"The search for new or alternative materials for use in bone tissue engineering (BTE) is one of the main challenges. Whey protein isolate (WPI) as a by-product of cheese manufacturing is inexpensive and widely available. Heat treatment of an aqueous solution of WPI above 60 °C results in the formation of a three-dimensional hydrogel network without the use of additional chemical cross-linking agents. A group of widely studied biomaterials for BTE includes bioactive glasses (BGs). Attractiveness of BGs lies in their ability to bond to living bone (bioactivity). Furthermore, their ionic dissolution products have been shown to stimulate bone formation via activating osteogenic genes (osteoinductivity). BGs can be used as effective carriers for inorganic therapeutic ions. Copper (Cu) and cobalt (Co) ions are known to induce new blood-vessel formation (angiogenesis). This has recently attracted particular attention because angiogenesis, besides osteogenesis, is essential for complete bone tissue regeneration.
In this work, for the first time, a material derived from food industry waste – WPI - and a material commonly used in bone regeneration – BGs - were combined to obtain novel composite biomaterials with potential applications in BTE. Additionally, to obtain pro-angiogenic properties, BGs doped with Cu2+ and Co2+ ions were used. Simple method based on the gas foaming (NH4HCO3) and autoclaving was applied to produce highly porous WPI/BG scaffolds. Materials were evaluated in terms of microstructure using SEM, high-resolution X-Ray microtomography and mercury intrusion porosimetry. In vitro bioactivity was evaluated by incubation of materials in simulated body fluid (SBF). The samples after incubation were analysed using ATR-FTIR and SEM/EDX methods. The changes in Ca, P, Si, Cu, and Co concentration in the SBF were monitored using an ICP-OES technique.
Using a simple gas foaming method, ready-to-use (sterile), bioactive scaffolds with high porosity (above 70%), fully connected pore networks, and pore size suitable for BTE applications (80–350 μm) were obtained. Thanks to the use of Cu2+ and Co2+-doped sol-gel BGs, the scaffolds showed additional functionalities - they are able to develop bioactive calcium phosphate layer on their surfaces and to gradually release therapeutic ions. Porous WPI/BG composites showed great potential for the use as novel bone substitutes, however they require further studies, especially analysis of degradation kinetics and biological properties.
This work was supported by the National Science Centre, Poland Grant No. 2019/32/C/ST5/00386 (MD)."