Cellulose nanofiber based composites for use as ligament or tendon substitute

Cellulose nanofibers were isolated from softwood pulp by mechanical fibrillation process and were utilized to develop biobased nanocomposites for biomedical application. Different processing techniques were attempted to develop nanocomposites for use as artificial ligament or tendon and the composites mechanical properties at room conditions as well as at simulated body condition (37 °C and 98 % RH) were studied. These initial studies indicated that the inherent properties like low toxicity, biocompatibility and biodegradability together with excellent mechanical properties of nanocelluloses makes cellulose based nanocomposites an excellent candidate for load bearing components in biomedical applications. INTRODUCTION Although significant progress has been made toward understanding the anatomy, composition, biomechanics and healing of ligaments and tendons there are still no graft or prosthesis ideally suited to substitute natural ligaments/tendons so far. Natural tendons and ligaments are capable of withstanding high stresses and during the 1970s and 80s, various synthetic materials were designed to act as a permanent ligament/tendon replacement devices. Synthetic polymers clinically evaluated for ACL reconstruction include polytetrafluoroethylene (GoreTex), polyethylene terephthalate (Dacron; Stryker-Meadox and Leeds-Keio ligaments), carbon fibres (Integraft), and braided polypropylene (Kennedy Ligament Augmentation Device). , In fact, these materials did not possess the same biomechanical properties of the native structure and were known to fatigue, stretch, and/or particulate over time. Though there are reports on development of composite materials for biomedical applications, especially for tendon and ligament replacement, most of them are based on synthetic polymers. , , 6 Research in the field of artificial ligaments and tendons indicates that mechanical performance comparable to that of natural ligaments/tendons and biocompatibility are the primary requirements for materials considered for artificial ligament /tendon application. The current report is unique because of the use of biobased raw materials with remarkable mechanical properties for developing the ligament or tendon substitute. The nanocellulose fibres were isolated from wood using chemical and mechanical treatments and were utilized to develop composite materials having mechanical properties similar or better than natural ligaments or tendons. Nanosized cellulose fibers used is expected to result in a homogeneous and uniform product as well as improved fibrematrix interaction owing to high surface area available for nanocelluloses. The processing and properties of the nanocomposites, especially in the body conditions of 37° C and high relative humidity conditions (98 %) are reported here. This study is expected to provide valuable insights on the use of nanosized cellulose fibres in the development of artificial ligaments and tendons. The in vitro biocompatibility studies on these nanofiber based composites materials were looked into and were finally fabricated into a prototypes and is being evaluated for in vivo bio mechanical performance. EXPERIMENTAL Materials Collagen fibres obtained from horse tendons by pH induced regeneration (Resorba, Germany) and cellulose nanofibres were produced out of never dried softwood pulp by mechanical fibrillation. The ionic liquid used for cellulose as well as the crosslinking agents for collagen was procured from Sigma Aldrich GmH, Germany. Processing of nanocomposites Composite 1. The nanofiber networks were prepared from cellulose nanofiber suspensions and treated with ionic liquid to prepare partially dissolved networks which is then precipitated and washed with water to remove the residual reagents and dried to obtain flat films Composite 2. Cellulose nanofiber suspensions were thoroughly mixed with collagen suspensions and casted on Petri dishes to obtain flat films. The films were neutralised and subsequently treated with cross linking agents to obtain uncross linked and cross slinked composites respectively. These films were washed thoroughly and dried in a vacuum oven.