Induced Periosteum-Mimicking Membrane with Cell Barrier and Multipotential Stromal Cell (MSC) Homing Functionalities

The current management of critical size bone defects (CSBDs) remains challenging and requires multiple surgeries. To reduce the number of surgeries, wrapping a biodegradable fibrous membrane around the defect to contain the graft and carry biological stimulants for repair is highly desirable. Poly(ε-caprolactone) (PCL) can be utilised to realise nonwoven fibrous barrier-like structures through free surface electrospinning (FSE). Human periosteum and induced membrane (IM) samples informed the development of an FSE membrane to support platelet lysate (PL) absorption, multipotential stromal cells (MSC) growth, and the prevention of cell migration. Although thinner than IM, periosteum presented a more mature vascular system with a significantly larger blood vessel diameter. The electrospun membrane (PCL3%-E) exhibited randomly configured nanoscale fibres that were successfully customised to introduce pores of increased diameter, without compromising tensile properties. Additional to the PL absorption and release capabilities needed for MSC attraction and growth, PCL3%-E also provided a favourable surface for the proliferation and alignment of periosteum- and bone marrow derived-MSCs, whilst possessing a barrier function to cell migration. These results demonstrate the development of a promising biodegradable barrier membrane enabling PL release and MSC colonisation, two key functionalities needed for the in situ formation of a transitional periosteum-like structure, enabling movement towards single-surgery CSBD reconstruction.

Micro/Nano Multilayered Scaffolds of PLGA and Collagen by Alternately Electrospinning for Bone Tissue Engineering

The dual extrusion electrospinning technique was used to fabricate multilayered 3D scaffolds by stacking microfibrous meshes of poly(lactic acid-co-glycolic acid) (PLGA) in alternate fashion to micro/nano mixed fibrous meshes of PLGA and collagen. To fabricate the multilayered scaffold, 35 wt% solution of PLGA in THF-DMF binary solvent (3:1) and 5 wt% solution of collagen in hexafluoroisopropanol (HFIP) with and without hydroxyapatite nanorods (nHA) were used. The dual and individual electrospinning of PLGA and collagen were carried out at flow rates of 1.0 and 0.5 mL/h, respectively, at an applied voltage of 20 kV. The density of collagen fibers in multilayered scaffolds has controlled the adhesion, proliferation, and osteogenic differentiation of MC3T3-E1 cells. The homogeneous dispersion of glutamic acid-modified hydroxyapatite nanorods (nHA-GA) in collagen solution has improved the osteogenic properties of fabricated multilayered scaffolds. The fabricated multilayered scaffolds were characterized using FT-IR, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). The scanning electron microscopy (FE-SEM) was used to evaluate the adhesion and spreads of MC3T3-E1 cells on multilayered scaffolds. The activity of MC3T3-E1 cells on the multilayered scaffolds was evaluated by applying MTT, alkaline phosphatase, Alizarin Red, von Kossa, and cytoskeleton F-actin assaying protocols. The micro/nano fibrous PLGA-Col-HA scaffolds were found to be highly bioactive in comparison to pristine microfibrous PLGA and micro/nano mixed fibrous PLGA and Col scaffolds.

Graphene oxide-enriched poly(ε-caprolactone) electrospun nanocomposite scaffold for bone tissue engineering applications

Tissue engineering aims at fabricating biological substitutes to improve, repair, and regenerate failing human tissues or organs. Designing a nanocomposite scaffolds with tailored properties that enhance the development of functional tissue can be an appropriate approach to achieve this purpose. In this study, the uniform and bead-free nanofibers of poly(ε-caprolactone) composited with different graphene oxide nanosheet contents (ranging from 0.5 to 2 wt%) were successfully fabricated through electrospinning process. A decrease in the average diameter of poly(ε-caprolactone) nanofibers was observed with the addition of graphene oxide nanosheets. Moreover, the nanocomposite scaffolds containing 2 wt% of graphene oxide nanosheets exhibited superior mechanical properties compared to that of pure poly(ε-caprolactone). Compared with pure poly(ε-caprolactone) scaffold, the degradation rate of poly(ε-caprolactone)-graphene oxide nanosheet nanofibers was enhanced, while the integrity of fibers was preserved. The presence of graphene oxide nanosheets in poly(ε-caprolactone) fibers promoted in vitro biomineralization, indicating bioactive features of the nanocomposite scaffolds. Compared to the pure one, nanocomposite fibers also showed better ability in protein adsorption. The in vitro cell culture studies showed that the addition of graphene oxide nanosheets did not diminish the biocompatibility of the electrospun poly(ε-caprolactone) nanofiber. Furthermore, the adhesion and proliferation of MG63 cells were increased. Altogether, the results demonstrated that electrospun poly(ε-caprolactone)-graphene oxide nanosheet nanofiber may be a suitable candidate for tissue engineering scaffold applications.

Electrospun poly(butylene carbonate) membranes for guided bone regeneration: In vitro and in vivo studies

A nonwoven membrane for guided bone regeneration, constituting of poly(butylene carbonate), with a backbone that is similar to poly(ϵ-caprolactone), was prepared by electrospinning. The as-fabricated poly(butylene carbonate) membranes were to be used as guided bone regeneration membranes with efficacies equal to or better than poly(ϵ-caprolactone) membranes. The contact angles of electrospun poly(butylene carbonate) membranes (fPBC) (101.90 ± 4.19°) were lower than those for electrospun poly(ϵ-caprolactone) membranes (fPCL) (117.79 ± 3.38°) ( p < 0.01). To examine the biocompatibility, we investigated cell morphology, proliferation, and differentiation in vitro. The bone regenerative efficacy was evaluated in rat calvarial defect. The cell numbers were increased in accordance with culture period. Cells had a stellate shape and broad cytoplasmic extensions on the membrane. Alkaline phosphatase activity was significantly higher on fPBC than on fPCL ( p < 0.05). Defects covered by fPBC and fPCL achieved a similar degree of regeneration at 4 weeks in vivo and were significantly better than uncovered samples ( p < 0.01).Based on the results of this study, the potential for using electrospun poly(butylene carbonate) membranes in guided bone regeneration is highly significant . In addition, poly(butylene carbonate) could be a promising alternative to poly(ϵ-caprolactone) for biomedical applications.

In vitro and in vivo biocompatibility of multi-walled carbon nanotube/biodegradable polymer nanocomposite for bone defects repair

Biomaterials are extensively used in bone defect recovery caused by bone diseases. Multi-walled carbon nanotubes have been reported to reinforce synthetic polymeric materials. The aim of the study is to test poly(3-hydroxybutyrate- co-3-hydroxyvalerate) loaded with different amounts of multi-walled carbon nanotubes to fabricate nanocomposites. Mechanical, mineralization, and degradation properties were studied in vitro. The proliferation and differentiation of rat bone marrow stem cells were studied to determine biocompatibility in vivo. The incorporation of multi-walled carbon nanotubes greatly increased the mechanical properties of poly(3-hydroxybutyrate- co-3-hydroxyvalerate) and the strongest composite obtained was at 2% multi-walled carbon nanotubes. The 2% nanocomposite also had higher rat bone marrow stem cell adhesion, proliferation, and differentiation characteristics compared to the pure poly(3-hydroxybutyrate- co-3-hydroxyvalerate). The apoptosis in the later stage of rat bone marrow stem cells decreased in the 2% nanocomposites group at different time points. Based on histology and micro-computed tomography tests 6 weeks after in vivo implantation, the 2% multi-walled carbon nanotubes/poly(3-hydroxybutyrate- co-3-hydroxyvalerate) treated animals had a higher volume of bone formation compared to the pure poly(3-hydroxybutyrate- co-3-hydroxyvalerate) group. Thus, the presence of multi-walled carbon nanotubes has an apparent positive effect on poly(3-hydroxybutyrate- co-3-hydroxyvalerate) in assisting osteogenesis.

Antibiofilm activity of quercetin-encapsulated cytocompatible nanofibers against Candida albicans

In this study, nanofibers against pro dimorphic fungal sessile growth were developed. Quercetin was successfully encapsulated within poly(d,l-lactide- co-glycolide)–poly(ε-caprolactone) nanofibers using an electrospinning technique. Field emission scanning electron microscopy, fluorescent microscopy, and Fourier-transformed infrared spectrometer were used to confirm the formation as well as encapsulation of quercetin within the nanofibers. These fabricated nanofibers were further evaluated to determine the effectiveness of the antibiofilm activity against Candida albicans. The cytocompatibility of quercetin-encapsulated nanofibers was found to be similar to control and pure polymeric nanofibers based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay against human embryonic kidney (HEK-293) cell lines. These fabricated nanofibers potentially could be used as coatings on biomedical devices to inhibit microbial contaminations.

Trapping tetracycline-loaded nanoparticles into polycaprolactone fiber networks for periodontal regeneration therapy

The controlled delivery of antibiotics, anti-inflammatory agents, or chemotherapeutic agents to the periodontal site is a recognized strategy to improve the efficiency of regenerative processes of hard tissues. A novel approach based on the trapping of tetracycline hydrochloride–loaded particles in polycaprolactone nanofibers was used to guide the regeneration processes of periodontal tissue at the gum interface. Chitosan nanoparticles loaded with different levels of tetracycline hydrochloride (up to 5% wt) were prepared by solution nebulization induced by electrical forces (i.e. electrospraying). The fine tuning of process parameters allows to obtain nanoparticles with tailored sizes ranging from 0.485 ± 0.147 µm to 0.639 ± 0.154 µm. The tetracycline hydrochloride release profile had a predominant burst effect for the first 70% of release followed by a relatively slow release over 24 h, which is promising for oral drug delivery. We also demonstrated that trapping tetracycline hydrochloride–loaded particles with submicrometer diameters into a polycaprolactone fiber network contributed to slowing the release of tetracycline hydrochloride from the nanoparticles, thus providing a more prolonged release in the periodontal pocket during clinical therapy. Preliminary studies on human mesenchymal stem cells confirm the viability of cells up to 5 days after culture, and thereby, validate the use of nanoparticle-/nanofiber-integrated systems in periodontal therapies.

Electrospun poly(lactic-co-glycolic acid)/wool keratin fibrous composite scaffolds potential for bone tissue engineering applications

Biocomposite scaffolds consist of poly(lactic- co-glycolic acid) and wool keratin were obtained by an electrospinning process. Scanning electron microscopy images showed that the poly(lactic- co-glycolic acid)/wool keratin fibers had relatively rougher surfaces and smaller diameters. Thermogravimetric analysis showed higher thermal stabilities of the developed biocomposites compared to neat poly(lactic- co-glycolic acid). Mechanical tests showed that when the wool keratin content increased from 0% to 0.5% w/v, the tensile strength and elongation at break of the poly(lactic- co-glycolic acid)/0.5% wool keratin scaffolds increased with maxima of 6.59 MPa and 104.44%, respectively, which was an increase of 8.2% and 570% over the poly(lactic- co-glycolic acid) scaffold. The biological response of bone mesenchymal stem cells to the poly(lactic- co-glycolic acid)/1.5% wool keratin biocomposites was superior when compared to pure poly(lactic- co-glycolic acid) scaffold in terms of improved cell attachment and higher proliferation. These observations suggest that the addition of wool keratin to a poly(lactic- co-glycolic acid) matrix can improve several properties of the electrospun poly(lactic- co-glycolic acid) fibers, and the poly(lactic- co-glycolic acid)/wool keratin biocomposites could make excellent materials for tissue engineering applications.

Poly(d-lactide)/poly(caprolactone) nanofiber-thermogelling chitosan gel composite scaffolds for osteochondral tissue regeneration in a rat model

Macroporous nanostructured scaffolds that can be made to closely mimic skeletal tissue extracellular matrix as well as have the potential to support bone and cartilage tissue regeneration. Porous poly(d-lactide)/poly(caprolactone) nanofiber scaffolds were prepared by electrospinning respective polymer solutions along with salt crystals, which were sintered into fiber mats into cylindrical shape of 1.5 mm diameter and cut into 2–3 mm length followed by salt leaching in distilled water. The poly(d-lactide)/poly(caprolactone)–chitosan composite scaffolds were prepared by impregnating the porous structure of the electrospun scaffold with a thermosensitive chitosan solution. For in vivo evaluation, the scaffolds with and without chitosan gel were press fitted into osteochondral defects in a rat model. Hematoxylin and eosin staining 6 weeks post implantation showed new bone formation within the porous scaffolds with and without chitosan gel. Significant bone formation was observed within both the scaffolds at 15 weeks post implantation compared to the control group. The results show that macroporous poly(d-lactide)/poly(caprolactone) nanofiber scaffolds can be prepared with and without chitosan hydrogel and can serve as an osteochondral scaffold. The porous scaffolds showed the ability to promote new bone formation at the defect site, and incorporation of chitosan within the pores did not adversely affect the tissue in-growth. However, the scaffolds did not support significant cartilage formation even after 15 weeks, which indicates the need for the addition of cells or bioactive molecules within the scaffold to support effective osteochondral tissue regeneration.

Functionalization of electrospun poly(ε-caprolactone) scaffold with heparin and vascular endothelial growth factors for potential application as vascular grafts

In this study, a heparin-conjugated poly(ε-caprolactone) electrospun fiber was constructed to develop a functional scaffold for controlled release of vascular endothelial growth factors. The immobilization of vascular endothelial growth factor was achieved through affinity binding between heparin and vascular endothelial growth factor molecules. The sustained release of vascular endothelial growth factor from the scaffold was followed for up to 15 days. The endothelial cell adhesion and proliferation assay demonstrated that immobilized vascular endothelial growth factor maintained its activity. The blood compatibility of the scaffold was evaluated by activated partial thromboplastin time, platelet adhesion test, and arteriovenous shunt, and the functionalized scaffold showed improved anticoagulation properties. The biocompatibility was evaluated by subcutaneous implantation. Results showed that this vascular endothelial growth factor–releasing scaffold stimulated neovascularization with minimum immunological rejection compared to the unmodified poly(ε-caprolactone) scaffold. The present study demonstrated a new strategy of building bioactive scaffolds for the development of small-diameter vascular graft.

Mineralization of nanohydroxyapatite on electrospun poly(l-lactic acid)/gelatin by an alternate soaking process: A biomimetic scaffold for bone regeneration

Biomimetic nanocomposite scaffolds were fabricated by electrospinning poly(l-lactic acid) and a blend of poly(L-lactic acid)/gelatin to eliminate the use of collagen. The scaffolds were mineralized via alternate soaking in calcium and phosphate solutions, whereby 66.8% nanohydroxyapatite formation was successfully induced which is similar to that of native human bone (60%). The poly(L-lactic acid)/gelatin scaffolds had uniform nanohydroxyapatite formation throughout the scaffold. The mineralization enhanced the tensile modulus and tensile strength without increasing the brittleness. The in vitro biocompatibility of scaffolds was evaluated with murine adipose tissue–derived stem cells. The scaffolds with nanohydroxyapatite aided cell attachment and promoted cell–cell interaction. The mineralization and osteocalcin expression of the murine adipose tissue–derived stem cells were maximum in the poly(L-lactic acid)/gelatin/nanohydroxyapatite scaffold. Therefore, the gelatin and nanohydroxyapatite in poly(L-lactic acid)/gelatin/nanohydroxyapatite scaffolds provided cues for the differentiation of murine adipose tissue–derived stem cells. The biochemical nature of poly(L-lactic acid)/gelatin/nanohydroxyapatite scaffold accelerated osteogenic differentiation and could be a potential candidate for bone regeneration.