Development of Textile Structures with Material-Intrinsic Shape Changing Capabilities for Regenerative Medicine (TexMedActor)
In the IGF project 21022 BR/1 "TexMedActor", fabrics based on shape memory or electroactive yarns were developed which are capable of enclosing defects in hollow organs on the one hand and stimulating cells by micro-movements on the other. For this purpose, influences of spinning process and material composition on the shape memory behavior of TPU-based yarns were characterized and, in particular, the activation temperature was adjusted to values of the body core and body surface temperature. Furthermore, piezoelectric PVDF yarns were developed whose proportion of polar crystal phases was significantly increased by the spinning parameters and post-treatment, which also increased the piezoelectric behavior of the material. This allowed dynamic changes in pore size to be demonstrated in situ, which can have a stimulating effect on cells. With a new process and a new product group (textiles with intrinsic, active shape-changing capability), the results offer high innovation potential not only for medical devices, but also for a wide range of lucrative applications in a variety of niches, such as sports textiles and filter textiles. Furthermore, these can be used as a basis for the development of extracorporeal medical products such as compression textiles, bandages and orthoses.
Introduction and Objective
In Germany, both demographic changes in society and injuries resulting from trauma are leading to a high proportion of people with cardiovascular diseases or injuries to vessels and internal organs requiring treatment. Treatment of injuries to internal organs, vessels, or nerves usually requires complex procedures (anastomoses) that involve elaborate fixation and suturing. These complicated and elaborate procedures are often associated with long procedure times, which in turn directly correlate with increased complication rates [1-3]. Tubular plastic implants are increasingly being developed to bridge such defects. These single material structures do not allow tissue/ cell ingrowth. Therefore, they run counter to the concept of regenerative medicine, which aims to restore body tissues and cells. In addition, when the defects are filled, regeneration is often disturbed due to the structural-mechanical properties that are not adapted to biomechanics. Furthermore, the lack of interconnectivity of the pore spaces of the replacement structures prevents the cell ingrowth, cell growth, nutrient supply and the removal of metabolic products.
In the context of in vitro tissue engineering, in addition to static cell culture systems, dynamic systems are also being developed. These are based, for example, on continuous or pulsating fluid flows or on a cyclic stretching of a clamped cell support system or substrate . However, a replication of natural mechanical growth stimuli is not possible with such bioreactor systems because, especially in larger structures, there is a locally increased flow velocity along the largest pores or only an overflow of the entire cell support system. Additionally, undesirable stress peaks and undefined distortions occur in the region of the clamps and supports in mechanically stimulated systems.
Since the native structure of the four most important tissue types (connective and supporting tissue, nervous, muscular and epithelial tissue) from which organs, such as bones, blood vessels, muscles, tendons and ligaments, are formed, consists of fiber-like constructs, these can be particularly well biomimicked with textile structures. With the help of pre-designed fiber arrangements, three-dimensional, complex geometries with interconnecting pore spaces can be built up. The cells can use these structures to orient themselves in their growth direction . Therefore, fiber-based high-tech structures are particularly predestined to overcome the limitations of currently available implants.
Therefore, within the framework of the IGF research project TexMedActor (21022 BR/1) novel textile structures with material-intrinsic shape changing capabilities were developed for regenerative medicine with a variety of different application fields, especially anastomosis. The concept pursued envisages the textile-technological realization of structures with a shape memory effect. The textiles should be able to assume predetermined geometries in order to adapt interactively to defects and to simplify complex interventions to bridge or support defects in internal organs like vessel and nerves. Furthermore, these textiles are intended to enable electromechanical stimulation for the actively targeted stimulating of cell growth. In this way, regeneration is accelerated or even made possible in the first place, since the necessary stimuli for tissue- and cell-adapted growth stimulation are lacking, especially in the case of body tissues with weak or no blood supply, such as cartilage, tendons, ligaments, or in the case of wound healing disorders or chronic wounds. Furthermore, novel bioreactors based on the intrinsic properties of the textile structures will be developed, which use the mechanism of action for electromechanical stimulation to uniformly stimulate the cells at each site even in highly complex and large-scale cell carrier structures. Here, the mechanical stimuli originate from the material itself. This material-intrinsic stimulation represent a new method for optimal cell cultivation, by stimulating cell on the textile cell carrier structures without externally applied fluid flows or mechanical deformation. This is intended to overcome two recognized medical technology problems: 1) complicated, costly operations on internal organs, vessels or nerves that are difficult or impossible to perform with minimally invasive procedures, and 2) lack of tissue- and cell-adapted stimuli for promotion of growth in previously used replacement structures and materials as well as currently available dynamic cell culture systems.
The IGF project 21022 BR/1 of the Research Association Forschungskuratorium Textil e.V. was funded by the Federal Ministry of Economics and Climate Protection via the AiF within the framework of the program for the promotion of joint industrial research (IGF) on the basis of a resolution of the German Bundestag. We would like to thank the above-mentioned institutions for providing the financial resources. Furthermore, we want to thank the member of the “Projektbegleitender Ausschuss” (project accompanying committee) for their support during the project.