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Objective·To construct a self-healing injectable hyaluronic acid (HA)-based hydrogel (HAPD-Cu) and investigate the effects of different copper ions on the properties of the hydrogel and its vasogenic efficacy to evaluate its feasibility for clinical wound healing.Methods·Bisphosphonated hyaluronic acid (HAPD) was prepared via a blue-light mediated thiol-ene click reaction between thiolated hyaluronic acid (HASH) and acrylated bisphosphonate (Ac-PD) in the presence of photoinitiator 2959. Then, HAPD was further interacted with Cu2+ through metal coordination to prepare HAPD-Cu hydrogels with different Cu2+ concentrations, i.e. HAPD-Cu1, HAPD-Cu2, HAPD-Cu3 and HAPD-Cu4. The molecular structures of HASH, Ac-PD, HAPD and HAPD-Cu were verified with 1HNMR and FTIR. Microscopic morphology of HAPD-Cu was observed under SEM. The shear-thinning and self-healing properties of HAPD-Cu were verified by rheometer. The Cu2+ release from HAPD-Cu was determined with ICP. Live-dead staining and CCK-8 assay were applied to evaluate the biocompatibility of HAPD-Cu. The in vitro vasculogenic activity of HAPD-Cu was determined by a tubule-forming assay with human umbilical vein vascular endothelial cells and the in vivo vasculogenic activity of HAPD-Cu was assessed by CD31 tissue staining. A rat wound defect model was established in vitro to evaluate its actual repair effect.Results·The preparation of the materials was demonstrated through chemical qualitative and quantitative analytical means. In vitro studies showed that all HAPD-Cu with a loose porous internal structure exhibited outstanding self-healing, injectability and degradability, with a one-week degradation cycle and abrupt release behavior, which can meet the needs of wound healing cycle. All HAPD-Cu showed good biocompatibility except HAPD-Cu4, due to its high Cu2+ concentrations. Moreover, its angiogenic effect in vitro or in vivo was enhanced with increasing Cu2+ concentrations within the permissible Cu2+ concentration range. In vitro wound model experiments also showed that the HAPD-Cu hydrogel significantly promoted wound healing compared with the control group.Conclusion·HAPD-Cu hydrogel constructed via the metal coordination shows excellent shape plasticity, allowing the filling of defective sites in a minimally invasive form, and the release of Cu2+ greatly facilitates the establishment of early vascular networks, with giant potential for use in the repair of clinically irregular wounds.

Objective·To investigate the effect of hydrogel stiffness on nucleus pulposus cell phenotype and its function in repairing intervertebral disc degeneration in rats.Methods·Methacrylate gelatin (GelMA) hydrogels with different concentrations were constructed. The stiffness of the hydrogels was investigated by using rheological analysis and uniaxial compression test. The microstructure and morphology of the hydrogels were observed by scanning electron microscopy (SEM). Nucleus pulposus cells with normal phenotype were inoculated on the surface of GelMA hydrogels. The biocompatibility of the hydrogel was evaluated by live-dead cell staining and the growth pattern of nucleus pulposus cells on hydrogels with different stiffness was observed with phalloidin staining under microscope. Immunofluorescence staining was performed to examine the nuclear localization of Yes-associated protein (YAP) and real-time quantitative reverse transcription PCR (qRT-PCR) was used to detect the expression levels of nucleus pulposus cell-associated genes [neural cell adhesion molecule 1 (Ncam-1), aggrecan (Acan), sex-determing region of Y chromosome (SRY)-box transcription factor 9 (Sox9)]. A rat caudal acupuncture intervertebral disc degeneration model was established. Nucleus pulposus cells cultured on different hydrogels were harvested and injected into the degenerated discs separately. Four weeks after surgery, magnetic resonance imaging (MRI) was performed to analyze the water content of the intervertebral discs in each group. Histological tests were performed to examine the disc structure and proteoglycan levels.Results·The elastic modulus of the hydrogels was 1 kPa and 200 kPa when the concentration of GelMA prepolymerisation solution was at 4% and 15% respectively. SEM observation revealed that the hydrogels showed a loose and porous microstructure, and the porosity of hydrogels decreased significantly with the decrease of their stiffness. In vitro experiments demonstrated that both GelMA hydrogel mediums showed good biocompatibility and the ability to support cell proliferation. Nucleus pulposus cells cultured on the soft matrix (4%GelMA) had a lower elongation and spreading area than those cultured on the stiff matrix (15%GelMA), showing a tendency of YAP concentration in the cytoplasm. The gene expression of nucleus pulposus cells was examined and the levels of Sox9, Acan and Ncam-1 in the soft matrix hydrogel group were 23.7, 6.6 and 12.7 times of those in the control group respectively. In vivo experiments on rat disc degeneration showed that the soft hydrogel matrix group had higher disc water content and structural integrity than the stiff hydrogel matrix group.Conclusion·Compared to stiff GelMA hydrogels, hydrogels with low stiffness better maintain the growth phenotypes in the nucleus pulposus cells and have better therapeutic effect on disc degeneration in vivo.

Objective·To construct an electrospun short fibrous sponge (Sponge@GO) laden with graphene oxide (GO) for chronic wound healing.Methods·Two types of short fibrous sponges (Sponge and Sponge@GO) without and with GO were prepared by means of electrospinning, homogenizing, shaping and crosslinking with glutaraldehyde, respectively. The internal structures of the two sponges were observed with a scanning electron microscope (SEM), and their hydrophilic properties were observed via contact angle and water absorption rate. The biocompatibility of the sponge was verified by CCK-8 and live/dead staining. Twelve 6-week-old SD male rats were divided into control group, Sponge group and Sponge@GO group, with 4 rats in each group. The diabetes models were established by intraperitoneal injection of 1% streptozotocin solution, and three full-layer skin defects with a diameter of 1.0 cm were prepared on the back of each rat after modelling. Covering on the wound, the material was fixed with medical gauze. The control group was only covered with sterile gauze dressing. The wound healing rate was measured and calculated on Day 7 and 14, respectively, while hematoxylin-eosin (H-E) staining and Masson staining were performed on tissues within 0.5 cm around the wound to observe pathological changes. The angiogenesis was observed by α-smooth muscle actin (α-SMA) immunofluorescence staining on Day 14.Results·SEM observation showed that the fiber diameter of Sponge@GO was significantly thinner and the porosity increased. The two types of short fiber scaffolds basically reached the maximum water uptake within 10 min, but the Sponge@GO scaffold showed better water absorption performance. The water contact angle of Sponge@GO scaffold was significantly smaller than that of Sponge, and the difference was statistically significant (P=0.000). The results of CCK-8 method showed that on Day 3 and 5, the Sponge group had better cell proliferation compared with the control group (both P