Fig. 3

Absorption of nanoparticles. (a) Fluorescence microscopy images of Caco-2 cells after incubation with 20 µM curcumin at 37 °C for 4 h. The images demonstrate the intracellular uptake and localization of curcumin loaded PLGA, highlighting its potential for cellular permeation and retention. Curcumin’s fluorescence properties allow for visualization within the cells, indicating its successful internalization. (b) Calibration curve of curcumin with concentrations ranging from 0.391 to 25 µg/ml. The curve is used to determine the relative amount of curcumin absorbed by the cells, based on UV–vis absorbance intensity measurements. The strong linear correlation between curcumin concentration and absorbance intensity confirms the assay’s sensitivity and accuracy for quantifying intracellular curcumin levels. CN and CPN denotes curcumin nanoparticles, and curcumin piperine nanoparticles, respectively.