Gold Nanoparticles Stabilize Peptide-Drug-Conjugates for Sustained Targeted Drug Delivery to Cancer Cells

Michael Firer, Chemical Engineering, Ariel University, Ariel, Israel
Kalishwaralal Kalimuthu, Chemical Engineering, Ariel University, Ariel, Israel
Galia Luboshits, Chemical Engineering, Ariel University, Ariel, Israel

Peptide-drug-conjugates (PDCs) are being developed as an effective strategy to specifically deliver cytotoxic drugs to cancer cells. However one of the challenges to their successful application is the relatively low stability of peptides in the blood, liver and kidneys. One approach to overcoming this problem would be to conjugate the PDCs to Gold nanoparticles (AuNPs), as these have favorable physico-chemical and safety properties for drug delivery systems. We tested whether Polyethylene-Glycol (PEG) coated-AuNPs could provide a suitable platform for the non-covalent loading of pre-formed PDCs and whether this modification would affect the bioavailability of the PDCs and their cytotoxicity toward target cancer cells. Peptides specifically internalized by A20 murine lymphoma cells were isolated from a phage library displaying 7mer linear peptides. PDCs were synthesized containing a selected peptide (P4) and either chlorambucil (Chlor), melphalan (Melph) or Bendamustine (Bend). Gold nanoparticles were sequentially coated with citrate, PEG-6000 and then PDC (PDC-PEG-AuNP). The physico-chemical properties of the coated particles were analyzed by electrophoresis, TEM, UV–VIS and FTIR. Stability of free and PDC-coated AuNP was determined. All three PDCs specifically killed A20 target cells, however they had short half-lives ranging from 10.6 to 15.4 min. When coated to PEG-AuNPs, the half-lives were extended to 21.0–22.3 h. The PDC-PEG-AuNPs retained cytotoxicity towards the target cells. Moreover, whereas pre-incubation for 24 h of free PDCs almost completely abolished their cytotoxic activity, the PDC-PEGAuNPs were still active even after 72 h pre-incubation. The results suggest that while PDCs hold potential for improving the target efficacy of chemotherapeutic drugs, their short half-lives may limit their application. This hurdle can be overcome by easily conjugating them to gold nanoparticles. This conjugation also opens up the possibility of developing slow release formulations of targeted drug delivery systems containing PDCs.

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