A. Sangtani, E. Petryayeva, M. Wu, K. Susumu, E. Oh, A.L. Huston, G. Lasarte-Aragonés, I.L. Medintz, W.R. Algar, J.B. Delehanty
US Naval Research Laboratory,
Keywords: quantum dot, peptide mediated delivery, doxorubicin
Summary:Nanoparticle (NP)-mediated drug delivery offers many potential benefits over the traditional systemic delivery of therapeutic drug compounds including the ability to achieve specific targeting and controlled release of the NP-associated drug cargo. These advantages have clear implications for the industrial production of novel NP-based therapeutics. Doxorubicin (DOX) is a widely used FDA-approved cancer therapeutic that has been shown to have great potential for tumor treatment. However, DOX is dose-limited due to the fact that it is known to cause a multitude of side effects including cardiac toxicity. Thus, there is significant interest in modulating the efficacy of the drug. Here, we employ a quantum dot (QD) as a central scaffold to conjugate DOX via three different peptidyl linkages (ester, disulfide, hydrazone) that are responsive to enzymatic cleavage, reducing conditions and low pH, respectively. The QD-[peptide-DOX] complex is delivered to cells via facilitated uptake by appending a polyarginine-displaying cell penetrating peptide (CPP) to the QD surface which results in the introduction of the QD-[peptide-DOX]-CPP complex into the endocytic pathway. The assembly of both the DOX-conjugated peptides and the CPP is driven by polyhistidine-mediated metal affinity. This allows fine control of the number of copies or “valence” of the peptide in the assembly. Importantly, this allows for the fine control of the eventual DOX dose delivered to cells by simply varying the number of copies of DOX-conjugated peptide that is assembled onto the QD surface. Microplate-based Förster resonance energy transfer assays confirmed the successful ratiometric assembly of the conjugates. Cell delivery experiments were performed to track the residence of the QD-[peptide-DOX]-CPP complexes in the endocytic pathway over time and distinct differences amongst the various DOX-peptide conjugates are noted. Cytotoxicity assays confirm the augmented cell killing of the QD-[peptide-DOX]-CPP conjugate when the DOX is attached via an ester linkage compared to a control peptide where the DOX is attached through an amide bond. Attachment of the DOX through hydrazone and disulfide linkages show intermediary cytotoxicity. We discuss our results in the context of the role played by various attachment chemistries used in QD-peptide-drug assemblies and their implications for the rationale design of nanoparticle-based constructs for drug delivery.