A new process for rapidly synthesizing dense biomineralised collagen scaffolds

Abstract

With an ageing world population and over 20% of adults in Europe affected by bone disorders, there is urgency in developing advanced strategies and tissue regenerative biomaterials which provide an adequate microenvironment for cells to thrive. This project sought to develop a new material or method which furthered progress towards synthesizing bone. Bone is comprised primarily of collagen and hydroxyapatite (HA) mineral; while numerous methods exist for mineralising and densifying collagen respectively, bone-like organization does not yet coincide with scalability. This work combines previously disparate techniques to explore rapid fabrication of nascent bone. A collagen-HA coprecipitation protocol which utilizes plastic compression to form dense biomineralised scaffolds with time-related tuning of mineral characteristics was developed. Samples nucleated intrafibrillar crystals (<0.5hrs) and precipitated extrafibrillar ‘nanoflowers’ (<6hrs) whilst achieving cancellous bone-like density; composed of type-I collagen and 10xSBF, they were deemed non-cytotoxic to mesenchymal stem cells. This process was informed by physicochemical characterisations of hydroxyapatite discs mineralised using Simulated-Body-Fluids (SBFs), in which the biomimetic efficacy of accelerated precipitation pathways was assessed. Precipitation using 10xSBF was qualified as ubiquitously advantageous compared to standard varieties, generating minerals with carbonate substitutions and greater crystallinity in <1% of the time. A thermodynamic/kinetic profile of HA was also generated using state-of-the-art simulation techniques combined with dedicated dissolution experiments. This model presents an alternative dissolution mechanism for HA and addresses highlighted shortcomings on current theories, with a vision towards guiding scaffold production. In conclusion this work presents a production method for potentially viable bone repair substrates/void-fillers, with rapid synthesis and homogeneous, biomimetic structure. The in silico model makes inroads towards predicting HA precipitation dynamics which could be directly utilized in protocol optimization. Such progress would make an in vitro bone tissue model feasible, permitting the study of bone development beyond what is possible in-situ