Dual electrospinning with sacrificial fibers for engineered porosity and enhancement of tissue ingrowth.

Porosity, pore size and pore interconnectivity are critical factors for cellular infiltration into electrospun scaffolds. This study utilized dual electrospinning with sacrificial fiber extraction to produce scaffolds with engineered porosity and mechanical properties. Subsequently, scaffolds were covalently grafted with heparin, a known anti-coagulant with growth-factor binding properties. We hypothesized that the tissue ingrowth would correlate positively with the porosity of the scaffolds. Pellethane® (PU) was spun simultaneously with poly(ethylene oxide) (PEO, subsequently extracted). Low, medium and high porosity scaffolds and heparinized versions of each were characterized and implanted in vivo for evaluation of cellular infiltration and inflammation subcutaneously in male Wistar rats (7,14 and 28 days, n = 6). Average pore-size for low (76 ± 0.2%), medium (83 ± 0.5%) and high (90 ± 1.0%) porosity scaffolds was 4.0 ± 2.3 µm, 9.9 ± 4.2 µm and 11.1 ± 5.5 µm (p < 0.0001). Heparinization resulted in increased fiber diameter (3.6 ± 1.1 µm vs. 1.8 ± 0.8 µm, p < 0.0001) but influenced neither pore-size (p = 0.67) nor porosity (p = 0.27). Cellular infiltration for low, medium and high porosity scaffolds reached 33 ± 7%, 77 ± 20% and 98 ± 1% of scaffold width, respectively, by day 28 of implantation (p < 0001); heparinization did not affect infiltration (p = 0.89). The ultimate tensile strength (UTS) and Young's modulus (Ey ) of the constructs increased linearly with increasing PU fiber fraction (UTS: r2  = 0.97, p < 0.0001, Ey : r2 = 0.76, p < 0.0001) and heparinization resulted in decreased strength but increased stiffness compared to non-heparinized scaffolds. Increased PEO to PU fraction in the scaffold resulted in predictable losses to mechanical strength and improvements to cellular infiltration, which could make PEO to PU fraction a useful optimization parameter for small diameter vascular grafts. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1559-1572, 2017.

[1]  C. Vaquette,et al.  Increasing electrospun scaffold pore size with tailored collectors for improved cell penetration. , 2011, Acta biomaterialia.

[2]  M. Edirisinghe,et al.  A novel method of selecting solvents for polymer electrospinning , 2010 .

[3]  W. Park,et al.  The effects of solution properties and polyelectrolyte on electrospinning of ultrafine poly(ethylene oxide) fibers , 2004 .

[4]  F. Baaijens,et al.  Tailoring the void space and mechanical properties in electrospun scaffolds towards physiological ranges. , 2014, Journal of materials chemistry. B.

[5]  Devotha Nyambo,et al.  Applications: A Review , 2014 .

[6]  N. L'Heureux,et al.  Human tissue-engineered blood vessels for adult arterial revascularization , 2007, Nature Medicine.

[7]  Yiqi Yang,et al.  Novel 3D electrospun scaffolds with fibers oriented randomly and evenly in three dimensions to closely mimic the unique architectures of extracellular matrices in soft tissues: fabrication and mechanism study. , 2013, Langmuir : the ACS journal of surfaces and colloids.

[8]  Kwangsok Kim,et al.  Structure and process relationship of electrospun bioabsorbable nanofiber membranes , 2002 .

[9]  J. Folkman,et al.  Control of angiogenesis by heparin and other sulfated polysaccharides. , 1992, Advances in experimental medicine and biology.

[10]  Kerm Sin Chian,et al.  Fabrication and in vitro and in vivo cell infiltration study of a bilayered cryogenic electrospun poly(D,L-lactide) scaffold. , 2010, Journal of biomedical materials research. Part A.

[11]  Guy Schlatter,et al.  Thick electrospun honeycomb scaffolds with controlled pore size , 2015 .

[12]  Jason A Burdick,et al.  Sacrificial nanofibrous composites provide instruction without impediment and enable functional tissue formation , 2012, Proceedings of the National Academy of Sciences.

[13]  H. Bergmeister,et al.  Healing characteristics of electrospun polyurethane grafts with various porosities. , 2013, Acta biomaterialia.

[14]  A. Seifalian,et al.  In vivo femoropopliteal arterial wall compliance in subjects with and without lower limb vascular disease. , 1999, Journal of vascular surgery.

[15]  D. Bezuidenhout,et al.  Covalent Surface Heparinization Potentiates Porous Polyurethane Scaffold Vascularization , 2010, Journal of biomaterials applications.

[16]  D. Lim,et al.  Cell infiltration and growth in a low density, uncompressed three-dimensional electrospun nanofibrous scaffold. , 2011, Biomaterials.

[17]  R. Sanderson,et al.  Modification, crosslinking and reactive electrospinning of a thermoplastic medical polyurethane for vascular graft applications. , 2010, Acta biomaterialia.

[18]  Xiaohong Li,et al.  Electrospun fibrous mats with high porosity as potential scaffolds for skin tissue engineering. , 2008, Biomacromolecules.

[19]  Horst A von Recum,et al.  Electrospinning: applications in drug delivery and tissue engineering. , 2008, Biomaterials.

[20]  John Lannutti,et al.  Fabrication of burst pressure competent vascular grafts via electrospinning: effects of microstructure. , 2009, Journal of biomedical materials research. Part A.

[21]  John F. Rabolt,et al.  Micro- and Nanostructured Surface Morphology on Electrospun Polymer Fibers , 2002 .

[22]  Qiang Zhao,et al.  Improvement of cell infiltration in electrospun polycaprolactone scaffolds for the construction of vascular grafts. , 2014, Journal of biomedical nanotechnology.

[23]  Il Keun Kwon,et al.  Electrospun nano- to microfiber fabrics made of biodegradable copolyesters: structural characteristics, mechanical properties and cell adhesion potential. , 2005, Biomaterials.

[24]  A. Seifalian,et al.  Compliance properties of conduits used in vascular reconstruction , 2000, The British journal of surgery.

[25]  J. Burdick,et al.  The Influence of Fibrous Elastomer Structure and Porosity on Matrix Organization , 2010, PloS one.

[26]  P. Neuenschwander,et al.  Tuning electrospinning parameters for production of 3D-fiber-fleeces with increased porosity for soft tissue engineering applications. , 2011, European cells & materials.

[27]  Jian Yu,et al.  Femtosecond laser ablation enhances cell infiltration into three-dimensional electrospun scaffolds. , 2012, Acta biomaterialia.

[28]  F. N. van de Vosse,et al.  Experimental investigation of collagen waviness and orientation in the arterial adventitia using confocal laser scanning microscopy , 2011, Biomechanics and Modeling in Mechanobiology.

[29]  A. Clowes,et al.  Suppression by heparin of smooth muscle cell proliferation in injured arteries , 1977, Nature.

[30]  N. Lamba.  Polyurethanes in Biomedical Applications , 1997 .

[31]  G. Bowlin,et al.  Fabrication of cell penetration enhanced poly (l-lactic acid-co-ɛ-caprolactone)/silk vascular scaffolds utilizing air-impedance electrospinning. , 2014, Colloids and surfaces. B, Biointerfaces.

[32]  Jian Yang,et al.  Novel biphasic elastomeric scaffold for small-diameter blood vessel tissue engineering. , 2005, Tissue engineering.

[33]  David G Simpson,et al.  Utilizing acid pretreatment and electrospinning to improve biocompatibility of poly(glycolic acid) for tissue engineering. , 2004, Journal of biomedical materials research. Part B, Applied biomaterials.

[34]  Dietmar W Hutmacher,et al.  Combining electrospun scaffolds with electrosprayed hydrogels leads to three-dimensional cellularization of hybrid constructs. , 2008, Biomacromolecules.

[35]  A. Mikos,et al.  Electrospinning of polymeric nanofibers for tissue engineering applications: a review. , 2006, Tissue engineering.

[36]  Zhigang Xie,et al.  Electrospinning of polymeric nanofibers for drug delivery applications. , 2014, Journal of controlled release : official journal of the Controlled Release Society.

[37]  James J. Yoo,et al.  Bilayered scaffold for engineering cellularized blood vessels. , 2010, Biomaterials.

[38]  R. Rossi,et al.  Simultaneous electrospinning and electrospraying: a straightforward approach for fabricating hierarchically structured composite membranes. , 2013, ACS applied materials & interfaces.

[39]  A. Khademhosseini,et al.  Controlling the porosity of fibrous scaffolds by modulating the fiber diameter and packing density. , 2011, Journal of biomedical materials research. Part A.

[40]  J. Beckstead,et al.  A simple technique for preservation of fixation-sensitive antigens in paraffin-embedded tissues. , 1994, The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society.

[41]  Ross A. Marklein,et al.  The potential to improve cell infiltration in composite fiber-aligned electrospun scaffolds by the selective removal of sacrificial fibers. , 2008, Biomaterials.

[42]  Min Soo Bae,et al.  Highly porous electrospun nanofibers enhanced by ultrasonication for improved cellular infiltration. , 2011, Tissue engineering. Part A.

[43]  Eric Jeffries,et al.  Highly elastic and suturable electrospun poly(glycerol sebacate) fibrous scaffolds. , 2015, Acta biomaterialia.

[44]  Johannes E. Schindelin,et al.  Fiji: an open-source platform for biological-image analysis , 2012, Nature Methods.

[45]  N Pallua,et al.  Modulation of angiogenic potential of collagen matrices by covalent incorporation of heparin and loading with vascular endothelial growth factor. , 2004, Tissue engineering.

[46]  James M. Anderson,et al.  The topographical effect of electrospun nanofibrous scaffolds on the in vivo and in vitro foreign body reaction. , 2009, Journal of biomedical materials research. Part A.

[47]  E. Young.  The anti-inflammatory effects of heparin and related compounds. , 2008, Thrombosis research.

[48]  Michael Unser,et al.  Effect of Aging on Elastin Functionality in Human Cerebral Arteries , 2008, Stroke.

[49]  V. Vogel,et al.  Influence of the fiber diameter and surface roughness of electrospun vascular grafts on blood activation. , 2012, Acta biomaterialia.