Biofabrication of bundles of poly(lactic acid)-collagen blends mimicking the fascicles of the human Achille tendon

Abstract

Electrospinning is a promising technique for the production of scaffolds aimed at the regeneration of soft tissues. The aim of this work was to develop electrospun bundles mimicking the architecture and mechanical properties of the fascicles of the human Achille tendon. Two different blends of poly(L-lactic acid) (PLLA) and collagen (Coll) were tested, PLLA/Coll-75/25 and PLLA/Coll-50/50, and compared with bundles of pure PLLA. First, a complete physico-chemical characterization was performed on non-woven mats made of randomly arranged fibers. The presence of collagen in the fibers was assessed by thermogravimetric analysis, differential scanning calorimetry and water contact angle measurements. The collagen release in phosphate buffer solution (PBS) was evaluated for 14 days: results showed that collagen loss was about 50% for PLLA/Coll-75/25 and 70% for PLLA/Coll-50/50. In the bundles, the individual fibers had a diameter of 0.48 ± 0.14 μm (PLLA), 0.31 ± 0.09 μm (PLLA/Coll-75/25), 0.33 ± 0.08 μm (PLLA/Coll-50/50), whereas bundle diameter was in the range 300-500 μm for all samples. Monotonic tensile tests were performed to measure the mechanical properties of PLLA bundles (as-spun) and of PLLA/Coll-75/25 and PLLA/Coll-50/50 bundles (as-spun, and after 48 h, 7 days and 14 days in PBS). The most promising material was the PLLA/Coll-75/25 blend with a Young modulus of 98.6 ± 12.4 MPa (as-spun) and 205.1 ± 73.0 MPa (after 14 days in PBS). Its failure stress was 14.2 ± 0.7 MPa (as-spun) and 6.8 ± 0.6 MPa (after 14 days in PBS). Pure PLLA withstood slightly lower stress than the PLLA/Coll-75/25 while PLLA/Coll-50/50 had a brittle behavior. Human-derived tenocytes were used for cellular tests. A good cell adhesion and viability after 14 day culture was observed. This study has therefore demonstrated the feasibility of fabricating electrospun bundles with multiscale structure and mechanical properties similar to the human tendon.

Hierarchical electrospun tendon‐ligament bioinspired scaffolds induce changes in fibroblasts morphology under static and dynamic conditions

“…In order to reproduce the morphology of tendon and ligament fibrils and fascicles (Kannus, 2000;Murphy et al, 2016), electrospun bundles (cross-sectional diameter = 550-650 µm) of aligned nanofibres (cross-sectional diameter of the nanofibres = 0.36 ± 0.06 µm) of a PLLA/Coll-75/25 (w/w) blend were produced as previously described (Sensini et al, 2017(Sensini et al, , 2018a. To obtain the bundles the following electrospinning parameters were used: a rotating drum collector (peripheral speed = 22.8 m s −1 ); the polymer solution was delivered through two needles (internal diameter 0.51 mm); room temperature (RT) and relative humidity 20-30%; applied voltage = 22 kV; feed rate = 0.5 mL h −1 , electrospinning time = 2 h; needles-collector distance = 200 mm; the sliding spinneret with the two needles had an excursion of 120 mm, with a sliding speed of 1200 mm min −1 .…”

Biodegradable polymer nanocomposites for ligament/tendon tissue engineering

“…A good cell attachment and viability after 14 days of culture was observed. However, cells exhibited a better adhesion on PLLA/Coll-50/50 bundles and a more elongated morphology in comparison to PLLA/Coll-75/25 one [104].…”

“…However, their quick degradability and low-mechanical properties may limit their application in tissue engineering, while synthetic polymers present low bioactivity and higher mechanical properties [37]. Thus, the combination both types of materials is expected to yield a synergetic effect between natural and synthetic polymers [37], and has been proposed as a good compromise between biological and mechanical performance for tendon and ligament regeneration [83,104].…”

“…Electrospun bundles containing PLLA and collagen type I in different percentages, PLLA/Col-75/25 and PLLA/Col-50/50, were tested by Sensini et al [104] to evaluate its potential for human Achille tendon regeneration. Human tenocytes were cultured over the same time range on the bundles and cell morphology was assessed.…”

Advances in Tendon and Ligament Tissue Engineering: Materials Perspective

“…Furthermore, mechanical dynamic stimulation of the cell-seeded constructs could significantly promote tendon regeneration compared to static culture conditions. Sensini A. et al have investigated an electrospun bundled scaffold containing PLA and collagen type I [51]. This scaffold had sufficient mechanical properties with blends containing PLA/collagen 75:25 reaching a Young's modulus of 98.6±12.4 MPa as spun bundles and 205.1±73.0 MPa after 14 days of immersion in PBS.…”