Poster 64 - Engineering Polymer Nanoyarns for Biomedical Applications

Saturday, October 26, 2024

10:00 AM - 12:00 PM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Adam Freedman (he/him/his)

High School Researcher
Rowan University
Mount Laurel, New Jersey, United States

Primary Investigator(s)

VB

Vince Beachley

ASSOCIATE PROFESSOR & GRADUATE PROGRAM CHAIR
Rowan University, United States

Co-Author(s)

Dominique Hassinger

Graduate Research Assistant
Rowan University
Franklin, New Jersey, United States

Introduction: Polylactic acid (PLA) and polycaprolactone (PCL) both exhibit biodegradable and biocompatible properties, making them excellent materials for biomedical applications [3]. Like many other polymers, they can be electrospun, a process that uses a potential difference to stretch polymers into nanofibers. These nanofibers (with diameters less than 1 μm) can be wound into nanoyarns. Nanoyarns aren’t new in the biomedical field, having already been used to create textiles for personal protective equipment, scaffolds for tissue engineering, and surgical sutures (the main focus of this study) [3]. Due to the biodegradable and biocompatible nature of PCL and PLA, sutures made of their nanoyarns can degrade in the body. Additionally, the nanofiber structure of polymer nanoyarns can create an environment that promotes wound healing, since cells have been observed to align well with nanofibers (figure 1) [2]. However, using nanoyarns for surgical sutures does have downsides. They exhibit lower mechanical properties than traditional sutures [3], can cause inflammation due to their hydrophobic nature, and their degradation properties can limit them to surgeries that do not require sutures to retain their mechanical properties long term. In this study, the mechanical properties of 12.5% PLA and 18% PCL nanofibers and nanoyarns were investigated to determine whether application as a suture would be feasible.

Materials and

Methods: Materials used were PLA Filament and PCL beads, Dichloromethane (DCM), Dimethylformamide (DMF), electrospinning apparatus (figure 2a), mechanical tester (figure 2c and 2d), yarn spinning apparatus (figure 2b), and plastic frames (figure 2c).

To create the polymer solution filament/beads are massed by multiplying desired concentration by solvent volume (Ex: 12.5% * 12 mL = 1.5 g). Then, provided ratios of organic solvent (3:1 Ratio of DCM to DMF) were used to create the polymer solution.

Rowan University's electrospinning device consists of two rotating, grounded parallel tracks used to create aligned fibers (figure 2a). The PLA and PCL nanofibers were collected on a rack for 5 minutes for frames, and continuously collected on a spinning roller of parchment paper for the nanoyarns. The parameters for electrospinning are seen in table 1.

To make the yarns, initial fibers on the continuous collecter were bunched by hand and attached to the spool of the yarn spinning device seen in figure 2b. The device twists fibers into yarns and gathers the yarns simultaneously using two motors. These motors work together to impart a twist and uptake the yarn. The complete yarn is transferred from collection bobbin to storage bobbin.

For mechanical testing, United States Pharmacopeia (USP) 41 testing protocls were followed (figure 2d) for the yarns. For the frames, the operating speed on the mechanical tester was set to 5 mm/min for both PLA and PCL (figure 2c). After testing, stress/strain curves for both yarns and fibers were created (figure 4).

Results, Conclusions, and Discussions: Fibers:
Fibers were counted along a frame containing nanofibers electrospun for 5 minutes. The average fiber count for PLA (n=6) and PCL (n=6) was 505 ± 150 and 1000 ± 221 respectively (p = 0.128). A scanning electron microscope was used to image and measure fibers (figure 3). The average diameter of a PLA (n=5) fiber was 945 nm ± 552, and the average diameter of a PCL (n=6) fiber was 722 nm ± 154 (p = 0.412). For PLA (n=6) the ultimate tensile strength (UTS) was 29.432 MPa ± 17.79, and for PCL (n=6) the UTS was 427.82 MPa ± 93.72 (p = 0.0002). At the UTS, strain was 0.354 ± 0.113 for PLA fibers (n=6) and 1.02 ± 0.0781 for PCL fibers (n=6) respectively (p = 0.00002). PLA (n=6) had a Young's modulus of 0.857 GPa ± 0.611. PCL (n=6) had a modulus of 1.17 GPa ± 0.402 (p = 0.366).

Nanoyarns:
The mass and length of the nanoyarns were collected and the linear density was reported in denier (g/9km). PLA (n=3) had an average linear density of 116.3 den ± 41 and PCL (n=3) had an average linear density of 131.7 den ± 36 (p = 0.748). The tenacity is the maximum measured force divided by the linear density. The average tenacity of PLA (n=3) and PCL (n=3) nanoyarns were 1.6E4 N*m/kg ± 5.8E3 and 1.14E5 N*m/kg ± 3.68E4 respectively (p = 0.07). The Young’s modulus for PLA (n=3) was 64.9 MPa ± 55.3 and for PCL (n=3) it was 81.9 MPa ± 37.8 (p = 0.45). UTS for nanoyarns is tenacity times bulk density, which is 1.24 g/cm^3 for PLA and 1.145g/cm^3 for PCL. PLA (n=3) had a UTS of 39.656 MPa ± 7.21 and PCL (n=3) had a UTS of 131.07 MPa ± 42.22 (p = 0.08).

Conclusion:
PCL and PLA nanofibers were successfully fabricated and tested. A significant difference (with α = 0.05) was found for the UTS and strain at the UTS between the two nanofibers, both being greater for PCL. There was no significant difference for any properties of the yarns.

Acknowledgements (Optional): U.S. National Science Foundation
Rowan-Virtua School of Translational Biomedical Engineering and Sciences
RISER Program
Mentors: Dominique Hassinger, Varsha Prahaladan
Principle Investigator: Dr. Vince Beachley
Nominating Teacher: Tara Sharp

References (Optional): 1. Zhang, X., Guo, M., Guo, Q., Liu, N., Wang, Y., & Wu, T. (2023a). Modulating axonal growth and neural stem cell migration with the use of uniaxially aligned nanofiber yarns welded with NGF-loaded microparticles. Materials Today Advances, 17, 100343. http://doi.org/10.1016/j.mtadv.2023.100343
2. Xue, J., Wu, T., & Xia, Y. (2018). Perspective: Aligned arrays of electrospun nanofibers for directing cell migration. APL Materials, 6(12). https://doi.org/10.1063/1.5058083
3. Wu, S., Dong, T., Li, Y., Sun, M., Qi, Y., Liu, J., Kuss, M. A., Chen, S., & Duan, B. (2022). State-of-the-art review of advanced electrospun nanofiber yarn-based textiles for biomedical applications. Applied Materials Today, 27, 101473. https://doi.org/10.1016/j.apmt.2022.101473