Design, clinical applications and post-surgical assessment of bioresorbable 3D-printed craniofacial composite implants

This study details the design, fabrication, clinical trials' evaluation, and analysis after the clinical application of 3D-printed bone reconstruction implants made of nHAp@PLDLLA [nanohydroxyapatite@poly(L-lactide-co-D,L-lactide)] biomaterial. The 3D-printed formulations have been tested as bone reconstruction Cranioimplants in 3 different medical cases, including frontal lobe, mandibular bone, and cleft palate reconstructions. Replacing one of the implants after 6 months provided a unique opportunity to evaluate the post-surgical implant obtained from a human patient. This allowed us to quantify physicochemical changes and develop a spatial map of osseointegration and material degradation kinetics as a function of specific locations. To the best of our knowledge, hydrolytic degradation and variability in the physicochemical and mechanical properties of the biomimetic, 3D-printed implants have not been quantified in the literature after permanent placement in the human body. Such analysis has revealed the constantly changing properties of the implant, which should be considered to optimize the design of patient-specific bone substitutes. Moreover, it has been proven that the obtained composition can produce biomimetic, bioresorbable and bone-forming alloplastic substitutes tailored to each patient, allowing for shorter surgery times and faster patient recovery than currently available methods.

A Study on the Effect of Doping Metallic Nanoparticles on Fracture Properties of Polylactic Acid Nanofibres via Molecular Dynamics Simulation

All-atom molecular dynamics simulations are conducted to elucidate the fracture mechanism of polylactic acid nanofibres doped with metallic nanoparticles. Extensional deformation is applied on polymer nanofibres decorated with spherical silver nanoparticles on the surface layer. In the obtained stress-strain curve, the elastic, yield, strain softening and fracture regions are recognized, where mechanical parameters are evaluated by tracking the stress, strain energy and geometrical evolutions. The energy release rate during crack propagation, which is a crucial factor in fracture mechanics, is calculated. The results show that the presence of doping nanoparticles improves the fracture properties of the polymer nanofibre consistently with experimental observation. The nanoparticles bind together polymer chains on the surface layer, which hinders crack initiation and propagation. The effect of the distribution of nanoparticles is studied through different doping decorations. Additionally, a discussion on the variation of internal energy components during uniaxial tensile loading is provided to unravel the deformation mechanism of nanoparticle-doped nanofibres.

A Study of Vanadate Group Substitution into Nanosized Hydroxyapatite Doped with Eu3+ Ions as a Potential Tissue Replacement Material

In this study, nanosized vanadate-substituted hydroxyapatites doped with 1 mol% and 2 mol% Eu3+ ions were obtained via the precipitation method. To evaluate the structure and morphology of the obtained compounds, the XRPD (X-ray powder diffraction) technique, Rietveld refinement, SEM-EDS (scanning electron microscopy-energy-dispersive spectrometry) and TEM (transmission electron microscopy) techniques as well as FTIR (Fourier transform infrared) spectroscopy were performed. Moreover, the chemical formula was confirmed using the ICP-OES (Inductively coupled plasma optical emission spectroscopy spectroscopy). The calculated average grain size for powders was in the range of 25 to 90 nm. The luminescence properties of vanadium-substituted hydroxyapatite were evaluated by recording emission spectra and excitation spectra as well as luminescence kinetics. The crucial step of this research was the evaluation of the biocompatibility of the synthesized nanomaterials. Therefore, the obtained compounds were tested toward sheep red blood cells and normal human dermal fibroblast to confirm the nontoxicity and biocompatibility of new nanosized Eu3+ ion-doped vanadate-hydroxyapatite. Moreover, the final step of the research allowed us to determine the time dependent ion release to the simulated body fluid environment. The study confirmed cytocompatibility of vanadium hydroxyapatite doped with Eu3+ ions.

Alginate-magnetic short nanofibers 3D composite hydrogel enhances the encapsulated human olfactory mucosa stem cells bioactivity for potential nerve regeneration application

The design of 3D hydrogel constructs to elicit highly controlled cell response is a major field of interest in developing tissue engineering. The bioactivity of encapsulated cells inside pure alginate hydrogel is limited by its relatively inertness. Combining short nanofibers within a hydrogel serves as a promising method to develop a cell friendly environment mimicking the extracellular matrix. In this paper, we fabricated alginate hydrogels incorporating different magnetic short nanofibers (M.SNFs) content for olfactory ecto-mesenchymal stem cells (OE-MSCs) encapsulation. Wet-electrospun gelatin and superparamagnetic iron oxide nanoparticles (SPIONs) nanocomposite nanofibers were chopped using sonication under optimized conditions and subsequently embedded in alginate hydrogels. The storage modulus of hydrogel without M.SNFs as well as with 1 and 5 mg/mL of M.SNFs were in the range of nerve tissue. For cell encapsulation, OE-MSCs were used as a new hope for neuronal regeneration due to their neural crest origin. Resazurin analyses and LIVE/DEAD staining confirmed that the composite hydrogels containing M.SNFs can preserve the cell viability after 7 days. Moreover, the proliferation rate was enhanced in M.SNF/hydrogels compared to alginate hydrogel. The presence of SPIONs in the short nanofibers can accelerate neural-like differentiation of OE-MSCs rather than the sample without SPIONs.

Collagen Scaffolds Containing Hydroxyapatite-CaO Fiber Fragments for Bone Tissue Engineering

Collagen (COL) and hydroxyapatite (HAp) are the major components of bone, therefore, COL-HAp composites have been widely used as bone substitutes to promote bone regeneration. We have reported that HAp-CaO fibers (HANFs), which were fabricated by a sol-gel route followed by an electrospinning technique, possessed good drug-loading efficiency and limited the burst release of tetracycline. In the present study, we used HANF fragments to evaluate the effects of COL-HANF scaffolds on MG63 osteoblast-like cell behaviors. COL-HANF composite scaffolds in which the average diameter of HANFs was approximately 461 ± 186 nm were fabricated by a freeze-drying process. The alkaline phosphatase activity and the protein expression levels of OCN and BSP showed that compared with COL alone, the COL-HANF scaffold promoted the differentiation of MG63 osteoblast-like cells. In addition, the bone regeneration ability of the COL-HANF scaffold was examined by using a rabbit condylar defect model in vivo. The COL-HANF scaffold was biodegradable and promoted bone regeneration eight weeks after the operation. Hence, we concluded that the COL-HANF scaffold has potential as a bone graft for bone tissue engineering.

Recent Advances in Bioplastics: Application and Biodegradation

The success of oil-based plastics and the continued growth of production and utilisation can be attributed to their cost, durability, strength to weight ratio, and eight contributions to the ease of everyday life. However, their mainly single use, durability and recalcitrant nature have led to a substantial increase of plastics as a fraction of municipal solid waste. The need to substitute single use products that are not easy to collect has inspired a lot of research towards finding sustainable replacements for oil-based plastics. In addition, specific physicochemical, biological, and degradation properties of biodegradable polymers have made them attractive materials for biomedical applications. This review summarises the advances in drug delivery systems, specifically design of nanoparticles based on the biodegradable polymers. We also discuss the research performed in the area of biophotonics and challenges and opportunities brought by the design and application of biodegradable polymers in tissue engineering. We then discuss state-of-the-art research in the design and application of biodegradable polymers in packaging and emphasise the advances in smart packaging development. Finally, we provide an overview of the biodegradation of these polymers and composites in managed and unmanaged environments.

Wireless implantable and biodegradable sensors for postsurgery monitoring: current status and future perspectives

In in vivo postsurgery monitoring, the use of wireless biodegradable implantable sensors has gained and is gaining a lot of interest, particularly in cases of monitoring for a short period of time. The employment of biodegradable materials allows the circumvention of secondary surgery for device removal. Additionally, the use of wireless communication for data elaboration avoids the need for transcutaneous wires. As such, it is possible to prevent possible inflammation and infections associated with long-term implants which are not wireless. It is expected that microfabricated biodegradable sensors will have a strong impact in acute or transient biomedical applications. However, the design of such high-performing electronic systems, both fully biodegradable and wireless, is very complex, particularly at small scales. The associated technologies are still in their infancy and should be more deeply and extensively investigated in animal models and, successively, in humans, before being clinically implemented. In this context, the present review aims to provide a complete overview of wireless biodegradable implantable sensors, covering the vital signs to be monitored, the wireless technologies involved, and the biodegradable materials used for the production of the devices, as well as designed devices and their applications. In particular, both their advantages and drawbacks are highlighted, and the key challenges faced, mainly associated with fabrication techniques, and control over degradation kinetics and biocompatibility of the device, are reported and discussed.

Surface modified electrospun poly(lactic acid) fibrous scaffold with cellulose nanofibrils and Ag nanoparticles for ocular cell proliferation and antimicrobial application

Corneal and conjunctival infections are common ocular diseases, sometimes, causing severe and refractory drug-resistant bacteria infections. Fungal keratitis is a leading cause for blindness and traditional medical treatment is unsatisfactory. Thus, there is an urge to develop a new therapy to deal with these cases. In this study, we developed surface modified poly(lactic acid) (PLA) electrospun nanofibrous membranes (EFMs) with silver nanoparticles (AgNPs) and cellulose nanofibrils (CNF) as scaffolds for cell proliferation and antimicrobial application. The AgNPs with a very low content (below 0.1%) were easily anchored on the surface of PLA EFMs by CNF, which endowed the scaffold with hydrophilicity and antibacterial ability. The in-vitro cell co-culture experiments showed that the scaffold had great biocompatibility to ocular epithelial cells, especially the scaffolds coated by CNF, which significantly proliferated cells. Furthermore, the antibacterial activity could reach >95% inhibiting Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) due to the implantation of AgNPs, and the antifungal activity was also outstanding with most of the Fusarium spp. inhibited. Hence, the developed PLA EFMs with CNF and AgNPs are promising ocular bandages to promote cell proliferation and kill infectious pathogens, exhibiting potential applications in ocular wound healing in the future.

Insight into Mechanobiology: How Stem Cells Feel Mechanical Forces and Orchestrate Biological Functions

The cross-talk between stem cells and their microenvironment has been shown to have a direct impact on stem cells' decisions about proliferation, growth, migration, and differentiation. It is well known that stem cells, tissues, organs, and whole organisms change their internal architecture and composition in response to external physical stimuli, thanks to cells' ability to sense mechanical signals and elicit selected biological functions. Likewise, stem cells play an active role in governing the composition and the architecture of their microenvironment. Is now being documented that, thanks to this dynamic relationship, stemness identity and stem cell functions are maintained. In this work, we review the current knowledge in mechanobiology on stem cells. We start with the description of theoretical basis of mechanobiology, continue with the effects of mechanical cues on stem cells, development, pathology, and regenerative medicine, and emphasize the contribution in the field of the development of ex-vivo mechanobiology modelling and computational tools, which allow for evaluating the role of forces on stem cell biology.

The Effect of Nanofillers on the Functional Properties of Biopolymer-based Films: A Review

Waste from non-degradable plastics is becoming an increasingly serious problem. Therefore, more and more research focuses on the development of materials with biodegradable properties. Bio-polymers are excellent raw materials for the production of such materials. Bio-based biopolymer films reinforced with nanostructures have become an interesting area of research. Nanocomposite films are a group of materials that mainly consist of bio-based natural (e.g., chitosan, starch) and synthetic (e.g., poly(lactic acid)) polymers and nanofillers (clay, organic, inorganic, or carbon nanostructures), with different properties. The interaction between environmentally friendly biopolymers and nanofillers leads to the improved functionality of nanocomposite materials. Depending on the properties of nanofillers, new or improved properties of nanocomposites can be obtained such as: barrier properties, improved mechanical strength, antimicrobial, and antioxidant properties or thermal stability. This review compiles information about biopolymers used as the matrix for the films with nanofillers as the active agents. Particular emphasis has been placed on the influence of nanofillers on functional properties of biopolymer films and their possible use within the food industry and food packaging systems. The possible applications of those nanocomposite films within other industries (medicine, drug and chemical industry, tissue engineering) is also briefly summarized.

Adipose Stem Cell Translational Applications: From Bench-to-Bedside

During the last five years, there has been a significantly increasing interest in adult adipose stem cells (ASCs) as a suitable tool for translational medicine applications. The abundant and renewable source of ASCs and the relatively simple procedure for cell isolation are only some of the reasons for this success. Here, we document the advances in the biology and in the innovative biotechnological applications of ASCs. We discuss how the multipotential property boosts ASCs toward mesenchymal and non-mesenchymal differentiation cell lineages and how their character is maintained even if they are combined with gene delivery systems and/or biomaterials, both in vitro and in vivo.

Recent Advances in Nanocomposites Based on Aliphatic Polyesters: Design, Synthesis, and Applications in Regenerative Medicine

In the last decade, biopolymer matrices reinforced with nanofillers have attracted great research efforts thanks to the synergistic characteristics derived from the combination of these two components. In this framework, this review focuses on the fundamental principles and recent progress in the field of aliphatic polyester-based nanocomposites for regenerative medicine applications. Traditional and emerging polymer nanocomposites are described in terms of polymer matrix properties and synthesis methods, used nanofillers, and nanocomposite processing and properties. Special attention has been paid to the most recent nanocomposite systems developed by combining alternative copolymerization strategies with specific nanoparticles. Thermal, electrical, biodegradation, and surface properties have been illustrated and correlated with the nanoparticle kind, content, and shape. Finally, cell-polymer (nanocomposite) interactions have been described by reviewing analysis methodologies such as primary and stem cell viability, adhesion, morphology, and differentiation processes.

Hydrogen Sulfide-Releasing Fibrous Membranes: Potential Patches for Stimulating Human Stem Cells Proliferation and Viability under Oxidative Stress

The design of biomaterial platforms able to release bioactive molecules is mandatory in tissue repair and regenerative medicine. In this context, electrospinning is a user-friendly, versatile and low-cost technique, able to process different kinds of materials in micro- and nano-fibers with a large surface area-to-volume ratio for an optimal release of gaseous signaling molecules. Recently, the antioxidant and anti-inflammatory properties of the endogenous gasotramsmitter hydrogen sulfide (H₂S), as well as its ability to stimulate relevant biochemical processes on the growth of mesenchymal stem cells (MSC), have been investigated. Therefore, in this work, new poly(lactic) acid fibrous membranes (PFM), doped and functionalized with H₂S slow-releasing donors extracted from garlic, were synthetized. These innovative H₂S-releasing mats were characterized for their morphological, thermal, mechanical, and biological properties. Their antimicrobial activity and effects on the in vitro human cardiac MSC growth, either in the presence or in the absence of oxidative stress, were here assessed. On the basis of the results here presented, these new H₂S-releasing PFM could represent promising and low-cost scaffolds or patches for biomedical applications in tissue repair.

Nanocomposites Based on Biodegradable Polymers

In the present review paper, our main results on nanocomposites based on biodegradable polymers (on a time scale from 2010 to 2018) are reported. We mainly focused our attention on commercial biodegradable polymers, which we mixed with different nanofillers and/or additives with the final aim of developing new materials with tunable specific properties. A wide list of nanofillers have been considered according to their shape, properties, and functionalization routes, and the results have been discussed looking at their roles on the basis of different adopted processing routes (solvent-based or melt-mixing processes). Two main application fields of nanocomposite based on biodegradable polymers have been considered: the specific interaction with stem cells in the regenerative medicine applications or as antimicrobial materials and the active role of selected nanofillers in food packaging applications have been critically revised, with the main aim of providing an overview of the authors' contribution to the state of the art in the field of biodegradable polymeric nanocomposites.

Eco-sustainable systems based on poly(lactic acid), diatomite and coffee grounds extract for food packaging

In the food packaging sector many efforts have been (and are) devoted to the development of new materials in order to reply to an urgent market demand for green and eco-sustainable products. Particularly a lot of attention is currently devoted both to the use of compostable and biobased polymers as innovative and promising alternative to the currently used petrochemical derived polymers, and to the re-use of waste materials coming from agriculture and food industry. In this work, multifunctional eco-sustainable systems, based on poly(lactic acid) (PLA) as biopolymeric matrix, diatomaceous earth as reinforcing filler and spent coffee grounds extract as oxygen scavenger, were produced for the first time, in order to provide a simultaneous improvement of mechanical and gas barrier properties. The influence of the diatomite and the spent coffee grounds extract on the microstructural, mechanical and oxygen barrier properties of the produced films was deeply investigated by means of X-Ray diffraction (XRD), infrared spectroscopy (FT-IR, ATR), scanning electron microscopy (SEM), uniaxial tensile tests, O₂ permeabilimetry measurements. An improvement of both mechanical and oxygen barrier properties was recorded for systems characterised by the co-presence of diatomite and coffee grounds extract, suggesting a possible synergic effect of the two additives.

Surface Hydrophilicity of Poly(l-Lactide) Acid Polymer Film Changes the Human Adult Adipose Stem Cell Architecture

Current knowledge indicates that the molecular cross-talk between stem cells and biomaterials guides the stem cells’ fate within a tissue engineering system. In this work, we have explored the effects of the interaction between the poly(l-lactide) acid (PLLA) polymer film and human adult adipose stem cells (hASCs), focusing on the events correlating the materials’ surface characteristics and the cells’ plasma membrane. hASCs were seeded on films of pristine PLLA polymer and on a PLLA surface modified by the radiofrequency plasma method under oxygen flow (PLLA+O₂). Comparative experiments were performed using human bone-marrow mesenchymal stem cells (hBM-MSCs) and human umbilical matrix stem cells (hUCMSCs). After treatment with oxygen-plasma, the surface of PLLA films became hydrophilic, whereas the bulk properties were not affected. hASCs cultured on pristine PLLA polymer films acquired a spheroid conformation. On the contrary, hASCs seeded on PLLA+O₂ film surface maintained the fibroblast-like morphology typically observed on tissue culture polystyrene. This suggests that the surface hydrophilicity is involved in the acquisition of the spheroid conformation. Noteworthy, the oxygen treatment had no effects on hBM-MSC and hUCMSC cultures and both stem cells maintained the same shape observed on PLLA films. This different behavior suggests that the biomaterial-interaction is stem cell specific.

Calcium Orthophosphate-Containing Biocomposites and Hybrid Biomaterials for Biomedical Applications

The state-of-the-art on calcium orthophosphate (CaPO4)-containing biocomposites and hybrid biomaterials suitable for biomedical applications is presented. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through the successful combinations of the desired properties of matrix materials with those of fillers (in such systems, CaPO4 might play either role), innovative bone graft biomaterials can be designed. Various types of CaPO4-based biocomposites and hybrid biomaterials those are either already in use or being investigated for biomedical applications are extensively discussed. Many different formulations in terms of the material constituents, fabrication technologies, structural and bioactive properties, as well as both in vitro and in vivo characteristics have been already proposed. Among the others, the nano-structurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin, as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using CaPO4-based biocomposites and hybrid biomaterials in the selected applications are highlighted. As the way from a laboratory to a hospital is a long one and the prospective biomedical candidates have to meet many different necessities, the critical issues and scientific challenges that require further research and development are also examined.

Electrospun antibacterial nanofibrous polyvinylpyrrolidone/cetyltrimethylammonium bromide membranes for biomedical applications

Nanoscale structures with large surface area-to-volume ratios are used as biomaterial scaffolds for vascular grafts, wound dressings, and air purifying filters. Using electrospinning, nanofibers containing an antibacterial agent, cetyltrimethylammonium bromide, were prepared for wound healing application. Polyvinylpyrrolidone, known as a biocompatible additive in food and drug industries, has been used as fiber processing agent with the organic active ingredient, cetyltrimethylammonium bromide. A series of samples with different polyvinylpyrrolidone/ cetyltrimethylammonium bromide ratios were successfully prepared by this method. The morphology and electroactive characteristics of nanofibers were investigated using scanning electron microscopy, atomic force microscopy, and electrochemical impedance spectroscopy. Fiber diameters and charge transfer resistances were found to decrease with salt content, while the double-layer capacitance increased with no apparent effect on the specific capacitance providing favorable conditions for the fabrication of biomaterials. In addition, the quaternary ammonium compound (cetyltrimethylammonium bromide) with a minimum ratio of 2.5 wt% showed reduction in bacterial activity of Klebsiella pneumonia, Staphylococcus aureus, and Escherichia coli.

Combination of silica nanoparticles with hydroxyapatite reinforces poly (l-lactide acid) scaffolds without loss of bioactivity

Composite scaffolds of poly(l-lactide acid) and hydroxyapatite are of great interest in bone tissue engineering, but their mechanical properties are typically inferior to scaffolds of pure poly(l-lactide acid) due to agglomeration of the particles and weak interfacial component interaction. Fabrication strategies like double sonication of hydroxyapatite or increasing the amount of this inorganic filler do not effectively enhance the mechanical performance. In this study, poly(l-lactide acid) composites combining two types of fillers, mesoporous silica (SiO2) nanoparticles and hydroxyapatite, were developed to reinforce the poly(l-lactide acid) scaffold without any loss of bioactivity. A 5% addition of SiO2 nanoparticles to hydroxyapatite nanopowder and subjecting the scaffold formulation to double sonication increased the Young’s modulus from 5 MPa (pure poly(l-lactide acid) scaffold) to almost 7 MPa (poly(l-lactide acid)/hydroxyapatite/SiO2 scaffold). In addition, the composite was able to deposit a layer of biomimetic hydroxyapatite both on the surface and interior of the scaffold after 21 days of immersion in a simulated body fluid. The manufacturing method was straightforward and economically viable and does not require any chemical modification of the particles’ surfaces.

Effect of silver nanoparticles and cellulose nanocrystals on electrospun poly(lactic) acid mats: morphology, thermal properties and mechanical behavior

The fabrication of ternary fibrous mats based on poly(lactic) acid (PLA), cellulose nanocrystals (CNCs, both pristine (p-CNCs) and modified with a commercial surfactant (s-CNCs)) and silver (Ag) nanoparticles by electrospinning is reported. Amounts of 1 and 5 wt.% were selected for Ag and CNCs, respectively. Neat PLA and binary PLA/Ag, PLA/p-CNCs and PLA/s-CNCs were produced as references. The CNCs and Ag influence on the microstructural, thermal and mechanical properties was investigated. The Ag and/or p-CNCs addition did not remarkably affect fiber morphology and average size dimension (between (468 ± 111) and (551 ± 122)nm), whereas the s-CNCs presence led to the deposition of a honeycomb-like network on a underneath layer of randomly oriented fibers. The efficiency of the surfactant use in promoting the CNC dispersion was demonstrated. A slight enhancement (e.g. around 25%, in terms of strength) of the mechanical properties of p-CNCs loaded fibers, particularly for PLA/Ag/p-CNCs, was revealed, whereas mats with s-CNCs showed a decrement (e.g. around 35-45%, in terms of strength), mainly imputable to the delamination between the upper honeycomb-like layer and the lower conventional fibrous mat.

Fibrous star poly(ε-caprolactone) melt-electrospun scaffolds for wound healing applications

Polymeric fibrous scaffolds based on the biocompatible and biodegradable three-arm-branched star poly(ε-caprolactone) (Mw = 189,000 g/mol) were prepared by a melt electrospinning technique. The possibility of processing polymers without the use of organic solvents is one of the main advantages over solution electrospinning. Scaffolds were biologically tested for their ability of supporting skin tissue regeneration. For this purpose, mouse embryo fibroblast (BALB/3T3 clone A31) and human keratinocyte (HaCaT) cell lines were selected as models, and seeded onto the polymeric supports both as single and co-culture. Cell viability, proliferation, and collagen production were assessed by WST-1 assay and Direct Red 80 dye, respectively. Cell morphology and colonization of the supports were evaluated by scanning electron microscopy and confocal laser scanning microscopy. Results highlighted that the star poly(ε-caprolactone) scaffolds were able to promote collagen production by fibroblasts. In co-culture studies, scaffolds supported adhesion, proliferation, and spatial organization of both cell lines. By virtue of the observed results, the developed polymeric scaffolds appeared suitable as biodegradable and biocompatible three-dimensional supports for skin tissue regeneration in wound healing dressing.

Additive manufacturing of star poly(ε-caprolactone) wet-spun scaffolds for bone tissue engineering applications

Three-dimensional fibrous scaffolds made of a three-arm star poly(ε-caprolactone) were developed by employing a novel computer-aided wet-spinning apparatus to precisely control the deposition pattern of an extruded polymeric solution as a filament into a coagulation bath. Star poly(ε-caprolactone)/hydroxyapatite composite scaffolds composed of fibres with a porous morphology both in the outer surface and in the cross section were successfully produced with a layer-by-layer approach achieving good reproducibility of the internal architecture and external shape. Changes in processing parameters were used to fabricate scaffolds with different architectural parameters in terms of average pore size in the xy-axes (from 190 to 297 µm) and in the z-axis (from 54 to 126 µm) and porosity (in the range of 20%–60%). Based on the mechanical characterization, processing variations and hydroxyapatite loading have an influence on scaffold compression properties. Cell cultures, using a murine pre-osteoblast cell line, had good cell responses in terms of proliferation and osteoblastic differentiation. Thus, this technique appears to be an effective method for producing customized polymeric scaffolds for bone tissue engineering applications.

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.

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.

Electrospun PHBV/PEO co-solution blends: microstructure, thermal and mechanical properties

Blending allows to tailor and modulate the properties of selected polymers. Blends of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polyethylene oxide (PEO) were fabricated by electrospinning in different weight ratios i.e. 100:0, 80:20, 70:30, 50:50, 0:100. In order to evaluate the influence of PEO addition on the final properties of PHBV, a complete microstructural, thermal and mechanical characterization of PHBV/PEO blends has been performed. The two neat polymeric membranes were also considered for the sake of comparison. The following characterization techniques were employed: scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy, simultaneous thermogravimetric and differential analyses (TG-DTA), differential scanning calorimetry (DSC), and uniaxial tensile tests. All electrospun mats consisted of randomly oriented and uniform fibers. It has been observed that the microstructure of PHBV/PEO was remarkably affected by blend composition. The average fiber size ranged between 0.5 μm and 2.6 μm. It resulted that the electrospun polymeric blends consisted of separate crystalline domains associated to an amorphous interdisperse phase. PHBV/PEO blends presented intermediate mechanical properties, in terms of tensile modulus and ultimate tensile stress, with respect to the two neat components.

Membranes of poly(dl-lactic acid)/Bioglass® with asymmetric bioactivity for biomedical applications

In guided tissue/bone regeneration, membranes are used as barriers to prevent the faster growing soft tissue cells from entering the defect space and to regenerate periodontal ligament, cementum, and bone. The two sides of the membranes are in contact with distinct biological environments in which one faces a region in which osteointegration should be ideally promoted. Biocompatible and biodegradable composite membranes were produced by combining poly(d,l-lactic acid) and Bioglass® particles featuring an asymmetric bioactivity and a good integration between the polymeric and inorganic fractions. The asymmetric distribution of the osteoconductive particles was produced during the processing of the membrane using a solvent casting methodology. Only the inorganic-rich face promoted the deposition of bone-like apatite after immersing the composite membrane in simulated body fluid for 2 days. The mechanical properties of the membranes were evaluated using dynamic mechanical analysis by analyzing the viscoelastic properties and the glass transition of the samples in both dry and wet states. A clear plasticization effect of water was detected, but the composite membranes were found to be stiffer, at 37ºC, compared with the pure polymer. SaOs-2 cells attached on both the surfaces and proliferated after 7 days in culture.

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.

Tuning multi/pluri-potent stem cell fate by electrospun poly(L-lactic acid)-calcium-deficient hydroxyapatite nanocomposite mats

In this study, we investigated whether multipotent (human-bone-marrow-derived mesenchymal stem cells [hBM-MSCs]) and pluripotent stem cells (murine-induced pluripotent stem cells [iPSCs] and murine embryonic stem cells [ESCs]) respond to nanocomposite fibrous mats of poly(L-lactic acid) (PLLA) loaded with 1 or 8 wt % of calcium-deficient nanohydroxyapatite (d-HAp). Remarkably, the dispersion of different amounts of d-HAp to PLLA produced a set of materials (PLLA/d-HAp) with similar architectures and tunable mechanical properties. After 3 weeks of culture in the absence of soluble osteogenic factors, we observed the expression of osteogenic markers, including the deposition of bone matrix proteins, in multi/pluripotent cells only grown on PLLA/d-HAp nanocomposites, whereas the osteogenic differentiation was absent on stem-cell-neat PLLA cultures. Interestingly, this phenomenon was confined only in hBM-MSCs, murine iPSCs, and ESCs grown on direct contact with the PLLA/d-HAp mats. Altogether, these results indicate that the osteogenic differentiation effect of these electrospun PLLA/d-HAp nanocomposites was independent of the stem cell type and highlight the direct interaction of stem cell-polymeric nanocomposite and the mechanical properties acquired by the PLLA/d-HAp nanocomposites as key steps for the differentiation process.

Nanofibrous electrospun barrier membrane promotes osteogenic differentiation of human mesenchymal stem cells

An electrospun polysulfone (PSU) was prepared as a barrier membrane for guided bone regeneration. The membrane was in nanoscale to prevent fibrous tissue infiltration and highly porous to allow permeation of oxygen and nutrients. The morphology and attachment, viability and proliferation, and differentiation and mineralization of human bone marrow mesenchymal stem cells (HBMSCs) were determined. Cells adhered and spread well on the PSU membrane with characteristic polygonal, fusiform shapes and radial extensions. The live/dead staining revealed that the membrane had no negative influence on cell viability. The proliferation rates of HBMSCs on PSU membranes were lower in comparison with tissue-culture polystyrene plate after 3 days of culture. However, differentiation activity was particularly expressed at high levels when cells were cultured on PSU membranes. The results based on the data suggest that the PSU electrospun membrane promoted the osteogenic differentiation of HBMSCs, displayed desirable in vitro biocompatibility, and has good potential as a barrier membrane.

Effects of electrospinning parameters on morphology and diameter of electrospun PLGA/MWNTs fibers and cytocompatibility in vitro

Poly(lactic- co-glycolic acid) (PLGA)/multiwalled carbon nanotubes (MWNTs) composite fiber mats were prepared by electrospinning and gas-jet/electrospinning. The morphology and diameter of the electrospun PLGA/MWNTs fibers were tailored by controlling process parameters; smooth and uniform PLGA/MWNTs fibers were obtained by using the following optimized process parameters, 25 wt% PLGA concentrations, 0.25% w/v MWNTs contents, 20 kV applied voltage, 13 cm tip-to-collector distances, 0.27 mm inner diameters, and 0.2 mL/min feeding rates. The cytocompatibility of the PLGA/MWNTs fibers prepared by optimizing process parameters was evaluated using rat bone marrow-derived mesenchymal stem cells. Good-quality cell attachment and characteristic cell morphology were observed on the fibers. The PLGA/MWNTs fiber mats, fabricated by electrospinning, indicate excellent potential for bone tissue engineering applications, particularly as scaffolds for bone tissue regeneration.