Delivery of macromolecules into living cells: A method that exploits folate receptor endocytosis

C. P. Leamon, P. S. Low

Research output: Contribution to journalArticlepeer-review

564 Scopus citations


Difficulties with the nondestructive delivery of macromolecules into living cells have limited the potential applications of antibodies, genes, enzymes, peptides, and antisense oligonucleotides in biology and medicine. We have found, however, that the natural endocytosis pathway for the vitamin folate can be exploited to nondestructively introduce macromolecules into cultured cells if the macromolecule is first covalently linked to folate. Thus, treatment of KB cells with folate-conjugated ribonuclease, horseradish peroxidase, serum albumin, IgG, or ferritin allowed delivery of >106 copies of the macromolecules within a 2-hr period. Cytochemical staining using 4-chloro-1-naphthol further demonstrated that the horseradish peroxidase retained activity for at least 6 hr after internalization. Since folate is an essential vitamin required in substantial quantities by virtually all cells, these observations may open the possibility of scientific and medical applications for many of the above macromolecules.

Original languageEnglish (US)
Pages (from-to)5572-5576
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number13
StatePublished - Jul 1 1991


  • Folate uptake
  • Rug delivery
  • Vitamin endocytosis

ASJC Scopus subject areas

  • General
  • Genetics


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