Biomaterials for tissue repair

Simulation of the bone remodelling microenvironment by calcium compound-loaded hydrogel fibrous membranes for in situ bone regeneration

The endowment of guided bone regeneration (GBR) membranes with the ability to activate the endogenous regenerative capability of bone to regenerate bone defects is of clinical significance. Herein we explored the preparation of the calcium compound (CC) (calcium sulfate (CaSL), calcium hydrophosphate (CaHP), or tricalcium phosphate (TCaP)) loaded ultrathin silk fibroin (SF)/gelatin (G) fibre membranes via electrospinning as the GBR membranes to regenerate the calvarial bone defects. The in vitro experiments demonstrated that the CaSL-loaded ultrathin fibrous membranes could simulate optimally the bone remodelling microenvironment in comparison with the CaHP- and TCaP-loaded fibrous membranes, displaying the highest activity to regulate the migration, proliferation, and differentiation of mesenchymal stem cells (MSCs). Also, the in vivo experiments demonstrated that the CaSL-loaded fibrous membranes presented the highest intrinsic osteoinduction to guide in situ regeneration of bone. Furthermore, the in vivo experiments demonstrated that the as-prepared composite fibrous membranes possessed good degradability. In summary, our results suggested that the CaSL-loaded fibrous membranes with high intrinsic osteoinduction and good degradability have potential to translate into clinical practice.

Functionalized hydrogels as smart gene delivery systems to treat musculoskeletal disorders

Despite critical advances in regenerative medicine, the generation of definitive, reliable treatments for musculoskeletal diseases remains challenging. Gene therapy based on the delivery of therapeutic genetic sequences has strong value to offer effective, durable options to decisively manage such disorders. Furthermore, scaffold-mediated gene therapy provides powerful alternatives to overcome hurdles associated with classical gene therapy, allowing for the spatiotemporal delivery of candidate genes to sites of injury. Among the many scaffolds for musculoskeletal research, hydrogels raised increasing attention in addition to other potent systems (solid, hybrid scaffolds) due to their versatility and competence as drug and cell carriers in tissue engineering and wound dressing. Attractive functionalities of hydrogels for musculoskeletal therapy include their injectability, stimuli-responsiveness, self-healing, and nanocomposition that may further allow to upgrade of them as "intelligently" efficient and mechanically strong platforms, rather than as just inert vehicles. Such functionalized hydrogels may also be tuned to successfully transfer therapeutic genes in a minimally invasive manner in order to protect their cargos and allow for their long-term effects. In light of such features, this review focuses on functionalized hydrogels and demonstrates their competence for the treatment of musculoskeletal disorders using gene therapy procedures, from gene therapy principles to hydrogel functionalization methods and applications of hydrogel-mediated gene therapy for musculoskeletal disorders, while remaining challenges are being discussed in the perspective of translation in patients. STATEMENT OF SIGNIFICANCE: Despite advances in regenerative medicine, the generation of definitive, reliable treatments for musculoskeletal diseases remains challenging. Gene therapy has strong value in offering effective, durable options to decisively manage such disorders. Scaffold-mediated gene therapy provides powerful alternatives to overcome hurdles associated with classical gene therapy. Among many scaffolds for musculoskeletal research, hydrogels raised increasing attention. Functionalities including injectability, stimuli-responsiveness, and self-healing, tune them as "intelligently" efficient and mechanically strong platforms, rather than as just inert vehicles. This review introduces functionalized hydrogels for musculoskeletal disorder treatment using gene therapy procedures, from gene therapy principles to functionalized hydrogels and applications of hydrogel-mediated gene therapy for musculoskeletal disorders, while remaining challenges are discussed from the perspective of translation in patients.

Glucosamine sulfate-loaded nanofiber reinforced carboxymethyl chitosan sponge for articular cartilage restoration

Cartilage is severely limited in self-repair after damage, and tissue engineering scaffold transplantation is considered the most promising strategy for cartilage regeneration. However, scaffolds without cells and growth factors, which can effectively avoid long cell culture times, high risk of infection, and susceptibility to contamination, remain scarce. Hence, we developed a cell- and growth factor-dual free hierarchically structured nanofibrous sponge to mimic the extracellular matrix, in which the encapsulated core-shell nanofibers served both as mechanical supports and as long-lasting carriers for bioactive biomass molecules (glucosamine sulfate). Under the protection of the nanofibers in this designed sponge, glucosamine sulfate could be released continuously for at least 30 days, which significantly accelerated the repair of cartilage tissue in a rat cartilage defect model. Moreover, the nanofibrous sponge based on carboxymethyl chitosan as the framework could effectively fill irregular cartilage defects, adapt to the dynamic changes during cartilage movement, and maintain almost 100 % elasticity even after multiple compression cycles. This strategy, which combines fiber freeze-shaping technology with a controlled-release method for encapsulating bioactivity, allows for the assembly of porous bionic scaffolds with hierarchical nanofiber structure, providing a novel and safe approach to tissue repair.

A Spin-Charge-Regulated Self-Powered Nanogenerator for Simultaneous Pyro-Magneto-Electric Energy Harvesting

In view of the depletion of natural energy resources, harvesting energy from waste is a revolution to simultaneously capture, unite, and recycle various types of waste energies in flexible devices. Thus, in this work, a spin-charge-regulated pyro-magneto-electric nanogenerator is devised at a well-known ferroelectric P(VDF-TrFE) copolymer. It promptly stores thermal-magnetic energies in a "capacitor" that generates electricity at room temperature. The ferroelectric domains are regulated to slip at the interfaces (also twins) of duly promoting polarization and other properties. An excellent pyroelectric coefficient p ∼ 615 nC·m-2·K-1 is obtained, with duly enhanced stimuli of a thermal sensitivity ∼1.05 V·K-1, a magnetoelectric coefficient αme ∼8.8 mV·cm-1·Oe-1 at 180 Hz (resonance frequency), and a magnetosensitivity ∼473 V/T. It is noteworthy that a strategy of further improving p (up to 41.2 μC·m-2·K-1) and αme (up to 23.6 mV·cm-1·Oe-1) is realized in the electrically poled dipoles. In a model hybrid structure, the spins lead to switch up the electric dipoles parallel at the polymer chains in a cohesive charged layer. It is an innovative approach for efficiently scavenging waste energies from electric vehicles, homes, and industries, where abundant thermal and magnetic energies are accessible. This sustainable strategy could be useful in next-generation self-powered electronics.

Regenerative Medicine in Urogynecology: Where We Are and Where We Want to Be

ABSTRACT

Pelvic floor disorders (PFDs) constitute a major public health issue given their negative effect on quality of life for millions of women worldwide and the associated economic burden. As the prevalence of PFDs continues to increase, novel therapeutic approaches for the effective treatment of these disorders are urgently needed. Regenerative medicine techniques, including cellular therapies, extracellular vesicles, secretomes, platelet-rich plasma, laser therapy, and bioinductive acellular biomaterial scaffolds, are emerging as viable clinical options to counteract urinary and fecal incontinence, as well as pelvic organ prolapse. This brief expert review explores the current state-of-science regarding application of these therapies for the treatment of PFDs. Although regenerative approaches have not been widely deployed in clinical care to date, these innovative techniques show a promising safety profile and potential to positively affect the quality of life of patients with PFDs. Furthermore, investigations focused on regeneration of the main constituents of the pelvic floor and lower urinary tract improve our understanding of the underlying pathophysiology of PFDs. Regenerative medicine techniques have a high potential not only to revolutionize treatment of PFDs but also to prevent these complex conditions.

Improving the mechanical and biological functions of cell sheet constructs: The interplay of human-derived periodontal ligament stem cells, endothelial cells and plasma rich in growth factors

OBJECTIVE

The aim of this study was to produce and characterize triple-layered cell sheet constructs with varying cell compositions combined or not with the fibrin membrane scaffold obtained by the technology of Plasma Rich in Growth Factors (mPRGF).

MATERIALS AND METHODS

Human primary cultures of periodontal ligament stem cells (hPDLSCs) were isolated, and their stemness nature was evaluated. Three types of triple-layered composite constructs were generated, composed solely of hPDLSCs or combined with human umbilical vein endothelial cells (HUVECs), either as a sandwiched endothelial layer or as coculture sheets of both cell phenotypes. These three triple-layered constructs were also manufactured using mPRGF as cell sheets' support. Necrosis, glucose consumption, secretion of extracellular matrix proteins and synthesis of proangiogenic factors were determined. Histological evaluations and proteomic analyses were also performed.

RESULTS

The inclusion of HUVECs did not clearly improve the properties of the multilayered constructs and yet hindered their optimal conformation. The presence of mPRGF prevented the shrinkage of cell sheets, stimulated the metabolic activity and increased the matrix synthesis. At the proteome level, mPRGF conferred a dramatic advantage to the hPDLSC constructs in their ability to provide a suitable environment for tissue regeneration by inducing the expression of proteins necessary for bone morphogenesis and cellular proliferation.

CONCLUSIONS

hPDLSCs' triple-layer construct onto mPRGF emerges as the optimal structure for its use in regenerative therapeutics.

CLINICAL RELEVANCE

These results suggest the suitability of mPRGF as a promising tool to support cell sheet formation by improving their handling and biological functions.

Zeolitic imidazolate framework-8: a versatile nanoplatform for tissue regeneration

Extensive research on zeolitic imidazolate framework (ZIF-8) and its derivatives has highlighted their unique properties in nanomedicine. ZIF-8 exhibits advantages such as pH-responsive dissolution, easy surface functionalization, and efficient drug loading, making it an ideal nanosystem for intelligent drug delivery and phototherapy. These characteristics have sparked significant interest in its potential applications in tissue regeneration, particularly in bone, skin, and nerve regeneration. This review provides a comprehensive assessment of ZIF-8's feasibility in tissue engineering, encompassing material synthesis, performance testing, and the development of multifunctional nanosystems. Furthermore, the latest advancements in the field, as well as potential limitations and future prospects, are discussed. Overall, this review emphasizes the latest developments in ZIF-8 in tissue engineering and highlights the potential of its multifunctional nanoplatforms for effective complex tissue repair.

Bioinspired polysaccharide-based nanocomposite membranes with robust wet mechanical properties for guided bone regeneration

Polysaccharide-based membranes with excellent mechanical properties are highly desired. However, severe mechanical deterioration under wet conditions limits their biomedical applications. Here, inspired by the structural heterogeneity of strong yet hydrated biological materials, we propose a strategy based on heterogeneous crosslink-and-hydration (HCH) of a molecule/nano dual-scale network to fabricate polysaccharide-based nanocomposites with robust wet mechanical properties. The heterogeneity lies in that the crosslink-and-hydration occurs in the molecule-network while the stress-bearing nanofiber-network remains unaffected. As one demonstration, a membrane assembled by bacterial cellulose nanofiber-network and Ca2+-crosslinked and hydrated sodium alginate molecule-network is designed. Studies show that the crosslinked-and-hydrated molecule-network restricts water invasion and boosts stress transfer of the nanofiber-network by serving as interfibrous bridge. Overall, the molecule-network makes the membrane hydrated and flexible; the nanofiber-network as stress-bearing component provides strength and toughness. The HCH dual-scale network featuring a cooperative effect stimulates the design of advanced biomaterials applied under wet conditions such as guided bone regeneration membranes.

Granular Hydrogels Improve Myogenic Invasion and Repair after Volumetric Muscle Loss

Skeletal muscle injuries including volumetric muscle loss (VML) lead to excessive tissue scarring and permanent functional disability. Despite its high prevalence, there is currently no effective treatment for VML. Bioengineering interventions such as biomaterials that fill the VML defect to support cell and tissue growth are a promising therapeutic strategy. However, traditional biomaterials developed for this purpose lack the pore features needed to support cell infiltration. The present study investigates for the first time, the impact of granular hydrogels on muscle repair - hypothesizing that their flowability will permit conformable filling of the defect site and their inherent porosity will support the invasion of native myogenic cells, leading to effective muscle repair. Small and large microparticle fragments are prepared from photocurable hyaluronic acid polymer via extrusion fragmentation and facile size sorting. In assembled granular hydrogels, particle size and degree of packing significantly influence pore features, rheological behavior, and injectability. Using a mouse model of VML, it is demonstrated that, in contrast to bulk hydrogels, granular hydrogels support early-stage (satellite cell invasion) and late-stage (myofiber regeneration) muscle repair processes. Together, these results highlight the promising potential of injectable and porous granular hydrogels in supporting endogenous repair after severe muscle injury.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Hurdles in translating science from lab to market in delivery systems for Cosmetics: An industrial perspective

In recent decades, a sweeping technological wave has reshaped the global economic landscape. Fueled by the unceasing forces of digital innovation and venture capital investment, this transformative machine has left a significant mark across numerous economic sectors. More recently, the emergence of 'deep tech' start-ups, focusing on areas such as artificial intelligence, nanotechnology, and biotechnology, has infused a fresh wave of innovation into various sectors, including the pharmaceutical and cosmetic industry. This review explores the significance of innovation within the cosmetics sector, with a particular emphasis on delivery systems. It assesses the crucial process of bridging the gap between research and the market, particularly in the translation of nanotechnology into tangible real-world applications. With the rise of nanotechnology-based beauty ingredients, we can anticipate groundbreaking advancements that promise to surpass consumer expectations, ushering in a new era of unparalleled innovation in beauty products.

Panthenol Citrate Biomaterials Accelerate Wound Healing and Restore Tissue Integrity

Impaired wound healing is a common complication for diabetic patients and effective diabetic wound management remains a clinical challenge. Furthermore, a significant problem that contributes to patient morbidity is the suboptimal quality of healed skin, which often leads to reoccurring chronic skin wounds. Herein, a novel compound and biomaterial building block, panthenol citrate (PC), is developed. It has interesting fluorescence and absorbance properties, and it is shown that PC can be used in soluble form as a wash solution and as a hydrogel dressing to address impaired wound healing in diabetes. PC exhibits antioxidant, antibacterial, anti-inflammatory, and pro-angiogenic properties, and promotes keratinocyte and dermal fibroblast migration and proliferation. When applied in a splinted excisional wound diabetic rodent model, PC improves re-epithelialization, granulation tissue formation, and neovascularization. It also reduces inflammation and oxidative stress in the wound environment. Most importantly, it improves the regenerated tissue quality with enhanced mechanical strength and electrical properties. Therefore, PC could potentially improve wound care management for diabetic patients and play a beneficial role in other tissue regeneration applications.

A 3D-Printed Assemblable Bespoke Scaffold as a Versatile Microcryogel Carrier for Site-Specific Regenerative Medicine

Advances in additive manufacturing have led to diverse patient-specific implant designs utilizing computed tomography, but this requires intensive work and financial implications. Here, Digital Light Processing is used to fabricate a hive-structured assemblable bespoke scaffold (HIVE). HIVE can be manually assembled in any shape/size with ease, so a surgeon can create a scaffold that will best fit a defect before implantation. Simultaneously, it can have site-specific treatments by working as a carrier filled with microcryogels (MC) incorporating different biological factors in different pockets of HIVE. After characterization, possible site-specific applications are investigated by utilizing HIVE as a versatile carrier with incorporated treatments such as growth factors (GF), bioceramic, or cells. HIVE as a GF-carrier shows a controlled release of bone morphogenetic protein/vascular endothelial growth factor (BMP/VEGF) and induced osteogenesis/angiogenesis from human mesenchymal stem cells (hMSC)/human umbilical vein endothelial cells (HUVECs). Furthermore, as a bioceramic-carrier, HIVE demonstrates enhanced mineralization and osteogenesis, and as a HUVEC carrier, it upregulates both osteogenic and angiogenic gene expression of hMSCs. HIVE with different combinations of MCs yields a distinct local effect and successful cell migration is confirmed within assembled HIVEs. Finally, an in vivo rat subcutaneous implantation demonstrates site-specific osteogenesis and angiogenesis.

Effect of composite conjugated materials on tissue healing during exercise rehabilitation training

The application of traditional materials to tissue healing in sports rehabilitation training has problems such as poor effect, high rejection reaction, and slow healing speed. It also brings many challenges to the development of sports rehabilitation training. This article aims to explore the impact of composite conjugated materials on tissue healing to promote rapid and efficient tissue healing and improve the effect of sports rehabilitation training. Through research and analysis, this article found that composite conjugated materials have unique biocompatibility and can promote cell growth and differentiation. In skin tissue healing, composite conjugated materials can control the release rate and duration of drugs to promote skin healing. During the fracture healing process, conjugated materials can provide growth factors and extracellular matrix components, stimulate bone cell proliferation and differentiation, and promote fracture healing. In terms of soft tissue injuries, composite conjugated materials serve as supporting structures or matrices, providing a favorable environment for the regeneration of damaged tissue. In the regulation of inflammatory responses, composite conjugated materials reduce inflammatory responses and accelerate the healing process by modulating immune responses. The results of this study show that 1 week after the experiment, the skin healing rates of the control group and the experimental group were 42.55% and 58.17% respectively; 5 weeks after the experiment, the skin healing rates of the control group and the experimental group were 51.28% and 73.24% respectively. After 1, 2, 3, 4, and 5 weeks of experiment, it was found that the average tissue repair rates of the control group were 44.03%, 54.18%, 58.40%, 67.08%, and 72.09% respectively, and the average tissue repair rates of the experimental group were 52.18%, 61.91%, 63.40%, 74.61%, and 85.05% respectively. This study highlights the huge potential of composite conjugated materials in promoting tissue healing and tissue repair, and is of great significance for promoting technological progress in the field of sports rehabilitation and improving rehabilitation effects.

Immunomodulatory contribution of mast cells to the regenerative biomaterial microenvironment

Bioactive immunomodulatory biomaterials have shown promise for influencing the immune response to promote tissue repair and regeneration. Macrophages and T cells have been associated with this response; however, other immune cell types have been traditionally overlooked. In this study, we investigated the role of mast cells in the regulation of the immune response to decellularized biomaterial scaffolds using a subcutaneous implant model. In mast cell-deficient mice, there was dysregulation of the expected M1 to M2 macrophage transition typically induced by the biomaterial scaffold. Polarization progression deviated in a sex-specific manner with an early transition to an M2 profile in female mice, while the male response was unable to properly transition past a pro-inflammatory M1 state. Both were reversed with adoptive mast cell transfer. Further investigation of the later-stage immune response in male mice determined a greater sustained pro-inflammatory gene expression profile, including the IL-1 cytokine family, IL-6, alarmins, and chemokines. These results highlight mast cells as another important cell type that influences the immune response to pro-regenerative biomaterials.

The Effect of Leukocyte- and Platelet-Rich Fibrin on Central and Peripheral Nervous System Neurons-Implications for Biomaterial Applicability

Leukocyte- and Platelet-Rich Fibrin (L-PRF) is a second-generation platelet concentrate that is prepared directly from the patient's own blood. It is widely used in the field of regenerative medicine, and to better understand its clinical applicability we aimed to further explore the biological properties and effects of L-PRF on cells from the central and peripheral nervous system. To this end, L-PRF was prepared from healthy human donors, and confocal, transmission, and scanning electron microscopy as well as secretome analysis were performed on these clots. In addition, functional assays were completed to determine the effect of L-PRF on neural stem cells (NSCs), primary cortical neurons (pCNs), and peripheral dorsal root ganglion (DRG) neurons. We observed that L-PRF consists of a dense but porous fibrin network, containing leukocytes and aggregates of activated platelets that are distributed throughout the clot. Antibody array and ELISA confirmed that it is a reservoir for a plethora of growth factors. Key molecules that are known to have an effect on neuronal cell functions such as brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) were slowly released over time from the clots. Next, we found that the L-PRF secretome had no significant effect on the proliferative and metabolic activity of NSCs, but it did act as a chemoattractant and improved the migration of these CNS-derived stem cells. More importantly, L-PRF growth factors had a detrimental effect on the survival of pCNs, and consequently, also interfered with their neurite outgrowth. In contrast, we found a positive effect on peripheral DRG neurons, and L-PRF growth factors improved their survival and significantly stimulated the outgrowth and branching of their neurites. Taken together, our study demonstrates the positive effects of the L-PRF secretome on peripheral neurons and supports its use in regenerative medicine but care should be taken when using it for CNS applications.

Composite Hydrogels of Ultrasound-Assisted-Digested Formic Acid-Decellularized Extracellular Matrix and Sacchachitin Nanofibers Incorporated with Platelet-Rich Plasma for Diabetic Wound Treatment

In this study, an ultrasound-assisted digestion method of a formic acid-decellularized extracellular matrix (dECM) of porcine skin was developed and optimized to form UdECM hydrogels for diabetic wound healing. Results demonstrated that ultrasonication improved the extraction rate of collagen from dECM samples, preserved the collagen content of dECM, reduced residual cells, and extracted greater DNA contents. Scanning electron microscope (SEM) analyses were performed, which demonstrated the optimal porosity on the surface and density of the cross-section in the hydrogel structure, which could control the release of growth factors embedded in UdECM hydrogels at desirable rates to boost wound healing. A wound-healing study was conducted with six different composite hydrogels, both empty materials and materials enriched with rat platelet-rich plasma (R-PRP), sacchachitin nanofibers (SCNFs), and TEMPO-oxidized sacchachitin in diabetic rats. The assessment based on scars stained with hematoxylin and eosin (H&E), Masson's trichrome (MT), and a cluster of differentiation 31 (CD31) staining showed that the UdECM/SC/R-PRP treatment group had the most significant efficacy of promoting healing and even recovery of diabetic wounds to normal tissues. UdECM/R-PRP and UdECM/SCNFs demonstrated better healing rates than UdECM hydrogel scaffolds, which had only recovered 50% resemblance to normal skin. Treatment with both UdECM/TEMPO 050 and UdECM/TEMPO 050/R-PRP hydrogel scaffolds was ranked last, with even poorer efficacy than UdECM hydrogels. In summary, formulated UdECM and SCNF hydrogels loaded with PRP showed synergistic effects of accelerating wound healing and ultimately stimulating the wound to recover as functional tissues. This newly UdECM/SCNF composite hydrogel has promising potential for healing and regenerating diabetic wounds.

Proregenerative extracellular matrix hydrogel mitigates pathological alterations of pelvic skeletal muscles after birth injury

Pelvic floor disorders, including pelvic organ prolapse and urinary and fecal incontinence, affect millions of women globally and represent a major public health concern. Pelvic floor muscle (PFM) dysfunction has been identified as one of the leading risk factors for the development of these morbid conditions. Childbirth, specifically vaginal delivery, has been recognized as the most important potentially modifiable risk factor for PFM injury; however, the precise mechanisms of PFM dysfunction after parturition remain elusive. In this study, we demonstrated that PFMs exhibit atrophy and fibrosis in parous women with symptomatic pelvic organ prolapse. These pathological alterations were recapitulated in a preclinical rat model of simulated birth injury (SBI). The transcriptional signature of PFMs after injury demonstrated an impairment in muscle anabolism, persistent expression of genes that promote extracellular matrix (ECM) deposition, and a sustained inflammatory response. We also evaluated the administration of acellular injectable skeletal muscle ECM hydrogel for the prevention of these pathological alterations. Treatment of PFMs with the ECM hydrogel either at the time of birth injury or 4 weeks after injury mitigated PFM atrophy and fibrosis. By evaluating gene expression, we demonstrated that these changes are mainly driven by the hydrogel-induced enhancement of endogenous myogenesis, ECM remodeling, and modulation of the immune response. This work furthers our understanding of PFM birth injury and demonstrates proof of concept for future investigations of proregenerative biomaterial approaches for the treatment of injured pelvic soft tissues.

3D printed pore morphology mediates bone marrow stem cell behaviors via RhoA/ROCK2 signaling pathway for accelerating bone regeneration

Bone bionics and structural engineering have sparked a broad interest in optimizing artificial scaffolds for better bone regeneration. However, the mechanism behind scaffold pore morphology-regulated bone regeneration remains unclear, making the structure design of scaffolds for bone repair challenging. To address this issue, we have carefully assessed diverse cell behaviors of bone mesenchymal stem cells (BMSCs) on the β-tricalcium phosphate (β-TCP) scaffolds with three representative pore morphologies (i.e., cross column, diamond, and gyroid pore unit, respectively). Among the scaffolds, BMSCs on the β-TCP scaffold with diamond pore unit (designated as D-scaffold) demonstrated enhanced cytoskeletal forces, elongated nucleus, faster cell mobility, and better osteogenic differentiation potential (for example, the alkaline phosphatase expression level in D-scaffold were 1.5-2 times higher than other groups). RNA-sequencing analysis and signaling pathway intervention revealed that Ras homolog gene family A (RhoA)/Rho-associated kinase-2 (ROCK2) has in-depth participated in the pore morphology-mediated BMSCs behaviors, indicating an important role of mechanical signaling transduction in scaffold-cell interactions. Finally, femoral condyle defect repair results showed that D-scaffold could effectively promote endogenous bone regeneration, of which the osteogenesis rate was 1.2-1.8 times higher than the other groups. Overall, this work provides insights into pore morphology-mediated bone regeneration mechanisms for developing novel bioadaptive scaffold designs.

The marriage of immunomodulatory, angiogenic, and osteogenic capabilities in a piezoelectric hydrogel tissue engineering scaffold for military medicine

BACKGROUND

Most bone-related injuries to grassroots troops are caused by training or accidental injuries. To establish preventive measures to reduce all kinds of trauma and improve the combat effectiveness of grassroots troops, it is imperative to develop new strategies and scaffolds to promote bone regeneration.

METHODS

In this study, a porous piezoelectric hydrogel bone scaffold was fabricated by incorporating polydopamine (PDA)-modified ceramic hydroxyapatite (PDA-hydroxyapatite, PHA) and PDA-modified barium titanate (PDA-BaTiO₃, PBT) nanoparticles into a chitosan/gelatin (Cs/Gel) matrix. The physical and chemical properties of the Cs/Gel/PHA scaffold with 0-10 wt% PBT were analyzed. Cell and animal experiments were performed to characterize the immunomodulatory, angiogenic, and osteogenic capabilities of the piezoelectric hydrogel scaffold in vitro and in vivo.

RESULTS

The incorporation of BaTiO₃ into the scaffold improved its mechanical properties and increased self-generated electricity. Due to their endogenous piezoelectric stimulation and bioactive constituents, the as-prepared Cs/Gel/PHA/PBT hydrogels exhibited cytocompatibility as well as immunomodulatory, angiogenic, and osteogenic capabilities; they not only effectively induced macrophage polarization to M2 phenotype but also promoted the migration, tube formation, and angiogenic differentiation of human umbilical vein endothelial cells (HUVECs) and facilitated the migration, osteo-differentiation, and extracellular matrix (ECM) mineralization of MC3T3-E1 cells. The in vivo evaluations showed that these piezoelectric hydrogels with versatile capabilities significantly facilitated new bone formation in a rat large-sized cranial injury model. The underlying molecular mechanism can be partly attributed to the immunomodulation of the Cs/Gel/PHA/PBT hydrogels as shown via transcriptome sequencing analysis, and the PI3K/Akt signaling axis plays an important role in regulating macrophage M2 polarization.

CONCLUSION

The piezoelectric Cs/Gel/PHA/PBT hydrogels developed here with favorable immunomodulation, angiogenesis, and osteogenesis functions may be used as a substitute in periosteum injuries, thereby offering the novel strategy of applying piezoelectric stimulation in bone tissue engineering for the enhancement of combat effectiveness in grassroots troops.

In situ activation of flexible magnetoelectric membrane enhances bone defect repair

For bone defect repair under co-morbidity conditions, the use of biomaterials that can be non-invasively regulated is highly desirable to avoid further complications and to promote osteogenesis. However, it remains a formidable challenge in clinical applications to achieve efficient osteogenesis with stimuli-responsive materials. Here, we develop polarized CoFe₂O₄@BaTiO₃/poly(vinylidene fluoridetrifluoroethylene) [P(VDF-TrFE)] core-shell particle-incorporated composite membranes with high magnetoelectric conversion efficiency for activating bone regeneration. An external magnetic field force conduct on the CoFe₂O₄ core can increase charge density on the BaTiO₃ shell and strengthens the β-phase transition in the P(VDF-TrFE) matrix. This energy conversion increases the membrane surface potential, which hence activates osteogenesis. Skull defect experiments on male rats showed that repeated magnetic field applications on the membranes enhanced bone defect repair, even when osteogenesis repression is elicited by dexamethasone or lipopolysaccharide-induced inflammation. This study provides a strategy of utilizing stimuli-responsive magnetoelectric membranes to efficiently activate osteogenesis in situ.

Surface modifications of biomaterials in different applied fields

Biomaterial implantation into the human body plays a key role in the medical field and biological applications. Increasing the life expectancy of biomaterial implants, reducing the rejection reaction inside the human body and reducing the risk of infection are the problems in this field that need to be solved urgently. The surface modification of biomaterials can change the original physical, chemical and biological properties and improve the function of materials. This review focuses on the application of surface modification techniques in various fields of biomaterials reported in the past few years. The surface modification techniques include film and coating synthesis, covalent grafting, self-assembled monolayers (SAMs), plasma surface modification and other strategies. First, a brief introduction to these surface modification techniques for biomaterials is given. Subsequently, the review focuses on how these techniques change the properties of biomaterials, and evaluates the effects of modification on the cytocompatibility, antibacterial, antifouling and surface hydrophobic properties of biomaterials. In addition, the implications for the design of biomaterials with different functions are discussed. Finally, based on this review, it is expected that the biomaterials have development prospects in the medical field.

Repairing gastric ulcer with hyaluronic acid/extracellular matrix composite through promoting M2-type polarization of macrophages

The treatment of gastric ulcer and perforation using synthetic and biomaterials has been a clinical challenge. In this work, a drug-carrying layer of hyaluronic acid was combined with a gastric submucosal decellularized extracellular matrix called gHECM. The regulation of macrophage polarization by the extracellular matrix's components was then investigated. This work proclaims how gHECM responds to inflammation and aids in the regeneration of the gastric lining by altering the phenotype of surrounding macrophages and stimulating the body's whole immune response. In a nutshell, gHECM promotes tissue regeneration by changing the phenotype of macrophages around the site of injury. In particular, gHECM reduces the production of pro-inflammatory cytokines, decreases the percentage of M1 macrophages, and further encourages differentiation of macrophage subpopulation to the M2 phenotype and the release of anti-inflammatory cytokines, which could block the NF-κB pathway. Activated macrophages are capable of immediately delivering through spatial barriers, modulating the peripheral immune system, influencing the inflammatory microenvironment, and ultimately promoting the recovery of inflammation and healing of ulcers. They contribute to the secreted cytokines that act on local tissues or enhance the chemotactic ability of macrophages through paracrine secretion. In this study, we focused on the immunological regulatory network of macrophage polarization to further develop the mechanisms behind this process. Nevertheless, the signaling pathways involved in this process need to be further explored and identified. We think that our research will encourage more investigation into how the decellularized matrix affects immune modulation and will help the decellularized matrix perform better as a new class of natural biomaterials for tissue engineering.

Silk fibroin-based piezoelectric nanofibrous scaffolds for rapid wound healing

Piezoelectric polymer nanofibers are attracting increasing attention in the stimulation of cell growth and proliferation in tissue engineering and wound healing applications. However, their intrinsic non-biodegradability in vivo hinders widespread applications in the biological fields. Herein, we designed, synthesized and characterized composite materials of silk fibroin (SF)/LiNbO₃ (LN) nanoparticles/MWCNTs by electrospinning technology, which displayed good biocompatibility and comparable piezoelectric properties with an output current of up to 15 nA and output voltage of up to 0.6 V under pressure stimulation, remaining stable after 200 cycles of pressure release without significant decay. Meanwhile, the mechanical properties of the LN/CNTs/SF-nanofiber scaffolds (SF-NFSs) are also enhanced, with a tensile strength reaching 12.84 MPa and an elongation at break reaching 80.07%. Importantly, in vitro cell proliferation experiments showed that the LN/CNTs/SF-NFSs promoted cell proliferation at a rate of 43%. Accordingly, the mouse wound healing experiments further indicated that they could accelerate the healing of skin wounds in mice that were continuously moving. Therefore, SF-based piezoelectric nanofibrous scaffolds exhibit potential for use in rapid wound healing and this sheds light on smart treatment for tissue engineering in biomedicine.

Polymers and Bioactive Compounds with a Macrophage Modulation Effect for the Rational Design of Hydrogels for Skin Regeneration

The development of biomaterial platforms for dispensing reagents of interest such as antioxidants, growth factors or antibiotics based on functional hydrogels represents a biotechnological solution for many challenges that the biomedicine field is facing. In this context, in situ dosing of therapeutic components for dermatological injuries such as diabetic foot ulcers is a relatively novel strategy to improve the wound healing process. Hydrogels have shown more comfort for the treatment of wounds due to their smooth surface and moisture, as well as their structural affinity with tissues in comparison to hyperbaric oxygen therapy, ultrasound, and electromagnetic therapies, negative pressure wound therapy or skin grafts. Macrophages, one of the most important cells of the innate immune system, have been described as the key not only in relation to the host immune defense, but also in the progress of wound healing. Macrophage dysfunction in chronic wounds of diabetic patients leads to a perpetuating inflammatory environment and impairs tissue repair. Modulating the macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) could be a strategy for helping to improve chronic wound healing. In this regard, a new paradigm is found in the development of advanced biomaterials capable of inducing in situ macrophage polarization to offer an approach to wound care. Such an approach opens a new direction for the development of multifunctional materials in regenerative medicine. This paper surveys emerging hydrogel materials and bioactive compounds being investigated to induce the immunomodulation of macrophages. We propose four potential functional biomaterials for wound healing applications based on novel biomaterial/bioactive compound combination that are expected to show synergistic beneficial outcomes for the local differentiation of macrophages (M1-M2) as a therapeutic strategy for chronic wound healing improvement.

Microneedles for in situ tissue regeneration

Tissue injury is a common clinical problem, which may cause great burden on patients' life. It is important to develop functional scaffolds to promote tissue repair and regeneration. Due to their unique composition and structure, microneedles have attracted extensive attention in various tissues regeneration, including skin wound, corneal injury, myocardial infarction, endometrial injury, and spinal cord injury et al. Microneedles with micro-needle structure can effectively penetrate the barriers of necrotic tissue or biofilm, therefore improving the bioavailability of drugs. The use of microneedles to deliver bioactive molecules, mesenchymal stem cells, and growth factors in situ allows for targeted tissue and better spatial distribution. At the same time, microneedles can also provide mechanical support or directional traction for tissue, thus accelerating tissue repair. This review summarized the research progress of microneedles for in situ tissue regeneration over the past decade. At the same time, the shortcomings of existing researches, future research direction and clinical application prospect were also discussed.

Customizable Low-Friction Tough Hydrogels for Potential Cartilage Tissue Engineering by a Rapid Orthogonal Photoreactive 3D-Printing Design

Hydrogels have demonstrated wide applications in tissue engineering, but it is still challenging to develop strong, customizable, low-friction artificial scaffolds. Here, we report a rapid orthogonal photoreactive 3D-printing (ROP3P) strategy to achieve the design of high-performance hydrogels in tens of minutes. The orthogonal ruthenium chemistry enables the formation of multinetworks in hydrogels via phenol-coupling reaction and traditional radical polymerization. Further Ca²⁺-cross-linking treatment greatly improves their mechanical properties (6.4 MPa at a critical strain of 300%) and toughness (10.85 MJ m^-3). The tribological investigation reveals that the high elastic moduli of the as-prepared hydrogels improve their lubrication (∼0.02) and wear-resistance performances. These hydrogels are biocompatible and nontoxic and promote bone marrow mesenchymal stem cell adhesion and propagation. The introduction of 1-hydroxy-3-(acryloylamino)-1,1-propanediylbisphosphonic acid units can greatly enhance their antibacterial property to kill typical Escherichia coli and Staphylococcus aureus. Moreover, the rapid ROP3P can achieve hydrogel preparation in several seconds and is readily compatible with making artificial meniscus scaffolds. The printed meniscus-like materials are mechanically stable and can maintain their shape under long-term gliding tests. It is anticipated that these high-performance customizable low-friction tough hydrogels and the highly efficient ROP3P strategy could promote further development and practical applications of hydrogels in biomimetic tissue engineering, materials chemistry, bioelectronics, and so on.

L-cysteine aided polyaniline capped SrO2 nanoceramics: Assessment of MC3T3-E1-arbitrated osteogenesis and anti-bactericidal efficacy on the polyurethane 2D nanofibrous substrate

Fabricating bioartificial bone graft ceramics retaining structural, mechanical, and bone induction properties akin to those of native stem-cell niches is a major challenge in the field of bone tissue engineering and regenerative medicine. Moreover, the developed materials are susceptible to microbial invasion leading to biomaterial-centered infections which might limit their clinical translation. Here, we successfully developed biomimetic porous scaffolds of polyurethane-reinforcedL-cysteine-anchored polyaniline capped strontium oxide nanoparticles to improve the scaffold's biocompatibility, osteo-regeneration, mechanical, and antibacterial properties. The engineered nanocomposite substrate PU/L-Cyst-SrO₂ @PANI (0.4 wt%) significantly promotes bone repair and regeneration by modulating osteolysis and osteogenesis. ALP activity, collagen-I, ARS staining, as well as biomineralization of MC3T3-E1 cells, were used to assess the biocompatibility and cytocompatibility of the developed scaffolds in vitro, confirming that the scaffold provided a favorable microenvironment with a prominent effect on cell growth, proliferation, and differentiation. Furthermore, osteogenic protein markers were studied using qRT-PCR with expression levels of runt-related transcription factor 2 (RUNX2), secreted phosphoprotein 1 (Spp-I), and collagen type I (Col-I). The overall results suggest that PU/L-Cyst-SrO₂ @PANI (0.4 wt%) scaffolds showed superior interfacial biocompatibility, antibacterial properties, load-bearing ability, and osteoinductivity as compared to pristine PU. Thus, prepared bioactive nanocomposite scaffolds perform as a promising biomaterial substrate for bone tissue regeneration.

Syndecan-4 and stromal cell-derived factor-1 alpha functionalized endovascular scaffold facilitates adhesion, spreading and differentiation of endothelial colony forming cells and functions under flow and shear stress conditions

Acellular vascular scaffolds with capture molecules have shown great promise in recruiting circulating endothelial colony forming cells (ECFCs) to promote in vivo endothelialization. A microenvironment conducive to cell spreading and differentiation following initial cell capture are key to the eventual formation of a functional endothelium. In this study, syndecan-4 and stromal cell-derived factor-1 alpha were used to functionalize an elastomeric biomaterial composed of poly(glycerol sebacate), Silk Fibroin and Type I Collagen, termed PFC, to enhance ECFC-material interaction. Functionalized PFC (fPFC) showed significantly greater ECFCs capture capability under physiological flow. Individual cell spreading area on fPFC (1474 ± 63 μm² ) was significantly greater than on PFC (1187 ± 54 μm² ) as early as 2 h, indicating enhanced cell-material interaction. Moreover, fPFC significantly upregulated the expression of endothelial cell specific markers such as platelet endothelial cell adhesion molecule (24-fold) and Von Willebrand Factor (11-fold) compared with tissue culture plastic after 7 days, demonstrating differentiation of ECFCs into endothelial cells. fPFC fabricated as small diameter conduits and tested using a pulsatile blood flow bioreactor were stable and maintained function. The findings suggest that the new surface functionalization strategy proposed here results in an endovascular material with enhanced endothelialization.

Application of Nanomaterials in Stem Cell-Based Therapeutics for Cardiac Repair and Regeneration

Cardiovascular disease is a leading cause of disability and death worldwide. Although the survival rate of patients with heart diseases can be improved with contemporary pharmacological treatments and surgical procedures, none of these therapies provide a significant improvement in cardiac repair and regeneration. Stem cell-based therapies are a promising approach for functional recovery of damaged myocardium. However, the available stem cells are difficult to differentiate into cardiomyocytes, which result in the extremely low transplantation efficiency. Nanomaterials are widely used to regulate the myocardial differentiation of stem cells, and play a very important role in cardiac tissue engineering. This study discusses the current status and limitations of stem cells and cell-derived exosomes/micro RNAs based cardiac therapy, describes the cardiac repair mechanism of nanomaterials, summarizes the recent advances in nanomaterials used in cardiac repair and regeneration, and evaluates the advantages and disadvantages of the relevant nanomaterials. Besides discussing the potential clinical applications of nanomaterials in cardiac therapy, the perspectives and challenges of nanomaterials used in stem cell-based cardiac repair and regeneration are also considered. Finally, new research directions in this field are proposed, and future research trends are highlighted.

Stereochemistry Determines Immune Cellular Responses to Polylactide Implants

Repeating l- and d-chiral configurations determine polylactide (PLA) stereochemistry, which affects its thermal and physicochemical properties, including degradation profiles. Clinically, degradation of implanted PLA biomaterials promotes prolonged inflammation and excessive fibrosis, but the role of PLA stereochemistry is unclear. Additionally, although PLA of varied stereochemistries causes differential immune responses in vivo, this observation has yet to be effectively modeled in vitro. A bioenergetic model was applied to study immune cellular responses to PLA containing >99% l-lactide (PLLA), >99% d-lactide (PDLA), and a 50/50 melt-blend of PLLA and PDLA (stereocomplex PLA). Stereocomplex PLA breakdown products increased IL-1β, TNF-α, and IL-6 protein levels but not MCP-1. Expression of these proinflammatory cytokines is mechanistically driven by increases in glycolysis in primary macrophages. In contrast, PLLA and PDLA degradation products selectively increase MCP-1 protein expression. Although both oxidative phosphorylation and glycolysis are increased with PDLA, only oxidative phosphorylation is increased with PLLA. For each biomaterial, glycolytic inhibition reduces proinflammatory cytokines and markedly increases anti-inflammatory (IL-10) protein levels; differential metabolic changes in fibroblasts were observed. These findings provide mechanistic explanations for the diverse immune responses to PLA of different stereochemistries and underscore the pivotal role of immunometabolism in the biocompatibility of biomaterials applied in medicine.

Effect of Alleviating Fibrosis with EGCG-Modified Bone Graft in Murine Model Depended on Less Accumulation of Inflammatory Macrophage

In response to current trends in the modification of guided bone regeneration (GBR) materials, we aimed to build upon our previous studies on epigallocatechin-3-gallate (EGCG) by immersing a commonly used bone graft primarily composed of hydroxyapatite (HA) in EGCG solution, expecting to obtain superior bone material integration after implantation. Bone grafts are commonly used for bone repair, in which the bone extracellular matrix is stimulated to promote osteogenesis. However, due to its profibrosis effect, this osteoconductive material commonly exhibits implant failure. In addition to providing a basic release profile of EGCG-modified bone graft (E-HA) to clarify the relationship between this material and the environment, we have examined the integration effect via subcutaneous implantation experiments. In this manner, we have assessed the aggregation of proinflammatory macrophages, the formation of fibrous capsules, and an enhanced cell viability observed in cultured RAW 264.7 cells. Among these results, we focus on proinflammatory macrophages due to their close relationship with fibrosis, which is the most important process in the immune response. Immunofluorescent staining results showed that E-HA substantially compromised the formation of fibrous capsules in hematoxylin-eosin-stained sections, which exhibited less proinflammatory macrophage recruitment; meanwhile, the cell viability was improved. This work lays the foundation for future studies on GBR.

Intravascularly infused extracellular matrix as a biomaterial for targeting and treating inflamed tissues

Decellularized extracellular matrix in the form of patches and locally injected hydrogels has long been used as therapies in animal models of disease. Here we report the safety and feasibility of an intravascularly infused extracellular matrix as a biomaterial for the repair of tissue in animal models of acute myocardial infarction, traumatic brain injury and pulmonary arterial hypertension. The biomaterial consists of decellularized, enzymatically digested and fractionated ventricular myocardium, localizes to injured tissues by binding to leaky microvasculature, and is largely degraded in about 3 d. In rats and pigs with induced acute myocardial infarction followed by intracoronary infusion of the biomaterial, we observed substantially reduced left ventricular volumes and improved wall-motion scores, as well as differential expression of genes associated with tissue repair and inflammation. Delivering pro-healing extracellular matrix by intravascular infusion post injury may provide translational advantages for the healing of inflamed tissues 'from the inside out'.

Bioresponsive Immunotherapeutic Materials

The human immune system is an interaction network of biological processes, and its dysfunction is closely associated with a wide array of diseases, such as cancer, infectious diseases, tissue damage, and autoimmune diseases. Manipulation of the immune response network in a desired and controlled fashion has been regarded as a promising strategy for maximizing immunotherapeutic efficacy and minimizing side effects. Integration of "smart" bioresponsive materials with immunoactive agents including small molecules, biomacromolecules, and cells can achieve on-demand release of agents at targeted sites to reduce overdose-related toxicity and alleviate off-target effects. This review highlights the design principles of bioresponsive immunotherapeutic materials and discusses the critical roles of controlled release of immunoactive agents from bioresponsive materials in recruiting, housing, and manipulating immune cells for evoking desired immune responses. Challenges and future directions from the perspective of clinical translation are also discussed.

Degradable Biocompatible Porous Microtube Scaffold for Extended Donor Cell Survival and Activity

Cell therapy has significant therapeutic potential but is often limited by poor donor cell retention and viability at the host implantation site. Biomaterials can improve cell retention by providing cells with increased cell-cell and cell-matrix contacts and materials that allow three-dimensional cell culture to better recapitulate native cell morphology and function. In this study, we engineered a scaffold that allows for cell encapsulation and sustained three-dimensional cell culture. Since cell therapy is largely driven by paracrine secretions, the material was fabricated by electrospinning to have a large internal surface area, micrometer-thin walls, and nanoscale surface pores to allow for nutrient exchange without early cell permeation. The material is degradable, which allows for less invasive removal of the implant. Here, a biodegradable poly(lactic-co-glycolic acid) (PLGA) microtube array membrane was fabricated. In vitro testing showed that the material supported the culture of human dermal fibroblasts for at least 21 days, with paracrine secretion of pro-angiogenic FGF2. In vivo xenotransplantation of human cells in an immunocompetent mouse showed that donor cells could be maintained for more than one month and the material showed no obvious toxicity. Analysis of gene expression and tissue histology surrounding the implant showed that the material produced muted inflammatory and immune responses compared to a permanent implant and increased markers of angiogenesis.

Cardiac Mesenchymal Stem Cell-like Cells Derived from a Young Patient with Bicuspid Aortic Valve Disease Have a Prematurely Aged Phenotype

There is significant interest in the role of stem cells in cardiac regeneration, and yet little is known about how cardiac disease progression affects native cardiac stem cells in the human heart. In this brief report, cardiac mesenchymal stem cell-like cells (CMSCLC) from the right atria of a 21-year-old female patient with a bicuspid aortic valve and aortic stenosis (referred to as biscuspid aortic valve disease BAVD-CMSCLC), were compared with those of a 78-year-old female patient undergoing coronary artery bypass surgery (referred to as coronary artery disease CAD-CMSCLC). Cells were analyzed for expression of MSC markers, ability to form CFU-Fs, metabolic activity, cell cycle kinetics, expression of NANOG and p16, and telomere length. The cardiac-derived cells expressed MSC markers and were able to form CFU-Fs, with higher rate of formation in CAD-CMSCLCs. BAVD-CMSCLCs did not display normal MSC morphology, had a much lower cell doubling rate, and were less metabolically active than CAD-CMSCLCs. Cell cycle analysis revealed a population of BAVD-CMSCLC in G2/M phase, whereas the bulk of CAD-CMSCLC were in the G0/G1 phase. BAVD-CMSCLC had lower expression of NANOG and shorter telomere lengths, but higher expression of p16 compared with the CAD-CMSCLC. In conclusion, BAVD-CMSCLC have a prematurely aged phenotype compared with CAD-CMSCLC, despite originating from a younger patient.

Porous scaffold for mesenchymal cell encapsulation and exosome-based therapy of ischemic diseases

Ischemic diseases including myocardial infarction (MI) and limb ischemia are some of the greatest causes of morbidity and mortality worldwide. Cell therapy is a potential treatment but is usually limited by poor survival and retention of donor cells injected at the target site. Since much of the therapeutic effects occur via cell-secreted paracrine factors, including extracellular vesicles (EVs), we developed a porous material for cell encapsulation which would improve donor cell retention and survival, while allowing EV secretion. Human donor cardiac mesenchymal cells were used as a model therapeutic cell and the encapsulation system could sustain three-dimensional cell growth and secretion of therapeutic factors. Secretion of EVs and protective growth factors were increased by encapsulation, and secreted EVs had hypoxia-protective, pro-angiogenic activities in in vitro assays. In a mouse model of limb ischemia the implant improved angiogenesis and blood flow, and in an MI model the system preserved ejection fraction %. In both instances, the encapsulation system greatly extended donor cell retention and survival compared to directly injected cells. This system represents a promising therapy for ischemic diseases and could be adapted for treatment of other diseases in the future.

The role of the immune microenvironment in bone, cartilage, and soft tissue regeneration: from mechanism to therapeutic opportunity

Bone, cartilage, and soft tissue regeneration is a complex spatiotemporal process recruiting a variety of cell types, whose activity and interplay must be precisely mediated for effective healing post-injury. Although extensive strides have been made in the understanding of the immune microenvironment processes governing bone, cartilage, and soft tissue regeneration, effective clinical translation of these mechanisms remains a challenge. Regulation of the immune microenvironment is increasingly becoming a favorable target for bone, cartilage, and soft tissue regeneration; therefore, an in-depth understanding of the communication between immune cells and functional tissue cells would be valuable. Herein, we review the regulatory role of the immune microenvironment in the promotion and maintenance of stem cell states in the context of bone, cartilage, and soft tissue repair and regeneration. We discuss the roles of various immune cell subsets in bone, cartilage, and soft tissue repair and regeneration processes and introduce novel strategies, for example, biomaterial-targeting of immune cell activity, aimed at regulating healing. Understanding the mechanisms of the crosstalk between the immune microenvironment and regeneration pathways may shed light on new therapeutic opportunities for enhancing bone, cartilage, and soft tissue regeneration through regulation of the immune microenvironment.

Harnessing Biomaterials for Immunomodulatory-Driven Tissue Engineering

Abstract

The immune system plays a crucial role during tissue repair and wound healing processes. Biomaterials have been leveraged to assist in this in situ tissue regeneration process to dampen the foreign body response by evading or suppressing the immune system. An emerging paradigm within regenerative medicine is to use biomaterials to influence the immune system and create a pro-reparative microenvironment to instigate endogenously driven tissue repair. In this review, we discuss recent studies that focus on immunomodulation of innate and adaptive immune cells for tissue engineering applications through four biomaterial-based mechanisms of action: biophysical cues, chemical modifications, drug delivery, and sequestration. These materials enable augmented regeneration in various contexts, including vascularization, bone repair, wound healing, and autoimmune regulation. While further understanding of immune-material interactions is needed to design the next generation of immunomodulatory biomaterials, these materials have already demonstrated great promise for regenerative medicine.

Lay Summary

The immune system plays an important role in tissue repair. Many biomaterial strategies have been used to promote tissue repair, and recent work in this area has looked into the possibility of doing repair by tuning. Thus, we examined the literature for recent works showcasing the efficacy of these approaches in animal models of injuries. In these studies, we found that biomaterials successfully tuned the immune response and improved the repair of various tissues. This highlights the promise of immune-modulating material strategies to improve tissue repair.

Navigating ethical challenges in the development and translation of biomaterials research

Biomaterials--from implanted iron teeth in the second century to intraocular lenses, artificial joints, and stents today--have long been used clinically. Today, biomaterials researchers and biomedical engineers are pushing beyond these inert synthetic alternatives and incorporating complex multifunctional materials to control biological interactions and direct physiological processes. These advances are leading to novel strategies for targeted drug delivery, drug screening, diagnostics and imaging, gene therapy, tissue regeneration, and cell transplantation. While the field has survived ethical transgressions in the past, the rapidly expanding scope of biomaterials science, combined with the accelerating clinical translation of this diverse field calls for urgent attention to the complex and challenging ethical dilemmas these advances pose. This perspective responds to this call, examining the intersection of research ethics -- the sets of rules, principles and norms guiding responsible scientific inquiry -- and ongoing advances in biomaterials. While acknowledging the inherent tensions between certain ethical norms and the pressures of the modern scientific and engineering enterprise, we argue that the biomaterials community needs to proactively address ethical issues in the field by, for example, updating or adding specificity to codes of ethics, modifying training programs to highlight the importance of ethical research practices, and partnering with funding agencies and journals to adopt policies prioritizing the ethical conduct of biomaterials research. Together these actions can strengthen and support biomaterials as its advances are increasingly commercialized and impacting the health care system.

Engineering physical microenvironments to study innate immune cell biophysics

Innate immunity forms the core of the human body's defense system against infection, injury, and foreign objects. It aims to maintain homeostasis by promoting inflammation and then initiating tissue repair, but it can also lead to disease when dysregulated. Although innate immune cells respond to their physical microenvironment and carry out intrinsically mechanical actions such as migration and phagocytosis, we still do not have a complete biophysical description of innate immunity. Here, we review how engineering tools can be used to study innate immune cell biophysics. We first provide an overview of innate immunity from a biophysical perspective, review the biophysical factors that affect the innate immune system, and then explore innate immune cell biophysics in the context of migration, phagocytosis, and phenotype polarization. Throughout the review, we highlight how physical microenvironments can be designed to probe the innate immune system, discuss how biophysical insight gained from these studies can be used to generate a more comprehensive description of innate immunity, and briefly comment on how this insight could be used to develop mechanical immune biomarkers and immunomodulatory therapies.

Application of 3D-Printed, PLGA-Based Scaffolds in Bone Tissue Engineering

Polylactic acid–glycolic acid (PLGA) has been widely used in bone tissue engineering due to its favorable biocompatibility and adjustable biodegradation. 3D printing technology can prepare scaffolds with rich structure and function, and is one of the best methods to obtain scaffolds for bone tissue repair. This review systematically summarizes the research progress of 3D-printed, PLGA-based scaffolds. The properties of the modified components of scaffolds are introduced in detail. The influence of structure and printing method change in printing process is analyzed. The advantages and disadvantages of their applications are illustrated by several examples. Finally, we briefly discuss the limitations and future development direction of current 3D-printed, PLGA-based materials for bone tissue repair.

Engineering microbial systems for the production and functionalization of biomaterialsBiomaterials engineering with microorganisms

A new trend in biomaterials synthesis is harnessing the production of microorganisms, owing to the low cost and sustainability. Because microorganisms use DNA as a production code, it is possible for humans to reprogram these cells and thus build living factories for the production of biomaterials. Over the past decade, advances in genetic engineering have enabled the development of various intriguing biomaterials with useful properties, with commercially available biomaterials representing only a few of these. In this review, we discuss the common strategies for the production of bulk and commodity biogenic polymers, and highlight several notable approaches such as modular protein engineering and pathway optimization in achieving these goals. We finally investigate the available synthetic biology tools that allow engineering of living materials, and discuss how this emerging class of materials has expanded the application scope of biomaterials.

Visible-Light-Mediated Nano-biomineralization of Customizable Tough Hydrogels for Biomimetic Tissue Engineering

Biomineralized tough hydrogels (BTHs) have advanced applications in the fields of soft bioelectronics and biomimetic tissue engineering. But the development of rapid and general photomineralization strategies for one-step fabrication of customizable BTHs is still a challenging task. Here we report a straightforward, low-cost visible-light-mediated nano-biomineralization (VLMNB) strategy via a rational design of a phosphate source and efficient ruthenium photochemistry. Multinetwork tough hydrogels are simultaneously constructed under the same condition. Therefore, BTHs are rapidly prepared in a short time as low as ∼60 s under visible light irradiation. The in situ formation of calcium phosphate particles can improve BTHs' mechanical and biological properties and reduce the friction coefficient with bones. Furthermore, fast biomineralization and solidification processes in these BTHs benefit their injectable and highly flexible customizable design, showing applications of promoting customizable skin repair and bone regeneration.

Composite alginate-gelatin hydrogels incorporating PRGF enhance human dental pulp cell adhesion, chemotaxis and proliferation

The increasing prevalence of tissue injuries is fueling the development of autologous biological treatments for regenerative medicine. Here, we investigated the potential of three different bioinks based on the combination of gelatin and alginate (GA), enriched in either hydroxyapatite (GAHA) or hydroxyapatite and PRGF (GAHAP), as a favorable microenvironment for human dental pulp stem cells (DPSCs). Swelling behaviour, in vitro degradation and mechanical properties of the matrices were evaluated. Morphological and elemental analysis of the scaffolds were also performed along with cytocompatibility studies. The in vitro cell response to the different scaffolds was also assessed. Results showed that all scaffolds presented high swelling capacity, and those that contained HA showed higher Young's modulus. GAHAP had the lowest degradation rate and the highest values of cytocompatibility. Cell adhesion and chemotaxis were significantly increased when PRGF was incorporated to the matrices. GAHA and GAHAP compositions promoted the highest proliferative rate as well as significantly stimulated osteogenic differentiation. In conclusion, the enrichment with PRGF improves the regenerative properties of the composites favouring the development of personalized constructs.

Aldehyde-methacrylate-hyaluronan profited hydrogel system integrating aligned and viscoelastic cues for neurogenesis

Either oriented architecture or viscoelasticity is pivotal to neurogenesis, thus, native neural extracellular matrix derived-hyaluronan hydrogels with nano-orientation and viscoelasticity recapitulated might be instructive for neurogenesis, however it is still unexploited. Herein, based on aldehyde-methacrylate difunctionalized hyaluronan, by integrating imine kinetic modulation and microfluidic biofabrication, we construct a hydrogel system with orthogonal viscoelasticity and nano-topography. We then find the positive synergy effects of matrix nano-orientation and viscoelasticity not only on neurites outgrowth and elongation of neural cells, but also on neuronal differentiation of stem cells. Moreover, by implanting viscoelastic and nano-aligned hydrogels into lesion sites, we demonstrate the enhanced repair of spinal cord injury, including ameliorated pathological microenvironment, facilitated endogenous neurogenesis and functional axons regeneration as well as motor function restoration. This work supplies universal platform for preparing neuronal inducing hyaluronan-based hydrogels which might serve as promising therapeutic strategies for nerve injury.

Electroconductive biomaterials for cardiac tissue engineering

Myocardial infarction (MI) is still the leading cause of mortality worldwide. The success of cell-based therapies and tissue engineering strategies for treatment of injured myocardium have been notably hindered due to the limitations associated with the selection of a proper cell source, lack of engraftment of engineered tissues and biomaterials with the host myocardium, limited vascularity, as well as immaturity of the injected cells. The first-generation approaches in cardiac tissue engineering (cTE) have mainly relied on the use of desired cells (e.g., stem cells) along with non-conductive natural or synthetic biomaterials for in vitro construction and maturation of functional cardiac tissues, followed by testing the efficacy of the engineered tissues in vivo. However, to better recapitulate the native characteristics and conductivity of the cardiac muscle, recent approaches have utilized electroconductive biomaterials or nanomaterial components within engineered cardiac tissues. This review article will cover the recent advancements in the use of electrically conductive biomaterials in cTE. The specific emphasis will be placed on the use of different types of nanomaterials such as gold nanoparticles (GNPs), silicon-derived nanomaterials, carbon-based nanomaterials (CBNs), as well as electroconductive polymers (ECPs) for engineering of functional and electrically conductive cardiac tissues. We will also cover the recent progress in the use of engineered electroconductive tissues for in vivo cardiac regeneration applications. We will discuss the opportunities and challenges of each approach and provide our perspectives on potential avenues for enhanced cTE. STATEMENT OF SIGNIFICANCE: Myocardial infarction (MI) is still the primary cause of death worldwide. Over the past decade, electroconductive biomaterials have increasingly been applied in the field of cardiac tissue engineering. This review article provides the readers with the leading advances in the in vitro applications of electroconductive biomaterials for cTE along with an in-depth discussion of injectable/transplantable electroconductive biomaterials and their delivery methods for in vivo MI treatment. The article also discusses the knowledge gaps in the field and offers possible novel avenues for improved cardiac tissue engineering.

Construction of a drug-containing microenvironment for in situ bone regeneration

Bioactive glass-coated hierarchical porous tricalcium phosphate ceramics were constructed as both bone scaffolds and drug delivery devices to treat S. aureus-infected bone defects.