Solution stability of linear vs. cyclic RGD peptides

Abstract

Arg-Gly-Asp (RGD) peptides contain an aspartic acid residue that is highly susceptible to chemical degradation and leads to the loss of biological activity. Our hypothesis is that cyclization of RGD peptides via disulphide bond linkage can induce structural rigidity, thereby preventing degradation mediated by the aspartic acid residue. In this paper, we compared the solution stability of a linear peptide (Arg-Gly-Asp-Phe-OH; 1) and a cyclic peptide (cyclo-(1, 6)-Ac-Cys-Arg-Gly-Asp-Phe-Pen-NH2; 2) as a function of pH and buffer concentration. The decomposition of both peptides was studied in buffers ranging from pH 2-12 at 50 degrees C. Reversed-phase HPLC was used as the main tool in determining the degradation rates and pathways of both peptides. Fast atom bombardment mass spectrometry (FAB-MS), electrospray ionization mass spectrometry (ESI-MS), matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry, liquid chromatography-mass spectrometry (LC-MS), and one- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) were used to characterize peptides 1 and 2 and their degradation products. In addition, co-elution with authentic samples was used to identify degradation products. Both peptides displayed pseudo-first-order kinetics at all pH values studied. The cyclic peptide 2 appeared to be 30-fold more stable than the linear peptide 1 at pH 7. The degradation mechanisms of linear (1) and cyclic (2) peptides primarily involved the aspartic acid residue. However, above pH 8 the stability of the cyclic peptide decreased dramatically due to disulphide bond degradation. Both peptides also exhibited a change in degradation mechanism upon an increase in pH. The increase in stability of cyclic peptide 2 compared to linear peptide 1, especially at neutral pH, may be due to decreased structural flexibility imposed by the ring. This rigidity would prevent the Asp side chain carboxylic acid from orientating itself in the appropriate position for attack on the peptide backbone.

Noninvasive monitoring of early antiangiogenic therapy response in human nasopharyngeal carcinoma xenograft model using MRI with RGD-conjugated ultrasmall superparamagnetic iron oxide nanoparticles

“…Moreover, the cyclic RGD peptide is commercially available and its stability is 30-fold higher than linear peptide. 29 In addition, these RGD-PAA-USPIO nanoparticles have well-controlled size, high negative relaxivities, and the preparation process is simple and low energy consuming, making it an attractive targeted contrast agent for MRI and potentially suited for clinical translation.…”

Molecular magnetic resonance imaging of activated hepatic stellate cells with ultrasmall superparamagnetic iron oxide targeting integrin αvβ3 for staging liver fibrosis in rat model

“…To enhance binding affinity, we used the cyclic RGD peptide (c (RGDyK)), which has been reported to provide 30-fold higher stability in comparison with conventional linear peptide. 36 In addition, after incubating with RGD-USPIO, HSC-T6 took up iron particles at an early incubation time of 20 minutes, and there was significant increase in the accumulation of iron particles along with incubation time. However, the naked USPIO accumulated in the cells remained at the lower level even after incubation of 3 hours.…”

A review of RGD-functionalized nonviral gene delivery vectors for cancer therapy

“…21 The improved binding properties of cyclic RGD peptides arise from structural rigidity. 22 RGD peptides contain an aspartic acid residue, which is highly susceptible to chemical degradation through intramolecular reactions in peptides, leading to the loss of biological functions. 23,24 The structural rigidity conferred by cyclization prevents the chemical degradation and, consequently, increases the stability of cyclic RGD peptides.…”

“…However, linear RGD peptides are highly susceptible to chemical degradation, which results in the reduction of binding with integrins. 22 GENE DELIVERY VECTORS Among various considerations for the development of gene therapy techniques that can fulfill the requirements of current demands, the lack of safe and efficient gene delivery vectors is a bottleneck by far. Although viral vectors promise an excellent performance in both high efficiency of transfection and great protection of therapeutic genes, safety concerns associated with severe immune and inflammatory responses are the primary obstacle to their clinical application.…”