Quercetin-Loaded Nanocarriers as Effective Inhibitors for Copper Metal Ion-Induced γD-Crystallin Aggregation

Cataract is one of the leading causes of blindness worldwide. Till date, the only solution for cataracts is surgery, which is a resource-intensive solution. A much simpler solution is to find a potential drug that could inhibit aggregation. It is well established that nonamyloid aggregates of eye lens protein result in cataract. γD-Crystallin, a thermodynamically stable protein, is one of the most abundant proteins in the core of the eye lens and is found to aggregate under stress conditions, leading to the cataract. It has also been found that in cataractous lens, the concentration of metals like copper is elevated significantly as compared to healthy eye lens, suggesting their role in inducing aggregation. In our present study, aggregation of γD-Crystallin was carried out in the presence of Cu (II). Using techniques like turbidity assay, CD spectroscopy, ANS binding assay, and microscopic studies like TEM, it could be confirmed that protein aggregates in the presence of Cu (II) and the nature of aggregates is amorphous. Various polyphenols were tested to suppress aggregation of the protein. Quercetin was observed to be the most efficient. To overcome the problems associated with the delivery of polyphenols, such as solubility and bioavailability, quercetin was encapsulated in two types of nanocarriers. Their characterization was done using TEM, DLS, and other techniques. The potency of quercetin-loaded CS-TPP/CS-PLGA NPs as inhibitors of γD-Crystallin aggregation was confirmed by various experiments.