Fibrous bone tissue engineering scaffolds prepared by wet spinning of PLGA

Abstract

Having a self-healing capacity, bone is very well known to regenerate itself without leaving a scar. However, critical size defects due to trauma, tumor, disease, or infection involve bone graft surgeries in which complication rate is relatively at high levels. Bone tissue engineering appears as an alternative for grafting. Fibrous scaffolds are useful in tissue engineering applications since they have a high surface-to-volume ratio, and adjustable, highly interconnected porosity to enhance cell adhesion, survival, migration, and proliferation. They can be produced in a wide variety of fiber sizes and organizations. Wet spinning is a convenient way to produce fibrous scaffolds with consistent fiber size and good mechanical properties. In this study, a fibrous bone tissue engineering scaffold was produced using poly(lactic-co-glycolic acid) (PLGA). Different concentrations (20%, 25%, and 30%) of PLGA (PLA:PGA 75:25) (Mw = 66,000-107,000) were wet spun using coagulation baths composed of different ratios (75:25, 60:40, 50:50) of isopropanol and distilled water. Scanning electron microscopy (SEM) and in vitro degradation studies were performed to characterize the fibrous PLGA scaffolds. Mesenchymal stem cells were isolated from rat bone marrow, characterized by flow cytometry and seeded onto scaffolds to determine the most appropriate fibrous structure for cell proliferation. According to the results of SEM, degradation studies and cell proliferation assay, 20% PLGA wet spun in 60:40 coagulation bath was selected as the most successful condition for the preparation of wet-spun scaffolds. Wet spinning of different concentrations of PLGA (20%, 25%, 30%) dissolved in dichloromethane using different isopropanol:distilled water ratios of coagulation baths (75:25, 60:40, 50:50) were shown in this study.

Keywords: Biomaterials; PLGA; bone; rat bone marrow mesenchymal stem cells; tissue engineering; wet spinning.

Figure 1

Wet spinning setup.

Figure 2

Scanning electron micrographs of wet-spun PLGA (a, b, c) 20%, (d, e, f) 25%, and (g, h, i) 30% in (a, d, g) 50:50, (b, e, h) 60:40, and (c, f, i) 75:25 (Isopropanol: dH2O) coagulation baths. 200× magnification.

Figure 3

The rate of (a) weight loss and (b) pH decreasing as a function of time (days) (*P < 0.05) during biodegradation of fibrous PLGA scaffold.

Figure 4

Scanning electron micrographs of wet-spun PLGA at the end of 90 days of incubation period; a) 20%-60-40, b) 25%-60-40, c) 30%-60-40, d) 25%-75-25, e) 30%-75-25.

Figure 5

Flow cytometry histograms of rBMSCs a) Negative control; labeled with (b) CD45, (c) CD11A, (d) CD31, (e) CD29, (f) CD90 antibodies.

Figure 6

Cell proliferation on different PLGA scaffolds (20%-60-40, 25%-60-40, 25%-75-25, 30%-60-40, and 30%-75-25) after 7, 14, and 21 days of incubation. Initial cell seeding was 2 × 104 cells/sample (*P < 0.05). Indent on the top right corner shows the cell proliferation on Tissue Culture Plate and OC stands for the cells seeded into wells of the tissue culture plate (only cell).

Figure 7

Scanning electron micrographs of MSCs seeded onto the PLGA fibers (20%-60-40) at day 10 (a) and 20 (b) with 200× magnification.