Complexes comprising a shielding component

A polymer complex comprising

• a) a positively charged nanoparticle comprising a cationic polymer, a pharmaceutically acceptable salt thereof, or any stereoisomer or mixtures of stereoisomers, either of the compound of cationic polymer, or of any of its pharmaceutically acceptable salts;
• the cationic polymer being covalently or electrostatically bonded with at least one pharmaceutically, veterinary or cosmetically active ingredient;
• and
• b) at least one anionic copolymer selected from
• i. a copolymer comprising substructure I;
• ii. a copolymer comprising substructure II;
• and
• iii. a copolymer comprising substructure III;
• wherein the substructures III, and III are depicted as follows:
• -Am-Bn- Structure I
• —(Bn-Am)p-Bn- Structure II
• -(Am-Bn)p-Am- Structure III
• each instance of A is an amino acid residue is independently selected from methionine sulfoxide, ethionine sulfoxide, S-alkyl-cysteine sulfoxide, S-alkyl cysteine sulfone, S-alkyl homocysteine, S-alkyl homocysteine sulfoxide, glycosylated cysteine, serine, homoserine, homomethionine sulfoxide, sarcosine, glycine, and alanine;
• wherein at least 50 mol % of the A amino acid residues are methionine sulfoxide;
• wherein each instance of B is independently selected from glutamic acid, aspartic acid, and a salt thereof, and
• wherein:
• m is an integer from 20 to 600;
• n is an integer from 5 to 200;
• and
• p is an integer from 1 to 2.