Probing gold nanoparticles/highly modified nucleosides interaction by capillary electrophoresis

Nanoparticles (NPs) are being employed in many different fields such as drug carriers, imaging agents and analytical probes, due to their unique physico-chemical properties. With the growing of nanotechnology applications in research and industry, the release of nanomaterials into the environment could increase; therefore, ecotoxicological effects of NPs are rising concerns. Investigations on molecule/nanoparticle interactions play a key role in both the determination of NP’s biocompatibility for various biomedical applications and for nanosafety evaluation (1). Moreover, these studies can also find application in sample pre-treatment and pre-concentration, in such cases NPs are employed as adsorbent material (2). The aim of the present work was to evaluate the interaction between modified nucleosides and gold nanoparticles (AuNPs), and to investigate the applicability of these NPs in Solid-Phase Nano- Extraction (SPNE) systems. The application of AuNPs as adsorbent media is a rapidly expanding application because their inherent properties make them a very promising tool. In fact, controlled fabrication in a wide dimensional range (1–150 nm) with limited size dispersity has been established. Moreover, AuNP surface can adsorb multiple targeting agents and/or therapeutics. Finally, the core in essence is non-toxic, biocompatible and inert (3). The nucleoside/AuNP system was studied by using Capillary Electrophoresis (CE), since it has been demonstrated that this technique is a powerful tool to investigate bio-physical and kinetic parameters of interactions between nanoparticles and compounds with biological activity (proteins, nucleotides, DNA, drugs, etc. ...). In particular, we examined the effectiveness of CE in measuring the affinity between AuNPs and three highly modified nucleosides (Figure 1): this class of compounds includes a large number of molecules obtained from parent nucleosides. The increased interest in the synthesis of new modified nucleosides is linked to their pharmacological activity as antibiotic, antiviral and/or antitumoral drugs. From the experimental data, the adsorption isotherm was calculated: AuNPs showed an high saturation capacity for nucleoside C). Release experiments were carried out by varying both the buffer composition and the surfactant concentration of the medium. A recovery in the range 100-110% for different concentration levels of nucleoside C) was obtained. Therefore, by employing AuNPs as adsorbent mean in Solid Phase Nano Extraction (SPNE), an enrichment factor of 7 was attained. Finally, by combining SPNE with sample injection in Reversed Electrode Polarity Stacking Mode (REPSM) which leads to a sample preconcentration inside the capillary (4), an enrichment factor of about 50 was achieved. Furthermore, AuNPs could be used in multiple adsorption/release experiments because, after total release of the analyte, their adsorption capacity is fully maintained.