title: Effects of phosphate-buffered saline concentration and incubation time on the mechanical and structural properties of electrochemically aligned collagen threads.
abstract: A key step during the synthesis of collagen constructs is the incubation of monomeric collagen in phosphate buffer saline (PBS) to promote fibrillogenesis in the collagen network. Optimal PBS-treatment conditions for monomeric collagen solutions to induce gelation are well established in the literature. Recently, a report in the literature (Cheng et al 2008 Biomaterials 29 3278-88) showed a novel method to fabricate highly oriented electrochemically aligned collagen (ELAC) threads which have orders of magnitude greater packing density than collagen gels. The optimal PBS-treatment conditions for induction of D-banding pattern in such a dense and anisotropic collagen network are unknown. This study aimed to optimize PBS treatment of ELAC threads by investigating the effect of phosphate ion concentration (0.5×, 1×, 5× and 10×) and incubation time (3, 12 and 96 h) on the mechanical strength and ultrastructural organization by monotonic mechanical testing, small angle x-ray scattering and transmission electron microscopy (TEM). ELAC threads incubated in water (no PBS) served as the control. ELAC threads incubated in 1× PBS showed significantly higher extensibility compared to those in 0.5× or 10× PBS along with the presence of D-banded patterns with a periodicity of 63.83 nm. Incubation of ELAC threads in 1× PBS for 96 h resulted in significantly higher ultimate stress compared to 3 or 12 h. However, these threads lacked the D-banding pattern. TEM observations showed no significant differences in the microfibril diameter distribution of ELAC threads treated with or without PBS. This indicates that microfibrils lacked D-banding following electrochemical alignment and the subsequent PBS-treatment-induced D-banding by reorganization within microfibrils. It was concluded that incubation of aligned collagen in 1× PBS for 12 h results in mechanically competent, D-banded ELAC threads which can be used for the regeneration of load bearing tissues such as tendons and ligaments.
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-2032, USA.
authors.forename: Jorge Alfredo
authors.initials: JA
authors.lastname: Uquillas
authors.forename: Vipuil
authors.initials: V
authors.lastname: Kishore
authors.forename: Ozan
authors.initials: O
authors.lastname: Akkus
mesh_terms: D016880:Anisotropy; D001672:Biocompatible Materials / Q000737:chemistry; D002021:Buffers; D003094:Collagen / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D006801:Humans; D008422:Materials Testing; D046529:Microscopy, Electron, Transmission / Q000379:methods; D010710:Phosphates / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011312:Pressure; D013314:Stress, Mechanical; D013710:Tendons / Q000473:pathology*; D013997:Time Factors; D023822:Tissue Engineering / Q000379:methods
chemical_list: D001672:Biocompatible Materials; D002021:Buffers; D010710:Phosphates; D011108:Polymers; D003094:Collagen