ERBB2 and cancer: The blended H2.1MS1:MS2KN spheres are better choice than H2.1MS1KN particles due to i) higher efficiency of protein yields, ii) smaller size, iii) more defined spherical morphology, iv) higher HER2+ cell-binding potential, v) higher specific internalization into HER-overexpressing cancer cells, and finally vi) more efficient and stable delivery of functional siRNA.