Theranostic nanozyme: Silk fibroin based multifunctional nanocomposites to combat oxidative stress

Multifunctional nanomaterials integrating therapeutic and imaging modalities in one platform have opened a new era in the present therapeutic strategies. In the present study, a multifunctional silk fibroin-based carrier has been designed for the delivery of antioxidant and imaging agents. One-step desolvation method was used to prepare sulforaphane (antioxidant drug) loaded silk fibroin nanoparticles (SFSNPs). These anionic SFSNPs were further coupled with cationic cerium oxide nanoparticles (CeNPs) and PEI passivated carbon dots (CDs) to form self-assembled CeNP-CD@SFSNPs nanocomposites. CDs were synthesized from mulberry leaves (Morus indica) as green source of carbon and bPEI as a passivating agent to get positively charged CDs. The CDs functioned as molecular probes by emitting green fluorescence while the presence of CeNPs augmented the antioxidant potential due to their unique redox property. Time-dependent in vitro release of sulforaphane was fast in acidic pH than under normal physiological conditions. Cytotoxicity studies were performed on L132 normal epithelial lung cell lines and A549 lung cancer cell lines to analyze the toxicity of the nanocomposites. Green fluorescence from the CDs facilitated in fluorescence microscopic imaging and cellular uptake studies. ROS scavenging capability was analyzed by exposing cells to H₂O₂ stress using flow cytometry and DCFH-DA staining. Overall, the synthesized CeNP-CD@SFSNPs nanocomposites efficiently reduced ROS levels by simultaneously enabling imaging of the cells. Thus, this CeNP-CD@SFSNPs nanocomposite could be a potential candidate for simultaneous imaging and drug delivery against oxidative stress.