Scaffolds For Soft Tissue Engineering Research Articles

Multicellular Layered Nanofibrous Poly(Oligo Ethylene Glycol Methacrylate) (POEGMA)-Based Hydrogel Scaffolds via Reactive Cell Electrospinning.

While hydrogels are demonstrated to be effective scaffolds for soft tissue engineering, existing fabrication techniques pose limitations in terms of being able to reproduce both the micro/nanofibrous structures of native extracellular matrix as well as the spatial arrangement of different cell types inherent of more complex tissues. Herein, a reactive cell electrospinning strategy is described using hydrazide and aldehyde-functionalized poly(oligoethylene glycol methacrylate) precursor polymers that can create nanofibrous hydrogel scaffolds with controllable local cell gradients using a sequential all-aqueous process that does not require additives or external energy. Cells can be encapsulated directly during the fabrication process in different layers within the scaffold, enabling localized segregation of different cell types within the structures without compromising their capacity to proliferate (≈4-fold increase in cell density over a 14 day incubation period). This sequential reactive electrospinning approach thus offers promise to generate coculture fibrous hydrogel networks in which both the nanoscale architecture and the cell distribution can be controlled, as it is essential to recreate more complex types of tissues.

Optimizing phenol-modified hyaluronic acid for designing shape-maintaining biofabricated hydrogel scaffolds in soft tissue engineering

In this study, we developed a well-printable biomaterial ink for 3D printing of shape-maintaining hydrogel scaffolds. The hydrogel base comprised tyramine-modified hyaluronic acid (HA-Tyr) and gelatin methacrylate (GelMA) and was dually cross-linked. Using the Box-Behnken design, we explored how varying the ink composition affected fiber formation and shape preservation. By adjusting the polymer ratios, we produced a stable hydrogel with varying responses, from a viscous liquid to a thick gel, and optimized 3D scaffolds that were structurally stable both during and after printing, offering precision and flexibility. Our ink exhibited shear-thinning behavior and high swelling capacity, as well as ECM-like characteristics and biocompatibility, making it an ideal candidate for soft tissues matrices with storage modulus of around 300 Pa. Animal trials and CAM assays confirmed its biocompatibility and integration with host tissue.

Fabrication and characterization of methylprednisolone-loaded polylactic acid/hyaluronic acid nanofibrous scaffold for soft tissue engineering

Previous in vitro and in vivo studies have indicated that tissue engineering scaffolds, including Schwann cells, may improve axonal regeneration, particularly in combination with Methylprednisolone as an influential neuroprotective factor. The primary aim of this study was to design composite electrospun scaffolds based on polylactic acid (PLA)/hyaluronic acid (HA) containing various percentages (0.05–2% (w/v)) of Methylprednisolone (MP) with suitable mechanical and chemical properties for soft tissue especially to promote nerve growth. For the first time, MP was implicated in a PLA/HA nanofibrous and its effect on fiber’s properties was scrutinized as a candidate for nerve tissue engineering. In addition, morphology, chemical bonding, wettability, and degradation of the scaffolds were examined to evaluate their performance. The results showed the PLA/HA scaffolds had suitable morphological, physicochemical, and mechanical properties for nerve regeneration. Also, various percentages of MP were evaluated through physiochemical assay, drug release profile, and biological assays to find an optimum level of drug. These scaffolds may improve the growth and viability of Schwann cells. Results showed that composite scaffolds containing 0.5 w/v MP had lower cytotoxicity and higher biocompatibility.

3D printing and properties of cellulose nanofibrils-reinforced quince seed mucilage bio-inks

Plant-based hydrogels have attracted great attention in biomedical fields since they are biocompatible and based on natural, sustainable, cost-effective, and widely accessible sources. Here, we introduced new viscoelastic bio-inks composed of quince seed mucilage and cellulose nanofibrils (QSM/CNF) easily extruded into 3D lattice structures through direct ink writing in ambient conditions. The QSM/CNF inks enabled precise control on printing fidelity where CNF endowed objects with shape stability after freeze-drying and with suitable porosity, water uptake capacity, and mechanical strength. The compressive and elastic moduli of samples produced at the highest CNF content were both increased by ~100% (from 5.1 ± 0.2 kPa and 32 ± 1 kPa to 10.7 ± 0.5 and 64 ± 2 kPa, respectively). These values ideally matched those reported for soft tissues; accordingly, the cell compatibility of the printed samples was evaluated against HepG2 cells (human liver cancer). The results confirmed the 3D hydrogels as being non-cytotoxic and suitable to support attachment, survival, and proliferation of the cells. All in all, the newly developed inks allowed sustainable 3D bio-hydrogels fitting the requirements as scaffolds for soft tissue engineering.

Human Hair Keratin Composite Scaffold: Characterisation and Biocompatibility Study on NIH 3T3 Fibroblast Cells.

The aim of this study was to transform human hair keratin waste into a scaffold for soft tissue engineering to heal wounds. The keratin was extracted using the Shindai method. Keratin and polyvinyl alcohol (PVA) was cross-linked with alginate dialdehyde and converted into a scaffold by the freeze-drying method using gentamycin sulphate (GS) as a model drug. The scaffold was subjected to Fourier transform infrared spectra (FTIR), swelling index, porosity, water absorption, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), drug release, and cell viability (MTT) analysis. The scaffold was tested for keratinocyte growth using the murine fibroblast cell line (NIH 3T3 cells). The outcome from the keratin had a molecular weight band between 52–38 kDa in SDS-PAGE (Sodium dodecylsulfate-Polyacrylamide gel electrophoresis). A porous scaffold was capable of water absorption (73.64 ± 14.29%), swelling ability (68.93 ± 1.33%), and the release of GS shown as 97.45 ± 4.57 and 93.86 ± 5.22 of 1:4 and 1:3 scaffolds at 16 h. The physicochemical evaluation revealed that the prepared scaffold exhibits the proper structural integrity: partially crystalline with a strong thermal property. The scaffold demonstrated better cell viability against the murine fibroblast cell line (NIH 3T3 cells). In conclusion, we found that the prepared composite scaffold (1:4) can be used for wound healing applications.

Mechanical and biological performance of rainbow trout collagen‐boron nitride nanocomposite scaffolds for soft tissue engineering

AbstractWe aim to investigate the potential of collagen extracted from rainbow trout for tissue engineering applications. In this regard, nanocomposite scaffolds based on the extracted collagen reinforced with various concentrations of boron nitride (BN) nanoparticles (0, 3, 6, 9, and 12 wt%) were developed. In addition, the role of various concentrations of BN nanoparticles and two‐step cross‐linking process on the physical and chemical properties of nanocomposite scaffolds were investigated. Our results demonstrated the isolation of Type I collagen with excellent thermal stability but with some structural and chemical differences compared to other sources. The synergic role of BN nanoparticles and two‐step cross‐linking process resulted in a noticeable improvement in the mechanical properties of collagen‐BN scaffolds. Noticeably, incorporation of 6 wt% BN along with a two‐step cross‐linking process significantly increased the compressive strength (9.5 times) and elastic modulus (four times) of the collagen scaffold. Besides, nanocomposite scaffolds significantly improved proliferation and spreading of MG‐63 cell line, confirming their biocompatibility. The results suggested that the incorporation of BN nanoparticles along with a two‐step cross‐linking process not only could promote the mechanical and thermal performances of collagen scaffolds, but also enhanced high cell viability, and proliferation supporting their potential in tissue engineering applications.

3D printing of Osage orange extract/Chitosan scaffolds for soft tissue engineering

In this study, three-dimensional tissue scaffolds were fabricated using a 3D printing process. Chitosan (CS) was used as a matrix polymer, and Osage orange extract (OGE) with different amounts was added as a bioactive material. The scaffolds were characterized by SEM, FTIR, tensile testing, antibacterial, and biocompatibility tests. The SEM images revealed that scaffolds had homogeneous morphology, and the size of the pores ranged from 160 µm to 270 µm. FTIR spectrum of the extracted Osage Orange confirmed the successful extraction of the Osage Orange. The OGE addition decreased the swelling capacity of the CS scaffold proportionally. Biocompatibility results proved the biostability properties of the scaffolds. According to the results, the antibacterial activity of the scaffolds against the Staphylococcus Aureus (S. aureus) and Enterococcus Faecalis (E. faecalis) should be provided after detailed optimization.

An investigation into influence of acetylated cellulose nanofibers on properties of PCL/Gelatin electrospun nanofibrous scaffold for soft tissue engineering

In this study, the effective role of incorporation of cellulose nanofibers (CNF) and modified acetylated cellulose nanofibers (ACNF) on mechanical, physical, and biological properties of poly (ε-caprolactone) (PCL)/gelatin (Gel) electrospun nanofibrous scaffold was individually investigated. It was noticed that mechanical and biological properties of the scaffolds were considerably affected by the filler type and content. Although, by addition of 2 wt% ACNF, the ultimate tensile strength (UTS) of the PCL/Gel was remarkably enhanced from 2.5 ± 0.1 MPa to 4.3 ± 0.1 MPa due to homogeneous dispersion of the ACNF, however, the degradation rate of PCL/Gel scaffold was reduced about 1.66 times. Moreover, the studies on the interactions between hybrid scaffolds and fibroblast cells revealed that the incorporation of ACNF into scaffold not only showed no cytotoxic, but also promoted cell proliferation. In conclusion, PCL/Gel nanocomposite scaffolds reinforced by ACNFs show an excellent potential as a promising candidate for soft tissue engineering applications.

PLGA Membranes Functionalized with Gelatin through Biomimetic Mussel-Inspired Strategy.

Electrospun membranes have been widely used as scaffolds for soft tissue engineering due to their extracellular matrix-like structure. A mussel-inspired coating approach based on 3,4-dihydroxy-DL-phenylalanine (DOPA) polymerization was proposed to graft gelatin (G) onto poly(lactic-co-glycolic) acid (PLGA) electrospun membranes. PolyDOPA coating allowed grafting of gelatin to PLGA fibers without affecting their bulk characteristics, such as molecular weight and thermal properties. PLGA electrospun membranes were dipped in a DOPA solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 7 h and then incubated in G solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 16 h. PLGA fibers had an average diameter of 1.37 ± 0.23 µm. Quartz crystal microbalance with dissipation technique (QCM-D) analysis was performed to monitor DOPA polymerization over time: after 7 h the amount of deposited polyDOPA was 71 ng/cm2. After polyDOPA surface functionalization, which was, also revealed by Raman spectroscopy, PLGA membranes maintained their fibrous morphology, however the fiber size and junction number increased. Successful functionalization with G was demonstrated by FTIR-ATR spectra, which showed the presence of G adsorption bands at 1653 cm−1 (Amide I) and 1544 cm−1 (Amide II) after G grafting, and by the Kaiser Test, which revealed a higher amount of amino groups for G functionalized membranes. Finally, the biocompatibility of the developed substrates and their ability to induce cell growth was assessed using Neonatal Normal Human Dermal Fibroblasts.

Crosslinked Hyaluronic Acid Gels with Blood-Derived Protein Components for Soft Tissue Regeneration.

Hyaluronic acid (HA) is an ideal initial material for preparing hydrogels, which may be used as scaffolds in soft tissue engineering based on their advantageous physical and biological properties. In this study, two crosslinking agents, divinyl sulfone (DVS) and butanediol diglycidyl ether, were used to investigate their effect on the properties of HA hydrogels. As HA hydrogels alone do not promote cell adhesion on the scaffold, fibrin and serum from platelet-rich fibrin (SPRF) were combined with the scaffold; the aim was to create a material intended to be used as soft tissue implant that facilitates new tissue formation, and degrades over time. The chemical changes were characterized and cell attachment capacity of the protein-containing gels was examined using human mesenchymal stem cells, and viability was assessed using live-dead staining. Fourier-transform infrared measurements revealed that linking fibrin into the gel was more effective than linking SPRF. The scaffolds were found to be able to support cell adherence onto the hydrogels, and the best result was achieved when HA was crosslinked with DVS and contained fibrin. The most promising derivative, 5% DVS-crosslinked fibrin-containing hydrogel, was injected subcutaneously into C57BL/6 mice for 12 weeks. The scaffold was proven to be biocompatible, remodeling, and vascularization occurred, while shape and integrity were maintained. Impact statement Fibrin was combined with crosslinked hyaluronic acid (HA) for regenerative application, the structure of the combination of crosslinked HA with blood-derived protein was analyzed and effective coating was proven. It was observed that the fibrin content led to better mesenchymal stem cell attachment in vitro. The compositions showed biocompatibility, connective tissue and vascularization took place when implanted in vivo. Thus, a biocompatible, injectable gel was produced, which is a potential candidate for soft tissue implantation.

Fabrication of guar gum-gelatin scaffold for soft tissue engineering

This study investigates the effect of G’, G” and G”/G’ (tan ∂) on the properties of freeze-dried scaffolds for tissue engineering. Guar gum (GG)-gelatin (GE) hydrogels were prepared with varying concentrations of GG, to achieve a wide range of G’ and G”. Rheological analysis was performed and then the hydrogels were freeze-dried to evaluate their porosity and structural integrity. Studies revealed that higher tan ∂ values resulted in weak scaffolds, while lower values resulted in hard scaffolds having structural deformities. Scaffolds desirable for soft tissue engineering had tan ∂ value of 0.88. The porosity and interconnectivity of the optimized scaffold were in range to enable efficient transport of nutrition and waste products. Physical parameters, like contact angle and surface roughness of the optimized scaffold were favourable for soft tissue engineering. Bioassay was performed by culturing human keratinocytes, which divulged excellent cell viability and proliferation even after fourteen days of culture.

Polymer-Based Scaffolds for Soft-Tissue Engineering.

Biomaterials have been used since ancient times. However, it was not until the late 1960s when their development prospered, increasing the research on them. In recent years, the study of biomaterials has focused mainly on tissue regeneration, requiring a biomaterial that can support cells during their growth and fulfill the function of the replaced tissue until its regeneration. These materials, called scaffolds, have been developed with a wide variety of materials and processes, with the polymer ones being the most advanced. For this reason, the need arises for a review that compiles the techniques most used in the development of polymer-based scaffolds. This review has focused on three of the most used techniques: freeze-drying, electrospinning and 3D printing, focusing on current and future trends. In addition, the advantages and disadvantages of each of them have been compared.

Soft Actuated Hybrid Hydrogel with Bioinspired Complexity to Control Mechanical Flexure Behavior for Tissue Engineering.

Hydrogels exhibit excellent properties that enable them as nanostructured scaffolds for soft tissue engineering. However, single-component hydrogels have significant limitations due to the low versatility of the single component. To achieve this goal, we have designed and characterized different multi-component hydrogels composed of gelatin, alginate, hydroxyapatite, and a protein (BSA and fibrinogen). First, we describe the surface morphology of the samples and the main characteristics of the physiological interplay by using fourier transform infrared (FT-IR), and confocal Raman microscopy. Then, their degradation and swelling were studied and mechanical properties were determined by rheology measurements. Experimental data were carefully collected and quantitatively analyzed by developing specific approaches and different theoretical models to determining the most important parameters. Finally, we determine how the nanoscale of the system influences its macroscopic properties and characterize the extent to which degree each component maintains its own functionality, demonstrating that with the optimal components, in the right proportion, multifunctional hydrogels can be developed.

Beta-sheet content significantly correlates with the biodegradation time of silk fibroin hydrogels showing a wide range of compressive modulus

Elasticity and biodegradability are required for hydrogel scaffolds in soft tissue engineering and vary among target tissues. To identify the unique effects of these properties on tissue regeneration, a factor that alters only one of these properties independent of the other is needed. Here, we evaluated various properties of 15 types of silk fibroin (SF) physical hydrogels with different SF concentrations and molecular weights, and found that the compressive modulus and biodegradability did not correlate with each other significantly. This suggested the possibility of a factor that affected only one of the properties. SF concentration and water content of the hydrogels changed both the compressive modulus and biodegradability simultaneously. In contrast, the β-sheet content in SF hydrogels correlated only with the biodegradation time significantly, suggesting that the β-sheet content may be used to study the effect of biodegradation time on tissue regeneration. In addition, an SF hydrogel was modified with a peptide derived from the β-sheet forming GAGAGS/Y repeated region in SF heavy-chain, resulting in no significant difference in the compressive modulus but a significantly delayed biodegradation time. These results suggest the potential for SF hydrogels as a group of materials with made-to-order elasticity and biodegradability for soft tissue engineering applications.

3D bioprinted alginate-gelatin based scaffolds for soft tissue engineering

Increase in the number of patients suffering from Osteoarthritis is prevalent nowadays and hence, there is need for tissue regeneration. Fabricating a 3D structure giving a better control mimicking the actual tissue properties, especially for osteo-chondral applications is a challenge due to several constraints (like suitable biomaterial for cell encapsulation, mimicking mechanical properties). Here, we mimic the natural process of tissue formation by encapsulating cells in an optimized 3D construct which improves mechanical properties by matrix secretion. We investigated different concentrations of Alginate-Gelatin ink and further characterized the optimized concentration. Behaviour of different infill percentage on the bioactivity and morphology of the scaffold was also investigated. For observing the behaviour of cells on different infill percentages within the scaffolds of same concentration, we used osteoblasts (MG63) cells. The optimized material concentration with the adequate infill showed printability, adequate viscosity, and increased swelling. Both, 20 and 25% infill within the Alginate-Gelatin scaffolds (2.5% w/v Alginate and 5% w/v Gelatin) resulted in higher viability and proliferation of osteoblast cells. Additionally, to control the shape retention ability of the scaffolds dual crosslinking was applied. Thus, the developed Alginate-Gelatin based 3D scaffold maintains the required balance between biomechanics and soft tissue regeneration.

Architectured helically coiled scaffolds from elastomeric poly(butylene succinate) (PBS) copolyester via wet electrospinning

Electrospinning is one of the most investigated methods used to produce polymeric fiber scaffolds that mimic the morphology of native extracellular matrix. These structures have been extensively studied in the context of scaffolds for tissue regeneration. However, the compactness of materials obtained by traditional electrospinning, collected as two-dimensional non-woven scaffolds, can limit cell infiltration and tissue ingrowth. In addition, for applications in smooth muscle tissue engineering, highly elastic scaffolds capable of withstanding cyclic mechanical strains without suffering significant permanent deformations are preferred. In order to address these challenges, we report the fabrication of microscale 3D helically coiled scaffolds (referred as 3D-HCS) by wet-electrospinning method, a modification of the traditional electrospinning process in which a coagulation bath (non-solvent system for the electrospun material) is used as the collector. The present study, for the first time, successfully demonstrates the feasibility of using this method to produce various architectures of 3D helically coiled scaffolds (HCS) from segmented copolyester of poly (butylene succinate-co-dilinoleic succinate) (PBS-DLS), a thermoplastic elastomer. We examined the role of process parameters and propose a mechanism for the HCS formation. Fabricated 3D-HCS showed high specific surface area, high porosity, and good elasticity. Further, the marked increase in cell proliferation on 3D-HCS confirmed the suitability of these materials as scaffolds for soft tissue engineering.

Biodegradable polyurethane/graphene oxide scaffolds for soft tissue engineering: in vivo behavior assessment

In this work, 3D porous electrospun scaffolds based on DegraPol® (DP), a polyester urethane, with different concentrations of graphene oxide (GO) (0.0–2.0 wt%) were obtained. In order to produce scaffolds with increased porosity, solutions of DP and GO were co-electrospun with polyethylene oxide (PEO), which was subsequently removed. The electrospinning resulted in the formation of porous and fibrous scaffolds with superior elasticity. The colloidal Ag was successfully used as a novel method of scaffold sterilization. The results of the in vivo analysis showed scaffold degradation, absence of an inflammatory process and penetration of tissue cells in the scaffold.

The Use of Platelet-Rich Plasma to Promote Cell Recruitment into Low-Molecular-Weight Fucoidan-Functionalized Poly(Ester-Urea-Urethane) Scaffolds for Soft-Tissue Engineering.

Due to their elastomeric behavior, polyurethane-based scaffolds can find various applications in soft-tissue engineering. However, their relatively inert surface has to be modified in order to improve cell colonization and control cell fate. The present study focuses on porous biodegradable scaffolds based on poly(ester-urea-urethane), functionalized concomitantly to the scaffold elaboration with low-molecular-weight (LMW) fucoidan; and their bio-activation with platelet rich plasma (PRP) formulations with the aim to promote cell response. The LMW fucoidan-functionalization was obtained in a very homogeneous way, and was stable after the scaffold sterilization and incubation in phosphate-buffered saline. Biomolecules from PRP readily penetrated into the functionalized scaffold, leading to a biological frame on the pore walls. Preliminary in vitro assays were assessed to demonstrate the improvement of scaffold behavior towards cell response. The scaffold bio-activation drastically improved cell migration. Moreover, cells interacted with all pore sides into the bio-activated scaffold forming cell bridges across pores. Our work brought out an easy and versatile way of developing functionalized and bio-activated elastomeric poly(ester-urea-urethane) scaffolds with a better cell response.

Electrospun biodegradable chitosan based-poly(urethane urea) scaffolds for soft tissue engineering

The composition and architecture of a scaffold determine its supportive role in tissue regeneration. In this work, we demonstrate the feasibility of obtaining a porous electrospun fibrous structure from biodegradable polyurethanes (Pus) synthesized using polycaprolactone-diol as soft segment and, as chain extenders, chitosan (CS) and/or dimethylol propionic acid. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance confirmed the syntheses. Fibre mats' properties were analysed and compared with those of solvent cast films. Scanning electron microscopy images of the electrospun scaffolds revealed fibres with diameters around 1 μm. From tensile tests, we found that Young's modulus increases with CS content and is higher for films (2.5 MPa to 6.5 MPa) than for the corresponding fibre mats (0.8 MPa to 3.2 MPa). The use of CS as the only chain extender improves recovery ratio and resilience. From X-ray diffraction, a higher crystalline degree was identified in fibre mats than in the corresponding films. Films' wettability was enhanced by the presence of CS as shown by the decrease of water contact angle. X-ray photoelectron spectroscopy revealed that while ester groups are predominant at the films' surface, ester and urethanes are present in similar concentrations at fibres' surface, favouring the interaction with water molecules. Both films and fibres undergo hydrolytic degradation. In vitro evaluation was performed with human dermal fibroblasts. No PU sample revealed cytotoxicity. Cells adhered to fibre mats better than to films and proliferation was observed only for samples of CS-containing PUs. Results suggest that electrospun fibres of CS-based polyurethanes are good candidate scaffolds for soft tissue engineering.

Fabrication of bioactive glass particles composite porous fibers by combination of electrospinning and phase separation

In the present study, a porous electrospun polycaprolactone (PCL) scaffold incorporated with bioactive glass (BG) particles was fabricated by combining phase separation with electrospinning. Chloroform (CF) and dimethyl formamide (DMF) were used as good solvents, while dimethyl sulfoxide (DMSO) was used as a poor solvent to generate pores on the fiber surface. The effects of PCL concentration, DMSO amount and BG particles dosage on the surface morphology of electrospun fibers were investigated, respectively. Fibrous scaffolds with well-distributed pores and uniform diameter were successfully obtained by using 12% w/v PCL in solution with good/poor solvent ratios at 90% v/v. The addition of BG particles (<8%w/v)in electrospun solution did not lead to any deformation of the porous fibers. The porous fibrous scaffolds incorporated with BG particles may be a promising scaffolds for soft tissue engineering.