Assessment of cartilage regeneration on 3D collagen-polycaprolactone scaffolds: Evaluation of growth media in static and in perfusion bioreactor dynamic culture

Evaluation of rabbit adipose derived stem cells fate in perfused multilayered silk fibroin composite scaffold for Osteochondral repair

Development of osteochondral tissue engineering approaches using scaffolds seeded with stem cells in association with mechanical stimulations has been recently considered as a promising technique for the repair of this tissue. In this study, an integrated and biomimetic trilayered silk fibroin (SF) scaffold containing SF nanofibers in each layer was fabricated. The osteogenesis and chondrogenesis of stem cells seeded on the fabricated scaffolds were investigated under a perfusion flow. 3-Dimethylthiazol-2,5-diphenyltetrazolium bromide assay showed that the perfusion flow significantly enhanced cell viability and proliferation. Analysis of gene expression by stem cells revealed that perfusion flow had significantly upregulated the expression of osteogenic and chondrogenic genes in the bone and cartilage layers and downregulated the hypertrophic gene expression in the intermediate layer of the scaffold. In conclusion, applying flow perfusion on the prepared integrated trilayered SF-based scaffold can support osteogenic and chondrogenic differentiation for repairing osteochondral defects.

3D-Printed Antibacterial Scaffolds for the Regeneration of Alveolar Bone in Severe Periodontitis

Current clinical treatment of periodontitis alleviates periodontal symptoms and helps to keep the disease under control for extended periods. Despite this, a significant destruction of the tooth's underlying bone tissue often takes place progressively. Herein, we present a two-way therapeutic approach for local delivery of antibacterial agents and bone tissue regeneration, incorporating ~1% w/w tetracycline hydrochloride (TCH) into a 3D-printed scaffold composed of poly(ε-caprolactone) (PCL). Samples were assessed for their morphological, physicochemical, pharmacokinetic, and antibacterial properties. Furthermore, osteoprecursor cells (MC3T3-E1) were employed to evaluate the osteoinductive potential of the drug-loaded scaffolds. Cell proliferation, viability, and differentiation were determined on all cell-seeded scaffolds. At the end of the culture, PCL-TCH scaffolds promoted abundant collagen organic matrix, demonstrating augmented alkaline phosphatase (ALP) activity and areas of accumulated mineralised bone tissue, despite their belayed cell proliferation. Based on the observed effectiveness of the PCL-TCH scaffolds to inhibit Staphylococcus aureus, these constructs could serve as an alternative bioactive implant that supports bacterial inhibition and favours a 3D microenvironment for bone tissue regeneration in severe periodontitis.

Efficient expansion and delayed senescence of hUC-MSCs by microcarrier-bioreactor system

BACKGROUND

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are widely used in cell therapy due to their robust immunomodulatory and tissue regenerative capabilities. Currently, the predominant method for obtaining hUC-MSCs for clinical use is through planar culture expansion, which presents several limitations. Specifically, continuous cell passaging can lead to cellular aging, susceptibility to contamination, and an absence of process monitoring and control, among other limitations. To overcome these challenges, the technology of microcarrier-bioreactor culture was developed with the aim of ensuring the therapeutic efficacy of cells while enabling large-scale expansion to meet clinical requirements. However, there is still a knowledge gap regarding the comparison of biological differences in cells obtained through different culture methods.

METHODS

We developed a culture process for hUC-MSCs using self-made microcarrier and stirred bioreactor. This study systematically compares the biological properties of hUC-MSCs amplified through planar culture and microcarrier-bioreactor systems. Additionally, RNA-seq was employed to compare the differences in gene expression profiles between the two cultures, facilitating the identification of pathways and genes associated with cell aging.

RESULTS

The findings revealed that hUC-MSCs expanded on microcarriers exhibited a lower degree of cellular aging compared to those expanded through planar culture. Additionally, these microcarrier-expanded hUC-MSCs showed an enhanced proliferation capacity and a reduced number of cells in the cell cycle retardation period. Moreover, bioreactor-cultured cells differ significantly from planar cultures in the expression of genes associated with the cytoskeleton and extracellular matrix.

CONCLUSIONS

The results of this study demonstrate that our microcarrier-bioreactor culture method enhances the proliferation efficiency of hUC-MSCs. Moreover, this culture method exhibits the potential to delay the process of cell aging while preserving the essential stem cell properties of hUC-MSCs.

Fabricating the cartilage: recent achievements

This review aims to describe the most recent achievements and provide an insight into cartilage engineering and strategies to restore the cartilage defects. Here, we discuss cell types, biomaterials, and biochemical factors applied to form cartilage tissue equivalents and update the status of fabrication techniques, which are used at all stages of engineering the cartilage. The actualized concept to improve the cartilage tissue restoration is based on applying personalized products fabricated using a full cycle platform: a bioprinter, a bioink consisted of ECM-embedded autologous cell aggregates, and a bioreactor. Moreover, in situ platforms can help to skip some steps and enable adjusting the newly formed tissue in the place during the operation. Only some achievements described have passed first stages of clinical translation; nevertheless, the number of their preclinical and clinical trials is expected to grow in the nearest future.

Strategies of immobilizing BMP-2 with 3D-printed scaffolds to improve osteogenesis

The management and definitive treatment of critical-size bone defects in severe trauma, tumor resection and congenital malformation are troublesome for orthopedic surgeons and patients worldwide without recognized good treatment strategies. Researchers and clinicians are working to develop new strategies to treat these problems. This review aims to summarize the techniques used by additive manufacturing scaffolds loaded with BMP-2 to promote osteogenesis and to analyze the current status and trends in relevant clinical translation. Optimize composite scaffold design to enhance bone regeneration through printing technology, material selection, structure design and loading methods of BMP-2 to advance the clinical therapeutic bone repair field.

Hypoxia Promotes Cartilage Regeneration in Cell-Seeded 3D-Printed Bioscaffolds Cultured with a Bespoke 3D Culture Device

In this study, we investigated the effect of oxygen tension on the expansion of ADMSCs and on their differentiation toward their chondrocytic phenotype, regenerating a lab-based cartilaginous tissue with superior characteristics. Controversial results with reference to MSCs that were cultured under different hypoxic levels, mainly in 2D culturing settings combined with or without other biochemical stimulus factors, prompted our team to study the role of hypoxia on MSCs chondrogenic differentiation within an absolute 3D environment. Specifically, we used 3D-printed honeycomb-like PCL matrices seeded with ADMSCs in the presence or absence of TGF and cultured with a prototype 3D cell culture device, which was previously shown to favor nutrient/oxygen supply, cell adhesion, and infiltration within scaffolds. These conditions resulted in high-quality hyaline cartilage that was distributed uniformly within scaffolds. The presence of the TGF medium was necessary to successfully produce cartilaginous tissues with superior molecular and increased biomechanical properties. Despite hypoxia's beneficial effect, it was overall not enough to fully differentiate ADMSCs or even promote cell expansion within 3D scaffolds alone.

Progress in biomechanical stimuli on the cell-encapsulated hydrogels for cartilage tissue regeneration

BACKGROUND

Worldwide, many people suffer from knee injuries and articular cartilage damage every year, which causes pain and reduces productivity, life quality, and daily routines. Medication is currently primarily used to relieve symptoms and not to ameliorate cartilage degeneration. As the natural healing capacity of cartilage damage is limited due to a lack of vascularization, common surgical methods are used to repair cartilage tissue, but they cannot prevent massive damage followed by injury.

MAIN BODY

Functional tissue engineering has recently attracted attention for the repair of cartilage damage using a combination of cells, scaffolds (constructs), biochemical factors, and biomechanical stimuli. As cyclic biomechanical loading is the key factor in maintaining the chondrocyte phenotype, many studies have evaluated the effect of biomechanical stimulation on chondrogenesis. The characteristics of hydrogels, such as their mechanical properties, water content, and cell encapsulation, make them ideal for tissue-engineered scaffolds. Induced cell signaling (biochemical and biomechanical factors) and encapsulation of cells in hydrogels as a construct are discussed for biomechanical stimulation-based tissue regeneration, and several notable studies on the effect of biomechanical stimulation on encapsulated cells within hydrogels are discussed for cartilage regeneration.

CONCLUSION

Induction of biochemical and biomechanical signaling on the encapsulated cells in hydrogels are important factors for biomechanical stimulation-based cartilage regeneration.

Irrigating degradation properties of silk fibroin-collagen type II composite cartilage scaffold in vitro and in vivo

Silk fibroin-collagen type II scaffolds are promising in cartilage tissue engineering due to their suitable biological functionality to promote proliferation of chondrocytes in vitro. However, their degradation properties, which are of crucial importance as scaffold degradation should consistent with the new tissue formation process, are still unknown. In this study, degradability of silk fibroin-collagen type II cartilage scaffolds was probed both in vitro and in vivo. In vitro degradation experiments show that the scaffolds decreased 32.25 % ± 0.62 %, 34.27 % ± 0.96 %, 36.27 % ± 2.39 % in weight after 8 weeks of degradation at the irrigation velocity of 0 mL/min, 7.89 mL/min and 15.79 mL/min. The degradation ratio, which increases with time and increasing irrigation velocity, is described by combining the built mathematic model and finite element modeling method. The scaffolds after 8 weeks of degradation in vitro keep their mechanical structural integrity to support new tissues. In vivo degradation experiments conducted in rabbits further show that the scaffolds degrade gradually, be absorbed with time and finally collapse in structure. The degradation process is accompanied by the growth of fibrous tissues and the scaffold is filled by fibrous tissues after 12 weeks of implantation. Immunohistology analysis shows that the inflammation caused by scaffolds is controllable and gradually alleviates with time. To sum up, silk fibroin-collagen type II cartilage scaffolds, which show suitable mechanical properties and biocompatibility during degradation in vitro and in vivo, have great potential in cartilage repair. The novelty of the study is that it not only introduces a mathematical model to predict the irrigation degradation ratio, but also provides experimental degradation data support for clinical application of silk fibroin-collagen type II cartilage scaffolds.

A Comparative Study of Three Approaches to Fibre's Surface Functionalization

Polyester-based scaffolds are of research interest for the regeneration of a wide spectrum of tissues. However, there is a need to improve scaffold wettability and introduce bioactivity. Surface modification is a widely studied approach for improving scaffold performance and maintaining appropriate bulk properties. In this study, three methods to functionalize the surface of the poly(lactide-co-ε-caprolactone) PLCL fibres using gelatin immobilisation were compared. Hydrolysis, oxygen plasma treatment, and aminolysis were chosen as activation methods to introduce carboxyl (-COOH) and amino (-NH₂) functional groups on the surface before gelatin immobilisation. To covalently attach the gelatin, carbodiimide coupling was chosen for hydrolysed and plasma-treated materials, and glutaraldehyde crosslinking was used in the case of the aminolysed samples. Materials after physical entrapment of gelatin and immobilisation using carbodiimide coupling without previous activation were prepared as controls. The difference in gelatin amount on the surface, impact on the fibres morphology, molecular weight, and mechanical properties were observed depending on the type of modification and applied parameters of activation. It was shown that hydrolysis influences the surface of the material the most, whereas plasma treatment and aminolysis have an effect on the whole volume of the material. Despite this difference, bulk mechanical properties were affected for all the approaches. All materials were completely hydrophilic after functionalization. Cytotoxicity was not recognized for any of the samples. Gelatin immobilisation resulted in improved L929 cell morphology with the best effect for samples activated with hydrolysis and plasma treatment. Our study indicates that the use of any surface activation method should be limited to the lowest concentration/reaction time that enables subsequent satisfactory functionalization and the decision should be based on a specific function that the final scaffold material has to perform.

Cartilage regeneration using improved surface electrospun bilayer polycaprolactone scaffolds loaded with transforming growth factor-beta 3 and rabbit muscle-derived stem cells

Polycaprolactone (PCL) has recently received significant attention due to its mechanical strength, low immunogenicity, elasticity, and biodegradability. Therefore, it is perfectly suitable for cartilage tissue engineering. PCL is relatively hydrophobic in nature, so its hydrophilicity needs to be enhanced before its use in scaffolding. In our study, first, we aimed to improve the hydrophilicity properties after the network of the bilayer scaffold was formed by electrospinning. Electrospun bilayer PCL scaffolds were treated with ozone and further loaded with transforming growth factor-beta 3 (TGFβ3). In vitro studies were performed to determine the rabbit muscle-derived stem cells’ (rMDSCs) potential to differentiate into chondrocytes after the cells were seeded onto the scaffolds. Statistically significant results indicated that ozonated (O) scaffolds create a better environment for rMDSCs because collagen-II (Coll2) concentrations at day 21 were higher than non-ozonated (NO) scaffolds. In in vivo studies, we aimed to determine the cartilage regeneration outcomes by macroscopical and microscopical/histological evaluations at 3- and 6-month time-points. The Oswestry Arthroscopy Score (OAS) was the highest at both mentioned time-points using the scaffold loaded with TGFβ3 and rMDSCs. Evaluation of cartilage electromechanical quantitative parameters (QPs) showed significantly better results in cell-treated scaffolds at both 3 and 6 months. Safranin O staining indicated similar results as in macroscopical evaluations—cell-treated scaffolds revealed greater staining with safranin, although an empty defect also showed better results than non-cell-treated scaffolds. The scaffold with chondrocytes represented the best score when the scaffolds were evaluated with the Mankin histological grading scale. However, as in previous in vivo evaluations, cell-treated scaffolds showed better results than non-cell-treated scaffolds. In conclusion, we have investigated that an ozone-treated scaffold containing TGFβ3 with rMDSC is a proper combination and could be a promising scaffold for cartilage regeneration.

Static and dynamic culture of human endothelial cells encapsulated inside alginate-gelatin microspheres

This study aimed to explore the angiogenesis potential of human endothelial cells encapsulated inside alginate-gelatin microspheres under static and dynamic culture systems after 7 days. Human umbilical vein endothelial cells were encapsulated inside alginate (1%) and gelatin (1.2%) using an electrostatic encapsulation method. Cells were incubated for 7 days in vitro. The cell survival rate was measured using the MTT assay. The expression of VEGFR-2 and von Willebrand factor genes was studied by real-time PCR assay. Using western blot analysis, we monitored the protein contents of VEGFR-2, vWF, and Caspase 3. The levels of SOD and GPx enzymes were calculated using biochemical kits. Angiogenesis potential was assessed using in vitro Matrigel assay. Data showed an increased survival rate in encapsulated cells cultured under the static condition compared to the conventional 2D condition (p < 0.05). The culture of encapsulated cells under a dynamic bioreactor system did not alter cell viability. Compared to the dynamic culture system, the incubation of encapsulated cells in the static culture system swelled the microspheres (p < 0.05). Both dynamic and static culture models increased the expression of VEGFR-2 and von Willebrand factor in encapsulated cells compared to 2D culture (p < 0.05), showing enhanced functional maturation. Data showed a significant increase of vWF and reduction of apoptosis marker Caspase in the dynamic culture system (p < 0.05). The levels of SOD and GPx were significantly increased in dynamic and static culture models as compared to the control 2D group (p < 0.05). In vitro tubulogenesis assay showed significant induction of angiogenesis in dynamic encapsulated HUVECs indicated with a large number of vascular tubes and arborized ECs compared to the control and static encapsulated HUVECs (p < 0.05). The current study suggests a bioreactor dynamic system is a reliable approach, similar to a static condition, for the expansion of encapsulated human ECs in a 3D milieu.

Small diameter polycaprolactone vascular grafts are patent in sheep carotid bypass but require antithrombotic therapy

Background: Polycaprolactone (PCL) scaffolds exhibit high biocompatibility and are attractive as vascular conduits. Materials & methods: PCL tubes were cultivated in bioreactor with human adipose regenerative cells to assess ex vivo cytocompatibility, whereas in vivo PCL tube patency was evaluated in sheep carotid bypass with and without antithrombotic treatment. Results: Ex vivo results revealed increasing adipose regenerative cells on PCL using dynamic bioreactor culturing. In vivo data showed that 67% (2/3) of grafts in the antithrombotic group were patent at day 28, while 100% (3/3) of control grafts were occluded already during the first week due to thrombosis. Histology showed that patent PCL grafts were recellularized by host cells. Conclusion: PCL tubes may work as small diameter vascular scaffolds under antithrombotic treatment.

Applications of Biocompatible Scaffold Materials in Stem Cell-Based Cartilage Tissue Engineering

Cartilage, especially articular cartilage, is a unique connective tissue consisting of chondrocytes and cartilage matrix that covers the surface of joints. It plays a critical role in maintaining joint durability and mobility by providing nearly frictionless articulation for mechanical load transmission between joints. Damage to the articular cartilage frequently results from sport-related injuries, systemic diseases, degeneration, trauma, or tumors. Failure to treat impaired cartilage may lead to osteoarthritis, affecting more than 25% of the adult population globally. Articular cartilage has a very low intrinsic self-repair capacity due to the limited proliferative ability of adult chondrocytes, lack of vascularization and innervation, slow matrix turnover, and low supply of progenitor cells. Furthermore, articular chondrocytes are encapsulated in low-nutrient, low-oxygen environment. While cartilage restoration techniques such as osteochondral transplantation, autologous chondrocyte implantation (ACI), and microfracture have been used to repair certain cartilage defects, the clinical outcomes are often mixed and undesirable. Cartilage tissue engineering (CTE) may hold promise to facilitate cartilage repair. Ideally, the prerequisites for successful CTE should include the use of effective chondrogenic factors, an ample supply of chondrogenic progenitors, and the employment of cell-friendly, biocompatible scaffold materials. Significant progress has been made on the above three fronts in past decade, which has been further facilitated by the advent of 3D bio-printing. In this review, we briefly discuss potential sources of chondrogenic progenitors. We then primarily focus on currently available chondrocyte-friendly scaffold materials, along with 3D bioprinting techniques, for their potential roles in effective CTE. It is hoped that this review will serve as a primer to bring cartilage biologists, synthetic chemists, biomechanical engineers, and 3D-bioprinting technologists together to expedite CTE process for eventual clinical applications.

The Marine Polysaccharide Ulvan Confers Potent Osteoinductive Capacity to PCL-Based Scaffolds for Bone Tissue Engineering Applications

Hybrid composites of synthetic and natural polymers represent materials of choice for bone tissue engineering. Ulvan, a biologically active marine sulfated polysaccharide, is attracting great interest in the development of novel biomedical scaffolds due to recent reports on its osteoinductive properties. Herein, a series of hybrid polycaprolactone scaffolds containing ulvan either alone or in blends with κ-carrageenan and chondroitin sulfate was prepared and characterized. The impact of the preparation methodology and the polysaccharide composition on their morphology, as well as on their mechanical, thermal, water uptake and porosity properties was determined, while their osteoinductive potential was investigated through the evaluation of cell adhesion, viability, and osteogenic differentiation of seeded human adipose-derived mesenchymal stem cells. The results verified the osteoinductive ability of ulvan, showing that its incorporation into the polycaprolactone matrix efficiently promoted cell attachment and viability, thus confirming its potential in the development of biomedical scaffolds for bone tissue regeneration applications.

In Vivo Cartilage Regeneration with Cell-Seeded Natural Biomaterial Scaffold Implants: 15-Year Study

Articular cartilage can be easily damaged from human's daily activities, leading to inflammation and to osteoarthritis, a situation that can diminish the patients' quality of life. For larger cartilage defects, scaffolds are employed to provide cells the appropriate three-dimensional environment to proliferate and differentiate into healthy cartilage tissue. Natural biomaterials used as scaffolds, attract researchers' interest because of their relative nontoxic nature, their abundance as natural products, their easy combination with other materials, and the relative easiness to establish Marketing Authorization. The last 15 years were chosen to review, document, and elucidate the developments on cell-seeded natural biomaterials for articular cartilage treatment in vivo. The parameters of the experimental designs and their results were all documented and presented. Considerations about the newly formed cartilage and the treatment of cartilage defects were discussed, along with difficulties arising when applying natural materials, research limitations, and tissue engineering approaches for hyaline cartilage regeneration.

[In vitro regeneration of tissue engineered cartilage and its clinical application for nasal reconstruction]

Objective

To explore the clinical application and effectiveness of a personalized tissue engineered cartilage with seed cells derived from ear or nasal septal cartilage and poly-glycolic acid (PGA)/poly-lactic acid (PLA) as scaffold in patients with nasal reconstruction.

Methods

Between March 2014 and October 2015, 4 cases of acquired nasal defects and 1 case of congenital nasal deformity were admitted. The patient with congenital nasal deformity was a 4-year-old boy, and the source of seed cells was nasal septal cartilage. The other 4 patients were 3 males and 1 female, aged 24-33 years, with an average of 28.5 years. They all had multiple nasal subunit defects caused by trauma and the source of seed cells was auricular cartilage. The tissue engineered cartilage framework was constructed in the shape of normal human nasal alar cartilage and L-shaped silicone prosthesis with seed cells from cartilage and PGA-PLA compound biodegradable scaffold. The boy underwent nasal deformity correction and silicone prosthesis implantation in the first stage, and the prosthesis was removed and implanted with tissue engineered cartilage in the second stage; the remaining 4 adult patients all used expanded forehead flaps for nasal reconstruction. All 5 patients underwent 1-4 nasal revisions. The implanted tissue engineered cartilage was observed during the operation and taken from 2 patients for histological examination.

Results

All the incisions healed by first intention after the tissue engineered cartilage implantation, and the expanded forehead flaps survived. Postoperative low fever occurred in 3 patients. No complications such as infection, obvious immune rejection response, and tissue engineered cartilage protrusion were found in all patients. All patients were followed up 9-74 months (mean，54.8 months). During follow-up, the patients had no obvious discomfort in the nose and the ventilation function were good. All patients were satisfied with the nasal contour. Early-stage histological examination showed the typical cartilage characteristics in 1 patient after the implantation of tissue engineered cartilage. Late-stage histological examination in 1 patient of tissue engineered cartilage showed the characteristics of fibrous connective tissue; and the other showed there was remaining cartilage.

Conclusion

The safety of tissue engineered cartilage constructed in vitro for reconstruction is preliminarily confirmed, but the effectiveness still needs further verification.

The Application of Bioreactors for Cartilage Tissue Engineering: Advances, Limitations, and Future Perspectives

Tissue engineering (TE) has brought new hope for articular cartilage regeneration, as TE can provide structural and functional substitutes for native tissues. The basic elements of TE involve scaffolds, seeded cells, and biochemical and biomechanical stimuli. However, there are some limitations of TE; what most important is that static cell culture on scaffolds cannot simulate the physiological environment required for the development of natural cartilage. Recently, bioreactors have been used to simulate the physical and mechanical environment during the development of articular cartilage. This review aims to provide an overview of the concepts, categories, and applications of bioreactors for cartilage TE with emphasis on the design of various bioreactor systems.

Optimized Media Volumes Enable Homogeneous Growth of Mesenchymal Stem Cell-Based Engineered Cartilage Constructs

Despite marked advances in the field of cartilage tissue engineering, it remains a challenge to engineer cartilage constructs with homogeneous properties. Moreover, for engineered cartilage to make it to the clinic, this homogeneous growth must occur in a time-efficient manner. In this study we investigated the potential of increased media volume to expedite the homogeneous maturation of mesenchymal stem cell (MSC) laden engineered constructs over time in vitro. We assessed the MSC-laden constructs after 4 and 8 weeks of chondrogenic culture using bulk mechanical, histological, and biochemical measures. These assays were performed on both the intact total constructs and the construct cores to elucidate region-dependent differences. In addition, local strain transfer was assessed to quantify depth-dependent mechanical properties throughout the constructs. Our findings suggest that increased media volume enhances matrix deposition early in culture and ameliorates unwanted regional heterogeneities at later time points. Taken together, these data support the use of higher media volumes during in vitro culture to hasten tissue maturation and increase the core strength of tissue constructs. These findings will forward the field of cartilage tissue engineering and the translation of tissue engineered constructs.

An effective device and method for enhanced cell growth in 3D scaffolds: Investigation of cell seeding and proliferation under static and dynamic conditions

Cell adhesion on 3D-scaffolds is a challenging task to succeed high cell densities and even cell distribution. We aimed to design a 3D-cell Culture Device (3D-CD) for static seeding and cultivation, to be used with any kind of scaffold, limiting cell loss and facilitating nutrient supply. 3D printing technology was used for both scaffold and device fabrication. Apart from testing the device, the purpose of this study was to assess and compare static and dynamic seeding and cultivation methods, of wet and dry scaffolds, under normoxic and hypoxic conditions and their effects on parameters such as cell seeding efficiency, cell distribution and cell proliferation. Human adipose tissue was harvested and cultured in 3D-printed poly(epsilon-caprolactone) scaffolds. Micro-CT scans were performed and projection images were reconstructed into cross section images. We created 3D images to visualize cell distribution and orientation inside the scaffolds. The group of prewetted scaffolds was the most favorable to cell attachment. The 3D-cell Culture Device (3D-CD) enhanced cell seeding efficiency with almost no cell loss. We suggest that the most favorable outcome can be produced with static seeding in the device for 24 h, followed either by static cultivation in the same device or by dynamic cultivation.

Small-Scale Fluidized Bed Bioreactor for Long-Term Dynamic Culture of 3D Cell Constructs and in vitro Testing

With the increasing interest in three-dimensional (3D) cell constructs that better represent native tissues, comes the need to also invest in devices, i.e., bioreactors, that provide a controlled dynamic environment similar to the perfusion mechanism observed in vivo. Here a laboratory-scale fluidized bed bioreactor (sFBB) was designed for hydrogel (i.e., alginate) encapsulated cells to generate a dynamic culture system that produced a homogenous milieu and host substantial biomass for long-term evolution of tissue-like structures and “per cell” performance analysis. The bioreactor design, conceptualized through scale-down empirical similarity rules, was initially validated through computational fluid dynamics analysis for the distributor capacity of homogenously dispersing the flow with an average fluid velocity of 4.596 × 10^–4 m/s. Experimental tests then demonstrated a consistent fluidization of hydrogel spheres, while maintaining shape and integrity (606.9 ± 99.3 μm diameter and 0.96 shape factor). It also induced mass transfer in and out of the hydrogel at a faster rate than static conditions. Finally, the sFBB sustained culture of alginate encapsulated hepatoblastoma cells for 12 days promoting proliferation into highly viable (>97%) cell spheroids at a high final density of 27.3 ± 0.78 million cells/mL beads. This was reproducible across multiple units set up in parallel and operating simultaneously. The sFBB prototype constitutes a simple and robust tool to generate 3D cell constructs, expandable into a multi-unit setup for simultaneous observations and for future development and biological evaluation of in vitro tissue models and their responses to different agents, increasing the complexity and speed of R&D processes.

Hybrid Sponge-Like Scaffolds Based on Ulvan and Gelatin: Design, Characterization and Evaluation of Their Potential Use in Bone Tissue Engineering

Ulvan, a bioactive natural sulfated polysaccharide, and gelatin, a collagen-derived biopolymer, have attracted interest for the preparation of biomaterials for different biomedical applications, due to their demonstrated compatibility for cell attachment and proliferation. Both ulvan and gelatin have exhibited osteoinductive potential, either alone or in combination with other materials. In the current work, a series of novel hybrid scaffolds based on crosslinked ulvan and gelatin was designed, prepared and characterized. Their mechanical performance, thermal stability, porosity, water-uptake and in vitro degradation ability were assessed, while their morphology was analyzed through scanning electron microscopy. The prepared hybrid ulvan/gelatin scaffolds were characterized by a highly porous and interconnected structure. Human adipose-derived mesenchymal stem cells (hADMSCs) were seeded in selected ulvan/gelatin hybrid scaffolds and their adhesion, survival, proliferation, and osteogenic differentiation efficiency was evaluated. Overall, it was found that the prepared hybrid sponge-like scaffolds could efficiently support mesenchymal stem cells' adhesion and proliferation, suggesting that such scaffolds could have potential uses in bone tissue engineering.