In recent years, synthetic nanoparticles have been widely used in biomedicine, optics, electronics and so on, and have become one of the most popular scientific research fields. Semiconductors, metals, polymers and carbon-based nanoparticles are used in high-resolution imaging (nuclear magnetic resonance, fluorescence), disease diagnosis, drug targeting, protein purification, pathogen detection, cancer treatment, and food safety. Environmental monitoring and other fields are playing an increasingly important role. However, the application of nanoparticles has also led to the exploration of the toxicity of nanoparticles, such as the ability of nanoparticles to aggregate in tissues to produce genetic variation. Single nanoparticles can also make proteins gather on their surface to form protein crowns, thus affecting the normal functioning of biological systems. The safety of nanomaterials is mainly measured by dose, chemical composition and exposure pathway. However, the safety of nanomaterials is also related to their particle size, shape, adsorption force and charge.
####Size Differentiation and Absolute Quantification of Gold Nanoparticles
Nanocrystalline gold has attracted much attention in medical, biological analysis and catalytic applications for its unique photothermal properties. Accurate particle size and concentration analysis is very important in the process of synthesis, surface functionalization modification and development analysis of gold nanoparticles. TEM is the most commonly used method to characterize the morphology of gold nanoparticles. DLS can quickly measure the particle size of gold nanoparticles. But only uniform samples can be measured. Compared with many methods of measuring gold nanoparticles, the accurate measurement of concentration is lack of effective means. The concentration of gold nanoparticles is usually analyzed by combining transmission electron microscopy (TEM) with inductively coupled plasma mass spectrometry (ICP-MS or ICP-AES). The particle concentration of nanocrystalline gold was estimated by the determination of the particle size and the atomic concentration of gold after nitration. This method is not only cumbersome and time-consuming, but also deviates from the calculation of the volume due to the irregular shape of the nanoparticles and the uneven size of the nanoparticles, which leads to the deviation between the experimental results and the actual situation. An absolute quantitative analysis method of particle concentration without standard sample was developed by means of single particle count and volume flow rate of sample per unit time. In addition, a very simple quantitative method of fluorescence internal standard was developed by using the multi-parameter detection performance of the instrument.
Figure 1. Flow cytometric analysis of single GNPs.
Figure 2. Absolute quantification of GNPs.
Figure 3. Relationship between the ratios determined by NanoFCM and the theoretical ratios.
J. Am. Chem. Soc. 2010, 132, 12176-12178.