Electron microscopic image of a single human lymphocyte. Source: Wikipedia.
Associate Professor John X. J. Zhang of the University of Texas at Austin spoke at the Jones Seminar at the Thayer School of Engineering this past Friday about his research in the field of cancer detection technology.
Zhang’s talk encompassed three areas of his lab research, all of which are predicated on miniaturizing and integrating micro and nano scale technologies: multispectral quantum dot based imaging, miniature cancer imaging microscopes, and nanoscreening of circulating tumor cells in blood (CTCs).
Cancer spreads and kills by metastasis and looking for CTCs in the blood may reveal the mechanism of metastasis. However, CTCs are rare and difficult to separate from the blood. Zhang estimated that depending on the type of cancer a person has, there might be approximately three to five CTCs present in 7.5 milliliters of blood. There are some existing mechanisms to detect CTCs, including immunomagnetic and microfluidics assays, and work is being done to continue to develop new technologies. The effort to detect CTCs has spread to the commercial realm as well; Johnson & Johnson made a cell detection machine called the Veridex Cell Search that many researchers now use as a control for detection experiments.
Zhang’s approach to CTC detection involves the magnet tagging of CTCs with ferric oxide (Fe2O3) and gold. Zhang used a magnetic apparatus that is able to search for CTCs using a catch-and-release mechanism as blood flows through a thin microfluidic chip. This method, known as a microchip-based immunomagnetic assay, is efficient in capturing CTCs. Zhang’s microchip apparatus inverts as the blood runs through it in order to allow nonmagnetic particles in the blood to fall off. Zhang then quantifies his CTC capture rate by comparing the ratio of the number of CTC cells captured experimentally and the number of CTC cells in the control. Zhang predicts that the capture efficiency will be much higher if the microchip is embedded with nanomagnets.
The second and third areas of development into cancer and biomedical technology were types of cellular imaging based on spectral quantum dots and miniature microscopes. The imaging technique involves staining cancer cells and then observing excitation wavelengths from light supplied from a quantum dot light emitting diode (QDLED) source. Quantum dots are nano-scale particles made of semiconducting materials. They typically exhibit various optical and electrical properties; they emit photons when excited, and this is how they excite cancer cells.
The other type of imaging, which uses cancer screening miniature microscopes, is based on development of the optical MEMS (Micro Electro Mechanical Systems) scanner. The current gold standard for cancer imaging and treatment involves radiation (for both screening and treatment,) surgical excision and biopsy analysis. The MEMS scanner aims to screen for cancer in a non-invasive fashion that does not use radiation. These miniature scanners have extremely high resolution, as the light source also involves quantum dots.
Professor Zhang stated that his research is organized in a system to miniaturize technology and then integrate it into medical practice. Zhang believes micro- and nano-scale technologies to be more efficient and less invasive than the existing practices.
References:
1 J. Zhang. “Engineering Biology and Medicine at Small Scales: From Cell Manipulation, Molecular Screening to Early Cancer Detection.” Thayer School of Engineering, Dartmouth College. Hanover, 26 April 2013.