The Carbon Dots from Seabuckthorn (Hippophae rhamnoides L.) Leaves: Recycle the Herbal Waste Products for a Nano-Formulation in Delivering Bioactive Compounds

Carbon dots have emerged as promising nanocarriers for drug delivery due to their unique physicochemical properties and biocompatibilities. Here, the potential of leaf-derived carbon dots (named as SBL_CD), derived from Seabuckthorn (<i>Hippophae rhamnoides</i> L.), was illustrated as a novel nano-formulation for bioactive compound delivery. Seabuckthorn leaves, rich in flavonoids, are the waste product during the production of Seabuckthorn fruits. The wasted leaves were utilized to synthesize carbon dots via a hydrothermal method. The resulting SBL_CD, characterized by TEM, FT-IR and Raman spectroscopy, exhibited a diameter of ~5 nm in both amorphous and quasi-crystalline forms. Applications of SBL_CD in cultures demonstrated robust properties of anti-inflammation and inducing neuronal cell differentiation. Furthermore, SBL_CD was able to encapsulate luteolin, a bioactive flavonoid. The enhanced delivery efficiency translated to superior biological activity, with SBL_CD-luteolin requiring only 1.50 μg/mL in achieving the EC₅₀ efficacy, as compared to 6.82 μg/mL for free luteolin in pNF200-Luc expression assays. This approach not only valorizes Seabuckthorn leaf by-products but also potentially improves the efficacy of encapsulated flavonoids. The development of SBL_CD as a multifunctional platform for flavonoid delivery represents a promising strategy in enhancing the efficacy of neuroactive compounds, combining anti-inflammatory effects (>70% cytokine suppression) with enhanced cellular uptake (4.5-fold increase).