellent antibacterial and self-healing properties. Meanwhile, Au-Pt alloy nanoparticles endowed the OHCN hydrogel dressing with the functions of lowering blood glucose, alleviating oxidative damage, and providing O2 by simulating glucose oxidase and catalase. Through a synergistic combination of OHC hydrogel and Au-Pt alloy nanoparticles, the resulted OHCN hydrogel dressing significantly ameliorated the pathological microenvironment and accelerated the healing rate of diabetic wound. The proposed nanozyme-decorated multifunctional hydrogel offers an efficient strategy for the improved management of diabetic chronic wound.

Release of O-GlcNAc transferase inhibitor promotes neuronal differentiation of neural stem cells in 3D bioprinted supramolecular hydrogel scaffold for spinal cord injury repair.

Precise fabrication of biomimetic three-dimensional (3D) structure and effective neuronal differentiation under the pathological environment are the key to neural stem cell (NSC)-based spinal cord injury (SCI) therapy. In this study, we have developed a spinal cord-like bioprinted scaffold loading with OSMI-4, a small molecule O-GlcNAc transferase (OGT) inhibitor, to induce and guide the neuron differentiation of NSCs for efficient SCI repair. To achieve this, we developed a supramolecular bioink (SM bioink) consisting of methacrylated gelatin and acrylated ß-cyclodextrins to load NSCs and OSMI-4. This bioink showed fast gelation and stable mechanical properties, facilitating bioprinting of functional neural scaffolds. Moreover, the weak host-guest cross-linking of the SM scaffolds significantly improved the cell-matrix interaction for the infiltration and migration of NSCs. What's more, the sustained delivery of OSMI-4 remarkably enhanced the intrinsic neuronal differentiation of the encapsulated NSCs in vitro by inhibiting Notch signaling pathway. In vivo experiment further revealed that the functional bioprinted scaffolds promoted the neuronal regeneration and axonal growth, leading to significant locomotor recovery of the SCI model rats. Together, the NSC-laden bioprinted SM scaffolds in combination with sustained release of the therapeutic agent OSMI-4 largely induced neuronal differentiation of NSCs and thus leading to efficient SCI repair. STATEMENT OF SIGNIFICANCE: Efficient neuronal differentiation of neural stem cells (NSCs) under the complex pathological microenvironment of spinal cord injury (SCI) is a major challenge of neural regeneration. By the use of a supramolecular bioink, we bioprinted a spinal cord-like scaffold loaded with NSCs and a small molecule drug OSMI-4 to significantly induce neuronal differentiation of NSCs for efficient SCI repair in vivo. The scaffolds with spinal cord-like structure can support the interaction and neuronal differentiation of NSCs by providing a dynamic matrix and a source of molecular release of OSMI-4. The influences of OSMI-4 on NSCs and its molecular mechanism were investigated for the first time in this study. Altogether, three-dimensional bioprinting fabrication of NSC- and small molecule drug-laden biomimetic construct may represent a promising therapeutic strategy for SCI repair.

Development and Characterization of Complementary Polymer Network Bioinks for 3D Bioprinting of Soft Tissue Constructs.

The development of 3D bioprinting has been hindered by a narrow "biofabrication window" with a limited variety of feasible bioinks which are compatible with both high printability and well cytocompatibility. Herein, a generalizable strategy using complementary polymer network (CPN) bioinks is developed in the current study, to address the conflict between the printability and cytocompatibility of bioinks in extrusion 3D bioprinting, especially for the manufacture of soft tissue constructs. In this strategy, CPN bioinks are formed though mixing two interpenetrated polymer networks, one of which is a photocrosslinkable polymer network, and the other is a dynamic polymer network crosslinked by reversible covalent linkage, thereby endowed with well reversible thixotropy. Compatible with well printability, shape fidelity, and cytocompatibility, the utilization of CPN bioinks provides a viable solution for extrusion 3D bioprinting of photocrosslinkable biomaterials at a low concentration, thus suitable for soft tissue construct fabrication. Briefly, this study is testified to be a successful attempt to extend the bioink diversity within the "biofabrication window," and offers a novel insight into designing more feasible bioinks based on their special rheological properties, for further tissue engineering and biomedicine application.

Neural stem cell-laden 3D bioprinting of polyphenol-doped electroconductive hydrogel scaffolds for enhanced neuronal differentiation.

The development of three-dimensional (3D) bioprinting technology opens a door for constructing bionic nerve tissue scaffolds on demand for nerve injury repair. However, the electrical insulation of the current nerve tissue scaffolds fabricated by 3D bioprinting hinders the bioelectrical signal transmission between cells, limiting the therapeutic effect in nerve tissue repair. To address this issue, we have developed a neural stem cell (NSC)-laden 3D bioprinted electroconductive hydrogel (ECH) scaffold, composed of modified poly(3,4-ethylenedioxythiophene) (PEDOT), gelatin methacrylate/polyethylene glycol diacrylate hydrogel matrix, and NSCs, to promote the electron propagation in the scaffold for enhanced nerve regeneration. In our strategy, PEDOT is modified by doping with chondroitin sulfate and tannic acid (TA) to improve its water-solubility and electric property. With moderate mechanical strength and good electroconductivity, the 3D ECH scaffold provides a benign conductive microenvironment for the adhesion, growth, and proliferation of the encapsulated NSCs. Clearly, in the 3D ECH scaffolds, the NSCs not only maintain high cell viability (>90%) after bioprinting, but also tend to differentiate into neurons with extended neurites. This study testifies for the first time the effect of polyphenol structure belonging to TA on neuronal differentiation of NSCs, and offers a new insight into designing electroconductive biomaterials to induce neuronal regeneration for nerve injury repair and neurodegenerative disease therapy.

Recent Development of Conductive Hydrogels for Tissue Engineering: Review and Perspective.

In recent years, tissue engineering techniques have been rapidly developed and offer a new therapeutic approach to organ or tissue damage repair. However, most of tissue engineering scaffolds are nonconductive and cannot establish effective electrical coupling with tissue for the electroactive tissues. Electroconductive hydrogels (ECHs) have received increasing attention in tissue engineering owing to their electroconductivity, biocompatibility, and high water content. In vitro, ECHs can not only promote the communication of electrical signals between cells, but also mediate the adhesion, proliferation, migration, and differentiation of different kinds of cells. In vivo, ECHs can transmit the electric signal to electroactive tissues and activate bioelectrical signaling pathways to promote tissue repair. As a result, implanting ECHs into damaged tissues can effectively reconstruct physiological functions related to electrical conduction. In this review, an overview about the classifications and the fabrication methods of ECHs is first presented. And then, the applications of ECHs in tissue engineering, including cardiac, nerve, skin, and skeletal muscle tissue, are highlighted. At last, some rational guidelines for designing ECHs toward clinical applications are provided.

HBC-nanofiber hydrogel scaffolds with 3D printed internal microchannels for enhanced cartilage differentiation.

Articular cartilage injuries are a major orthopedic problem. Cartilage repair is a long-standing challenge due to the limited self-regenerative capability of cartilage. Tissue engineering offers a new and effective approach to cartilage repair. We report herein the fabrication of 3D scaffolds that mimic the native structure of cartilage, by first preparing poly(lactic-co-glycolic acid) (PLGA) electrospun nanofiber incorporated hydroxybutyl chitosan (HBC) hydrogels (HBC-NF hydrogels) and then injecting the hydrogels into a 3D printed poly(ε-caprolactone) (PCL) framework with internal microchannels for improved mechanical support and substance exchange. The thus-obtained HBC-NF hydrogels exhibited outstanding gelation properties with a gelling time of no more than 15 s at 37 °C. With the incorporation of the nanofibers, human mesenchymal stem cells (hMSCs) showed good proliferation in the HBC-NF hydrogels. The relative gene expression levels for mesenchymal condensation and matrix deposition significantly increased in the HBC-NF hydrogels due to the addition of the nanofibers, suggesting substantially enhanced cartilage differentiation. Furthermore, the injection of the HBC-NF hydrogels into the 3D printing PCL framework led to the formation of 3D scaffolds with significantly improved mechanical performance. More importantly, the construction of regulable internal microchannels for cell growth and the exchange of nutrients and waste products were achieved via co-printing of PCL and a sacrificial material, Pluronic F-127. The PCL reinforced HBC-NF hydrogel scaffolds with internal microchannels showed enhanced chondrogenesis and mechanical properties in vivo. In summary, the current work has demonstrated that PCL framework reinforced HBC-NF hydrogels with tunable internal microchannels provide an ideal biomimetic microenvironment for the growth and cartilage differentiation of hMSCs, therefore holding promise for potential applications in cartilage tissue engineering.