Creating spontaneous ‘cell’ division in artificial cell models

April 22, 2014

Spontaneous “cell” division (credit: SISSA)

Scientists of the International School for Advanced Studies (SISSA) of Triest have taken a first step toward the creation of functioning artificial cells by reproducing motility in their computer models, causing the “cells” to divide spontaneously without the action of external forces

The research could provide a better understanding of the development of life on our planet.

Droplets of filamentous material enclosed in a lipid membrane are the simplified models of the cell used by the SISSA physicists Luca Giomi and Antonio DeSimone, who simulated the spontaneous emergence of cell motility and division — features of living material in inanimate “objects,” the researchers note in a study published in Physical Review Letters and arXiv (open access).

The force exerted by the filaments is the variable that competes with another force, the surface tension that keeps the membrane surrounding the droplet from collapsing. This generates a flow in the fluid surrounding the droplet, which in turn is propelled by such self-generated flow. When the flow becomes very strong, the droplet deforms to the point of dividing. “When the force of the flow prevails over the force that keeps the membrane together we have cellular division,” explains DeSimone, director of the SISSA mathLab, SISSA’s mathematical modelling and scientific computing laboratory.

“We showed that by acting on a single physical parameter in a very simple model we can reproduce similar effects to those obtained with experimental observations” continues DeSimone. Empirical observations on microtubule specimens have shown that these also move outside the cell environment, in a manner proportional to the energy they have (derived from ATP, the cell “fuel”). “Similarly, our droplets, fueled by their ‘inner’ energy alone — without forces acting from the outside — are able to move and even divide.”

“Research on artificial cells has a long-standing tradition in chemistry and material science, Giomi told KurzweilAI in an email interview. “On the other hand, the notion of ‘active matter’ has become a central topic in soft matter physics and applied mathematics in the last decade. We are trying to bridge the gap between these communities and suggest that the mechanics of active materials could provide a potentially useful framework to understand the physics of minimal forms of life.

“Our theoretical work does not have so far any practical application, but does illustrate a number of physical mechanisms that could occur in biological materials. The same mechanisms could in principle be reproduced in synthetic materials and thus serve as an inspiration for the design of artificial minimal cells.”

Abstract of Physical Review Letters paper

We investigate the mechanics of an active droplet endowed with internal nematic order and surrounded by an isotropic Newtonian fluid. Using numerical simulations we demonstrate that, due to the interplay between the active stresses and the defective geometry of the nematic director, this system exhibits two of the fundamental functions of living cells: spontaneous division and motility, by means of self-generated hydrodynamic flows. These behaviors can be selectively activated by controlling a single physical parameter, namely, an active variant of the capillary number.