Characterisation of ‘wet’ polymer surfaces for tissue engineering applications: Are flat surfaces a suitable model for complex structures?

Abstract

Tissue engineering scaffolds are 3D constructs that simulate the growth environment in vivo. The present work aims to address the question of whether thin films, i.e., flat surfaces, are a suitable model for more complex 3D structures? With this in mind a complete study of the morphology and surface chemistry of poly(D,Llactide) (PDLLA) substrates, fabricated into two different structures, is presented. The polymer structures studied include a 3D, porous, foam-like scaffold prepared by the thermally induced phase separation (TIPS) method and flat polymer thin films made by solvent casting. Based on the maximum bubble point test, a new method to assess the wettability of wet pore wall surfaces inside highly porous 3D structures was developed and tested. The maximum pore diameter determined using the maximum bubble point test for the total wetting liquids was confirmed through image analysis of scanning electron micrographs. The method allows the determination of the contact angle between the wet pore wall and a contacting liquid. The captive bubble method was employed to characterise the wettability of flat polymer films in contact with water. Both structures were further characterised using zeta-(ζ-) potential measurements to assess the surface chemistry of the polymer. The results demonstrate that PDLLA contains acidic functional groups and is hydrophobic. In order to evaluate the sensitivity of the test methods, the polymer surfaces were modified by protein adsorption using fibronectin and collagen. ζ-Potential and wettability measurements show that proteins indeed adsorb on virgin PDLLA surfaces. Protein adsorption causes the wettability of the PDLLA for water to improve. Our results strongly indicate that flat surfaces are not a suitable model for surfaces in complex 3D structures such as highly porous tissue engineering scaffolds. Such scaffolds must be characterised as a 3D system.

Tailoring Cell Behavior on Polymers by the Incorporation of Titanium Doped Phosphate Glass Filler

“…This is observed for at least PLDL and the TCP/PLDL composite. PLDL has an iep of 4.0 and a z plateau of À30 mV, which corresponds well to z-potentials measured for PDLLA [46,45] which have similar iep and z plateau values. As expected the incorporation of inorganic fillers into the polymer matrix does effect the surface properties, i.e., the wettability and z-potential, of the polymer.…”

Synthesis of two-component injectable polyurethanes for bone tissue engineering

“…To determine the wettability of each hydrated polymer film, captive bubble contact angle techniques were performed as described elsewhere [31] using a Drop Shape Analyser (DSA 10 MK2, Kru¨ss GmbH, Hamburg, Germany). Films cured to glass microscope slides were placed horizontally into the measurement cell and filled with Dulbecco's-modified phosphate buffered solution (D-PBS).…”

The development of a three-dimensional scaffold for ex vivo biomimicry of human acute myeloid leukaemia

“…Scaffold properties, such as surface area, porosity and pore size, are critical in influencing cell adhesion, spreading, proliferation and differentiation [33]. Several scaffolds have been employed for the culture of stem cells, including the ones evaluated in this work: PLGA has been utilised to expand human chrondrocytes [34], PDLLA for the growth of osteoblasts, chrondrocytes, and lung carcinoma cells [35], PCL for the expansion of dermal fibroblasts [36], PS in tissue culture plastics [37], PMMA for bone remodelling [38], and PU for growth and proliferation of rabbit bone marrow stromal cells [39].…”