Injectable polyethylene glycol-laponite composite hydrogels as articular cartilage scaffolds with superior mechanical and rheological properties

In this study, injectable PEG-based hydrogels containing Laponite particles with mechanical and structural properties close to the natural articular cartilage are introduced. The nanocomposites are fabricated by imide ring opening reactions utilizing synthesized copolymers containing PEG blocks and nanoclay through a two-step thermal poly-(amic acid) process. Butane diamine is used as nucleophilic reagent and hydrogels with interconnected pores with sizes in the range of 100–250?µm are prepared. Improved viscoelastic properties compared with the conventional PEG hydrogels are shown. Evaluation of cell viability utilizing human mesenchymal stem cells determines cytocompatibility of the nanocomposite hydrogels.     

Incorporation of chitosan nanoparticles into silk fibroin-based porous scaffolds: Chondrogenic differentiation of stem cells

A silk fibroin-chondroitin sulfate-sodium alginate (SF-CHS-SA) porous scaffold containing chitosan nanoparticles (NPs) was investigated. The proliferation of adipose-derived stem cells (ASCs) was studied by SEM, fluorescent microscopy, alcian blue staining, dimethylmethylene blue assay, and real-time polymerization chain reaction. The results showed that incorporation of NPs into the scaffold improved compressive modulus (5.6 ± 0.15 MPa). The amount of glycosaminoglycan expression of the ASCs was reached to 8.9 ± 0.3 µg/mL. The gene expressions of aggrecan, collagen II, and SOX9 of the ASCs were significantly improved. This study revealed that the prepared scaffold can be used as a substrate for cartilage tissue engineering.     

Electrospun scaffolds with surfaces modified by plasma for regeneration of articular cartilage tissue: a pilot study in rabbit

Abstract

This paper focuses on the development of an electrospun scaffold for application in cartilage regenerative engineering. Based on polylactic acid and polycaprolactone, the surface was modified with plasma polymerized polypyrrole-Iodine (PPy-I), which aims to improve cellular interaction and to ease the adhesion of the protein aggrecan (AG), an important component of the extracellular matrix of native cartilage. In vitro tests with autologous chondrocytes cells of rabbit were performed, and in vivo tests were performed over 30 days. Morphological and chemical characterizations of the scaffolds were executed. A comparison of the neotissue was done through tensile tests, histology and immunohistochemistry.     

Osteochondral scaffolds based on electrospinning method: General review on new and emerging approaches

The complexity and gradient structure of osteochondral (OC) tissue have become a challenging topic in interfacial tissue engineering (ITE) researches. Various reports have been published about the replaced OC scaffolds prepared by altered techniques; however, electrospinning as an effective method has not been sufficiently reported yet. This general review of the literature is focused on the preclinical studies published about the OC scaffolds prepared by electrospinning method and describing an outline on future directions and challenges. This overview revealed the necessity of additional preclinical studies to develop optimal scaffolds that can effectively replace and treat defected OC tissue.     

Articular cartilage: New directions and barriers of scaffolds development – review

Despite progress which has been made in recent years in the field of cell-based therapies or cell scaffolds for cartilage regeneration, a lot of work still needs to be done. Scaffolds remain a great base for tissue regeneration. However, proper implantation procedures or post-treatment still await development.

In this review we summarize paths of cartilage treatment, especially focusing on cell scaffold design and manufacture. As well as the advantages and disadvantages of available or investigated methods and materials, especially focusing on cartilage scaffold design. We show the most promising directions and barriers in the creation of healthy tissue.     

A novel strategy for cartilage tissue engineering: Collagenase-loaded cryogel scaffolds in a sheep model

In this study, we developed a novel strategy, through which cartilage tissue pieces were placed in a sheep cartilage defect model and covered with a collagenase incorporated cryogel scaffold (in vivo cartilage tissue engineering, IVCTE group). While applying this strategy, the chondrocytes could be isolated inside the body and the treatment could be accomplished in one session. To compare our strategy, to another group, in which we used cultured cells and Chondro-gide, standard matrix-induced autologous chondrocyte implantation (MACI) was applied. Although the MACI applied group demonstrated better healing than IVCTE, the type II collagen synthesis was better in the IVCTE group compared to MACI applied group. Collagenase did not have detrimental effect on surrounding cartilage in IVCTE group. The preliminary results of the novel strategy applied group (IVCTE) were promising.     

Preparation and characterization of novel chitosan/nanodiopside/nanohydroxyapatite composite scaffolds for tissue engineering applications

Chitosan/nanodiopside/nanohydroxyapatite (CS/nDP/nHAp) composite scaffolds were prepared from the mixture of chitosan, nDP, and nHAp in different inorganic/organic weight ratios by using the freeze-drying method. The prepared nHAp and composite scaffolds were investigated using BET, TG, FT-IR, SEM, EDS, and XRD techniques. The composite scaffolds had 50–85% porosities with interlinked porous networks. Moreover, investigation of the cell proliferation, adhesion, and viability using MTT test, and mouse preosteoblast cell proved the cytocompatibile nature of the composite scaffolds with improved cell attachment and proliferation. All these results essentially illustrated that this composite could be a potential for bone tissue engineering applications.     

Three-dimensional silk impregnated HAp/PHBV nanofibrous scaffolds for bone regeneration

Three-dimensional silk fibroin impregnated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibrous scaffolds with or without hydroxyapatite (HAp) were prepared by wet-electrospinning method followed by freeze-drying. Scaffolds with cotton wool-like structure have the average fiber diameter of 450–850?nm with 80–85% porosity. In-vitro cell culture tests using MG-63 osteosarcoma human cells revealed improved cell viability, alkaline phosphatase (ALP) activity and total cellular protein amount on the silk impregnated scaffolds compared to PHBV and HAp/PHBV scaffolds after 10 days of cell culture. Immunohistochemical analyses on the silk impregnated scaffolds showed that HAp triggered cell penetration and type I collagen production. Besides, HAp mineralization tendency increased with a decrease in percent crystallinity of the scaffolds comprising HAp and silk after 4 weeks of incubation in simulated body fluid. Consequently, cotton wool-like HAp/PHBV-SF scaffold would be a promising candidate as a bone-filling material for tissue regeneration.     

Synthesis and characterization of injectable chitosan cryogel microsphere scaffolds

Treatment of tissue defects involves invasive processes such as implanting the tissue engineered scaffold to the defected area. Injectable scaffolds are increasingly being developed to achieve tissue regeneration in a less invasive manner. In this study, injectable chitosan cryogels in the form of microspheres were synthesized combining the water in oil emulsification method with the crosslinking of microspheres during cryogelation. The effects of polymer ratio, crosslinker concentration, cryogelation temperature, and stirring speed on the resulting cryogels’ chemistry, pore morphology, microsphere size, swelling ratio, degree of crosslinking, and degradation rate were examined for a possible noninvasive tissue engineering application. Microspheres with optimized properties were developed with an average pore and particle size of 5.50?±?0.63 and 220.11?±?25.58?µm at a chitosan ratio of 1%, glutaraldehyde concentration of 3%, reaction temperature of ?16°C, and stirring rate of 1,000?rpm.     

Hypoxia and flow perfusion modulate proliferation and gene expression of articular chondrocytes on porous scaffolds

The combination of reduced oxygen tension and flow perfusion bioreactor culture is investigated for its effect on the proliferation, glycosaminoglycan production, and chondrogenic gene expression of bovine articular chondrocytes on porous polymer scaffolds. It was hypothesized that the combination of such factors would more closely replicate the in situ environment of these cells, leading to improvements in the cell phenotype. Chondrocytes were seeded onto electrospun poly(ε‐caprolactone) scaffolds and cultured in static or perfusion culture in either normoxic or hypoxic conditions for 6days. Results demonstrated that the combination of hypoxic and perfusion culture led to an increase in chondrocyte proliferation and glycosaminoglycan production, as well as an improvement in the ratio of collagen II/I gene expression over perfusion culture alone. The results demonstrate the need to combine multiple signals in vitro, in order to improve tissue growth by more closely replicating the native environment of cells. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3158–3166, 2013     

Evaluation of the chondrogenic differentiation of mesenchymal stem cells on hybrid biomimetic scaffolds

Hybrid materials are widely and promisingly used as scaffolds in cartilage tissue remodeling. In this study, hybrid scaffolds consist of polycaprolactone (PCL), poly(vinyl alcohol) (PVA) with/without gelatin (GEL) to mimic natural cartilage extracellular matrix (ECM) were investigated. Scaffolds were prepared by freeze drying and characterized by scanning electron microscopy and compressive mechanical testing. Biological assays of mesenchymal stem cell (MSC) cultures, 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide, and dimethyl methylene blue were performed, and real‐time polymerization chain reaction analysis of the cartilage‐specific ECM gene marker expression was done. The results show an open interconnected porous structure with a compression modulus of 1.27 ± 0.04 MPa. The surface of the scaffolds showed an excellent efficiency in the adhesion and proliferation of MSCs. A significant increase in the proteoglycan content from 3.70 ± 0.96 to 5.4 ± 1.13 μg/mL was observed after 14 days in the PCL–PVA–GEL scaffolds. The expression amount of the sex‐determining region Y–Box 9 (SOX9) and collagen II (COL2) mRNA levels of the MSCs showed significant increases in SOX9 and COL2, respectively in comparison with PCL–PVA scaffold. The study revealed that the aforementioned scaffold as a blend of natural and synthetic polymers may be a promising substrate in tissue engineering for cartilage repair with MSC transplantation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40635.     

Degradable natural polymer hydrogels for articular cartilage tissue engineering

Articular cartilage has poor ability to heal once damaged. Tissue engineering with scaffolds of polymer hydrogels is promising for cartilage regeneration and repair. Polymer hydrogels composed of highly hydrated crosslinked networks mimic the collagen networks of the cartilage extracellular matrix and thus are employed as inserts at cartilage defects not only to temporarily relieve the pain but also to support chondrocyte proliferation and neocartilage regeneration. The biocompatibility, biofunctionality, mechanical properties, and degradation of the polymer hydrogels are the most important parameters for hydrogel‐based cartilage tissue engineering. Degradable biopolymers with natural origin have been widely used as biomaterials for tissue engineering because of their outstanding biocompatibility, low immunological response, low cytotoxicity, and excellent capability to promote cell adhesion, proliferation, and regeneration of new tissues. This review covers several important natural proteins (collagen, gelatin, fibroin, and fibrin) and polysaccharides (chitosan, hyaluronan, alginate and agarose) widely used as hydrogels for articular cartilage tissue engineering. The mechanical properties, structures, modification, and structure–performance relationship of these hydrogels are discussed since the chemical structures and physical properties dictate the in vivo performance and applications of polymer hydrogels for articular cartilage regeneration and repair. © 2012 Society of Chemical Industry     

In vitro and in vivo properties of graphene-incorporated scaffolds for bone defect repair

The employment of graphene and its derivatives, graphene oxide and reduced graphene oxide, is extending from bioimaging and fabrications of biosensors to drug delivery and tissue engineering in the biomedical area. Graphene family-incorporated scaffolds, used in bone tissue engineering and bone regenerative medicine, profit superior properties of these materials, such as enhanced mechanical properties, large surface area, and the existence of functional groups. At the same time, problems related to cytotoxicity and adverse immune response of graphene family are solved when they are applied to produce 3-dimensional scaffolds. The objective of this review is to focus on in vitro properties of scaffolds consisting of graphene or its derivatives, especially osteogenic and antibacterial properties, as well as the influence of graphene and its derivatives on in vivo performances of implanted bone scaffolds. The positive effect of graphene and its two derivatives on attachment, and cell proliferation, as well as in vitro osteogenic differentiation of different cells was undeniable. Besides, the synergetic outcome of using graphene family on the antibacterial feature of scaffolds, especially incorporation with the silver element, was effective. Moreover, successful treatment of critical-sized bone defects was reported during in vivo preclinical tests when graphene or its derivatives-incorporated scaffolds were used. However, the limited number of in vivo studies should be considered as one of the main shortcomings to use graphene as a promising candidate for treating bone defects. It is anticipated that the increased number of well-designed preclinical studies could improve the applications of graphene incorporated scaffolds in bone tissue engineering/regeneration, and find out explanations and appropriate solutions to possible long-term toxicity and nonbiodegradability of these materials.     

Electrospun polycaprolactone scaffolds for tissue engineering: a review

Polycaprolactone is a biodegradable and biocompatible polyester which has a wide range of applications in tissue engineering. Electrospinning, the versatile technique, used for the fabrication of fibrous scaffolds, which is widely used in tissue engineering, due to the ability of fabrication of nano/micro-scale fiber scaffolds. Polycaprolactone nanofiber scaffolds are widely used in tissue engineering and drug delivery. Polycaprolactone can be used in a wide variety of scaffolds construction. In this review, we will discuss the recent advances in the electrospinning of polycaprolactone nanofiber scaffolds in bone, cardiovascular, nerve, and skin tissue engineering.     

Incorporation of zeolite and silica nanoparticles into electrospun PVA/collagen nanofibrous scaffolds: The influence on the physical,chemical properties and cell behavior

Cartilage is under extensive investigation in tissue engineering research. Herein, we evaluated scaffolds prepared by composites of polyvinyl alcohol (PVA) and collagen incorporated with zeolite and silica nanoparticles (nZe and nSi). The scaffolds were prepared by the electrospinning method. The mean diameters of nanofibers were 0.61 ± 0.34 µm for PVA/collagen versuss 0.62 ± 0.22 µm and 0.66 ± 0.25 µm for the PVA/collagen/nZe and the PVA/collagen/nSi scaffolds, respectively. DAPI staining results revealed that cell proliferations on the PVA/collagen/nZe and PVA/collagen/nSi were strikingly higher than on the pure PVA/collagen. The results encouraged further investigation of PVA/collagen/nSi scaffolds as biomimetic platform for chondrocyte cells in tissue engineering.     

Preparation of Pure PLLA,Pure Chitosan,and PLLA/Chitosan Blend Porous Tissue Engineering Scaffolds by Thermally Induced Phase Separation Method and Evaluation of the Corresponding Mechanical and Biological Properties

The aim of this work was to prepare the scaffolds of pure poly (L-lactic acid) 3% (w/v), pure chitosan 3% (w/v), and PLLA/chitosan blend (1:5) 3% (w/v) using TIPS method and investigate their properties and application in tissue engineering. An in vitro degradation study of scaffolds showed the addition of chitosan to PLLA not only increased its degradation rate, but also slowed down its pH value reduction. Addition of chitosan to PLLA increased hydrophilicity, porosity, compressive properties, and cell viability of the scaffolds. The results indicate that among all scaffolds, the most appropriate candidate for tissue engineering is PLLA/chitosan blend.     

Stabilizing effect of carbodiimide and dehydrothermal treatment crosslinking on the properties of collagen/hydroxyapatite scaffolds

This paper reports the effect of the combined technique of dehydrothermal treatment (DHT) and a mixture of 1‐ethyl‐3(3‐dimethylaminopropyl) carbodiimide (EDC) and N‐hydroxysuccinimide (NHS) crosslinking on the physicochemical properties of collagen/hydroxyapatite materials. Collagen and collagen/hydroxyapatite porous scaffolds containing different amounts of collagen and hydroxyapatite were prepared with use of the freeze‐drying technique. All samples were capable of absorbing a large quantity of phosphate buffered saline. Samples crosslinked by DHT+EDC/NHS presented higher resistance to collagenase degradation (with slightly reduced degradation in DHT+EDC/NHS crosslinked scaffolds prepared from 2% collagen solution), whereas DHT scaffolds exhibited faster degradation. Mechanical testing results suggested that scaffolds crosslinked by DHT+EDC/NHS treatment have an improved compressive modulus compared with EDC/NHS crosslinking. The qualitative analysis of colour intensity resulting from the CellTiter 96 Aqueous One Solution Cell Proliferation Assay (MTS) led to the conclusion that all samples, regardless of the crosslinking method, were well tolerated by cells. However, DHT and EDC/NHS crosslinked scaffolds seem to support better cell viability, in contrast to DHT+EDC/NHS crosslinked scaffolds that support cell differentiation instead. DHT+EDC/NHS crosslinked scaffolds markedly increase the specific alkaline phosphatase activity of cells, which may be of benefit in bone tissue engineering. © 2017 Society of Chemical Industry     

From rose petal to bone scaffolds: Using nature to fabricate osteon-like scaffolds for bone tissue engineering applications

In this study, rose petal was used to fabricate osteon-like scaffolds for bone tissue engineering applications. Rose petal was coupled with nanocrystalline forsterite colloid to mimic the lamellar structure of porous osteons. The microstructures on the surface of the petals were utilized as template for pores and lacuna spaces which are suitable for cell attachment. On the other hand, rolling the petals allowed us to form the osteon structure with haversian canal and lacuna spaces on the body of the samples. After trying different temperatures, the results showed that samples annealed at 1100 °C closely mimicked the lacuna spaces, haversian canal, and lamellar structures of osteons. These scaffolds had the pore diameter in the range of about 13–20 μm and presented good bioactivity and biocompatibility. It was found that red rose petal is a good candidate to be used as a template for designing scaffolds for bone tissue engineering applications.     

Polymeric scaffolds for cardiac tissue engineering: requirements and fabrication technologies

Cardiac tissue engineering (TE) is an emerging field, whose main goal is the development of innovative strategies for the treatment of heart diseases, with the aim of overcoming the drawbacks of traditional therapies. One of these strategies involves the implantation of three‐dimensional matrices (scaffolds) capable of supporting tissue formation. Scaffolds designed and fabricated for such application should meet several requirements, concerning both the scaffold‐forming materials and the properties of the scaffold itself. A scaffold for cardiac TE should be biocompatible and biodegradable, mimic the properties of the native cardiac tissue, provide a mechanical support to the regenerating heart and possess an interconnected porous structure to favour cell migration, nutrient and oxygen diffusion, and waste removal. Moreover, the mimesis of myocardium characteristic anisotropy is attracting increasing interest to provide engineered constructs with the possibility to be structurally and mechanically integrated in native tissue. Several conventional and non‐conventional fabrication techniques have been explored in the literature to produce polymeric scaffolds meeting all these requirements. This review describes these techniques, with a focus on their advantages and disadvantages, and their flexibility, with the final goal of providing the reader with the primal knowledge necessary to develop an effective strategy in cardiac TE. © 2013 Society of Chemical Industry     

Three-dimensional polycaprolactone-bioactive glass composite scaffolds: Effect of particle size and volume fraction on mechanical properties and in vitro cellular behavior

In this study, highly porous polycaprolactone-based composites (90% porosity) with hierarchical pore structure (400–500?µm) and nanotopographical features were prepared by 3D printing. 45S5 Bioglass particles with different sizes (<100?nm; 250?nm; 6?µm) and concentrations (2, 6, and 10?vol%) were utilized to attain improved mechanical strength and bioactivity. The micrometric particles embedded in the polymer matrix enhanced the elastic modules up to 235%. The ultrafine particles decorated the struts and affected nanotopography, hydrophilicity, and nanohardness by about 100%. The rate of pore filing lowers in the presence of nanoparticles as compared with microparticles.