Carnegie Mellon University
February 10, 2015

Designing Biomimetic Capsules and Gels that Undergo Directed Movement

Professor Anna Balazs

Distinguished Professor of Chemical Engineering

The Robert v. d. Luft Professor, Department of Chemical & Petroleum Engineering University of Pittsburgh


Our  goal  is  to understand how  protocells  developed  signaling  mechanisms  that  allowed them  to  communicate  and  coordinate  their  actions.  The  capability  to  respond  to  signals,  move, and   assemble   into   cohesive   colonies   would   have   significantly   improved   the   protocells’ survivability and  enhanced  their  functionality. Early  protocells  lacked  complex  biochemical machinery  and  thus,  communication  was most  likely driven  by  fundamental  physical/chemical mechanisms, including diffusion of molecules across the membrane. In this context, it is worth considering the behavior of primitive organisms, such as Dictyostelium discoideum (slime molds or social amoebas) who survive and replicate by releasing chemo-attractants, which drive them to move towards each other and aggregate into larger colonies. Based on the survival tactics of these  primitive  organisms,  we  hypothesize  that  this  mode  of  communication—the  release  of signaling molecules, recognition of these molecules and motion in response to gradients of these molecules—served  as  a  useful  mechanism  for  protocell-protocell  communication. To  this  end, we develop computational  models  that  provide an  ideal  starting  point  for  integrating  both  the spatial   and   temporal   behavior   of   assemblies   of   protocells   and   investigating   the   role   of physicochemical  phenomena  in  enabling  responsive,  collective  behavior.  In  these studies, micron-sized capsules release signaling  inhibitor  and  promoter  molecules,  which  modify the permeability of the capsules’ shells and create local adhesion gradients on an underlying surface. Hence,  these  capsules  both  sense  and  modify this  environment.  Due  to  this  mode  of signaling, these capsules can self-organize into various autonomously moving structures. Our findings also demonstrate the  importance  of  noise and  hydrodynamics  in  guiding  the  self-organization  of  the capsules. The results  of  these studies  can  provide  some  insight into  communication and collective behavior among early protocells.