Design Challenges in Polymeric Scaffolds for Tissue Engineering

Enhancing the biological characteristics of aminolysis surface-modified 3D printed nanocomposite polycaprolactone/nanohydroxyapatite scaffold via gelatin biomacromolecule immobilization: An in vitro and in vivo study

The surface characteristics of scaffolds utilized in bone tissue engineering profoundly influence subsequent cellular response. This study investigated the efficacy of applying a gelatin coat to the surface of aminolysis surface-modified scaffolds fabricated through 3D printing with a polycaprolactone/hydroxyapatite nanocomposite, employing the hot-melt extrusion FDM technique. Initially, aminolysis surface modification using hexamethylenediamine enhanced surface hydrophilicity by introducing amine functional groups. Subsequently, gelatin solutions were applied to the scaffolds, and crosslinking with EDC/NHS was performed to increase coating strength. Contact angle measurements revealed a significantly increased surface hydrophilicity post-aminolysis. Aminolysis facilitated uniform gelatin coating formation and distribution. Subsequently, crosslinking enhanced coating durability. The addition of gelatin coating resulted in a notable 20 % increase in scaffold mechanical strength and more than 50 % rise in Young's modulus and exhibited enhancement of biodegradability and bioactivity. Gelatin coated scaffolds also demonstrated improved cell viability and adhesion and over two times higher expression of OPN and ALP genes, suggesting improved biological properties. In addition, in vivo bone formation studies verified the biological enhancement of scaffolds. Utilizing an immobilized crosslinked gelatin biomacromolecule coating effectively enhanced the biological characteristics of 3D printed scaffolds and their potential applications as bone tissue engineering scaffolds.

Biodegradable Poly(d,l-lactide-co-ε-caprolactone) Electrospun Scaffolds Outperform Antifibrotic-Loaded Meshes in an in Vivo Tissue Regeneration Model

Wound healing is a complex and dynamic process of replacing missing cellular structures and tissue layers. Clinical practice includes the application of a sterile bandage to promote healing and to restrain infection, like the commercial nonbiodegradable meshes. However, while inert, nontoxic, and nonimmunogenic, they can cause calcification, fibrosis, and inflammation, potentially hindering the healing process in the long term. To address this challenge and enhance wound healing, we developed a totally biodegradable electrospun poly(d,l-lactide-co-ε-caprolactone) (PDLLCL) drug delivery system that incorporates two already FDA-approved antifibrotics, pirfenidone (PIRF) and triamcinolone acetonide (TA). The PDLLCL meshes, fabricated via electrospinning, exhibited homogeneity and complete degradation after 120 days, consistent with the wound healing process. In vitro, functional analysis on RAW 264.7 macrophages revealed no cytotoxicity and an immunomodulatory effect of PIRF and TA compared with the positive control (lipopolysaccharides, LPS) and the PDLLCL meshes alone. Lastly, subcutaneous in vivo assessment on a rabbit model, following the ISO 10993-6 standard, showed that our tailored made PDLLCL meshes were able to lower both irritation and fibrosis indexes from 2 weeks to 4 weeks of implantation, highlighting the beneficial effect of biodegradable polymers. However, we saw no significant positive effect on the incorporation of antifibrotics in vivo for irritation and fibrosis indexes. This underscores the potential of PDLLCL meshes as a possible alternative for wound healing, reducing the use of intermittent antifibrotic agents during the healing process.

Decellularized Porcine Aorta as a Scaffold for Human Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells in Tissue Engineering

Tissue engineering has been an integral part of regenerative medicine. Functional biomimetic structures were assembled by combining appropriate scaffolds with specific cells. The decellularization of animal tissue preserved the natural biochemical components and structural properties of the extracellular matrix (ECM) of specific organs, thereby providing a suitable niche for tissue-specific cell differentiation and growth. In this study, the extracellular matrix (ECM) of the porcine aorta was obtained through trypsin-based decellularization. The resulting porcine aortic ECM retained a favorable collagen composition, exhibited no cytotoxicity, and demonstrated chemophilic properties for mesenchymal stem cells. Human adipose-derived mesenchymal stem cells (hADSCs) and human induced pluripotent stem cell-derived mesenchymal stem cells (hiMSCs) were transplanted onto the decellularized porcine aortic ECM, where successful differentiation into a mature cartilage layer was observed. These findings suggested that the porcine aortic ECM could serve as a potential scaffold with tubular and linear structures for tissue engineering applications. Functional human iMSCs (induced-mesenchymal stem cells) were generated from human iPSCs (induced-pluripotent stem cells) and analyzed for differences compared to primary MSCs via RNA-seq. The hiMSCs were applied to decellularized porcine aortic ECM (extracellular matrix), demonstrating chondrogenic differentiation and confirming the usability of xenogeneic ECM.

Control and interplay of scaffold-biomolecule interactions applied to cartilage tissue engineering

Cartilage tissue engineering based on the combination of biomaterials, adult or stem cells and bioactive factors is a challenging approach for regenerative medicine with the aim of achieving the formation of a functional neotissue stable in the long term. Various 3D scaffolds have been developed to mimic the extracellular matrix environment and promote cartilage repair. In addition, bioactive factors have been extensively employed to induce and maintain the cartilage phenotype. However, the spatiotemporal control of bioactive factor release remains critical for maximizing the regenerative potential of multipotent cells, such as mesenchymal stromal cells (MSCs), and achieving efficient chondrogenesis and sustained tissue homeostasis, which are essential for the repair of hyaline cartilage. Despite advances, the effective delivery of bioactive factors is limited by challenges such as insufficient retention at the site of injury and the loss of therapeutic efficacy due to uncontrolled drug release. These limitations have prompted research on biomolecule-scaffold interactions to develop advanced delivery systems that provide sustained release and controlled bioavailability of biological factors, thereby improving therapeutic outcomes. This review focuses specifically on biomaterials (natural, hybrid and synthetic) and biomolecules (molecules, proteins, nucleic acids) of interest for cartilage engineering. Herein, we review in detail the approaches developed to maintain the biomolecules in scaffolds and control their release, based on their chemical nature and structure, through steric, non-covalent and/or covalent interactions, with a view to their application in cartilage repair.

Controlling Plasma-Functionalized Fillers for Enhanced Properties of PLA/ZnO Biocomposites: Effects of Excess l-Lactic Acid and Biomedical Implications

Plasma surface treatment of ceramic particles has emerged as a promising approach for developing biocomposites intended for use in tissue engineering applications. Introducing functional groups on particle surfaces promotes changes in material surface properties, enhancing adhesion, biocompatibility, and reactivity. It can also mitigate degradation during the processing of polymer matrices in composite materials. Therefore, carefully choosing the functionalizing agent responsible for generating the functional groups and selecting appropriate functionalization parameters are significant steps in the plasma surface treatment process. However, in a tissue engineering context, an excess of the functionalizing agent can be harmful, increasing cell toxicity and inhibiting the stimulation of cell growth, consequently delaying or even hindering tissue regeneration. This article examines how the functionalizing agent excess of l-lactic acid (LA) applied in the plasma surface treatment of the filler affects the thermal, rheological, biological, and wettability properties of poly(lactic acid) (PLA) and zinc oxide (ZnO) biocomposites. The investigation reveals that the surface treatment effectively mitigated the catalytic effects of ZnO on PLA degradation during melt processing, regardless of the excess functionalizing agent. There was minimal impact on the material's rheological, thermal, and wettability characteristics, but the LA residue significantly influenced cell proliferation and the biological response. These findings show the importance of removing excess functionalizing agents to obtain biocomposites suitable for tissue engineering applications.

Harnessing native blueprints for designing bioinks to bioprint functional cardiac tissue

Cardiac tissue lacks regenerative capacity, making heart transplantation the primary treatment for end-stage heart failure. Engineered cardiac tissues developed through three-dimensional bioprinting (3DBP) offer a promising alternative. However, reproducing the native structure, cellular diversity, and functionality of cardiac tissue requires advanced cardiac bioinks. Major obstacles in CTE (cardiac tissue engineering) include accurately characterizing bioink properties, replicating the cardiac microenvironment, and achieving precise spatial organization. Optimizing bioink properties to closely mimic the extracellular matrix (ECM) is essential, as deviations may result in pathological effects. This review encompasses the rheological and electromechanical properties of bioinks and the function of the cardiac microenvironment in the design of functional cardiac constructs. Furthermore, it focuses on improving the rheological characteristics, printability, and functionality of bioinks, offering valuable perspectives for developing new bioinks especially designed for CTE.

Biomaterial Properties and Differentiation Strategies for Tenogenic Differentiation of Mesenchymal Stem Cells

Tendinopathy is a prevalent musculoskeletal condition that affects both aging populations and individuals involved in repetitive, high-intensity activities, such as athletes. Current treatment options primarily address symptom management or involve surgery, which carries a significant risk of complications and re-injury. This highlights the need for regenerative medicine approaches that combine stem cells, biomaterials, and growth factors. However, achieving effective tenogenic differentiation remains challenging due to the absence of standardized differentiation protocols. Consequently, a review of existing research has been conducted to identify optimal biomaterial properties and growth factor protocols. Findings suggest that the ideal biomaterial for tenogenic differentiation should feature a 3D structure to preserve tenogenic expression, incorporate a combination of aligned micro- and nanofibers to promote differentiation, and require further investigation into optimal stiffness. Additionally, growth factor protocols should include an induction phase to initiate tenogenic lineage commitment, followed by a maintenance phase to support matrix production and maturation.

Mimicking bone remodeling scaffolds of polyvinylalcohol/silk fibroin with phytoactive compound of soy protein isolate as surgical supporting biomaterials for tissue formation at defect area in osteoporosis; characterization, morphology, andin-vitrotesting

Mimicking bone remodeling scaffolds were developed as supportive biomaterials to promote tissue formation at defect sites in osteoporosis. Scaffolds made of polyvinyl alcohol (PVA) were mixed with varying weight ratios of silk fibroin (SF) and a phytoactive compound-based soy protein isolate (SPI); PVA30SF, PVA20SF10SPI, PVA15SF15SPI, PVA10SF20SPI, PVA30SPI. PVA was used as control. These components were mixed into aqueous solution and crosslinking with EDC before freeze thawing and freeze drying, respectively. Then, the scaffolds were characterized at the molecular level using Fourier transform infrared spectroscopy and their morphology was observed using scanning electron microscopy. Physical properties including swelling and degradation were tested, as well as mechanical properties like stress-strain behavior and modulus. The biological performance of the scaffolds was evaluated through osteoblast cell culturing, assessing cell viability, proliferation, alkaline phosphatase (ALP) activity, calcium content, and calcium deposition. The results demonstrate that the scaffolds with both SF and SPI had greater molecular mobility of -OH, amide I, II, and III groups, compared to the scaffold with only SF or SPI. These scaffolds also displayed larger pore sizes. Scaffolds with both SF and SPI showed higher swelling and degradation rates than those with only SF or SPI. Additionally, they exhibited better cell viability and calcium deposition, along with increased cell proliferation, ALP activity, and calcium content. Notably, the scaffold with a higher amount of SPI, PVA10SF20SPI, exhibited the most suitable performance for enhancing cell response, thereby promoting bone formation. This scaffold is proposed as a supportive biomaterial to be incorporated with plates and screws for bone fixation at defect sites in osteoporosis.

Recent trends in the development ofin vitro3D kidney models

The kidneys are vital for maintaining bodily homeostasis and are susceptible to various diseases that disrupt their function. Traditionally, research on kidney diseases has relied on animal models and simplistic two-dimensional cell cultures, which do not fully replicate human tissue pathology. To address this, recent advances focus on developing advanced 3D biomimeticin vitromodels using human-derived cells. These models mimic healthy and diseased kidney tissues with specificity, replicating key elements like glomerular and tubular structures through tissue engineering. By closely mimicking human physiology, they provide a promising platform for studying renal disorders, drug-induced nephrotoxicity, and evaluating new therapies. However, the challenges include optimizing scalability, reproducibility, and long-term stability to enhance reliability in research and clinical applications. This review highlights the transformative potential of 3D biomimeticin vitrokidney models in advancing biomedical research and clinical applications. By focusing on human-specific cell cultures and tissue engineering techniques, these models aim to overcome the limitations of conventional animal models and simplistic 2D cell cultures. The review discusses in detail the various types of biomimetic kidney models currently under development, their specific applications, and the innovative approaches used to construct them. It also addresses the challenges and limitations associated with these models for their widespread adoption and reliability in research settings.

Clinical challenges in bone tissue engineering - A narrative review

Bone tissue engineering (BTE) has emerged as a promising approach to address large bone defects caused by trauma, infections, congenital malformations, and tumors. This review focuses on scaffold design, cell sources, growth factors, and vascularization strategies, highlighting their roles in developing effective treatments. We explore the complexities of balancing mechanical properties, porosity, and biocompatibility in scaffold materials, alongside optimizing mesenchymal stem cell delivery methods. The critical role of growth factors in bone regeneration and the need for controlled release systems are discussed. Vascularization remains a significant hurdle, with strategies such as angiogenic factors, co-culture systems, and bioprinting under investigation. Mechanical challenges, tissue responses, and inflammation management are examined, alongside gene therapy's potential for enhancing osteogenesis and angiogenesis via both viral and non-viral delivery methods. The review emphasizes the impact of patient-specific factors on bone healing outcomes and the importance of personalized approaches. Future directions are described, emphasizing the necessity of interdisciplinary cooperation to advance the field of BTE and convert laboratory results into clinically feasible solutions.

Vat-Based 3D-Bioprinted Scaffolds from Photocurable Bacterial Levan for Osteogenesis and Immunomodulation

Emerging techniques of additive manufacturing, such as vat-based three-dimensional (3D) bioprinting, offer novel routes to prepare personalized scaffolds of complex geometries. However, there is a need to develop bioinks suitable for clinical translation. This study explored the potential of bacterial-sourced methacrylate levan (LeMA) as a bioink for the digital light processing (DLP) 3D bioprinting of bone tissue scaffolds. LeMA was successfully synthesized, characterized, and used to fabricate 3D-bioprinted scaffolds with excellent printability and physicochemical properties. In vitro studies demonstrated superior cytocompatibility of 15% w/v LeMA gels compared to 20% gels. 15% LeMA gels supported osteogenic differentiation , as evidenced by alkaline phosphatase activity and mineral deposition by MC3T3 pre-osteoblasts. Importantly, the LeMA hydrogels positively modulated the macrophage phenotype, promoting the expression of the anti-inflammatory marker CD206. These findings suggest that 3D-printed LeMA scaffolds can create a favorable microenvironment for bone regeneration, highlighting their potential for tissue repair and regeneration applications.

Advances in biomaterials-based tissue engineering for regeneration of female reproductive tissues

The anatomical components of the female reproductive system-comprising the ovaries, uterus, cervix, vagina, and fallopian tubes-interact intricately to provide the structural and hormonal support essential for reproduction. However, this system is susceptible to various detrimental factors, both congenital and acquired, that can impair fertility and adversely affect quality of life. Recent advances in bioengineering have led to the development of sophisticated three-dimensional models that mimic the complex architecture and functionality of reproductive organs. These models, incorporating diverse cell types and tissue layers, are crucial for understanding physiological processes within the reproductive tract. They offer insights into decidualization, ovulation, folliculogenesis, and the progression of reproductive cancers, thereby enhancing personalized medical treatments and addressing female infertility. This review highlights the pivotal role of tissue engineering in diagnosing and treating female infertility, emphasizing the importance of considering factors like biocompatibility, biomaterial selection, and mechanical properties in the design of bioengineered systems. The challenge of replicating the functionally specialized and structurally complex organs, such as the uterus and ovary, underscores the need for reliable techniques that improve morphological and functional restoration. Despite substantial progress, the goal of creating a fully artificial female reproductive system is still a challenge. Nonetheless, the recent fabrication of artificial ovaries, uteruses, cervixes, and vaginas marks significant advancements toward this aim. Looking forward, the challenges in bioengineering are expected to spur further innovations in both basic and applied sciences, potentially hastening the clinical adoption of these technologies.

Sustainable biofabrication: from bioprinting to AI-driven predictive methods

Biofabrication is potentially an inherently sustainable manufacturing process of bio-hybrid systems based on biomaterials embedded with cell communities. These bio-hybrids promise to augment the sustainability of various human activities, ranging from tissue engineering and robotics to civil engineering and ecology. However, as routine biofabrication practices are laborious and energetically disadvantageous, our society must refine production and validation processes in biomanufacturing. This opinion highlights the research trends in sustainable material selection and biofabrication techniques. By modeling complex biosystems, the computational prediction will allow biofabrication to shift from an error-trial method to an efficient, target-optimized approach with minimized resource and energy consumption. We envision that implementing bionomic rationality in biofabrication will render bio-hybrid products fruitful for greening human activities.

A nanofibrous polycaprolactone/collagen neural guidance channel filled with sciatic allogeneic schwann cells and platelet-rich plasma for sciatic nerve repair

Sciatic nerve damage, a common condition affecting approximately 2.8% of the US population, can lead to significant disability due to impaired nerve signal transmission, resulting in loss of sensation and motor function in the lower extremities. In this study, a neural guidance channel was developed by rolling a nanofibrous scaffold produced via electrospinning. The scaffold's microstructure, biocompatibility, biodegradation rate, porosity, mechanical properties, and hemocompatibility were evaluated. Platelet-rich plasma (PRP) activated with 30,000 allogeneic Schwann cells (SCs) was injected into the lumen of the channels following implantation into a rat model of sciatic nerve injury. Recovery of motor function, sensory function, and muscle re-innervation was assessed using the sciatic function index (SFI), hot plate latency time, and gastrocnemius muscle wet weight loss. Results showed mean hot plate latency times of Autograft: 7.03, PCL/collagen scaffolds loaded with PRP and SCs (PCLCOLPRPSCs): 8.34, polymer-only scaffolds (PCLCOL): 10.66, and untreated animals (Negative Control): 12.00. The mean SFI values at week eight were Autograft: -49.30, PCLCOLPRPSCs: -64.29, PCLCOL: -75.62, and Negative Control: -77.14. The PCLCOLPRPSCs group showed a more negative SFI compared to the Autograft group but performed better than both the PCLCOL and Negative Control groups. These findings suggest that the developed strategy enhanced sensory and functional recovery compared to the negative control and polymer-only scaffold groups.

Multifunctional Biological Performance of Electrospun PCL Scaffolds Formulated with Silver Sulfide Nanoparticles

Our work describes the green synthesis of silver sulfide nanoparticles (Ag2S NPs) and their formulation into polycaprolactone fibers (PCL), aiming to improve the multifunctional biological performance of PCL membranes as scaffolds. For this purpose, an extract of rosemary (Salvia rosmarinus) was employed as a reducing agent for the Ag2S NPs, obtaining irregular NPs and clusters of 5-60 nm, with a characteristic SPR absorption at 369 nm. Ag2S was successfully incorporated into PCL fibers by electrospinning using heparin (HEP) as a stabilizer/biocompatibility agent, obtaining nanostructured fibers with a ca. 500-800 nm diameter. Different amounts of Ag2S NPs (0.05, 0.5, and 1 wt.%) enhanced the nanostructured membranes' surface polarity and mechanical performance, with a controlled ion release after 6 days submerged in PBS solution, determined by cyclic voltammetry. As a result, PCL/HEP/Ag2S scaffolds exhibit high antibacterial performance (80-90%) at early stages of contact (3 h) against E. coli and S. aureus. Also, cytotoxicity analysis demonstrated that the nanostructured membranes are biocompatible and exhibit high fibroblast cell regeneration, which is optimal for their application as scaffolds. To validate the regenerative response of PCL/HEP/Ag2S scaffolds, controlled wounds were induced in Wistar rats, presenting a favorable healing response by contact with PCL/HEP/Ag2S 1%, compared with the untreated wound. Our results indicated that nanostructured scaffolds enable the development of novel nanomaterials with multifunctional biological performance.

Enhancing alginate dialdehyde-gelatin (ADA-GEL) based hydrogels for biofabrication by addition of phytotherapeutics and mesoporous bioactive glass nanoparticles (MBGNs)

This study explores the 3D printing of alginate dialdehyde-gelatin (ADA-GEL) inks incorporating phytotherapeutic agents, such as ferulic acid (FA), and silicate mesoporous bioactive glass nanoparticles (MBGNs) at two different concentrations. 3D scaffolds with bioactive properties suitable for bone tissue engineering (TE) were obtained. The degradation and swelling behaviour of films and 3D printed scaffolds indicated an accelerated trend with increasing MBGN content, while FA appeared to stabilize the samples. Determination of the degree of crosslinking validated the increased stability of hydrogels due to the addition of FA and 0.1% (w/v) MBGNs. The incorporation of MBGNs not only improved the effective moduli and conferred bioactive properties through the formation of hydroxyapatite (HAp) on the surface of ADA-GEL-based samples but also enhanced VEGF-A expression of MC3T3-E1 cells. The beneficial impact of FA and low concentrations of MBGNs in ADA-GEL-based inks for 3D (bio)printing applications was corroborated through various printing experiments, resulting in higher printing resolution, as also confirmed by rheological measurements. Cytocompatibility investigations revealed enhanced MC3T3-E1 cell activity and viability. Furthermore, the presence of mineral phases, as confirmed by an in vitro biomineralization assay, and increased ALP activity after 21 days, attributed to the addition of FA and MBGNs, were demonstrated. Considering the acquired structural and biological properties, along with efficient drug delivery capability, enhanced biological activity, and improved 3D printability, the newly developed inks exhibit promising potential for biofabrication and bone TE.

Collagen binding and mimetic peptide-functionalized self-assembled peptide hydrogel enhance chondrogenic differentiation of human mesenchymal stem cells

The avascular structure and low cell migration to the damaged area due to the low number of cells do not allow spontaneous repair of the articular cartilage tissue. Therefore, functional scaffolds obtained from biomaterials are used for the regeneration of cartilage tissue. Here, we functionalized one of the self-assembling peptide (SAP) scaffolds KLD (KLDLKLDLKLDL) with short bioactive motifs, which are the α1 chain of type II collagen binding peptide WYRGRL (C1) and the triple helical collagen mimetic peptide GFOGER (C2) by direct coupling. Our goal was to develop injectable functional SAP hydrogels with proper mechanical characteristics that would improve chondrogenesis. Scanning electron microscopy (SEM) was used to observe the integration of peptide scaffold structure at the molecular level. To assure the stability of SAPs, the rheological characteristics and degradation profile of SAP hydrogels were assessed. The biochemical study of the DNA, glycosaminoglycan (GAG), and collagen content revealed that the developed bioactive SAP hydrogels greatly increased hMSCs proliferation compared with KLD scaffolds. Moreover, the addition of bioactive peptides to KLD dramatically increased the expression levels of important chondrogenic markers such as aggrecan, SOX-9, and collagen Type II as evaluated by real-time polymerase chain reaction (PCR). We showed that hMSC proliferation and chondrogenic differentiation were encouraged by the developed SAP scaffolds. Although the chondrogenic potentials of WYRGRL and GFOGER were previously investigated, no study compares the effect of the two peptides integrated into 3-D SAP hydrogels in chondrogenic differentiation. Our findings imply that these specifically created bioactive peptide scaffolds might help enhance cartilage tissue regeneration.

Exploiting the Potential of Decellularized Extracellular Matrix (ECM) in Tissue Engineering: A Review Study

While significant progress has been made in creating polymeric structures for tissue engineering, the therapeutic application of these scaffolds remains challenging owing to the intricate nature of replicating the conditions of native organs and tissues. The use of human-derived biomaterials for therapeutic purposes closely imitates the properties of natural tissue, thereby assisting in tissue regeneration. Decellularized extracellular matrix (dECM) scaffolds derived from natural tissues have become popular because of their unique biomimetic properties. These dECM scaffolds can enhance the body's ability to heal itself or be used to generate new tissues for restoration, expanding beyond traditional tissue transfers and transplants. Enhanced knowledge of how ECM scaffold materials affect the microenvironment at the injury site is expected to improve clinical outcomes. In this review, recent advancements in dECM scaffolds are explored and relevant perspectives are offered, highlighting the development and application of these scaffolds in tissue engineering for various organs, such as the skin, nerve, bone, heart, liver, lung, and kidney.

Preliminary study on the preparation of lyophilized acellular nerve scaffold complexes from rabbit sciatic nerves with human umbilical cord mesenchymal stem cells

BACKGROUND

The gold standard of care for patients with severe peripheral nerve injury is autologous nerve grafting; however, autologous nerve grafts are usually limited for patients because of the limited number of autologous nerve sources and the loss of neurosensory sensation in the donor area, whereas allogeneic or xenografts are even more limited by immune rejection. Tissue-engineered peripheral nerve scaffolds, with the morphology and structure of natural nerves and complex biological signals, hold the most promise as ideal peripheral nerve "replacements".

AIM

To prepare allogenic peripheral nerve scaffolds using a low-toxicity decellularization method, and use human umbilical cord mesenchymal stem cells (hUC-MSCs) as seed cells to cultivate scaffold-cell complexes for the repair of injured peripheral nerves.

METHODS

After obtaining sciatic nerves from New Zealand rabbits, an optimal acellular scaffold preparation scheme was established by mechanical separation, varying lyophilization cycles, and trypsin and DNase digestion at different times. The scaffolds were evaluated by hematoxylin and eosin (HE) and luxol fast blue (LFB) staining. The maximum load, durability, and elastic modulus of the acellular scaffolds were assessed using a universal material testing machine. The acellular scaffolds were implanted into the dorsal erector spinae muscle of SD rats and the scaffold degradation and systemic inflammatory reactions were observed at 3 days, 1 week, 3 weeks, and 6 weeks following surgery to determine the histocompatibility between xenografts. The effect of acellular scaffold extracts on fibroblast proliferation was assessed using an MTT assay to measure the cytotoxicity of the scaffold residual reagents. In addition, the umbilical cord from cesarean section fetuses was collected, and the Wharton's jelly (WJ) was separated into culture cells and confirm the osteogenic and adipogenic differentiation of mesenchymal stem cells (MSCs) and hUC-MSCs. The cultured cells were induced to differentiate into Schwann cells by the antioxidant-growth factor induction method, and the differentiated cells and the myelinogenic properties were identified.

RESULTS

The experiments effectively decellularized the sciatic nerve of the New Zealand rabbits. After comparing the completed acellular scaffolds among the groups, the optimal decellularization preparation steps were established as follows: Mechanical separation of the epineurium, two cycles of lyophilization-rewarming, trypsin digestion for 5 hours, and DNase digestion for 10 hours. After HE staining, no residual nuclear components were evident on the scaffold, whereas the extracellular matrix remained intact. LFB staining showed a significant decrease in myelin sheath composition of the scaffold compared with that before preparation. Biomechanical testing revealed that the maximum tensile strength, elastic modulus, and durability of the acellular scaffold were reduced compared with normal peripheral nerves. Based on the histocompatibility test, the immune response of the recipient SD rats to the scaffold New Zealand rabbits began to decline3 weeks following surgery, and there was no significant rejection after 6 weeks. The MTT assay revealed that the acellular reagent extract had no obvious effects on cell proliferation. The cells were successfully isolated, cultured, and passaged from human umbilical cord WJ by MSC medium, and their ability to differentiate into Schwann-like cells was demonstrated by morphological and immunohistochemical identification. The differentiated cells could also myelinate in vitro.

CONCLUSION

The acellular peripheral nerve scaffold with complete cell removal and intact matrix may be prepared by combining lyophilization and enzyme digestion. The resulting scaffold exhibited good histocompatibility and low cytotoxicity. In addition, hUC-MSCs have the potential to differentiate into Schwann-like cells with myelinogenic ability following in vitro induction.

Nanotherapeutic and Nano-Bio Interface for Regeneration and Healing

Wound and injury healing processes are intricate and multifaceted, involving a sequence of events from coagulation to scar tissue formation. Effective wound management is crucial for achieving favorable clinical outcomes. Understanding the cellular and molecular mechanisms underlying wound healing, inflammation, and regeneration is essential for developing innovative therapeutics. This review explored the interplay of cellular and molecular processes contributing to wound healing, focusing on inflammation, innervation, angiogenesis, and the role of cell surface adhesion molecules. Additionally, it delved into the significance of calcium signaling in skeletal muscle regeneration and its implications for regenerative medicine. Furthermore, the therapeutic targeting of cellular senescence for long-term wound healing was discussed. The integration of cutting-edge technologies, such as quantitative imaging and computational modeling, has revolutionized the current approach of wound healing dynamics. The review also highlighted the role of nanotechnology in tissue engineering and regenerative medicine, particularly in the development of nanomaterials and nano-bio tools for promoting wound regeneration. Moreover, emerging nano-bio interfaces facilitate the efficient transport of biomolecules crucial for regeneration. Overall, this review provided insights into the cellular and molecular mechanisms of wound healing and regeneration, emphasizing the significance of interdisciplinary approaches and innovative technologies in advancing regenerative therapies. Through harnessing the potential of nanoparticles, bio-mimetic matrices, and scaffolds, regenerative medicine offers promising avenues for restoring damaged tissues with unparalleled precision and efficacy. This pursuit marks a significant departure from traditional approaches, offering promising avenues for addressing longstanding challenges in cellular and tissue repair, thereby significantly contributing to the advancement of regenerative medicine.

Fabrication of Thymol-loaded Isabgol/Konjac Glucomannan-based Microporous Scaffolds with Enriched Antioxidant and Antibacterial Properties for Skin Tissue Engineering Applications

An antioxidant, antibacterial, and biocompatible biomaterial is essential to repair skin wounds effectively. Here, we have employed two natural biopolymers, isabgol (ISAB) and konjac glucomannan (KGM), to prepare microporous scaffolds by freezing and lyophilization. The scaffolds are loaded with thymol (THY) to impart potent antioxidant and antibacterial activities. The physicochemical properties of the ISAB+KGM+THY scaffold, like porosity (41.8±2.4 %), swelling, and biodegradation, were optimal for tissue regeneration application. Compared to the control, ISAB+KGM+THY scaffolds promote attachment, migration, and proliferation of L929 fibroblasts. The antioxidant activity of the ISAB+KGM+THY scaffold was significantly improved after loading THY. This would protect the tissues from oxidative damage. The antibacterial activity of the ISAB+KGM+THY scaffold was significantly higher than that of the control, which would help prevent bacterial infection. The vascularization ability of the ISAB+KGM scaffold was not altered by incorporating THY in the ISAB+KGM scaffold. Therefore, a strong antioxidant, antibacterial, and biocompatible nature of the ISAB+KGM+THY scaffold could be useful for various biomedical applications.

Advanced biomaterials for regenerative medicine and their possible therapeutic significance in treating COVID-19: a critical overview

The potential of biomaterials in medical sciences has attracted much interest, especially in promoting tissue regeneration and controlling immune responses. As the COVID-19 pandemic broke out, there was an increased interest in understanding more about how biomaterials could be employed to fight this dreaded disease, especially in the context of regenerative medicine. Out of the numerous regenerative medicine possibilities, stem cells and scaffolding (grafting) technology are two major areas in modern medicine and surgery. Mesenchymal stem cells are useful in tissue repair, tailored therapy and the treatment of COVID-19. Using biomaterials in COVID-19 treatment is intricate and needs multidisciplinary and cross-disciplinary research. Cell-based therapy and organ transplants pose immunological rejection challenges. Immunomodulation enhanced, tumorigenicity decreased, inflammation addressed and tissue damage restricted; bioengineered stem cells need clinical insights and validation. Advanced stem cell-based therapies should ideally be effective, safe and scalable. Cost and scalability shall dictate the dawn of techno-economically feasible regenerative medicine. A globally standard and uniform approval process could accelerate translational regenerative medicine. Researchers, patient advocacy organisations, regulators and biopharmaceutical stakeholders need to join hands for easy navigation of regulatory measures and expeditious market entry of regenerative medicine. This article summarises advances in biomaterials for regenerative medicine and their possible therapeutic benefits in managing infectious diseases like COVID-19. It highlights the significant recent developments in biomaterial design, scaffold construction, and stem cell-based therapies to treat tissue damage and COVID-19-linked immunological dysregulation. It also highlights the potential contribution of biomaterials towards creating novel treatment strategies to manage COVID-19.

Advances of naturally derived biomedical polymers in tissue engineering

The extensive utilization of natural polymers in tissue engineering is attributed to their excellent biocompatibility, degradability, and resemblance to the natural extracellular matrix. These polymers have a wide range of applications such as delivering therapeutic medicine, detecting diseases, sensing biological substances, promoting tissue regeneration, and treating diseases. This is a brief review of current developments in the properties and uses of widely used biomedical polymers derived from nature. Additionally, it explores the correlation between the characteristics and functions of these materials in different biomedical applications and highlights the prospective direction for the advancement of natural polymer materials in tissue engineering.

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

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

Optimizing scaffold pore size for tissue engineering: insights across various tissue types

Scaffold porosity is a critical factor in replicating the complex in vivo microenvironment, directly influencing cellular interactions, migration, nutrient transfer, vascularization, and the formation of functional tissues. For optimal tissue formation, scaffold design must account for various parameters, including material composition, morphology, mechanical properties, and cellular compatibility. This review highlights the importance of interconnected porosity and pore size, emphasizing their impact on cellular behavior and tissue formation across several tissue engineering domains, such as skin, bone, cardiovascular, and lung tissues. Specific pore size ranges enhance scaffold functionality for different tissues: small pores (∼1-2 µm) aid epidermal cell attachment in skin regeneration, moderate pores (∼2-12 µm) support dermal migration, and larger pores (∼40-100 µm) facilitate vascular structures. For bone tissue engineering, multi-layered scaffolds with smaller pores (50-100 µm) foster cell attachment, while larger pores (200-400 µm) enhance nutrient diffusion and angiogenesis. Cardiovascular and lung tissues benefit from moderate pore sizes (∼25-60 µm) to balance cell integration and nutrient diffusion. By addressing critical design challenges and optimizing pore size distributions, this review provides insights into scaffold innovations, ultimately advancing tissue regeneration strategies.

LCST/UCST behavior of polysaccharides for hydrogel fabrication

Hydrogel-based scaffolds play a crucial role in widespread biotechnological applications by providing physicochemical stability to loaded cells or therapeutic agents, interacting with organismal microenvironments, and controlling cargo release. Polysaccharides are regarded as attractive candidates among substrate materials because of their high water-retaining capacity, reactive functional groups, ease of gelation, low immunogenicity, biodegradability, and biocompatibility. However, employing polysaccharide-based hydrogel scaffolds for practical use in response to ongoing physiological and pathological changes within the human body, such as insufficient mechanical strength, uncertain degradation, and uncontrollable release patterns, is challenging. Several physically noncovalent or chemically covalent crosslinking strategies have been utilized to modify the physicochemical properties and biofunctionality of polysaccharide-based hydrogels. Among them, thermo-responsive gelation systems have been considered a promising approach for fabricating advanced scaffolds, referred to as 'stimuli-responsive' or 'smart' hydrogels. This is because of the sol-gel transition with a single trigger, requiring no further environmental or chemical intervention, and in situ and reversible gelation under ambient physiological temperature changes in a minimally invasive manner. This review highlights the classification, reaction mechanisms, characteristics, and advanced studies on thermo-responsive polysaccharides exploited in various biomedical fields.

Enhancing bone repair through improved angiogenesis and osteogenesis using mesoporous silica nanoparticle-loaded Konjac glucomannan-based interpenetrating network scaffolds

We have fabricated and characterized novel bioactive nanocomposite interpenetrating polymer network (IPN) scaffolds to treat bone defects by loading mesoporous silica nanoparticles (MSNs) into blends of Konjac glucomannan, polyvinyl alcohol, and polycaprolactone. By loading MSNs, we developed a porous nanocomposite scaffold with mechanical strengths comparable to cancellous bone. In vitro cell culture studies proved the cytocompatibility of the nanocomposite scaffolds. RT-PCR studies confirmed that these scaffolds significantly upregulated major osteogenic markers. The in vivo chick chorioallantoic membrane (CAM) assay confirmed the proangiogenic activity of the nanocomposite IPN scaffolds. In vivo studies were performed using Wistar rats to evaluate the scaffolds' compatibility, osteogenic activity, and proangiogenic properties. Liver and renal function tests confirmed that these scaffolds were nontoxic. X-ray and μ-CT results show that the bone defects treated with the nanocomposite scaffolds healed at a much faster rate compared to the untreated control and those treated with IPN scaffolds. H&E and Masson's trichrome staining showed angiogenesis near the newly formed bone and the presence of early-stage connective tissues, fibroblasts, and osteoblasts in the defect region at 8 weeks after surgery. Hence, these advantageous physicochemical and biological properties confirm that the nanocomposite IPN scaffolds are ideal for treating bone defects.

Theranostic Applications of Scaffolds in Current Biomedical Research

Theranostics, a remarkable combination of diagnostics and therapeutics, has given rise to tissue/organ-format theranostic scaffolds that integrate targeted therapy and real-time disease monitoring. The scaffold is a 3D structuring template for cell or tissue attachment and growth. These scaffolds offer unprecedented opportunities for personalized medicine and hold great potential for revolutionizing healthcare. Recent advancements in fabrication techniques have enabled the creation of highly intricate and precisely engineered scaffolds with controllable physical and chemical properties, enhancing their therapeutic potential for tissue engineering and regenerative medicine. This paper proposes a new categorization method for scaffolds in tissue engineering based on the relativity of scaffold design-independent parameters. Five types of scaffolds are defined at different levels, highlighting the importance of understanding and analyzing scaffold types. It possesses the ability to seamlessly integrate diagnostics and therapeutics within a single platform, enhancing the efficacy and precision of personalized medicine. Natural scaffolds derived from biomaterials and synthetic scaffolds fabricated by human intervention are discussed, with synthetic scaffolds offering advantages such as tunable mechanical properties and controlled drug delivery, while natural scaffolds provide inherent biocompatibility and bioactivity, making them ideal for promoting cellular responses. The use of synthetic scaffolds shows great promise in advancing regenerative medicine and improving patient outcomes. The transfer of new technologies and changes in society have accelerated the evolution of health monitoring into the era of personal health monitoring. Using emerging health data, cost-effective analytics, wireless sensor networks, mobile smartphones, and easy internet access, the combination of these technologies is expected to accelerate the transition to personal health monitoring outside of traditional healthcare settings. The main objective of this review article is to provide a comprehensive overview of the theranostic applications of scaffolds in current biomedical research, highlighting their dual role in therapy and diagnostics. The review aims to explore the latest advancements in scaffold design, fabrication, and functionalization, emphasizing how these innovations contribute to improved therapeutic efficacy, targeted drug delivery, and the real-time monitoring of disease progression across various medical fields.

Advanced Polymeric Scaffolds for Stem Cell Engineering and Regenerative Medicine

Polymeric scaffolds play a pivotal role in tissue engineering (TE) and regenerative medicine strategies, as they offer the possibility to closely mimic the architectural features of the native tissues' extracellular matrix (ECM) and support cell performance both in vitro and in vivo, creating a favourable regenerative microenvironment [...].

Soft material drilling: A thermo-mechanical analysis of polyurethane foam for biomimetic bone scaffolds and optimization of process parameters using Taguchi method

Drilling is a widely employed technique in machining processes, crucial for efficient material removal. However, when applied to living tissues, its invasiveness must be carefully considered. This study investigates drilling processes on polyurethane foam blocks mimicking human bone mechanical properties. Various drill bit types (118° twist, 135° twist, spherical, and conical), drilling speeds (1000-1600 rpm), and feed rates (20-80 mm/min) were examined to assess temperature elevation during drilling. The Taguchi method facilitated systematic experiment design and optimization. Signal-to-noise (S/N) ratio and analysis of variance (ANOVA) identified significant drilling parameters affecting temperature rise. Validation was conducted through confirmation testing. Results indicate that standard twist drill bits with smaller point angles, lower drilling speeds, and higher feed rates effectively minimize temperature elevation during drilling.

Electrically conductive coatings in tissue engineering

Recent interest in tissue engineering (TE) has focused on electrically conductive biomaterials. This has been inspired by the characteristics of the cells' microenvironment where signalling is supported by electrical stimulation. Numerous studies have demonstrated the positive influence of electrical stimulation on cell excitation to proliferate, differentiate, and deposit extracellular matrix. Even without external electrical stimulation, research shows that electrically active scaffolds can improve tissue regeneration capacity. Tissues like bone, muscle, and neural contain electrically excitable cells that respond to electrical cues provided by implanted biomaterials. To introduce an electrical pathway, TE scaffolds can incorporate conductive polymers, metallic nanoparticles, and ceramic nanostructures. However, these materials often do not meet implantation criteria, such as maintaining mechanical durability and degradation characteristics, making them unsuitable as scaffold matrices. Instead, depositing conductive layers on TE scaffolds has shown promise as an efficient alternative to creating electrically conductive structures. A stratified scaffold with an electroactive surface synergistically excites the cells through active top-pathway, with/without electrical stimulation, providing an ideal matrix for cell growth, proliferation, and tissue deposition. Additionally, these conductive coatings can be enriched with bioactive or pharmaceutical components to enhance the scaffold's biomedical performance. This review covers recent developments in electrically active biomedical coatings for TE. The physicochemical and biological properties of conductive coating materials, including polymers (polypyrrole, polyaniline and PEDOT:PSS), metallic nanoparticles (gold, silver) and inorganic (ceramic) particles (carbon nanotubes, graphene-based materials and Mxenes) are examined. Each section explores the conductive coatings' deposition techniques, deposition parameters, conductivity ranges, deposit morphology, cell responses, and toxicity levels in detail. Furthermore, the applications of these conductive layers, primarily in bone, muscle, and neural TE are considered, and findings from in vitro and in vivo investigations are presented. STATEMENT OF SIGNIFICANCE: Tissue engineering (TE) scaffolds are crucial for human tissue replacement and acceleration of healing. Neural, muscle, bone, and skin tissues have electrically excitable cells, and their regeneration can be enhanced by electrically conductive scaffolds. However, standalone conductive materials often fall short for TE applications. An effective approach involves coating scaffolds with a conductive layer, finely tuning surface properties while leveraging the scaffold's innate biological and physical support. Further enhancement is achieved by modifying the conductive layer with pharmaceutical components. This review explores the under-reviewed topic of conductive coatings in tissue engineering, introducing conductive biomaterial coatings and analyzing their biological interactions. It provides insights into enhancing scaffold functionality for tissue regeneration, bridging a critical gap in current literature.

Advancing 3D Spheroid Research through 3D Scaffolds Made by Two-Photon Polymerization

Three-dimensional cancer cell cultures have been a valuable research model for developing new drug targets in the preclinical stage. However, there are still limitations to these in vitro models. Scaffold-based systems offer a promising approach to overcoming these challenges in cancer research. In this study, we show that two-photon polymerization (TPP)-assisted printing of scaffolds enhances 3D tumor cell culture formation without additional modifications. TPP is a perfect fit for this task, as it is an advanced 3D-printing technique combining a μm-level resolution with complete freedom in the design of the final structure. Additionally, it can use a wide array of materials, including biocompatible ones. We exploit these capabilities to fabricate scaffolds from two different biocompatible materials-PEGDA and OrmoClear. Cubic spheroid scaffolds with a more complex architecture were produced and tested. The biological evaluation showed that the human ovarian cancer cell lines SKOV3 and A2780 formed 3D cultures on printed scaffolds without a preference for the material. The gene expression evaluation showed that the A2780 cell line exhibited substantial changes in CDH1, CDH2, TWIST, COL1A1, and SMAD3 gene expression, while the SKOV3 cell line had slight changes in said gene expression. Our findings show how the scaffold architecture design impacts tumor cell culture 3D spheroid formation, especially for the A2780 cancer cell line.

Supramolecular Composite Hydrogel Loaded with CaF2 Nanoparticles Promotes the Recovery of Periodontitis Bone Resorption

Treatments to reduce periodontal inflammation and rescue periodontitis bone resorption have been of interest to researchers. Bone tissue engineering materials have been gradually used in the treatment of bone defects, but periodontal bone tissue regeneration still faces challenges. Considering the biocompatibility factor, constructing bionic scaffolds with natural extracellular matrix properties is an ideal therapeutic pathway. Based on the pathological mechanism of periodontitis, in this study, short peptide and nanometer inorganic particles were comingled to construct NapKFF-nano CaF2 supramolecular composite hydrogels with different ratios. Material characterization experiments confirmed that the composite hydrogel had suitable mechanical properties and a three-dimensional structure that can function in the resorption region of the alveolar bone and provide spaces for cell proliferation and adhesion. The release of low concentrations of fluoride and calcium ions has been shown to have positive biological effects in both in vivo and in vitro experiments. Vitro experiments confirmed that the composite hydrogel had good biocompatibility and promoted osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Microbiological experiments confirmed that the composite hydrogel inhibited the activity of periodontal pathogenic bacteria. In animal studies, composite hydrogel applied to periodontitis rats in vivo can effectively repair alveolar bone resorption. This composite hydrogel has a simple preparation method and is inexpensive to produce, yet it has antibacterial and osteogenesis-promoting incremental effects, which makes it well suited for the treatment of periodontitis bone resorption, providing a new strategy for periodontal bone tissue engineering.

Fabrication of bacterial cellulose/PVP nanofiber composites by electrospinning

This study aimed to address a significant challenge in the application of bacterial cellulose (BC) within tissue engineering and regenerative medicine by tackling its inherent insolubility in water and organic solvents. Our team introduced a groundbreaking approach by utilizing zinc sulfate (ZnSO4) as a solvent to render BC soluble, a novel contribution to the literature. Subsequently, the obtained soluble BC was combined with varying concentrations of polyvinylpyrrolidone (PVP). Notably, we pioneered the fabrication of BC/PVP composite scaffolds with customizable fiber surface morphology and regulated degradation rates through the electrospun technique. Several key parameters, such as PVP concentration (8%, 15%, 12%, and 20% w/v), applied voltage (22, 15, and 12 kV), and a fixed nozzle-collector distance of 10 cm with a flow rate of 0.9 mL/h, were systematically evaluated so as to find the optimum parameter created BC/PVP product with electrospun. For electrospun BC/PVP products, a voltage of 12 kV was found to be optimal. Intriguingly, our findings revealed enhanced cell adhesion and proliferation in BC/PVP electrospun products compared with using PVP membranes alone. Specifically, cell viability for PVP and PVP/BC electrospun products was determined as 50.73% and 79.95%, respectively. In terms of thermal properties, the BC/PVP electrospun product exhibited a mass loss of 82.6% at 380°C, while PVP alone experienced 90.2% mass loss at around 280°C. Furthermore, the protein adhesion capacities were measured at 62.3 ± 1.2 μg for PVP and 99.4 ± 2 μg for BC/PVP electrospun products, whereas product showed no biodegradation over 28 days and had notable water retention capacity. In conclusion, our research not only successfully attained nanofiber morphology but also showcased enhanced cell attachment and proliferation on the BC/PVP electrospun product.

Enhanced Piezoelectric Performance of PVDF-TrFE Nanofibers through Annealing for Tissue Engineering Applications

This study investigates bioelectric stimulation's role in tissue regeneration by enhancing the piezoelectric properties of tissue-engineered grafts using annealed poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) scaffolds. Annealing at temperatures of 80°C, 100°C, 120°C, and 140°C was assessed for its impact on material properties and physiological utility. Analytical techniques such as Differential Scanning Calorimetry (DSC), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) revealed increased crystallinity with higher annealing temperatures, peaking in β-phase content and crystallinity at 140°C. Scanning Electron Microscopy (SEM) showed that 140°C annealed scaffolds had enhanced lamellar structures, increased porosity, and maximum piezoelectric response. Mechanical tests indicated that 140°C annealing improved elastic modulus, tensile strength, and substrate stiffness, aligning these properties with physiological soft tissues. In vitro assessments in Schwann cells demonstrated favorable responses, with increased cell proliferation, contraction, and extracellular matrix attachment. Additionally, genes linked to extracellular matrix production, vascularization, and calcium signaling were upregulated. The foreign body response in C57BL/6 mice, evaluated through Hematoxylin and Eosin (H&E) and Picrosirius Red staining, showed no differences between scaffold groups, supporting the potential for future functional evaluation of the annealed group in tissue repair.

Microstructural, Fluid Dynamic, and Mechanical Characterization of Zinc Oxide and Magnesium Chloride-Modified Hydrogel Scaffolds

Scaffolds for the filling and regeneration of osteochondral defects are a current challenge in the biomaterials field, and solutions with greater functionality are still being sought. The novel approach of this work was to obtain scaffolds with biologically active additives possessing microstructural, permeability, and mechanical properties, mimicking the complexity of natural cartilage. Four types of scaffolds with a gelatin/alginate matrix modified with hydroxyapatite were obtained, and the relationship between the modifiers and substrate properties was evaluated. They differed in the type of second modifier used, which was hydrated MgCl2 in two proportions, ZnO, and nanohydroxyapatite. The samples were obtained by freeze-drying by using two-stage freezing. Based on microstructural observations combined with X-ray microanalysis, the microstructure of the samples and the elemental content were assessed. Permeability and mechanical tests were also performed. The scaffolds exhibited a network of interconnected pores and complex microarchitecture, with lower porosity at the surface (15 ± 7 to 29 ± 6%) and higher porosity at the center (67 ± 8 to 75 ± 8%). The additives had varying effects on the pore sizes and permeabilities of the samples. ZnO yielded the most permeable scaffolds (5.92 × 10-11 m2), whereas nanohydroxyapatite yielded the scaffold with the lowest permeability (1.18 × 10-11 m2), values within the range reported for trabecular bone. The magnesium content had no statistically significant effect on the permeability. The best mechanical parameters were obtained for ZnO samples and those containing hydrated MgCl2. The scaffold's properties meet the criteria for filling osteochondral defects. The developed scaffolds follow a biomimetic approach in terms of hierarchical microarchitecture and mechanical parameters as well as chemical composition. The obtained composite materials have the potential as biomimetic scaffolds for the regeneration of osteochondral defects.

Water-powered, electronics-free dressings that electrically stimulate wounds for rapid wound closure

Chronic wounds affect ~2% of the U.S. population and increase risks of amputation and mortality. Unfortunately, treatments for such wounds are often expensive, complex, and only moderately effective. Electrotherapy represents a cost-effective treatment; however, its reliance on bulky equipment limits its clinical use. Here, we introduce water-powered, electronics-free dressings (WPEDs) that offer a unique solution to this issue. The WPED performs even under harsh conditions-situations wherein many present treatments fail. It uses a flexible, biocompatible magnesium-silver/silver chloride battery and a pair of stimulation electrodes; upon the addition of water, the battery creates a radial electric field. Experiments in diabetic mice confirm the WPED's ability to accelerate wound closure and promote healing by increasing epidermal thickness, modulating inflammation, and promoting angiogenesis. Across preclinical wound models, the WPED-treated group heals faster than the control with wound closure rates comparable to treatments requiring expensive biologics and/or complex electronics. The results demonstrate the WPED's potential as an effective and more practical wound treatment dressing.

Evaluation of Articular Cartilage Regeneration Properties of Decellularized Cartilage Powder/Modified Hyaluronic Acid Hydrogel Scaffolds

The articular cartilage has poor intrinsic healing potential, hence, imposing a great challenge for articular cartilage regeneration in osteoarthritis. Tissue regeneration by scaffolds and bioactive materials has provided a healing potential for degenerated cartilage. In this study, decellularized cartilage powder (DCP) and hyaluronic acid hydrogel modified by aldehyde groups and methacrylate (AHAMA) were fabricated and evaluated in vitro for efficacy in articular cartilage regeneration. In vitro tests such as cell proliferation, cell viability, and cell migration showed that DCP/AHAMA has negligible cytotoxic effects. Furthermore, it could provide an enhanced microenvironment for infrapatellar fat pad stem cells (IFPSCs). Mechanical property tests of DCP/AHAMA showed suitable adhesive and compressive strength. IFPSCs under three-dimensional (3D) culture in DCP/AMAHA were used to assess their ability to proliferate and differentiate into chondrocytes using normal and chondroinductive media. Results exhibited increased gene expression of COL2 and ACN and decreased COL1 expression. DCP/AHAMA provides a microenvironment that recapitulates the biomechanical properties of the native cartilage, promotes chondrogenic differentiation, blocks hypertrophy, and demonstrates applicability for cartilage tissue engineering and the potential for clinical biomedical applications.

Tissue engineering and regenerative medicine approaches in colorectal surgery

Tissue engineering and regenerative medicine (TERM) is an emerging field that has provided new therapeutic opportunities by delivering innovative solutions. The development of nontraditional therapies for previously unsolvable diseases and conditions has brought hope and excitement to countless individuals globally. Many regenerative medicine therapies have been developed and delivered to patients clinically. The technology platforms developed in regenerative medicine have been expanded to various medical areas; however, their applications in colorectal surgery remain limited. Applying TERM technologies to engineer biological tissue and organ substitutes may address the current therapeutic challenges and overcome some complications in colorectal surgery, such as inflammatory bowel diseases, short bowel syndrome, and diseases of motility and neuromuscular function. This review provides a comprehensive overview of TERM applications in colorectal surgery, highlighting the current state of the art, including preclinical and clinical studies, current challenges, and future perspectives. This article synthesizes the latest findings, providing a valuable resource for clinicians and researchers aiming to integrate TERM into colorectal surgical practice.

Engineering a robust and anisotropic cardiac-specific extracellular matrix scaffold for cardiac patch tissue engineering

Extracellular matrix (ECM) fabricated using human induced pluripotent stem cells (hiPSCs)-derived cardiac fibroblasts (hiPSC-CFs) could serve as a completely biological scaffold for an engineered cardiac patch, leveraging the unlimited source and outstanding reproducibility of hiPSC-CFs. Additionally, hiPSC-CF-derived ECM (hiPSC-CF-ECM) holds the potential to enhance maturation of exogenous cardiomyocytes, such as hiPSC-derived cardiomyocytes (hiPSC-CMs), by providing a microenvironment rich in cardiac-specific biochemical and signaling cues. However, achieving sufficient robustness of hiPSC-CF-ECM is challenging. This study aims to achieve appropriate ECM deposition, scaffold thickness, and mechanical strength of an aligned hiPSC-CF-ECM by optimizing the culture period, ranging from 2 to 10 weeks, of hiPSC-CFs grown on micro-grated substrates, which can direct the alignment of both hiPSC-CFs and their secreted ECM. The hiPSC-CFs demonstrated a production rate of 13.5 µg ECM per day per 20,000 cells seeded. An anisotropic nanofibrous hiPSC-CF-ECM scaffold with a thickness of 20.0 ± 2.1 µm was achieved after 6 weeks of culture, followed by decellularization. Compositional analysis through liquid chromatography-mass spectrometry (LC-MS) revealed the presence of cardiac-specific fibrillar collagens, non-fibrillar collagens, and matricellular proteins. Uniaxial tensile stretching of the hiPSC-CF-ECM scaffold indicated robust tensile resilience. Finally, hiPSCs-CMs cultured on the hiPSC-CF-ECM exhibited alignment following the guidance of ECM nanofibers and demonstrated mature organization of key structural proteins. The culture duration of the anisotropic hiPSC-CF-ECM was successfully refined to achieve a robust scaffold containing structural proteins that resembles cardiac microenvironment. This completely biological, anisotropic, and cardiac-specific ECM holds great potential for cardiac patch engineering.

In vivo characterization of a luffa-based composite scaffold for subcutaneous implantation in rats

Recent advancements in tissue engineering have witnessed luffa-derived scaffolds, exhibiting their exceptional potential in cellular proliferation, biocompatibility, appropriate interconnectivity, and biomechanical strength. In vivo studies involved implanting fabricated scaffolds subcutaneously in Wistar rats to evaluate their impact on the heart, liver, and kidneys. This approach provided a safe and minimally invasive means to evaluate scaffold compatibility with surrounding tissues. Male Wistar rats were categorized into four distinct groups, Group A, B, C, and D are referred to as 3% LC implanted scaffolds, 5% LC implanted scaffolds, control (without luffa scaffolds), and Sham (without any scaffold implantation), respectively. Histological analysis in all the groups indicated that the animal models did not exhibit any signs of inflammation or toxicity, suggesting favorable tissue response to the implanted scaffolds. Initial observations revealed elevated levels of enzymes and biomarkers in the experimental groups after a 24 h interval, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), bilirubin, creatine kinase-MB (CK-MB), and serum creatinine. However, these parameters normalized 3 weeks post-implantation, with no significant increase compared to the control groups, suggesting that the implanted luffa-based scaffolds did not induce adverse effects on the heart, liver, and kidneys. Furthermore, the scaffold's significant pore size and porosity enable it to release drugs, including antibacterial medications. This study demonstrates promising results, indicating excellent scaffold porosity, sustained drug release, affirming the in vivo biocompatibility, absence of inflammatory responses, and overall tissue compatibility highlighting the immense potential of these luffa-based scaffolds in various tissue engineering and regenerative medicine applications.

Navigating the challenges and exploring the perspectives associated with emerging novel biomaterials

The field of biomaterials is a continuously evolving interdisciplinary field encompassing biological sciences, materials sciences, chemical sciences, and physical sciences with a multitude of applications realized every year. However, different biomaterials developed for different applications have unique challenges in the form of biological barriers, and addressing these challenges simultaneously is also a challenge. Nevertheless, immense progress has been made through the development of novel materials with minimal adverse effects such as DNA nanostructures, specific synthesis strategies based on supramolecular chemistry, and modulating the shortcomings of existing biomaterials through effective functionalization techniques. This review discusses all these aspects of biomaterials, including the challenges at each level of their development and application, proposed countermeasures for these challenges, and some future directions that may have potential benefits.

3D-Bioprinted Gelatin Methacryloyl-Strontium-Doped Hydroxyapatite Composite Hydrogels Scaffolds for Bone Tissue Regeneration

New gelatin methacryloyl (GelMA)-strontium-doped nanosize hydroxyapatite (SrHA) composite hydrogel scaffolds were developed using UV photo-crosslinking and 3D printing for bone tissue regeneration, with the controlled delivery capacity of strontium (Sr). While Sr is an effective anti-osteoporotic agent with both anti-resorptive and anabolic properties, it has several important side effects when systemic administration is applied. Multi-layer composite scaffolds for bone tissue regeneration were developed based on the digital light processing (DLP) 3D printing technique through the photopolymerization of GelMA. The chemical, morphological, and biocompatibility properties of these scaffolds were investigated. The composite gels were shown to be suitable for 3D printing. In vitro cell culture showed that osteoblasts can adhere and proliferate on the surface of the hydrogel, indicating that the GelMA-SrHA hydrogel has good cell viability and biocompatibility. The GelMA-SrHA composites are promising 3D-printed scaffolds for bone repair.

Production and Characterization of Melt-Spun Poly(3-hydroxybutyrate)/Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Blend Monofilaments

We investigated the melt-spinning potential of a poly(3-hydroxybutyrate)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blend using a piston spinning machine with two different spinneret diameters (0.2 and 0.5 mm). Results from the differential scanning calorimetry, dynamic mechanical thermal analysis, and tensile testing showed distinct filament properties depending on the monofilaments' cross-sectional area. Finer filaments possessed different melting behaviors compared to the coarser filaments and the neat polymer, indicating the formation of a different type of polymer crystal. Additionally, the mechanical properties of the finer filament (tensile strength: 21.5 MPa and elongation at break: 341%) differed markedly from the coarser filament (tensile strength: 11.7 MPa, elongation at break: 12.3%). The hydrolytic stability of the filaments was evaluated for 7 weeks in a phosphate-buffered saline solution and showed a considerably reduced elongation at break of the thinner filaments. Overall, the results indicate considerable potential for further filament improvements to facilitate textile processing.

Bilayer Scaffolds of PLLA/PCL/CAB Ternary Blend Films and Curcumin-Incorporated PLGA Electrospun Nanofibers: The Effects of Polymer Compositions and Solvents on Morphology and Molecular Interactions

Tissue engineering scaffolds have been dedicated to regenerating damaged tissue by serving as host biomaterials for cell adhesion, growth, differentiation, and proliferation to develop new tissue. In this work, the design and fabrication of a biodegradable bilayer scaffold consisting of a ternary PLLA/PCL/CAB blend film layer and a PLGA/curcumin (CC) electrospun fiber layer were studied and discussed in terms of surface morphology, tensile mechanical properties, and molecular interactions. Three different compositions of PLLA/PCL/CAB-60/15/25 (TBF1), 75/10/15 (TBF2), and 85/5/10 (TBF3)-were fabricated using the solvent casting method. The electrospun fibers of PLGA/CC were fabricated using chloroform (CF) and dimethylformamide (DMF) co-solvents in 50:50 and 60:40 volume ratios. Spherical patterns of varying sizes were observed on the surfaces of all blend films-TBF1 (17-21 µm) > TBF2 (5-9 µm) > TBF3 (1-5 µm)-caused by heterogeneous surfaces inducing bubble nucleation. The TBF1, TBF2, and TBF3 films showed tensile elongation at break values of approximately 170%, 94%, and 43%, respectively. The PLGA/CC electrospun fibers fabricated using 50:50 CF:DMF had diameters ranging from 100 to 400 nm, which were larger than those of the PLGA fibers (50-200 nm). In contrast, the PLGA/CC electrospun fibers fabricated using 60:40 CF:DMF had diameters mostly ranging from 200 to 700 nm, which were larger than those of PLGA fibers (200-500 nm). Molecular interactions via hydrogen bonding were observed between PLGA and CC. The surface morphology of the bilayer scaffold demonstrated adhesion between these two solid surfaces resembling "thread stitches" promoted by hydrophobic interactions, hydrogen bonding, and surface roughness.

Fabrication of k-Carrageenan/Alginate/Carboxymethyl Cellulose basedScaffolds via 3D Printing for Potential Biomedical Applications

Three-dimensional (3D) printing technology was able to generate great attention because of its unique methodology and for its major potential to manufacture detailed and customizable scaffolds in terms of size, shape and pore structure in fields like medicine, pharmaceutics and food. This study aims to fabricate an ink entirely composed of natural polymers, alginate, k-carrageenan and carboxymethyl cellulose (AkCMC). Extrusion-based 3D printing was used to obtain scaffolds based on a crosslinked interpenetrating polymer network from the alginate, k-carrageenan, carboxymethyl cellulose and glutaraldehide formulation using CaCl2, KCl and glutaraldehyde in various concentrations of acetic acid. The stabile bonding of the crosslinked scaffolds was assessed using infrared spectroscopy (FT-IR) as well as swelling, degradation and mechanical investigations. Moreover, morphology analysis (µCT and SEM) confirmed the 3D printed samples' porous structure. In the AkCMC-GA objects crosslinked with the biggest acetic acid concentration, the values of pores and walls are the highest, at 3.9 × 10-2 µm-1. Additionally, this research proves the encapsulation of vitamin B1 via FT-IR and UV-Vis spectroscopy. The highest encapsulation efficiency of vitamin B1 was registered for the AkCMC-GA samples crosslinked with the maximum acetic acid concentration. The kinetic release of the vitamin was evaluated by UV-Vis spectroscopy. Based on the results of these experiments, 3D printed constructs using AkCMC-GA ink could be used for soft tissue engineering applications and also for vitamin B1 encapsulation.

Chitosan-based injectable hydrogel with multifunction for wound healing: A critical review

Different types of clinical wounds are difficult to treat while infected by bacteria. Wound repair involves multiple cellular and molecular interactions, which is a complicated process. However, wound repair often suffers from abnormal cellular functions or pathways that result in unavoidable side effects, so there is an urgent need for a material that can heal wounds quickly and with few side effects. Based on these needs, hydrogels with injectable properties have been confirmed to be able to undergo self-healing, which provides favorable conditions for wound healing. Notably, as a biopolymer with excellent easy-to-modify properties from a wide range of natural sources, chitosan can be used to prepare injectable hydrogel with multifunction for wound healing because of its outstanding flowability and injectability. Especially, chitosan-based hydrogels with marked biocompatibility, non-toxicity, and bio-adhesion properties are ideal for facilitating wound healing. In this review, the characteristics and healing mechanisms of different wounds are briefly summarized. In addition, the preparation and characterization of injectable chitosan hydrogels in recent years are classified. Additionally, the bioactive properties of this type of hydrogel in vitro and in vivo are demonstrated, and future trend in wound healing is prospected.

Impact of the Different Chemical-Based Decellularization Protocols on the Properties of the Caprine Pericardium

PURPOSE

This study aims to decellularized caprine pericardium tissue with varied non-ionic surfactant and anionic detergent concentrations.

METHODS

Protocol A consists of 1%, 0.5%, and 0.25% (w/v) sodium dodecyl sulphate (SDS). Protocol B uses 1%, 0.5%, and 0.25% (w/v) Triton X-100. Protocol C comprised 0.5% SDS + 0.5% Triton X-100, 0.5% + 0.25%, and 0.25% SDS + 0.5% Triton X-100.

RESULTS

Protocol B left a few countable cells in the pericardium tissue, but treatments A and C removed all cells. DNA quantification also demonstrated that protocol B had the most leftover DNA after decellularization. The pericardium tissue treated with an equal combination of anionic detergent and non-ionic surfactant preserves the matrix. However, changing the anionic detergent-non-ionic surfactant ratio disrupted the microstructure. Protocol A decreased pericardium tissue secant modulus (p < 0.05). Protocol B-treated pericardium tissue matched native tissue secant modulus and ultimate tensile stress. Protocol C strengthened pericardium tissue.

CONCLUSION

The intact extracellular matrix and biomechanical properties like native tissues require optimal chemical doses and combinations.

Intervertebral disc degeneration and regenerative medicine

Intervertebral disc (IVD) degeneration is a common phenomenon that affects patients with increasing prevalence with increasing age. Both conservative treatments, such as the use of pain medication or physical therapy, and surgical treatments, such as fusion or disc replacement therapies, are offered to patients. Both non‐invasive and invasive treatments have been shown to improve pain and quality of life for patients. This review explores the role of regenerative medicine techniques as a promising therapeutic intervention that can be used before or in combination with conservative therapy and surgery to enhance the treatment process in patients with IVD degeneration or disc pathology. Currently, there are four major modules of regenerative medicine: genetic therapy, platelet‐rich plasma therapy, stem cell transplantation and tissue engineering. Several research studies have shown promising outcomes of stem cell transplantation and tissue engineering when combined with either surgical or conservative treatment, resulting in improved pain outcomes. The additional benefit of regenerative medicine techniques, specifically stem cell transplantation, is the potential for treating the root pathology of degeneration. Regenerative medicine techniques also have the potential to either halt or reverse degeneration as opposed to current standards of care for managing symptoms. There is a plethora of current research highlighting the benefits of regenerative medicine techniques; however, there remains clinical concerns and ethical concerns regarding the use of regenerative therapy techniques such as stem cell transplantation in the context of IVD degeneration.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.