Tracing multi-isotopically labelled CdSe/ZnS quantum dots in biological media

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Environmental Science

Background:

• Engineered nanoparticles (ENPs) require sensitive detection methods in biological media.
• Isotopically labelled ENPs offer enhanced detection capabilities.
• Understanding ENP behavior in complex biological matrices is crucial.

Purpose of the Study:

• To assess the strengths and limits of isotopically labelled engineered nanoparticles (spiked ENPs) in biological media.
• To determine the limit of quantification (LOQ) for spiked CdSe/ZnS quantum dots (QDs) in various matrices.
• To introduce a new metric (QD-RLOQ) for evaluating spiking method efficiency.

Main Methods:

• Synthesis of multi-spiked CdSe/ZnS quantum dots (QDs) enriched with 68Zn, 77Se, and 111Cd.
• Dispersion of QDs at low concentrations (0.1–5000 ppt) in biological matrices (saliva, urine, plasma, DPBS).
• Quantification of isotopic compositions using high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS).

Main Results:

• QD-LOQ values for Zn, Cd, and Se from QDs were 10, 0.3, and 6 ppt, respectively, below conventional HR-ICP-MS LOQ.
• In complex matrices, QD-LOQ values increased significantly (Cd: 16–32 ppt, Zn: 446–10598 ppt, Se: 1618–8317 ppt).
• QD-LOQs are influenced by matrix background concentration and dilution factors.

Conclusions:

• Isotopic labelling is advantageous for detecting ENPs at very low concentrations.
• Matrix effects significantly impact the limit of quantification for spiked ENPs.
• The novel QD-RLOQ metric provides a better assessment of spiking method efficiency in biological media.