Electrospun nanofibrous scaffolds as a platform to reduce melanoma tumour growth, recurrence, and promote post-resection wound repair.

Wound healing following skin tumour surgery still remains a major challenge. To address this issue, polysaccharide-loaded nanofibrous mats have been engineered as skin patches on the wound site to improve wound healing while simultaneously eliminating residual cancer cells which may cause cancer relapse. The marine derived polysaccharides kappa-carrageenan (KCG) and fucoidan (FUC) were blended with polydioxanone (PDX) nanofibers due to their inherent anti-cancer activity conferred by the sulphate groups as well as their immunomodulatory properties which can reduce inflammation resulting in accelerated wound healing. KCG and FUC were released sustainably from the blend nanofibers via the Korsmeyer-Peppas kinetics. MTT assays, live/dead staining and SEM images demonstrated the toxicity of KCG and FUC towards skin cancer MP 41 cells. In addition, MP 41 cells showed reduced metastatic potential when grown on KCG or FUC containing mats. Both KCG and FUC were non- cytotoxic to healthy L 929 fibroblast cells. In vivo studies on healthy Wistar rats confirmed the non-toxicity of the nanofibrous patches as well as their improved and scarless wound healing potential. In vivo studies on tumour xenograft model further showed a reduction of 7.15 % in tumour volume in only 4 days following application of the transdermal patch.

Effect of poly-L-lactic acid and polydioxanone biostimulators on type I and III collagen biosynthesis.

OBJECTIVE: Safe, effective, and biocompatible minimally invasive procedures with the potential to stimulate collagen production have been made to recover dermal thickness and skin quality. The main of this animal model experiment was to observe the effect of poly-L-lactic acid (PLLA) and polydioxanone (PDO) biostimulators in collagen I and III after hypodermal injection. METHODOLOGY: Sixteen adult female rats (Wistar) were randomized into four groups and had dorsal treatment with: G1: hypodermic subcision (HS) only; G2: HS and PLLA hypodermic injection (HI), G3: HS and PDO HI; G4: Control, with no treatment. RESULTS: In histochemical, it was observed hypodermal and dermal tissue in more organized thickness in G3 and in G4 when compared to G1 and G2. There was few difference in G1 compared to G4. The tissue of G2 showed irregularities in the arrangement of collagen fibers, less defined structure and lower distribution of type I collagen compared to the other groups. There is a greater tendency for the proportions of type III collagen among tissues treated with both biostimulators (G2 and G3). PLLA and PDO had relatively similar percentages of collagen when compared to G4. The amount of type I collagen was higher in tissues treated with subcision, while type III collagen was higher in tissues treated with both biostimulators. CONCLUSION: G3 showed better performance in collagen production, although small, when compared with G2.

Polydioxanone Enhances Bone Regeneration After Resection and Reconstruction of Rat Femur with rhBMP2.

The aim of this study was to assess the bone regeneration potential of a polydioxanone (PDO) scaffold together with recombinant human bone morphogenetic protein-2 (rhBMP-2) for the reconstruction of large bone defect. In total, 24 male rats (6 months old) were subjected to bilateral femoral stabilization using titanium plates to create a 2 mm gap, and reconstruction using rhBMP-2 (Infuse®; 3.25 µg). The bone defects were covered with PDO (PDO group), or with titanium mesh (Ti group). Animals were euthanized on days 14 and 60. Simultaneously, 16 rats received PDO and Ti in their dorsum for the purpose of biocompatibility analysis at 3, 5, 7, and 10 days postoperatively. X-ray densitometry showed a higher density in the PDO group on day 14. On day 60, coverage of the bone defect with PDO showed a larger quantity of newly formed bone than that found for the Ti group, a lower inflammatory infiltrate value, and a more significant number of blood vessels on day 14. By immunohistochemical assessment, runt-related transcription factor 2 (RUNX2) and osteocalcin (OCN) showed higher labeling on day 14 in the PDO group. On day 60, bone morphogenetic protein-2 (BMP-2) showed higher labeling in the PDO group, whereas Ti showed higher labeling for osteoprotegerin, nuclear factor kappa B ligand-activating receptor, RUNX2, and OCN. Furthermore, biocompatibility analysis showed a higher inflammatory response in the Ti group. The PDO scaffold enhanced bone regeneration when associated with rhBMP-2 in rat femur reconstruction. Impact statement Regeneration of segmental bone defects is a difficult task, and several techniques and materials have been used. Recent advances in the production of synthetic polymers, such as polydioxanone (PDO), produced by three-dimensional printing, have shown distinct characteristics that could improve tissue regeneration even in an important bone defect. The present preclinical study showed that PDO membranes used as scaffolds to carry recombinant human bone morphogenetic protein-2 (rhBMP-2) improved bone tissue regeneration by more than 8-fold when compared with titanium mesh, suggesting that PDO membranes could be a feasible and useful material for use in guided bone regeneration. (In English, viable is only used for living creatures capable of sustaining life.

Mechanical characterization and neutrophil NETs response of a novel hybrid geometry polydioxanone near-field electrospun scaffold.

Near-field electrospinning (NFES) is a direct fiber writing sub-technique derived from traditional electrospinning (TES) by reducing the air gap distance to the magnitude of millimeters. In this paper, we demonstrate a NFES device designed from a commercial 3D printer to semi-stably write polydioxanone (PDO) microfibers. The print head was then programmed to translate in a stacking grid pattern, which resulted in a scaffold with highly aligned grid fibers that were intercalated with low density, random fibers. As the switching process can be considered random, increasing the grid size results in both a lower density of fibers in the center of each grid cell as well as a lower density of 'rebar-like' stacked fibers. These scaffolds resulted in tailorable as well as greater surface pore sizes as given by scanning electron micrographs and 3D permeability as indicated by fluorescent microsphere filtration compared to TES scaffolds of the same fiber diameter. Furthermore, ultimate tensile strength, percent elongation, yield stress, yield elongation, and Young's modulus were all tailorable compared to the static TES scaffold characterization. Lastly, the innate immune response of neutrophil extracellular traps was attenuated on NFES scaffolds compared to TES scaffolds. These results suggest that this novel NFES scaffold architecture of PDO can be highly tailored as a function of programming for a variety of biomedical and tissue engineering applications.

The efficacy of powdered polydioxanone in terms of collagen production compared with poly-L-lactic acid in a murine model.

BACKGROUND: There are many collagen-stimulating fillers, including calcium hydroxyapatite, polycaprolactone (PCL), and poly-L-lactic acid (PLLA), and other materials have been tested. Polydioxanone (PDO) has recently been used as absorbable thread-lifting material due to its collagen-forming effects. PDO in powdered form is expected to be a good material for collagen-producing fillers. OBJECTIVES: To evaluate the collagen-producing effects of powdered PDO injection compared with PLLA injection in a murine model. MATERIALS AND METHODS: Powdered PDO mixed with sodium carboxymethyl cellulose, PLLA, and phosphate-buffered saline was injected on dorsal skin of 8-week-old rat. Tissue samples were obtained 1, 2, and 12 weeks after the procedures for histopathologic review and for real-time PCR to quantify collagen and tissue growth factors. RESULTS: Both PLLA and powdered PDO injections induced granulomatous reactions. Collagen type 1, collagen type 3, TGF-ß1, TGF-ß2, and TGF-ß3 showed increases 2 weeks after injection but decreased 12 weeks after injection for both powdered PDO and PLLA. CONCLUSION: Our results suggested that powdered PDO injection induces collagen formation more effectively than PLLA injection. Therefore, PDO can be a good option for forming collagen.

Galectin-1 promotes an M2 macrophage response to polydioxanone scaffolds.

Regulating soft tissue repair to prevent fibrosis and promote regeneration is central to creating a microenvironment conducive to soft tissue development. Macrophages play an important role in this process. The macrophage response can be modulated using biomaterials, altering cytokine and growth factor secretion to promote regeneration. Electrospun polydioxanone (PDO) fiber scaffolds promoted an M2 phenotype when macrophages were cultured on large diameter, highly porous scaffolds, but an M1 phenotype on smaller diameter fibers. In this study, we investigated whether incorporation of galectin-1, an immunosuppressive protein that enhances muscle regeneration, could promote the M2 response. Galectin-1 was incorporated into large and small fiber PDO scaffolds during electrospinning. Galectin-1 incorporation increased arginase-1 and reduced iNOS and IL-6 production in mouse bone-marrow derived macrophages compared with PDO alone for both scaffold types. Inhibition of ERK mitogen-activated protein kinase did not alter galectin-1 effects on arginase-1 and iNOS expression, but reversed IL-6 suppression, indicating that IL-6 is mediated by a different mechanism. Our results suggest that galectin-1 can be used to modulate macrophage commitment to a pro-regenerative M2 phenotype, which may positively impact tissue regeneration when using small diameter PDO scaffolds. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2562-2571, 2017.

Resorbable electrospun polydioxanone fibres modify the behaviour of cells from both healthy and diseased human tendons.

Chronic tendinopathy in an active and ageing population represents an increasing burden to healthcare systems. Rotator cuff tendinopathy alone accounts for approximately 70 % of all shoulder pain. Tendinopathic tissue has a disorganised extracellular matrix, altered vasculature, and infiltration of fibroblasts and inflammatory cells. This altered biology may contribute to the limited success of surgical repair strategies. Electrospun resorbable scaffolds can potentially enhance endogenous repair mechanisms by influencing the tissue microenvironment. Polydioxanone (PDO) has an established safety profile in patients. We compared the response of healthy and diseased human tendon cells to electrospun PDO fibres using live cell imaging, proliferation, flow cytometry, and gene expression studies. Within 4 h of initial contact with electrospun PDO, healthy tendon cells underwent a marked transformation; elongating along the fibres in a fibre density dependent manner. Diseased tendon cells initially responded at a slower rate, but ultimately underwent a similar morphological change. Electrospun fibres increased the proliferation rate of diseased tendon cells and increased the ratio of type I:IIIcollagenmRNA expression. Flow cytometry revealed decreased expression of CD106, a marker of mesenchymal stem cells, and increased expression of CD10 on healthy versus diseased tendon cells. PDO electrospun scaffolds further promoted CD106negCD10pos expression of healthy tendon cells. Despite their behavioural differences, both healthy and diseased human tendon cells responded to electrospun PDO fibres. This encourages further work establishing their efficacy in augmenting surgical repair of diseased tendons.

Assessment of Scaffolding Properties for Chondrogenic Differentiation of Adipose-Derived Mesenchymal Stem Cells in Nasal Reconstruction.

IMPORTANCE: Nasal reconstruction in patients who are missing a significant amount of structural nasal support remains a difficult challenge. One challenge is the deficiency of cartilage left within the nose as a consequence of rhinectomy or a midline destructive disease. Historically, the standard donor source for large quantities of native cartilage has been costal cartilage. OBJECTIVE: To enable the development of protocols for new mesenchymal stem cell technologies as alternative procedures with reduced donor site morbidity, risk of infection and extrusion. DESIGN, SETTING, AND MATERIALS: We examined 6 popular scaffold materials in current practice in terms of their biodegradability in tissue culture, effect on adipose-derived mesenchymal stem cell growth, and chondrogenic fate commitment. Various biomaterials of matching size, porosity, and fiber alignment were synthesized by electrospinning and overlaid with rabbit adipose-derived mesenchymal cells in media supplemented or not with chondrogenic factors. Experiments were performed in vitro using as end points biomarkers for cell growth and chondrogenic differentiation. Polydioxanone (PDO), poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), PHBV-polycaprolactone, poly(L-lactide-co-caprolactone), poly(lactic-co-glycolic acid), and polystyrene scaffolds of 60% to 70% porosity and random fiber alignment were coated with poly(L)-lysine/laminin to promote cell adhesion and incubated for 28 days with 2.5 to 3.5 × 105 rabbit adipose mesenchymal cells. MAIN OUTCOMES AND MEASURES: Cell growth was measured by fluorometric DNA quantitation and chondrogenic differentiation of stem cells by spectrophotometric sulfated glycosaminoglycan (sGAG) assay. Microscopic visualization of cell growth and matrix deposition on formalin-fixed, paraffin-embedded tissue sections was performed, respectively, with nuclear fast red and Alcian blue. RESULTS: Of 6 scaffold materials tested using rabbit apidose mesenchymal cells, uncoated scaffolds promoted limited cell adhesion but coating with poly(L)-lysine/laminin enabled efficient cell saturation of scaffold surfaces, albeit with limited involvement of scaffold interiors. Similar growth rates were observed under these conditions, based on DNA content analysis. However, PDO and PHBV/PCL scaffolds supported chondrogenic fate commitment better than other materials, based on soluble sGAG analysis and microscopic observation of chondrogenic matrix deposition. The mean (SD) sGAG scaffold values expressed as fold increase over control were PDO, 2.26 (0.88), PHBV/PCL, 2.09 (0.83), PLCL, 1.36 (0.39), PLGA, 1.34 (0.77), PHBV, 1.07 (0.31), and PS, 0.38 (0.14). CONCLUSIONS AND RELEVANCE: These results establish materials, reagents, and protocols for tissue engineering for nasal reconstruction using single-layer, chondrogenically differentiated, adipose-derived mesenchymal stem cells. Stackable, scaffold-supported, multisheet bioengineered tissue may be generated using these protocols. LEVEL OF EVIDENCE: NA.

In vivo monitoring of structural and mechanical changes of tissue scaffolds by multi-modality imaging.

Degradable tissue scaffolds are implanted to serve a mechanical role while healing processes occur and putatively assume the physiological load as the scaffold degrades. Mechanical failure during this period can be unpredictable as monitoring of structural degradation and mechanical strength changes at the implant site is not readily achieved in vivo, and non-invasively. To address this need, a multi-modality approach using ultrasound shear wave imaging (USWI) and photoacoustic imaging (PAI) for both mechanical and structural assessment in vivo was demonstrated with degradable poly(ester urethane)urea (PEUU) and polydioxanone (PDO) scaffolds. The fibrous scaffolds were fabricated with wet electrospinning, dyed with indocyanine green (ICG) for optical contrast in PAI, and implanted in the abdominal wall of 36 rats. The scaffolds were monitored monthly using USWI and PAI and were extracted at 0, 4, 8 and 12 wk for mechanical and histological assessment. The change in shear modulus of the constructs in vivo obtained by USWI correlated with the change in average Young's modulus of the constructs ex vivo obtained by compression measurements. The PEUU and PDO scaffolds exhibited distinctly different degradation rates and average PAI signal intensity. The distribution of PAI signal intensity also corresponded well to the remaining scaffolds as seen in explant histology. This evidence using a small animal abdominal wall repair model demonstrates that multi-modality imaging of USWI and PAI may allow tissue engineers to noninvasively evaluate concurrent mechanical stiffness and structural changes of tissue constructs in vivo for a variety of applications.

Ex vivo evaluation of 7 polydioxanone for closure of equine ventral midline celiotomies.

The objective of this study was to compare the bursting strength (BS) and mode of failure (MF) of ventral midline (VM) celiotomies closed with USP 7 polydioxanone (7PD) in 1 or 2 simple continuous sections. A bursting strength model, consisting of inserting and inflating a 200-L polyurethane bladder through a 25-cm VM celiotomy, was used on 15 fresh equine cadavers. Celiotomies were closed using 7PD in 2 separate sections (4 knots), 2 continuous sections (3 knots), or a single section (2 knots) using a simple continuous pattern. The horses' signalment, body weight, number of total knots, MF, and BS were recorded and analyzed statistically for interactions. No difference was found between the BS of VM celiotomies closure types (P = 0.4). All celiotomy/ suture constructs failed at the abdominal wall. The celiotomy closure types evaluated in this study provided a secure method of closure in VM celiotomies in vivo.

L'objectif de la présente étude était de comparer la force d'éclatement (BS) et le mode d'échec (MF) de laparotomies par la ligne ventrale médiale (VM) refermées avec du 7 polydioxanone USP (7PD) en une ou 2 sections continues. Un modèle de force d'éclatement, consistant en l'insertion et le gonflement une vessie de 200 L en polyuréthane via une laparotomie de 25 cm fut utilisé sur 15 cadavres frais de cheval. Les laparotomies étaient refermées en utilisant le 7PD en deux sections séparées (4 nœuds), 2 sections continues (3 nœuds), ou une section simple (2 nœuds) au moyen d'un patron simple continu. L'historique des chevaux, leur poids corporel, le nombre total de nœuds, MF, et BS ont été enregistrés et analysés statistiquement pour les interactions. Aucune différence ne fut trouvée entre les BS et les types de fermetures de VM des laparotomies (P = 0,4). Toutes les laparotomies/modes de suture ont lâché au niveau de la paroi abdominale. Les types de fermeture des laparotomies évalués dans ce projet ont fourni une méthode sécuritaire de fermeture par la VM de laparotomies in vivo.(Traduit par Docteur Serge Messier).

Polymeric nanomicelles for sustained delivery of anti-cancer drugs.

In the first section of this paper, the existing and emerging nanotechnology-based cancer therapies--nanoparticles, drug conjugates, nanomicelles--are reviewed. In a second part, we present our original and unpublished findings on the sustained release of anti-cancer drugs such as paclitaxel, doxorubicin and camptothecin using block copolymer micelles [PEG-b-poly(dioxanone-co-methyl dioxanone)]. Copolymers with variable lengths of hydrophobic and hydrophilic blocks have been synthesized and successfully loaded with paclitaxel, doxorubicin and camptothecin anti-cancer drugs, with micelles size in the range 130-300 nm. Drug encapsulation efficiencies varied between 15% and 70% depending on drug and copolymer composition. The drug binding constants, which give a good insight into drug encapsulation and release, were evaluated from UV spectroscopy as we reported previously for anti-TB drugs. Through variation of the methyl dioxanone content of the copolymer, our systems can be tailored for sustained release of the different drugs.

Mechanism of inhibition on L929 rat fibroblasts proliferation induced by potential adhesion barrier material poly(p-dioxanone-co-L-phenylalanine) electrospun membranes.

Fibroblast plays an important role in the occurrence of postoperative tissue adhesion; materials that have particular "cell-material" interactions to inhibit proliferation of fibroblast will be excellent potential adhesion barriers. In the current study, we synthesized copolymers of p-dioxanone and L-phenylalanine (PDPA) and evaluated the mechanism of its particular inhibition effect on L929 fibroblast proliferation when used as a culture surface. PDPA electrospun membranes could induce apoptosis of L929 fibroblasts. We hypothesized there were two reasons for the apoptosis induction: one was the ability to facilitate cell adhesion of materials, and the other was production of the degradation product, L-phenylalanine. Ninhydrin colorimetric results revealed that L-phenylalanine was continuously released during the culture process and could induce apoptosis in L929 cells. Relatively poor cell adhesion and constant release of L-phenylalanine made PDPA-1 to be the most efficient polymer for the induction of apoptosis. Analysis of apoptosis-related genes revealed that PDPA-induced apoptosis might be performed in a mitochondrial-dependent pathway. But poly(p-dioxanone)-induced apoptosis might occur in a c-Myc independent pathway that was different from PDPA.

Bone morphogenetic proteins-immobilized polydioxanone porous particles as an artificial bone graft.

Bone morphogenetic proteins (BMPs)-immobilized polydioxanone (PDO)/Pluronic F127 porous particles were prepared as a bone graft using a melt-molding particulate-leaching method, and the sequential binding of heparin and BMPs (BMP-2 and BMP-7, single or dual) onto the porous particles. The prepared PDO/Pluronic F127 porous particles gradually degraded with time, with ∼30% of the initial particle weight remaining after 16 weeks. The degradation rate of the PDO/Pluronic F127 porous particles may parallel the bone-healing rate. The BMPs were easily immobilized onto the pore surfaces of PDO/Pluronic F127 particles via heparin binding and were released in a sustained manner for up to 21 days, regardless of BMP type. The BMPs (single BMP-2 or dual BMP-2/BMP-7)-immobilized porous particles were effective for in vitro osteogenesis of bone marrow stem cells (BMSCs), as analyzed by alkaline phosphatase activity, calcium content, time polymerase chain reaction using specific markers for osteogenesis (Type I collagen, osteocalcin, osteopotin, and RunX2), and immunohistochemical staining. The BMPs (single BMP-2 or dual BMP-2/BMP-7)-immobilized porous particles were also effective in promoting new bone formation, as analyzed by the preliminary animal study using a full-thickness skull defect model of Sprague-Dawley rats (microcomputed tomography). The synergistic effect of dual BMPs on the osteogenesis of BMSCs and bone regeneration was not significant in our system. The BMP-2 or dual BMPs (BMP-2/BMP-7)-immobilized PDO/Pluronic F127 porous particles may be a promising candidate as a bone graft for the delayed and insufficient bone healing in clinical fields.

Human umbilical cord blood-derived CD34-positive endothelial progenitor cells stimulate osteoblastic differentiation of cultured human periosteal-derived osteoblasts.

The aim of this study was to examine the effects of human umbilical cord blood-derived CD34-positive endothelial progenitor cells (CD34+ EPCs) on osteoblastic differentiation of cultured human periosteal-derived osteoblasts (POs). CD34+ cells from human umbilical cord blood were sorted to purify more EPCs in characterization. These sorted cells showed CD31, VE-cadherin, and KDR expression as well as CD34 expression and formed typical tubes in Matrigel. These sorted cells were referred to as human cord blood-derived CD34+ EPCs. In in vivo bone formation using a miniature pig model, the newly formed bone was clearly examined in defects filled with polydioxanone/pluronic F127 (PDO/Pluronic F127) scaffolds containing either human umbilical cord blood-derived CD34+ EPCs and POs or human umbilical vein endothelial cells (HUVEC) and POs; however, the new bone had the greatest density in the defect treated with CD34+ EPCs and POs. Osteoblastic phenotypes of cultured human POs using ALP activity and von Kossa staining were also more clearly found in CD34+ EPC-conditioned medium than CD34-negative (CD34-) cell-conditioned medium, whereas HUVEC-conditioned medium had an intermediate effect. PCR array for common cytokines and growth factors showed that the secretion of interleukin (IL)-1ß was significantly higher in CD34+ EPCs than in HUVEC, followed by level in CD34- cells. In addition, IL-1ß also potently and dose dependently increased ALP activity and mineralization of POs in culture. These results suggest that human umbilical cord blood-derived CD34+ EPCs stimulates osteoblastic differentiation of cultured human POs. The functional role of human umbilical cord blood-derived CD34+ EPCs in increasing the osteogenic phenotypes of cultured human POs may depend on IL-1ß secreted from human umbilical cord blood-derived CD34+ EPCs.

Implantation of a novel biologic and hybridized tissue engineered bioimplant in large tendon defect: an in vivo investigation.

Surgical reconstruction of large Achilles tendon defects is technically demanding. There is no standard method, and tissue engineering may be a valuable option. We investigated the effects of 3D collagen and collagen-polydioxanone sheath (PDS) implants on a large tendon defect model in rabbits. Ninety rabbits were divided into three groups: control, collagen, and collagen-PDS. In all groups, 2 cm of the left Achilles tendon were excised and discarded. A modified Kessler suture was applied to all injured tendons to retain the gap length. The control group received no graft, the treated groups were repaired using the collagen only or the collagen-PDS prostheses. The bioelectrical characteristics of the injured areas were measured at weekly intervals. The animals were euthanized at 60 days after the procedure. Gross, histopathological and ultrastructural morphology and biophysical characteristics of the injured and intact tendons were investigated. Another 90 pilot animals were also used to investigate the inflammatory response and mechanism of graft incorporation during tendon healing. The control tendons showed severe hyperemia and peritendinous adhesion, and the gastrocnemius muscle of the control animals showed severe atrophy and fibrosis, with a loose areolar connective tissue filling the injured area. The tendons receiving either collagen or collagen-PDS implants showed lower amounts of peritendinous adhesion, hyperemia and muscle atrophy, and a dense tendon filled the defect area. Compared to the control tendons, application of collagen and collagen-PDS implants significantly improved water uptake, water delivery, direct transitional electrical current and tissue resistance to direct transitional electrical current. Compared to the control tendons, both prostheses showed significantly increased diameter, density and alignment of the collagen fibrils and maturity of the tenoblasts at ultrastructure level. Both prostheses influenced favorably tendon healing compared to the control tendons, with no significant differences between collagen and collagen-PDS groups. Implantation of the 3D collagen and collagen-PDS implants accelerated the production of a new tendon in the defect area, and may become a valuable option in clinical practice.

Biodegradable weft-knitted intestinal stents: fabrication and physical changes investigation in vitro degradation.

Biodegradable stents can alleviate intestinal obstruction and stenosis in patients. The objective of this study was to develop a biodegradable polydioxanone (PDO) stent using weft-knitting technology and then investigate its biodegradation behaviors in vitro. PDO monofilament with linear density of 100 ± 10 tex was knitted into a tubular stent using a tubular weft-knitting machine. The physical and mechanical properties were evaluated according to the British standard BS EN 13895:2003 and ISO 7198:1998. The biodegradation behaviors of PDO weft-knitted stent in a phosphate buffer solution (pH = 6.8 ± 0.2, 37 ± 0.5 °C) were then investigated. The results showed that the stent maintained more than 60% of its original radial force above 12 weeks. During the 16 weeks of degradation, weight, crystallization, and pH change indicated the degradation medium was diffused into the chain segments of low molecular weight due to the rupture of ester bonds in the monofilament. Fourier transform infrared spectroscopy results demonstrated that the chemical structure of PDO polymer is stable during the in vitro degradation. In conclusion, this biodegradable stent can find valuable applications in treatment of intestinal obstruction and stenosis clinically.

Macrophage functional polarization (M1/M2) in response to varying fiber and pore dimensions of electrospun scaffolds.

In this study, we investigated the effect of fiber and pore size of an electrospun scaffold on the polarization of mouse bone marrow-derived macrophages (BMMΦs) towards regenerative (M2) or inflammatory (M1) phenotypes. BMMΦs were seeded on Polydioxanone (PDO) scaffolds electrospun from varying polymer concentrations (60, 100, and 140 mg/ml). Higher polymer concentrations yielded larger diameter fibers with larger pore sizes and porosity. BMMΦ cultured on these scaffolds showed a correlation between increasing fiber/pore size and increased expression of the M2 marker Arginase 1 (Arg1), along with decreased expression of the M1 marker inducible nitric oxide synthase (iNOS). Secretion of the angiogenic cytokines VEGF, TGF-ß1 and bFGF was higher among cultures employing larger fiber/pore size scaffolds (140 mg/ml). Using a 3D in vitro angiogenesis bead assay, we have demonstrated that the M2-like profile of BMMΦ induced by the 140 mg/ml is functional. Furthermore, our results show that the pore size of a scaffold is a more critical regulator of the BMMΦ polarization compared to the fiber diameter. The study also shows a potential role for MyD88 in regulating M1 BMMΦ signaling on the large vs. small fiber/pore size PDO scaffold. These data are instructive for the rationale design of implantable prosthetics designed to promote in situ regeneration.

Generation of osteogenic construct using periosteal-derived osteoblasts and polydioxanone/pluronic F127 scaffold with periosteal-derived CD146 positive endothelial-like cells.

The purpose of this study was to generate tissue-engineered bone using human periosteal-derived osteoblasts (PO) and polydioxanone/pluronic F127 (PDO/pluronic F127) scaffold with preseeded human periosteal-derived CD146 positive endothelial-like cells (PE). PE were purified from the periosteal cell population by cell sorting. One of the important factors to consider in generating tissue-engineered bone using osteoprecursor and endothelial cells and a specific scaffold is whether the function of osteoprecursor and endothelial cells can be maintained in originally different culture medium conditions. After human PE were preseeded into PDO/pluronic F127 scaffold and cultured in endothelial cell basal medium-2 for 7 days, human PO were seeded into the PDO/pluronic F127 scaffold with PE, and then, this cell-scaffold construct was cultured in endothelial cell basal medium-2 with osteogenic induction factors, including ascorbic acid, dexamethasone, and ß-glycerophosphate, for a further 7 days. Then, this 2-week cultured construct was grafted into the mandibular defect of miniature pig. Twelve weeks after implantation, the animal was sacrificed. Clinical examination revealed that newly formed bone was seen more clearly in the defect with human PO and PDO/pluronic F127 scaffold with preseeded human PE. The experimental results suggest that tissue-engineered bone formation using human PO and PDO/pluronic F127 scaffold with preseeded human PE can be used to restore skeletal integrity to various bony defects when used in clinics.

Modulation of mast cell adhesion, proliferation, and cytokine secretion on electrospun bioresorbable vascular grafts.

Mast cells synthesize several potent angiogenic factors and can also stimulate fibroblasts, endothelial cells, and macrophages. An understanding of how they participate in wound healing and angiogenesis is important to further our knowledge about in situ vascular prosthetic regeneration. The adhesion, proliferation, and cytokine secretion of bone marrow-derived murine mast cells (BMMC) on electrospun polydioxanone, polycaprolactone, and silk scaffolds, as well as tissue culture plastic, has been investigated in the presence or absence of IL-3, stem cell factor, IgE and IgE with a crosslinking antigen, dinitrophenol-conjugated albumin (DNP). It was previously believed that only activated BMMCs exhibit adhesion and cytokine secretion. However, this study shows nonactivated BMMC adhesion to electrospun scaffolds. Silk scaffold was not found to be conducive for mast cell adhesion and cytokine secretion. Activation by IgE and DNP significantly enhanced mast cell adhesion, proliferation, migration, and secretion of tumor necrosis factor alpha, macrophage inflammatory protein-1α, and IL-13. This indicates that mast cells might play a role in the process of biomaterial integration into the host tissue, regeneration, and possibly angiogenesis.