Electrospinning is useful for fabricating nanofibrous structure with different composition and morphologies. It offers great advantages through its geometrical structure and biomimetic property, which can provide a suitable environmental site for cell growth. The fiber diameter is entangled by the concentration of PCL with some adjustment of parameters during electrospinning process. PCL with lower concentration had bead structure while higher concentration had smooth fiber. The incorporation of nanoparticle hydroxyapatite (nHA) into poly(
Bone is a nanostructured biomaterial with unique biological and mechanical properties. It consists of inorganic hydroxyapatite crystal, organic type I collagen fibers, and other proteins [
Nanofibrous scaffold offers great advantages such as the large surface area to volume ratio, with pore structure characteristic, and it can mimic the natural extracellular matrix which is beneficial for cell growth. Among the various techniques of scaffold fabrication, electrospinning can be described as simple and most reliable for producing long and continuous fibers [
The scaffold may come from natural and synthetic materials. Synthetic polymer poly(
In this study, nanoparticle hydroxyapatite (nHA) incorporation into PCL fiber was investigated through the dispersibility of nHA within the fiber. The surface of the fiber was modified by immersion in a simulated body fluid (SBF) to mimic the mineral of native bone. PCL is a synthetic polymer. So, it may be extremely difficult to induce mineralization because PCL had very few ionic molecular groups compared to natural polymers such as chitosan and collagen. The existence of HA within PCL polymer fibers could improve the surface mineralization process.
PCL with molecular weight 70,000 to 90,000 and acetone (99.8%) were purchased from Sigma-Aldrich. Nanoparticle HA was synthesized by nanoemulsion technique produced in-house from the previous study [
PCL was dissolved in acetone solvent at a concentration of 7.5% (w/v) and 12.5% (w/v) at 40°C. HA powder was suspended into the solution at a concentration of 10% (w/w) and 20% (w/w), respectively. The mixed solution was stirred at room temperature for 24 h and homogenized using homogenizer (IKA T25, IKA works, Germany).
The prepared solution was transferred into a 5 mL syringe, with 18 and 22 G blunt-end needle. The electrospinning was conducted using electrospinning unit (NaBond, China). The distance between the needle tip and aluminium collector was adjusted at 10 cm. High voltage of 15–22 kV was applied to the needle. The solution was ejected at a feeding rate of 3 mL/h using infusion pump (Veryark TCV-IV, China). The resulting fiber was dried overnight to remove any solvent left on its surface.
The bioactivity test was done by immersing the fibers in SBF. The SBF was prepared in accordance with Kokubo et al. [
The morphology of the fibers was observed under SEM (Hitachi TM 3000, Japan) at an accelerating voltage of 15 kV and FESEM (Hitachi SU 8020, Japan). The fibers immersed in SBF analyzed by FESEM were gold-coated prior to analysis. The diameter of single fiber was measured at random location using image analysis software (Image J, NIH, USA). Energy dispersive X-ray (EDX) was used to confirm the presence of HA in the PCL polymer.
Water contact angle was measured by dropping deionized water (3
Water uptake of the fiber was measured to see how much water can be absorbed, which mainly depends on the hydrophilicity of the fiber. The fiber before immersion in SBF was cut into
Figure
SEM micrographs of fibers at different compositions: (a) 7.5% (w/v) PCL; (b) 12.5% (w/v) PCL; (c) 7.5% (w/v) PCL with 10% (w/w) nHA; (d) 7.5% (w/v) PCL with 20% nHA; (e) 12.5% (w/v) PCL with 10% (w/w) nHA; (f) 12.5% (w/v) PCL with 10% (w/w).
The ability of forming apatite onto the fiber was evaluated through soaking them in SBF for 3, 7, and 14 days using a sample of 7.5% (w/v) PCL and 7.5% (w/v) PCL with 10% (w/w) nHA. When the sample was immersed into SBF, PCL fiber was floated suggesting that high hydrophobic surface prevents water absorption. Meanwhile, composite fiber settled down to the bottom dish suggesting the fiber was high in density. It also showed faster absorption of water into the fiber. From Figure
FESEM micrographs of 7.5% (w/v) PCL fiber immersed in SBF after (a) 3 days, (b) 7 days; (c) 7.5% (w/v) PCL with 10% (w/w) nHA immersed in SBF after 3 days, (d) 7 days, and (e) 14 days.
(a) An EDX spectrum and (b) Ca distribution on PCL with 10% (w/w) nHA immersed in SBF after 7 days.
The wettability of the fiber was determined using contact angle. The desired scaffold property for cell interaction is hydrophilic surface. Table
Contact angle measurement of fibers at different PCL and HA concentration.
Composition | 0% HA/7.5% PCL | 10% HA/7.5% PCL | 20% HA/7.5% PCL | 0% HA/12.5% PCL | 10% HA/12.5% PCL | 20% HA/12.5% PCL |
---|---|---|---|---|---|---|
Contact angle | 127.3 ± 2.4 |
112.7 ± 3.1 |
106.3 ± 4.5 |
120.5 ± 2.2 |
115.1 ± 4.1 |
93.7 ± 3.6 |
Figure
Water uptake of PCL fiber and PCL/HA fibers in (a) deionized water over time (minutes) and (b) in simulated body fluid (SBF) over time (days).
The water uptake of the fiber immersed in SBF was measured as in Figure
Using the electrospinning technique, beadless HA/PCL nanofiber was obtained. Immersion in SBF showed 7.5% (w/v) PCL with 10% (w/w) nHA fiber had good bioactivity up to seven days compared to PCL fiber. Contact angle and water uptake showed that the composite PCL/nHA fibers were more hydrophilic than PCL fiber. The water uptake property was also greater in the composite fibers than pure PCL fiber. The composite electrospun fiber of PCL with osteoconductive nHA is expected to be conducive for osteoblast growth for bone tissue regeneration.
The authors declare that there is no conflict of interests.
The authors would like to acknowledge the Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia (UTM), for the lab facilities. This work was supported by research Grants GUP Tier 1 (05H07). The authors are also thankful for the support given by MOHE, RMC, and UTM.