Enhanced photostability of chlorophyll-a using gold nanoparticles as an efficient photoprotector

Improving the photostability of chlorophylls is one of the main challenges to facilitate their industrial and biotechnological use. In this regard, we have employed gold nanoparticles (AuNPs) to photoprotect chlorophyll-a (Chla). The results show that the photodegradation of Chla is slowed down in the presence of AuNPs, and an increase of as much as an order of magnitude in half-life time of Chla in the presence of AuNPs has been observed. It is further seen that under in vitro conditions, AuNPs are much better photoprotective agents of Chla than beta-carotene or quinones, which are known to be very effective under natural living conditions (plants). The protecting ability of Chla by AuNPs is the result of their efficient binding with Chla at its nitrogen sites even in the dark, thus inhibiting the reaction of reactive oxygen species with Chla, known to cause its degradation during illumination. The same property of AuNPs, i.e., to bind with Chla in the dark, renders them to be a better photoprotectant than carotene or quinones since these agents offer protection to Chla during its illumination.