A Bioinspired Scaffold with Anti-Inflammatory Magnesium Hydroxide and Decellularized Extracellular Matrix for Renal Tissue Regeneration

Manufacture Dependent Differential Biodegradation of 3D Printed Shape Memory Polymers

In the field of tissue engineering, 3D printed shape memory polymers (SMPs) are drawing increased interest. Understanding how these 3D printed SMPs degrade is critical for their use in the clinic, as small changes in material properties can significantly change how they behave after in vivo implantation. Degradation of 3D printed acrylated poly(glycerol-dodecanedioate) (APGD) was examined via in vitro hydrolytic, enzymatic, and in vivo subcutaneous implantation assays. Three APGD manufacturing modalities were assessed to determine differences in degradation. Material extrusion samples showed significantly larger mass and volume loss at 2 months, compared to lasercut and vat photopolymerization samples, under both enzymatic and in vivo degradation. Critically, melt transition temperatures of degraded PGD increased over time in vitro, but not in vivo. Histology of tissue surrounding APGD implants showed no significant signs of inflammation compared to controls, providing a promising outlook for use of 3D printed APGD devices in the clinic.

Degradation-controlled tissue extracellular sponge for rapid hemostasis and wound repair after kidney injury

Patients diagnosed with T1a cancer undergo partial nephrectomy to remove the tumors. In the process of removing the tumors, loss of kidney volume is inevitable, and current surgical methods focus solely on hemostasis and wound closure. Here, we developed an implantable form of decellularized extracellular matrix sponge to target both hemostasis and wound healing at the lesion site. A porous form of kidney decellularized matrix was achieved by fabricating a chemically cross-linked cryogel followed by lyophilization. The prepared kidney decellularized extracellular matrix sponge (kdES) was then characterized for features relevant to a hemostasis as well as a biocompatible and degradable biomaterial. Finally, histological evaluations were made after implantation in rat kidney incision model. Both gelatin sponge and kdES displayed excellent hemocompatibility and biocompatibility. However, after a 4-week observation period, kdES exhibited more favorable wound healing results at the lesion site. This suggests a promising potential for kdES as a supportive material in facilitating wound closure during partial nephrectomy surgery. KdES not only achieved rapid hemostasis for managing renal hemorrhage that is comparable to commercial hemostatic sponges, but also demonstrated superior wound healing outcomes.

Double-Layer Asymmetric Porous Mesh with Dynamic Mechanical Support Properties Enables Efficient Single-Stage Repair of Contaminated Abdominal Wall Defect

Contamination tolerance and long-term mechanical support are the two critical properties of meshes for contaminated abdominal wall defect repair. However, biological meshes with excellent pollution tolerance fail to provide bio-adaptive long-term mechanical support due to their rapid degradation. Here, a novel double-layer asymmetric porous mesh (SIS/PVA-EXO) is designed by simple and efficient in situ freeze-thaw of sticky polyvinyl alcohol (PVA) solution on the loosely porous surface of small intestinal submucosal decellularized matrix (SIS), which can successfully repair the contaminated abdominal wall defect with bio-adaptive dynamic mechanical support through only single-stage surgery. The exosome-loaded degradable loosely porous SIS layer accelerates the tissue healing; meanwhile, the exosome-loaded densely porous PVA layer can maintain long-term mechanical support without any abdominal adhesion. In addition, the tensile strength and strain at break of SIS/PVA-EXO mesh change gradually from 0.37 MPa and 210% to 0.10 MPa and 385% with the degradation of SIS layer. This unique performance can dynamically adapt to the variable mechanical demands during different periods of contaminated abdominal wall reconstruction. As a result, this SIS/PVA-EXO mesh shows an attractive prospect in the treatment of contaminated abdominal wall defect without recurrence by integrating local immune regulation, tissue remodeling, and dynamic mechanical supporting.

Multiplexed PLGA scaffolds with nitric oxide-releasing zinc oxide and melatonin-modulated extracellular vesicles for severe chronic kidney disease

INTRODUCTION

With prevalence of chronic kidney disease (CKD) in worldwide, the strategies to recover renal function via tissue regeneration could provide alternatives to kidney replacement therapies. However, due to relatively low reproducibility of renal basal cells and limited bioactivities of implanted biomaterials along with the high probability of substance-inducible inflammation and immunogenicity, kidney tissue regeneration could be challenging.

OBJECTIVES

To exclude various side effects from cell transplantations, in this study, we have induced extracellular vesicles (EVs) incorporated cell-free hybrid PMEZ scaffolds.

METHODS

Hybrid PMEZ scaffolds incorporating essential bioactive components, such as ricinoleic acid grafted Mg(OH)2 (M), extracellular matrix (E), and alpha lipoic acid-conjugated ZnO (Z) based on biodegradable porous PLGA (P) platform was successfully manufactured. Consecutively, for functional improvements, melatonin-modulated extracellular vesicles (mEVs), derived from the human umbilical cord MSCs in chemically defined media without serum impurities, were also loaded onto PMEZ scaffolds to construct the multiplexed PMEZ/mEV scaffold.

RESULTS

With functionalities of Mg(OH)2 and extracellular matrix-loaded PLGA scaffolds, the continuous nitric oxide-releasing property of modified ZnO and remarkably upregulated regenerative functionalities of mEVs showed significantly enhanced kidney regenerative activities. Based on these, the structural and functional restoration has been practically achieved in 5/6 nephrectomy mouse models that mimicked severe human CKD.

CONCLUSION

Our study has proved the combinatory bioactivities of the biodegradable PLGA-based multiplexed scaffold for kidney tissue regeneration in 5/6 nephrectomy mouse representing a severe CKD model. The optimal microenvironments for the morphogenetic formations of renal tissues and functional restorations have successfully achieved the combinatory bioactivities of remarkable components for PMEZ/mEV, which could be a promising therapeutic alternative for CKD treatment.

Application of Cartilage Extracellular Matrix to Enhance Therapeutic Efficacy of Methotrexate

BACKGROUND

Rheumatoid arthritis (RA) is characterized by chronic inflammation and joint damage. Methotrexate (MTX), a commonly used disease-modifying anti-rheumatic drug (DMARD) used in RA treatment. However, the continued use of DMARDs can cause adverse effects and result in limited therapeutic efficacy. Cartilage extracellular matrix (CECM) has anti-inflammatory and anti-vascular effects and promotes stem cell migration, adhesion, and differentiation into cartilage cells.

METHODS

CECM was assessed the dsDNA, glycosaminoglycan, collagen contents and FT-IR spectrum of CECM. Furthermore, we determined the effects of CECM and MTX on cytocompatibility in the SW 982 cells and RAW 264.7 cells. The anti-inflammatory effects of CECM and MTX were assessed using macrophage cells. Finally, we examined the in vivo effects of CECM in combination with MTX on anti-inflammation control and cartilage degradation in collagen-induced arthritis model. Anti-inflammation control and cartilage degradation were assessed by measuring the serum levels of RA-related cytokines and histology.

RESULTS

CECM in combination with MTX had no effect on SW 982, effectively suppressing only RAW 264.7 activity. Moreover, anti-inflammatory effects were enhanced when low-dose MTX was combined with CECM. In a collagen-induced arthritis model, low-dose MTX combined with CECM remarkably reduced RA-related and pro-inflammatory cytokine levels in the blood. Additionally, low-dose MTX combined with CECM exerted the best cartilage-preservation effects compared to those observed in the other therapy groups.

CONCLUSION

Using CECM as an adjuvant in RA treatment can augment the therapeutic effects of MTX, reduce existing drug adverse effects, and promote joint tissue regeneration.

Three Birds, One Stone: An Osteo-Microenvironment Stage-Regulative Scaffold for Bone Defect Repair through Modulating Early Osteo-Immunomodulation, Middle Neovascularization, and Later Osteogenesis

In order to repair critical-sized bone defects, various polylactic acid-glycolic acid (PLGA)-based hybrid scaffolds are successfully developed as bone substitutes. However, the byproducts of these PLGA-based scaffolds are known to acidify the implanted site, inducing tiresome acidic inflammation. Moreover, these degradation productions cannot offer an osteo-friendly microenvironment at the implanted site, matching natural bone healing. Herein, inspired by bone microenvironment atlas of natural bone-healing process, an osteo-microenvironment stage-regulative scaffold (P80/D10/M10) is fabricated by incorporating self-developed decellularized bone matrix microparticles (DBM-MPs) and multifunctional magnesium hydroxide nanoparticles (MH-NPs) into PLGA with an optimized proportion using low-temperature rapid prototyping (LT-RP) 3D-printing technology. The cell experiments show that this P80/D10/M10 exhibits excellent properties in mechanics, biocompatibility, and biodegradability, meanwhile superior stimulations in osteo-immunomodulation, angiogenesis, and osteogenesis. Additionally, the animal experiments determined that this P80/D10/M10 can offer an osteo-friendly microenvironment in a stage-matched pattern for enhanced bone regeneration, namely, optimization of early inflammation, middle neovascularization, and later bone formation. Furthermore, transcriptomic analysis suggested that the in vivo performance of P80/D10/M10 on bone defect repair is mostly attributed to regulating artery development, bone development, and bone remodeling. Overall, this study reveals that the osteo-microenvironment stage-regulative scaffold provides a promising treatment for bone defect repair.

Antioxidant and anti-inflammatory injectable hydrogel microspheres for in situ treatment of tendinopathy

Tendinopathy is a common disorder that causes local dysfunction and reduces quality of life. Recent research has indicated that alterations in the inflammatory microenvironment play a vital role in the pathogenesis of tendinopathy. Herein, injectable methacrylate gelatin (GelMA) microspheres (GM) were fabricated and loaded with heparin-dopamine conjugate (HDC) and hepatocyte growth factor (HGF). GM@HDC@HGF were designed to balance the inflammatory microenvironment by inhibiting oxidative stress and inflammation, thereby regulating extracellular matrix (ECM) metabolism and halting tendon degeneration. Combining growth factors with heparin was expected to improve the encapsulation rate and maintain the long-term efficacy of HGF. In addition, the catechol groups on dopamine have adhesion and antioxidant properties, allowing potential attachment at the injured site, and better function synergized with HGF. GM@HDC@HGF injected in situ in rat Achilles tendinopathy (AT) models significantly down-regulated oxidative stress and inflammation, and ameliorated ECM degradation. In conclusion, the multifunctional platform developed presents a promising alternative for the treatment of tendinopathy.

Additively manufactured porous scaffolds by design for treatment of bone defects

There has been increasing attention to produce porous scaffolds that mimic human bone properties for enhancement of tissue ingrowth, regeneration, and integration. Additive manufacturing (AM) technologies, i.e., three dimensional (3D) printing, have played a substantial role in engineering porous scaffolds for clinical applications owing to their high level of design and fabrication flexibility. To this end, this review article attempts to provide a detailed overview on the main design considerations of porous scaffolds such as permeability, adhesion, vascularisation, and interfacial features and their interplay to affect bone regeneration and osseointegration. Physiology of bone regeneration was initially explained that was followed by analysing the impacts of porosity, pore size, permeability and surface chemistry of porous scaffolds on bone regeneration in defects. Importantly, major 3D printing methods employed for fabrication of porous bone substitutes were also discussed. Advancements of MA technologies have allowed for the production of bone scaffolds with complex geometries in polymers, composites and metals with well-tailored architectural, mechanical, and mass transport features. In this way, a particular attention was devoted to reviewing 3D printed scaffolds with triply periodic minimal surface (TPMS) geometries that mimic the hierarchical structure of human bones. In overall, this review enlighten a design pathway to produce patient-specific 3D-printed bone substitutions with high regeneration and osseointegration capacity for repairing large bone defects.

Kidney tissue regeneration using bioactive scaffolds incorporated with differentiating extracellular vesicles and intermediate mesoderm cells

BACKGROUND

To overcome the limitations of current alternative therapies for chronic kidney disease (CKD), tissue engineering-mediated regeneration strategies have demonstrated the possibilities for complete kidney tissue regeneration. Given the challenges associated with the reproducibility of renal basal cells, the incorporation of intermediate mesoderm (IM) cells and bioactive materials to control bioactivities of cells with supported scaffolds should be considered as a viable approach to enable the regeneration of the complex kidney structure via renal differentiation.

METHODS

We developed PMEZ scaffolds by combining crucial bioactive components, such as ricinoleic acid-grafted Mg(OH)2 (M), extracellular matrix (E), and alpha lipoic acid-conjugated ZnO (Z) integrated into biodegradable porous PLGA (P) platform. Additionally, we utilized differentiating extracellular vesicles (dEV) isolated during intermediate mesoderm differentiation into kidney progenitor cells, and IM cells were serially incorporated to facilitate kidney tissue regeneration through their differentiation into kidney progenitor cells in the 3/4 nephrectomy mouse model.

RESULTS

The use of differentiating extracellular vesicles facilitated IM differentiation into kidney progenitor cells without additional differentiation factors. This led to improvements in various regeneration-related bioactivities including tubule and podocyte regeneration, anti-fibrosis, angiogenesis, and anti-inflammation. Finally, implanting PMEZ/dEV/IM scaffolds in mouse injury model resulted in the restoration of kidney function.

CONCLUSIONS

Our study has demonstrated that utilizing biodegradable PLGA-based scaffolds, which include multipotent cells capable of differentiating into various kidney progenitor cells along with supporting components, can facilitate kidney tissue regeneration in the mouse model that simulates CKD through 3/4 nephrectomy.

Electrochemical Detection of Dopamine Release from Living Neurons Using Graphene Oxide-Incorporated Polypyrrole/Gold Nanocluster Hybrid Nanopattern Arrays

Stem-cell-based therapeutics have shown immense potential in treating various diseases that are currently incurable. In particular, partial recovery of Parkinson's disease, which occurs due to massive loss or abnormal functionality of dopaminergic (DAnergic) neurons, through the engraftment of stem-cell-derived neurons ex vivo is reported. However, precise assessment of the functionality and maturity of DAnergic neurons is still challenging for their enhanced clinical efficacy. Here, a novel conductive cell cultivation platform, a graphene oxide (GO)-incorporated metallic polymer nanopillar array (GOMPON), that can electrochemically detect dopamine (DA) exocytosis from living DAnergic neurons, is reported. In the cell-free configuration, the linear range is 0.5-100 µm, with a limit of detection of 33.4 nm. Owing to its excellent biocompatibility, a model DAnergic neuron (SH-SY5Y cell) can be cultivated and differentiated on the platform while their DA release can be quantitatively measured in a real-time and nondestructive manner. Finally, it is showed that the functionality of the DAnergic neurons derived from stem cells can be precisely assessed via electrochemical detection of their DA exocytosis. The developed GOMPON is highly promising for a wide range of applications, including real-time monitoring of stem cell differentiation into neuronal lineages, evaluating differentiation protocols, and finding practical stem cell therapies.

Polylactide Degradation Activates Immune Cells by Metabolic Reprogramming

Polylactide (PLA) is the most widely utilized biopolymer in medicine. However, chronic inflammation and excessive fibrosis resulting from its degradation remain significant obstacles to extended clinical use. Immune cell activation has been correlated to the acidity of breakdown products, yet methods to neutralize the pH have not significantly reduced adverse responses. Using a bioenergetic model, delayed cellular changes were observed that are not apparent in the short-term. Amorphous and semi-crystalline PLA degradation products, including monomeric l-lactic acid, mechanistically remodel metabolism in cells leading to a reactive immune microenvironment characterized by elevated proinflammatory cytokines. Selective inhibition of metabolic reprogramming and altered bioenergetics both reduce these undesirable high cytokine levels and stimulate anti-inflammatory signals. The results present a new biocompatibility paradigm by identifying metabolism as a target for immunomodulation to increase tolerance to biomaterials, ensuring safe clinical application of PLA-based implants for soft- and hard-tissue regeneration, and advancing nanomedicine and drug delivery.

Decellularized Scaffolds with Double-Layer Aligned Microchannels Induce the Oriented Growth of Bladder Smooth Muscle Cells: Toward Urethral and Ureteral Reconstruction

There is a great clinical need for regenerating urinary tissue. Native urethras and ureters have bidirectional aligned smooth muscle cells (SMCs) layers, which plays a pivotal role in micturition and transporting urine and inhibiting reflux. Thus far, urinary scaffolds have not been designed to induce the native-mimicking aligned arrangement of SMCs. In this study, a tubular decellularized extracellular matrix (dECM) with an intact internal layer and bidirectional aligned microchannels in the tubular wall, which is realized by the subcutaneous implantation of a template, followed by the removal of the template, and decellularization, is engineered. The dense and intact internal layer effectively increases the leakage pressure of the tubular dECM scaffolds. Rat-derived dECM scaffolds with three different sizes of microchannels are fabricated by tailoring the fiber diameter of the templates. The rat-derived dECM scaffolds exhibiting microchannels of ≈65 µm show suitable mechanical properties, good ability to induce the bidirectional alignment and growth of human bladder SMCs, and elevated higher functional protein expression in vitro. These data indicate that rat-derived tubular dECM scaffolds manifesting double-layer aligned microchannels may be promising candidates to induce the native-mimicking regeneration of SMCs in urethra and ureter reconstruction.

3D Cell Printing of Advanced Vascularized Proximal Tubule-on-a-Chip for Drug Induced Nephrotoxicity Advancement

Renal dysfunction due to drug-induced nephrotoxicity (DIN) affects >20% of the adult population worldwide. The vascularized proximal tubule is a complex structure that is often the primary site of drug-induced kidney injury. Herein, a vascularized proximal tubule-on-a-chip (Vas-POAC) was fabricated, demonstrating improved physiological emulation over earlier single-cell proximal tubule models. A perfusable model of vascularized proximal tubules permits the growth and proliferation of renal proximal tubule cells and adjacent endothelial cells under various conditions. An in vitro Vas-POAC showed mature expressions of the tubule and endothelial cell markers in the mature epithelium and endothelium lumens after 7 days of culture. Expression in the mature proximal tubule epithelium resembled the polarized expression of sodium-glucose cotransporter-2 and the de novo synthesis of ECM proteins. These perfusable Vas-POACs display significantly improved functional properties relative to the proximal tubules-on-a-chip (POAC), which lacks vascular components. Furthermore, the developed Vas-POAC model evaluated the cisplatin-induced nephrotoxicity and revealed enhanced drug receptivity compared to POAC. We further evaluated the capability of the developed proximal tubule model to act as a functional platform that targets screening drug doses that can cause renal proximal tubule injury in adults. Thus, our cell-printed models may prove valuable for screening, thoughtful mechanistic investigations of DIN, and discovery of drugs that interfere with tubule formation.

Bioactive and Hemocompatible PLA/Lignin Bio-Composites: Assessment of In Vitro Antioxidant Activity for Biomedical Applications

In this study, acetylated soda lignin (ASL) and non-acetylated soda lignin (SL) were extruded with PLA in different concentrations to fabricate antioxidant polylactic acid (PLA)/lignin composites for potential biomedical applications. After lignin acetylation, good compatibility was observed between PLA and lignin in scanning electron microscopy images. All the PLA/ASL composites displayed higher mechanical properties than PLA/SL composites. PLA/ASL5 displayed the highest mechanical characteristics with elongation at break of 10% and tensile strength of 57 MPa, while PLA/SL15 and PLA/SL20 demonstrated superior UV-blocking potential with UV transmittance less than 10%. Addition of ASL in PLA lead to an increase in the hydrophobic character, with all the PLA/ASL displaying a higher water contact angle. The antioxidant test using 2,2-diphenyl-1-picrylhydrazyl assay showed that PLA/SL composites rendered superior radical scavenging activity (RSA), with PLA/SL20 composites displaying an RSA of 80%. Furthermore, in vitro antioxidant activity and cytocompatibility were analyzed using human colon cancer cells (HCT-15) and gastric epithelial cells (NCC-24). In vitro antioxidant activity, evaluated by H2O2 exposure was confirmed by a live/dead assay. PLA/SL composites protected both types of cells from oxidative stress. In addition, all PLA/SL and PLA/ASL composites promoted cell proliferation compared to PLA. PLA/SL5 and PLA/SL10 displayed the highest cell proliferation of all composites. Lastly, all PLA/SL and PLA/ASL composites had a hemoglobin release less than 2%. The antioxidant properties, cytocompatibility, and hemocompatibility of lignin/PLA demonstrated in our study indicate that these lignin/PLA composites possess the desirable attributes for potential biomedical applications.

Renal tissue engineering for regenerative medicine using polymers and hydrogels

Chronic Kidney Disease (CKD) is a growing worldwide problem, leading to end-stage renal disease (ESRD). Current treatments for ESRD include haemodialysis and kidney transplantation, but both are deemed inadequate since haemodialysis does not address all other kidney functions, and there is a shortage of suitable donor organs for transplantation. Research in kidney tissue engineering has been initiated to take a regenerative medicine approach as a potential treatment alternative, either to develop effective cell therapy for reconstruction or engineer a functioning bioartificial kidney. Currently, renal tissue engineering encompasses various materials, mainly polymers and hydrogels, which have been chosen to recreate the sophisticated kidney architecture. It is essential to address the chemical and mechanical aspects of the materials to ensure they can support cell development to restore functionality and feasibility. This paper reviews the types of polymers and hydrogels that have been used in kidney tissue engineering applications, both natural and synthetic, focusing on the processing and formulation used in creating bioactive substrates and how these biomaterials affect the cell biology of the kidney cells used.

Alkaline earth metals for osteogenic scaffolds: From mechanisms to applications

Regeneration of bone defects is a significant challenge today. As alternative approaches to the autologous bone, scaffold materials have remarkable features in treating bone defects; however, the various properties of current scaffold materials still fall short of expectations. Due to the osteogenic capability of alkaline earth metals, their application in scaffold materials has become an effective approach to improving their properties. Furthermore, numerous studies have shown that combining alkaline earth metals leads to better osteogenic properties than applying them alone. In this review, the physicochemical and physiological characteristics of alkaline earth metals are introduced, mainly focusing on their mechanisms and applications in osteogenesis, especially magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Furthermore, this review highlights the possible cross-talk between pathways when alkaline earth metals are combined. Finally, some of the current drawbacks of scaffold materials are enumerated, such as the high corrosion rate of Mg scaffolds and defects in the mechanical properties of Ca scaffolds. Moreover, a brief perspective is also provided regarding future directions in this field. It is worth exploring that whether the levels of alkaline earth metals in newly regenerated bone differs from those in normal bone. The ideal ratio of each element in the bone tissue engineering scaffolds or the optimal concentration of each elemental ion in the created osteogenic environment still needs further exploration. The review not only summarizes the research developments in osteogenesis but also offers a direction for developing new scaffold materials.

Multi-modulation of immune-inflammatory response using bioactive molecule-integrated PLGA composite for spinal fusion

Despite current developments in bone substitute technology for spinal fusion, there is a lack of adequate materials for bone regeneration in clinical applications. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is commercially available, but a severe inflammatory response is a known side effect. Bone graft substitutes that enhance osteogenesis without adverse effects are needed. We developed a bioactive molecule-laden PLGA composite with multi-modulation for bone fusion. This bioresorbable composite scaffold was considered for bone tissue engineering. Among the main components, magnesium hydroxide (MH) aids in reduction of acute inflammation affecting disruption of new bone formation. Decellularized bone extracellular matrix (bECM) and demineralized bone matrix (DBM) composites were used for osteoconductive and osteoinductive activities. A bioactive molecule, polydeoxyribonucleotide (PDRN, PN), derived from trout was used for angiogenesis during bone regeneration. A nano-emulsion method that included Span 80 was used to fabricate bioactive PLGA-MH-bECM/DBM-PDRN (PME2/PN) composite to obtain a highly effective and safe scaffold. The synergistic effect provided by PME2/PN improved not only osteogenic and angiogenic gene expression for bone fusion but also improved immunosuppression and polarization of macrophages that were important for bone tissue repair, using a rat model of posterolateral spinal fusion (PLF). It thus had sufficient biocompatibility and bioactivity for spinal fusion.

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.

Preparation of Nano-Mg(OH)2 and Its Flame Retardant and Antibacterial Modification on Polyethylene Terephthalate Fabrics

The multifunctional polyethylene terephthalate (PET) fabrics were successfully prepared through a dip-coating technology to endow the flame retardant and antibacterial properties of PET fabrics, which are extensively used in many fields. The flame retardant and antibacterial agent was synthesized by a double drop-reverse precipitation method and surface-modified by the mixtures of titanate coupling agents and stearic acid to result in a good compatibility of the hydrophilic nano-Mg(OH)₂ and the hydrophobic PET fabrics. The results indicated that the suitable synthesis conditions of nano-Mg(OH)₂ are: Mg²⁺ concentration 1.5 mg/mL, reaction temperature 50 °C and reaction time 50 min, and the optimal modification conditions of nano-Mg(OH)₂ are: modifier ratio 5/5, modification temperature 70 °C and modification time 40 min. The flame retardant test and the antibacterial test showed that the multifunctional PET fabrics had excellent flame retardant and antibacterial properties.

Additive Manufacturing of Polymer/Mg-Based Composites for Porous Tissue Scaffolds

Due to their commercial availability, superior processability, and biocompatibility, polymers are frequently used to build three-dimensional (3D) porous scaffolds. The main issues limiting the widespread clinical use of monophasic polymer scaffolds in the bone healing process are their inadequate mechanical strength and inappropriate biodegradation. Due to their mechanical strength and biocompatibility, metal-based scaffolds have been used for various bone regenerative applications. However, due to the mismatch in mechanical properties and nondegradability, they lack integration with the host tissues, resulting in the production of fiber tissue and the release of toxic ions, posing a risk to the durability of scaffolds. Due to their natural degradability in the body, Mg and its alloys increasingly attract attention for orthopedic and cardiovascular applications. Incorporating Mg micro-nano-scale particles into biodegradable polymers dramatically improves scaffolds and implants' strength, biocompatibility, and biodegradability. Polymer biodegradable implants also improve the quality of life, particularly for an aging society, by eliminating the secondary surgery often needed to remove permanent implants and significantly reducing healthcare costs. This paper reviews the suitability of various biodegradable polymer/Mg composites for bone tissue scaffolds and then summarizes the current status and challenges of polymer/magnesium composite scaffolds. In addition, this paper reviews the potential use of 3D printing, which has a unique design capability for developing complex structures with fewer material waste at a faster rate, and with a personalized and on-site fabrication possibility.

Role of extracellular matrix components and structure in new renal models in vitro

The extracellular matrix (ECM), a complex set of fibrillar proteins and proteoglycans, supports the renal parenchyma and provides biomechanical and biochemical cues critical for spatial-temporal patterning of cell development and acquisition of specialized functions. As in vitro models progress towards biomimicry, more attention is paid to reproducing ECM-mediated stimuli. ECM's role in in vitro models of renal function and disease used to investigate kidney injury and regeneration is discussed. Availability, affordability, and lot-to-lot consistency are the main factors determining the selection of materials to recreate ECM in vitro. While simpler components can be synthesized in vitro, others must be isolated from animal or human tissues, either as single isolated components or as complex mixtures, such as Matrigel or decellularized formulations. Synthetic polymeric materials with dynamic and instructive capacities are also being explored for cell mechanical support to overcome the issues with natural products. ECM components can be used as simple 2D coatings or complex 3D scaffolds combining natural and synthetic materials. The goal is to recreate the biochemical signals provided by glycosaminoglycans and other signaling molecules, together with the stiffness, elasticity, segmentation, and dimensionality of the original kidney tissue, to support the specialized functions of glomerular, tubular, and vascular compartments. ECM mimicking also plays a central role in recent developments aiming to reproduce renal tissue in vitro or even in therapeutical strategies to regenerate renal function. Bioprinting of renal tubules, recellularization of kidney ECM scaffolds, and development of kidney organoids are examples. Future solutions will probably combine these technologies.

Factors Controlling Degradation of Biologically Relevant Synthetic Polymers in Solution and Solid State

The field of biodegradable synthetic polymers, which is central for regenerative engineering and drug delivery applications, encompasses a multitude of hydrolytically sensitive macromolecular structures and diverse processing approaches. The ideal degradation behavior for a specific life science application must comply with a set of requirements, which include a clinically relevant kinetic profile, adequate biocompatibility, benign degradation products, and controlled structural evolution. Although significant advances have been made in tailoring materials characteristics to satisfy these requirements, the impacts of autocatalytic reactions and microenvironments are often overlooked resulting in uncontrollable and unpredictable outcomes. Therefore, roles of surface versus bulk erosion, in situ microenvironment, and autocatalytic mechanisms should be understood to enable rational design of degradable systems. In an attempt to individually evaluate the physical state and form factors influencing autocatalytic hydrolysis of degradable polymers, this Review follows a hierarchical analysis that starts with hydrolytic degradation of water-soluble polymers before building up to 2D-like materials, such as ultrathin coatings and capsules, and then to solid-state degradation. We argue that chemical reactivity largely governs solution degradation while diffusivity and geometry control the degradation of bulk materials, with thin "2D" materials remaining largely unexplored. Following this classification, this Review explores techniques to analyze degradation in vitro and in vivo and summarizes recent advances toward understanding degradation behavior for traditional and innovative polymer systems. Finally, we highlight challenges encountered in analytical methodology and standardization of results and provide perspective on the future trends in the development of biodegradable polymers.

Dendrimer-based delivery of macromolecules for the treatment of brain tumor

Brain tumor represents the most lethal form of cancer with the highest mortality and morbidity rates irrespective of age and sex. Advancements in macromolecule-based therapy (such as nucleic acids and peptides) have shown promising roles in the treatment of brain tumor where the phenomenon of severe toxicities due to the conventional chemotherapeutic agents can be circumvented. Despite its preclinical progress, successful targeting of these macromolecules across the blood-brain barrier without altering their physical and chemical characteristics is of great challenge. With the advent of nanotechnology, nowadays targeted delivery of therapeutics is being explored extensively and these macromolecules, including peptides and nucleic acids, have shown initial success in the treatment, where dendrimer has shown its potential for optimal delivery. Dendrimers are being favored as a mode of drug delivery due to their nano-spherical size and structure, high solubilization potential, multivalent surface, and high loading capacity, where biomolecule resembling characteristics of dendritic 3D structures has shown effective delivery of various therapeutic agents to the brain. Armed with targeting ligands to these dendrimers further expedite the transportation of these multifunctional shuttles specifically to the glioblastoma cells. Thus, a focus has been made in this review on therapeutic applications of dendrimer platforms in brain tumor treatment. The future development of dendrimers as a potential platform for nucleic acid and peptide delivery and its promising clinical application could provide effective and target-specific treatment against brain tumors.

Kidney tissue engineering in preclinical models of renal failure: a systematic review and meta-analysis

Aim: This study aims to compare the efficacy of tissue engineering for kidney reconstruction. Materials & methods: We searched MEDLINE, EMBASE (May 2021), and reference lists of review articles. Results: 19 articles matched our inclusion criteria. A range of natural, synthetic and hybrid scaffolds with or without incorporating cells/growth factors was investigated in 937 animals. More favorable results were observed with a combination of two or more biomaterials, addition of bioactive moieties, and cell seeding. Creatinine concentration, PAX2, collagen type-1, α-SMA, vimentin, IL-1, IL-6 and TNF-α gene expressions were significantly increased compared with native control. Conclusion: Tissue engineering can improve renal function and regeneration; however, further research could benefit from using hybrid scaffolds, stem cells and large animal models.

Human SMILE-Derived Stromal Lenticule Scaffold for Regenerative Therapy: Review and Perspectives

A transparent cornea is paramount for vision. Corneal opacity is one of the leading causes of blindness. Although conventional corneal transplantation has been successful in recovering patients’ vision, the outcomes are challenged by a global lack of donor tissue availability. Bioengineered corneal tissues are gaining momentum as a new source for corneal wound healing and scar management. Extracellular matrix (ECM)-scaffold-based engineering offers a new perspective on corneal regenerative medicine. Ultrathin stromal laminar tissues obtained from lenticule-based refractive correction procedures, such as SMall Incision Lenticule Extraction (SMILE), are an accessible and novel source of collagen-rich ECM scaffolds with high mechanical strength, biocompatibility, and transparency. After customization (including decellularization), these lenticules can serve as an acellular scaffold niche to repopulate cells, including stromal keratocytes and stem cells, with functional phenotypes. The intrastromal transplantation of these cell/tissue composites can regenerate native-like corneal stromal tissue and restore corneal transparency. This review highlights the current status of ECM-scaffold-based engineering with cells, along with the development of drug and growth factor delivery systems, and elucidates the potential uses of stromal lenticule scaffolds in regenerative therapeutics.

Fat Graft with Allograft Adipose Matrix and Magnesium Hydroxide-Incorporated PLGA Microspheres for Effective Soft Tissue Reconstruction

BACKGROUND

Autologous fat grafting is one of the most common procedures used in plastic surgery to correct soft tissue deficiency or depression deformity. However, its clinical outcomes are often suboptimal, and lack of metabolic and architectural support at recipient sites affect fat survival leading to complications such as cyst formation, calcification. Extracellular matrix-based scaffolds, such as allograft adipose matrix (AAM) and poly(lactic-co-glycolic) acid (PLGA), have shown exceptional clinical promise as regenerative scaffolds. Magnesium hydroxide (MH), an alkaline ceramic, has attracted attention as a potential additive to improve biocompatibility. We attempted to combine fat graft with regenerative scaffolds and analyzed the changes and viability of injected fat graft in relation to the effects of injectable natural, and synthetic (PLGA/MH microsphere) biomaterials.

METHODS

In vitro cell cytotoxicity, angiogenesis of the scaffolds, and wound healing were evaluated using human dermal fibroblast cells. Subcutaneous soft-tissue integration of harvested fat tissue was investigated in vivo in nude mouse with random fat transfer protocol Fat integrity and angiogenesis were identified by qRT-PCR and immunohistochemistry.

RESULTS

In vitro cell cytotoxicity was not observed both in AAM and PLGA/MH with human dermal fibroblast. PLGA/MH and AAM showed excellent wound healing effect. In vivo, the AAM and PLGA/MH retained volume compared to that in the only fat group. And the PLGA/MH showed the highest angiogenesis and anti-inflammation.

CONCLUSION

In this study, a comparison of the volume retention effect and angiogenic ability between autologous fat grafting, injectable natural, and synthetic biomaterials will provide a reasonable basis for fat grafting.

Male-specific long non-coding RNA testis-specific transcript, Y-linked 15 promotes gastric cancer cell growth by regulating Wnt family member 1/β-catenin signaling by sponging microRNA let-7a-5p

The present study is aimed to investigate the regulatory effects and related mechanism of long non-coding RNA testis-specific transcript, Y-linked 15 (TTTY15) in gastric carcinoma (GC) cell proliferation, migration, invasion, apoptosis and epithelial–mesenchymal transition (EMT). TTTY15 expression in GC tissue samples and cells was detected by quantitative real-time PCR (qRT-PCR), and the correlation between TTTY15 expression and GC clinicopathological indicators was analyzed. Cell counting kit-8 (CCK-8), BrdU, flow cytometry and Transwell assays were performed for detecting GC cell proliferation, migration, invasion and apoptosis. Western blot was performed for detecting the expressions of EMT-associated proteins (N-cadherin and E-cadherin), Wnt family member 1 (Wnt1) protein and β-catenin protein. Bioinformatics analysis was conducted to predict, and RNA immunoprecipitation (RIP) assay and dual-luciferase reporter gene assay were performed to verify the targeted relationships of microRNA let-7a-5p (let-7a-5p) with TTTY15 and Wnt1 mRNA 3'UTR. It was found that TTTY15 expression was significantly up-regulated in GC tissues and cells, and was associated with advanced TNM stage and poor tumor differentiation. TTTY15 overexpression promoted GC cell proliferation, migration and invasion, the expressions of N-cadherin, Wnt1 and β-catenin protein, and inhibited the apoptosis and E-cadherin expression, while knocking down TTTY15 had the opposite effects. TTTY15 directly targeted let-7a-5p and negatively regulated its expression. Wnt1 was the target gene of let-7a-5p, and TTTY15 could indirectly and positively regulate Wnt1 expression. In conclusion, TTTY15 promotes GC progression, by regulating the let-7a-5p/Wnt1 axis to activate the Wnt/β-catenin pathway.

Honeycomb-Like Hydrogel Microspheres for 3D Bulk Construction of Tumor Models

A two-dimensional (2D) cell culture-based model is widely applied to study tumorigenic mechanisms and drug screening. However, it cannot authentically simulate the three-dimensional (3D) microenvironment of solid tumors and provide reliable and predictable data in response to in vivo, thus leading to the research illusions and failure of drug screening. In this study, honeycomb-like gelatin methacryloyl (GelMA) hydrogel microspheres are developed by synchronous photocrosslinking microfluidic technique to construct a 3D model of osteosarcoma. The in vitro study shows that osteosarcoma cells (K7M2) cultured in 3D GelMA microspheres have stronger tumorous stemness, proliferation and migration abilities, more osteoclastogenetic ability, and resistance to chemotherapeutic drugs (DOX) than that of cells in 2D cultures. More importantly, the 3D-cultured K7M2 cells show more tumorigenicity in immunologically sound mice, characterized by shorter tumorigenesis time, larger tumor volume, severe bone destruction, and higher mortality. In conclusion, honeycomb-like porous microsphere scaffolds are constructed with uniform structure by microfluidic technology to massively produce tumor cells with original phenotypes. Those microspheres could recapitulate the physiology microenvironment of tumors, maintain cell-cell and cell-extracellular matrix interactions, and thus provide an effective and convenient strategy for tumor pathogenesis and drug screening research.

Electrospinning Fabrication Methods to Incorporate Laminin in Polycaprolactone for Kidney Tissue Engineering

BACKGROUND

Today's treatment options for renal diseases fall behind the need, as the number of patients has increased considerably over the last few decades. Tissue engineering (TE) is one avenue which may provide a new approach for renal disease treatment. This involves creating a niche where seeded cells can function in an intended way. One approach to TE is combining natural extracellular matrix proteins with synthetic polymers, which has been shown to have many positives, yet a little is understood in kidney. Herein, we investigate the incorporation of laminin into polycaprolactone electrospun scaffolds.

METHOD

The scaffolds were enriched with laminin via either direct blending with polymer solution or in a form of emulsion with a surfactant. Renal epithelial cells (RC-124) were cultured on scaffolds up to 21 days.

RESULTS

Mechanical characterization demonstrated that the addition of the protein changed Young's modulus of polymeric fibres. Cell viability and DNA quantification tests revealed the capability of the scaffolds to maintain cell survival up to 3 weeks in culture. Gene expression analysis indicated healthy cells via three key markers.

CONCLUSION

Our results show the importance of hybrid scaffolds for kidney tissue engineering.

Bioactive PCL microspheres with enhanced biocompatibility and collagen production for functional hyaluronic acid dermal fillers

Polymeric microspheres containing magnesium hydroxide (MH) and a bioactive agent (BA), such as apocynin (APO) and astaxanthin (ATX), have been prepared as functional dermal fillers with enhanced physicochemical and biological performance.

Advanced PLGA hybrid scaffold with a bioactive PDRN/BMP2 nanocomplex for angiogenesis and bone regeneration using human fetal MSCs

Biodegradable polymers have been used with various systems for tissue engineering. Among them, poly(lactic-co-glycolic) acid (PLGA) has been widely used as a biomaterial for bone regeneration because of its great biocompatibility and biodegradability properties. However, there remain substantial cruxes that the by-products of PLGA result in an acidic environment at the implanting site, and the polymer has a weak mechanical property. In our previous study, magnesium hydroxide (MH) and bone extracellular matrix are combined with a PLGA scaffold (PME) to improve anti-inflammation and mechanical properties and osteoconductivity. In the present study, the development of a bioactive nanocomplex (NC) formed along with polydeoxyribonucleotide and bone morphogenetic protein 2 (BMP2) provides synergistic abilities in angiogenesis and bone regeneration. This PME hybrid scaffold immobilized with NC (PME/NC) achieves outstanding performance in anti-inflammation, angiogenesis, and osteogenesis. Such an advanced PME/NC scaffold suggests an integrated bone graft substitute for bone regeneration.

Sequestered cell-secreted extracellular matrix proteins improve murine folliculogenesis and oocyte maturation for fertility preservation

Synthetic matrices offer a high degree of control and tunability for mimicking extracellular matrix functions of native tissue, allowing the study of disease and development in vitro. In this study, we functionalized degradable poly(ethylene glycol) hydrogels with extracellular matrix (ECM)-sequestering peptides aiming to recapitulate the native ECM composition for culture and maturation of ovarian follicular organoids. We hypothesized that ECM-sequestering peptides would facilitate deposition and retention of cell-secreted ECM molecules, thereby recreating cell-matrix interactions in otherwise bioinert PEG hydrogels. Specifically, heparin-binding peptide from antithrombin III (HBP), heparan sulfate binding peptide derived from laminin (AG73), basement membrane binder peptide (BMB), and heparan sulfate binding region of placental growth factor 2 (RRR) tethered to a PEG hydrogel significantly improved follicle survival, growth and maturation compared to PEG-Cys, a mechanically similar but biologically inert control. Immunohistochemical analysis of the hydrogel surrounding cultured follicles confirmed sequestration and retention of laminin, collagen I, perlecan, and fibronectin in ECM-sequestering hydrogels but not in bioinert PEG-Cys hydrogels. The media from follicles cultured in PEG-AG73, PEG-BMB, and PEG-RRR also had significantly higher concentrations of factors known to regulate follicle development compared to PEG-Cys. PEG-AG73 and PEG-BMB were the most beneficial for promoting follicle maturation, likely because AG73 and BMB mimic basement membrane interactions which are crucial for follicle development. Here we have shown that functionalizing PEG with ECM-sequestering peptides allows cell-secreted ECM to be retained within the hydrogels, restoring critical cell-matrix interactions and promoting healthy organoid development in a fully synthetic culture system. STATEMENT OF SIGNIFICANCE: Here we present a novel approach for sequestering and retaining cell-secreted extracellular matrix in a fully synthetic material for organoid culture. We have engineered a biomimetic poly(ethylene glycol) hydrogel functionalized with extracellular matrix-binding peptides to recapitulate the ovarian microenvironment. Incorporation of these peptides allows ovarian follicles to recreate their native matrix with the sequestered ECM that subsequently binds growth factors, facilitating follicle maturation. The novel design resulted in improved outcomes of folliculogenesis, potentially developing a fertility preservation option for young women undergoing sterilizing treatments for cancer. The fully synthetic and modular nature of this biomimetic material holds promise for other tissue engineering applications as it allows encapsulated cells to rebuild their native microenvironments in vitro.

Prevention of chemotherapy-induced premature ovarian insufficiency in mice by scaffold-based local delivery of human embryonic stem cell-derived mesenchymal progenitor cells

BACKGROUND

Premature ovarian insufficiency (POI) is one of the most serious side effects of chemotherapy in young cancer survivors. It may not only reduce fecundity but also affect lifelong health. There is no standard therapy for preserving ovarian health after chemotherapy. Recently, administration of embryonic stem cell-derived mesenchymal progenitor cells (ESC-MPCs) has been considered a new therapeutic option for preventing POI. However, the previous method of directly injecting cells into the veins of patients exhibits low efficacy and safety. This study aimed to develop safe and effective local delivery methods for the prevention of POI using two types of bioinspired scaffolds.

METHODS

Female mice received intraperitoneal cisplatin for 10 days. On day 11, human ESC-MPCs were delivered through systemic administration using intravenous injection or local administration using intradermal injection and intradermal transplantation with a PLGA/MH sponge or hyaluronic acid (HA) gel (GEL) type of scaffold. PBS was injected intravenously as a negative control. Ovarian function and fertility were evaluated 4 weeks after transplantation. Follicle development was observed using hematoxylin and eosin staining. The plasma levels of sex hormones were measured using ELISA. Expression levels of anti-Müllerian hormone (AMH) and ki-67 were detected using immunostaining, and the quality of oocytes and embryos was evaluated after in vitro fertilization. The estrous cycles were observed at 2 months after transplantation.

RESULTS

The local administration of human ESC-MPCs using the bioinspired scaffold to the backs of mice effectively prolonged the cell survival rate in vivo. The HA GEL group exhibited the best recovered ovarian functions, including a significantly increased number of ovarian reserves, estrogen levels, and AMH levels and decreased apoptotic levels. Furthermore, the HA GEL group showed improved quality of oocytes and embryos and estrous cycle regularity.

CONCLUSIONS

HA GEL scaffolds can be used as new delivery platforms for ESC-MPC therapy, and this method may provide a novel option for the clinical treatment of chemotherapy-induced POI.

Promotion of Bone Regeneration Using Bioinspired PLGA/MH/ECM Scaffold Combined with Bioactive PDRN

Current approaches of biomaterials for the repair of critical-sized bone defects still require immense effort to overcome numerous obstacles. The biodegradable polymer-based scaffolds have been required to expand further function for bone tissue engineering. Poly(lactic-co-glycolic) acid (PLGA) is one of the most common biopolymers owing to its biodegradability for tissue regenerations. However, there are major clinical challenges that the byproducts of the PLGA cause an acidic environment of implanting site. The critical processes in bone repair are osteogenesis, angiogenesis, and inhibition of excessive osteoclastogenesis. In this study, the porous PLGA (P) scaffold was combined with magnesium hydroxide (MH, M) and bone-extracellular matrix (bECM, E) to improve anti-inflammatory ability and osteoconductivity. Additionally, the bioactive polydeoxyribonucleotide (PDRN, P) was additionally incorporated in the existing PME scaffold. The prepared PMEP scaffold has pro-osteogenic and pro-angiogenic effects and inhibition of osteoclast due to the PDRN, which interacts with the adenosine A_2A receptor agonist that up-regulates expression of vascular endothelial growth factor (VEGF) and down-regulates inflammatory cytokines. The PMEP scaffold has superior biological properties for human bone-marrow mesenchymal stem cells (hBMSCs) adhesion, proliferation, and osteogenic differentiation in vitro. Moreover, the gene expressions related to osteogenesis and angiogenesis of hBMSCs increased and the inflammatory factors decreased on the PMEP scaffold. In conclusion, it provides a promising strategy and clinical potential candidate for bone tissue regeneration and repairing bone defects.

Renal Regeneration: The Role of Extracellular Matrix and Current ECM-Based Tissue Engineered Strategies

Natural extracellular matrices (ECM) are currently being studied as an alternative source for organ transplantation or as new solutions to treat kidney injuries, which can evolve to end-stage renal disease, a life devastating condition. This paper provides an overview on the current knowledge in kidney ECM and its usefulness on future investigations. The composition and structure of kidney ECM is herein associated with its intrinsic capacity of remodeling and repair after insult. Moreover, it provides a deeper insight on altered ECM components during disease. The use of decellularized kidney matrices is discussed in the second part of the review, with emphasis on how these matrices contribute to tissue-specific differentiation of embryonic, pluripotent, and other stem cells. The evolution on the field toward different uses of xenogeneic ECM as a biological scaffold material is discussed, namely the major outcomes on whole kidney recellularization and its in vivo implantation. At last, the recent literature on the use of processed kidney decellularized ECM to produce diverse biomaterial substrates, such as hydrogels, membranes, and bioinks are reviewed, with emphasis on future perspectives of its translation into the clinic.

Fluorescent Magnesium Hydroxide Nanosheet Bandages with Tailored Properties for Biocompatible Antimicrobial Wound Dressings and pH Monitoring

Magnesium hydroxide (Mg(OH)₂) is hailed as a cheap and biocompatible material with antimicrobial potential; however, research aimed at instilling additional properties and functionality to this material is scarce. In this work, we synthesized novel, fluorescent magnesium hydroxide nanosheets (Mg(OH)₂-NS) with a morphology that closely resembles that of graphene oxide. These multifunctional nanosheets were employed as a potent antimicrobial agent against several medically relevant bacterial and fungal species, particularly on solid surfaces. Their strong fluorescence signature correlates to their hydroxide makeup and can therefore be used to assess their degradation and functional antimicrobial capacity. Furthermore, their pH-responsive change in fluorescence can potentially act as a pH probe for wound acidification, which is characteristic of healthy wound healing. These fluorescent antimicrobial nanosheets were stably integrated into biocompatible electrospun fibers and agarose gels to add functionality to the material. This reinforces the suitability of the material to be used as antimicrobial bandages and gels. The biocompatibility of the Mg(OH)₂-NS for topical medical applications was supported by its noncytotoxic action on human keratinocyte (HaCaT) cells.

Insight into levofloxacin loaded biocompatible electrospun scaffolds for their potential as conjunctival substitutes

The rehabilitation of visual acuity with severe conjunctival fibrosis depends on ocular reconstruction with suitable conjunctival substitutes. In this study, we have developed poly(lactic acid) (PLA) electrospun nanofibrous membranes (EFMs) surface coated by cellulose nanofibrils (CNF) and/or silk peptide (SP). The CNF coating improved the hydrophilicity and the SP coating proliferated conjunctival epithelial cells (CjECs). To prevent post-operative infections, the composite scaffolds were loaded with levofloxacin (LF), constantly exerting efficient bactericidal effects. In in vivo evaluations, the PLA EFMs presented excellent therapeutic effects by promoting structural and functional restoration of conjunctiva after transplant. Even with reduced topical administration of antibiotics, the coloboma treated with LF loaded scaffolds presented no infections. It could be deduced that the potent bacterial inhibition feature could save troubles for patients by minimizing the application of antibiotics post-surgery. Hence, the developed PLA EFMs loaded with LF could be promising conjunctival substitutes.

Enhancing Kidney Vasculature in Tissue Engineering-Current Trends and Approaches: A Review

Chronic kidney diseases are a leading cause of fatalities around the world. As the most sought-after organ for transplantation, the kidney is of immense importance in the field of tissue engineering. The primary obstacle to the development of clinically relevant tissue engineered kidneys is precise vascularization due to the organ's large size and complexity. Current attempts at whole-kidney tissue engineering include the repopulation of decellularized kidney extracellular matrices or vascular corrosion casts, but these approaches do not eliminate the need for a donor organ. Stem cell-based approaches, such as kidney organoids vascularized in microphysiological systems, aim to construct a kidney without the need for organ donation. These organ-on-a-chip models show complex, functioning kidney structures, albeit at a small scale. Novel methodologies for developing engineered scaffolds will allow for improved differentiation of kidney stem cells and organoids into larger kidney grafts with clinical applications. While currently, kidney tissue engineering remains mostly limited to individual renal structures or small organoids, further developments in vascularization techniques, with technologies such as organoids in microfluidic systems, could potentially open doors for a large-scale growth of whole engineered kidneys for transplantation.

Particulate kidney extracellular matrix: bioactivity and proteomic analysis of a novel scaffold from porcine origin

Decellularized matrices are attractive substrates, being able to retain growth factors and proteins present in the native tissue. Several biomaterials can be produced by processing these matrices. However, new substrates capable of being injected that reverse local kidney injuries are currently scarce. Herein, we hypothesized that the decellularized particulate kidney porcine ECM (pKECM) could support renal progenitor cell cultures for posterior implantation. Briefly, kidneys are cut into pieces, decellularized by immersion on detergent solutions, lyophilized and reduced into particles. Then, ECM particles are analyzed for nuclear material remaining by DNA quantification and histological examination, molecular conformation by FITR and structural morphology by SEM. Protein extraction is also optimized for posterior identification and quantification by mass spectrometry. The results obtained confirm the collagenous structure and composition of the ECM, the effective removal of nucleic material and the preservation of ECM proteins with great similarity to human kidneys. Human renal progenitor cells (hRPCs) are seeded in different ratios with pKECM, on 3D suspensions. The conducted assays for cell viability, proliferation and distribution over 7 days of culture suggest that these matrices as biocompatible and bioactive substrates for hRPCs. Also, by analyzing CD133 expression, an optimal ratio for specific phenotypic expression is revealed, demonstrating the potential of these substrates to modulate cellular behavior. The initial hypothesis of developing and characterizing a particulate ECM biomaterial as a consistent substrate for 3D cultures is successfully validated. The findings in this manuscript suggest these particles as valuable tools for regenerative nephrology by minimizing surgeries and locally reversing small injuries which can lead to chronic renal disfunction.

The antagonistic effect of magnesium hydroxide particles on vascular endothelial activation induced by acidic PLGA degradation products

Although drug-eluting stents (DESs) are mainly coated with biodegradable polymers such as PLGA and PLLA, their acidic degradation products can alter the local microenvironment and affect the homeostasis of adjacent tissue. Previously, we developed anti-inflammatory PLGA-based materials including magnesium hydroxide (MH) to relieve the side effects caused by PLGA degradation. However, the underlying molecular mechanism of its protective effects has not yet been clarified. Here, we demonstrated the pathological mechanism of vascular endothelial activation caused by PLGA by-products. The PLGA by-products accumulated in HCAECs through MCT1, followed by oxidative stress and the activation of the MAPK/NF-κB signaling pathway. Finally, the PLGA by-products increased the expression of VCAM-1 as well as the secretion of proinflammatory cytokines. However, the addition of MH particles significantly diminished the activation of this molecular pathway and the expression of inflammation-related factors induced by acidic PLGA degradation products. Furthermore, Mg2+ released from MH particles restored endothelial function in both intracellular and extracellular spaces. Taken together, MH particles prevent the accumulation of PLGA degradation products in HCAECs, thereby repressing the associated vascular endothelial activation. These findings on the biochemical mechanisms are expected to provide important clues for addressing the safety issues in nearly all biodegradable polymer-based implants.

Integrated Bioactive Scaffold with Polydeoxyribonucleotide and Stem-Cell-Derived Extracellular Vesicles for Kidney Regeneration

Kidney tissue engineering and regeneration approaches offer great potential for chronic kidney disease treatment, but kidney tissue complexity imposes an additional challenge in applying regenerative medicine for renal tissue regeneration. In this study, a porous pneumatic microextrusion (PME) composite scaffold consisting of poly(lactic-co-glycolic acid) (PLGA, P), magnesium hydroxide (MH, M), and decellularized porcine kidney extracellular matrix (kECM, E) is functionalized with bioactive compounds, polydeoxyribonucleotide (PDRN), and tumour necrosis factor-α (TNF-α)/interferon-γ (IFN-γ)-primed mesenchymal stem-cell-derived extracellular vesicles (TI-EVs) to improve the regeneration and maintenance of a functional kidney tissue. The combination of PDRN and TI-EVs showed a significant synergistic effect in regenerative processes including cellular proliferation, angiogenesis, fibrosis, and inflammation. In addition, the PME/PDRN/TI-EV scaffold induced an effective glomerular regeneration and restoration of kidney function compared to the existing PME scaffold in a partial nephrectomy mouse model. Therefore, such an integrated bioactive scaffold that combines biochemical cues from PDRN and TI-EVs and biophysical cues from a porous PLGA scaffold containing MH and kECM can be used as an advanced tissue engineering platform for kidney tissue regeneration.

PLGA Microspheres Containing Hydrophobically Modified Magnesium Hydroxide Particles for Acid Neutralization-Mediated Anti-Inflammation

BACKGROUND

Poly(lactic-co-glycolic acid) (PLGA) microspheres have been actively used in various pharmaceutical formulations because they can sustain active pharmaceutical ingredient release and are easy to administer into the body using a syringe. However, the acidic byproducts produced by the decomposition of PLGA cause inflammatory reactions in surrounding tissues, limiting biocompatibility. Magnesium hydroxide (MH), an alkaline ceramic, has attracted attention as a potential additive because it has an acid-neutralizing effect.

METHODS

To improve the encapsulation efficiency of hydrophilic MH, the MH particles were capped with hydrophobic ricinoleic acid (RA-MH). PLGA microspheres encapsulated with RA-MH particles were manufactured by the O/W method. To assess the in vitro cytotoxicity of the degradation products of PLGA, MH/PLGA, and RA-MH/PLGA microspheres, CCK-8 and Live/Dead assays were performed with NIH-3T3 cells treated with different concentrations of their degradation products. In vitro anti-inflammatory effect of RA-MH/PLGA microspheres was evaluated with quantitative measurement of pro-inflammatory cytokines.

RESULTS

The synthesized RA-MH was encapsulated in PLGA microspheres and displayed more than four times higher loading content than pristine MH. The PLGA microspheres encapsulated with RA-MH had an acid-neutralizing effect better than that of the control group. In an in vitro cell experiment, the degradation products obtained from RA-MH/PLGA microspheres exhibited higher biocompatibility than the degradation products obtained from PLGA microspheres. Additionally, the RA-MH/PLGA microsphere group showed an excellent anti-inflammatory effect.

CONCLUSION

Our results proved that RA-MH-encapsulated PLGA microspheres showed excellent biocompatibility with an anti-inflammatory effect. This technology can be applied to drug delivery and tissue engineering to treat various incurable diseases in the future.

Modulation of Local Overactive Inflammation via Injectable Hydrogel Microspheres

Although injectable hydrogel microsphere has demonstrated tremendous promise in clinical applications, local overactive inflammation in degenerative diseases could jeopardize biomaterial implantation's therapeutic efficacy. Herein, an injectable "peptide-cell-hydrogel" microsphere was constructed by covalently coupling of APETx2 and further loading of nucleus pulposus cells, which could inhibit local inflammatory cytokine storms to regulate the metabolic balance of ECM in vitro. The covalent coupling of APETx2 preserved the biocompatibility of the microspheres and achieved a controlled release of APETx2 for more than 28 days in an acidic environment. By delivering "peptide-cell-hydrogel" microspheres to a rat degenerative intervertebral disc at 4 weeks, the expression of ASIC-3 and IL-1β was significantly decreased for 3.53-fold and 7.29-fold, respectively. Also, the content of ECM was significantly recovered at 8 weeks. In summary, the proposed strategy provides an effective approach for tissue regeneration under overactive inflammatory responses.

SARS-CoV-2 and tissue damage: current insights and biomaterial-based therapeutic strategies

The effect of SARS-CoV-2 infection on humanity has gained worldwide attention and importance due to the rapid transmission, lack of treatment options and high mortality rate of the virus. While scientists across the world are searching for vaccines/drugs that can control the spread of the virus and/or reduce the risks associated with infection, patients infected with SARS-CoV-2 have been reported to have tissue/organ damage. With most tissues/organs having limited regenerative potential, interventions that prevent further damage or facilitate healing would be helpful. In the past few decades, biomaterials have gained prominence in the field of tissue engineering, in view of their major role in the regenerative process. Here we describe the effect of SARS-CoV-2 on multiple tissues/organs, and provide evidence for the positive role of biomaterials in aiding tissue repair. These findings are further extrapolated to explore their prospects as a therapeutic platform to address the tissue/organ damage that is frequently observed during this viral outbreak. This study suggests that the biomaterial-based approach could be an effective strategy for regenerating tissues/organs damaged by SARS-CoV-2.

Biocompatible and functional inorganic magnesium ceramic particles for biomedical applications

Magnesium ceramics hold promise for numerous biological applications. This review covers the synthesis of magnesium ceramic particles with specific morphologies and potential modification techniques. Magnesium ceramic particles possess multiple characteristics directly applicable to human biology; they are anti-inflammatory, antibacterial, antiviral, and offer anti-cancer effects. Based on these advantages, magnesium hydroxide nanoparticles have been extensively utilized across biomedical fields. In a vascular stent, the incorporation of magnesium ceramic nanoparticles enhances re-endothelialization. Additionally, tissue regeneration for bone, cartilage, and kidney can be promoted by magnesium ceramics. This review enables researchers to identify the optimum synthetic conditions to prepare magnesium ceramics with specific morphologies and sizes and select the appropriate modification protocols. It is also intended to elucidate the desirable physicochemical properties and biological benefits of magnesium ceramics.

Implementation of Pericytes in Vascular Regeneration Strategies

For the survival and integration of complex large-sized tissue-engineered (TE) organ constructs that exceed the maximal nutrients and oxygen diffusion distance required for cell survival, graft (pre)vascularization to ensure medium or blood supply is crucial. To achieve this, the morphology and functionality of the microcapillary bed should be mimicked by incorporating vascular cell populations, including endothelium and mural cells. Pericytes play a crucial role in microvascular function, blood vessel stability, angiogenesis, and blood pressure regulation. In addition, tissue-specific pericytes are important in maintaining specific functions in different organs, including vitamin A storage in the liver, renin production in the kidneys and maintenance of the blood-brain-barrier. Together with their multipotential differentiation capacity, this makes pericytes the preferred cell type for application in TE grafts. The use of a tissue-specific pericyte cell population that matches the TE organ may benefit organ function. In this review, we provide an overview of the literature for graft (pre)-vascularization strategies and highlight the possible advantages of using tissue-specific pericytes for specific TE organ grafts. Impact statement The use of a tissue-specific pericyte cell population that matches the tissue-engineered (TE) organ may benefit organ function. In this review, we provide an overview of the literature for graft (pre)vascularization strategies and highlight the possible advantages of using tissue-specific pericytes for specific TE organ grafts.

Environmental toxicology wars: Organ-on-a-chip for assessing the toxicity of environmental pollutants

Environmental pollution is a widespread problem, which has seriously threatened human health and led to an increase of human diseases. Therefore, it is critical to evaluate environmental pollutants quickly and efficiently. Because of obvious inter-species differences between animals and humans, and lack of physiologically-relevant microenvironment, animal models and in vitro two-dimensional (2D) models can not accurately describe toxicological effects and predicting actual in vivo responses. To make up the limitations of conventional environmental toxicology screening, organ-on-a-chip (OOC) systems are increasingly developing. OOC systems can provide a well-organized architecture with comparable to the complex microenvironment in vivo and generate realistic responses to environmental pollutants. The feasibility, adjustability and reliability of OCC systems make it possible to offer new opportunities for environmental pollutants screening, which can study their metabolism, collective response, and fate in vivo. Further progress can address the challenges to make OCC systems better investigate and evaluate environmental pollutants with high predictive power.

Recent Advances in Antiinflammatory Material Design

Implants and prostheses are widely used to replace damaged tissues or to treat various diseases. However, besides the risk of bacterial or fungal infection, an inflammatory response usually occurs. Here, recent progress in the field of anti-inflammatory biomaterials is described. Different materials and approaches are used to decrease the inflammatory response, including hydrogels, nanoparticles, implant surface coating by polymers, and a variety of systems for anti-inflammatory drug delivery. Complex multifunctional systems dealing with inflammation, microbial infection, bone regeneration, or angiogenesis are also described. New promising stimuli-responsive systems, such as pH- and temperature-responsive materials, are also being developed that would enable an "intelligent" antiinflammatory response when the inflammation occurs. Together, different approaches hold promise for creation of novel multifunctional smart materials allowing better implant integration and tissue regeneration.