Data Sheet 1_Microalgae-mediated green synthesis of silver nanoparticles: a sustainable approach using extracellular polymeric substances from Graesiella emersonii KNUA204.docx

Traditional nanoparticle synthesis relies on chemical and physical methods that often involve hazardous reagents, high energy consumption, and environmental toxicity. As a sustainable alternative, biological synthesis utilizes biomolecules in an eco-friendly manner to form nanoparticles. This study explores the green synthesis of silver nanoparticles (AgNPs) using extracellular polymeric substances (EPS) secreted by the microalga Graesiella emersonii KNUA204, highlighting the potential of microalgal biomolecules in nanotechnology. EPS-rich supernatant from G. emersonii enabled AgNP formation under light without the need for biomass pre-processing. The effects of culture age, pH (optimal at 10–11), and tetracycline as a secondary stabilizer were examined. Tetracycline accelerated AgNP formation in dark conditions but could not fully substitute light-induced reduction. The synthesized AgNPs and tetracycline-assisted AgNPs (Tetra-AgNPs) were characterized using UV-visible spectroscopy, EDX, XRD, FTIR, TEM, and Zeta potential measurements, confirming their crystalline, spherical, and moderately stable properties. Biological assays showed strong antibacterial activity at 10 μg mL−1, though Tetra-AgNPs did not outperform AgNPs or tetracycline alone, suggesting structural incorporation of tetracycline. Both AgNPs and Tetra-AgNPs showed similar antioxidant activity. These findings support the potential of G. emersonii KNUA204 for dual biomass utilization, integrating biofuel production with nanomaterial synthesis. Further optimization of EPS composition and biosynthesis conditions could enhance nanoparticle properties for biomedical and environmental applications, reinforcing microalgae as a platform for sustainable nanotechnology.

传统纳米颗粒合成多依赖化学与物理方法，此类方法通常涉及有害试剂、高能耗以及环境毒性问题。作为可持续替代方案，生物合成法以生态友好的路径利用生物分子来制备纳米颗粒。本研究探索了利用埃默森格林藻（Graesiella emersonii）KNUA204分泌的胞外聚合物（extracellular polymeric substances, EPS）绿色合成银纳米颗粒（silver nanoparticles, AgNPs）的方法，凸显了微藻生物分子在纳米技术中的应用潜力。埃默森格林藻的富含EPS的上清液可在光照条件下实现银纳米颗粒的合成，无需对生物质进行预处理。研究考察了培养龄、pH值（最适范围为10~11）以及作为次级稳定剂的四环素对合成过程的影响。四环素可在黑暗条件下加速银纳米颗粒的形成，但无法完全替代光诱导的还原反应。研究人员采用紫外-可见分光光度法、能量色散X射线光谱（EDX）、X射线衍射（XRD）、傅里叶变换红外光谱（FTIR）、透射电子显微镜（TEM）以及Zeta电位测量，对合成的银纳米颗粒（AgNPs）与四环素辅助合成的银纳米颗粒（Tetra-AgNPs）进行了表征，证实二者均为结晶态、球形且具备中等稳定性的纳米颗粒。生物学活性实验表明，二者在浓度为10 μg·mL⁻¹时均表现出较强的抗菌活性，但四环素辅助银纳米颗粒并未优于单独使用的银纳米颗粒或四环素，这提示四环素已被整合进入纳米颗粒的结构之中。银纳米颗粒与四环素辅助银纳米颗粒的抗氧化活性相近。上述研究结果证实，埃默森格林藻KNUA204具备双重生物质利用潜力，可将生物燃料生产与纳米材料合成相结合。通过进一步优化EPS组成与生物合成条件，可提升纳米颗粒的性能以适配生物医学与环境应用需求，进一步确立微藻作为可持续纳米技术平台的价值。