Wei Sun

Skin injuries remain a significant challenge due to complex healing processes, which often results in delayed recovery, scarring, and impaired functionality. During the complicated wound repair, basic fibroblast growth factor (bFGF) serves as a core regulator for accelerating angiogenesis and fibroblast proliferation. However, conventional bFGF delivery systems suffer from rapid burst release and poor sustained bioavailability, severely limiting their therapeutic efficacy. Inspired by the interactions between the extracellular matrix and growth factors, this study develops a polyanionic hydrogel system for the controlled delivery of bFGF to regulate healing processes. Considering the ionic properties of bFGF, negative 3-Sulfopropyl acrylate potassium salt (SPAK) was ultimately chosen as the affinity ligand, and SPAK could be covalently conjugated to Gelatin Methacryloyl (GelMA) network via photopolymerization. GelMA-SPAK hydrogel material exhibited well affinity-controlled release functionality, with sustained bFGF release maintained for at least 700 h. Besides, bFGF-loaded hydrogel exhibits good cell compatibility, effectively promoted wound healing, improved tissue regeneration, and facilitated vascular growth without inducing significant inflammatory reactions, which may serve as a promising candidate for future intelligent wound dressing applications.

The cellular, dynamics, and spatial heterogeneity of tumor adaptive immunity pose great challenges to tumor-immune cell co-culture studies. Conventional large-cell-scale models often mask the intrinsic diversity of tumor and immune cells, missing the essential information for elucidating immunotherapy mechanisms, discovering rare cell subtypes, and screening cell surface receptors. A single-cell-scale interaction model has the potential to unravel the dynamic processes among specific cell subtypes, uncovering the differences in cell interaction and the resulting divergent outcomes. This paper reports the 3D printing of a single-cell leveled immuno-oncology model to investigate adaptive immune interactions among dendritic cells, T cells, and melanoma cells. The cells within this model successfully recapitulate key motility characteristics of adaptive immunity, including recognition, presentation, cytotoxicity, and immunosuppression. The dynamic results revealed a strong correlation between cell interaction and both motility and spatial distribution, specifically showing that the duration required for contact increased by 4-6 times when the distance exceeds 60 mu m. Tracking and analysis of T cells further revealed the consistency between motility and biofunctions under the stimulation of different dendritic cell types, T cell subtypes, and stimulatory factors. By reproducing cell contact events under controllable variables, the current model helps to refine and validate knowledge of immune synapses and immune-tumor cell interactions.

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease of unknown etiology. Macrophages are implicated in the fibrotic process, but exhibit remarkable plasticity in the activated immune environment in vivo, presenting significant challenges as therapeutic targets. To explore the influence of macrophages on IPF and develop macrophage-targeted therapies, we engineered a micro-lung chip with a lung epithelium-interstitium tissue unit to establish a controlled immune environment containing only macrophages. We discovered that macrophages exacerbated inflammation and fibrosis by comparing microchips treated with bleomycin (BLM) in the presence and absence of macrophages. Based on the duration of BLM treatment, we established pathological models corresponding to inflammation and fibrosis stages. Transcriptome analysis revealed that activation of the PI3K-AKT signalling pathway facilitates the transition from inflammation to fibrosis. However, LY294002, a PI3K inhibitor, not only suppressed fibrosis and decreased the accumulation of M2 macrophages but also intensified the severity of inflammation. These findings suggest that macrophages play a pivotal role in the potential development at the tissue level. The micro-lung chip co-cultured with macrophages holds significant potential for exploring the pathological progression of IPF and elucidating the mechanisms of anti-fibrotic drugs.

Biofabrication is an advanced technology that holds great promise for constructing highly biomimetic three-dimensional human organs. Such technology would help address the issues of immune rejection and organ donor shortage in organ transplantation, aiding doctors in formulating personalized treatments for clinical patients and replacing animal experiments. Biofabrication typically involves the interdisciplinary application of biology, materials science, mechanical engineering, and medicine to generate large amounts of data and correlations that require processing and analysis. Artificial intelligence (AI), with its excellent capabilities in big data processing and analysis, can play a crucial role in handling and processing interdisciplinary data and relationships and in better integrating and applying them in biofabrication. In recent years, the development of the semiconductor and integrated circuit industries has propelled the rapid advancement of computer processing power. An AI program can learn and iterate multiple times within a short period, thereby gaining strong automation capabilities for a specific research content or issue. To date, numerous AI programs have been applied to various processes around biofabrication, such as extracting biological information, designing and optimizing structures, intelligent cell sorting, optimizing biomaterials and processes, real-time monitoring and evaluation of models, accelerating the transformation and development of these technologies, and even changing traditional research patterns. This article reviews and summarizes the significant changes and advancements brought about by AI in biofabrication, and discusses its future application value and direction.

Owing to its thermoresponsive and photocrosslinking properties, gelatin methacryloyl (GelMA) based biomaterials have been commonly used as a novel and promising bioink for 3D bioprinting and various biomedical applications. However, the time and temperature dependent flow behaviors of GelMA at sol-gel transition state pose great challenges when printing thick scaffolds that also sustain high cell viability. Additionally, the turnabilities and in situ photocrosslinking ability of GelMA hydrogel make it a promising candidate for local drug delivery applications. Previous studies have reported on the direct encapsulation of minocycline (MH) in GelMA scaffolds for therapeutic applications. However, achieving prolonged and sustained release of high concentration MH is challenging due to its small molecular size. The aim of this study is to explore an optimal extrusion printing strategy for GelMA bioink in extrusion bioprinting considering its time and temperature dependent flow behaviors and then investigate its applications as drug loading carriers for sustained MH release for cellular protection under oxidative stress. Material properties of GelMA were characterized followed by printing optimization considering both the printability and cell survivability. A metal ion-mediated interaction mechanism between MH, dextran sulfate (DS), and magnesium to form nanoparticle complexes (MH-DS) was adopted for sustained drug release in GelMA. Additionally, an in vitro model was printed with GelMA to study the cell protection effect of MH against oxidative stress. Our results showed that the printability and cell survival rate of GelMA are significantly influenced by printing time, nozzle temperature, and GelMA concentrations. Optimal printing zones were determined based on both printability and cell viability window. Scaffolds printed using the parameters derived from optimal zones exhibited excellent printability and cell viability. We observed that lower concentrations of GelMA resulted in reduced burst release of MH from MH-DS on the first day, leading to more sustained release profiles compared to direct mixing. Additionally, released MH significantly increased fibroblasts survival in an in vitro oxidative stress model. .

Hepatocellular carcinoma (HCC) poses a significant threat to human health and medical care. Its dynamic microenvironment and stages of development will influence the treatment strategies in clinics. Reconstructing tumor-microvascular interactions in different stages of the microenvironment is an urgent need for in vitro tumor pathology research and drug screening. However, the absence of tumor aggregates with paracancerous microvascular and staged tumor-endothelium interactions leads to bias in the antitumor drug responses. Herein, a spheroid-on-demand manipulation strategy was developed to construct staged endothelialized HCC models for drug screening. Pre-assembled HepG2 spheroids were directly printed by alternating viscous and inertial force jetting with high cell viability and integrity. A semi-open microfluidic chip was also designed to form a microvascular connections with high density, narrow diameter, and curved morphologies. According to the single or multiple lesions in stages I or I HCC, endothelialized HCC models from micrometer to millimeter scale with dense tumor cell aggregation and paracancerous endothelial distribution were successively constructed. A migrating stage I HCC model was further constructed under TGF-& beta; treatment, where the spheroids exhibited a more mesenchymal phenotype with a loose cell connection and spheroid dispersion. Finally, the stage IHCC model showed stronger drug resistance compared to the stage I model, while the stage III showed a more rapid response. The corresponding work provides a widely applicable method for the reproduction of tumor-microvascular interactions at different stages and holds great promise for the study of tumor migration, tumor-stromal cell interactions, and the development of anti-tumor therapeutic strategies.

The convergence of 3D bioprinting with powerful manufacturing capability and cellular self-organization that can reproduce intricate tissue microarchitecture and function is a promising direction toward building functional tissues and has yet to be demonstrated. Here, we develop a granular aggregate-prevascularized (GAP) bioink for engineering highly vascularized bone tissues by capitalizing on the condensate-mimicking, self-organization, and angiogenic properties of prevascularized mesenchymal spheroids. The GAP bioink utilizes prevascularized aggregates as building blocks, which are embedded densely in extracellular matrices conducive to spontaneous self-organization. We printed various complex structures with high cell density (∼1.5 × 108 cells/cm3), viability (∼80%), and shape fidelity using GAP bioink. After printing, the prevascularized mesenchymal spheroids developed an interconnected vascular network through angiogenic sprouting. We printed highly vascularized bone tissues using GAP bioink and found that prevascularized spheroids were more conducive to osteogenesis and angiogenesis. We envision that the design of the GAP bioink could be further integrated with human-induced pluripotent stem cell-derived organoids, which opens new avenues to create patient-specific vascularized tissues for therapeutic applications..

Chronic diabetic wounds have become a major healthcare challenge worldwide. Improper treatment may lead to serious complications. Current treatment methods including biological and physical methods and skin grafting have limitations and disadvantages, such as poor efficacy, inconvenience of use, and high cost. Therefore, developing a more effective and feasible treatment is of great significance for the repair of chronic diabetic wounds. Hydrogels can be designed to serve multiple functions to promote the repair of chronic diabetic wounds. Furthermore, 3D bioprinting enables hydrogel customization to fit chronic diabetic wounds, thus facilitating the healing process. This paper reports a study of 3D printing of a collagen–hyaluronic acid composite hydrogels with application for chronic diabetic wound repair. In situ printed hydrogels were developed by a macromolecular crosslinking network using methacrylated recombinant human collagen (RHCMA) and methacrylated hyaluronic acid (HAMA), both of which can respond to ultraviolet (UV) irradiation. The hydrogels were also loaded with silver nanoclusters (AgNCs) with ultra-small-size nanoparticles, which have the advantages of deep penetration ability and broad-spectrum high-efficiency antibacterial properties. The results of this study show that the developed RHCMA, HAMA, and AgNCs (RHAg) composite hydrogels present good UV responsiveness, porosity, mechanical properties, printability, and biocompatibility, all of which are beneficial to wound healing. The results of this study further show that the developed RHAg hydrogels not only effectively inhibited Staphylococcus aureus and Pseudomonas aeruginosa but also promoted the proliferation and migration of fibroblasts in vitro and tissue regeneration and collagen deposition in vivo, thus producing a desirable wound repair effect and can be used as an effective functional biomaterial to promote chronic diabetic wound repair.

Adhesive hydrogels possess great potential to be explored as tissue adhesives, surgical sealants, and hemostats. However, it has been a great challenge to develop hydrogels that can function rapidly and controllably on wet, dynamic biological tissues. Inspired by polyphenol chemistry, we introduce a coacervation-triggered shaping strategy that enables the hierarchical assembly of recombinant human collagen (RHC) and tannic acid (TA). The conformation of the RHC and TA aggregates is controlled to evolve from granular to web-like states, accompanied by the significant enhancement of mechanical and adhesion performance. The coacervation and assembly process is driven by intermolecular interactions, especially hydrogen bonding between RHC and TA. Benefitting from the multifaceted nature of polyphenol chemistry, the hierarchically assembled hydrogels revealed excellent properties as surgical sealing materials, including fast gelation time (within 10 s), clotting time (within 60 s), ultrastretchability (strain >10 000%), and tough adhesion (adhesive strength >250 kPa). In vivo experiments demonstrated complete sealing of severely leaking heart and liver tissues with the assistance of in situ formed hydrogels during 7 d of follow-up. This work presents a highly promising hydrogel-based surgical sealant in wet and dynamic biological environments for future biomedical applications.

Nerve guidance conduits (NGCs) have become a promising alternative for peripheral nerve regeneration; however, the outcome of nerve regeneration and functional recovery is greatly affected by the physical, chemical, and electrical properties of NGCs. In this study, a conductive multiscale filled NGC (MF-NGC) consisting of electrospun poly(lactide-co-caprolactone) (PCL)/collagen nanofibers as the sheath, reduced graphene oxide /PCL microfibers as the backbone, and PCL microfibers as the internal structure for peripheral nerve regeneration is developed. The printed MF-NGCs presented good permeability, mechanical stability, and electrical conductivity, which further promoted the elongation and growth of Schwann cells and neurite outgrowth of PC12 neuronal cells. Animal studies using a rat sciatic nerve injury model reveal that the MF-NGCs promote neovascularization and M2 transition through the rapid recruitment of vascular cells and macrophages. Histological and functional assessments of the regenerated nerves confirm that the conductive MF-NGCs significantly enhance peripheral nerve regeneration, as indicated by improved axon myelination, muscle weight increase, and sciatic nerve function index. This study demonstrates the feasibility of using 3D-printed conductive MF-NGCs with hierarchically oriented fibers as functional conduits that can significantly enhance peripheral nerve regeneration.