Introduction: Tubular shaped scaffolds can possess advantageous features over solid foam type scaffolds such as guiding or encouraging cells along a specific route or to a target location. Orientation of aligned fibrous structures and incorporation of media-activated shape recovery within the scaffolds which retain their initial structure throughout the period of implantation could be considered a promising strategy for defect filling and/or nerve guide applications. In addition, the scaffolds could also be used to guide tissues for regrowth along specific alignments[1].
Experimental Methods: In this study PLA fibres were manufactured using a melt-drawn process and collected on a rotating drum with traverse mode in order to maintain the unidirectional alignment of the fibres. Various mixtures of polyvinyl acetate (PVAc) and tricalcium phosphate (β-TCP) with the ratios of 100/0, 85/15 and 70/30 were used to manufacture tubular structures, where PVAc acted as a binder and the β-TCP was added to improve the biocompatibility of the scaffolds.
Results and Discussion: The cross-sectional morphology of the tubular scaffolds confirmed alignment of the fibres along with a significant number of voids in between the PLA fibre layers.
Incorporation of β-TCP particles increased the compressive modulus properties from 66 MPa to 83 MPa. However, a decrease in the compressive strength from 67 MPa to 41 MPa with addition of 30 wt% β-TCP in the scaffolds was also observed. This was suggested to be due to the increasing number of voids created within the scaffolds.
The wet scaffolds showed a mass gain of 45% after immersion in phosphate buffer saline (PBS)media for 24h and revealed shape-recovery properties for the wet scaffolds post compression testing (presented in Fig. 1).
Fig. 1: Shape recovery behavior of the tubular scaffolds: a) during compression b) compressed sample after 30 s and c) after 5 min of compression testing.
It was also seen that orientation of the PLA fibres and addition of β-TCP supported MG-63 human osteosarcoma cell attachment and spreading along the longitudinal direction of the fibres compared to the non- β-TCP content scaffolds (as presented in Fig. 2).
Fig. 2: Influence of PVAc/β-TCP coating materials and fibrous structure on cultured MG-63 osteosarcoma cells morphology and spreading on PLA 30% β-TCP scaffold at varying time points: a) 24h and b) 48h.
Conclusions: The scaffold device could be utilised for cell guide and cancellous bone repair applications where maintaining specific alignment was required. The advantage of using β-TCP was to enhance the biocompatibility of the construct and it also had the additional benefit of being resorbable.
The authors would like to thank Mrs Julie Thompson (Technician, University of Nottingham) for her kind help with the micro-CT analysis.
References:
[1] Hossain et al. (2015), Journal of Functional Biomaterials, vol. 6, p. 564.