Knitted polylactide 96/4 L/D structures and scaffolds for tissue engineering: Shelf life, in vitro and in vivo studies

Abstract

This study covers the whole production cycle, from biodegradable polymer processing to an in vivo tissue engineered construct. Six different biodegradable polylactide 96/4 L/D single jersey knits were manufactured using either four or eight multifilament fiber batches. The properties of those were studied in vitro for 42 weeks and in 0- to 3-year shelf life studies. Three types (Ø 12, 15 and 19 mm) of cylindrical scaffolds were manufactured from the knit, and the properties of those were studied in vitro for 48 weeks. For the Ø 15 mm scaffold type, mechanical properties were also studied in a one-year in vivo experiment. The scaffolds were implanted in the rat subcutis. All the scaffolds were g-irradiated prior to the studies. In vitro, all the knits lost 99% of their mechanical strength in 30 weeks. In the three-year follow up of shelf life properties, there was no decrease in the mechanical properties due to the storage time and only a 12% decrease in molecular weight. The in vitro and in vivo scaffolds lost their mechanical properties after 1 week. In the case of the in vivo samples, the mechanical properties were restored again, stepwise, by the presence of growing/maturing tissue between weeks 3 and 12. Faster degradation was observed with in vitro scaffolds compared to in vivo scaffolds during the one-year follow up.

Fiber-based tissue engineering: Progress, challenges, and opportunities

“…This technique has been used to create fibers from various synthetic polymers such as polyethylene terephtalate (PET) (Lu et al, 2005, Sinclair et al, 2010), starch–PCL and starch–poly(lactic acid) (PLA) (Gomes et al, 2008), PLA (Chester and Bornemann, 2008, Ellä et al, 2011, Lu, Simionescu, 2005, Sumanasinghe et al, 2010), and poly(3-hydroxybutyrate) (Chester and Bornemann, 2008, Hinüber et al, 2010). Meltspinning process enables customized fiber constructions including monofilament (Sumanasinghe, Haslauer, 2010), multifilament (Ellä, Annala, 2011), and low denier per filament (DPF) (Sinclair, Webb, 2010) with the ability to create complex cross-sections. For example, fractal-like (Lu, Simionescu, 2005, Sinclair, Webb, 2010) or hollow fibers (Hinüber, Häussler, 2010) have been created to enable cell alignment and topographical control of cell orientation.…”

“…Fibers fabricated by meltspinning have relatively high mechanical properties with ultimate tensile strength of ~340 MPa and elastic modulus of 7.1 GPa (Chester and Bornemann, 2008). Therefore, meltspun fibers are suitable for textile based fabrication techniques such as knitting, weaving, or braiding (Ellä, Annala, 2011). …”

Bioabsorbable fabrics for musculoskeletal scaffolds

“…Starting around mid-1990s, we have worked on melt-spinning PLAs, with P(L/D)LA 96/4 being the most-spun raw material, preparing knits, weaves, braids, and nonwovens from single fibre types or several combined (e.g., T€ ormälä, 2003, Paakinaho et al, 2009;Ellä et al, 2011). Starting around mid-1990s, we have worked on melt-spinning PLAs, with P(L/D)LA 96/4 being the most-spun raw material, preparing knits, weaves, braids, and nonwovens from single fibre types or several combined (e.g., T€ ormälä, 2003, Paakinaho et al, 2009;Ellä et al, 2011).…”

“…The knits have also been applied to form round 3D-cylinder scaffolds, of which the basic form is the joint scaffold (Ellä et al, 2011), and researchers have employed differently modified composite scaffolds from the materials for lumbar fusion studies (Palmgren et al, 2003), in addition to testing them in calvarial bone with growth factors (Gómez et al, 2006) and with adipose stem cells and electrical stimulation for osteochondral defect repairs (Ahtiainen et al, 2012).…”

“…In 1994, in Finland, research inspired by the Vainio method (Vainio, 1989) led to the development of melt-spinning poly-L,D-lactide 96/4 into 4-filament yarns, followed by the design and manufacturing of scaffolds from these fibres, and then in vitro (Ellä et al, 2011), preclinical (Länsman et al, 2006Waris et al, 2008a,b), and clinical experiments (e.g. Honkanen et al, 2003;Honkanen et al, 2009) to confirm the functionality of the scaffolds (see Figure 4.2 for the image).…”