Polyamidoamine-Remdesivir Conjugate: Physical Stability and Cellular Uptake Enhancement

Nucleoside analogue antiviral remdesivir works by inhibiting the RNA-dependent RNA polymerase enzyme and terminating the viral replication. Currently, remdesivir is under a clinical trial for its activity against SARS-CoV-2. In the blood, remdesivir will undergo an enzymatic reaction to become monophosphate analogue form which is difficult to penetrate into the cell membrane. PAMAM (polyamidoamine) dendrimer is a good carrier to encapsulate remdesivir as a water-insoluble drug (0,339 mg/mL). Entrapment of remdesivir in the PAMAM cavity avoided remdesivir molecules to not undergo the enzymatic reactions. This study aimed to synthesize, characterize and evaluate cellular uptake of PAMAM-Remdesivir conjugate. PAMAM-Remdesivir was prepared with various stirring times (3, 6, 12, 24, and 48 hours). The conjugates were characterized to observe the size and particle distribution using Particle Size Analyzer, encapsulating efficiency using UV-Vis Spectroscopy, interaction between PAMAM and remdesivir particle using Fourier Transform Infrared Spectroscopy and cellular uptake of PAMAM-RDV using Fluorescence Microscope. The optimized stirring time of PAMAM-Remdesivir conjugate was 24 hours wich resulted the particles charge of + 23,07 mV of zeta potential, 1008 nm of particle size, 0,730 of PDI, and 69% entrapment efficiency. In addition, the FTIR analysis showed that remdesivir molecules successfully conjugated to PAMAM. Thus, through strring optimization time, the remdesivir molecules were successfully entrapped to PAMAM cavity. The cellular uptake in Vero Cell of PAMAM-RDV conjugated fluorescein isothiocyanate was observed with fluorescence microscope and had a stronger intensity than remdesivir only solution.