Endotoxins affect bioactivity of chitosan derivatives in cultures of bone marrow-derived human mesenchymal stem cells.

Biomaterials research has been expanding over the last decade, in part to provide improved medical devices for the treatment of orthopedic tissue injuries. In the quest to provide the best performance combined with low cost for medical implants, an increasing number of non-chemists have entered the field of biomaterials research without the profound knowledge of chemistry needed to understand the complex interaction mechanisms and characteristics of natural substances. Likewise, non-biologists often lack understanding when it comes to the presence of the contaminating biota frequently found in natural substances. This lack of knowledge by researchers in the field, combined with sensitive in vitro cell-based assays, can lead to inaccurate evaluation of biomaterials. Hence, there should be both an active effort to assemble multi-disciplinary teams and a genuine concern for the possible effects of contamination on in vitro assays. Here, we show that the presence of bacterial endotoxins in chitosan derivatives can result in false-positive results, profoundly altering product performance in in vitro assays. False-positive results through uncritical use of natural substances in vitro can be avoided by proper endotoxin testing and careful evaluation of cytokine secretion patterns.