Targeted Intracellular Delivery of Amino Acids to Trophoblast Cells Reveals Proteomic Signatures of Cellular Utilisation

Targeted delivery systems offer a promising approach for selectively modulating cellular processes; yet the intracellular consequences of targeted nutrient delivery to trophoblast cells remain poorly defined. Here, we investigated a previously validated placenta-targeting peptide conjugated to liposomes encapsulating stable isotope-labelled L-arginine and L-lysine to examine cellular uptake and downstream molecular responses in a trophoblast-like cell model. Peptide-dependent uptake of fluorescently labelled liposomes was confirmed in BeWo cells, demonstrating selective internalisation compared with non-targeted controls. Encapsulation of isotope-labelled amino acids enabled direct quantification of intracellular delivery and incorporation into the cellular proteome using stable isotope labelling by amino acids in cell culture (SILAC). Quantitative proteomic analysis revealed coordinated changes in proteins associated with translation, metabolism, and nitric oxide synthase regulation following targeted liposomal uptake. Notably, V-type proton ATPase subunit G1 (ATP6V1G1) and large neutral amino acid transporter small subunit 1 (SLC7A5) showed increased incorporation of labelled amino acids and were independently validated by Western blotting. Together, these findings establish a proof-of-concept platform for targeted intracellular amino acid delivery to trophoblast-like cells and define the resulting proteomic responses. This work provides mechanistic insight into intracellular amino acid utilisation and a framework for future studies in placental cell biology.