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Biomaterials

Biomaterials - Poster Session E

Poster N18 - Forming fibroin fibers through contact drawing

Saturday, October 26, 2024
10:00 AM - 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Silks have been extensively studied for their desirable mechanical properties. Fibroin, extracted from Bombyx mori silk, has gained attention because of its outstanding mechanical properties, biocompatibility, biodegradability, and environmental stability. [1] A variety of strategies [2,3] have now been developed and demonstrated to modify native fibroin before or after fiber spinning to further improve its mechanical properties from applications in textiles, sensors and biomedicine.[1,3] However, large-scale implementation of fibroin in these applications is hindered by limitations with current manufacturing processes. Wet-spinning and electrospinning remain the primary processes for producing fibroin fibers, but each has associated drawbacks with a major drawback for both being limited scalability. Contact drawing (Figure 1) is an emerging manufacturing technique for fibers that has potential to address the scalability issues associated with electro and wet spinning. [4,5]
Contact drawing is a dry spinning method for fiber formation relying on (1) a substrate and pin array tool and (2) dope solution. Fibers are formed by spreading the viscous dope solution containing the protein and a scaffolding polymer on the substrate tool. A pin array tool is brought into contact with the dope solution and pulled apart to form uniform fibers. The number of fabricated fibers can be readily adjusted through the design of the pin array and the number of pulls that are carried out (Figure 1). Despite its simplicity and efficacy, the use of contact drawing has so far been limited to collagen and synthetic polymer fibers.

Materials and

Methods:  Material – Fibroin (derived from Bombyx mori) was purchased from Zhongxin Chuangwei Biotech (Hangzhou). Poly(ethylene oxide) (PEO) was purchased from Aldrich Chemistry.
Contact drawing – The contact drawing system consists of three components: a substrate tool, a pin array tool, and a hollow collection container. The tools were printed using an ELEGOO Mars 4 3D printer with B9R-2-Black resin (B9Creations). The substrate tool was a printed flat rectangular plate and the pin array tool consisted of a flat rectangular base with either a 1x7 or 9x9 array of pins, with a height of 6 mm, a diameter of 0.6 mm, and a center-to-center spacing of 10 mm or 2 mm.
Fibroin was solubilized using a mixture of formic acid and acetic acid. PEO (1 %w/v) was added once the protein was fully solubilized. The mixture was allowed to form a homogeneous gel through incubation at 4 °C for 19-22 h. The gel was applied to the substrate tool through spreading to a visibly homogeneous state. The pin array tool was brought into contact with the gel-covered substrate tool before pulling them apart to produce fibroin fibers. The drawn fibers were collected and dried over a collection container of 12 cm by 9.5 cm.
Light microscopy – The optical microscopy measurements of the fibers were performed using an Axio Observer A1 from Carl Zeiss Canada (Toronto, ON) with 100x magnification. The diameter was determined using ImageJ.

Results, Conclusions, and Discussions: In the current study, a new contact drawing protocol was developed and optimized to allow robust formation of fibroin fibers. To achieve the required high viscosity of the dope solution, a polymer was added in a low concentration to the solubilized fibroin. Different concentrations of fibroin in the dope solution, from 5 to 20 % w/v, were investigated and all conditions successfully formed single fibroin filaments. The formed fibers displayed diameters ranging from 4 to 13 µm. After confirming the formation of fibroin monofilaments through contact drawing, fibroin multifilaments were formed by adapting the pin array tool from a 1x7 to a 9x9 set up and twisting monofilaments to form a multifilament. Thereby, the diameter of the resulting fibers was easily adapted form tens of micrometers to hundreds of micrometers. The study highlights the successful formation of fibroin fibers though a novel approach as well as the simplicity of adapting the diameter of the fibers and their properties.

References: [1] L.-D. Koh, Progress in Polymer Science, 2015, 46, 86–110. [2] H. A. Tran, Materials Today, 2023, 65, 244–259. [3] S. Chai, Adv Materials Technologies, 2024, 9, 2301659. [4] S. J. Baldwin, ACS Appl. Polym. Mater., 2021, 3, 4245–4255. [5] H. Yaghoobi, Macromol. Rapid Commun., 2023, 2300204.

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