Medical researchers have long known that diseases can cause -- or be caused by -- physical changes in individual cells. For instance, invading parasites can distort or degrade blood cells, and heart failure can occur as muscle cells lose their ability to contract in the wake of a heart attack. Knowing the effect of forces as small as a piconewton -- a trillionth of a newton -- on a cell gives researchers a much finer view of the ways in which diseased cells differ from healthy ones. A pioneering group of materials scientists are working closely with microbiologists and medical researchers to learn more about how our cells react to tiny forces and how their physical form is affected by disease.
Infected blood cells become more rigid, losing the ability to reduce their width from eight micrometers down to two or three micrometers, which they need to do to slip through capillaries. Rigid cells, on the other hand, can clog capillaries and cause cerebral hemorrhages. Using optical tweezers, which employ intensely focused laser light to exert a tiny force on objects attached to cells, Subra Suresh and his collaborators showed that red blood cells infected with malaria become 10 times stiffer than healthy cells -- three to four times stiffer than was previously estimated.