Fluorescent quantum dot as model imaging probe for studying plant uptake, systemic mobility, localization in plant tissue and potential fate of ultra-small nanoparticles

摘要

Fluorescent quantum dots (Qdots) are widely used as biomarker in animal cell imaging and spectroscopy. In recent years, these Qdots have emerged in agricultural applications. Studies are primarily focused on nanotoxicity of ultra-small size water-soluble Qdots in plant systems. In this study, we have developed CdS:Mn/ZnS and ZnS:Mn/ZnS Qdots based model bio-imaging probes for studying plant uptake, distribution, localization and potential fate of ultra-small size (＜10 nm) nanoparticles. These Qdots were synthesized using water-in-oil (W/O) microemulsion system. Qdots were surface-coated with biocompatible/ biodegradable materials such as N-acetyl cysteine (NAC). Stability of the coating and the core were evaluated using fluorescence confocal, fluorescence lifetime and Raman studies. Preliminary studies with N-acetyl cysteine (NAC) coated ～3-5 nm size ZnS:Mn/ZnS and CdS:Mn/ZnS Qdots demonstrated that these particles were readily uptaken by the snow pea (Pisum sativum L., a model plant) vascular system. Fluorescence microscopy studies confirmed localization of NAC-Qdots in the intercellular regions. Germination and growth of the snow pea seeds were found to be strongly dependent on Qdot dosage and incubation time with Qdots. Cd containing Qdots exhibited heavy metal induced toxicity. Seed germination reached 100% within 48 hours of ZnS:Mn/ZnS NAC-Qdot exposure. Confocal, AFM and Raman imaging studies were conducted to localize Qdots in plant tissue. Based on our preliminary findings, it is suggested that NAC-Qdot could be potentially used as systemic bio-imaging probes for studying ultra-small size engineered nanoparticle uptake, mobility and fate in plant system.