Nanomaterials have unique properties due to their size, which makes nanomaterials widely use in industries, commodities, medical and other fields. The widespread use of nanomaterials inevitably leads to their release in the environment, which has caused people's eager attention to its environmental hazards, ecosystem impacts and health effects. The development of nanotechnology requires nanodosimetry to provide reliable and accurate analytical techniques to quantify and characterize nanomaterials. In recent decades, commercial instrumentation and standard methods have been developed to characterize nanomaterials. Single particle inductively coupled plasma-mass spectrometry (spICP-MS) is a promising method for determination of nanoparticles. It can directly detect nanoparticle and dissolved ion signals in solution without separation pretreatment, which can also accurately detect particle size, distribution, composition, mass concentration and number concentration in environmental concentration samples. Although spICP-MS shows great potential for the analysis of nanomaterials, there are still some challenges. The sample matrix interference and transmission efficiency are important factors influencing the sensitivity and application range of spICP-MS. In order to improve the transmission efficiency, reduce the matrix influence and expand the application range, this research improves the spICP-MS sample introduction system. The improved method increases the transmission efficiency, reduce the influence of matrix. The improved spICP-MS method was employed to detect the dynamic changes of nanoparticles in blood samples with time, which provided an analytical method for the application of nanomaterials in the field of medicine. Moreover, spICP-MS also was used to analyzed the distribution of AuNPs@SiO2 in mice. The AuNPs@SiO2 is similar to fine atmosphere particles. Its distribution in mice provides useful information for studying the toxicity of fine particulate matter in the atmosphere.
The research mainly includes the following four aspects:
1. Improvement of spICP-MS sample introduction
The sample introduction of spICP-MS directly affects the determination of nanomaterials, including the transfer of nanoparticles to the plasma, the gasification of the sample into an aerosol, and the proportion of sample entering the plasma. In order to improve the transmission efficiency and reduce the influence of sample matrix, this research uses microFAST automatic sample introduction system to replace peristaltic pump. The sample flow rate is 0.3 mL/min or 0.5 mL/min with peristaltic pump. While using the microFAST autosampler system, the sample flow rate can be adjusted from 0.005 mL/min to 5 mL/min, and the minimum injection volume can be as low as 20 μL. At the same time, the cyclonic spray chamber without baffle is used to replace the traditional two-channel spray chamber and the spray chamber with baffle, which can greatly improve the transmission efficiency. Generally, the transmission efficiency of the spray chamber with the baffle is about 30% when the sample flow rate less than 10 μL/min. However, the transmission efficiency of the baffle spray chamber without baffle can reach 92.9 % at the similar flow rate. At the same time, the improved sample introduction of this project also reduces the influence of the sample matrix on the detection, reduces the sample pretreatment process, and expands the sample analysis range of spICP-MS.
2. Detection of AuNPs with different shapes by spICP-MS
As a powerful nanoparticle analysis technology, spICP-MS reduces the complexity of sample preparation process, and also analyzes particle size, mass concentration, particle concentration and corresponding chemical composition to obtain multidimensional information. However, the current analysis of nanoparticles by spICP-MS is mainly based on the size and distribution of spherical nanoparticles, which is rarely reported for other shapes of nanoparticles. Nanomaterials such as nanowires and nanorods have been widely used in various fields such as medicine and industry because of their special properties. In order to evaluate the environmental behavior and toxic effects of non-spherical nanomaterials, it is necessary to study the characterization and quantitative analysis of different shapes of nanoparticles by spICP-MS method. In this project, the nano-gold spheres with different particle sizes and gold nanorods with different aspect ratios were synthesized firstly, and then UV-Vis and TEM methods were employed to characterize the shape and size. Finally, the concentration and size were characterized and quantified by spICP-MS, which provides useful information for the detection of nanoparticles with different shapes.
3. Dynamic changes in nanoparticles in blood samples detected by spICP-MS
spICP-MS is a new analytical method with high sensitivity, short analysis time and characterization of metal nanoparticles. It has been widely used in many fields such as environment, food and manufacturing. The dynamic changes of nanoparticles in the blood are essential for understanding their absorption and metabolism in the body. The concentration of nanoparticles in the blood changes over time to reveal whether the nanoparticles can cross the biological barrier and whether they will deposit into the organ. However, biological samples are generally small in size, low in concentration, and require biological enzymes or alkaloids to nitrate the biological samples. The process of nitration may affect the ionization and transport of nanoparticles. The introduction system and the improved cyclone chamber allow direct analysis of the diluted blood sample without digestion, effectively reducing the error caused by digestion. The swirling spray chamber without the baffle can greatly increase the transmission efficiency while allowing a large biological cell to enter, reducing the pretreatment steps of the blood sample. In this work, the blood of mice exposed to three different concentrations of 5 μg/L, 250 μg/L, and 500 μg/mL AuNPs was measured by the spICP-MS method of the improved injection system. The results showed that the blood was 30 s later. Most of the AuNPs in the blood have been metabolized, and only 32 μg/mL were detected in the blood of mice exposed to 500 μg/mL. The study shown that the concentration of nanoparticles in the blood peaked about 1 hour after exposure, and then the concentration of nanoparticles in the blood gradually decreased with time. The recovery rate of this method is 111.74%, and the method is credible.
4. Distribution characteristics of silica-coated gold nanoparticles in mice detected by spICP-MS
The absorption, distribution, accumulation and metabolism of particulate matter in vivo are essential for understanding the toxicity mechanism of particulate matter. In order to understand the absorption and distribution of particulate matter in vivo, the mice were exposed to breath by Au@SiO2 particles. After dissection, the distribution in vivo was analyzed by spICP-MS. The results shown that the Au@SiO2 particles partially deposited in the lungs, and some passed through the alveolar-capillary barrier to enter the blood circulation and migrated to the heart and liver, which may eventually cause lesions in these organs. The distribution of nanoparticles in animals is influenced by factors such as exposure pathways and nanofeatures, in addition to traditional factors including the rate at which particles are distributed to tissues and organs. Studying the distribution of Au@SiO2 nanoparticles in vivo helps to understand their targeting and behavior in vivo, and because the surface is silica, it is consistent with the surface properties of silica particles in the atmosphere. It reveals the possible migration and distribution of silica particles with similar particle size in the atmosphere, and provides a basis for studying the migration and biodistribution of silica particles in animal fine particles.
By improving the sample introduction system of single particle inductively coupled plasma mass spectrometry, this project has improved the transmission efficiency and expands the detected range of sample species. At the same time, spICP-MS method has been used to detect the concentration of gold nanoparticles in blood samples at different times, providing a research method for studying the release of nanoparticles in blood as drugs or drug carriers. The method was also used to study the distribution of silica coated gold nanoparticles like as atmospheric particulate matter in mice, which provided a basis for studying the distribution of atmospheric fine particulate matter into human body and the changes in blood concentration.