Microfluidic approach to create three-dimensional tissue models for biofilm-related infection of orthopaedic implants.

With conventional in vitro culture methods, it is difficult to study complex interactions of host cells with pathogens and drugs in physiologically relevant microenvironments. To simulate orthopaedic implant-associated infection, a multi-channel microfluidic device was used to (1) observe in real-time the development of osteoblasts into three-dimensional (3D) tissue-like structures and (2) study how this development was influenced by phenotypes of Staphylococcus epidermidis. In the absence of bacteria, osteoblasts formed a confluent layer on the bottom channel surface, gradually migrated to the side and top surfaces, and formed calcified 3D nodular structures in 8 days. The delivery timing and concentration of an antibiotic were controlled to produce small colony variants, sessile biofilms, or dead cells of S. epidermidis. In the presence of the small colony variants, osteoblasts initially adhered, and spread, but were killed within 2 days. In contrast, the sessile biofilms and dead bacteria cells did not significantly interfere with the formation of tissue-like structures. The results suggest the possibility of creating in vitro tissue-biofilm-biomaterial interfaces and therefore 3D tissue models, as an entirely new method of studying biofilm-related infection of orthopaedic implants with physiological relevance.