Biofabricated soft network composites for cartilage tissue engineering

Abstract

Articular cartilage from a material science point of view is a soft network composite that plays a critical role in load-bearing joints during dynamic loading. Its composite structure, consisting of a collagen fiber network and a hydrated proteoglycan matrix, gives rise to the complex mechanical properties of the tissue including viscoelasticity and stress relaxation. Melt electrospinning writing allows the design and fabrication of medical grade polycaprolactone (mPCL) fibrous networks for the reinforcement of soft hydrogel matrices for cartilage tissue engineering. However, these fiber-reinforced constructs underperformed under dynamic and prolonged loading conditions, suggesting that more targeted design approaches and material selection are required to fully exploit the potential of fibers as reinforcing agents for cartilage tissue engineering. In the present study, we emulated the proteoglycan matrix of articular cartilage by using highly negatively charged star-shaped poly(ethylene glycol)/heparin hydrogel (sPEG/Hep) as the soft matrix. These soft hydrogels combined with mPCL melt electrospun fibrous networks exhibited mechanical anisotropy, nonlinearity, viscoelasticity and morphology analogous to those of their native counterpart, and provided a suitable microenvironment for in vitro human chondrocyte culture and neocartilage formation. In addition, a numerical model using the p-version of the finite element method (p-FEM) was developed in order to gain further insights into the deformation mechanisms of the constructs in silico, as well as to predict compressive moduli. To our knowledge, this is the first study presenting cartilage tissue-engineered constructs that capture the overall transient, equilibrium and dynamic biomechanical properties of human articular cartilage.

Multiscale modelling and homogenisation of fibre-reinforced hydrogels for tissue engineering

“…The model solution shown in Figure 4(b) is for =0.525%, E f = 45. 4 MPa and ν f = 0.49; these parameters were obtained through a sparse parameter sweep, as described earlier.…”

“…Another recent study focused on the mechanical characterisation of fibrereinforced hydrogel scaffolds, measuring the properties of both the overall scaffold and individual PCL fibres; this is of great interest since knowledge of both is required to parameterise the homogenised model of this paper. While finite element modelling of fibrereinforced hydrogel scaffolds has previously been used to predict their overall mechanical properties [4], the homogenisation approach adopted here is more computationally efficient since it obviates the need to model each individual, repeating cell of the printed fibre lattice and the hydrogel contained within.…”

Biologically Inspired Scaffolds for Heart Valve Tissue Engineering via Melt Electrowriting

“…Melt electrowriting (MEW) is an emerging manufacturing technique that enables the fabrication of solvent‐free, highly organized fibrous scaffolds with micrometric features by merging principles of electrospinning and additive manufacturing . Therefore, it has the potential to overcome the limitations of the currently employed fabrication techniques by a predefined and preprogrammed fiber deposition .…”

Type II Photoinitiator and Tuneable Poly(Ethylene Glycol)-Based Materials Library for Visible Light Photolithography

“…The library exhibits a wide range of compressive moduli from 3.57 KPa to 6.4 MPa, which could mimic a wide range of tissues from soft tissue such as brain and adipose tissue to stiffer cancellous bone. 18,22,23 As shown in Figures 6 and 7, the compressive moduli (E) of the hydrogels increased with PEG-DA concentration. Through a combination of prolation and subsequent molecular relaxation by removal of the porogen, decreasing material stiffness was achieved.…”