 Delivery into adult tissues is usually difficult , though there are a few systems allowing useful uptake of unmodified Morpholino oligos ( including the inherently leaky muscle cells caused by Duchenne muscular dystrophy or the vascular endothelial cells stressed during balloon angioplasty ) . Though they permeate through intercellular spaces in tissues effectively , unconjugated <unk> have limited distribution into the cytosol and nuclear spaces within healthy tissues following IV administration . Systemic delivery into many cells in adult organisms can be accomplished by using covalent conjugates of Morpholino oligos with cell @-@ penetrating peptides , and , while toxicity has been associated with moderate doses of the peptide conjugates , they have been used in vivo for effective oligo delivery at doses below those causing observed toxicity . An octa @-@ <unk> dendrimer attached to the end of a Morpholino can deliver the modified oligo ( called a Vivo @-@ Morpholino ) from the blood to the cytosol . Delivery @-@ enabled Morpholinos , such as peptide conjugates and Vivo @-@ Morpholinos , show promise as therapeutics for viral and genetic diseases . 
