Eda D. Yildirim

Accelerated differentiation of osteoblast cells on polycaprolactone scaffolds driven by a combined effect of protein coating and plasma modification

A combined effect of protein coating and plasma modification on the quality of the osteoblast-scaffold interaction was investigated. Three-dimensional polycaprolactone (PCL) scaffolds were manufactured by the precision extrusion deposition (PED) system. The structural, physical, chemical and biological cues were introduced to the surface through providing 3D structure, coating with adhesive protein fibronectin and modifying the surface with oxygen-based plasma. The changes in the surface properties of PCL after those modifications were examined by contact angle goniometry, surface energy calculation, surface chemistry analysis (XPS) and surface topography measurements (AFM). The effects of modification techniques on osteoblast short-term and long-term functions were examined by cell adhesion, proliferation assays and differentiation markers, namely alkaline phosphatase activity (ALP) and osteocalcin secretion. The results suggested that the physical and chemical cues introduced by plasma modification might be sufficient for improved cell adhesion, but for accelerated osteoblast differentiation the synergetic effects of structural, physical, chemical and biological cues should be introduced to the PCL surface.

Fabrication, Characterization, and Biocompatibility of Single-Walled Carbon Nanotube-Reinforced Alginate Composite Scaffolds Manufactured Using Freeform Fabrication Technique

Composite polymeric scaffolds from alginate and single-walled carbon nanotube (SWCNT) were produced using a freeform fabrication technique. The scaffolds were characterized for their structural, mechanical, and biological properties by scanning electron microscopy, Raman spectroscopy, tensile testing, and cell-scaffold interaction study. Three-dimensional hybrid alginate/SWCNT tissue scaffolds were fabricated in a multinozzle biopolymer deposition system, which makes possible to disperse and align SWCNTs in the alginate matrix. The structure of the resultant scaffolds was significantly altered due to SWCNT reinforcement, which was confirmed by Raman spectroscopy. Microtensile testing presented a reinforcement effect of SWCNT to the mechanical strength of the alginate struts. Ogden constitutive modeling was utilized to predict the stress-strain relationship of the alginate scaffold, which compared well with the experimental data. Cellular study by rat heart endothelial cell showed that the SWCNT incorporated in the alginate structure improved cell adhesion and proliferation. Our study suggests that hybrid alginate/SWCNT scaffolds are a promising biomaterial for tissue engineering applications.

Development of a cold atmospheric pressure microplasma jet for freeform cell printing

An atmospheric pressure non-thermal microplasma jet (O 50 μm) was developed for localized functionalization of various substrates, including polymers, to allow maskless freeform cell printing. The applied microplasma jet power ranged from 0.1 to 0.2 W without causing any damage to the polyethylene substrate. The surface characterization results demonstrate that the microplasma treatment locally changes the surface roughness and the concentration of oxygen-containing functional groups on the polyethylene surface. The biological characterization confirms that the osteoblast cells attach and survive on the plasma activated line while untreated surfaces show almost no attachment and viability.

Fabrication and plasma treatment of 3D polycaprolactane tissue scaffolds for enhanced cellular function

This paper reports a solid free-form fabrication (SFF) technology-based precision extrusion deposition (PED) process to manufacture three-dimensional (3D) polycaprolactane (PCL) scaffolds and their surface treatment with a plasma source for enhanced osteoblast cell adhesion and proliferation. The PED process allows us to manufacture tissue engineering scaffolds based on designed geometry with complete interconnectivity and controllable porosity. The as-fabricated PCL scaffolds have a pattern with a 0/90° strut configuration of 300 µm pore size and 250 µm strut width. In order to improve cellular activity on 3D PCL scaffolds, they were surface-treated with an oxygen-based plasma source. The surface hydrophilicity and total surface energy of PCL was increased with plasma treatment. Comparisons of different plasma treatment times, including 30 seconds, and 1, 2, 3, 5 and 7 minutes, were performed to identify the plasma treatment duration suggesting higher cellular adhesion and proliferation. The maximum value of total surface energy and its components (polar and dispersive) was observed in 3-min treated PCL scaffolds. In addition, the positive effect of plasma treatment was observed in stregth of cell adhesion, which was increased 55% on 3-min plasma-treated scaffolds compared to untreated and other plasma treatment duriations. Cell culture study over a 7-day period also showed that the cell number on 3-min treated scaffolds is 3-fold the number of cells on untreated scaffolds.

Precision Extruding Deposition for Freeform Fabrication of PCL and PCL-HA Tissue Scaffolds

Computer-aided tissue engineering approach was used to develop a novel Precision Extrusion Deposition (PED) process to directly fabricate Polycaprolactone (PCL) and composite PCL/Hydroxyapatite (PCL-HA) tissue scaffolds. The process optimization was carried out to fabricate both PCL and PCL-HA (25% concentration by weight of HA) with a controlled pore size and internal pore structure of the 0°/90° pattern. Two groups of scaffolds having 60 and 70% porosity and with pore sizes of 450 and 750 microns, respectively, were evaluated for their morphology and compressive properties using Scanning Electron Microscopy (SEM) and mechanical testing. The surface modification with plasma was conducted on PCL scaffold to increase the cellular attachment and proliferation. Our results suggested that inclusion of HA significantly increased the compressive modulus from 59 to 84 MPa for 60% porous scaffolds and from 30 to 76 MPa for 70% porous scaffolds. In vitro cell–scaffolds interaction study was carried out using primary fetal bovine osteoblasts to assess the feasibility of scaffolds for bone tissue engineering application. In addition, the results in surface hydrophilicity and roughness show that plasma surface modification can increase the hydrophilicity while introducing the nano-scale surface roughness on PCL surface. The cell proliferation and differentiation were calculated by Alamar Blue assay and by determining alkaline phosphatase activity. The osteoblasts were able to migrate and proliferate over the cultured time for both PCL as well as PCL-HA scaffolds. Our study demonstrated the viability of the PED process to the fabricate PCL and PCL-HA composite scaffolds having necessary mechanical property, structural integrity, controlled pore size and pore interconnectivity desired for bone tissue engineering.

Effect of plasma treatment on osteoblastic adhesion over poly (ε-caprolactone) scaffolds

Tissue engineering of bone is increasingly becoming the treatment of choice among surgeons to eliminate graft rejection, donor site morbidity and disease transmission problems. The ability of bone cells to produce an osteoid matrix on the scaffold can be affected by the quality of the cell-scaffold interaction. In this paper we report the use of dielectric barrier discharge plasma to improve adhesion and proliferation of bone cells, in particular osteoblast on poly (epsiv-caprolactone) (PCL) scaffolds. The surface treatment was carried out on PCL scaffolds with a custom made oxygen-based dielectric barrier discharge system (DBD). The effects of plasma treatment on PCL surface were characterized by assessing surface energy, surface topography, and surface chemistry. The surface energy of modified and unmodified PCL scaffolds was calculated by Owens-Wendts model using contact angle measurement data on these samples. The surface topography and the surface chemistry were evaluated by atomic force microscopy (AFM) and attenuated total reflectance Fourier-transformed infrared (ATR-FTIR) spectroscopy. The cell-substrate interaction study was carried out using mouse osteoblastic cell line 7F2 to examine the effect of oxygen plasma. Our results suggested that the oxygen plasma treatment not only enhances the hydrophilicity and increase solid surface energy of PCL but also improves the initial attachment, proliferation and migration of osteoblast on the PCL substrate.

Evaluation of 3D Hybrid Alginate/Single Wall Carbon Nanotube Tissue Scaffolds in Terms of Process and Cytocompatibility

Three-dimensional hybrid hydrogel tissue scaffolds of calcium alginate/single-walled carbon nanotubes (SWCNTs) composite were fabricated by solid freeform fabrication process in a multi-nozzle biopolymer deposition system. The scaffolds morphological, structural, mechanical and cytocompatibility properties were characterized. Except for a few areas, SWCNTs were evenly dispersed in the fabricated alginate scaffolds, and SWNTs were well aligned on the hydrogel surfaces from the SEM pictures. Raman spectroscopy showed that the structure of the Alginate/SWNT samples had been altered by the nanotube reinforcement. Microtensile test proved the reinforcement effect of SWNT to the mechanical strength of Alginate. Cell culture experiment for Rat Heart Endothelial Cell (RHEC) showed the cytocompatibility and biological enhancement of SWNTs to the Alginate substrate. In this manner, this type of biomaterial and scaffold possesses a good potential for future use in tissue engineering applications.

A combinatorial effect of plasma modification and protein coating on osteoblast differentiation for tissue engineering scaffolds

Summary form only given. Physical and chemical cues introduced on the microenvironment of cell may alter and regulate the cellular activity. Up to now, the positive effect of plasma modification and protein coating of biopolymer on cell attachment and proliferation has been studied excessively on planar surfaces1. However, based on our knowledge, the synergetic effect of plasma modification and protein coating on 3D scaffolds for long term cellular response including differentiation has not been studied. In this study, we investigated the combinatorial effect of adhesive protein coating and plasma modification on polycaprolactane (PCL) scaffolds for osteoblast differentiation compared to adhesive protein coating and plasma modification alone. We worked on four different groups of scaffolds; unmodified PCL (UP), plasma modified PCL (PP), fibronectin coated PCL (FNP) and plasma modified-fibronectin coated PCL (P-FNP). The surface characterization was done by contact angle measurement, surface energy calculation, surface roughness via atomic force microscopy, surface chemistry via X-ray photoelectron spectroscopy. The biological characterization was done through measuring strength of cellular adhesion, measuring rate of metabolic activity over time, observing early and later stage differentiation rate via alkaline phosphatase activity and osteocalcin secretion. Based on results, we found that rate of cellular differentiation strongly depends on the combination of physical, chemical and biological modification of PCL surfaces. More specifically, the early and later differentiation markers, the alkaline phosphatase activity and osteocalcin expression, increased more rapidly on plasma modified-fibronectin coated (P-FNP) scaffolds compared to UP, FNP, P-FNP.

Plasma Surface Modification of Three Dimensional Poly (ε-Caprolactone) Scaffolds for Tissue Engineering Application

In the present study, the effect of oxygen-based plasma treatment on the three dimensional poly (e-caprolactone) (PCL) was analyzed in terms of surface wettability, surface energy, and surface biocompatibility. The surface treatment was carried out for 1, 3, and 5-min durations on three dimensional PCL scaffolds at atmospheric pressure using a radio frequency (RF) plasma treatment system. The solid surface energies of the modified and unmodified PCL scaffolds were calculated by using the Owens-Wendt’s method. To examine the effect of oxygen plasma treatment on cell-scaffold interaction, mouse osteoblast cell line (7F2) was used. Oxygen plasma treatment contributed in decreasing the hydrophobicity of PCL for the 1-min treatment. A change in the surface energy from 39.98 mN/m for untreated to 52.54 mN/m for 1-min treated was observed by the increment in the polar component of surface energy. However, with the extended treatment times (3-min, and 5-min), the hydrophilicity, and the surface energy remained unaffected. The highest mouse osteoblast cells proliferation rate was observed for the 1-min treated sample.

Effect of Oxygen-Radio Frequency Plasma Treatment on Three Dimensional Poly(ε-Caprolactone) Scaffolds

In the present study, the effect of oxygen-based plasma treatment on the three dimensional poly (e-caprolactone) (PCL) was analyzed in terms of surface wettability, surface energy, and surface biocompatibility. The surface treatment was carried out for 1, 3, and 5 minutes durations on three dimensional PCL scaffolds at atmospheric pressure using a radio frequency (RF) plasma treatment system. The solid surface energies of the modified and unmodified PCL scaffolds were calculated by using the Owens-Wendt’s method. To examine the effect of oxygen plasma treatment on cell-scaffold interaction, mouse osteoblast cell line (7F2) was used. Oxygen plasma treatment contributed in decreasing the hydrophobicity of PCL for the 1-min treatment. A change in the surface energy from 39.98 mN/m for untreated to 52.54 mN/m for 1-min treated was observed by the increment in the polar component of surface energy. However, with the extended treatment times (3-min, and 5 min), the hydrophilicity, and the surface energy remained unaffected. The highest mouse osteoblast cells proliferation rate was observed for the 1-minute treated sample.Copyright