Collagen and nano-hydroxyapatite interactions in alginate-based microcapsule provide an appropriate osteogenic microenvironment for modular bone tissue formation

Magnetically responsive micro-clustered calcium phosphate-reinforced cell-laden microbead sodium alginate hydrogel for accelerated osteogenic tissue regeneration

The rising prevalence of bone injuries has increased the demand for minimally invasive treatments. Microbead hydrogels, renowned for cell encapsulation, provide a versatile substrate for bone tissue regeneration. They deliver bioactive agents, support cell growth, and promote osteogenesis, aiding bone repair and regeneration. In this study, we synthesized superparamagnetic iron oxide nanoparticles (Sp) coated with a calcium phosphate layer (m-Sp), achieving a distinctive flower-like micro-cluster morphology. Subsequently, sodium alginate (SA) microbead hydrogels containing m-Sp (McSa@m-Sp) were fabricated using a dropping gelation strategy. McSa@m-Sp is magnetically targetable, enhance cross-linking, control degradation rates, and provide strong antibacterial activity. Encapsulation studies with MC3T3-E1 cells revealed enhanced viability and proliferation. These studies also indicated significantly elevated alkaline phosphatase (ALP) activity and mineralization in MC3T3-E1 cells, as confirmed by Alizarin Red S (ARS) and Von Kossa staining, along with increased collagen production within the McSa@m-Sp microbead hydrogels. Immunocytochemistry (ICC) and gene expression studies supported the osteoinductive potential of McSa@m-Sp, showing increased expression of osteogenic markers including RUNX-2, collagen-I, osteopontin, and osteocalcin. Thus, McSa@m-Sp microbead hydrogels offer a promising strategy for multifunctional scaffolds in bone tissue engineering.

Hybrid scaffolds for bone tissue engineering: Integration of composites and bioactive hydrogels loaded with hDPSCs

Bone tissue regeneration remains a significant challenge in clinical settings due to the complexity of replicating the mechanical and biological properties of bone environment. This study addresses this challenge by proposing a hybrid scaffold designed to enhance both bioactivity and physical stability for bone tissue regeneration. This research is the fisrt to develop a rigid 3D structure composed of polycaprolactone (PCL) and hydroxyapatite nanoparticles (nHA) integrated with a bioink containing human dental pulp stem/stromal cells (hDPSCs), alginate, nHA and collagen (Col). The biofabricated constructs were extensively characterized through cytocompatibility tests, osteogenic differentiation assessment, and biocompatibility evaluation in a rat model. In vitro results demontrated that the hybrid scaffolds presented significantly higher cell viability after 168 h compared to the control group. Furthermore, the hybrid scaffolds showed increased osteogenic differentiation relative to other groups. In vivo evaluation indicated good biocompatibility, characterized by minimal inflammatory response and successful tissue integration. These findings highlight the scaffold's potential to support bone tissue regeneration by combining the mechanical strength of PCL and nHA with the biological activity of the alginate-nHA-Col and hDPSCs bioink. The current study provides a promising foundation for the development of biomaterials aimed at improving clinical outcomes in bone repair and regeneration, particulary for the treatment of critical-size bone defects, targeted drug administration, and three-dimensional models for bone tissue engineering.

Research Progress in Hydrogels for Cartilage Organoids

The repair and regeneration of cartilage has always been a hot topic in medical research. Cartilage organoids (CORGs) are special cartilage tissue created using tissue engineering techniques outside the body. These engineered organoids tissues provide models that simulate the complex biological functions of cartilage, opening new possibilities for cartilage regenerative medicine and treatment strategies. However, it is crucial to establish suitable matrix scaffolds for the cultivation of CORGs. In recent years, utilizing hydrogel to culture stem cells and induce their differentiation into chondrocytes has emerged as a promising method for the in vitro construction of CORGs. In this review, the methods for establishing CORGs are summarized and an overview of the advantages and limitations of using matrigel in the cultivation of such organoids is provided. Furthermore, the importance of cartilage tissue ECM and alternative hydrogel substitutes for Matrigel, such as alginate, peptides, silk fibroin, and DNA derivatives is discussed, and the pros and cons of using these hydrogels for the cultivation of CORGs are outlined. Finally, the challenges and future directions in hydrogel research for CORGs are discussed. It is hoped that this article provides valuable references for the design and development of hydrogels for CORGs.

An enzymatically crosslinked collagen type II/hyaluronic acid hybrid hydrogel: A biomimetic cell delivery system for cartilage tissue engineering

This study presents new injectable hydrogels based on hyaluronic acid and collagen type II that mimic the polysaccharide-protein structure of natural cartilage. After collagen isolation from chicken sternal cartilage, tyramine-grafted hyaluronic acid and collagen type II (HA-Tyr and COL-II-Tyr) were synthesized. Hybrid hydrogels were prepared with different ratios of HA-Tyr/COL-II-Tyr using horseradish peroxidase and noncytotoxic concentrations of hydrogen peroxide to encapsulate human bone marrow-derived mesenchymal stromal cells (hBM-MSCs). The findings showed that a higher HA-Tyr content resulted in a higher storage modulus and a lower hydrogel shrinkage, resulting in hydrogel swelling. Incorporating COL-II-Tyr into HA-Tyr hydrogels induced a more favorable microenvironment for hBM-MSCs chondrogenic differentiation. Compared to HA-Tyr alone, the hybrid HA-Tyr/COL-II-Tyr hydrogel promoted enhanced chondrocyte adhesion, spreading, proliferation, and upregulation of cartilage-related gene expression. These results highlight the promising potential of injectable HA-Tyr/COL-II-Tyr hybrid hydrogels to deliver cells for cartilage regeneration.

Platelet-rich fibrin (PRF) modified nano-hydroxyapatite/chitosan/gelatin/alginate scaffolds increase adhesion and viability of human dental pulp stem cells (DPSC) and osteoblasts derived from DPSC

Bone tissue regeneration strategies have incorporated the use of natural polymers, such as hydroxyapatite (nHA), chitosan (CH), gelatin (GEL), or alginate (ALG). Additionally, platelet concentrates, such as platelet-rich fibrin (PRF) have been suggested to improve scaffold biocompatibility. This study aimed to develop scaffolds composed of nHA, GEL, and CH, with or without ALG and lyophilized PRF, to evaluate the scaffold's properties, growth factor release, and dental pulp stem cells (DPSC), and osteoblast (OB) derived from DPSC viability. Four scaffold variations were synthesized and lyophilized. Then, degradation, swelling profiles, and morphological analysis were performed. Furthermore, PDGF-BB and FGF-B growth factors release were quantified by ELISA, and cytotoxicity and cell viability were evaluated. The swelling and degradation profiles were similar in all scaffolds, with pore sizes ranging between 100 and 250 μm. FGF-B and PDGF-BB release was evidenced after 24 h of scaffold immersion in cell culture medium. DPSC and OB-DPSC viability was notably increased in PRF-supplemented scaffolds. The nHA-CH-GEL-PRF scaffold demonstrated optimal physical-biological characteristics for stimulating DPSC and OB-DPSC cell viability. These results suggest lyophilized PRF improves scaffold biocompatibility for bone tissue regeneration purposes.

Droplet Microfluidics Powered Hydrogel Microparticles for Stem Cell-Mediated Biomedical Applications

Stem cell-related therapeutic technologies have garnered significant attention of the research community for their multi-faceted applications. To promote the therapeutic effects of stem cells, the strategies for cell microencapsulation in hydrogel microparticles have been widely explored, as the hydrogel microparticles have the potential to facilitate oxygen diffusion and nutrient transport alongside their ability to promote crucial cell-cell and cell-matrix interactions. Despite their significant promise, there is an acute shortage of automated, standardized, and reproducible platforms to further stem cell-related research. Microfluidics offers an intriguing platform to produce stem cell-laden hydrogel microparticles (SCHMs) owing to its ability to manipulate the fluids at the micrometer scale as well as precisely control the structure and composition of microparticles. In this review, the typical biomaterials and crosslinking methods for microfluidic encapsulation of stem cells as well as the progress in droplet-based microfluidics for the fabrication of SCHMs are outlined. Moreover, the important biomedical applications of SCHMs are highlighted, including regenerative medicine, tissue engineering, scale-up production of stem cells, and microenvironmental simulation for fundamental cell studies. Overall, microfluidics holds tremendous potential for enabling the production of diverse hydrogel microparticles and is worthy for various stem cell-related biomedical applications.

Sandwich hydrogel to realize cartilage-mimetic structures and performances from polyvinyl alcohol, chitosan and sodium hyaluronate

Developing artificial substitutes that mimic the structures and performances of natural cartilage is of great importance. However, it is challenging to integrate the high strength, excellent biocompatibility, low coefficient of friction, long-term wear resistance, outstanding swelling resistance, and osseointegration potential into one material. Herein, a sandwich hydrogel with cartilage-mimetic structures and performances was prepared to achieve this goal. The precursor hydrogel was obtained by freezing-thawing the mixture of poly vinyl alcohol, chitosan and deionized water three cycles, accompanied by soaking in sodium hyaluronate solution. The top of the precursor hydrogel was hydrophobically modified with lauroyl chloride and then loaded with lecithin, while the bottom was mineralized with hydroxyapatite. Due to the multiple linkages (crystalline domains, hydrogen bonds, and ionic interactions), the compressive stress was 71 MPa. Owing to the synergy of the hydrophobic modification and lecithin, the coefficient of friction was 0.01. Additionally, no wear trace was observed after 50,000 wear cycles. Remarkably, hydroxyapatite enabled the hydrogel osseointegration potential. The swelling ratio of the hydrogel was 0.06 g/g after soaking in simulated synovial fluid for 7 days. Since raw materials were non-toxic, the cell viability was 100 %. All of the above merits make it an ideal material for cartilage replacement.

Novel Calcium-Binding Peptide from Bovine Bone Collagen Hydrolysates and Its Potential Pro-Osteogenic Activity via Calcium-Sensing Receptor (CaSR)

SCOPE

This paper aims to explore the osteogenic activity and potential mechanism of the peptide-calcium chelate, and provides a theoretical basis for peptide-calcium chelates as functional foods to prevent or improve osteoporosis.

METHODS AND RESULTS

In this research, a novel peptide (Phe-Gly-Leu, FGL) with a high calcium-binding capacity is screened from bovine bone collagen hydrolysates (CPs), calcium binding sites of which mainly included carbonyl, amino and carboxyl groups. The FGL-Ca significantly enhances the osteogenic activity of MC3T3-E1 cells (survival rate, differentiation, and mineralization). The results of calcium fluorescence labeling and molecular docking show that FGL-Ca may activate calcium-sensing receptor (CaSR), leading to an increase in intracellular calcium concentration, then enhancing osteogenic activity of MC3T3-E1 cells. Further research found that FGL-Ca significantly promotes the mRNA and protein expression levels of CaSR, transforming growth factor β (TGF-β1), TGF-β-type II receptor (TβRII), Smad2, Smad3, osteocalcin (OCN), alkaline phosphatase (ALP), osteoprotegrin (OPG), and collagen type I (COLI). Subsequently, in the signal pathway intervention experiment, the expression levels of genes and proteins related to the TGF-β1/Smad2/3 signaling pathway that are promoted by FGL-Ca are found to decrease.

CONCLUSIONS

These results suggest that FGL-Ca may activate CaSR, increase intracellular calcium concentration, and activate TGF-β1/Smad2/3 signaling pathway, which may be one of the potential mechanisms for enhancing osteogenic activity.

Phosphorylation modification of bovine bone collagen peptide enhanced its effect on mineralization of MC3T3-E1 cells via improving calcium-binding capacity

This study aimed to investigate the effect of phosphorylation modification of collagen peptide on its calcium-binding capacity and pro-mineralization activity. In this study, collagen peptide (Leu-Thr-Phe, LTF) and phosphorylated LTF (P-LTF) were synthesized and further chelated with calcium ions. The results showed that phosphorylation of LTF significantly enhanced its calcium-binding capacity. Spectra analysis revealed that the calcium-binding sites of P-LTF were mainly carbonyl, carboxyl, and phosphate groups. Molecular docking further demonstrated that the phosphate group introduced by phosphorylation enhanced the calcium-binding capacity of LTF by ionic bonds and coordination bonds. The stability analysis results suggested that intestinal fluid could repair the peptide-calcium complex destroyed by gastric fluid. The cell experiment displayed that P-LTF-Ca significantly improved the mineralization activity of MC3T3-E1 cells, and the order of effective influence was P-LTF-Ca > LTF-Ca > P-LTF > LTF. This study provided the theoretical basis for the potential application of phosphorylation modification in improving bone health.

Harnessing Natural Polymers for Nano-Scaffolds in Bone Tissue Engineering: A Comprehensive Overview of Bone Disease Treatment

Numerous surgeries are carried out to replace tissues that have been harmed by an illness or an accident. Due to various surgical interventions and the requirement of bone substitutes, the emerging field of bone tissue engineering attempts to repair damaged tissues with the help of scaffolds. These scaffolds act as template for bone regeneration by controlling the development of new cells. For the creation of functional tissues and organs, there are three elements of bone tissue engineering that play very crucial role: cells, signals and scaffolds. For the achievement of these aims, various types of natural polymers, like chitosan, chitin, cellulose, albumin and silk fibroin, have been used for the preparation of scaffolds. Scaffolds produced from natural polymers have many advantages: they are less immunogenic as well as being biodegradable, biocompatible, non-toxic and cost effective. The hierarchal structure of bone, from microscale to nanoscale, is mostly made up of organic and inorganic components like nanohydroxyapatite and collagen components. This review paper summarizes the knowledge and updates the information about the use of natural polymers for the preparation of scaffolds, with their application in recent research trends and development in the area of bone tissue engineering (BTE). The article extensively explores the related research to analyze the advancement of nanotechnology for the treatment of bone-related diseases and bone repair.

Recent advances in biopolymer-based hydrogels and their potential biomedical applications

Hydrogels are three-dimensional networks of polymer chains containing large amounts of water in their structure. Hydrogels have received significant attention in biomedical applications owing to their attractive physicochemical properties, including flexibility, softness, biodegradability, and biocompatibility. Different natural and synthetic polymers have been intensely explored in developing hydrogels for the desired applications. Biopolymers-based hydrogels have advantages over synthetic polymers regarding improved cellular activity and weak immune response. These properties can be further improved by grafting with other polymers or adding nanomaterials, and they structurally mimic the living tissue environments, which opens their broad applicability. The hydrogels can be physically or chemically cross-linked depending on the structure. The use of different biopolymers-based hydrogels in biomedical applications has been reviewed and discussed earlier. However, no report is still available to comprehensively introduce the synthesis, advantages, disadvantages, and biomedical applications of biopolymers-based hydrogels from the material point of view. Herein, we systematically overview different synthesis methods of hydrogels and provide a holistic approach to biopolymers-based hydrogels for biomedical applications, especially in bone regeneration, wound healing, drug delivery, bioimaging, and therapy. The current challenges and prospects of biopolymers-based hydrogels are highlighted rationally, giving an insight into the progress of these hydrogels and their practical applications.

Phenolated alginate hydrogel induced osteogenic properties of mesenchymal stem cells via Wnt signaling pathway

Osteogenic properties of phenolated alginate (1.2 %) hydrogel containing collagen (0.5 %)/nano-hydroxyapatite (1 %) were studied on human mesenchymal stem cells in vitro. The phenolation rate and physical properties of the hydrogel were assessed using nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), swelling ratio, gelation time, mechanical assay, and degradation rate. The viability of encapsulated cells was monitored on days 7, 14, and 21 using an MTT assay. Osteoblast differentiation was studied using western blotting, and real-time PCR. Using PCR array analysis, the role of the Wnt signaling pathway was also investigated. Data showed that the combination of alginate/collagen/nanohydroxyapatite yielded proper mechanical features. The addition of nanohydroxyapatite, and collagen reduced degradation, swelling rate coincided with increased stiffness. Elasticity and pore size were also diminished. NMR and FTIR revealed suitable incorporation of collagen and nanohydroxyapatite in the structure of alginate. Real-time PCR analysis and western blotting indicated the expression of osteoblast-related genes such as Runx2 and osteocalcin. PCR array revealed the induction of numerous genes related to Wnt signaling pathways during the maturation of human stem cells toward osteoblast-like cells. In vivo data indicated that transplantation of phenolated alginate/collagen/nanohydroxyapatite hydrogel led to enhanced de novo bone formation in rats with critical-sized calvarial defects. Phenolated alginate hydrogel can promote the osteogenic capacity of human amniotic membrane mesenchymal stem cells in the presence of nanohydroxyapatite and collagen via engaging the Wnt signaling pathway.

Functionalization of biomimetic mineralized collagen for bone tissue engineering

Mineralized collagen (MC) is the basic unit of bone structure and function and is the main component of the extracellular matrix (ECM) in bone tissue. In the biomimetic method, MC with different nanostructures of neo-bone have been constructed. Among these, extra-fibrous MC has been approved by regulatory agencies and applied in clinical practice to play an active role in bone defect repair. However, in the complex microenvironment of bone defects, such as in blood supply disorders and infections, MC is unable to effectively perform its pro-osteogenic activities and needs to be functionalized to include osteogenesis and the enhancement of angiogenesis, anti-infection, and immunomodulation. This article aimed to discuss the preparation and biological performance of MC with different nanostructures in detail, and summarize its functionalization strategy. Then we describe the recent advances in the osteo-inductive properties and multifunctional coordination of MC. Finally, the latest research progress of functionalized biomimetic MC, along with the development challenges and future trends, are discussed. This paper provides a theoretical basis and advanced design philosophy for bone tissue engineering in different bone microenvironments.

A bifunctional bortezomib-loaded porous nano-hydroxyapatite/alginate scaffold for simultaneous tumor inhibition and bone regeneration

Treatments of osteolytic lesions due to malignant metastasis remain one of the major clinical challenges. The residual tumor cells after surgical resections and an acidic tumor microenvironment are unfavorable for osteogenic induction. Bortezomib (BTZ), a proteasome inhibitor used in chemotherapy, also has an osteogenic potential in concentration- and Ca²⁺-dependent manners. In this study, controlled delivery of BTZ in a novel bifunctional scaffold based on nano-hydroxyapatite (nHA) and sodium alginate (SA) nanocomposite, namely BTZ/nHA@SA, has been explored. By smartly adjusting microenvironments, a sustainable release of Ca²⁺ from nHA could be achieved, which was not only able to cross-link SA but also to regulate the switch between the dual functions of tumor inhibition and bone regeneration of BTZ to promote the osteogenic pathway. The freeze-dried BTZ/nHA@SA scaffold has excellent interconnectivity, is capable to promote the attachment and proliferation of mouse embryonic osteoblast precursor cells, as well as effectively induces breast cancer cell death in vitro. Furthermore, in vivo, studies using a mouse tumor model and a rabbit femoral defect model showed that the BTZ/nHA@SA scaffold could promote tumor ablation, and also enhance bone repair. Therefore, the BTZ/nHA@SA scaffold has unique dual functions of inhibiting tumor recurrence and promoting bone tissue regeneration simultaneously. This smart bi-functional scaffold offers a promising novel approach for oncological treatments by synchronously orchestrating tumor inhibition and tissue regeneration for the repair of neoplastic bone defects.

Advanced Composites Inspired by Biological Structures and Functions in Nature: Architecture Design, Strengthening Mechanisms, and Mechanical-Functional Responses

The natural design and coupling of biological structures are the root of realizing the high strength, toughness, and unique functional properties of biomaterials. Advanced architecture design is applied to many materials, including metal materials, inorganic nonmetallic materials, polymer materials, and so on. To improve the performance of advanced materials, the designed architecture can be enhanced by bionics of biological structure, optimization of structural parameters, and coupling of multiple types of structures. Herein, the progress of structural materials is reviewed, the strengthening mechanisms of different types of structures are highlighted, and the impact of architecture design on the performance of advanced materials is discussed. Architecture design can improve the properties of materials at the micro level, such as mechanical, electrical, and thermal conductivity. The synergistic effect of structure makes traditional materials move toward advanced functional materials, thus enriching the macroproperties of materials. Finally, the challenges and opportunities of structural innovation of advanced materials in improving material properties are discussed.

Preparation of Cell-Loaded Microbeads as Stable and Injectable Delivery Platforms for Tissue Engineering

Cell transplants in therapeutic studies do not preserve their long-term function inside the donor body. In mesenchymal stem cell (MSC) transplants, transplanted cells disperse through the body and are prone to degradation by immune cells after the transplant process. Various strategies, such as usage of the immunosuppressive drugs to eliminate allograft rejection, are designed to increase the efficiency of cell therapy. Another strategy is the construction of biomimetic encapsulates using polymeric materials, which isolate stem cells and protect them from environmental effects. In this study, fibroblasts (L929) and MSCs were investigated for their improved viability and functionality once encapsulated inside the alginate microbeads under in vitro conditions for up to 12 days of incubation. Thus, uniform and injectable (<200 µm) cell-loaded microbeads were constructed by the electrostatically assisted spraying technique. Results showed that both L929 and MSCs cells continue their metabolic activity inside the microbeads during the incubation periods. Glucose consumption and lactic acid production levels of both cell lines were consistently observed. The released cell number on day 12 was found to be increased compared to day 0. Protein expression levels of both groups increased every day with the expected doubling rate. Hence, this strategy with a simple yet clever design to encapsulate either MSCs or L929 cells might outstand as a potential cell delivery platform for cell therapy-based tissue engineering.

Application of mesenchymal stem cell sheet for regeneration of craniomaxillofacial bone defects

Bone defects are among the most common damages in human medicine. Due to limitations and challenges in the area of bone healing, the research field has turned into a hot topic discipline with direct clinical outcomes. Among several available modalities, scaffold-free cell sheet technology has opened novel avenues to yield efficient osteogenesis. It is suggested that the intact matrix secreted from cells can provide a unique microenvironment for the acceleration of osteoangiogenesis. To the best of our knowledge, cell sheet technology (CST) has been investigated in terms of several skeletal defects with promising outcomes. Here, we highlighted some recent advances associated with the application of CST for the recovery of craniomaxillofacial (CMF) in various preclinical settings. The regenerative properties of both single-layer and multilayer CST were assessed regarding fabrication methods and applications. It has been indicated that different forms of cell sheets are available for CMF engineering like those used for other hard tissues. By tackling current challenges, CST is touted as an effective and alternative therapeutic option for CMF bone regeneration.

Thermosensitive and biodegradable PCL-based hydrogels: potential scaffolds for cartilage tissue engineering

Due to a lack of sufficient blood supply and unique physicochemical properties, the treatment of injured cartilage is laborious and needs an efficient strategy. Unfortunately, most of the current therapeutic approaches are, but not completely, unable to restore the function of injured cartilage. Tissue engineering-based modalities are an alternative option to reconstruct the injured tissue. Considering the unique structure and consistency of cartilage tissue (osteochondral junction), it is mandatory to apply distinct biomaterials with unique properties slightly different from scaffolds used for soft tissues. PCL is extensively used for the fabrication of fine therapeutic scaffolds to accelerate the restorative process. Thermosensitive PCL hydrogels with distinct chemical compositions have paved the way for sophisticated cartilage regeneration. This review aimed to collect recent findings regarding the application of PCL in hydrogels blended with natural, synthetic materials in the context of cartilage healing.

A CS-based composite scaffold with excellent photothermal effect and its application in full-thickness skin wound healing

The development of natural polymer-based scaffolds with excellent biocompatibility, antibacterial activity, and blood compatibility, able to facilitate full-thickness skin wound healing, remains challenging. In this study, we have developed three chitosan (CS)-based porous scaffolds, including CS, CS/CNT (carbon nanotubes) and CS/CNT/HA (nano-hydroxyapatite, n-HA) using a freeze-drying method. All three scaffolds have a high swelling ratio, excellent antibacterial activity, outstanding cytocompatibility and blood compatibility in vitro. The introduction of CNTs exhibited an obvious increase in mechanical properties and exerts excellent photothermal response, which displays excellent healing performance as a wound dressing in mouse full-thickness skin wound model when compared to CS scaffolds. CS/CNT/HA composite scaffolds present the strongest ability to promote full-thickness cutaneous wound closure and skin regeneration, which might be ascribed to the synergistic effect of photothermal response from CNT and excellent bioactivity from n-HA. Overall, the present study indicated that CNT and n-HA can be engineered as effective constituents in wound dressings to facilitate full-thickness skin regeneration.

Combination of polyglycerol sebacate coated with collagen for vascular engineering

Introduction: Here, we monitored the cytocompatibility of scaffolds consisting of poly (glycerol sebacate) (PGS) coated with collagen (Col) for endothelial cell activity after 72 hours. Methods: Human endothelial cells were allocated into Control, PGS, and PGS+Col groups. Scaffolds were characterized using FTIR and HNMR spectroscopy. Contact angel analysis and SEM were used to study wettability, surface morphology, and cell attachment. Cell survival was assessed using LDH leakage assay. Levels of Tie-1, Tie-2, VE-Cadherin, and VEGFR-2 were measured using western blotting and real-time PCR. Results: FTIR and HNMR analyses revealed the proper blending in PGS+Col group. SEM imaging exhibited a flat surface in the PGS group while thin Col fibers were detected in PGS+Col surface. The addition of Col to the PGS reduced the contract angle values from 97.3˚ to 81.1˚. Compared to PGS substrate alone, in PGS+Col group, cells appropriately attached to the surface. PGS and PGS+Col did not alter the leakage of LDH to the supernatant compared to control cells, showing the cytocopatiblity of PGS-based scaffolds. SOD and NO levels were increased significantly in PGS (p<0.05) and PGS+Col groups (p<0.001), respectively. We found that PGS+Col decreased Tie-1 content in endothelial cells whereas protein levels of Tie-2 and VE-Cadherin and expression of VEGFR-2 remained unchanged compared to PGS and control groups. Conclusion: Simultaneous application of Col and PGS can stimulate normal endothleial cell morphology without the alteration of tyrosine kinases receptors and cadherin.

Revisable and high-strength wheel-spun alginate/graphene oxide based fibrous rods towards a flexible and biodegradable rib internal fixation system

The intramedullary splint insertion fixation system is the mainstream clinical solution to severe rib fractures. However, the titanium alloy scaffolds have limitations in biocompatibility, flexibility and complexity of surgeries. Here we present a revisable wheel-spun alginate (Alg)/graphene oxide (GO)-based fibrous rod as a potential alternative for a rib internal fixation system. The reversible fusion and fission capability was obtained by optimized Alg/GO blended spinning and GO coating post-treatment. The mechanical performance of the demonstrated rod samples matches the properties of the human rib. A self-designed cubic matrix was used to conduct in situ cell culture. In vitro evaluation not only confirms the cell viability and migration on the fibers' surface, but also investigated the degradation and fission performance of fibrous rods. With a simple, minimally invasive implantation and controlled swelling, Alg/GO fibrous rods are able to tightly fix the rib fracture wound while maintaining sufficient flexibility.

New Hope for Treating Intervertebral Disc Degeneration: Microsphere-Based Delivery System

Intervertebral disc (IVD) degeneration (IVDD) has been considered the dominant factor in low back pain (LBP), and its etiological mechanisms are complex and not yet fully elucidated. To date, the treatment of IVDD has mainly focused on relieving clinical symptoms and cannot fundamentally solve the problem. Recently, a novel microsphere-based therapeutic strategy has held promise for IVD regeneration and has yielded encouraging results with in vitro experiments and animal models. With excellent injectability, biocompatibility, and biodegradability, this microsphere carrier allows for targeted delivery and controlled release of drugs, gene regulatory sequences, and other bioactive substances and supports cell implantation and directed differentiation, aiming to improve the disease state of IVD at the source. This review discusses the possible mechanisms of IVDD and the limitations of current therapies, focusing on the application of microsphere delivery systems in IVDD, including targeted delivery of active substances and drugs, cellular therapy, and gene therapy, and attempts to provide a new understanding for the treatment of IVDD.

Effectiveness of exosome mediated miR-126 and miR-146a delivery on cardiac tissue regeneration

Despite advances in the treatment of acute myocardial infarction, due to the non-proliferative nature of adult cardiomyocytes, the injured myocardium is mainly replaced by fibrotic tissue, which ultimately causes heart failure. To prevent heart failure, particularly after myocardial infarction, exosome-based therapy has emerged as one of the most promising strategies to regenerate cardiac function. Exosomes can carry microRNAs in support of neovascularization, anti-inflammatory, and endogenous cardiac regeneration. This study demonstrated that animal rat models' combination treatment with microRNA-126 and microRNA-146a mimics in exosomes is desirable for cardiac regeneration after myocardial infarction. The exosomes isolated from stem cells and loaded with microRNAs were characterized their impacts in cell migration, tube formation, and vascular endothelial growth factor degree. In the following, the usefulness of loaded microRNAs in exosomes and their encapsulation within alginate derivative hydrogel was analyzed in myocardial infarction for an animal model. Exosomes isolated and loaded with microRNAs showed the synergetic impact on cell migration, tube formation, and promoted vascular endothelial growth factor folding. Moreover, microRNAs loaded exosomes and encapsulated them in alginate hydrogel could help in reducing infarct size and improving angiogenesis in myocardial infarction. The angiogenesis markers including CD31 and connexion 43 upregulated for myocardial infarction models treated with alginate-based hydrogels loaded with exosomes and microRNAs-exosomes. Histological analysis indicated that myocardial infarction model rats treated with alginate hydrogel loaded with microRNAs-exosomes possessed lower and higher degrees of fibrosis and collagen fiber, respectively. These findings have important therapeutic implications for a myocardial infarction model through angiogenesis and vascular integrity regulation.

Interaction of alginate with nano-hydroxyapatite-collagen using strontium provides suitable osteogenic platform

Background

Hydrogels based on organic/inorganic composites have been at the center of attention for the fabrication of engineered bone constructs. The establishment of a straightforward 3D microenvironment is critical to maintaining cell-to-cell interaction and cellular function, leading to appropriate regeneration. Ionic cross-linkers, Ca²⁺, Ba²⁺, and Sr²⁺, were used for the fabrication of Alginate-Nanohydroxyapatite-Collagen (Alg-nHA-Col) microspheres, and osteogenic properties of human osteoblasts were examined in in vitro and in vivo conditions after 21 days.

Results

Physicochemical properties of hydrogels illustrated that microspheres cross-linked with Sr²⁺ had reduced swelling, enhanced stability, and mechanical strength, as compared to the other groups. Human MG-63 osteoblasts inside Sr²⁺ cross-linked microspheres exhibited enhanced viability and osteogenic capacity indicated by mineralization and the increase of relevant proteins related to bone formation. PCR (Polymerase Chain Reaction) array analysis of the Wnt (Wingless-related integration site) signaling pathway revealed that Sr²⁺ cross-linked microspheres appropriately induced various signaling transduction pathways in human osteoblasts leading to osteogenic activity and dynamic growth. Transplantation of Sr²⁺ cross-linked microspheres with rat osteoblasts into cranium with critical size defect in the rat model accelerated bone formation analyzed with micro-CT and histological examination.

Conclusion

Sr²⁺ cross-linked Alg-nHA-Col hydrogel can promote functionality and dynamic growth of osteoblasts.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01511-9.

Polymer-Based Nanofiber-Nanoparticle Hybrids and Their Medical Applications

The search for higher-quality nanomaterials for medicinal applications continues. There are similarities between electrospun fibers and natural tissues. This property has enabled electrospun fibers to make significant progress in medical applications. However, electrospun fibers are limited to tissue scaffolding applications. When nanoparticles and nanofibers are combined, the composite material can perform more functions, such as photothermal, magnetic response, biosensing, antibacterial, drug delivery and biosensing. To prepare nanofiber and nanoparticle hybrids (NNHs), there are two primary ways. The electrospinning technology was used to produce NNHs in a single step. An alternate way is to use a self-assembly technique to create nanoparticles in fibers. This paper describes the creation of NNHs from routinely used biocompatible polymer composites. Single-step procedures and self-assembly methodologies are used to discuss the preparation of NNHs. It combines recent research discoveries to focus on the application of NNHs in drug release, antibacterial, and tissue engineering in the last two years.