In vitro evaluation of electrospun PCL/nanoclay composite scaffold for bone tissue engineering

Hydrogel-Impregnated Self-Oxygenating Electrospun Scaffolds for Bone Tissue Engineering

Bone defects resulting from trauma, disease, or aging present significant challenges in the clinic. Although biomaterial scaffolds for bone-tissue engineering have shown promising results, challenges remain, including the need for adequate mechanical strength and suitable bioactive agents within scaffolds to promote bone formation. Oxygen is a critical factor for successful bone formation, and low oxygen tension inhibits it. In this study, we developed gelatin methacryloyl (GelMA) hydrogel-impregnated electrospun polycaprolactone (PCL) scaffolds that can release oxygen over 3 weeks. We investigated the potential of composite scaffolds for cell survival in bone-tissue engineering. Our results showed that the addition of an increased amount of CaO2 nanoparticles to the PCL scaffolds significantly increased oxygen generation, which was modulated by GelMA impregnation. Moreover, the resulting scaffolds showed improved cytocompatibility, pre-osteoblast adhesion, and proliferation under hypoxic conditions. This finding is particularly relevant since hypoxia is a prevalent feature in various bone diseases. In addition to providing oxygen, CaO2 nanoparticles also act as reinforcing agents improving the mechanical property of the scaffolds, while the incorporation of GelMA enhances cell adhesion and proliferation properties. Overall, our newly developed self-oxygenating composite biomaterials are promising scaffolds for bone-tissue engineering applications.

Evaluation of the effects of halloysite nanotube on polyhydroxybutyrate - chitosan electrospun scaffolds for cartilage tissue engineering applications

Scaffolding method and material that mimic the extracellular matrix (ECM) of host tissue is an integral part of cartilage tissue engineering. This study aims to enhance the properties of electrospun scaffolds made of polyhydroxybutyrate (PHB) - Chitosan (Cs) by adding 1, 3, and 5 wt% halloysite nanotubes (HNT). The morphological, mechanical, and hydrophilicity evaluations expressed that the scaffold containing 3 wt% HNT exhibits the most appropriate features. The FTIR and Raman analysis confirmed hydrogen bond formation between the HNT and PHB-Cs blend. 3 wt% of HNT incorporation decreased the mean fibers' diameter from 965.189 to 745.16 nm and enhanced tensile strength by 169.4 %. By the addition of 3 wt% HNT, surface contact angle decreased from 61.45° ± 3.3 to 46.65 ± 1.8° and surface roughness increased from 684.69 to 747.62 nm. Our findings indicated that biodegradation had been slowed by incorporating HNT into the PHB-Cs matrix. Also, MTT test results demonstrated a significant increase in cell viability of chondrocytes on the PHB-Cs/3 wt% HNT (PC-3H) scaffold after 7 days of cell culture. Accordingly, the PC-3H scaffold can be considered a potential candidate for cartilage tissue engineering.

3D Printed Hierarchical Porous Poly(ε-caprolactone) Scaffolds from Pickering High Internal Phase Emulsion Templating

In the realm of biomaterials, particularly bone tissue engineering, there has been a great increase in interest in scaffolds with hierarchical porosity and customizable multifunctionality. Recently, the three-dimensional (3D) printing of biopolymer-based inks (solutions or emulsions) has gained high popularity for fabricating tissue engineering scaffolds, which optimally satisfies the desired properties and performances. Herein, therefore, we explore the fabrication of 3D printed hierarchical porous scaffolds of poly(ε-caprolactone) (PCL) using the water-in-oil (w/o) Pickering PCL high internal phase emulsions (HIPEs) as the ink in 3D printer. The Pickering PCL HIPEs stabilized using hydrophobically modified nanoclay comprised of aqueous poly(vinyl alcohol) (PVA) as the dispersed phase. Rheological measurements suggested the shear thinning behavior of Pickering HIPEs having a dispersed droplet diameter of 3-25 μm. The pore morphology resembling the natural extracellular matrix and the mechanical properties of scaffolds were customized by tuning the emulsion composition and 3D printing parameters. In vitro biomineralization and drug release studies proved the scaffolds' potential in developing the apatite-rich bioactive interphase and controlled drug delivery, respectively. During in vitro osteoblast (MG63) growth experiments for up to 7 days, good adhesion and proliferation on PCL scaffolds confirmed their cytocompatibility, assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) analysis. This study suggests that the assembly of HIPE templates and 3D printing is a promising approach to creating hierarchical porous scaffolds potentially suitable for bone tissue engineering and can be stretched to other biopolymers as well.

Nanoclays in medicine: a new frontier of an ancient medical practice

Clays have been used as early as 2500 BC in human civilization for medicinal purposes. The ease of availability, biocompatibility, and versatility of these unique charged 2D structures abundantly available in nature have enabled the extensive applications of clays in human history. Recent advances in the use of clays in nanostructures and as components of polymer clay nanocomposites have exponentially expanded the use of clays in medicine. This review covers the details of structures and biomedical applications of several common clays, including montmorillonite, LAPONITE®, kaolinite, and halloysite. Here we describe the applications of these clays in wound dressings as hemostatic agents in drug delivery of drugs for cancer and other diseases and tissue engineering. Also reviewed are recent experimental and modeling studies that elucidate the impact of clay structures on cellular processes and cell adhesion processes. Various mechanisms of clay-mediated bioactivity, including protein localization, modulation of cell adhesion, biomineralization, and the potential of clay nanoparticles to impact cell differentiation, are presented. We also review the current developments in understanding the impact of clays on cellular responses. This review also elucidates new emerging areas of use of nanoclays in osteogenesis and the development of in vitro models of bone metastasis of cancer.

Fabrication and Evaluation of Electrospun Silk Fibroin/Halloysite Nanotube Biomaterials for Soft Tissue Regeneration

The production of nanofibrous materials for soft tissue repair that resemble extracellular matrices (ECMs) is challenging. Electrospinning uniquely produces scaffolds resembling the ultrastructure of natural ECMs. Herein, electrospinning was used to fabricate Bombyx mori silk fibroin (SF) and SF/halloysite nanotube (HNT) composite scaffolds. Different HNT loadings were examined, but 1 wt% HNTs enhanced scaffold hydrophilicity and water uptake capacity without loss of mechanical strength. The inclusion of 1 wt% HNTs in SF scaffolds also increased the scaffold’s thermal stability without altering the molecular structure of the SF, as revealed by thermogravimetric analyses and Fourier transform infrared spectroscopy (FTIR), respectively. SF/HNT 1 wt% composite scaffolds better supported the viability and spreading of 3T3 fibroblasts and the differentiation of C2C12 myoblasts into aligned myotubes. These scaffolds coated with decellularised ECM from 3T3 cells or primary human dermal fibroblasts (HDFs) supported the growth of primary human keratinocytes. However, SF/HNT 1 wt% composite scaffolds with HDF-derived ECM provided the best microenvironment, as on these, keratinocytes formed intact monolayers with an undifferentiated, basal cell phenotype. Our data indicate the merits of SF/HNT 1 wt% composite scaffolds for applications in soft tissue repair and the expansion of primary human keratinocytes for skin regeneration.

Antibacterial Electrospun Polycaprolactone Nanofibers Reinforced by Halloysite Nanotubes for Tissue Engineering

Due to its slow degradation rate, polycaprolactone (PCL) is frequently used in biomedical applications. This study deals with the development of antibacterial nanofibers based on PCL and halloysite nanotubes (HNTs). Thanks to a combination with HNTs, the prepared nanofibers can be used as low-cost nanocontainers for the encapsulation of a wide variety of substances, including drugs, enzymes, and DNA. In our work, HNTs were used as a nanocarrier for erythromycin (ERY) as a model antibacterial active compound with a wide range of antibacterial activity. Nanofibers based on PCL and HNT/ERY were prepared by electrospinning. The antibacterial activity was evaluated as a sterile zone of inhibition around the PCL nanofibers containing 7.0 wt.% HNT/ERY. The morphology was observed with SEM and TEM. The efficiency of HNT/ERY loading was evaluated with thermogravimetric analysis. It was found that the nanofibers exhibited outstanding antibacterial properties and inhibited both Gram- (Escherichia coli) and Gram+ (Staphylococcus aureus) bacteria. Moreover, a significant enhancement of mechanical properties was achieved. The potential uses of antibacterial, environmentally friendly, nontoxic, biodegradable PCL/HNT/ERY nanofiber materials are mainly in tissue engineering, wound healing, the prevention of bacterial infections, and other biomedical applications.

Attapulgite-doped electrospun PCL scaffolds for enhanced bone regeneration in rat cranium defects

Electrospun PCL scaffolds have been widely used for tissue engineering as they have shown great potential to mimic the structure of the natural extracellular matrix (ECM). However, the small pore size and low bioactivity of the scaffolds limit cell migration and tissue formation. In this study, PCL (polycaprolactone), PCL/PEG (polyethylene glycol), and PCL/PEG/ATP (nano-attapulgite) scaffolds were fabricated via electrospinning. To increase the porosity of the scaffolds, they were washed to remove water-soluble PEG fibers. Then the porous structure was measured using scanning electron microscopy (SEM) and atomic force microscopy (AFM), which showed an increased porosity when PEG fibers were removed in PCL/PEG and PCL/PEG/ATP scaffolds. Moreover, the mechanical properties were also analyzed in dry and wet conditions. In vitro mouse multipotent mesenchymal precursor cells were used to assess the biocompatibility of the scaffolds, and osteogenesis was analyzed using CCK-8 and real-time PCR (RT-PCR) methods. Moreover, in vivo μCT, histological and immunohistochemical analyses were conducted to evaluate new bone formation in rat cranium defect models. Washed PCL/PEG/ATP scaffolds were implanted into the cranium defects in rats for 4 or 8 weeks, better cell infiltration was observed in these scaffolds than in unwashed ones. The result demonstrated that washed PCL/PEG/ATP scaffold facilitated the differentiation of MSCs into osteoblasts compared with PCL scaffold, as proved by the increased expression of osteogenic key genes as well as Smad1, Smad4, and Smad5. Furthermore, in vivo studies demonstrated that using the ATP-doped electrospun PCL scaffold can improve the bone regeneration of rat cranium defects. Particularly, the PCL/ATP-30% scaffold has the best effect compared to the other scaffolds. The enhanced osteogenesis and bone repair were related to the PCL/ATP activated BMP/Smad signaling pathway.

Vascularized bone regeneration accelerated by 3D-printed nanosilicate-functionalized polycaprolactone scaffold

Critical oral-maxillofacial bone defects, damaged by trauma and tumors, not only affect the physiological functions and mental health of patients but are also highly challenging to reconstruct. Personalized biomaterials customized by 3D printing technology have the potential to match oral-maxillofacial bone repair and regeneration requirements. Laponite (LAP) nanosilicates have been added to biomaterials to achieve biofunctional modification owing to their excellent biocompatibility and bioactivity. Herein, porous nanosilicate-functionalized polycaprolactone (PCL/LAP) was fabricated by 3D printing technology, and its bioactivities in bone regeneration were investigated in vitro and in vivo. In vitro experiments demonstrated that PCL/LAP exhibited good cytocompatibility and enhanced the viability of bone marrow mesenchymal stem cells (BMSCs). PCL/LAP functioned to stimulate osteogenic differentiation of BMSCs at the mRNA and protein levels and elevated angiogenic gene expression and cytokine secretion. Moreover, BMSCs cultured on PCL/LAP promoted the angiogenesis potential of endothelial cells by angiogenic cytokine secretion. Then, PCL/LAP scaffolds were implanted into the calvarial defect model. Toxicological safety of PCL/LAP was confirmed, and significant enhancement of vascularized bone formation was observed. Taken together, 3D-printed PCL/LAP scaffolds with brilliant osteogenesis to enhance bone regeneration could be envisaged as an outstanding bone substitute for a promising change in oral-maxillofacial bone defect reconstruction.

Emerging 2D Nanomaterials for Biomedical Applications

Two-dimensional (2D) nanomaterials are an emerging class of biomaterials with remarkable potential for biomedical applications. The planar topography of these nanomaterials confers unique physical, chemical, electronic and optical properties, making them attractive candidates for therapeutic delivery, biosensing, bioimaging, regenerative medicine, and additive manufacturing strategies. The high surface-to-volume ratio of 2D nanomaterials promotes enhanced interactions with biomolecules and cells. A range of 2D nanomaterials, including transition metal dichalcogenides (TMDs), layered double hydroxides (LDHs), layered silicates (nanoclays), 2D metal carbides and nitrides (MXenes), metal-organic framework (MOFs), covalent organic frameworks (COFs) and polymer nanosheets have been investigated for their potential in biomedical applications. Here, we will critically evaluate recent advances of 2D nanomaterial strategies in biomedical engineering and discuss emerging approaches and current limitations associated with these nanomaterials. Due to their unique physical, chemical, and biological properties, this new class of nanomaterials has the potential to become a platform technology in regenerative medicine and other biomedical applications.

Optimization of Nanoclay/Polyacrylonitrile Scaffold Using Response Surface Method for Bone Differentiation of Human Mesenchymal Stem Cells

Response surface methodology (RSM) based on the D-optimal algorithm was employed here for the electrospinning of nanoclay/polyacrylonitrile (PAN) composite scaffold by the aim of obtaining the lower fiber diameter and better mechanical properties for bone regeneration. The input parameters included the electrospinning voltage, flow rate and the ratio of nanoclay/PAN and the obtained values for the optimum point were 17 kV for the applied voltage, 0.41 ml/hr for flow rate, and 19.06% for the nanoclay/PAN ratio. The composite scaffold was fabricated in accordance with these optimum values and then studied by scanning electron microscopy and tensile apparatus. The fiber diameter and Young's modulus of the prepared scaffold were respectively 145 ± 12 nm and 267 ± 8.7 MPa that the values were between predicted by RSM. Moreover, the biocompatibility and osteogenic differentiation of the composite scaffold were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and alkaline phosphatase assays. The bare scaffold and tissue culture polystyrene were used as control groups. The results approved stronger bioactivity and bone regeneration with the composite scaffold as a presence of clay nanoparticles.

Nanoclay Reinforced Biomaterials for Mending Musculoskeletal Tissue Disorders

Nanoclay-reinforced biomaterials have sparked a new avenue in advanced healthcare materials that can potentially revolutionize treatment of musculoskeletal defects. Native tissues display many important chemical, mechanical, biological, and physical properties that engineered biomaterials need to mimic for optimal tissue integration and regeneration. However, it is time-consuming and difficult to endow such combinatorial properties on materials via feasible and nontoxic procedures. Fortunately, a number of nanomaterials such as graphene, carbon nanotubes, MXenes, and nanoclays already display a plethora of material properties that can be transferred to biomaterials through a simple incorporation procedure. In this direction, the members of the nanoclay family are easy to functionalize chemically, they can significantly reinforce the mechanical performance of biomaterials, and can provide bioactive properties by ionic dissolution products to upregulate cartilage and bone tissue formation. For this reason, nanoclays can become a key component for future orthopedic biomaterials. In this review, we specifically focus on the rapidly decreasing gap between clinic and laboratory by highlighting their application in a number of promising in vivo studies.

A network analysis of angiogenesis/osteogenesis-related growth factors in bone tissue engineering based on in-vitro and in-vivo data: A systems biology approach

The principal purpose of tissue engineering is to stimulate the injured or unhealthy tissues to revive their primary function through the simultaneous use of chemical agents, cells, and biocompatible materials. Still, choosing the appropriate protein as a growth factor (GF) for tissue engineering is vital to fabricate artificial tissues and accelerate the regeneration procedure. In this study, the angiogenesis and osteogenesis-related proteins' interactions are studied using their related network. Three major biological processes, including osteogenesis, angiogenesis, and angiogenesis regulation, were investigated by creating a protein-protein interaction (PPI) network (45 nodes and 237 edges) of bone regeneration efficient proteins. Furthermore, a gene ontology and a centrality analysis were performed to identify essential proteins within a network. The higher degree in this network leads to higher interactions between proteins and causes a considerable effect. The most highly connected proteins in the PPI network are the most remarkable for their employment. The results of this study showed that three significant proteins including prostaglandin endoperoxide synthase 2 (PTGS2), TEK receptor tyrosine kinase (TEK), and fibroblast growth factor 18 (FGF18) were involved simultaneously in osteogenesis, angiogenesis, and their positive regulatory. Regarding the available literature, the results of this study confirmed that PTGS2 and FGF18 could be used as a GF in bone tissue engineering (BTE) applications to promote angiogenesis and osteogenesis. Nevertheless, TEK was not used in BTE applications until now and should be considered in future works to be examined in-vitro and in-vivo.

The role of lithium in the osteogenic bioactivity of clay nanoparticles

LAPONITE® clay nanoparticles are known to exert osteogenic effects on human bone marrow stromal cells (HBMSCs), most characteristically, an upregulation in alkaline phosphatase activity and increased calcium deposition. The specific properties of LAPONITE® that impart its bioactivity are not known. In this study the role of lithium, a LAPONITE® degradation product, was investigated through the use of lithium salts and lithium modified LAPONITE® formulations. In contrast to intact particles, lithium ions applied at concentrations equivalent to that present in LAPONITE®, failed to induce any significant increase in alkaline phosphatase (ALP) activity. Furthermore, no significant differences were observed in ALP activity with modified clay structures and the positive effect on osteogenic gene expression did not correlate with the lithium content of modified clays. These results suggest that other properties of LAPONITE® nanoparticles, and not their lithium content, are responsible for their bioactivity.

Electrospinning of in situ synthesized silica-based and calcium phosphate bioceramics for applications in bone tissue engineering: A review

The field of bone tissue engineering (BTE) focuses on the repair of bone defects that are too large to be restored by the natural healing process. To that purpose, synthetic materials mimicking the natural bone extracellular matrix (ECM) are widely studied and many combinations of compositions and architectures are possible. In particular, the electrospinning process can reproduce the fibrillar structure of bone ECM by stretching a viscoelastic solution under an electrical field. With this method, nano/micrometer-sized fibres can be produced, with an adjustable chemical composition. Therefore, by shaping bioactive ceramics such as silica, bioactive glasses and calcium phosphates through electrospinning, promising properties for their use in BTE can be obtained. This review focuses on the in situ synthesis and simultaneous electrospinning of bioceramic-based fibres while the reasons for using each material are correlated with its bioactivity. Theoretical and practical considerations for the synthesis and electrospinning of these materials are developed. Finally, investigations into the in vitro and in vivo bioactivity of different systems using such inorganic fibres are exposed.

Regenerative medicine and drug delivery: Progress via electrospun biomaterials

Worldwide research on electrospinning enabled it as a versatile technique for producing nanofibers with specified physio-chemical characteristics suitable for diverse biomedical applications. In the case of tissue engineering and regenerative medicine, the nanofiber scaffolds' characteristics are custom designed based on the cells and tissues specific needs. This fabrication technique is also innovated for the production of nanofibers with special micro-structure and secondary structure characteristics such as porous fibers, hollow structure, and core- sheath structure. This review attempts to critically and succinctly capture the vast number of developments reported in the literature over the past two decades. We then discuss their applications as scaffolds for induction of cells growth and differentiation or as architecture for being used as graft for tissue engineering. The special nanofibers designed for improving regeneration of several tissues including heart, bone, central nerve system, spinal cord, skin and ocular tissue are introduced. We also discuss the potential of the electrospinning in drug delivery applications, which is a critical factor for cell culture, tissue formation and wound healing applications.

Fabrication and optimization of Nanodiamonds-composited poly(ε-caprolactone) fibrous matrices for potential regeneration of hard tissues

Background

Electrospun fibrous matrices are of great importance for tissue engineering and drug delivery device. However, relatively low mechanical strength of the fibrous matrix is one of the major disadvantages. NDs with a positive charge were selected to enhance the mechanical property of a composited fibrous matrix by inducing the intermolecular interaction between NDs and polymer chain. We prepared ND-composited poly (ε-caprolactone) (PCL) fibrous matrices by electrospinning and evaluated their performance in terms of mechanical strength and cell behaviors.

Methods

A predetermined amounts of NDs (0.5, 1, 2 and 3 wt%) were added into PCL solution in a mixture of chloroform and 2,2,2-trifluoroethanol (8:2). ND-composited PCL (ND/PCL) fibrous matrices were prepared by electrospinning method. The tensile properties of the ND/PCL fibrous matrices were analyzed by using a universal testing machine. Mouse calvaria-derived preosteoblast (MC3T3-E1) was used for cell proliferation, alkaline phosphatase (ALP) assay, and Alizarin Red S staining.

Results

The diameters of the fibrous matrices were adjusted to approximately 1.8 μm by changing process variables. The intermolecular interaction between NDs and PCL polymers resulted in the increased tensile strength and the favorable interfacial adhesion in the ND/PCL fibrous matrices. The ND/PCL fibrous matrix with 1 wt% of ND had the highest tensile strength among the samples and also improved proliferation and differentiation of MC3T3-E1 cells.

Conclusions

Compared to the other samples, the ND/PCL fibrous matrix with 1 wt% of ND concentration exhibited superior performances for MC3T3 cells. The ND/PCL fibrous matrix can be potentially used for bone and dental tissue engineering.

A review of evolution of electrospun tissue engineering scaffold: From two dimensions to three dimensions

The potential of electrospinning process to fabricate ultrafine fibers as building blocks for tissue engineering scaffolds is well recognized. The scaffold construct produced by electrospinning process depends on the quality of the fibers. In electrospinning, material selection and parameter setting are among many factors that contribute to the quality of the ultrafine fibers, which eventually determine the performance of the tissue engineering scaffolds. The major challenge of conventional electrospun scaffolds is the nature of electrospinning process which can only produce two-dimensional electrospun mats, hence limiting their applications. Researchers have started to focus on overcoming this limitation by combining electrospinning with other techniques to fabricate three-dimensional scaffold constructs. This article reviews various polymeric materials and their composites/blends that have been successfully electrospun for tissue engineering scaffolds, their mechanical properties, and the various parameters settings that influence the fiber morphology. This review also highlights the secondary processes to electrospinning that have been used to develop three-dimensional tissue engineering scaffolds as well as the steps undertaken to overcome electrospinning limitations.

Nanocarbons in Electrospun Polymeric Nanomats for Tissue Engineering: A Review

Electrospinning is a versatile process technology, exploited for the production of fibers with varying diameters, ranging from nano- to micro-scale, particularly useful for a wide range of applications. Among these, tissue engineering is particularly relevant to this technology since electrospun fibers offer topological structure features similar to the native extracellular matrix, thus providing an excellent environment for the growth of cells and tissues. Recently, nanocarbons have been emerging as promising fillers for biopolymeric nanofibrous scaffolds. In fact, they offer interesting physicochemical properties due to their small size, large surface area, high electrical conductivity and ability to interface/interact with the cells/tissues. Nevertheless, their biocompatibility is currently under debate and strictly correlated to their surface characteristics, in terms of chemical composition, hydrophilicity and roughness. Among the several nanofibrous scaffolds prepared by electrospinning, biopolymer/nanocarbons systems exhibit huge potential applications, since they combine the features of the matrix with those determined by the nanocarbons, such as conductivity and improved bioactivity. Furthermore, combining nanocarbons and electrospinning allows designing structures with engineered patterns at both nano- and microscale level. This article presents a comprehensive review of various types of electrospun polymer-nanocarbon currently used for tissue engineering applications. Furthermore, the differences among graphene, carbon nanotubes, nanodiamonds and fullerenes and their effect on the ultimate properties of the polymer-based nanofibrous scaffolds is elucidated and critically reviewed.

Chitosan-poly(vinyl alcohol) nanofibers by free surface electrospinning for tissue engineering applications

Deformities in tissues and organs can be treated by using tissue engineering approach offering the development of biologically functionalized scaffolds from a variety of polymer blends which mimic the extracellular matrix and allow adjusting the material properties to meet the defect architecture. In recent years, research interest has been shown towards the development of chitosan (CS) based biomaterials for tissue engineering applications, because of its minimal foreign body reactions, intrinsic antibacterial property, biocompatibility, biodegradability and ability to be molded into various geometries and forms thereby making it suitable for cell ingrowth and conduction. The present work involves the fabrication of nanofibrous scaffold from CS and poly(vinyl alcohol) blends by free-surface electrospinning method. The morphology and functional characteristics of the developed scaffolds were assessed by field emission scanning electron microscopy and fourier transformed infra-red spectra analysis. The morphological analysis showed the average fiber diameter was 269 nm and thickness of the mat was 200-300 µm. X-ray diffraction study confirmed the crystalline nature of the prepared scaffolds, whereas hydrophilic characteristic of the prepared scaffolds was confirmed by measured contact angle. The scaffolds possess an adequate biodegradable, swelling and mechanical property that is found desirable for tissue engineering applications. The cell study using umbilical cord blood-derived mesenchymal stem cells has confirmed the in vitro biocompatibility and cell supportive property of the scaffold thereby depicting their potentiality for future clinical applications.

Bioactivity assessment of PLLA/PCL/HAP electrospun nanofibrous scaffolds for bone tissue engineering

AIMS

The purpose of this paper was to fabricate PLLA/PCL nanofibrous scaffolds containing HAP to mimic the native bone extracellular matrix for potential applications as bone tissue engineering scaffolds materials and ultimately to help the repairing of bone defects.

MATERIALS AND METHODS

PLLA (MW 200kDa), PCL (MW 80kDa), HAP, dichloromethane, N,N-dimethylformamide; α-MEM, FBS, trypsin-EDTA, penicillin G, streptomycin, β-sodium glycerophosphate, l-ascorbic acid, dexamethasone; CCK-8, Alkaline Phosphatase Assay Kit, Mouse Osteocalcin ELISA Kit, MC3T3-E1 cells. PLLA, PCL and HAP were dissolved in the solution of DCM and DMF to fabricate nanofibrous scaffolds through electrospinning. The morphology of the scaffolds was investigated with SEM, while the diameter of the fibers, pore size and water uptake of the scaffolds were tested, respectively. TGA was carried out to verify the percentage of HAP in the composite scaffolds fabricated with different HAP concentrations. Cell count kit-8 assay, alkaline phosphatase (ALP) assay, and osteocalcin assay were applied to observe the MC3T3-E1 cells proliferation, differentiation on the composite scaffolds.

KEY FINDINGS

MC3T3-E1 cells were found to grow actively on the composite scaffolds based on the results of CCK-8 assay. The level of MC3T3-E1 differentiation was evaluated through the ALP activity and osteocalcin concentration, which showed higher value with HAP containing (PLLA/PCL/HAP) than that ones without (PLLA/PCL).

SIGNIFICANCE

The results demonstrated that the biocomposite PLLA/PCL/HAP nanofibrous scaffold should be a promising candidate for proliferation, differentiation and mineralization of osteoblasts, and potentially can be used for bone tissue regeneration.

Sustained Release of Antibacterial Agents from Doped Halloysite Nanotubes

The use of nanomaterials for improving drug delivery methods has been shown to be advantageous technically and viable economically. This study employed the use of halloysite nanotubes (HNTs) as nanocontainers, as well as enhancers of structural integrity in electrospun poly-e-caprolactone (PCL) scaffolds. HNTs were loaded with amoxicillin, Brilliant Green, chlorhexidine, doxycycline, gentamicin sulfate, iodine, and potassium calvulanate and release profiles assessed. Selected doped halloysite nanotubes (containing either Brilliant Green, amoxicillin and potassium calvulanate) were then mixed with poly-e-caprolactone (PLC) using the electrospinning method and woven into random and oriented-fibered nanocomposite mats. The rate of drug release from HNTs, HNTs/PCL nanocomposites, and their effect on inhibiting bacterial growth was investigated. Release profiles from nanocomposite mats showed a pattern of sustained release for all bacterial agents. Nanocomposites were able to inhibit bacterial growth for up to one-month with only a slight decrease in bacterial growth inhibition. We propose that halloysite doped nanotubes have the potential for use in a variety of medical applications including sutures and surgical dressings, without compromising material properties.

Nanomaterials for Engineering Stem Cell Responses

Recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. Synergistic interactions between nanomaterials and stem cell engineering offer numerous possibilities to address some of the daunting challenges in regenerative medicine, such as controlling trigger differentiation, immune reactions, limited supply of stem cells, and engineering complex tissue structures. Specifically, the interactions between stem cells and their microenvironment play key roles in controlling stem cell fate, which underlines therapeutic success. However, the interactions between nanomaterials and stem cells are not well understood, and the effects of the nanomaterials shape, surface morphology, and chemical functionality on cellular processes need critical evaluation. In this Review, focus is put on recent development in nanomaterial-stem cell interactions, with specific emphasis on their application in regenerative medicine. Further, the emerging technologies based on nanomaterials developed over the past decade for stem cell engineering are reviewed, as well as the potential applications of these nanomaterials in tissue regeneration, stem cell isolation, and drug/gene delivery. It is anticipated that the enhanced understanding of nanomaterial-stem cell interactions will facilitate improved biomaterial design for a range of biomedical and biotechnological applications.

Design, construction and mechanical testing of digital 3D anatomical data-based PCL-HA bone tissue engineering scaffold

The study aims to investigate the techniques of design and construction of CT 3D reconstructional data-based polycaprolactone (PCL)-hydroxyapatite (HA) scaffold. Femoral and lumbar spinal specimens of eight male New Zealand white rabbits were performed CT and laser scanning data-based 3D printing scaffold processing using PCL-HA powder. Each group was performed eight scaffolds. The CAD-based 3D printed porous cylindrical stents were 16 piece × 3 groups, including the orthogonal scaffold, the Pozi-hole scaffold and the triangular hole scaffold. The gross forms, fiber scaffold diameters and porosities of the scaffolds were measured, and the mechanical testing was performed towards eight pieces of the three kinds of cylindrical scaffolds, respectively. The loading force, deformation, maximum-affordable pressure and deformation value were recorded. The pore-connection rate of each scaffold was 100 % within each group, there was no significant difference in the gross parameters and micro-structural parameters of each scaffold when compared with the design values (P > 0.05). There was no significant difference in the loading force, deformation and deformation value under the maximum-affordable pressure of the three different cylinder scaffolds when the load was above 320 N. The combination of CT and CAD reverse technology could accomplish the design and manufacturing of complex bone tissue engineering scaffolds, with no significant difference in the impacts of the microstructures towards the physical properties of different porous scaffolds under large load.

Magnetic resonance functional nano-hydroxyapatite incorporated poly(caprolactone) composite scaffolds for in situ monitoring of bone tissue regeneration by MRI

In this study, we have reported the incorporation of a multi-modal contrast agent based on hydroxyapatite nanocrystals, within a poly(caprolactone)(PCL) nanofibrous scaffold by electrospinning. The multifunctional hydroxyapatite nanoparticles (MF-nHAp) showed simultaneous contrast enhancement for three major molecular imaging techniques. In this article, the magnetic resonance (MR) contrast enhancement ability of the MF-nHAp was exploited for the purpose of potentially monitoring as well as for influencing tissue regeneration. These MF-nHAp containing PCL scaffolds were engineered in order to enhance the osteogenic potential as well as its MR functionality for their application in bone tissue engineering. The nano-composite scaffolds along with pristine PCL were evaluated physico-chemically and biologically in vitro, in the presence of human mesenchymal stem cells (hMSCs). The incorporation of 30-40 nm sized MF-nHAp within the nanofibers showed a substantial increase in scaffold strength, protein adsorption, proliferation, and osteogenic differentiation of hMSCs along with enhanced MR functionality. This preliminary study was performed to eventually exploit the MR contrast imaging capability of MF-nHAp in nanofibrous scaffolds for real-time imaging of the changes in the tissue engineered construct.

Nanoclay-enriched poly(ɛ-caprolactone) electrospun scaffolds for osteogenic differentiation of human mesenchymal stem cells

Musculoskeletal tissue engineering aims at repairing and regenerating damaged tissues using biological tissue substitutes. One approach to achieve this aim is to develop osteoconductive scaffolds that facilitate the formation of functional bone tissue. We have fabricated nanoclay-enriched electrospun poly(ɛ-caprolactone) (PCL) scaffolds for osteogenic differentiation of human mesenchymal stem cells (hMSCs). A range of electrospun scaffolds is fabricated by varying the nanoclay concentrations within the PCL scaffolds. The addition of nanoclay decreases fiber diameter and increases surface roughness of electrospun fibers. The enrichment of PCL scaffold with nanoclay promotes in vitro biomineralization when subjected to simulated body fluid (SBF), indicating bioactive characteristics of the hybrid scaffolds. The degradation rate of PCL increases due to the addition of nanoclay. In addition, a significant increase in crystallization temperature of PCL is also observed due to enhanced surface interactions between PCL and nanoclay. The effect of nanoclay on the mechanical properties of electrospun fibers is also evaluated. The feasibility of using nanoclay-enriched PCL scaffolds for tissue engineering applications is investigated in vitro using hMSCs. The nanoclay-enriched electrospun PCL scaffolds support hMSCs adhesion and proliferation. The addition of nanoclay significantly enhances osteogenic differentiation of hMSCs on the electrospun scaffolds as evident by an increase in alkaline phosphates activity of hMSCs and higher deposition of mineralized extracellular matrix compared to PCL scaffolds. Given its unique bioactive characteristics, nanoclay-enriched PCL fibrous scaffold may be used for musculoskeletal tissue engineering.