Effect of Pore Size and Void Fraction on Cellular Adhesion, Proliferation, and Matrix Deposition

Abstract

The aim of this study was to determine the influence of two key scaffold design parameters, void fraction (VF) and pore size, on the attachment, growth, and extracellular matrix deposition by several cell types. Disc-shaped, porous, poly(-lactic acid) (L-PLA) scaffolds were manufactured by the TheriForm solid free-form fabrication process to generate scaffolds with two VF (75% and 90%) and four pore size distributions (< 38, 38-63, 63-106, and 106-150 microm). Microcomputed tomography analysis revealed that the average pore size was generally larger than the NaCl used, while VF was at or near the designated percentage. The response of three cell types-canine dermal fibroblasts (DmFb), vascular smooth muscle cells (VSMC), or microvascular epithelial cells (MVEC)-to variations in architecture during a 4-week culture period were assessed using histology, metabolic activity, and extracellular matrix deposition as comparative metrics. DmFb, VSMC, and MVEC showed uniform seeding on scaffolds with 90% VF for each pore size, in contrast to the corresponding 75% VF scaffolds. DmFb showed the least selectivity for pore sizes. VSMC displayed equivalent cell proliferation and matrix deposition for the three largest pore sizes. MVEC formed disconnected webs of tissue with sparse extracellular matrix at 90% VF and >38 to 150 microm; however, when cultured on scaffolds with pores formed with salt particles of <38 microm, MVEC formed a multilayered lining on the scaffolds surface. Culture data from scaffolds with a 75% VF suggests that the structural features were unsuitable for tissue formation. Hence, there were limits of acceptable scaffold architecture (VF, pore size) that modulated in vitro cellular responses.

3D Bioprinting Using a Templated Porous Bioink

“…Porosity is a critical feature in tissue engineering structures, with large pores shown to increase elastic moduli, enhance nutrient mass transport, and provide interstitial space for extracellular matrix (ECM) deposition. [ 24,25 ] Moreover, unidirectional calcium diffusion into the hybrid gel generated aligned channels oriented perpendicular to the gel surface (Figure 2 d). This behavior has previously been observed in alginate hybrid gels, [ 26,27 ] and is thought to occur when hydrodynamic fl ow arises from friction between the contracting alginate chains and the bulk solution.…”

Cell colonization in degradable 3D porous matrices

“…These studies 8,9 have shown that besides chemical cues, 3D matrix physical properties such as stiffness, 81 hydrophilicity, porosity, 29 pore size and void fraction 82,83 can affect cell morphology, attachment and function (Fig. 2).…”

“…Especially the spatial structures or the topography of scaffolds influence cell alignment, orientation, 84 multicellular organization, 82 cell spreading 85 and cell attachment. 83 2D surface features such as edges, grooves, steps, roughness and pores of substratum significantly influence cell behavior. 84,86 Important structural properties include both the mechanical properties inherent in the material, such as break stress, modulus of elasticity and stiffness, but also the properties of the scaffold's 3D architecture.…”

The effect of pore size on cell adhesion in collagen-GAG scaffolds

“…In porous silicon nitride scaffolds, endothelial cells bind only to pores smaller than 80 µm while fibroblasts preferentially bind to larger pores (>90 µm). In PLLA scaffolds, vascular smooth muscle cells preferentially bind to one range of pore sizes (63 -150 µm) while fibroblasts bind to a wider range (38 -150 µm) [12,13]. A number of cell types exhibit preferences to binding in scaffolds with pore sizes considerably larger than the characteristic cell size, often utilizing a characteristic bridging mechanism where adjacent cells act as support structures to assist bridging large pores; examples include fibrovascular tissue ingrowth into PLLA scaffolds, osteoblast adhesion to polylactide-co-glycolide (PLAGA) scaffolds, and rat marrow cells binding to PEOT/PBT scaffolds [7,14,15].…”