Printed Hydrogel Scaffolds Research Articles

In Vitro Investigation of 3D Printed Hydrogel Scaffolds with Electrospun Tidemark Component for Modeling Osteochondral Interface.

Osteochondral (OC) tissue plays a crucial role due to its ability to connect bone and cartilage tissues. To address the complexity of structure and functionality at the bone-cartilage interface, relevant to the presence of the tidemark as a critical element at the bone-cartilage boundary, we fabricated graded scaffolds through sequential 3D printing. The scaffold's bottom layer was based on a gelatin/oxidized alginate mixture enriched with hydroxyapatite (HAp) to create a rougher surface and larger pores to promote osteogenesis. In contrast, the upper layer was engineered to have smaller pores and aimed to promote cartilage tissue formation and mimic the physical properties of the cartilage. An electrospun ε-polycaprolactone (PCL) membrane with micrometer-range pores was incorporated between the layers to replicate the function of tidemark-a barrier to prevent vascularization of cartilage from subchondral bone tissue. In vitro cell studies confirmed the viability of the cells on the layers of the scaffolds and the ability of PCL mesh to prevent cellular migration. The fabricated scaffolds were thoroughly characterized, and their mechanical properties were compared to native OC tissue, demonstrating suitability for OC tissue engineering and graft modeling. The distance of gradient of mineral concentration was found to be 151 µm for grafts and the native OC interface.

Digital light processing printed hydrogel scaffolds with adjustable modulus

Hydrogels are extensively explored as biomaterials for tissue scaffolds, and their controlled fabrication has been the subject of wide investigation. However, the tedious mechanical property adjusting process through formula control hindered their application for diverse tissue scaffolds. To overcome this limitation, we proposed a two-step process to realize simple adjustment of mechanical modulus over a broad range, by combining digital light processing (DLP) and post-processing steps. UV-curable hydrogels (polyacrylamide-alginate) are 3D printed via DLP, with the ability to create complex 3D patterns. Subsequent post-processing with Fe3+ ions bath induces secondary crosslinking of hydrogel scaffolds, tuning the modulus as required through soaking in solutions with different Fe3+ concentrations. This innovative two-step process offers high-precision (10 μm) and broad modulus adjusting capability (15.8–345 kPa), covering a broad range of tissues in the human body. As a practical demonstration, hydrogel scaffolds with tissue-mimicking patterns were printed for cultivating cardiac tissue and vascular scaffolds, which can effectively support tissue growth and induce tissue morphologies.

3D Bioprinting of Artificial Skin Substitute with Improved Mechanical Property and Regulated Cell Behavior through Integrating Patterned Nanofibrous Films.

Three-dimensional (3D) bioprinting has advantages for constructing artificial skin tissues in replicating the structures and functions of native skin. Although many studies have presented improved effect of printing skin substitutes in wound healing, using hydrogel inks to fabricate 3D bioprinting architectures with complicated structures, mimicking mechanical properties, and appropriate cellular environments is still challenging. Inspired by collagen nanofibers withstanding stress and regulating cell behavior, a patterned nanofibrous film was introduced to the printed hydrogel scaffold to fabricate a composite artificial skin substitute (CASS). The artificial dermis was printed using gelatin-hyaluronan hybrid hydrogels containing human dermal fibroblasts with gradient porosity and integrated with patterned nanofibrous films simultaneously, while the artificial epidermis was formed by seeding human keratinocytes upon the dermis. The collagen-mimicking nanofibrous film effectively improved the tensile strength and fracture resistance of the CASS, making it sewable for firm implantation into skin defects. Meanwhile, the patterned nanofibrous film also provided the biological cues to guide cell behavior. Consequently, CASS could effectively accelerate the regeneration of large-area skin defects in mouse and pig models by promoting re-epithelialization and collagen deposition. This research developed an effective strategy to prepare composite bioprinting architectures for enhancing mechanical property and regulating cell behavior, and CASS could be a promising skin substitute for treating large-area skin defects.

4D printed hydrogel scaffold with swelling-stiffening properties and programmable deformation for minimally invasive implantation.

The power of three-dimensional printing in designing personalized scaffolds with precise dimensions and properties is well-known. However, minimally invasive implantation of complex scaffolds is still challenging. Here, we develop amphiphilic dynamic thermoset polyurethanes catering for multi-material four-dimensional printing to fabricate supportive scaffolds with body temperature-triggered shape memory and water-triggered programmable deformation. Shape memory effect enables the two-dimensional printed pattern to be fixed into temporary one-dimensional shape, facilitating transcatheter delivery. Upon implantation, the body temperature triggers shape recovery of the one-dimensional shape to its original two-dimensional pattern. After swelling, the hydrated pattern undergoes programmable morphing into the desired three-dimensional structure because of swelling mismatch. The structure exhibits unusual soft-to-stiff transition due to the water-driven microphase separation formed between hydrophilic and hydrophobic chain segments. The integration of shape memory, programmable deformability, and swelling-stiffening properties makes the developed dynamic thermoset polyurethanes promising supportive void-filling scaffold materials for minimally invasive implantation.

A Printable Hydrogel Loaded with Medicinal Plant Extract for Promoting Wound Healing.

How to promote wound healing is still a major challenge in the healthcare while macrophages are a critical component of the healing process. Compared to various bioactive drugs, many plants have been reported to facilitate the wound healing process by regulating the immune response of wounds. In this work, a Three-dimensional (3D) printed hydrogel scaffold loaded with natural Centella asiatica extract (CA extract) is developed for wound healing. This CA@3D scaffold uses gelatin (Gel)and sodium alginate (SA)with CA extract as bio-ink for 3D printing. The CA extract contains a variety of bioactive compounds that make the various active ingredients in Centella asiatica work in concert. The printed CA@3D scaffold can fit the shape of wound, orchestrate the macrophages and immune responses within the wound, and promote wound healing compared to commercial wound dressings. The underlying mechanism of promoting wound healing is also illuminated by applying multi-omic analyses. Moreover, the CA extract loaded 3D scaffold also showed great ability to promote wound healing in diabetic chronic wounds. Due to its ease of preparation, low-cost, biosafety, and therapeutic outcomes, this work proposes an effective strategy for promoting chronic wound healing.

Sawdust-derived cellulose nanofibrils with high biosafety for potential bioprinting

Cellulose is a sustainable biopolymer with potential to reduce the adverse environmental impact of non-biodegradable plastics and promote a circular economy. Nanocellulose, a representative biobased nanomaterial, is considered as a promising material in biomedical applications due to its outstanding biocompatibility and low toxicity. However, the presence of some leachable immunogenic contaminants, such as endotoxin and (1,3)-β-D-glucan, in nanocellulose will often pose a potential risk in biomedical applications, particularly to the human body in 3D printing. In line with this challenge, a novel nanocellulose fabricating method was innovatively developed from the source of sawdust biomass to minimize the possible immunogenic contaminants presented in the cellulose nanofibrils (CNFs), which will ensure its biocompatibility of the material in applications. The resulting CNFs exhibited a very low level of leachable contaminants, recorded with endotoxin at 1.39 EU/g and (1,3)-β-D-glucan at 2.82 μg/g, respectively, which fall within the acceptable levels of Pharmacopoeia. In the following evaluation with the fabricated CNFs, the printability of the CNF hydrogel scaffolds was further optimized with hydrogel concentration at 5 %, printing pressure at 37 kPa, nozzle size setting up at 25 G, and crosslinker concentration at 200 mM, respectively. As an important property of 3D printed hydrogel scaffold, its biocompatibility was further evaluated and observed through cell culture in vitro, where the extract of hydrogel scaffold demonstrated a 36 % higher cell viability in promoting cell growth and proliferation when compared with that in pure culture medium. This exploration would suggest a possible application in the biomedical field that may not only secure a sound biocompatibility of CNFs produced from sawdust biomass, but also ensure the following 3D-printed scaffold with a viable cell growth and proliferation.

Oxygen Delivery Biomaterials in Wound Healing Applications.

Oxygen (O2 ) delivery biomaterials have attracted great interest in the treatment of chronic wounds due to their potential applications in local and continuous O2 generation and delivery, improving cell viability until vascularization occurs, promoting structural growth of new blood vessels, simulating collagen synthesis, killing bacteria and reducing hypoxia-induced tissue damage. Therefore, different types of O2 delivery biomaterials including thin polymer films, fibers, hydrogels, or nanocomposite hydrogels have been developed to provide controlled, sufficient and long-lasting O2 to prevent hypoxia and maintain cell viability until the engineered tissue is vascularized by the host system. These biomaterials are made by various approaches, such as encapsulating O2 releasing molecules into hydrogels, polymer microspheres and 3D printed hydrogel scaffolds and adsorbing O2 carrying reagents into polymer films of fibers. In this article, different O2 generating sources such as solid inorganic peroxides, liquid peroxides, and photosynthetic microalgae, and O2 carrying perfluorocarbons and hemoglobin are presented and the applications of O2 delivery biomaterials in promoting wound healing are discussed. Furthermore, challenges encountered and future perspectives are highlighted.

A 3D Bioprinted Nanoengineered Hydrogel with Photoactivated Drug Delivery for Tumor Apoptosis and Simultaneous Bone Regeneration via Macrophage Immunomodulation.

One of the significant challenges in bone tissue engineering (BTE) is the healing of traumatic tissue defects owing to the recruitment of local infection and delayed angiogenesis. Herein, a 3D printable multi-functional hydrogel composing polyphenolic carbon quantum dots (CQDs, 100 µg mL-1 ) and gelatin methacryloyl (GelMA, 12 wt%) is reported for robust angiogenesis, bone regeneration and anti-tumor therapy. The CQDs are synthesized from a plant-inspired bioactive molecule, 1, 3, 5-trihydroxybenzene. The 3D printed GelMA-CQDs hydrogels display typical shear-thinning behavior with excellent printability. The fabricated hydrogel displayed M2 polarization of macrophage (Raw 264.7) cells via enhancing anti-inflammatory genes (e.g., IL-4 and IL10), and induced angiogenesis and osteogenesis of human bone mesenchymal stem cells (hBMSCs). The bioprinted hBMSCs are able to produce vessel-like structures after 14 d of incubation. Furthermore, the 3D printed hydrogel scaffolds also show remarkable near infra-red (NIR) responsive properties under 808 nm NIR light (1.0W cm-2 ) irradiation with controlled release of antitumor drugs (≈49%) at pH 6.5, and thereby killing the osteosarcoma cells. Therefore, it is anticipated that the tissue regeneration and healing ability with therapeutic potential of the GelMA-CQDs scaffolds may provide a promising alternative for traumatic tissue regeneration via augmenting angiogenesis and accelerated immunomodulation.

3D printed hydrogel scaffold promotes the formation of hormone-active engineered parathyroid tissue

The parathyroid glands are localized at the back of the thyroid glands in the cervical region and are responsible for regulation of the calcium level in the blood, through specialized cells that sense Ca2+ and secrete parathyroid hormone (PTH) in response to a decline in its serum level. PTH stimulates the skeleton, kidneys and intestines and controls the level of Ca2+ through specialized activities. Iatrogenic removal of the parathyroid gland, as well as damage to its vascular integrity during cauterization are some of the common complications of thyroid surgery. Therefore, regeneration and/or replacement of malfunctioning parathyroid tissue is required. Tissue engineering is an emerging and promising field for patients with organ failure with recent pioneering clinical applications. The success of tissue engineering strategy depends on the use of proper cells, bioactive factors that stimulate the activities of these cells and scaffolds that are produced to recapitulate the tissue structure and support the function of the engineered tissues. 3D printing is a developing strategy for the production of these scaffolds by providing a delicate control over their structure and properties. In this study, human primary parathyroid cells were successfully isolated and their viability and ability to secrete PTH upon stimulation with different levels of Ca2+ were shown in vitro. These cells were then seeded onto 3D printed alginate scaffolds and 3D bioprinted within alginate bioink, and cell viability as well as the ability to secrete PTH upon stimulation were also demonstrated. Therefore, functional hormone-active parathyroid tissue substitute was engineered in vitro through 3D printed hydrogels and autologous cells.

Implantable 3D Printed Hydrogel Scaffolds Loading Copper-Doxorubicin Complexes for Postoperative Chemo/Chemodynamic Therapy

Biomaterial-based implants hold great potential for postoperative cancer treatment due to the enhanced drug dosage at the disease site and decreased systemic toxicity. However, the elaborate design of implants to avoid complicated chemical modification and burst release remains challenging. Herein, we report a three-dimensional (3D) printed hydrogel scaffold to enable sustained release of drugs for postoperative synergistic cancer therapy. The hydrogel scaffold is composed of Pluronic F127 and sodium alginate (SA) as well as doxorubicin (DOX) and copper ions (F127-SA/Cu-DOX hydrogel scaffold). Benefiting from the coordination of Cu(II) with both SA and DOX, burst release of DOX can be overcome, and prolonged release time can be achieved. The therapeutic efficiency can be adjusted by altering the amount of DOX and Cu(II) in the scaffolds. Moreover, apoptosis and ferroptosis of cancer cells can be induced through the combination of chemotherapy and chemodynamic therapy. In addition, DOX supplies excess hydrogen peroxide to enhance the efficiency of Cu-based chemodynamic therapy. When implanted in the resection site, hydrogel scaffolds effectively inhibit tumor growth. Overall, this study may offer a new strategy for fabricating local implants with synergistic therapeutic performance for preventing postoperative cancer recurrence.

3D printed hydrogel/wesselsite-PCL composite scaffold with structural change from core/shell fibers to microchannels for enhanced bone regeneration

Corresponding to the process of bone formation, three-dimensional (3D) scaffolds should provide adaptive structural cues and microenvironment for bone repair at different stages. Herein, we fabricate a core-shell fiber scaffold by coating a layer of polycaprolactone (PCL)/SrCuSi4O10 (wesselsite, CS) on 3D printed hydrogel scaffolds. The core/shell scaffold provided enhanced mechanical support for the defect at the initial stage. Then, the degradation of hydrogels resulted in the transformation of core/shell fiber structure (hydrogel/PCL + CS) to interconnected microchannels (PCL/CS hollow channel), which provided increasing space and clear architectural cues for promoting bone formation and vascularization. Simultaneously, the chemokine stromal cell-derived factor-1α (SDF-1α) loaded in hydrogels achieved sustained release in the initial two weeks to facilitate the recruitment of bone marrow stromal cells (BMSCs) to defect. Subsequently, the degradation of CS nanomaterials yielded the sustained release of bioactive ions (Si, Sr and Cu), promoting osteogenesis and angiogenesis. The in vivo data showed that the prepared scaffolds exhibited enhanced bone repair capacity with abundant new bone formation and blood vessels ingrowth in the defect. Thus, this designed system shows great potential for bone tissue engineering application.

Infiltration from Suspension Systems Enables Effective Modulation of 3D Scaffold Properties in Suspension Bioprinting.

Bioprinting is a biofabrication technology which allows efficient and large-scale manufacture of 3D cell culture systems. However, the available biomaterials for bioinks used in bioprinting are limited by their printability and biological functionality. Fabricated constructs are often homogeneous and have limited complexity in terms of current 3D cell culture systems comprising multiple cell types. Inspired by the phenomenon that hydrogels can exchange liquids under the infiltration action, infiltration-induced suspension bioprinting (IISBP), a novel printing technique based on a hyaluronic acid (HA) suspension system to modulate the properties of the printed scaffolds by infiltration action, was described in this study. HA served as a suspension system due to its shear-thinning and self-healing rheological properties, simplicity of preparation, reusability, and ease of adjustment to osmotic pressure. Changes in osmotic pressure were able to direct the swelling or shrinkage of 3D printed gelatin methacryloyl (GelMA)-based bioinks, enabling the regulation of physical properties such as fiber diameter, micromorphology, mechanical strength, and water absorption of 3D printed scaffolds. Human umbilical vein endothelial cells (HUVEC) were applied as a cell culture model and printed within cell-laden scaffolds at high resolution and cell viability with the IISBP technique. Herein, the IISBP technique had been realized as a reliable hydrogel-based bioprinting technique, which enabled facile modulation of 3D printed hydrogel scaffolds properties, being expected to meet the scaffolds requirements of a wide range of cell culture conditions to be utilized in bioprinting applications.

3D printed hydrogel scaffolds combining glutathione depletion-induced ferroptosis and photothermia-augmented chemodynamic therapy for efficiently inhibiting postoperative tumor recurrence

Surgical resection to achieve tumor-free margins represents a difficult clinical scenario for patients with hepatocellular carcinoma. While post-surgical treatments such as chemotherapy and radiotherapy can decrease the risk of cancer recurrence and metastasis, growing concerns about the complications and side effects have promoted the development of implantable systems for locoregional treatment. Herein, 3D printed hydrogel scaffolds (designed as Gel-SA-CuO) were developed by incorporating one agent with multifunctional performance into implantable devices to simplify the fabrication process for efficiently inhibiting postoperative tumor recurrence. CuO nanoparticles can be effectively controlled and sustained released during the biodegradation of hydrogel scaffolds. Notably, the released CuO nanoparticles not only function as the reservoir for releasing Cu2+ to produce intracellular reactive oxygen species (ROS) but also serve as photothermal agent to generate heat. Remarkably, the heat generated by photothermal conversion of CuO nanoparticles further promotes the efficiency of Fenton-like reaction. Additionally, ferroptosis can be induced through Cu2+-mediated GSH depletion via the inactivation of GPX4. By implanting hydrogel scaffolds in the resection site, efficient inhibition of tumor recurrence after primary resection can be achieved in vivo. Therefore, this study may pave the way for the development of advanced multifunctional implantable platform for eliminating postoperative relapsable cancers.Graphical

3D Biofabrication of a Cardiac Tissue Construct for Sustained Longevity and Function.

In this study, we developed three-dimensional (3D) printed annular ring-like scaffolds of hydrogel (gelatin-alginate) constructs encapsulated with a mixture of human cardiac AC16 cardiomyocytes (CMs), fibroblasts (CFs), and microvascular endothelial cells (ECs) as cardiac organoid models in preparation for investigating the role of microgravity in cardiovascular disease initiation and development. We studied the mechanical properties of the acellular scaffolds and confirmed their cell compatibility as well as heterocellular coupling for cardiac tissue engineering. Rheological analysis performed on the acellular scaffolds showed the scaffolds to be elastogenic with elastic modulus within the range of a native in vivo heart tissue. The microstructural and physicochemical properties of the scaffolds analyzed through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy-attenuated total reflectance (ATR-FTIR) confirmed the mechanical and functional stability of the scaffolds for long-term use in in vitro cell culture studies. HL-1 cardiomyocytes bioprinted in these hydrogel scaffolds exhibited contractile functions over a sustained period of culture. Cell mixtures containing CMs, CFs, and ECs encapsulated within the 3D printed hydrogel scaffolds exhibited a significant increase in viability and proliferation over 21 days, as shown by flow cytometry analysis. Moreover, via the expression of specific cardiac biomarkers, cardiac-specific cell functionality was confirmed. Our study depicted the heterocellular cardiac cell interactions, which is extremely important for the maintenance of normal physiology of the cardiac wall in vivo and significantly increased over a period of 21 days in in vitro. This 3D bioprinted "cardiac organoid" model can be adopted to simulate cardiac environments in which cellular crosstalk in diseased pathologies like cardiac atrophy can be studied in vitro and can further be used for drug cytotoxicity screening or underlying disease mechanisms.

Fabrication of chitosan/alginate/hydroxyapatite hybrid scaffolds using 3D printing and impregnating techniques for potential cartilage regeneration

Three-dimensional (3D) printed hydrogel scaffolds enhanced with ceramics have shown potential applications for cartilage regeneration, but leaving biological and mechanical properties to be desired. This paper presents our study on the development of chitosan /alginate scaffolds with nano hydroxyapatite (nHA) by combining 3D printing and impregnating techniques, forming a hybrid, yet novel, structure of scaffolds for potential cartilage regeneration. First, we incorporated nHA into chitosan scaffold printing and studied the printability by examining the difference between the printed scaffolds and their designs. Then, we impregnated alginate with nHA into the printed chitosan scaffolds to forming a hybrid structure of scaffolds; and then characterized the scaffolds mechanically and biologically, with a focus on identifying the influence of nHA and alginate for potential cartilage regeneration. The results of compression tests on the scaffolds showed that the inclusion of nHA increased the elastic moduli of scaffolds; while the live/dead assay illustrated that nHA had a great effect on improving attachment and viability of ATCD5 cells on the scaffolds. Also, our results illustrated scaffolds with nHA impregnated in alginate hydrogel enhanced the cell viability and attachment. Furthermore, antibacterial activity of hybrid scaffolds was characterized with results indicating that the chitosan scaffolds had favourable antibacterial ability, which was further enhanced with the impregnated nHA. Taken together, our study has illustrated that chitosan/HA/alginate hybrid scaffolds are promising for cartilage regeneration and the methods developed to create hybrid scaffolds based on 3D printing and impregnating techniques, which can also be extended to fabricating scaffolds for other tissue engineering applications.

Controlled and Local Delivery of Antibiotics by 3D Core/Shell Printed Hydrogel Scaffolds to Treat Soft Tissue Infections.

Soft tissue infections in open fractures or burns are major cause for high morbidity in trauma patients. Sustained, long-term and localized delivery of antimicrobial agents is needed for early eradication of these infections. Traditional (topical or systemic) antibiotic delivery methods are associated with a variety of problems, including their long-term unavailability and possible low local concentration. Novel approaches for antibiotic delivery via wound coverage/healing scaffolds are constantly being developed. Many of these approaches are associated with burst release and thus seldom maintain long-term inhibitory concentrations. Using 3D core/shell extrusion printing, scaffolds consisting of antibiotic depot (in the core composed of low concentrated biomaterial ink 3% alginate) surrounded by a denser biomaterial ink (shell) were fabricated. Denser biomaterial ink (composed of alginate and methylcellulose or alginate, methylcellulose and Laponite) retained scaffold shape and modulated antibiotic release kinetics. Release of antibiotics was observed over seven days, indicating sustained release characteristics and maintenance of potency. Inclusion of Laponite in shell, significantly reduced burst release of antibiotics. Additionally, the effect of shell thickness on release kinetics was demonstrated. Amalgamation of such a modular delivery system with other biofabrication methods could potentially open new strategies to simultaneously treat soft tissue infections and aid wound regeneration.

3D printed hydrogel scaffolds with macro pores and interconnected microchannel networks for tissue engineering vascularization

The macro pores and interconnected microchannels in three-dimensional (3D) scaffolds are important architecture cures to support new tissues growth and vascularization. To date, the fabrication of hydrogel scaffold possessing both designed macro pores and fully interconnected microchannel (FIM) networks is still a challenge. Herein, we reported a facile method to effectively fabricate hydrogel scaffold containing designed macro pores and FIM networks by 3D printing and surface crosslinking. The surface of the printed scaffold is crosslinked, while the inner parts of the filaments are still in uncrosslinked state, after soaking the scaffold in crosslinking solution for a certain time. Then, the FIM networks are generated by removing the uncrosslinked gels from the printed filaments. The created FIM scaffold shows improved mechanical properties and structural integrity after post treatment. The channel wall with barrier function endows the scaffold with the ability of fast perfusion of liquid in the microchannels. Human umbilical vein endothelial cells are well adhered on the inner surface of the microchannels with high cell viability. In vivo study shows the excellent performance to facilitate vessels formation not only in the interface zone between scaffolds and host tissue, but also in the center of the FIM scaffolds. It also demonstrate that FIM scaffolds hold the potential capability to promote wound healing. In conclusion, the present study proposes a facile method to fabricate hydrogel scaffolds with both macro pores and FIM networks, and demonstrates their strong potential for tissue engineering application.

Cryogenic 3D printed hydrogel scaffolds loading exosomes accelerate diabetic wound healing

Diabetic wounds represent a pressing concern affecting the health and quality of life of patients. Despite the continuous improvement in therapeutic strategy, diabetic wounds remain a worldwide challenge. Vascular dysfunction, in part due to hyperglycemia, is a well-identified factor contributing to inadequate healing in diabetic wounds. In the current study, we utilize an extrusion-based cryogenic 3D printing technology to construct decellularized small intestinal submucosa (SIS) combined with mesoporous bioactive glass (MBG) and exosomes to fabricate a produce a 3D scaffold dressing (SIS/MBG@Exos) which permits sustained release of bioactive exosomes. The SIS/MBG@Exos hydrogel scaffolds possess a good 3D structure with an suitable porosity, biocompatibility and hemostasis ability, which could promote the proliferation, migration and angiogenesis of Human umbilical vein endothelial cells (HUVECs). The results of diabetic wounds in vivo indicate that the SIS/MBG@Exos hydrogel scaffolds accelerate diabetic wound healing through increasing the blood flow of wounds and stimulating the angiogenesis process of the diabetic wound. The SIS/MBG@Exos hydrogel scaffolds also promote granulation tissue formation, well-organized collagen fiber deposition, functional new blood vessel growth, factors promoting wound healing. Taken together, this research presents a promising novel strategy for the treatment of diabetic wounds.

Multiscale porosity in a 3D printed gellan–gelatin composite for bone tissue engineering

The aim of this work was to develop a complex-shaped gelatin–gellan composite scaffold with multiscale porosity using a combination of cryogenic 3D printing and lyophilization for bone tissue engineering. Cryogenic 3D printing was used to fabricate a low-concentration composite of complex-shaped macroporous gelatin–gellan structures with a pore size of 919 ± 89 µm. This was followed by lyophilization to introduce micropores of size 20–250 µm and nanometre-level surface functionalities, thus achieving a hierarchical porous structure. These multiscale porous scaffolds (GMu) were compared with two other types of scaffolds having only microporosity (GMi) and macroporosity (GMa) with regard to their physical and in vitro biological properties. GMu scaffolds were found to be better than GMi and GMa in terms of swelling percentage, degradation rate, uniform pore distribution, cellular infiltration, attachment, proliferation, protein generation and mineralization. In conclusion, we have developed a controlled hierarchical bone-like structure, biomimicking natural bone, together with a reproducible process of manufacture by coupling soft hydrogel 3D printing with lyophilization. This enables the development of complex-shaped patient-specific 3D printed hydrogel scaffolds with enhanced performance in vitro and great potential in the fields of tissue engineering, bioprinting and regenerative medicine.

3D Printed Hydrogels with Aligned Microchannels to Guide Neural Stem Cell Migration.

Following traumatic or ischemic brain injury, rapid cell death and extracellular matrix degradation lead to the formation of a cavity at the brain lesion site, which is responsible for prolonged neurological deficits and permanent disability. Transplantation of neural stem/progenitor cells (NSCs) represents a promising strategy for reconstructing the lesion cavity and promoting tissue regeneration. In particular, the promotion of neuronal migration, organization, and integration of transplanted NSCs is critical to the success of stem cell-based therapy. This is particularly important for the cerebral cortex, the most common area involved in brain injuries, because the highly organized structure of the cerebral cortex is essential to its function. Biomaterials-based strategies show some promise for conditioning the lesion site microenvironment to support transplanted stem cells, but the progress in demonstrating organized cell engraftment and integration into the brain is very limited. An effective approach to sufficiently address these challenges has not yet been developed. Here, we have implemented a digital light-processing-based 3D printer and printed hydrogel scaffolds with a designed shape, uniaxially aligned microchannels, and tunable mechanical properties. We demonstrated the capacity to achieve high shape precision to the lesion site with brain tissue-matching mechanical properties. We also established spatial control of bioactive molecule distribution within 3D printed hydrogel scaffolds. These printed hydrogel scaffolds have shown high neuro-compatibility with aligned neuronal outgrowth along with the microchannels. This study will provide a biomaterial-based approach that can serve as a protective and guidance vehicle for transplanted NSC organization and integration for brain tissue regeneration after injuries.