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

Abstract

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.

Structures of human folate receptors reveal biological trafficking states and diversity in folate and antifolate recognition

“…2), for hFRα or hFRβ via isothermal titration calorimetry at pH 7.4 and pH 6.5. A general expectation given the proposed pH dependence model for ligand release is that a lower affinity for folate would be seen at pH 6.5, the average pH of the recycling endosome (Table 1; Table S3) (2,42,53,63). Isothermal titration calorimetry (ITC) measurements demonstrate that hFRα has an extremely high affinity for folate with a dissociation constant (K d ) of ∼10 pM at pH 7.4.…”

Oxaprozin-Loaded Lipid Nanoparticles towards Overcoming NSAIDs Side-Effects

“…This way there is a potential in the targeting of activated macrophages using FR-β as target. It's possible to perform this targeting conjugating folate or folic acid on the drug system surface [79,93]. Chandrasekar et al, for example, created a folate-dendrimer conjugate loaded with indomethacin for specific drug delivery to inflammatory sites.…”

The role of folate receptor α in cancer development, progression and treatment: Cause, consequence or innocent bystander?

“…The basis for FRa-targeted drug delivery lies in the substrate specificity of folic acid to FRa. In a series of experiments, Leamon et al 94 showed that covalent conjugation of folic acid with various pharmaceuticals such as horseradish peroxidase, IgG serum albumin and ribonuclease, resulted in the nondestructive intracellular delivery of these molecules via FRa. In a subsequent study, the authors showed that cellular protein synthesis was inhibited in a time and dose dependent manner by the uptake of the folic acid-toxin conjugate into the cell, providing direct evidence that folic acid conjugates not only reach the cytoplasm but do so in a functionally active form.…”