The interaction with the highest electrostatic potential energy is the +2 and -2 particle separated by a distance of 5 nm. This is because the electrostatic potential energy between two charged particles is directly proportional to the product of the charges and inversely proportional to the distance between them. In this case, the product of the charges (+2 and -2) is 4, which is higher than any other combination given in the options. Additionally, the distance between them (5 nm) is smaller than any other option, further increasing the electrostatic potential energy.