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Biphasic scaffolds with biomimetic structure are essential to osteochondral tissue engineering. However, insufficient mechanical properties limit their applications. Here, a novel biphasic scaffold was designed and fabricated using a multi-nozzle three-dimensional (3D) printer with hydroxyapatite (HAp) and polycaprolactone (PCL). HAp was first printed as the subchondral layer and strengthened by sintering, followed by printing PCL as the cartilage layer on top of the HAp layer. High interface bonding strength between the two layers was obtained by controlling the temperature of the printing platform. Compression tests showed that the biphasic scaffold had properties between those of pure HAp and PCL scaffolds, and its compressive modulus was about 18 MPa at the strain of 0–5% and 143 MPa at the strain of 5–10%, which was separately at the range of native cartilage and subchondral bone. Finite element simulation was adopted to investigate the variation of inner structure of the biphasic scaffold under compression, demonstrating a biomimetic strengthened structure with a deformable cartilage layer. Therefore, the biphasic HAp/PCL scaffold takes advantage of both the rigidity of HAp and the elasticity of PCL, thus has biomimetic mechanical properties for its further applications.

The expansion and harvest of stem cells at clinically relevant scales is critical for cell-based therapies. These approaches need to be robust and cost-effective, support the functional maintenance of desired cell behaviors, and allow for simple harvest. Here, we introduce a real-time monitoring 3D printing approach to fabricate scaffolds with quadruple hierarchical structure that meet these design goals for stem cell expansion. Specifically, a versatile strategy was developed to produce scaffolds from alginate and gelatin with approximately 102 μm interconnected macropores, 300 μm microfilaments, 1.3 mm hollow channels, and centimeter-scale overall dimensions. The scaffolds exhibited good pattern fidelity and stable mechanical properties (compressive modulus value was 22-fold that of hydrogels from the same materials), facilitating uniform and efficient cell seeding with high viability (98.9%). The utility of the scaffold was shown with the 3D culture of HepaRG cells and embryonic stem cells (ESCs) with aggregated morphology, and significantly enhanced cell proliferation was observed compared to those of cultures on flat surfaces, obtaining approximately 2 × 108 cells within a single culture. Interestingly, the functional behavior of the cells was dependent on the cell type, as ESCs maintained their pluripotency, while HepaRG cells improved their hepatic differentiation. Cells were harmlessly harvested through chelating the calcium ions in the cross-linked alginate and de-cross-linking the scaffolds, indicating the potential of this study for scalable stem cell culture for numerous downstream applications.

Significance: Artificial skin (AS) is widely used in dermatology, pharmacology, and toxicology, and has great potential in transplant medicine, burn wound care, and chronic wound treatment. There is a great demand for high-quality AS product and a non-invasive detection method is highly desirable. Aim: To quantify the constructure parameters (i.e., thickness and surface roughness) of AS samples in the culture cycle and explore the growth regularities using optical coherent tomography (OCT). Approach: An adaptive interface detection algorithm is developed to recognize surface points in each A-scan, offering a rapid method to calculate parameters without constructing OCT B-scan pictures and further achieving realizing real-time quantification of AS thickness and surface roughness. Experiments on standard roughness plates and H&E-staining microscopy were performed as a verification. Results: As applied on the whole cycle of AS culture, our method’s results show that during the air–liquid culture, the surface roughness of the skin first decreases and then exhibits an increase, which implies coincidence with the degree of keratinization under a microscope. And normal and typical abnormal samples can be differentiated by thickness and roughness parameters during the culture cycle. Conclusions: The adaptive interface detection algorithm is suitable for high-sensitivity, fast detection, and quantification of the interface with layered characteristic tissues, and can be used for non-destructive detection of the growth regularity of AS sample thickness and roughness during the culture cycle.

Background This pioneering study is aimed to design training models for robotic pancreaticojejunostomy (PJ) and to assess their usefulness using quality improvement exercise in the dry lab. Methods Three dry lab models were developed including the anastomosis model of a transected silicon pancreatic stent (model 1), a rough model (model 2) simulating PJ, and an advanced three-dimensional printed model (model 3) more vividly simulating PJ. Three surgeons (A, B, C) with same specialty and levels of expertise in surgery were enrolled in the training which was divided into three rounds of tasks. In the first round, all three surgeons (A, B, C) participated in the training on basic technical tasks before moved on to the next rounds. While surgeons A, B participated in the second round on model 1, only surgeon A worked on model 2 in the third round. Their proficiency of performance was evaluated on model 3. Results The results of the first and second rounds between surgeons are similar. Surgeon A practiced with model 2 for 6 h, completing 10 cases. In model 3, the times of attempts before achieving a consecutively three times of satisfactory anastomosis procedures were compared, for surgeon A, six cases, 20 for B and 25 for C. Conclusions The specifically designed series of dry lab training models may be a potential training tool for advancing the robotic PJ through quality improvement exercise in dry lab. Further larger and well-designed studies are warranted to validate this issue.

In three-dimensional (3D) bioprinting, errors during the printing process leads to lower structural fidelity, and the desired structural and functional performances cannot be fully satisfied. Process monitoring with high-speed imaging techniques is helpful for identifying material deposition errors. 3D reconstruction of printed objects enables comprehensive evaluation of structural characteristics, with wide-field full-depth imaging being necessary for large objects. In this study, we demonstrate 3D extrusion-based bioprinter-associated optical coherence tomography (3D P-OCT) to achieve high-speed, wide-field and full-depth imaging, and provide in situ process monitoring and comprehensive evaluation for 3D bioprinting. In 3D P-OCT, a wide field was achieved with a lateral image mosaic using the simplified iterative closest point algorithm, and the extension of imaging depth was achieved with a longitudinal image mosaic using image fusion based on maximum intensity values. During the printing process, 3D P-OCT enables real-time multi-parameter quantification for intelligent feedback. In conclusion, with in situ process monitoring and evaluation, 3D P-OCT contributes to ensure better structural and functional performances of 3D functional tissue constructs.

Cell therapy, the treatment of diseases using living cells, offers a promising clinical approach to treating refractory diseases. The global market for cell therapy is growing rapidly, and there is an increasing demand for automated methods that can produce large quantities of high quality therapeutic cells. Biomaterials can be used during cell production to establish a biomimetic microenvironment that promotes cell adhesion and proliferation while maintaining target cell genotype and phenotype. Here we review recent progress and emerging techniques in biomaterial-assisted cell production. The increasing use of auxiliary biomaterials and automated production methods provides an opportunity to improve quality control and increase production efficiency using standardized GMP-compliant procedures.

One of the major obstacles in engineering thick and complex tissues while vascularizing tissues in vitro is to maintain cell viability during tissue growth and structural organization. Adipose-derived stromal (ADS) cells were used to establish a multicellular system through a cell-assembly technique. Attempts were made to control ADS cells differentiation into different targeted cell types according to their positions within an orderly 3D structure. Oil red 0 staining confirmed that the ADS cells in the structure differentiated into adipocytes with a spherical shape while immunostaining tests confirmed that the endothelial growth factor induced ADS cells on the walls of channels differentiated into mature endothelial cells and then organized into tubular structures throughout the engineered 3D structure. The endothelin-1 and nitric oxide release rules of the endothelial cells were coincidental with those in vivo. This study provides a new approach to engineer orderly endothelial vessel networks in vitro and has potential applications in adipose-tissue engineering.

One of the major obstacles in drug discovery is the lack of in vitro three-dimensional (3D) models that can capture more complex features of a disease.Here we established a in vitro physiological model of the metabolic syndrome (MS) using cell-assembly technique (CAT), which can assemble cells into designated places to form complex 3D structures. Adipose-derived stromal (ADS) cells were assembled with gelatin/alginate/fibrinogen. Fibrin was employed as an effective material to regulate ADS cell differentiation and self-organization along with other methods. ADS cells differentiated into adipocytes and endothelial cells, meanwhile, the cells were induced to self-organize into an analogous tissue structure. Pancreatic islets were then deposited at designated locations and constituted the adipoinsular axis with adipocytes. Analysis of the factors involved in energy metabolism showed that this system could capture more pathological features of MS. Drugs known to have effects on MS showed accordant effects in this system, indicating that the model has potential in MS drug discovery. Overall, this study demonstrated that cell differentiation and self-organization can be regulated by techniques combined with CAT. The model presented could result in a better understanding of the pathogenesis of MS and the development of new technologies for drug discovery.

One of the major obstacles in developing drugs for diabetes is the lack of in vitro models that can capture more features of the dynamic insulin secretion. Here, we engineered an insulin secretion model by cell-assembly technique which can assemble cells into designated places to form complex three-dimensional structures. Adipose-derived stromal cells were assembled and induced differentiation into adipocytes; pancreatic islets were then assembled at designated stations. A perfusion system was used for a time-dependent estimation of insulin response to glucose stimulation. After long-term exposure to high glucose, the insulin secretion peak value of β-cell in the 3D system decreased and delayed compared with the 2D culture system. These results suggested that adipocytes in 3-D structure help β-cells capture more pathologic features of diabetes. Drugs, Nateglinide and rosiglitazone, known to have effects on diabetes showed accordant effect in the system. This 3D culture model provides an excellent system to study the insulin secretion kinetics of the β-cells. This study also demonstrates that the 3D culture system can provide a model for diabetes drug discovery.

One of the major obstacles in developing multifunctional drugs for the metabolic syndrome (MS) is lack of in vitro models that capture more complex features of the disease. Here we give the first report that establishes an energy metabolic system model using cell-assembly technique which can assemble cells into designated places to form complex three-dimensional structures. Adipose-derived stromal cells were assembled and induced differentiation into adipocytes and endothelial cells; pancreatic islets were then deposited at designated locations and constituted adipoinsular axis with adipocytes. Analysis of the factors involved in energy metabolism showed our system could capture more physiological and pathophysiological features of the in vivo energy metabolism. Drugs known to have effects on MS showed accordant effects in the systems. Construction and study of such multicellular systems could help us better understand pathogenesis of MS, develop new technologies for drug discovery, and foster applications in tissue engineering and metabolomics profiling.