PHB Scaffolds Research Articles

Osteogenic Potential and Long-Term Enzymatic Biodegradation of PHB-based Scaffolds with Composite Magnetic Nanofillers in a Magnetic Field.

Millions of people worldwide suffer from musculoskeletal damage, thus using the largest proportion of rehabilitation services. The limited self-regenerative capacity of bone and cartilage tissues necessitates the development of functional biomaterials. Magnetoactive materials are a promising solution due to clinical safety and deep tissue penetration of magnetic fields (MFs) without attenuation and tissue heating. Herein, electrospun microfibrous scaffolds were developed based on piezoelectric poly(3-hydroxybutyrate) (PHB) and composite magnetic nanofillers [magnetite with graphene oxide (GO) or reduced GO]. The scaffolds' morphology, structure, mechanical properties, surface potential, and piezoelectric response were systematically investigated. Furthermore, a complex mechanism of enzymatic biodegradation of these scaffolds is proposed that involves (i) a release of polymer crystallites, (ii) crystallization of the amorphous phase, and (iii) dissolution of the amorphous phase. Incorporation of Fe3O4, Fe3O4-GO, or Fe3O4-rGO accelerated the biodegradation of PHB scaffolds owing to pores on the surface of composite fibers and the enlarged content of polymer amorphous phase in the composite scaffolds. Six-month biodegradation caused a reduction in surface potential (1.5-fold) and in a vertical piezoresponse (3.5-fold) of the Fe3O4-GO scaffold because of a decrease in the PHB β-phase content. In vitro assays in the absence of an MF showed a significantly more pronounced mesenchymal stem cell proliferation on composite magnetic scaffolds compared to the neat scaffold, whereas in an MF (68 mT, 0.67 Hz), cell proliferation was not statistically significantly different when all the studied scaffolds were compared. The PHB/Fe3O4-GO scaffold was implanted into femur bone defects in rats, resulting in successful bone repair after nonperiodic magnetic stimulation (200 mT, 0.04 Hz) owing to a synergetic influence of increased surface roughness, the presence of hydrophilic groups near the surface, and magnetoelectric and magnetomechanical effects of the material.

Production of PHB Scaffolds Reinforced with HAp Through Electrospinning

Production of PHB Scaffolds Reinforced with HAp Through Electrospinning

Biological evaluation and osteogenic potential of polyhydroxybutyrate-keratin/Al2O3 electrospun nanocomposite scaffold: A novel bone regeneration construct

In this study, the effect of alumina nanowire on the physical and biological properties of polyhydroxybutyrate-keratin (PHB-K) electrospun scaffold was investigated. First, PHB-K/alumina nanowire nanocomposite scaffolds were made with an optimal concentration of 3 wt% alumina nanowire by using the electrospinning method. The samples were examined in terms of morphology, porosity, tensile strength, contact angle, biodegradability, bioactivity, cell viability, ALP activity, mineralization ability, and gene expression. The nanocomposite scaffold provided a porosity of >80 % and a tensile strength of about 6.72 MPa, which were noticeable for an electrospun scaffold. AFM images showed an increase in surface roughness with the presence of alumina nanowires. This led to an improvement in the degradation rate and bioactivity of PHB-K/alumina nanowire scaffolds. The viability of mesenchymal cells, alkaline phosphatase secretion, and mineralization significantly increased with the presence of alumina nanowire compared to PHB and PHB-K scaffolds. In addition, the expression level of collagen I, osteocalcin, and RUNX2 genes in nanocomposite scaffolds increased significantly compared to other groups. In general, this nanocomposite scaffold could be a novel and interesting construct for osteogenic induction in bone tissue engineering.

Investigating of physical, mechanical, and biological properties of polyhydroxybutyrate-keratin/alumina electrospun scaffold utilized in bone tissue engineering

Electrospun nanofiber scaffolds have a similar structure to extracellular matrix, leading to increased cell adhesion, proliferation, and migration. In this study, 1–5wt % of alumina nanowires were added to polyhydroxybutyrate-keratin (PHB–K) solution, and the morphology of the electrospun scaffolds in terms of fiber diameter, porosity percentage, and the uniformity of the alumina nanowires distribution was evaluated by SEM. FTIR and raman tests were also used to evaluate the chemical bonds of nanofibers and the presence of alumina and keratin in electrospun scaffolds. The crystallinity of the scaffolds was also measured using DSC and confirmed by XRD. The increase of alumina augmented the crystallinity of scaffolds because alumina is a nucleating agent. The tensile strength of PHB-K scaffolds increased up to 3 fold in the presence of 3 wt % of alumina.The MG63 cells survived, and the secretion of alkaline phosphatase and mineralization due to the presence of alumina was significantly higher than PHB and PHB-K scaffolds. Based on the results, the electrospun PHB-K/AL2O3 scaffolds are potential candidates for bone tissue engineering.

Cell Behavior Changes and Enzymatic Biodegradation of Hybrid Electrospun Poly(3-hydroxybutyrate)-Based Scaffolds with an Enhanced Piezoresponse after the Addition of Reduced Graphene Oxide.

This is the first comprehensive study of the impact of biodegradation on the structure, surface potential, mechanical and piezoelectric properties of poly(3-hydroxybutyrate) (PHB) scaffolds supplemented with reduced graphene oxide (rGO) as well as cell behavior under static and dynamic mechanical conditions. There is no effect of the rGO addition up to 1.0 wt% on the rate of enzymatic biodegradation of PHB scaffolds for 30 d. The biodegradation of scaffolds leads to the depolymerization of the amorphous phase, resulting in an increase in the degree of crystallinity. Because of more regular dipole order in the crystalline phase, surface potential of all fibers increases after the biodegradation, with a maximum (361 ± 5mV) after the addition of 1 wt% rGO into PHB as compared to pristine PHB fibers. By contrast, PHB-0.7rGO fibers manifest the strongest effective vertical (0.59 ± 0.03 pm V-1 ) and lateral (1.06 ± 0.02 pm V-1 ) piezoresponse owing to a greater presence of electroactive β-phase. In vitro assays involving primary human fibroblasts reveal equal biocompatibility and faster cell proliferation on PHB-0.7rGO scaffolds compared to pure PHB and nonpiezoelectric polycaprolactone scaffolds. Thus, the developed biodegradable PHB-rGO scaffolds with enhanced piezoresponse are promising for tissue-engineering applications.

Effects of decellularized extracellular matrix on Polyhydroxybutyrate electrospun scaffolds for cartilage tissue engineering

ABSTRACT The current study was carried out to evaluate the effects of cartilage-decellularized extracellular matrix (ECM) on Poly (3-hydroxybutyrate) (PHB) electrospun scaffold for cartilage tissue engineering. In this study, PHB scaffolds with three different percentages of ECM (1%, 2%, and 3%) were fabricated. Mechanical, chemical, and physical properties of scaffolds along with their interactions with cells were assessed. Results showed that by adding of ECM to the scaffolds, the Physiomechanical properties of combined scaffolds were modified, compared to the pure PHB scaffold. In the other hand, the biological behavior was increased by increasing the ECM ratio to the PHB.

Comprehensive Study on the Reinforcement of Electrospun PHB Scaffolds with Composite Magnetic Fe3O4-rGO Fillers: Structure, Physico-Mechanical Properties, and Piezoelectric Response.

This is a comprehensive study on the reinforcement of electrospun poly(3-hydroxybutyrate) (PHB) scaffolds with a composite filler of magnetite-reduced graphene oxide (Fe3O4-rGO). The composite filler promoted the increase of average fiber diameters and decrease of the degree of crystallinity of hybrid scaffolds. The decrease in the fiber diameter enhanced the ductility and mechanical strength of scaffolds. The surface electric potential of PHB/Fe3O4-rGO composite scaffolds significantly increased with increasing fiber diameter owing to a greater number of polar functional groups. The changes in the microfiber diameter did not have any influence on effective piezoresponses of composite scaffolds. The Fe3O4-rGO filler imparted high saturation magnetization (6.67 ± 0.17 emu/g) to the scaffolds. Thus, magnetic PHB/Fe3O4-rGO composite scaffolds both preserve magnetic properties and provide a piezoresponse, whereas varying the fiber diameter offers control over ductility and surface electric potential.

Electrospun composites of poly-3-hydroxybutyrate reinforced with conductive fillers for in vivo bone regeneration

The aim of this study was to investigate the biocompatibility and osteoinductive properties of fibrous scaffolds implanted in the bone tissue of white rats in vivo. The effect of various concentrations of conductive PANi (2 and 3 wt%) and rGO (0.2 and 1 wt%) in the PHB scaffolds on the reparative processes of bone callus formation in white rats was studied. On the 28th day after implantation, a histomorphological study of the preparations of the transverse section of the diaphysis of the femur of the implantation area was performed. The results of implantation tests in the femur revealed that all the studied scaffolds are biocompatible and the most pronounced stimulating effect on bone formation was observed for hybrid PHB scaffolds doped with 3 wt% PANi and 0.2 wt% rGO compared with pure PHB scaffolds, thus determining further prospects to study the osteoinductive features of hybrid PHB scaffolds.

Core-Shell Magnetoactive PHB/Gelatin/Magnetite Composite Electrospun Scaffolds for Biomedical Applications.

Novel hybrid magnetoactive composite scaffolds based on poly(3-hydroxybutyrate) (PHB), gelatin, and magnetite (Fe3O4) were fabricated by electrospinning. The morphology, structure, phase composition, and magnetic properties of composite scaffolds were studied. Fabrication procedures of PHB/gelatin and PHB/gelatin/Fe3O4 scaffolds resulted in the formation of both core-shell and ribbon-shaped structure of the fibers. In case of hybrid PHB/gelatin/Fe3O4 scaffolds submicron-sized Fe3O4 particles were observed in the surface layers of the fibers. The X-ray photoelectron spectroscopy results allowed the presence of gelatin on the fiber surface (N/C ratio–0.11) to be revealed. Incubation of the composite scaffolds in saline for 3 h decreased the amount of gelatin on the surface by more than ~75%. The differential scanning calorimetry results obtained for pure PHB scaffolds revealed a characteristic melting peak at 177.5 °C. The presence of gelatin in PHB/gelatin and PHB/gelatin/Fe3O4 scaffolds resulted in the decrease in melting temperature to 168–169 °C in comparison with pure PHB scaffolds due to the core-shell structure of the fibers. Hybrid scaffolds also demonstrated a decrease in crystallinity from 52.3% (PHB) to 16.9% (PHB/gelatin) and 9.2% (PHB/gelatin/Fe3O4). All the prepared scaffolds were non-toxic and saturation magnetization of the composite scaffolds with magnetite was 3.27 ± 0.22 emu/g, which makes them prospective candidates for usage in biomedical applications.

Novel electrospun poly-hydroxybutyrate scaffolds as carriers for the wound healing agents alkannins and shikonins.

The aim of this study was to investigate the potential of novel electrospun fiber mats loaded with alkannin and shikonin (A/S) derivatives, using as carrier a highly biocompatible, bio-derived, eco-friendly polymer such as poly[(R)-3-hydroxybutyric acid] (PHB). PHB fibers containing a mixture of A/S derivatives at different ratios were successfully fabricated via electrospinning. Αs evidenced by scanning electron microscopy, the fibers formed a bead-free mesh with average diameters from 1.25 to 1.47 μm. Spectroscopic measurements suggest that electrospinning marginally increases the amorphous content of the predominantly crystalline PHB in the fibers, while a significant drug amount lies near the fiber surface for samples of high total A/S content. All scaffolds displayed satisfactory characteristics, with the lower concentrations of A/S mixture-loaded PHB fiber mats achieving higher porosity, water uptake ratios, and entrapment efficiencies. The in vitro dissolution studies revealed that all samples released more than 70% of the encapsulated drug after 72 h. All PHB scaffolds tested by cell viability assay were proven non-toxic for Hs27 fibroblasts, with the 0.15 wt.% sample favoring cell attachment, spreading onto the scaffold surface, as well as cell proliferation. Finally, the antimicrobial activity of PHB meshes loaded with A/S mixture was documented for Staphylococcus epidermidis and S. aureus.

The Influence of Microstructure in PHB Non‐Woven Materials on Mechanical Behavior Under Tension

AbstractThis work focuses on the study of mechanical behavior of non‐woven scaffolds under tensile. The results are obtained in poly(3‐hydroxybutyrate) (PHB) scaffolds prepared by two technological approaches and various PHB concentration in molding solutions. The technological solutions provide electrospun fibrous structures with various fiber morphologies, which cause significant differences in the physico‐mechanical properties of non‐woven materials. Tensile strength of produced PHB scaffolds with different porosity and geometry of fibrous layer is in the range of 0.1 to 1.3 MPa and elongation at break from 3% to 9%. To visualize the evolution of the microstructure during tensile, optic microscopy and high‐frequency acoustic microscopy are applied.

Porous Poly(3-hydroxybutyrate) Scaffolds Prepared by Non-Solvent-Induced Phase Separation for Tissue Engineering.

Highly porous poly(3-hydroxybutyrate) (PHB) scaffolds were fabricated using non-solvent-induced phase separation with chloroform as the solvent and tetrahydrofuran as the non-solvent. The microporosity, nanofiber morphology, and mechanical strength of the scaffolds were adjusted by varying the fabrication parameters, such as the polymer concentration and solvent composition. The influence of these parameters on the structure and morphology of PHB organogels and scaffolds was elucidated using small-angle neutron scattering and scanning electron microscopy. The organogels and scaffolds in this study have a complex hierarchical structure, extending over a wide range of length scales. In vitro viability assays were performed using the human keratinocyte cell line (HaCaT), and all PHB scaffolds demonstrated the excellent cell viability. Microporosity had the greatest impact on HaCaT cell proliferation on PHB scaffolds, which was determined after a 3-day incubation period with scaffolds of different morphologies and mechanical properties. The superior cell viability and the controlled scaffold properties and morphologies suggested PHB scaffolds fabricated by non-solvent-induced phase separation using chloroform and tetrahydrofuran as promising biomaterials for the applications of tissue engineering, particularly of epidermal engineering.Electronic Supplementary MaterialSupplementary material is available in the online version of this article at 10.1007/s13233-020-8109-x.

Drug Release Kinetics of Electrospun PHB Meshes.

Microbial poly(3-hydroxybutyrate) (PHB) has several advantages including its biocompatibility and ability to degrade in vivo and in vitro without toxic substances. This paper investigates the feasibility of electrospun PHB meshes serving as drug delivery systems. The morphology of the electrospun samples was modified by varying the concentration of PHB in solution and the solvent composition. Scanning electron microscopy of the electrospun PHB scaffolds revealed the formation of different morphologies including porous, filamentous/beaded and fiber structures. Levofloxacin was used as the model drug for incorporation into PHB electrospun meshes. The entrapment efficiency was found to be dependent on the viscosity of the PHB solution used for electrospinning and ranged from 14.4–81.8%. The incorporation of levofloxacin in electrospun meshes was confirmed by Fourier-transform infrared spectroscopy and UV-VIS spectroscopy. The effect of the morphology of the electrospun meshes on the levofloxacin release profile was screened in vitro in phosphate-buffered saline solution. Depending upon the morphology, the electrospun meshes released about 14–20% of levofloxacin during the first 24 h. The percentage of drug released after 13 days increased up to 32.4% and was similar for all tested morphologies. The antimicrobial efficiency of all tested samples independent of the morphology, was confirmed by agar diffusion testing.

Enhanced piezoelectric response of hybrid biodegradable 3D poly(3-hydroxybutyrate) scaffolds coated with hydrothermally deposited ZnO for biomedical applications

Fibrous scaffolds based on biodegradable piezoelectric poly(3-hydroxybutyrate) (PHB) polymers were fabricated via electrospinning. Hydrothermal deposition of zinc oxide (ZnO) on the surfaces of fibrous PHB scaffolds resulted in a homogeneous ZnO layer that grew conformally on the porous polymeric scaffold. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results confirmed the formation of a hexagonal wurtzite crystal structure of ZnO on the PHB fibres. XRD patterns, TEM and EDS analysis revealed a bimodal morphology with rod-like nanostructures that grew preferentially along the c-axis as well as nanoparticles that grew randomly. The piezoelectric charge coefficient d33 for pristine PHB scaffolds was 2.9 ± 0.1 pC⋅N−1, whereas after ZnO deposition, it substantially increased to 13.7 ± 1.6 pC⋅N−1. Moreover, the output surface electrical potential of PHB scaffolds after ZnO deposition also substantially increased from 0.58 ± 0.02 to 0.88 ± 0.04 V, showing enhanced electromechanical coupling in the piezoelectric nanocomposites. The output surface electric potential for ZnO-coated PHB scaffolds was stable within 1200 loading cycles. In addition, the ZnO rod-like nanostructured surface improved the wettability of PHB fibrous scaffolds, demonstrating synergy between the ceramic and polymeric phases in PHB/ZnO composites. Therefore, the hybrid biodegradable piezoelectric scaffolds reported in the present study are potentially useful for biomedical applications, where both improved piezoelectric response and surface wettability are required.

Piezoelectric 3-D Fibrous Poly(3-hydroxybutyrate)-Based Scaffolds Ultrasound-Mineralized with Calcium Carbonate for Bone Tissue Engineering: Inorganic Phase Formation, Osteoblast Cell Adhesion, and Proliferation.

Elaboration of novel biocomposites providing simultaneously both biodegradability and stimulated bone tissue repair is essential for regenerative medicine. In particular, piezoelectric biocomposites are attractive because of a possibility to electrically stimulate cell response. In the present study, novel CaCO3-mineralized piezoelectric biodegradable scaffolds based on two polymers, poly[( R)3-hydroxybutyrate] (PHB) and poly[3-hydroxybutyrate- co-3-hydroxyvalerate] (PHBV), are presented. Mineralization of the scaffold surface is carried out by the in situ synthesis of CaCO3 in the vaterite and calcite polymorphs using ultrasound (U/S). Comparative characterization of PHB and PHBV scaffolds demonstrated an impact of the porosity and surface charge on the mineralization in a dynamic mechanical system, as no essential distinction was observed in wettability, structure, and surface chemical compositions. A significantly higher (4.3 times) piezoelectric charge and a higher porosity (∼15%) lead to a more homogenous CaCO3 growth in 3-D fibrous structures and result in a two times higher relative mass increase for PHB scaffolds compared to that for PHBV. This also increases the local ion concentration incurred upon mineralization under U/S-generated dynamic mechanical conditions. The modification of the wettability for PHB and PHBV scaffolds from hydrophobic (nonmineralized fibers) to superhydrophilic (mineralized fibers) led to a pronounced apatite-forming behavior of scaffolds in a simulated body fluid. In turn, this results in the formation of a dense monolayer of well-distributed and proliferated osteoblast cells along the fibers. CaCO3-mineralized PHBV surfaces had a higher osteoblast cell adhesion and proliferation assigned to a higher amount of CaCO3 on the surface compared to that on PHB scaffolds, as incurred from micro-computed tomography (μCT). Importantly, a cell viability study confirmed biocompatibility of all the scaffolds. Thus, hybrid biocomposites based on the piezoelectric PHB polymers represent an effective scaffold platform functionalized by an inorganic phase and stimulating the growth of the bone tissue.

Highly porous PHB-based bioactive scaffolds for bone tissue engineering by in situ synthesis of hydroxyapatite

In this study bioactive and bioresorbable porous scaffolds for bone tissue regeneration, based on poly(3-hydroxybutyrate) (PHB), are presented. The porous structure is obtained by thermally induced phase separation (TIPS) technique, whereas the osteoinductivity and osteoconductivity are enhanced through the incorporation of hydroxyapatite (HA). The HA particles are generated in PHB using an innovative filler in situ synthesis, and the properties of the composite scaffolds are then compared to scaffolds obtained by conventional mechanical dispersion of ex situ synthesized HA particles. The in situ synthesis leads to composite materials with improved porosity, even at high filler content, without any degradation of the polymeric matrix as confirmed by GPC and DSC measurements. On the contrary, the samples prepared by ex situ method show a suppressed porosity by increasing the inorganic filler content, therefore limiting the amount of HA that can be loaded in PHB and the resulting bioactivity. The possibility to use PHB/HA porous composites as scaffolds for bone tissue regeneration, is assessed by preliminary cell viability in vitro studies. In particular, it is observed that the composites are fully cytocompatible and able to sustain MC3T3-E1 mouse pre-osteoblast cells adhesion and proliferation. Investigations on cell morphology reveal, for all PHB/HA scaffolds, the presence of differentiated cells with a predominance of osteocyte-like morphology, which are not observed for neat PHB scaffolds. Moreover, the MC3T3-E1 cells differentiation towards osteoblastic phenotype is further supported by the evaluation of the early osteogenic markers. In particular, samples loaded with HA in situ synthesized showed the highest ALP production and typical morphology of the terminal differentiation stages of osteoblasts.

Multifunctional Scaffolds with Improved Antimicrobial Properties and Osteogenicity Based on Piezoelectric Electrospun Fibers Decorated with Bioactive Composite Microcapsules.

The incorporation of bioactive compounds onto polymer fibrous scaffolds with further control of drug release kinetics is essential to improve the functionality of scaffolds for personalized drug therapy and regenerative medicine. In this study, polymer and hybrid microcapsules were prepared and used as drug carriers, which are further deposited onto polymer microfiber scaffolds [polycaprolactone (PCL), poly(3-hydroxybutyrate) (PHB), and PHB doping with the conductive polyaniline (PANi) of 2 wt % (PHB-PANi)]. The number of immobilized microcapsules decreased with increase in their ζ-potential due to electrostatic repulsion with the negatively charged fiber surface, depending on the polymer used for the scaffold's fabrication. Additionally, the immobilization of the capsules in dynamic mechanical conditions at a frequency of 10 Hz resulted in an increase in the number of the capsules on the fibers with increase in the scaffold piezoelectric response in the order PCL < PHB < PHB-PANi, depending on the chemical composition of the capsules. The immobilization of microcapsules loaded with different bioactive molecules onto the scaffold surface enabled multimodal triggering by physical (ultrasound, laser radiation) and biological (enzymatic treatment) stimuli, providing controllable release of the cargo from scaffolds. Importantly, the microcapsules immobilized onto the surface of the scaffolds did not influence the cell growth, viability, and cell proliferation on the scaffolds. Moreover, the attachment of human mesenchymal stem cells (hMSCs) on the scaffolds revealed that the PHB and PHB-PANi scaffolds promoted adhesion of hMSCs compared to that of the PCL scaffolds. Two bioactive compounds, antibiotic ceftriaxone sodium (CS) and osteogenic factor dexamethasone (DEXA), were chosen to load the microcapsules and demonstrate the antimicrobial properties and osteogenesis of the scaffolds. The modified scaffolds had prolonged release of CS or DEXA, which provided an improved antimicrobial effect, as well as enhanced osteogenic differentiation and mineralization of the scaffolds modified with capsules compared to that of individual scaffolds soaked in CS solution or incubated in an osteogenic medium. Thus, the immobilization of microcapsules provides a simple, convenient way to incorporate bioactive compounds onto polymer scaffolds, which makes these multimodal materials suitable for personalized drug therapy and bone tissue engineering.

Assessment of poly(3-hydroxybutyrate) synthesis from a novel obligate alkaliphilic Bacillus marmarensis and generation of its composite scaffold via electrospinning

In this study, poly(3-hydroxybutyrate) (PHB) production from a newly isolated obligate alkaliphilic Bacillus marmarensis DSM 21297 was investigated to evaluate the ability of obligate alkaliphilic strain to produce a biopolymer. Additionally, electrospun nanofibers from B. marmarensis PHB (Bm-PHB) were generated using Bm-PHB/polycaprolactone (PCL) blend to evaluate the applicability of Bm-PHB. According to the experimental results, the metabolic activity of B. marmarensis decreased the pH of the medium by generating H+ ions to initiate Bm-PHB production, which was achieved at pH below 9.0. Regarding medium components, the addition of MgSO4.7H2O and KH2PO4 to the medium containing 1% glucose enhanced the amount of Bm-PHB synthesis, and an approximately 60% increase in PHB concentration was obtained in the presence of mineral salts.Based on FTIR analysis, the chemical structures of Bm-PHB and commercial PHB were found to be highly similar. Additionally, the Tg and Tm values of Bm-PHB were determined to be 17.77 °C and 165.17 °C, respectively. Moreover, Bm-PHB/PCL composite scaffold was generated by electrospinning method that produced nanofibers between 150 and 400 nm in diameter, with an average of 250 nm. To our knowledge, this is the first report to produce PHB from an obligate alkaliphilic Bacillus strain and PHB scaffold.

Three-dimensional printing and in vitro evaluation of poly(3-hydroxybutyrate) scaffolds functionalized with osteogenic growth peptide for tissue engineering

Poly(3-hydroxybutyrate) (PHB) is a biodegradable and thermoprocessable biopolymer, making it a promising candidate for applications in tissue engineering. In the present study a structural characterization and in vitro evaluation were performed on PHB scaffolds produced by additive manufacturing via selective laser sintering (SLS), followed by post-printing functionalization with osteogenic growth peptide (OGP) and its C-terminal sequence OGP(10–14). The PHB scaffolds were characterized, including their morphology, porosity, thermal and mechanical properties, moreover OGP release. The results showed that SLS technology allowed the sintering of the PHB scaffolds with a hierarchical structure with interconnected pores and intrinsic porosity (porosity of 55.8 ± 0.7% and pore size in the 500–700 μm range), and good mechanical properties. Furthermore, the SLS technology did not change thermal properties of PHB polymer. The OGP release profile showed that PHB scaffold promoted a controlled release above 72 h. In vitro assays using rat bone marrow stem cells showed good cell viability/proliferation in all the PHB scaffolds. Additionally, SEM images suggested advanced morphological differentiation in the groups containing osteogenic growth peptide. The overall results demonstrated that PHB biopolymer is potential candidate for 3D printing via SLS technology, moreover the OGP-containing PHB scaffolds showed ability to sustain cell growth to support tissue formation thereby might be considered for tissue-engineering applications.

Electrospun poly(hydroxybutyrate) scaffolds promote engraftment of human skin equivalents via macrophage M2 polarization and angiogenesis.

Human dermo-epidermal skin equivalents (DE) comprising in vitro expanded autologous keratinocytes and fibroblasts are a good option for massive burn treatment. However, the lengthy expansion time required to obtain sufficient surface to cover an extensive burn together with the challenging surgical procedure limits their clinical use. The integration of DE and biodegradable scaffolds has been proposed in an effort to enhance their mechanical properties. Here, it is shown that poly(hydroxybutyrate) electrospun scaffolds (PHB) present good biocompatibility both in vitro and in vivo and are superior to poly-ε-caprolactone electrospun scaffolds as a substrate for skin reconstruction. Implantation of PHB scaffolds in healthy rats polarized macrophages to an M2-type that promoted constructive in vivo remodelling. Moreover, implantation of DE-PHB composites in a NOD/SCID mouse xenograft model resulted in engraftment accompanied by an increase in angiogenesis that favoured the survival of the human graft. Thus, PHB scaffolds are an attractive substrate for further exploration in skin reconstruction procedures, probably due in part to their greater angiogenic and M2 macrophage polarization properties. Copyright © 2017 John Wiley & Sons, Ltd.