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The traceability and availability of nanoparticles enables their use to enhance a variety of nano-biological and nano-medicinal applications. The particular size and shape of nanoparticles determine the uptake rate and pathway into the cell, and therefore impact specific cell components and processes. Selecting specific particle types allows researchers to target the process or structure of interest, with minimal additional impact. This can be used for drug or DNA delivery, and is being explored for use in oncology. Understanding the different uptake mechanisms and impacted processes requires sub-cellular Imaging resolution to determine, for example, whether or not the nanoparticles are reaching the nucleus.
Sub-cellular imaging has traditionally been challenging to achieve with laser ablation ICP-MS due to a lack of sensitivity at small spots. Bioimaging using LA-ICP-MS is a well-established technique, but usually applied on the tissue scale, which depends on larger spot areas where sensitivity is less problematic. The improved sensitivity and washout from the NWRimage has allowed faster imaging of smaller spots. The NWRimage also provides the possibility of true sub-micron spot sizes. This work compares the capabilities of standard laser Ablation (NWR213 system) with results from the NWRimage platform, which has been optimized for imaging applications.
Nanoparticles (NPs) have potential applications in medical diagnostics, imaging, drug delivery and other kinds of therapy. Furthermore, studies concerning nanoparticle uptake by cells are important for risk assessment. Size, shape and surface modification of the NPs determine the uptake rate and pathway into the cells, and therefore impact specific cell components and processes. Understanding the different uptake mechanisms and involved processes require sub-cellular resolution to determine, for example, whether the nanoparticles are reaching the nucleus. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is an established quantitative multi-elemental analysis and mapping technique. However, sub-cellular imaging has traditionally been challenging to achieve due to a lack of sensitivity at small laser spots. But now novel laser ablation systems with improved sensitivity and washout time allow imaging at high lateral resolution with spot sizes down to 1 µm.
Here LA-ICP-MS was applied for the imaging of individual fibroblast cells to study the uptake and intracellular processing of metal-containing NPs. To indicate cell morphology the local distribution of naturally occurring elements in cells like P and Zn was measured, too. Our results show that LA-ICP-MS can be used to localise nanoparticle aggregates within cellular compartments. The studied NPs accumulate in the perinuclear region in the course of intracellular processing, but do not enter the cell nucleus. The uptake efficiency depends strongly on the physico-chemical properties of the nanostructures as well as on the incubation conditions like concentration and incubation time. The potential of LA-ICP-MS for analysis at single cell level will be demonstrated.
Studying the interaction of nanoparticles (NPs) with cells has become a growing field of interest. Research topics are ranging from nanotoxicology to medical applications e.g. as theranostic agents. In order to evaluate nano-bio interactions, the number of NPs inside cells as well as their localisation within cellular substructures is of particular interest.
In recent years, elemental imaging of biological samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining more and more importance. Latest instrumental developments regarding spatial resolution (down to 1 µm) and detection efficiency make LA ICP-MS particularly interesting for single cell analysis.
Here, we have applied LA-ICP-MS for sub-cellular scale imaging of individual cells to study the NP pathway from uptake, via intracellular processing up to cell division. Furthermore, the local distribution of naturally occurring elements in cells like P was measured to indicate the cell morphology.
Murine fibroblast cells were incubated with different metal-containing NPs under varying experimental conditions. For LA analysis, the cells were fixed and dried. Sub-cellular resolution was achieved by careful optimisation of the laser ablation parameters. By rastering with the laser beam across the sample, a two-dimensional image of the elemental distribution can be received. Our results show that LA-ICP-MS is able to localise NP aggregates within cellular substructures. The studied NPs accumulate in the perinuclear region in the course of intracellular processing, e.g. multivesicular fusion and endosomal maturation, but do not enter the nucleus. The uptake depends on the physico-chemical properties of the nanostructures and on the incubation conditions like concentration and incubation time. Additionally, the number of NPs internalized by individual cells was determined and variations within a cell population became visible.
The findings demonstrate the potential of LA-ICP-MS providing insight into NP uptake and intracellular distribution dependent on experimental parameters.
Gold nanostructures that serve as probes for nanospectroscopic analysis of eukaryotic cell cultures can be obtained by the in situ reduction of tetrachloroauric acid (HAuCl4). To understand the formation process of such intracellularly grown particles depending on the incubation medium, the reaction was carried out with 3T3 fibroblast cells in three different incubation media, phosphate buffer, Dulbecco's Modified Eagle Medium (DMEM), and standard cell culture medium (DMEM with fetal calf serum). The size, the optical properties, the biomolecular corona, and the localization of the gold nanoparticles formed in situ vary for the different conditions. The combination of surface-enhanced Raman scattering (SERS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) microscopic mapping and transmission electron microscopy (TEM) provides complementary perspectives on plasmonic nanoparticles and non-plasmonic gold compounds inside the cells. While for the incubation with HAuCl4 in PBS, gold particles provide optical signals from the nucleus, the incubation in standard cell culture medium leads to scavenging of the toxic molecules and the formation of spots of high gold concentration in the cytoplasm without formation of SERS-active particles inside the cells. The biomolecular corona of nanoparticles formed in situ after incubation in buffer and DMEM differs, suggesting that different intracellular molecular species serve for reduction and stabilization. Comparison with data obtained from ready-made gold nanoparticles suggests complementary application of in situ and ex situ generated nanostructures for optical probing.