RGD-Targeted Liposome Binding and Uptake on Breast Cancer Cells Is Dependent on Elastin Linker Secondary Structure

Abstract

The linker between the targeting moiety and the nanoparticle is often overlooked when engineering targeted drug delivery vehicles. We hypothesized that pH-triggered conformational changes of an elastin-like peptide (ELP) linker, with repeating VPGVG sequences, could alter the binding affinity of the well-established targeting moiety arginine-glycine-aspartic acid (RGD), which is known to enhance the delivery of nanoparticles to tumor cells via integrin overexpression. The pH change from blood (pH 7.4) to the tumor environment (pH 6) was used to elicit a conformational change in the ELP linker, as described by circular dichroism. Atomic force microscopy confirmed that RGD-ELP resulted in stronger adhesion to both MDA-MB-231 and HCC1806 breast cancer cells at pH 6 relative to pH 7.4. No change in adhesion force was measured as a function of pH for the non-neoplastic MCF-10A cell line and the nontargeting GDR-ELP peptide. This translated to significant binding and uptake of RGD-ELP modified liposomes at pH 6.0 relative to pH 7.4. These results indicate that the pH-triggered conformational structure of the ELP linker shifts RGD-mediated cancer cell targeting from non-active (pH 7.4) to active (pH 6). The reversible shift in ELP secondary structure may be used to engineer targeted drug delivery vehicles with tunable uptake.

Recent advances on liposomal nanoparticles: synthesis, characterization and biomedical applications

“…Sonication is maybe the most widely applied method for the preparation of liposomes and nanoliposomes. Sonication is a simple technique for dropping the size of liposomes and production of nanoliposomes (Veneti et al 2016, Eatemadi et al 2016). There are some disadvantages for this method such as very low internal volume/encapsulation efficiency, removal of large molecules and metal pollution from probe tip (Yu and Tang 2016).…”

Peptide-Based Cancer-Targeted DDS and Molecular Imaging

“…Since the ELP linker showed conformational change in an acidic tumor microenvironment, the liposome-modified RGD-ELP linker significantly recognized both MDA-MB-231 and HCC1806 breast cancer cells. 109) These findings indicate that spacer peptides contribute to the efficacy of peptide-ligand-mediated active targeting.…”

“…Compared with PEGylated liposomes using PEG spacers, the combination of liposomal PEG350 and EG12 spacer dramatically improved its accumulation by 9-and 100-fold in breast cancer and multiple myeloma cells, respectively. 108) As another linker, Veneti et al 109) reported an elastin-like peptide (ELP) linker for RGD-targeted liposomes. Since the ELP linker showed conformational change in an acidic tumor microenvironment, the liposome-modified RGD-ELP linker significantly recognized both MDA-MB-231 and HCC1806 breast cancer cells.…”

Engineering the Architecture of Elastin‐Like Polypeptides: From Unimers to Hierarchical Self‐Assembly

“…[182][183][184][185][186][187][188][189][190][191] Recently, thermoresponsive ELP-liposomes have gained attention for their ability to allow release of drugs when exposed to mild hyperthermia. [163][164][165][166][167]192] Due to the hydrophobicity of the lipid bilayer, ELPs in ELP-liposomes have been modified with either a reactive group to decorate the hydrophilic head group of the liposomes that is exposed to aqueous solution, [163,164] or a lipid moiety to anchor the ELPs into the lipid bilayer. [165][166][167] The T t of the ELPs has been tuned to ≈40°C to match the temperature suitable for mild clinical hyperthermia of tissues.…”