Introduction: Various suture materials and sizes are employed across many types of surgery including orthopedic and sports medicine surgeries like rotator cuff repair (RCR). Currently, non-absorbable or partially absorbable sutures are favored in RCR for their high strength; however, this may not be ideal. Stress shielding can occur which hinders regeneration and tissue remodeling at the tendon-to-bone interface. A medical suture developed from nanofiber is a promising candidate for a resorbable suture with enhanced therapeutic outcomes. The small diameter of nanofibers results in a large surface-area-volume -ratio which is favorable environment for cell attachment and mimics the structure of extracellular matrix. These features make nanofibers superior for tissue engineering scaffolds compared to microfibers which have reduced cellular activities and lesser therapeutic effects[3].
Nanoyarns, though possessing desired features of nanofibers, have shortcomings as result of fabrication techniques. Current methods for assembly of nanoyarns result in nanoyarns that inferior to their microyarn counterparts due to poor mechanics, limited yarn lengths and randomly aligned fibers.[3] The collection of electrospun fibers onto a custom parallel track collector has been explored with much success[4] This method allows for highly aligned nanofibers, collection onto a continuous roll and post drawing of fibers. Nanoyarns created from nanofiber sheets fabricated by this method can address many of the limitations of current nanoyarn fabrication techniques by enhancing mechanical properties through aligned fiber and creating longer yarns through continuous collection. By utilizing technology of aligned nanofibers for nanoyarn fabrication, we aim to create a nanoyarn as a potential fully resorbable suture.
Materials and
Methods: Nanoyarns were created via means of electrospinning. 16% w/v polylactic acid (PLA) solution and 18% w/v polycaprolactone solutions were created and electrospun to nanofibers. The solutions are electrospun onto our lab's novel custom parallel track electrospinning collector, post-drawn to enhance strength, and deposited in aligned orientation on to a continuous roll to facilitate roll-to-roll fabrication. Following collection, the sheet of nanofibers is formed into a yarn through use of an in-house, custom-built spinner which allows for controlled over linear density and twists per inch. Yarns are collected onto a bobbin to be used for later testing. The custom parallel track to continuous roll-to-roll collector system and custom-built yarn spinner are pictured in Figure 1. PLA and PCL microfiber monofilament wase created by means of wet spinning of each respective polymer for controls. All fabricated materials were subjected to the US Pharmacopeia (USP) tensile testing protocol for sutures. All materials underwent degradation in PBS for a duration of 0,3,5,7, and 14 days. After incubation in PBS, yarn segments were weighed and underwent USP testing once again. Additionally, cell attachment, and two types of suture retention tests were deployed to capture the suture qualities of the fabricated materials.
Results, Conclusions, and Discussions: We have shown that PCL nanoyarns fabricated through use of our lab's unique parallel track system and custom yarn spinner is feasible and that resulting post-drawn yarns have an increase in mechanical properties compared to their counterparts that are not post drawn. This research highlights the potential of nanoyarns to fill the need of fully resorbable sutures in sports medicine applications.
