(134f) Characterization Of Whey Protein Isolate Sol-Gels As Scaffolds For Bone Regeneration

Conventional alternatives used for bone replacement, such as metals, ceramics, and various polymers have all shown considerable shortcomings. The deficiencies are due, in part, to the inability of these materials to fulfill the nonstructural roles of bone, such as ion reserves and red and white blood cell production. To further complicate matters, metal implantation generally results in necrosis of the adjacent bones and ligaments. Furthermore, the metal does not allow for the regeneration of bone in the site of the implant. While ceramics overcome the biocompatibility issues of metals, ceramics do not degrade and show high fragility and, therefore, cannot be used for large implants. Polymers are being investigated to address many of these issues. The chemistry in their construction can be used to control their rate of degradation and cross-linking can be used to increase the compressive properties of the material. However, developing polymers that meet all the requirements for the scaffold material has proven difficult. With hopes to correct many of these deficiencies, we are investigating using whey protein as a scaffold material.

The proposed scaffold material is a sol-gel made by thermally treating a concentrated suspension of whey protein isolate in an aqueous calcium chloride solution. Two aspects of the potential scaffolds are characterized in this study. The first is the material strength and its dependence on the protein and calcium chloride content of the gel-forming suspension. The second is the affinity of preosteoblastic cells towards the gels, and its dependence on the same two variables. As osteointegration is a key factor for the success of a scaffold material, the compositional range of interest for future work is to be gathered from this study. The significance of the work presented is that the strength of the naïve material is comparable to that of bone, and that the affinity of cells to the scaffold is such that its presence encourages osteoconduction. Both characteristics make this a promising future implant material in bone-deficient patients.

First, compressive material testing was performed on gel samples comprising a range of protein concentrations and calcium chloride concentrations to determine the ultimate compressive strength and modulus of the material. In this way the composition of highest strength is found and the range of interest for further study is determined. On samples of this range, preosteoblastic mouse cell-line (MC3T3-E1 subclone 4), is cultured in α-MEM for various incubation periods. SEM micrographs of the fixed cells will be presented with an analysis of ?flatness,? or, degree to which the cells spread on the different samples. Along with these, viability and cell density results from flow cytometry will be presented, quantifying the growth kinetics of the cells on the proposed scaffold material.