This work presents results of rocket-borne measurements of dusty plasma parameters conducted in winter in high northern latitude ionosphere. It demonstrates that also smaller MSPs, i.e. with radii in sub-nanometer size range can be effectively charged and, thereby significantly influence plasma properties. Parameters of a charged MSP size distribution function were derived. The modelling results show that largest fraction of the charged MSPs reveal radii smaller than 1 nm and their density can exceed the density of electrons by up to an order of magnitude.