The plateau-like release observed during the extended laundering was attributed to the immobilization of the internal nanoparticles formed within the fiber. It was deduced from the slope change in the plot of the silver concentration in cotton as a function of the laundering cycle that about 92 and 87% of the internal nanoparticles remained in cotton after 50 simulated home laundering cycles in water and a detergent solution, respectively. Considering that most textile manufacturing processes involve washing, the final products that the consumer will experience in household use would have mainlyinternal nanoparticles. The washing durability of the internal nanoparticles was demonstrated by the retention of superior antimicrobial activity of cotton, i.e., greater than 99.99% reductions of P. aeruginosa and S. aureus, after 50 home laundering cycles.