Membranes were prepared from fibroin, a protein isolated from the domesticated silkworm (Bombyx mori) silk, and evaluated as a potential substratum for corneal limbal epithelial cells. These membranes (i.e., B. mori silk fibroin [BMSF] membranes) were cast from dialyzed solutions of fibroin protein (4% w/v) dispensed into 35-mm-diameter culture dishes and dried at room temperature (23–24°C). The resulting material was transparent, easy to handle, and supported levels of human limbal epithelial (HLE) cell growth comparable to that observed on tissue culture plastic. Remarkably, these results were obtained utilizing a commercial serum-free medium (CnT-20) designed for the ex vivo expansion of corneal epithelial progenitor cells. The potential benefits of serum proteins on this culture system were examined through addition of fetal bovine serum (FBS) either to fibroin stocks prior to membrane casting or by supplementation of the CnT-20 medium. Membranes cast in the presence of FBS displayed increasing opacity and induced little change in HLE growth. Supplementation of CnT-20 medium with FBS deterred cell growth on all substrata, including tissue culture plastic control substrata. The remarkable properties of BMSF membranes demonstrated under serum-free conditions warrant investigation of this material as a substratum in the creation of tissue-engineered constructs for the restoration of diseased or damaged ocular surface.

Advances in bioengineering and stem cell research betoken revolutionary changes in the practice of medicine, but while the science, ethics, and morality have been passionately debated, little attention has been given to managing risks inherent to production protocols, which are often complex and research based. Current investigational protocols rely on the use of animal and/or donor human tissue products and thus carry the potential to induce xenogenic microchimerism in recipients or disease transmission through contamination with bacteria, viruses, or other infectious agents, such as those responsible for transmissible spongiform encephalopathy (TSE).^1-5 Until specific guidance can be established for emerging cell-based therapies, potential manufacturers are being encouraged by regulators to adopt strategies that minimize risk to patient well-being. The financial costs of adopting these measures and varying degrees of legislative and regulatory oversight globally may drive future clinical trials to markets with fewer legislative and regulatory restrictions. This is disadvantageous to clinical investigators and may permit the emergence of significant risks to public health on a global scale. This current work examines features of current techniques that may infringe benefits to society.