We report the details of our success in conferring photocatalytic self-cleaning properties on keratin fibers using modified sol-gel colloids. To the best of our knowledge, we studied for the first time the crucial effect of the concentration of titanium dioxide precursor on colloid composition, properties, and biocompatibility in an attempt to enhance the properties and application of anatase titanium dioxide colloid to keratins. The transparency, the particle size distribution, and the crystallinity of synthesized colloids were systematically investigated. The compatibility of the colloids and keratin substrates is thoroughly compared and discussed. The insights presented contribute to the further understanding of the structure-property-use relationship of titanium dioxide in biomaterial applications. © 2009 Elsevier Inc. All rights reserved.