This invention is directed to preparations useful for the permanent or substantially permanent treatment of textiles and other webs. More particularly, the preparations of the invention comprise an agent or other payload surrounded by or contained within a polymeric encapsulator that is reactive to webs, to give textile-reactive nanoparticles. By "textile-reactive" is meant that the payload nanoparticle will form a chemical covalent bond with the fiber, yarn, fabric, textile, finished goods (including apparel), or other web or substrate to be treated. The polymeric encapsulator of the payload nanoparticle has a surface that includes functional groups for binding or attachment to the fibers of the textiles or other webs to be treated, to provide permanent attachment of the payload to the textiles. Alternatively, the surface of the nanoparticle includes functional groups that can bind to a linker molecule that will in turn bind or attach the nanoparticle to the fiber. This invention is further directed to the fibers, yarns, fabrics, other textiles, or finished goods treated with the textile-reactive nanoparticles. Such textiles and webs exhibit a greatly improved retention or durability of the payload agent and its activity, even after multiple washings.