The only factor that affects the size of the particles produced is not only the loading capacity of the particles but also how they are absorbed into the target tissue. Basically, the particles are taken up into the cell by energy-independent and energy-dependent pathways. The energy-independent pathway, as the name implies, is a process that does not require energy for the uptake of nanoparticles into the cell. The particles pass through the cell membrane by free diffusion. In contrast, the other form of cellular uptake requires the use of energy in the form of ATP. This pathway of cellular uptake is divided into pinocytosis and phagocytosis. Pinositos (Pino means "to drink") is the uptake of solutes from the environment into a liquid. This process is, in a sense, the drinking of the cell. In contrast, phagocytosis is, in a sense, the eating of the cell. In cellular uptake, the factor that determines which of the energy-consuming pathways takes up the substances is the size of the particle. Particles with a size of 0.5 μm-10 μm are drunk by the cell, whereas particles with smaller sizes are eaten by the cell . A concise summary of all uptake mechanisms is shown in Figure 7 .