Penetratin-Conjugated Gold Nanoparticles − Design of Cell-Penetrating Nanomarkers by Femtosecond Laser Ablation

Abstract

Gold nanoparticles (AuNPs) are promising imaging agents for the long-term visualization and tracing of intracellular functions because they bear outstanding optical properties and are fairly easily bioconjugated. However, the design of such multifunctional nanosystems might be limited by their bioavailability. Cell-penetrating peptides (CPPs) have been shown to be efficient molecular transporters with very few indices of cytotoxicity also in conjunction with nanoparticles. In this context, the current work aims to explore the approach of in situ conjugation during laser ablation in liquids for the design of CPP-NP conjugates at the example of penetratin-conjugated AuNPs. Because penetratin is positively charged at neutral pH, the conjugation process most likely differs from the previously reported coupling of oligonucleotides with their negatively charged phosphate backbone. Results reveal that penetratin is more efficiently bound to AuNPs, increasing the pH value of the ablation media, whereas the size and morphology of the bioconjugates function in terms of the penetratin concentration during the laser process. Probable underlying processes such as size quenching, aggregation, and laser-induced partial melting are assessed by the means of transmission electron microscopy and UV-vis spectroscopy. In a preliminary biological study, laser scanning confocal and transmission electron microscopy revealed a successful uptake of penetratinconjugated AuNPs for the first time in up to 100% of coincubated cells within 2 h.

Interaction of colloidal nanoparticles with their local environment: the (ionic) nanoenvironment around nanoparticles is different from bulk and determines the physico-chemical properties of the nanoparticles

“…Naturally, in these samples, more protons are necessary for charge compensation, and the isoelectric point is reached at a more acidic pH. Completely different results were obtained by Petersen et al [119] where a pI of 4.5 was found. These deviations may be due to the fact that a system of CH 3 COOH/NH 3 was used for pH adjustment.…”

“…These findings seem to indicate that ligand-free gold NPs work as a buffer in highly diluted electrolytes, totally stabilizing the pH at 6.5 up to a proton surplus, as well as a proton deficiency of 30 mM. Apparently, the nanoenvironment of the Petersen et al [119] (ammonium-acetate buffer) Sylvestre et al [103] (10 mM NaCl) rsif.royalsocietypublishing.org J. R. Soc. Interface 11: 20130931…”

Gold nanoparticles prepared by laser ablation in aqueous biocompatible solutions: assessment of safety and biological identity for nanomedicine applications

“…32 For instance, due to the presence of some higher oxidation states at high pH, they can possess O − functionalization, making hydrogen bonding interactions possible. 29,32 Au-NPs can thus be noncovalently conjugated to oligosaccharides, 32,33 polymers, 34 proteins, 35 and oligonucleotides. 36 Such direct conjugation (without any group ligand-specific binding) promotes those Au-NPs as novel classes of biocompatible materials for various biological applications that have been underdeveloped or not fully investigated.…”

“…Taylor et al 38 explored the cell uptake of Au-NPs in an immortalized bovine endothelial cell line. It was also shown that NP coating with cell-penetrating peptides 35 or thermoresponsive polymers 39 can facilitate cell penetration without cytotoxicity. Those scarce reports are thus preliminary examples of promising in vitro applications with laser-synthesized Au-NPs.…”

Sex selection of sperm in farm animals: status report and developmental prospects

“…Nevertheless, successful internalisation depended strongly on the cargo itself as well as on peptide concentration (Stewart et al 2008, Mandal et al 2009). Some of them, such as penetratin, led to a tremendously enhanced uptake of AuNPs, but only into endosomes (Petersen et al 2011). However, modification of AuNPs with Tat peptide, derived from the human immunodeficiency virus type-1, and also with a peptide named nucleus localisation signal caused the particles to directly enter into the cytosol and even into the nucleus (Tkachenko et al 2004, de la Fuente & Berry 2005, Berry et al 2007.…”