Nanosensors have learned to stick to living cells
Alexander Voityuk, N+1
A group of scientists from the King Abdullah University of Science and Technology has developed nanodetectors capable of sticking to the surface of living cells and transmitting information about their thermophysical properties without damaging them. Article by ElAfandy et al. Nanomembrane-Based, Thermal-Transport Biosensor for Living Cells is published in the journal Small.
Knowledge of the thermophysical properties of living cells is important for use in various fields of biology and technology, for example in thermography, for the detection and treatment of cancer, or in assessing the health and viability of cells. However, when creating devices capable of determining such parameters, developers face two problems — the cells are small in size and have variable uneven shapes. In addition, there is a high risk of damaging the cell membrane during measurements. Now, researchers have been able to work around all these problems and create such a device.
The sensor itself consists of a flexible nanomembrane, 40 nanometers thick, based on gallium nitride (GaN), which is able to fit snugly to the cell wall and provide good thermal contact. GaN was chosen because of reliability, chemical stability and biocompatibility. The membrane is irradiated by monochromatic pulses of a helium-cadmium laser operating in the ultraviolet range. The laser pulse heats the membrane and causes photoluminescence, while light is emitted at a frequency depending on the temperature of the membrane. This temperature, in turn, depends on the thermophysical properties of the cell — thermal conductivity and thermal conductivity, which can be determined. The spatial accuracy of the technique is determined by the spot width of the focused laser pulse. A thin disk of gold (with a diameter of 2.35 micrometers and a thickness of 250 nanometers) is inserted between the nanomembrane and the cell, which absorbs all transmitted laser radiation, allowing heating of the membrane and heat transfer to the cell without damaging it with UV radiation.
A nanosensor device and a scheme for determining the thermophysical properties of a cell. The inset shows the processes occurring when a laser pulse (thick black arrow), spontaneous light radiation (blue arrows) and heat diffusion through the cell (thin black arrows) are exposed to the membrane
The researchers used the created sensor to study the properties of two types of cancer cells — breast cancer and cervical cancer. It turned out that the measured thermophysical properties of cells differ, not only in the case of different types of cancer, but also in the case of different subtypes of the same type of cancer (ductal and luminal breast cancer). There was a correlation between the invasiveness of cancer cells (their ability to spread in the body) and their thermophysical properties. All this indicates the possibility of using this development in medicine in the diagnosis of cancer. In addition, the sensor has been successfully used to determine the heat-conducting properties of glasses and polymers.
Experimental determination of thermophysical properties of cancer cells. (a) An image of a GaN membrane with an attached Au microdisk obtained on an optical microscope. (b) An image of a GaN membrane with an attached Au microdisk obtained by atomic force microscopy. (c) Sensor height profile. (d) The process of transferring the sensor to living cells using a tungsten needle. e) Micrograph of a cancer cell (green) covered with a nanomembrane (magenta). An image in false colors obtained on a scanning electron microscope. f) Experimental data obtained on photoluminescent radiation for different groups of cancer cells.
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