Cyclic Peptide-Gadolinium Nanoparticles for Enhanced Intracellular Delivery.

Amir Nasrolahi Shirazi,Luiza Baloyan,Muhammad Imran Sajid,Keykavous Parang,Sandeep Lohan,Ryley Hall,Dindyal Mandal,Shirin Rad,Khalid Zoghebi,Shang Eun Park,Rakesh Kumar Tiwari

doi:10.3390/pharmaceutics12090792

Abstract

A cyclic peptide containing one cysteine and five alternating tryptophan and arginine amino acids [(WR)5C] was synthesized using Fmoc/tBu solid-phase methodology. The ability of the synthesized cyclic peptide to produce gadolinium nanoparticles through an in situ one-pot mixing of an aqueous solution of GdCl3 with [(WR)5C] peptide solution was evaluated. Transmission electron microscopy showed the formed peptide-Gd nanoparticles in star-shape morphology with a size of ~250 nm. Flow cytometry investigation showed that the cellular uptake of a cell-impermeable fluorescence-labeled phosphopeptide (F′-GpYEEI, where F′ = fluorescein) was approximately six times higher in the presence of [(WR)5C]-Gd nanoparticles than those of F′-GpYEEI alone in human leukemia adenocarcinoma (CCRF-CEM) cells after 2 h incubation. The antiproliferative activities of cisplatin and carboplatin (5 µM) were increased in the presence of [(WR)5C]-GdNPs (50 μM) by 41% and 18%, respectively, after 72-h incubation in CCRF-CEM cells. The intracellular release of epirubicin, an anticancer drug, from the complex showed that 15% and 60% of the drug was released intracellularly within 12 and 48 h, respectively. This report provides insight about using a non-toxic MRI agent, gadolinium nanoparticles, for the delivery of various types of molecular cargos.

Highlights

Metal-containing materials have been used extensively in designing various biomedical projects such as imaging cargos, detection markers and therapeutics [1,2]
Intermediate and final compounds were purified by reversed-phase high-performance liquid chromatography (RP-HPLC) from Shimadzu (Prominence, Columbia, MD, USA) using a gradient system of acetonitrile and water with 0.1% trifluoroacetic acid (TFA) using a reverse-phase column (XBridge BEH C18 OBD Prep Column), from Waters Corporation (Milford, MA, USA)
The presence of gadolinium enhanced the uptake even further by approximately 1.7 folds in comparison with that of peptide alone. Another control experiment was performed by using the phosphopeptide (F -GpYEEI) alone. These results show that, the presence of the peptide is necessary for enhanced delivery efficiency of the carrier, the gadolinium nanoparticles improve the cellular uptake of the drug, suggesting that the uptake of the drug was significantly enhanced, presumably due to the new orientation of amino acids and gadolinium nanoparticles

Summary

Introduction

Metal-containing materials have been used extensively in designing various biomedical projects such as imaging cargos, detection markers and therapeutics [1,2]. Optimized functionality of metal-containing materials could be obtained by utilizing various elements such as size, active surface, morphology and stability properties. Gadolinium offers a paramagnetic property due to the presence of seven unpaired electrons in the 4f shell, which makes it a potential agent for magnetic resonance imaging (MRI) [6]. It enhances MR images by reducing T1 relaxation constant of the tissues in which accumulated. Gd containing complexes have been used widely, they suffer from leaching issues where non-metabolizable Gd3+ ions could potentially induce toxicity through accumulation in the body. Discovering novel Gd-containing complexes with insignificant toxicity could be of potential interest for researchers

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