Synthesis of CQD-doped and bio-based chitosan-starch-locust bean gum composite polymeric films for cell growth and pH-responsive drug release

Recently, Carbon Quantum Dots (CQDs) have been heralded as economically and ecologically friendlier alternatives to their traditional counterparts. In this study, we aimed to investigate how carbon-source pretreatment and N-doping affect poppyseed-derived CQDs and whether these differences influence the drug delivery and cell growth properties of CQD-incorporated bio-based polymeric films. CQDs were synthesized hydrothermally from unaltered, ground, and oil-extracted poppyseeds, both with and without N-doping, and subsequently incorporated into Chitosan-Starch-Locust Bean Gum (LBG) blends crosslinked with citric acid and prepared by solvent casting. N-doping resulted in a 1.81-fold increase in emission intensity together with an approximately 46 nm blueshift, while oil extraction also increased the emission intensity of the obtained CQDs. The films were evaluated for swelling, Diclofenac Diethylamine loading and pH-responsive release, and L929 mouse fibroblast growth over 72 h. The highest drug loading capacity was approximately 78% for the control 12:2:1 Chitosan/LBG/Starch formulation, while CQD-containing films generally demonstrated lower but formulation-dependent loading capacities. Drug release was strongly dependent on pH, occurring from fastest to slowest at pH 7.4 (≈10–100 min), pH 2.3 (≈160–280 min), and pH 5.5 (≈24–30 h). Release kinetics likewise varied according to pH and formulation, indicating that the governing release mechanism was not uniform across the films. CQD-containing films also demonstrated increased L929 cell growth compared with the corresponding CQD-free sample, reaching an average 2.3-fold increase after 72 h. Overall, the CQD-integrated polymer films have favorable drug loading/release and cell growth properties, showing great potential for biomedical and tissue engineering applications.