Bulk Metallic Glasses (BMGs) are a newly emerged class of biomaterials that possess a unique combination of properties. BMGs thanks to their metallic component resemble metal-based biomaterials in their strength and stiffness, however as amorphous structures which components and internal organization can be easily altered they are also highly elastic (compressive elasticity), ductile, wear-resistant and generally do not cause a severe immune reaction. Moreover, they are easily modifiable both in terms of their macroscopic and microscopic structure (for example of surface molding patterns see figure below), which might positively influence their biocompatibility and biointegration by decreasing the formation of fibrous capsule around the BMG-implant.
While there are many types of BMGs, containing several metals, such as Zr, Cu, Fe, Ti, or V, among others, after reviewing some literature on the topic I found that most of now used BMG-based implants result in eventual isolation of the implant from host tissue by fibrous encapsulation (see figure on the left; examples: Mg60Zn35Ca5 in porcine abdomen, Zr60Ti6Cu19Fe5Al10 alloy in rabbit). However, the group of Kyriakides, research of which we learned about during the guest lecture, looks into how altering the surface of BMGs can improve their incorporation into the host tissue, that is result in lower inflammatory response and ultimately absence of fibrous encapsulation. The groups produced BMGs with different size nanopatterns on their surface by thermoplastic forming (to avoid the crystallization) and investigated the response of macrophages and fibroblasts to the nanopatterned BMGs as these are the main cell types involved in inflammatory response, and production of collagen I-rich matrix and encapsulation respectively, and result in loss of functionality of implant.
Interestingly, the nanopatterns on the surface of BMGs resulted in lower fused macrophage – giant cell response, as well as smaller size of fibroblasts on the highly nanoscale-patterned material. The smaller size of fibroblasts can be explained by decreasing adhesion of the cells when the pattern was smaller which was also observed in their study. What is more important, these fibroblasts also expressed less collagen I, which is a very promising result and indication for future projects involving production of highly biointegrative biomaterials.
Based on these results, nanopatterning of BMGs seems to facilitate alteration of cellular responses to implants and therefore in the future we may be able to find the optimal nanopattern to fully diminish fibrous encapsulation implants, allowing for the ideal situation where integration of the material into host tissue would occur.