Silsesquioxane compounds having one of the following basic chemical structures T6, T8, T10 or T12, wherein at least one of R1 to R6 in T6, R1 to R8 in T8, R1 to RIO in T10 or R1 to R12 in T12 is a group which comprises one or more guanidine groups and/or quaternary ammonium groups, wherein at least one of the groups of R1 to R6 in T6, R1 to R8 in T8, R1 to RIO in T10 or R1 to R12 in T12 contains at least one cargo molecular structure, wherein the cargo molecular structure contains a molecule which should be transported across cell membranes and is selected from active pharmaceutical ingredients, marker compounds which within cells are able to generate a measurable signal, and targeting structures which are suitable to accumulate the compounds at a desired site of action, and wherein the group which comprises one or more guanidine groups and/or quaternary ammonium groups consists of the structure group -X-A, - wherein A is selected from guanidine group and quaternary ammonium group, and - wherein X may be substituted or unsubstituted and is selected from branched or unbranched, cyclic or not cyclic, saturated or unsaturated alkylene and the group X 1 -L-X 2 , • wherein X 1 and X 2 each independently from each other may be substituted or unsubstituted and are selected from branched or unbranched, cyclic or not cyclic, saturated or unsaturated alkylene, • wherein L in group X 1 -L-X 2 is a linker group which is selected from carboxylic acid amide group, in particular amino carbonyl group (-HN-CO-) or carbonyl amino group (-CO-NH-); carboxylic acid ester group, in particular oxycarbonyl (-O-CO-) or carbonyloxy group (-CO-O-), including the respective thioesters, selenoesters or phosphorous esters; ether group; thioether group; imide group; imine group; oximes; sulfones including sulfone amine groups; peroxide groups; ketone groups; hydrazine groups; hydrazone groups; carboxylic acid hydrazide groups and disulfide bridges. - wherein A is selected from guanidine group and quaternary ammonium group, and - wherein X may be substituted or unsubstituted and is selected from branched or unbranched, cyclic or not cyclic, saturated or unsaturated alkylene and the group X 1 -L-X 2 , • wherein X 1 and X 2 each independently from each other may be substituted or unsubstituted and are selected from branched or unbranched, cyclic or not cyclic, saturated or unsaturated alkylene, • wherein L in group X 1 -L-X 2 is a linker group which is selected from carboxylic acid amide group, in particular amino carbonyl group (-HN-CO-) or carbonyl amino group (-CO-NH-); carboxylic acid ester group, in particular oxycarbonyl (-O-CO-) or carbonyloxy group (-CO-O-), including the respective thioesters, selenoesters or phosphorous esters; ether group; thioether group; imide group; imine group; oximes; sulfones including sulfone amine groups; peroxide groups; ketone groups; hydrazine groups; hydrazone groups; carboxylic acid hydrazide groups and disulfide bridges. • wherein X 1 and X 2 each independently from each other may be substituted or unsubstituted and are selected from branched or unbranched, cyclic or not cyclic, saturated or unsaturated alkylene, • wherein L in group X 1 -L-X 2 is a linker group which is selected from carboxylic acid amide group, in particular amino carbonyl group (-HN-CO-) or carbonyl amino group (-CO-NH-); carboxylic acid ester group, in particular oxycarbonyl (-O-CO-) or carbonyloxy group (-CO-O-), including the respective thioesters, selenoesters or phosphorous esters; ether group; thioether group; imide group; imine group; oximes; sulfones including sulfone amine groups; peroxide groups; ketone groups; hydrazine groups; hydrazone groups; carboxylic acid hydrazide groups and disulfide bridges. <EOS>