Feature: Nanobiophysics: The Ultimate Frontier of the Physics of Cell

Ahead of the new Physics Café series which is being launched at St Mary’s University, Twickenham in October, Lecturer Dr Elisabetta Canetta discusses nanobiophysics and what it means for future research. We are currently living in a nanotechnology era, which means that most of the world’s devices (e.g. computers, mobile phones), objects (e.g. clothes, sport gears), and health products (e.g. toothpastes, sun creams) are based on technologies that work at the nanoscale. But what does “nanoscale” mean? Nanoscale is a composite noun: nano-scale. Nano is a unit and it means one billionth of a meter (i.e. 0,00000001m). So all the devices, objects, and health products that we use daily work using physical phenomena that can be observed only if we look at them using instruments called nanotools (i.e. tools that can see, manipulate, and measure objects that have dimensions as small as one billionth of a meter). Among these nanotools there are the ones used in nanobiophysics. Before going any further let us try to understand what nanobiophysics is. Nanobiophysics is again a composite noun: nano-bio-physics. Nano means one billionth of a meter, bio means life, and physics means the branch of science that studies forces, gravity, magnetic and electric fields, and so on. Putting these three definitions together we see that nano-bio-physics means the branch of science that studies the physical properties of living organisms at the nanoscale. From this, two questions arise, firstly, what are the physical properties of living organisms; and secondly, why do we need to study them at the nanoscale? A living organism can be a single cell, a tissue (i.e. a highly ordered cluster of cells), a bacterium. A cell can be soft (e.g. leucocytes, also called white blood cells, which protect our body from infections, viruses, etc) or hard (e.g. bone cells which form our skeleton), it can conduct electricity (e.g. neurons which are the cells of which our brain is made), and it can beat (e.g. heart cells that make up our heart). All these cell properties, i.e. soft, rigid, electric conductor, are physical, with soft and rigid belonging to the realm of mechanics and electric conductor to that of electricity. What about the bacterium? A bacterium can swim by using “tentacles” called flagella, makingample use of the physical laws of mechanics and fluid dynamics. If we want to understand fully how the human body or a plant works and how a disease (which could be caused by a bacterium) starts and progresses then we need to understand how every single component of our body, a plant, a disease works. It is like when we try to understand how a watch works, we open up the watch and start looking at each single piece individually and trying to make out how it functions. Nanobiophysics works to the same principle; we look at how every single cell or bacterium taken individually works. It becomes clear that the main aim of nanobiophysics is to study the behaviour of individual cells, bacteria and tissues by placing ourselves on their own scale. A cell is on average between 5 and 100 micrometers (1 micrometer = 0,000001m) and a bacterium is usually ~2-3 micrometers long and ~500 nanometers in diameter. The forces that they experience in their native environment (e.g. individual heart cells forming our heart) are as small as a few nanonewtons (1 nanonewton = 0,00000001 newtons, where 1 newton is the unit of force). Therefore, if we want to understand fully how our heart works then we must be able to detect such tiny forces and also to look at the details of one individual heart cell. To do this, we use nanotools, such as an Atomic Force Microscope (AFM) which allows us to see the finest details of the cell surface (Fig. 1) and to “poke” or “stretch” the cell with a special nanoprobe (Fig. 2) in order to measure how stiff the cell is or how strongly the cell is “clinging” to another cell or a tissue. For example, the last information is of particular importance in cancer research to understand how cancer cells move inside the body (i.e. how they metastasise) and form new (i.e. secondary) tumours in organs that are far from the primary tumour. Knowing this physical mechanism can help designing new anticancer treatments. Fig.1: 2D AFM image of a human bladder cell (Canetta et al., Acta Biomaterialia 10 (2014), 2043) Fig.2: Lateral image of an AFM probe “stretching” the membrane of a living endothelial cell (these cells form the inner walls of our blood vessels) (Canetta et al., Biorheology 42 (2005), 321) Nanobiophysics is, therefore, the ultimate frontier of the physics of cells whose final goal is to unravel the most complex biophysical phenomena that regulate our body, the different aspects of nature that are surrounding us, and the different diseases that make us, plants, and animals sick. This knowledge is crucial to design new cures, drugs, to solve problems like draught, crop production, and to use our body at its full potential. St Mary’s Physics Café is a new series of free public talks aimed at getting people to discuss science in a relaxed atmosphere. Starting on 27th October, there will be a range of speakers over the next year including Dr Elisabetta Canetta and physicists from the National Physical Laboratory.