Research Article
KDEL peptide gold nanoconstructs: promising nanoplatforms for drug delivery

https://doi.org/10.1016/j.nano.2012.09.002Get rights and content

Abstract

Gold nanoparticles (AuNPs) have been widely investigated as potential nanocarriers for drug delivery. In the present study, AuNPs were conjugated to a peptide that has a C-terminal Lys–Asp–Glu–Leu (KDEL) motif. In a pulse-chase study, time-course sampling revealed that AuNP-delivered KDEL peptides were rapidly localized to the endoplasmic reticulum (ER) in 5 to 15 min, and after 1 h the majority of peptides were localized to the ER. Clathrin-coated vesicles and Golgi apparatus were also involved during the intracellular trafficking of KDEL peptide gold (AuNP-KDEL) nanoconstructs. Furthermore, overexpression of KDEL receptor (KDELR) significantly enhanced KDEL peptide uptake in both free and AuNP-conjugated forms. These data indicate that the AuNP-KDEL nanoconstructs are internalized via a clathrin-mediated pathway and trafficked to the ER via a retrograde transport pathway, bypassing the lysosomal degradation pathway. Thus, this novel approach to development of nanoconstruct-based drug delivery has the potential to evade intracellular degradation, enhancing drug efficacy.

From the Clinical Editor

In this study, gold nanoparticles were conjugated to a peptide with KDEL motif, resulting in internalization via a clathrin-mediated pathway and trafficking to the ER via retrograde transport meanwhile bypassing the lysosomal degradation pathway. This method results in a potential evasion of intracellular degradation, and enhanced drug efficacy.

Graphical Abstract

Nanoconstructs may be internalized via several known endocytosis pathways including macropinocytosis, clathrin-mediated, caveolae-mediated pathway or non-specific pathway such as membrane adsorption. Once the nanoconstructs enter the cells, they will be transported through different subcellular compartments. Our studies showed that a clathrin-mediated pathway is predominant during the internalization of Lys–Asp–Glu–Leu (KDEL) peptide gold nanoconstructs and these nanoconstructs are transported to the endoplasmic reticulum via a retrograde pathway mediated by coat protein I (COPI). Overall, the KDEL peptide gold nanoconstructs have potential as a nanoplatform for high efficacy drug delivery.

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Section snippets

Preparation of peptide gold nanoconstructs

The structure and conjugation procedures used with the KDEL peptide in the present studies are described in detail in our previous publication.14 Briefly, AuNP-KDEL nanoconstructs were prepared using 1078 molar equivalents of KDEL peptide relative to 20 nm Au NP, as reported previously.14

Cell culture

Sol8 myogenic cells (ATCC, Manassas, VA) were maintained in 5% CO2 at 37 °C in Dulbecco's modified Eagle medium (DMEM) supplemented with 10% FBS (Life Technologies, Grand Island, NY) and penicillin (100 

Intracellular trafficking of KDEL peptide gold nanoconstructs

A pulse-chase study was conducted to investigate the intracellular trafficking of KDEL peptide gold (AuNP-KDEL) nanoconstructs. Figure 2 shows the colocalization images of internalized free KDEL peptide and AuNP-delivered KDEL peptides with three cellular compartments: clathrin-coated vesicles, Golgi apparatus and ER. Quantification of colocalization levels of the peptide within each cellular compartment is shown in Figure 3. The analysis shows that both free KDEL peptide and AuNP-KDEL

Discussion

Targeted drug delivery is very important for the efficacy, safety and cost of treatment. One approach is to target the drug by linking specific ligands enabling cellular internalization by a particular cell type via receptor-mediated endocytic pathways. Strategies for targeted drug delivery to subcellular compartments were well reviewed by Rajendran et al.44 Although currently cell-penetrating peptides (CPPs) have shown advantages to facilitate drug delivery into nuclei or mitochondria,45 the

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    No conflict of interest was reported by the authors of this paper.

    This work was supported by the University of Idaho Blue Ribbon BANTech initiative.

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