Robust formulation for the design of tissue engineering scaffolds: A comprehensive study on structural anisotropy, viscoelasticity and degradation of 3D scaffolds fabricated with customized desktop robot based rapid prototyping (DRBRP) system.

This study investigates the scaffolds' structural anisotropy (i.e. the effect of loading direction), viscoelasticity (i.e. the effect of cross head speed or strain rate), and the influence of simulated physiological environment (PBS solution at 37°C) on the mechanical properties. Besides, the in vitro degradation study has also been performed that evaluates the effect of variation in material and lay-down pattern on the scaffolds' degradation kinetics in terms of mass loss, and change in morphological and mechanical properties. Porous three dimensional (3D) scaffolds of polycarprolactone (PCL) and polycarprolactone-polyethylene glycol (PCL-PEG) were developed by laying down the microfilaments directionally layer-by-layer using an in-house built computer-controlled extrusion and deposition process, called desktop robot based rapid prototyping (DRBRP) system. The loading direction, strain rate and physiological environment directly influenced the mechanical properties of the scaffolds. In vitro degradation study demonstrated that both PCL and PCL-PEG scaffolds realized homogeneous hydrolytic degradation via surface erosion resulting in a consistent and predictable mass loss. The linear mass loss caused uniform and linear increase in porosity that accordingly led to the decrease in mechanical properties. The synthetic polymer had the potential to modulate hydrophilicity and/or degradability and consequently, the biomechanical properties of the scaffolds by varying the polymer constituents.

Effect of nanofillers on the physico-mechanical properties of load bearing bone implants.

Bones are nanocomposites consisting of a collagenous fibre network, embedded with calcium phosphates mainly hydroxyapatite (HA) nanocrystallites. As bones are subjected to continuous loading and unloading process every day, they often tend to become prone to fatigue and breakdown. Therefore, this review addresses the use of nanocomposites particularly polymers reinforced with nanoceramics that can be used as load bearing bone implants. Further, nanocomposite preparation and dispersion modification techniques have been highlighted along with thorough discussion on the influence that various nanofillers have on the physico-mechanical properties of nanocomposites in relation to that of natural bone properties. This review updates the nanocomposites that meet the physico-mechanical properties (strength and elasticity) as well as biocompatibility requirement of a load bearing bone implant and also attempts to highlight the gaps in the reported studies to address the fatigue and creep properties of the nanocomposites.

Extrusion based rapid prototyping technique: an advanced platform for tissue engineering scaffold fabrication.

Advances in scaffold design and fabrication technology have brought the tissue engineering field stepping into a new era. Conventional techniques used to develop scaffolds inherit limitations, such as lack of control over the pore morphology and architecture as well as reproducibility. Rapid prototyping (RP) technology, a layer-by-layer additive approach offers a unique opportunity to build complex 3D architectures overcoming those limitations that could ultimately be tailored to cater for patient-specific applications. Using RP methods, researchers have been able to customize scaffolds to mimic the biomechanical properties (in terms of structural integrity, strength, and microenvironment) of the organ or tissue to be repaired/replaced quite closely. This article provides intensive description on various extrusion based scaffold fabrication techniques and review their potential utility for TE applications. The extrusion-based technique extrudes the molten polymer as a thin filament through a nozzle onto a platform layer-by-layer and thus building 3D scaffold. The technique allows full control over pore architecture and dimension in the x- and y- planes. However, the pore height in z-direction is predetermined by the extruding nozzle diameter rather than the technique itself. This review attempts to assess the current state and future prospects of this technology.