Tailoring surface nanoroughness of electrospun scaffolds for skeletaltissue engineering
Author and unit
Sita M.DamarajuaYueyangShenbEzinwaElelebBorisKhusidbAhmadEshghinejadcJiangyuLicdMichaelJaffeaTreena LivingstonArinzeha
Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ 07102-1982, USA
Department of Chemical, Biological and Pharmaceutical Engineering, New Jersey Institute of Technology, Newark, NJ 07102-1982, USA
Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA
Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, Guangdong, China
Joumal Impact Factor：8.402
Received 6 July 2017,
Revised 8 September 2017,
Accepted 17 September 2017,
Available online 19 September 2017.
The discovery of electric fields in biological tissues has led to efforts in developing technologies utilizing electrical stimulation for therapeutic applications. Native tissues, such as cartilage and bone, exhibit piezoelectric behavior, wherein electrical activity can be generated due to mechanical deformation. Yet, the use of piezoelectric materials have largely been unexplored as a potential strategy in tissue engineering, wherein a piezoelectric biomaterial acts as a scaffold to promote cell behavior and the formation of large tissues. Here we show, for the first time, that piezoelectric materials can be fabricated into flexible, three-dimensional fibrous scaffolds and can be used to stimulate human mesenchymal stem cell differentiation and corresponding extracellular matrix/tissue formation in physiological loading conditions. Piezoelectric scaffolds that exhibit low voltage output, or streaming potential, promoted chondrogenic differentiation and piezoelectric scaffolds with a high voltage output promoted osteogenic differentiation. Electromechanical stimulus promoted greater differentiation than mechanical loading alone. Results demonstrate the additive effect of electromechanical stimulus on stem cell differentiation, which is an important design consideration for tissue engineering scaffolds. Piezoelectric, smart materials are attractive as scaffolds for regenerative medicine strategies due to their inherent electrical properties without the need for external power sources for electrical stimulation.
Fig. 1. Picture of piezoelectric scaffolds, approximately 3 mm thick. Scale bar = 6 mm (A). Scanning electron microscope (SEM) images of as-spun PVDF-TrFE (B), annealed PVDF-TrFE (C) and PCL (D) at 2000× magnification. Scale bar = 20 μm. Setup for measuring the electrical output of the piezoelectric scaffolds in dry conditions. (E) Top-down view of the electrical testing setup where the piezoelectric material is sandwiched between copper tape (scale bar = 63.5 mm) (E), side-view (F) and schematic of the testing device where force is applied and recording made by the oscilloscope (G). Corresponding graphs of electric output for as-spun (H) and annealed PVDF-TrFE scaffolds (I) in dry conditions undergoing dynamic compression. Note the difference in the values of the y-axis.
Fig. 2. The displacement amplitude and phase of the PFM switching at different locations on the as-spun PVDF-TrFE (A & B), annealed PVDF-TrFE (C & D) and PCL (E & F) fibers.
Fig. 3. Representative gross images and histological images of scaffolds after 28 days undergoing chondrogenesis in dynamic conditions. Gross images of as-spun PVDF-TrFE (A), annealed PVDF-TrFE (B) and PCL (C) scaffolds. Histological staining for proteoglycans (safranin-O) (D–F) and immunohistochemical staining for collagen type II (G–I) and collagen type I (J–L) of as-spun PVDF-TrFE (D, G, and J), annealed PVDF-TrFE (E, H, and K) and PCL (F, I and L) scaffolds. (Scale bars: A-C, 6 mm; D-L, 100 mm). Biochemical analysis for MSCs undergoing chondrogenesis on as-spun PVDF-TrFE, annealed PVDF-TrFE and PCL scaffolds. Graphs show cell number (M), total GAG production (N), collagen type II production (O), collagen type I production (P) where dynamic (DYN) is normalized to perfusion only (PERF) groups and collagen types II/I ratio in DYN conditions (Q) at day 28. # p < 0.05, significant difference between groups at day 28. ˆp < 0.05, significant difference between time points. * p < 0.05, all three groups are significantly different.
Fig. 4. Representative gross images and histological evaluation of scaffolds after 28 days undergoing osteogenic differentiation in dynamic conditions. Gross images of as-spun PVDF-TrFE (A), annealed PVDF-TrFE (B) and PCL (C) scaffolds. Immunohistochemical staining for collagen type I of as-spun PVDF-TrFE (D), annealed PVDF-TrFE (E) and PCL (F) scaffolds. (Scale bars: A-C, 6 mm; D-F, 100 μm). Biochemical analysis for MSCs undergoing osteogenesis on as-spun PVDF-TrFE, annealed PVDF-TrFE and PCL scaffolds. Graphs show cell number at days 14 and 28 (G), total alkaline phosphatase activity (H), and mineralization (I) where dynamic (DYN) is normalized to perfusion only (PERF) groups. # p < 0.05, significant difference between groups at day 28. * p < 0.05, all three groups are significantly different.
Piezoelectric materials hold promise as a scaffold strategy to enhance tissue formation by providing a smart, electrically active microenvironment without the use of an external power source. Here, we show that piezoelectric materials can be fabricated into flexible, three-dimensional fibrous scaffolds that can be used to stimulate mesenchymal stem cell differentiation and tissue formation when undergoing dynamic loading, which mimics physiological loading conditions found in structural tissues. Findings demonstrate the potential of piezoelectric scaffolds as a viable approach to regenerate tissues using stem cell-based therapies.