Development of a Device to Fabricate Sutures Coated with Functionalized Electrospun Nanofibers

Adam Samuta, Jorge Rodriguez Ph.D, and fellow CI members

Introduction

Composite materials have become of great importance in the biomedical field due to their vast applications. Nanofibers fabricated with electrospinning technology have been proven useful as a result of their ability to mimic the human Extracellular Matrix (ECM). The objective of this project was to design and prototype a mechanism to fabricate composite core-shell yarns that coat sutures with electospun fibers. The automated device facilitates the wrapping and coating of the core with electrospun fibers, thus creating functionalized sutures with multiple biomedical applications.

Materials and Methods

Our device used to apply the fibers produced by electrospinning to sutures was designed and machined to be variable for an array of testing parameters, including nanofiber brush collector size, material, and rotational speed. To optimize the rotational velocity of steel brush heads for production of samples, a simple PLLA polymer was melted and mixed with DCM for extrusion. This polymer was electrospun into fibers with a flow rate of 1.50 mL/hr using a voltage difference of 7.97 kV between the syringe and grounded rotating collection apparatus. After one hour of extrusion, the fibers were collected with the brush heads of the device and spun into a silk with the brush heads rotating in opposite directions at 150 rpm. Following the spinning, the wrapped fibers were cut from the brush heads. Next, another sample group was prepared the same way, but a 4-0 braided suture was strung through the device and the fibers were wrap around the suture at 150 rpm. The final sample was prepared, and a suture was strung through the device, but a speed of 76 rpm was used to apply the fibers to the suture. To analyze the samples and determine the best speed for the brush heads to coat the sutures, scanning electron microscopy(SEM) was used to compare each samples’ fiber alignment and size (Figures 1 and 2).

Results

Nanofiber alignment can be observed at the SEM images taken of the two fiber-coated sutures prepared by our device (Figures 1 and 2). It is evident that samples run with 76 rpm are ideal for a tight twisting of the fibers using steel brush heads. Both tests were run with the same amount of fibers attached to the brush heads, the samples made with 76 rpm (Figure 1) had the most even coating of the suture, as well as a higher angle of fiber alignment. This shows that the lower rpm produces better results for overall suture coverage with the fibers. Also, having the higher angle of fiber alignment with the lower rotational velocity sample, the fibers were more tightly wrap around the suture itself.

Figure 1. (Left) The SEM image taken at 150x magnification of the PLLA fibers wrapped around a suture prepared with brush head speeds of 76 rpm.

Figure 2. (Right) The SEM image taken at 150x magnification of the PLLA fibers wrapped around a suture prepared with brush head speeds of 150 rpm

Automization

Since the finish of this experiment, the device has added an automated lifting mechanism that allows for controlled fiber collection rate as well as a user interface system for ease of operation. This user interface system allows the user to control individual variables dependent on motor speed, and rate of fiber collection which is dependent on apparatus lifting rate and brush head rotational collection speed. The automated lifting mechanisms allows for more accurate methods of fiber collection, while the user interface allows for testing parameters to be more controlled and expanded.

Conclusions

From this optimization experiment, it can be concluded that, for steel brush heads, our device produces the best fiber-wrapped sutures at lower rotational velocities. Moving forward, more testing will be done to determine the ideal electrospinning fiber application parameters for our machined device. Some of these parameters include: brush head materials, brush head size, fiber application time, fiber orientation, fiber collecting rate, and storage methods. The development of this device’s user interface system provides a standardized method of electrospinning treated fibers to sutures, allowing for consistent samples of these wrapped sutures for use in future research exploring the possibilities presented by functionalized surgical sutures.