Fig. 2. Schematic of the processes involved in compartmental models of particle–cell interactions and particle internalisation. Nano-engineered particles interact with receptors and subsequently become bound to the cell membrane. The particles are either internalised or unbind from the receptors. Internalised particles can either be recycled or the vesicles can detach from the cell membrane and are subsequently transported through the cytosol, while the receptors are recycled back to the cell membrane. This process can be modelled via the chemical reaction, which describes the evolution of the number of particles in the fluid, [P]F, the number of receptors on the outside of the cell, [R]F, the number of particle–receptor complexes on the outside of the cell, [P − R]F, the number of internalised particle–receptor complexes, [P − R]I, the number of internalised particles, [P]I, and the number of internalised receptors, [R]I. This is equivalent to the above schematic. The k parameters represent the rates of particle–receptor binding (kb), particle–receptor unbinding (kd), particle–receptor internalisation (ki), particle–receptor exocytosis (ke), internalised particle–cell unbinding (ks) and receptor recycling (kr), respectively.
