A bilayer scaffold prepared from collagen and carboxymethyl cellulose for skin tissue engineering applications

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.

Topical hADSCs-HA Gel Promotes Skin Regeneration and Angiogenesis in Pressure Ulcers by Paracrine Activating PPARβ/δ Pathway

Background

Pressure ulcer is common in the bedridden elderly with high mortality and lack of effective treatment. In this study, human-adipose-derived-stem-cells-hyaluronic acid gel (hADSCs-HA gel) was developed and applied topically to treat pressure ulcers, of which efficacy and paracrine mechanisms were investigated through in vivo and in vitro experiments.

Methods

Pressure ulcers were established on the backs of C57BL/6 mice and treated topically with hADSCs-HA gel, hADSCs, hyaluronic acid, and normal saline respectively. The rate of wound closure was observed continuously during the following 14 days and the wound samples were obtained for Western blot, histopathology, immunohistochemistry, and proteomic analysis. Human dermal fibroblasts (HDFs) and human venous endothelial cells (HUVECs) under normal or hypoxic conditions were treated with conditioned medium of human ADSCs (ADSC-CM), then CCK-8, scratch test, tube formation, and Western blot were conducted to evaluate the paracrine effects of hADSCs and to explore the underlying mechanism.

Results

The in vivo data demonstrated that hADSCs-HA gel significantly accelerated the healing of pressure ulcers by enhancing collagen expression, angiogenesis, and skin proliferation. The in vitro data revealed that hADSCs strengthened the proliferation and wound healing capabilities of HDFs and HUVECs, meanwhile promoted collagen secretion and tube formation through paracrine mode. ADSC-CM was also proved to exert protective effects on hypoxic HDFs and HUVECs. Besides, the results of proteomic analysis and Western blot elucidated that lipid metabolism and PPARβ/δ pathway mediated the healing effect of hADSCs-HA gel on pressure ulcers.

Conclusion

Our research showed that topical application of hADSCs-HA gel played an important role in dermal regeneration and angiogenesis. Therefore, hADSCs-HA gel exhibited the potential as a novel stem-cell-based therapeutic strategy of treating pressure ulcers in clinical practices.

Bovine Placentome-Derived Extracellular Matrix: A Sustainable 3D Scaffold for Cultivated Meat

Cultivated meat, an advancement in cellular agriculture, holds promise in addressing environmental, ethical, and health challenges associated with traditional meat production. Utilizing tissue engineering principles, cultivated meat production employs biomaterials and technologies to create cell-based structures by introducing cells into a biocompatible scaffold, mimicking tissue organization. Among the cell sources used for producing muscle-like tissue for cultivated meats, primary adult stem cells like muscle satellite cells exhibit robust capabilities for proliferation and differentiation into myocytes, presenting a promising avenue for cultivated meat production. Evolutionarily optimized for growth in a 3D microenvironment, these cells benefit from the biochemical and biophysical cues provided by the extracellular matrix (ECM), regulating cell organization, interactions, and behavior. While plant protein-based scaffolds have been explored for their utilization for cultivated meat, they lack the biological cues for animal cells unless functionalized. Conversely, a decellularized bovine placental tissue ECM, processed from discarded birth tissue, achieves the biological functionalities of animal tissue ECM without harming animals. In this study, collagen and total ECM were prepared from decellularized bovine placental tissues. The collagen content was determined to be approximately 70% and 40% in isolated collagen and ECM, respectively. The resulting porous scaffolds, crosslinked through a dehydrothermal (DHT) crosslinking method without chemical crosslinking agents, supported the growth of bovine myoblasts. ECM scaffolds exhibited superior compatibility and stability compared to collagen scaffolds. In an attempt to make cultivate meat constructs, bovine myoblasts were cultured in steak-shaped ECM scaffolds for about 50 days. The resulting construct not only resembled muscle tissues but also displayed high cellularity with indications of myogenic differentiation. Furthermore, the meat constructs were cookable and able to sustain the grilling/frying. Our study is the first to utilize a unique bovine placentome-derived ECM scaffold to create a muscle tissue-like meat construct, demonstrating a promising and sustainable option for cultivated meat production.

Functionalised Sodium-Carboxymethylcellulose-Collagen Bioactive Bilayer as an Acellular Skin Substitute for Future Use in Diabetic Wound Management: The Evaluation of Physicochemical, Cell Viability, and Antibacterial Effects

The wound healing mechanism is dynamic and well-orchestrated; yet, it is a complicated process. The hallmark of wound healing is to promote wound regeneration in less time without invading skin pathogens at the injury site. This study developed a sodium-carboxymethylcellulose (Na-CMC) bilayer scaffold that was later integrated with silver nanoparticles/graphene quantum dot nanoparticles (AgNPs/GQDs) as an acellular skin substitute for future use in diabetic wounds. The bilayer scaffold was prepared by layering the Na-CMC gauze onto the ovine tendon collagen type 1 (OTC-1). The bilayer scaffold was post-crosslinked with 0.1% (w/v) genipin (GNP) as a natural crosslinking agent. The physical and chemical characteristics of the bilayer scaffold were evaluated. The results demonstrate that crosslinked (CL) groups exhibited a high-water absorption capacity (>1000%) and an ideal water vapour evaporation rate (2000 g/m2 h) with a lower biodegradation rate and good hydrophilicity, compression, resilience, and porosity than the non-crosslinked (NC) groups. The minimum inhibitory concentration (MIC) of AgNPs/GQDs presented some bactericidal effects against Gram-positive and Gram-negative bacteria. The cytotoxicity tests on bilayer scaffolds demonstrated good cell viability for human epidermal keratinocytes (HEKs) and human dermal fibroblasts (HDFs). Therefore, the Na-CMC bilayer scaffold could be a potential candidate for future diabetic wound care.

Vitamin A-loaded decellularized kidney capsule promoted wound healing in rat

Tissue regeneration in many skin defects is progressing with new treatments in recent years. Tissue engineering with the use of scaffolds offers more versatile and faster solutions in treatment. Extracellular matrix (ECM) and its three-dimensional (3D) network structure as a biological bond by imitating the tissue microstructure has been used for tissue repair, which can answer many existing challenges. Vitamin A, which comes in several forms such as retinols, retinals, and retinoic acids, is a necessary vitamin that is crucial for wound healing. In this research, sheep kidney capsule tissue decellularized with sodium dodecyl sulfate (SDS) containing different doses of vitamin A has been used as an ECM in skin tissue engineering. The above scaffold was evaluated in terms of properties such as biocompatibility, analysis of mechanical properties, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), hydrophilicity, antibacterial, and cell adhesion. The findings reported suitable properties for wound dressing, especially at a dose of 15,000 U/ml vitamin A for this scaffold. Then, the above scaffold was evaluated on the full-thickness wound model in rat, which showed good wound contraction, and increased VEGF factor. It showed a decrease in IL-1β level. Therefore, the use of the above-mentioned decellularized scaffold in combination with medicinal agents effective in wound healing can be introduced for further pre-clinical studies.

An in vitro and in vivo study of electrospun polyvinyl alcohol/chitosan/sildenafil citrate mat on 3D-printed polycaprolactone membrane as a double layer wound dressing

Double-layer dermal substitutes (DS) generally provide more effective therapeutic outcomes than single-layer substitutes. The architectural design of DS incorporates an outer layer to protect against bacterial invasions and maintain wound hydration, thereby reducing the risk of infection and the frequency of dressing changes. Moreover, the outer layer is a mechanical support for the wound, preventing undue tension in the affected area. A 3D-printed polycaprolactone (PCL) membrane was utilized as the outer layer to fabricate DS wound dressing. Simultaneously, a polyvinyl alcohol/chitosan/sildenafil citrate (PVA/CS/SC) scaffold was electrospun onto the PCL membrane to facilitate cellular adhesion and proliferation. Scanning electron microscopy (SEM) analysis of the PCL filaments revealed a consistent cross-sectional surface and structure, with an average diameter of 562.72 ± 29.15 μm. SEM results also demonstrated uniform morphology and beadless structure for the PVA/CS/SC scaffold, with an average fiber diameter of 366.77 ± 1.81 nm for PVA/CS. The addition of SC led to an increase in fiber diameter while resulting in a reduction in tensile strength. However, drug release analysis indicated that the SC release from the sample can last up to 72 h. Animal experimentation confirmed that DS wound dressing positively accelerated wound closure and collagen deposition in the Wistar rat skin wound model.

Cobalt/Bioglass Nanoparticles Enhanced Dermal Regeneration in a 3-Layered Electrospun Scaffold

Purpose

Due to the multilayered structure of the skin tissue, the architecture of its engineered scaffolds needs to be improved. In the present study, 45s5 bioglass nanoparticles were selected to induce fibroblast proliferation and their protein secretion, although cobalt ions were added to increase their potency.

Methods

A 3-layer scaffold was designed as polyurethane (PU) - polycaprolactone (PCL)/ collagen/nanoparticles-PCL/collagen. The scaffolds examined by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), tensile, surface hydrophilicity and weight loss. Biological tests were performed to assess cell survival, adhesion and the pattern of gene expression.

Results

The mechanical assay showed the highest young modulus for the scaffold with the doped nanoparticles and the water contact angle of this scaffold after chemical crosslinking of collagen was reduced to 52.34±7.7°. In both assessments, the values were statistically compared to other groups. The weight loss of the corresponding scaffold was the highest value of 82.35±4.3 % due to the alkaline effect of metal ions and indicated significant relations in contrast to the scaffold with non-doped particles and bare one (P value<0.05). Moreover, better cell expansion, greater cell confluence and a lower degree of toxicity were confirmed. The up-regulation of TGF β1 and VEGF genes introduced this scaffold as a better model for the fibroblasts commitment to a new skin tissue among bare and nondoped scaffold (P value<0.05).

Conclusion

The 3-layered scaffold which is loaded with cobalt ions-bonded bioglass nanoparticles, is a better substrate for the culture of the fibroblasts.

Accelerated wound healing with resveratrol-loaded decellularized pericardium in mice model

One of the key objectives of regenerative medicine is the design of skin tissue engineering scaffolds to promote wound healing. These scaffolds provide a fresh viewpoint on skin injury repair by emulating body tissues in their structure. A suitable platform for cellular processes can be provided by natural scaffolds made from decellularized tissues while retaining the primary components. Resveratrol (RES), which has qualities like angiogenesis, antioxidant, antibacterial, and anti-inflammatory, is also useful in the healing of wounds. In this investigation, RES-loaded decellularized sheep pericardium scaffolds were created and tested on full-thickness wounds in a mouse model. According to the in vivo findings, the groups in which the wound was treated with decellularized pericardium (DP) had better wound healing than the control group and showed more production of angiogenic and anti-inflammatory substances. The secretion of these factors was greater in RES-loaded decellularized pericardium (DP-RES) than in the scaffold without RES, and the macroscopic and histological data supported this. Therefore, the use of decellularization scaffolds with substances like RES for the regeneration of skin wounds can be further researched and evaluated in the preclinical stages.

Fabrication and characterization of an antibacterial chitosan-coated allantoin-loaded NaCMC/SA skin scaffold for wound healing applications

The field of tissue engineering has recently emerged as one of the most promising approaches to address the limitations of conventional tissue replacements for severe injuries. This study introduces a chitosan-coated porous skin scaffold based on sodium carboxymethyl cellulose (NaCMC) and sodium alginate (SA) hydrogels, incorporating allantoin (AL) as an antibacterial agent. The NaCMC/SA hydrogel was cross-linked with epichlorohydrin (ECH) and freeze-dried to obtain a three-dimensional porous structure. The coated and non-coated scaffolds underwent comprehensive evaluation and characterization through various in-vitro analyses, including SEM imaging, swelling, degradation, and mechanical assessments. Furthermore, the scaffolds were studied regarding their allantoin (AL) release profiles, antibacterial properties, cell viability, and cell adhesion. The in-vitro analyses revealed that adding a chitosan (CS) coating and allantoin (AL) to the NaCMC/SA hydrogel significantly improved the scaffolds' antibacterial properties and cell viability. It was observed that the NaCMC:SA ratio and ECH concentration influenced the swelling capacity, biodegradation, drug release profile, and mechanical properties of the scaffolds. Samples with higher NaCMC content exhibited enhanced swelling capacity, more controlled allantoin (AL) release, and improved mechanical strength. Furthermore, the in-vivo results demonstrated that the proposed skin scaffold exhibited satisfactory biocompatibility and supported cell viability during wound healing in Wistar rats, highlighting its potential for clinical applications.

3D-Printed Collagen-Nanocellulose Hybrid Bioscaffolds with Tailored Properties for Tissue Engineering Applications

Hybrid collagen (Coll) bioscaffolds have emerged as a promising solution for tissue engineering (TE) and regenerative medicine. These innovative bioscaffolds combine the beneficial properties of Coll, an important structural protein of the extracellular matrix, with various other biomaterials to create platforms for long-term cell growth and tissue formation. The integration or cross-linking of Coll with other biomaterials increases mechanical strength and stability and introduces tailored biochemical and physical factors that mimic the natural tissue microenvironment. This work reports on the fabrication of chemically cross-linked hybrid bioscaffolds with enhanced properties from the combination of Coll, nanofibrillated cellulose (NFC), carboxymethylcellulose (CMC), and citric acid (CA). The bioscaffolds were prepared by 3D printing ink containing Coll-NFC-CMC-CA followed by freeze-drying, dehydrothermal treatment, and neutralization. Cross-linking through the formation of ester bonds between the polymers and CA in the bioscaffolds was achieved by exposing the bioscaffolds to elevated temperatures in the dry state. The morphology, pores/porosity, chemical composition, structure, thermal behavior, swelling, degradation, and mechanical properties of the bioscaffolds in the dry and wet states were investigated as a function of Coll concentration. The bioscaffolds showed no cytotoxicity to MG-63 human bone osteosarcoma cells as tested by different assays measuring different end points. Overall, the presented hybrid Coll bioscaffolds offer a unique combination of biocompatibility, stability, and structural support, making them valuable tools for TE.

Biomimetic Bilayered Scaffolds for Tissue Engineering: From Current Design Strategies to Medical Applications

Tissue damage due to cancer, congenital anomalies, and injuries needs new efficient treatments that allow tissue regeneration. In this context, tissue engineering shows a great potential to restore the native architecture and function of damaged tissues, by combining cells with specific scaffolds. Scaffolds made of natural and/or synthetic polymers and sometimes ceramics play a key role in guiding cell growth and formation of the new tissues. Monolayered scaffolds, which consist of uniform material structure, are reported as not being sufficient to mimic complex biological environment of the tissues. Osteochondral, cutaneous, vascular, and many other tissues all have multilayered structures, therefore multilayered scaffolds seem more advantageous to regenerate these tissues. In this review, recent advances in bilayered scaffolds design applied to regeneration of vascular, bone, cartilage, skin, periodontal, urinary bladder, and tracheal tissues are focused on. After a short introduction on tissue anatomy, composition and fabrication techniques of bilayered scaffolds are explained. Then, experimental results obtained in vitro and in vivo are described, and their limitations are given. Finally, difficulties in scaling up production of bilayer scaffolds and reaching the stage of clinical studies are discussed when multiple scaffold components are used.

Accelular nanofibrous bilayer scaffold intrapenetrated with polydopamine network and implemented into a full-thickness wound of a white-pig model affects inflammation and healing process

Treatment of complete loss of skin thickness requires expensive cellular materials and limited skin grafts used as temporary coverage. This paper presents an acellular bilayer scaffold modified with polydopamine (PDA), which is designed to mimic a missing dermis and a basement membrane (BM). The alternate dermis is made from freeze-dried collagen and chitosan (Coll/Chit) or collagen and a calcium salt of oxidized cellulose (Coll/CaOC). Alternate BM is made from electrospun gelatin (Gel), polycaprolactone (PCL), and CaOC. Morphological and mechanical analyzes have shown that PDA significantly improved the elasticity and strength of collagen microfibrils, which favorably affected swelling capacity and porosity. PDA significantly supported and maintained metabolic activity, proliferation, and viability of the murine fibroblast cell lines. The in vivo experiment carried out in a domestic Large white pig model resulted in the expression of pro-inflammatory cytokines in the first 1-2 weeks, giving the idea that PDA and/or CaOC trigger the early stages of inflammation. Otherwise, in later stages, PDA caused a reduction in inflammation with the expression of the anti-inflammatory molecule IL10 and the transforming growth factor β (TGFβ1), which could support the formation of fibroblasts. Similarities in treatment with native porcine skin suggested that the bilayer can be used as an implant for full-thickness skin wounds and thus eliminate the use of skin grafts.

Stem cell and tissue engineering approaches in pressure ulcer treatment

CONTEXT

Pressure ulcers or injuries, arise from ischemic damage to soft tissues induced by unrelieved pressure over a bony prominence. They are usually difficult to treat with standard medical therapy and often they recur. In the search for better treatment options, promising alternative forms of treatment are today emerging. Within the field of regenerative medicine, ongoing research on advanced therapies seeks to develop medicinal products based on gene therapy, somatic cell therapy, tissue-engineering and combinations of these.

OBJECTIVE

The main objective is to perform an overview of experimental and clinical developments in somatic cell therapy and tissue engineering targeting the treatment of pressure injuries.

METHODS

Searching terms as "PRESSURE ULCER", "STEM CELL THERAPY", "TISSUE ENGINEERING" or "WOUND HEALING" were used in combination or alone, including publications refered to basic and clinical research and focusing on articles showing results obtained in a clinical context. A total of 80 references are cited, including 23 references published in the 3 last years.

RESULTS

The results suggest that this form of treatment could be an interesting option in patients with difficult-to-treat ulcers as spinal cord injury patients.

CONCLUSION

This field of regenerative medicine is very broad and further research is warranted.

Chondroitin sulfate-based composites: a tour d'horizon of their biomedical applications

Chondroitin sulfate (CS), a natural anionic mucopolysaccharide, belonging to the glycosaminoglycan family, acts as the primary element of the extracellular matrix (ECM) of diverse organisms. It comprises repeating units of disaccharides possessing β-1,3-linked N-acetyl galactosamine (GalNAc), and β-1,4-linked D-glucuronic acid (GlcA), and exhibits antitumor, anti-inflammatory, anti-coagulant, anti-oxidant, and anti-thrombogenic activities. It is a naturally acquired bio-macromolecule with beneficial properties, such as biocompatibility, biodegradability, and immensely low toxicity, making it the center of attention in developing biomaterials for various biomedical applications. The authors have discussed the structure, unique properties, and extraction source of CS in the initial section of this review. Further, the current investigations on applications of CS-based composites in various biomedical fields, focusing on delivering active pharmaceutical compounds, tissue engineering, and wound healing, are discussed critically. In addition, the manuscript throws light on preclinical and clinical studies associated with CS composites. A short section on Chondroitinase ABC has also been canvassed. Finally, this review emphasizes the current challenges and prospects of CS in various biomedical fields.

Novel strategies for designing regenerative skin products for accelerated wound healing

Healthy skin protects from pathogens, water loss, ultraviolet rays, and also maintains homeostasis conditions along with sensory perceptions in normal circumstances. Skin wound healing mechanism is a multi-phased biodynamic process that ultimately triggers intercellular and intracellular mechanisms. Failure to implement the normal and effective healing process may result in chronic injuries and aberrant scarring. Chronic wounds lead to substantial rising healthcare expenditure, and innovative methods to diagnose and control severe consequences are urgently needed. Skin tissue engineering (STE) has achieved several therapeutic accomplishments during the last few decades, demonstrating tremendous development. The engineered skin substitutes provide instant coverage for extensive wounds and facilitate the prevention of microbial infections and fluid loss; furthermore, they help in fighting inflammation and allow rapid neo-tissue formation. The current review primarily focused on the wound recovery and restoration process and the current conditions of STE with various advancements and complexities associated with different strategies such as cell sources, biopolymers, innovative fabrication techniques, and growth factors delivery systems.

A Comprehensive Review on Collagen Type I Development of Biomaterials for Tissue Engineering: From Biosynthesis to Bioscaffold

Collagen is the most abundant structural protein found in humans and mammals, particularly in the extracellular matrix (ECM). Its primary function is to hold the body together. The collagen superfamily of proteins includes over 20 types that have been identified. Yet, collagen type I is the major component in many tissues and can be extracted as a natural biomaterial for various medical and biological purposes. Collagen has multiple advantageous characteristics, including varied sources, biocompatibility, sustainability, low immunogenicity, porosity, and biodegradability. As such, collagen-type-I-based bioscaffolds have been widely used in tissue engineering. Biomaterials based on collagen type I can also be modified to improve their functions, such as by crosslinking to strengthen the mechanical property or adding biochemical factors to enhance their biological activity. This review discusses the complexities of collagen type I structure, biosynthesis, sources for collagen derivatives, methods of isolation and purification, physicochemical characteristics, and the current development of collagen-type-I-based scaffolds in tissue engineering applications. The advancement of additional novel tissue engineered bioproducts with refined techniques and continuous biomaterial augmentation is facilitated by understanding the conventional design and application of biomaterials based on collagen type I.

Bilayer Hydrogels for Wound Dressing and Tissue Engineering

A large number of different skin diseases such as hits, acute, and chronic wounds dictate the search for alternative and effective treatment options. The wound healing process requires a complex approach, the key step of which is the choice of a dressing with controlled properties. Hydrogel-based scaffolds can serve as a unique class of wound dressings. Presented on the commercial market, hydrogel wound dressings are not found among proposals for specific cases and have a number of disadvantages—toxicity, allergenicity, and mechanical instability. Bilayer dressings are attracting great attention, which can be combined with multifunctional properties, high criteria for an ideal wound dressing (antimicrobial properties, adhesion and hemostasis, anti-inflammatory and antioxidant effects), drug delivery, self-healing, stimulus manifestation, and conductivity, depending on the preparation and purpose. In addition, advances in stem cell biology and biomaterials have enabled the design of hydrogel materials for skin tissue engineering. To improve the heterogeneity of the cell environment, it is possible to use two-layer functional gradient hydrogels. This review summarizes the methods and application advantages of bilayer dressings in wound treatment and skin tissue regeneration. Bilayered hydrogels based on natural as well as synthetic polymers are presented. The results of the in vitro and in vivo experiments and drug release are also discussed.

Self-Assembled Hydrogel Microparticle-Based Tooth-Germ Organoids

Here, we describe the characterization of tooth-germ organoids, three-dimensional (3D) constructs cultured in vitro with the potential to develop into living teeth. To date, the methods used to successfully create tooth organoids capable of forming functional teeth have been quite limited. Recently, hydrogel microparticles (HMP) have demonstrated utility in tissue repair and regeneration based on their useful characteristics, including their scaffolding ability, effective cell and drug delivery, their ability to mimic the natural tissue extracellular matrix, and their injectability. These outstanding properties led us to investigate the utility of using HMPs (average diameter: 158 ± 32 µm) derived from methacrylated gelatin (GelMA) (degree of substitution: 100%) to create tooth organoids. The tooth organoids were created by seeding human dental pulp stem cells (hDPSCs) and porcine dental epithelial cells (pDE) onto the HMPs, which provided an extensive surface area for the cells to effectively attach and proliferate. Interestingly, the cell-seeded HMPs cultured on low-attachment tissue culture plates with gentle rocking self-assembled into organoids, within which the cells maintained their viability and morphology throughout the incubation period. The self-assembled organoids reached a volume of ~50 mm3 within two weeks of the in vitro tissue culture. The co-cultured hDPSC-HMP and pDE-HMP structures effectively attached to each other without any externally applied forces. The presence of polarized, differentiated dental cells in these composite tooth-bud organoids demonstrated the potential of self-assembled dental cell HMPs to form tooth-bud organoid-like structures for potential applications in tooth regeneration strategies.

An Overview of Cellulose Derivatives-Based Dressings for Wound-Healing Management

Presently, notwithstanding the progress regarding wound-healing management, the treatment of the majority of skin lesions still represents a serious challenge for biomedical and pharmaceutical industries. Thus, the attention of the researchers has turned to the development of novel materials based on cellulose derivatives. Cellulose derivatives are semi-synthetic biopolymers, which exhibit high solubility in water and represent an advantageous alternative to water-insoluble cellulose. These biopolymers possess excellent properties, such as biocompatibility, biodegradability, sustainability, non-toxicity, non-immunogenicity, thermo-gelling behavior, mechanical strength, abundance, low costs, antibacterial effect, and high hydrophilicity. They have an efficient ability to absorb and retain a large quantity of wound exudates in the interstitial sites of their networks and can maintain optimal local moisture. Cellulose derivatives also represent a proper scaffold to incorporate various bioactive agents with beneficial therapeutic effects on skin tissue restoration. Due to these suitable and versatile characteristics, cellulose derivatives are attractive and captivating materials for wound-healing applications. This review presents an extensive overview of recent research regarding promising cellulose derivatives-based materials for the development of multiple biomedical and pharmaceutical applications, such as wound dressings, drug delivery devices, and tissue engineering.

Benefit of coupling heparin to crosslinked collagen I/III scaffolds for human dermal fibroblast subpopulations' tissue growth

Currently, there is a lack of models representing the skin dermal heterogeneity for relevant research and skin engineering applications. This is the first study reporting production of dermal equivalents reproducing features of papillary and reticular dermal compartments. Inspired from our current knowledge on the architecture and composition differences between the papillary and reticular dermis, we evaluated different collagen-based porous materials to serve as scaffolds for the three-dimensional expansion of freshly isolated papillary and/or reticular fibroblasts. The scaffolds, composed of either collagen I or collagen I and III mixtures, were prepared by lyophilization. Pore size and hydrolytic stability were controlled by crosslinking with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) or EDC/NHS with covalently bound heparin. The evaluation of the resultant "papillary" and "reticular" dermal equivalents was based on the analysis of characteristic features of each dermal compartment, such as cell density and deposition of newly synthetized extracellular matrix components in histological sections. Crosslinking supported cell growth during dermal tissue formation independent on the fibroblast subpopulation. The presence of collagen III seemed to have some positive but non-specific effect only on the maintenance of the mechanical strength of the scaffolds during dermal formation. Histological analyses demonstrated a significant and specific effect of heparin on generating dermal equivalents reproducing the respective higher papillary than reticular cell densities and supporting distinct extracellular matrix components deposition (three to five times more carbohydrate material deposited by papillary fibroblasts in all scaffolds containing heparin, while higher collagen production was observed only in the presence of heparin).

Photo-crosslinked hyaluronic acid hydrogel as a biomimic extracellular matrix to recapitulate in vivo features of breast cancer cells

2D cell culture is widely utilized to develop anti-cancer drugs and to explore the mechanisms of cancer tumorigenesis and development. However, the findings obtained from 2D culture often fail to provide guidance for clinical tumor treatments since it cannot precisely replicate the features of real tumors. 3D tumor models capable of recapitulating native tumor microenvironments have been proved to be a promising alternative technique. Herein, we constructed a breast tumor model from novel hyaluronic acid (HA) hydrogel which was prepared through photocrosslinking of methacrylated HA. The hydrogel was used as a biomimetic extracellular matrix to incubate MCF-7 cells. It was found that methacrylation degree had great effects on hydrogel's microstructure, mechanical performances, and liquid-absorbing and degradation abilities. Optimized hydrogel exhibited highly porous morphology, high equilibrium swelling ratio, suitable mechanical properties, and hyaluronidase-responsive degradation behavior. The results demonstrated that the HA hydrogel facilitated MCF-7 cell proliferation and growth in an aggregation manner. Furthermore, 3D-cultured MCF-7 cells not only up-regulated the expression of VEGF, bFGF and interleukin-8 but exhibited greater invasion and tumorigenesis capabilities compared with 2D-cultured cells. Therefore, the HA hydrogel is a reliable substitute for tumor model construction.

Acellular Scaffolds as Innovative Biomaterial Platforms for the Management of Diabetic Wounds

Diabetic wound (DW) is one of the leading complications of patients having a long history of uncontrolled diabetes. Moreover, it also imposes an economic burden on people suffering from wounds to manage the treatment. The major impending factors in the treatment of DW are infection, prolonged inflammation and decreased oxygen levels. Since these non-healing wounds are associated with an extended recovery period, the existing therapies provide treatment for a limited period only. The areas covered in this review are general sequential events of wound healing along with DW's pathophysiology, the origin of DW and success, as well as limitations of existing therapies. This systematic review's significant aspect is to highlight the fabrication, characterization and applications of various acellular scaffolds used to heal DW. In addition to that, cellular scaffolds are also described to a limited extent.

Influence of Charge and Heat on the Mechanical Properties of Scaffolds from Ionic Complexation of Chitosan and Carboxymethyl Cellulose

As one of the most abundant, multifunctional biological polymers, polysaccharides are considered promising materials to prepare tissue engineering scaffolds. When properly designed, wetted porous scaffolds can have biomechanics similar to living tissue and provide suitable fluid transport, both of which are key features for in vitro and in vivo tissue growth. They can further mimic the components and function of glycosaminoglycans found in the extracellular matrix of tissues. In this study, we investigate scaffolds formed by charge complexation between anionic carboxymethyl cellulose and cationic protonated chitosan under well-controlled conditions. Freeze-drying and dehydrothermal heat treatment were then used to obtain porous materials with exceptional, unprecendent mechanical properties and dimensional long-term stability in cell growth media. We investigated how complexation conditions, charge ratio, and heat treatment significantly influence the resulting fluid uptake and biomechanics. Surprisingly, materials with high compressive strength, high elastic modulus, and significant shape recovery are obtained under certain conditions. We address this mostly to a balanced charge ratio and the formation of covalent amide bonds between the polymers without the use of additional cross-linkers. The scaffolds promoted clustered cell adhesion and showed no cytotoxic effects as assessed by cell viability assay and live/dead staining with human adipose tissue-derived mesenchymal stem cells. We suggest that similar scaffolds or biomaterials comprising other polysaccharides have a large potential for cartilage tissue engineering and that elucidating the reason for the observed peculiar biomechanics can stimulate further research.

Key advances of carboxymethyl cellulose in tissue engineering & 3D bioprinting applications

Carboxymethyl cellulose (CMC) is a water-soluble derivative of cellulose and a major type of cellulose ether prepared by the chemical attack of alkylating reagents on the activated non-crystalline regions of cellulose. It is the first FDA approved cellulose derivative which can be targeted for desired chemical modifications. In this review, the properties along with current advances in the physical and chemical modifications of CMC are discussed. Further, CMC and modified CMC could be engineered to fabricate scaffolds for tissue engineering applications. In recent times, CMC and its derivatives have been developed as smart bioinks for 3D bioprinting applications. From these perspectives, the applications of CMC in tissue engineering and current knowledge on peculiar features of CMC in 3D and 4D bioprinting applications are elaborated in detail. Lastly, future perspectives of CMC for wider applications in tissue engineering and 3D/4D bioprinting are highlighted.

Bioinks-materials used in printing cells in designed 3D forms

Use of materials to activate non-functional or damaged organs and tissues goes back to early ages. The first materials used for this purpose were metals, and in time, novel materials such as ceramics, polymers and composites were introduced to the field to serve in medical applications. In the last decade, the advances in material sciences, cell biology, technology and engineering made 3D printing of living tissues or organ models in the designed structure and geometry possible by using cells alone or together with hydrogels through additive manufacturing. This review aims to give a brief information about the chemical structures and properties of bioink materials and their applications in the production of 3D tissue constructs.

Assessment of properties, applications and limitations of scaffolds based on cellulose and its derivatives for cartilage tissue engineering: A review

Cartilage is a connective tissue, which is made up of ~80% of water. It is alymphatic, aneural and avascular with only one type of cells present, chondrocytes. They constitute about 1-5% of the entire cartilage tissue. It has a very limited capacity for spontaneous repair. Articular cartilage defects are quite common due to trauma, injury or aging and these defects eventually lead to osteoarthritis, affecting the daily activities. Tissue engineering (TE) is a promising strategy for the regeneration of articular cartilage when compared to the existing invasive treatment strategies. Cellulose is the most abundant natural polymer and has desirable properties for the development of a scaffold, which can be used for the regeneration of cartilage. This review discusses about (i) the basic science behind cartilage TE and the study of cellulose properties that can be exploited for the construction of the engineered scaffold with desired properties for cartilage tissue regeneration, (ii) about the requirement of scaffolds properties, fabrication mechanisms and assessment of cellulose based scaffolds, (iii) details about the modification of cellulose surface by employing various chemical approaches for the production of cellulose derivatives with enhanced characteristics and (iv) limitations and future research prospects of cartilage TE.

Cellulose/Collagen Dressings for Diabetic Foot Ulcer: A Review

Diabetic foot ulcer (DFU) is currently a global concern and it requires urgent attention, as the cost allocation by the government for DFU increases every year. This review was performed to provide scientific evidence on the advanced biomaterials that can be utilised as a first-line treatment for DFU patients. Cellulose/collagen dressings have a biological property on non-healing wounds, such as DFU. This review aims to analyse scientific-based evidence of cellulose/collagen dressing for DFU. It has been proven that the healing rate of cellulose/collagen dressing for DFU patients demonstrated a significant improvement in wound closure as compared to current standard or conventional dressings. It has been scientifically proven that cellulose/collagen dressing provides a positive effect on non-healing DFU. There is a high tendency for cellulose/collagen dressing to be used, as it highly promotes angiogenesis with a rapid re-epithelisation rate that has been proven effective in clinical trials.

New Developments in Medical Applications of Hybrid Hydrogels Containing Natural Polymers

New trends in biomedical applications of the hybrid polymeric hydrogels, obtained by combining natural polymers with synthetic ones, have been reviewed. Homopolysaccharides, heteropolysaccharides, as well as polypeptides, proteins and nucleic acids, are presented from the point of view of their ability to form hydrogels with synthetic polymers, the preparation procedures for polymeric organic hybrid hydrogels, general physico-chemical properties and main biomedical applications (i.e., tissue engineering, wound dressing, drug delivery, etc.).

Physically Cross-Linked Gels of PVA with Natural Polymers as Matrices for Manuka Honey Release in Wound-Care Applications

Manuka honey is a well-known natural material from New Zealand, considered to have properties beneficial for burn treatment. Gels created from polyvinyl alcohol (PVA) blended with natural polymers are potential burn-care dressings, combining biocompatibility with high fluid uptake. Controlled release of manuka honey from such materials is a possible strategy for improving burn healing. This work aimed to produce polyvinyl alcohol (PVA), PVA⁻sodium carboxymethylcellulose (PVA-CMC), PVA⁻gelatin (PVA-G), and PVA⁻starch (PVA-S) cryogels infused with honey and to characterize these materials physicochemically, morphologically, and thermally, followed by in vitro analysis of swelling capacity, degradation/weight loss, honey delivery kinetics, and possible activity against Staphylococcus aureus. The addition of honey to PVA led to many PVA crystals with defects, while PVA⁻starch⁻honey and PVA⁻sodium carboxymethylcellulose⁻honey (PVA-CMC-H) formed amorphous gels. PVA-CMC presented the highest swelling degree of all. PVA-CMC-H and PVA⁻gelatin⁻honey presented the highest swelling capacities of the honey-laden samples. Weight loss/degradation was significantly higher for samples containing honey. Layers submitted to more freeze⁻thawing cycles were less porous in SEM images. With the honey concentration used, samples did not inhibit S. aureus, but pure manuka honey was bactericidal and dilutions superior to 25% honey were bacteriostatic, indicating the need for higher concentrations to be more effective.