Soft Lithography Enhances Biological Cells Imaging

The development of microarrays for analysis and manipulation of cells or viruses has attracted considerable interest from both researchers and biomedical related industry. Different kinds of biological microarrays are under intense investigation to facilitate early detection and analysis of biological events; these are DNA microarrays, Protein microarrays, Tissue and Antibody gene chip analysis, chemical compound arrays to name a few.

Within the MacDiarmid Institute for Advanced Material and Nanotechnology, we are investigating the use of nanoscale imaging technologies that might help in the fundamental understanding of cell function and lead to early diagnosis of diseases at a single cell and molecular level.

We have recently developed a novel technique for replicating biological cellular and sub cellular structures^1-4. This method facilitates imaging individual cells at high resolution and offers a snap shot record of cell response to stimulus. Termed Bioimprint, it has enabled us to detect features of fusion pores in cells at unprecedented resolution down to the nanometer scale (nano-bio-imaging). Bioimprint integrates soft lithography directly with biological materials to create replica cell impressions in a robust storage medium to facilitate topographical analysis using Atomic Force Microscopy.

In combination with our BioChip platform^5,6, which traps individual cells in its cavities, we are creating a very powerful tool for single cell analysis. Single cell analysis is utilised to provide unique understanding of important biological mechanisms as it enables us to look at the response of individual cells to different stimulation conditions.

In developing a protocol for the bioimprint/biochip processes a new polymer has been especially prepared by our collaborators at the New Zealand Plant and Food Research Centre for this work that showed promising results as it cures at room temperature under UV exposure and we have achieved the imprinting of muscle cells with high precision.

Using these techniques we were the first to show AFM images of cancer cells and investigate the potential of imaging techniques for early detection and analysis of cancer.

AFM images at two powers of magnification, in which craters and pores are visible and AFM trace scans.

We have explored nanoimaging of exocytotic pores on cell membranes through which a biological cell transfers peptides to the outside of the cell. Some peptides can stimulate cancer growth. Peptides are made in cells and packaged into granules within the cell. The membrane that surrounds the cell merges with the membrane of the secretory granule. As the two membranes have similar chemical structure, being lipoprotein, each can dissolve in the other at the point of contact. When this occurs a gap forms in the cell's membrane and the interior of the granule is exposed to the exterior of the cell; the peptide that will stimulate cancer growth can depart through this pore that has formed. This process is termed exocytosis; the gap is called an exocytotic pore. Such pores can now be studied at the nanoscale level.

Clearly if we could alter the release of the compounds from cells then novel treatments for cancer may eventuate. The emerging evidence that disruption of normal exocytosis itself is implicated in cancer growth makes the characterisation of the process even more important. However there is little understanding of how the formation of the pores and their function in diseases such as cancer, nor how the pores may be used as a target of treatments.

This work should lead to a new insight of cell responses and communication and might help in early diagnosis of cell deformation especially in cancer cell studies. It is important that we advance to investigate live cells in the biochip/bioimprint system, but there are challenging barriers that require careful consideration and innovative nanoengineering solutions.

Applications of Bioimprint technique in the formation of 3D biocompatible scaffolds for tissue engineering is underway.

References

1. Alkaisi, M.M., Muys, J.J., Evans, J.J., "Single cell imaging with AFM using Biochip/Bioimprint Technology" 2009 invited paper, Special Issue of International Journal of Nanotechnology on New Zealand Science, issue3-4, Vol, 6, 355-368, (2009).
2. Alkaisi, M.M., Muys, J.J., Evans, J.J.,"Invited paper" "Bioimprint Replication of Single Cells on a Biochip", BioMEMs and Nanotechnology, Proc of SPIE Vol 6799, U212-U221 , 2007.
3. Muys, J, Alkaisi, M.M., Evans, J.J., Melville D.O.S. Nagase, J., Oaruez, G.M., Sykes, P., (2006), "Cellular Transfer and AFM imaging of Cancer cells using Bioimprint", Journal of Nanobiotechnology, (2006), 4:1. ISSN 1477-3155.
4. Muys, J., Alkaisi, M.M., Evans, J.J.(2006) "Bioimprint: Nanoscale analysis by replication of cellular topography using soft lithography" Journal of Biomedical nanotechnology, Vol 2, No 1, April 2006, pp 11-15.
5. Muys, J., Alkaisi, M.M., Evans, J.J. "Cellular replication and AFM imaging using UV-Bioimprint technique", Nanomedicine: Nanotechnology, biology and Medicine, 2(3) 2006.
6. Muys, J., Alkaisi, M. M. Evans, J. J. and Nagase, J. (2005). "Analysis of dielectrophoretically trapped biological cells by atomic force microscopy using an integrated biochip platform". Japanese Journal of Applied Physics, Vol.44, No.7B, pp.5717-5723.