Single molecule trafficking in targeted neurons using nanoparticles

Neurons communicate by chemical transmission. These chemicals are released from nerve terminals (exocytosis) and act at specific receptors on the next neuron which are then internalised (receptor-mediated endocytosis), Figure 1. We will hijack these normal neuronal communication pathways by tagging the chemicals with specially engineered, highly visible, photostable nanoparticles. Using innovative imaging techniques, trafficking of these particles will be followed in single, functionally identified neurons. This will provide an understanding of the processes of exo-and endocytosis and ultimately permit delivery of nanoparticles, potentially capable of carrying drugs to a targeted site in the brain.

Figure 1. Schematic diagram of the cell hijacking with a nanoparticle (red octagon). Vesicle migration (bilayer circles) via stages 1 to 6 eventuates to the vesicle opening to the intracellular space, which exposes an enzyme biomolecule (green circle) to external environment. The antibody (blue forks)-biofunctionalised nanoparticle can bind to this enzyme and be internalised via step 7.

Our first step is aim to study the process of nanoparticle trafficking in cells by receptor-mediated-endocytosis. Specifically, it is the somatostatin peptide receptor mediated endocytosis studied by using cell culture. In neurons, it control the blood pressure (Ann's group research) Recently, we obtained some results in progressing which is show in following Figure 2.

AR42J cell line, a rat pancreatic tumour was used to check the particle trafficking. The cells were incubated with amino group coated quantum dot (NH-QD) solution and the solution with quantum dot further conjugated with somatostatin (SSt) molecules (SSt-QD). The incubation time length was 5 or 30 min. After fixation, the cell nuclei were stain with Hoechst 33342 (a nuclear dye, blue). We can see the endocytosis difference from the confocal images due to functional groups on the particle surface and the incubation time. The cells absorbed more SSt-QDs than NH-QDs for the same incubation time. Longer incubation time allows cells to take in more particles, 30 min > 5 min.

Figure 2. somatostatin conjugated and unconjugated amimo-quantum dots are internalized by AR42J (Rat pancreas tumor) cells.

This project has been funded by Macquarie Research Innovation fund scheme, and carried out collaboratively with A/Prof Ann Goodchild, Australian School of Advanced Medicine, and Prof Ewa Goldys, Physics, MQ

For more information on this project, please contact A/Prof A. Zvyagin.

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Last modified: 17 06, 2011