Functionalised polycaprolactone films and 3D scaffolds via gamma irradiation-induced grafting

Abstract

Polycaprolactone (PCL) is frequently used as the base polymer in scaffolds targeted for tissue engineering applications. However, in the absence of further surface modification, the lack of functional moieties on the PCL chain results in non-ideal surface properties of such scaffolds, especially in terms of the inability to tailor the presentation of functional ligands for directed cell adhesion and growth. The current study investigates gamma irradiation-induced grafting as a means of improving the biofunctionality of the PCL surface. The surface presentation of carboxylic acid groups on 2D PCL films could be tailored by changing the acrylic acid (AAc) concentration and/or the solvent during grafting, as evaluated from X-ray photoelectron spectroscopy (XPS). From data obtained using Raman spectroscopy, it was concluded that the penetration depth of the grafted pAAc was affected by the solvent system with a mixed watermethanol system yielding high penetration. Grafted samples displayed a decreased elastic modulus of the surface correlating with pAAc penetration depth, as shown by nano-indentation using atomic force microscopy (AFM). The most promising grafting conditions found for the 2D PCL films were then applied to 3D thermally induced phase separation (TIPS) scaffolds and it was demonstrated using XPS that equivalent levels of grafting of pAAc could be achieved throughout the whole depth of the scaffold. The scaffolds maintained their overall integrity after grafting, even though we observed a decrease in the compressive modulus by 20% after surface modification. These combined studies confirm the utility of this surface modification methodology for scaffolds targeted at tissue engineering and cell culture applications.

Use of Two-Step Grafting to Fabricate Dual-Functional Films and Site-Specific Functionalized Scaffolds

“…The graft yield for the PCL SC -g-AA film displayed in Table 1 is essentially zero as observed previously when grafting of AA to PCL under similar conditions. 7 The chemical structure of the base polymer, PCL SC , contains both carbon (C 1s peak at 285 eV) and oxygen (O 1s peak at 532 eV) which is evident in all samples along with low (< 2%) levels of silicone contamination (identified through the binding energy of the silicon 2p peak at 101.8 eV). 26 The XPS data for the PCL SC -g-AA film that had been derivatized with PFP is displayed in Table 1 and shows the introduction of both fluorine (F 1s peak at 292 eV) and nitrogen (N 1s peak at 399 eV).…”

“…6 In our previous work, it was shown that surface modification throughout three-dimensional (3D) polycaprolactone (PCL) scaffolds (pore sizes of 60−100 μm) could be achieved by graft copolymerization of acrylic acid (AA) using a mixed solvent system, while a methanol solution resulted in surface-confined grafting. 7 In that study, no correlation between wettability and penetration was observed. 7 In addition to introducing site-specific chemistries in porous substrates, there has also been interest in fabricating bifunctional films 8,9 which have shown promise in biomedical applications.…”

“…7 In that study, no correlation between wettability and penetration was observed. 7 In addition to introducing site-specific chemistries in porous substrates, there has also been interest in fabricating bifunctional films 8,9 which have shown promise in biomedical applications. 8 Such films can be produced by plasma-polymerization (so-called bipolar films), 8,9 by grafting of binary monomer mixtures by preirradiation or simultaneous irradiation methods, 10−13 or by grafting of two monomers by a twostep method.…”

CHAPTER 11. Grafting of Functional Monomers on Biomaterials

“…Higher degree of grafting with increase in concentration generally observed 8,11,12,14,15 and can be rationalised based on radical polymerisation kinetics, i.e. the monomer concentration affects the chain length.…”

Screening bioactive compounds from Ligusticum chuanxiong by high density immobilized human umbilical vein endothelial cells

“…Successful preparation of these supports ascribes to the signaling domains in the molecules, which can specifically bind to integrin on cell membranes [33]. Various methods consisting of covalent bonding, layer-by-layer self-assembly, plasma treatment, photo-initiated grafting, and γ-irradiationinduced grafting have been utilized to immobilize the biomolecules onto the solid matrix [34,35]. These strategies have several limitations, including low grafting density because of steric hindrance, uncontrollable grafting yield of polymer brushes, and undesired reactions between reactive groups of the brushes and the surface [36].…”