Bioinspired 3D porous human placental derived extracellular matrix/silk fibroin sponges for accelerated bone regeneration

Decellularized Brain Extracellular Matrix Hydrogel Aids the Formation of Human Spinal-Cord Organoids Recapitulating the Complex Three-Dimensional Organization

The intricate electrophysiological functions and anatomical structures of spinal cord tissue render the establishment of in vitro models for spinal cord-related diseases highly challenging. Currently, both in vivo and in vitro models for spinal cord-related diseases are still underdeveloped, complicating the exploration and development of effective therapeutic drugs or strategies. Organoids cultured from human induced pluripotent stem cells (hiPSCs) hold promise as suitable in vitro models for spinal cord-related diseases. However, the cultivation of spinal cord organoids predominantly relies on Matrigel, a matrix derived from murine sarcoma tissue. Tissue-specific extracellular matrices are key drivers of complex organ development, thus underscoring the urgent need to research safer and more physiologically relevant organoid culture materials. Herein, we have prepared a rat decellularized brain extracellular matrix hydrogel (DBECMH), which supports the formation of hiPSC-derived spinal cord organoids. Compared with Matrigel, organoids cultured in DBECMH exhibited higher expression levels of markers from multiple compartments of the natural spinal cord, facilitating the development and maturation of spinal cord organoid tissues. Our study suggests that DBECMH holds potential to replace Matrigel as the standard culture medium for human spinal cord organoids, thereby advancing the development of spinal cord organoid culture protocols and their application in in vitro modeling of spinal cord-related diseases.

Human Placenta Decellularized Extracellular Matrix Hydrogel Promotes the Generation of Human Spinal Cord Organoids with Dorsoventral Organization from Human Induced Pluripotent Stem Cells

Spinal cord organoids are of significant value in the research of spinal cord-related diseases by simulating disease states, thereby facilitating the development of novel therapies. However, the complexity of spinal cord structure and physiological functions, along with the lack of human-derived inducing components, presents challenges in the in vitro construction of human spinal cord organoids. Here, we introduce a novel human decellularized placenta-derived extracellular matrix hydrogel (DPECMH) and, combined with a new induction protocol, successfully construct human spinal cord organoids. The human placenta-sourced decellularized extracellular matrix (dECM), verified through hematoxylin and eosin staining, DNA quantification, and immunofluorescence staining, retained essential ECM components such as elastin, fibronectin, type I collagen, laminin, and so forth. The temperature-sensitive hydrogel made from human placenta dECM demonstrated good biocompatibility and promoted the differentiation of human induced pluripotent stem cell (hiPSCs)-derived spinal cord organoids into neurons. It displayed enhanced expression of laminar markers in comparison to Matrigel and showed higher expression of laminar markers compared to Matrigel, accelerating the maturation process of spinal cord organoids and demonstrating its potential as an organoid culture substrate. DPECMH has the potential to replace Matrigel as the standard additive for human spinal cord organoids, thus advancing the development of spinal cord organoid culture protocols and their application in the in vitro modeling of spinal cord-related diseases.

Silk-Based 3D Porous Scaffolds for Tissue Engineering

Silk fibroin, extracted from the silk of the Bombyx mori silkworm, stands out as a biomaterial due to its nontoxic nature, excellent biocompatibility, and adjustable biodegradability. Porous scaffolds, a type of biomaterial, are crucial for creating an optimal microenvironment that supports cell adhesion and proliferation, thereby playing an essential role in tissue remodeling and repair. Therefore, this review focuses on 3D porous silk fibroin-based scaffolds, first summarizing their preparation methods and then detailing their regenerative effects on bone, cartilage, tendon, vascular, neural, skin, hepatic, and tracheal epithelial tissue engineering in recent years.

Silk fibroin-derived electrospun materials for biomedical applications: A review

Electrospinning is a versatile technique for fabricating polymeric fibers with diameters ranging from micro- to nanoscale, exhibiting multiple morphologies and arrangements. By combining silk fibroin (SF) with synthetic and/or natural polymers, electrospun materials with outstanding biological, chemical, electrical, physical, mechanical, and optical properties can be achieved, fulfilling the evolving biomedical demands. This review highlights the remarkable versatility of SF-derived electrospun materials, specifically focusing on their application in tissue regeneration (including cartilage, cornea, nerves, blood vessels, bones, and skin), disease treatment (such as cancer and diabetes), and the development of controlled drug delivery systems. Additionally, we explore the potential future trends in utilizing these nanofibrous materials for creating intelligent biomaterials, incorporating biosensors and wearable sensors for monitoring human health, and also discuss the bottlenecks for its widespread use. This comprehensive overview illuminates the significant impact and exciting prospects of SF-derived electrospun materials in advancing biomedical research and applications.

Decellularized extracellular matrix and silk fibroin-based hybrid biomaterials: A comprehensive review on fabrication techniques and tissue-specific applications

Biomaterials play a fundamental role in tissue engineering by providing biochemical and physical cues that influence cellular fate and matrix development. Decellularized extracellular matrix (dECM) as a biomaterial is distinguished by its abundant composition of matrix proteins, such as collagen, elastin, fibronectin, and laminin, as well as glycosaminoglycans and proteoglycans. However, the mechanical properties of only dECM-based constructs may not always meet tissue-specific requirements. Recent advancements address this challenge by utilizing hybrid biomaterials that harness the strengths of silk fibroin (SF), which contributes the necessary mechanical properties, while dECM provides essential cellular cues for in vitro studies and tissue regeneration. This review discusses emerging trends in developing such biopolymer blends, aiming to synergistically combine the advantages of SF and dECM through optimal concentrations and desired cross-linking density. We focus on different fabrication techniques and cross-linking methods that have been utilized to fabricate various tissue-engineered hybrid constructs. Furthermore, we survey recent applications of such biomaterials for the regeneration of various tissues, including bone, cartilage, trachea, bladder, vascular graft, heart, skin, liver, and other soft tissues. Finally, the trajectory and prospects of the constructs derived from this blend in the tissue engineering field have been summarized, highlighting their potential for clinical translation.

Synthesis and characterization of a silk fibroin/placenta matrix hydrogel for breast reconstruction

Reconstructive surgery is a complex and demanding interdisciplinary field. One of the major challenges is the production of sizeable, implantable, inexpensive bioprostheses such as breast implants. In this study, porous hybrid hydrogels were fabricated by a combinatorial method using decellularized human placenta (dHplacenta) and silk fibroin. Histology was used to confirm the acellularity of the dHplacenta. The physio-chemical properties of the hydrogels were evaluated using SEM, FTIR, and rheological assays. The synthesized hydrogels exhibited a uniform 3-D microstructure with an interconnected porous network, and the hybrid hydrogels with a 30/70 ratio had improved mechanical properties compared to the other hydrogels. Hybrid hydrogels were also cultured with adipose-derived mesenchymal stem cells (ADSCs). Liposuction was used to obtain adipose tissue from patients, which was then characterized using flow cytometry and karyotyping. The results showed that CD34 and CD31 were downregulated, whereas CD105 and CD90 were upregulated in ADSCs, indicating a phenotype resembling to that of mesenchymal stem cells from the human bone marrow. Moreover, after re-cellularized hydrogel, the live/dead assay and SEM analysis confirmed that most viability and cellular expansion on the hydrogels contained higher ratios of dHplacenta (30/70) than the other two groups. All these findings recapitulated that the 30/70 dHplacenta/silk fibroin hydrogel can perform as an excellent substrate for breast tissue engineering applications.

Silk fibroin scaffolds: A promising candidate for bone regeneration

It remains a big challenge in clinical practice to repair large-sized bone defects and many factors limit the application of autografts and allografts, The application of exogenous scaffolds is an alternate strategy for bone regeneration, among which the silk fibroin (SF) scaffold is a promising candidate. Due to the advantages of excellent biocompatibility, satisfying mechanical property, controllable biodegradability and structural adjustability, SF scaffolds exhibit great potential in bone regeneration with the help of well-designed structures, bioactive components and functional surface modification. This review will summarize the cell and tissue interaction with SF scaffolds, techniques to fabricate SF-based scaffolds and modifications of SF scaffolds to enhance osteogenesis, which will provide a deep and comprehensive insight into SF scaffolds and inspire the design and fabrication of novel SF scaffolds for superior osteogenic performance. However, there still needs more comprehensive efforts to promote better clinical translation of SF scaffolds, including more experiments in big animal models and clinical trials. Furthermore, deeper investigations are also in demand to reveal the degradation and clearing mechanisms of SF scaffolds and evaluate the influence of degradation products.

Green tea catechin-grafted silk fibroin hydrogels with reactive oxygen species scavenging activity for wound healing applications

BACKGROUND

Overproduction of reactive oxygen species (ROS) is known to delay wound healing by causing oxidative tissue damage and inflammation. The green tea catechin, (-)-Epigallocatechin-3-O-gallate (EGCG), has drawn a great deal of interest due to its strong ROS scavenging and anti-inflammatory activities. In this study, we developed EGCG-grafted silk fibroin hydrogels as a potential wound dressing material.

METHODS

The introduction of EGCG to water-soluble silk fibroin (SF-WS) was accomplished by the nucleophilic addition reaction between lysine residues in silk proteins and EGCG quinone at mild basic pH. The resulting SF-EGCG conjugate was co-crosslinked with tyramine-substituted SF (SF-T) via horseradish peroxidase (HRP)/H2O2 mediated enzymatic reaction to form SF-T/SF-EGCG hydrogels with series of composition ratios.

RESULTS

Interestingly, SF-T70/SF-EGCG30 hydrogels exhibited rapid in situ gelation (< 30 s), similar storage modulus to human skin (≈ 1000 Pa) and superior wound healing performance over SF-T hydrogels and a commercial DuoDERM® gel dressings in a rat model of full thickness skin defect.

CONCLUSION

This study will provide useful insights into a rational design of ROS scavenging biomaterials for wound healing applications.

Recent advances in biofunctional guided bone regeneration materials for repairing defective alveolar and maxillofacial bone: A review

The anatomy of the oral and maxillofacial sites is complex, and bone defects caused by trauma, tumors, and inflammation in these zones are extremely difficult to repair. Among the most effective and reliable methods to attain osteogenesis, the guided bone regeneration (GBR) technique is extensively applied in defective oral and maxillofacial GBR. Furthermore, endowing biofunctions is crucial for GBR materials applied in repairing defective alveolar and maxillofacial bones. In this review, recent advances in designing and fabricating GBR materials applied in oral and maxillofacial sites are classified and discussed according to their biofunctions, including maintaining space for bone growth; facilitating the adhesion, migration, and proliferation of osteoblasts; facilitating the migration and differentiation of progenitor cells; promoting vascularization; providing immunoregulation to induce osteogenesis; suppressing infection; and effectively mimicking natural tissues using graded biomimetic materials. In addition, new processing strategies (e.g., 3D printing) and new design concepts (e.g., developing bone mimetic extracellular matrix niches and preparing scaffolds to suppress connective tissue to actively acquire space for bone regeneration), are particularly worthy of further study. In the future, GBR materials with richer biological functions are expected to be developed based on an in-depth understanding of the mechanism of bone-GBR-material interactions.

Mimicking the Natural Basement Membrane for Advanced Tissue Engineering

Advancements in the field of tissue engineering have led to the elucidation of physical and chemical characteristics of physiological basement membranes (BM) as specialized forms of the extracellular matrix. Efforts to recapitulate the intricate structure and biological composition of the BM have encountered various advancements due to its impact on cell fate, function, and regulation. More attention has been paid to synthesizing biocompatible and biofunctional fibrillar scaffolds that closely mimic the natural BM. Specific modifications in biomimetic BM have paved the way for the development of in vitro models like alveolar-capillary barrier, airway models, skin, blood-brain barrier, kidney barrier, and metastatic models, which can be used for personalized drug screening, understanding physiological and pathological pathways, and tissue implants. In this Review, we focus on the structure, composition, and functions of in vivo BM and the ongoing efforts to mimic it synthetically. Light has been shed on the advantages and limitations of various forms of biomimetic BM scaffolds including porous polymeric membranes, hydrogels, and electrospun membranes This Review further elaborates and justifies the significance of BM mimics in tissue engineering, in particular in the development of in vitro organ model systems.

Updates in immunocompatibility of biomaterials: applications for regenerative medicine

INTRODUCTION

Biomaterials, either metallic, ceramic, or polymeric, can be used in medicine as a part of the implants, dialysis membranes, bone scaffolds, or components of artificial organs. Polymeric biomaterials cover a vast range of biomedical applications. The biocompatibility and immunocompatibility of polymeric materials are of fundamental importance for their possible therapeutic uses, as the immune system can intervene in the materials' performance. Therefore, based on application, different routes can be utilized for immunoregulation.

AREAS COVERED

As different biomaterials can be modulated by different strategies, this study aims to summarize and evaluate the available methods for the immunocompatibility enhancement of more common polymeric biomaterials based on their nature. Different strategies such as surface modification, physical characterization, and drug incorporation are investigated for the immunomodulation of nanoparticles, hydrogels, sponges, and nanofibers.

EXPERT OPINION

Recently, strategies for triggering appropriate immune responses by functional biomaterials have been highlighted. As most strategies correspond to the physical and surface properties of biomaterials, specific modulation can be conducted for each biomaterial system. Besides, different applications require different modulations of the immune system. In the future, the selection of novel materials and immune regulators can play a role in tuning the immune system for regenerative medicine.

Demineralized and decellularized bone extracellular matrix-incorporated electrospun nanofibrous scaffold for bone regeneration

Extracellular matrix (ECM)-based materials have been employed as scaffolds for bone tissue engineering, providing a suitable microenvironment with biophysical and biochemical cues for cell attachment, proliferation and differentiation. In this study, bone-derived ECM (bECM)-incorporated electrospun poly(ε-caprolactone) (PCL) (bECM/PCL) nanofibrous scaffolds were prepared and their effects on osteogenesis were evaluated in vitro and in vivo. The results showed that the bECM/PCL scaffolds promoted the attachment, spreading, proliferation and osteogenic differentiation of rat mesenchymal stem cells (MSCs), mitigated the foreign-body reaction, and facilitated bone regeneration in a rat calvarial critical size defect model. Thus, this study suggests that bECM can provide a promising option for bone regeneration.

Estimating Kinetic Rate Parameters for Enzymatic Degradation of Lyophilized Silk Fibroin Sponges

Sponge-like biomaterials formed from silk fibroin are promising as degradable materials in clinical applications due to their controllable breakdown into simple amino acids or small peptides in vivo. Silk fibroin, isolated from Bombyx mori silkworm cocoons, can be used to form sponge-like materials with a variety of tunable parameters including the elastic modulus, porosity and pore size, and level of nanocrystalline domains. These parameters can be independently tuned during formulation resulting in a wide parameter space and set of final materials. Determining the mechanism and rate constants for biomaterial degradation of these tunable silk materials would allow scientists to evaluate and predict the biomaterial performance for the large array of tissue engineering applications and patient ailments a priori. We first measured in vitro degradation rates of silk sponges using common protein-degrading enzymes such as Proteinase K and Protease XIV. The concentration of the enzyme in solution was varied (1, 0.1, 0.01 U/mL) along with one silk sponge formulation parameter: the level of crystallinity within the sponge. Additionally, two experimental degradation methods were evaluated, termed continuous and discrete degradation methods. Silk concentration, polymer chain length and scaffold pore size were held constant during experimentation and kinetic parameter estimation. Experimentally, we observed that the enzyme itself, enzyme concentration within the bulk solution, and the sponge fabrication water annealing time were the major experimental parameters dictating silk sponge degradation in our experimental design. We fit the experimental data to two models, a Michaelis-Menten kinetic model and a modified first order kinetic model. Weighted, non-linear least squares analysis was used to determine the parameters from the data sets and Monte-Carlo simulations were utilized to obtain estimates of the error. We found that modified first order reaction kinetics fit the time-dependent degradation of lyophilized silk sponges and we obtained first order-like rate constants. These results represent the first investigations into determining kinetic parameters to predict lyophilized silk sponge degradation rates and can be a tool for future mathematical representations of silk biomaterial degradation.

Tissue Engineering for Mimics and Modulations of Immune Functions

In the field of regenerative medicine, advances in tissue engineering have surpassed the reconstruction of individual tissues or organs and begun to work towards engineering systemic factors such as immune objects and functions. The immune system plays a crucial role in protecting and regulating systemic functions in the human body. Engineered immune tissues and organs have shown potential in recovering dysfunctions and aplasia of the immune system and the evasion from immune-mediated inflammatory responses and rejection elicited by engineered implants from allogeneic or xenogeneic sources are also being pursued to facilitate clinical transplantation of tissue engineered grafts. Here, current progress in tissue engineering to mimic or modulate immune functions is reviewed and elaborated from two perspectives: 1) engineering of immune tissues and organs per se and 2) immune evasion of host immunoinflammatory rejection by tissue-engineered implants.