PCFT Independent Cellular Uptake of Cyclic Cell Penetrating Peptide Conjugated Folic Acid.

Folic acid is an essential component of many metabolic processes, including the synthesis of nucleoproteins, purines, and pyrimidines and is a recommended supplement to lower the incidence of various disorders. Folic acid and folate loaded nanoparticles are extensively evaluated for sustained release and enhanced stability of the molecule, however malfunctioning of Proton Coupled Folate Transporters (PCFT) present on the intestinal cells, and subsequent folate deficiency remain a major issue in this context. This study provides first demonstration where cell-penetrating peptide conjugated folic acid mediate PCFT independent folic acid permeabilization and intracellular bioavailability in vitro in the intestinal cells and macrophages. Cyclic-Transactivating transcriptional activator (cTAT) folic acid conjugates are prepared by solid phase peptide synthesis and are evaluated for the cellular uptake and bioavailability in the presence and absence of PCFT inhibitors. Compared with free folic acid that showed PCFT mediated cellular uptake, cTAT-folic acid conjugates exhibited enhanced cellular uptake at all studied pH and improved intracellular bioavailability of the cargo, as was determined by dihydrofolate reductase (DHFR) assay. Folic acid and cTAT-folic acid conjugates also dampened the production of pro-inflammatory mediators in the presence of toxins in vitro in macrophage cell lines.