Onsager's irreversible thermodynamics of the dynamics of transient pores in spherical lipid vesicles

Cyclic Activity of an Osmotically Stressed Liposome in a Finite Hypotonic Environment

A lipid vesicle, or simply called a liposome, represents a synthetic compartment for the examination of transmembrane transport and signaling phenomena. Yet, a liposome is always subjected to size and shape fluctuations due to local and global imbalance of internal and external osmotic pressures. Here, we show that an osmotically stressed liposome placed within a hypotonic spherical bath undergoes cyclic dynamics described by a periodic sequence of swelling and relaxation phases. These two phases are interfaced by the appearance of a transient transmembrane pore through which chemical delivery occurs. An analytical model was formulated for the recurrent differential equations that convey the time-dependent swelling phase of a pulsatory liposome during individual cycles. We demonstrate that the time-dependent swelling phases of the last several cycles of a pulsatory liposome are strongly dependent on the size of the external bath. Furthermore, decreasing the size of the hypotonic medium reduces the number of cycles of a pulsatory liposome. Comparisons and contrasts of an infinite hypotonic bath with finite external baths of varying radii are discussed.

Review on the Macro-Transport Processes Theory for Irregular Pores able to Perform Catalytic Reactions

We review and generalize a recent theoretical framework that provides a sound physicochemical basis to describe how volume and surface diffusion are affected by adsorption and desorption processes, as well as by catalytic conversion within the space defined by the irregular geometry of the pores in a material. The theory is based on two single-dimensional mass conservation equations for irregular domains deduced for the volumetric (bulk) and surface mass concentrations. It offers a powerful tool for analyzing and modeling mass transport across porous media like zeolites or artificially build materials, since it establishes how the microscopic quantities that refer to the internal details of the geometry, the flow and the interactions within the irregular pore can be translated into macroscopic variables that are currently measured in experiments. The use of the theory in mass uptake experiments is explained in terms of breakthrough curves and effective mass diffusion coefficients which are explicitly related to the internal geometry of the pores.