Efficient biocompatible drug carrier: Lignin-based nanogel amplifies Curcumin's cytotoxic effects and induces apoptosis in brain and lung cancer cell lines

This study focuses on the biological effects of size-tunable nanogel based on the natural polymer named lignin. The flexibility of the nanogel to act under variable conditions makes it a promising smart carrier in nanomedicine. Through the “grafting from” approach, it was synthesized by atom transfer radical polymerization (ATRP) method, loaded with curcumin (an anticancer herbal compound) and has been applied to treat two cell lines (A549 and U87MG). Treatment of cells with free curcumin and curcumin-loaded nanogel demonstrated significant differences in IC50 values. The values of free curcumin were 48.23 μM for A549 cells and 36.54 μM for U87MG cells, while the values of curcumin-loaded nanogel were 25.95 μM for A549 cells and 25.65 μM for U87MG cells, respectively. This indicates that the nanogels enhanced the cytotoxic effects of curcumin on both cancerous cell lines.

Furthermore, the expression of apoptosis associated genes was evaluated. Under the effects of curcumin-loaded nanogel, the expression of caspase 3 and caspase 9 genes in the A549 cell line increased by 2.3-fold and 1.41-fold, respectively. Additionally, the expression of the pro-apoptotic gene Bax increased by 1.29-fold, while the anti-apoptotic gene Bcl2 decreased by 0.315-fold. Similarly, in U87MG cells, the expression of caspase 3 and caspase 9 genes increased by 6.49-fold and 2.08-fold, respectively, while Bcl2 decreased by 0.023-fold. The changes in gene expression patterns indicate the induction of apoptosis in both cell lines when exposed to curcumin-loaded nanogels. The results of flow cytometry confirmed an increase in apoptosis in the presence of curcumin-loaded nanogels.