Freeze-drying storage method based on pectin for gold nanoparticles

A cheap, reproducible, environmentally friendly, and biocompatible method for stabilizing and storing gold nanoparticles for prolonged time is presented. Adding a diluted pectin solution immediately after the synthesis of gold nanoparticles increases the stability of the aqueous nanoparticle dispersion, avoiding agglomeration and further precipitation, regardless of the initial size and shape of the nanoparticles. When the gold nanoparticles–pectin solution is freeze-dried, a sponge-like solid is obtained, improving significantly the pectin capacity to stabilize gold nanoparticles. Because the gold nanoparticles are immobilized into the freeze-dried pectin matrix, the size, size distribution, and shape remain unchanged, regardless of how long the solid is stored. The solid can be redispersed in water to obtain a solution that is able to maintain the stability of the gold nanoparticles, even for more than 20 weeks. This solution can be freeze-dried again, with no changes in the gold nanoparticles size. The proposed method is an alternative for stabilizing nanoparticles with no toxic agents, increasing significantly the storage time.