# Conjugation of Functionalized Gold Nanorods and Copper (I)-Based Drug: An Anisotropic Nano Drug Delivery System

## TL;DR

This paper describes a new drug delivery system using gold nanorods to carry copper-based drugs, which are stable, biocompatible, and effective for potential medical applications.

## Contribution

The novel contribution is the development of an anisotropic nano drug delivery system using functionalized gold nanorods conjugated with copper(I)-based drugs.

## Key findings

- AuNRs showed strong hydrophilicity and stability in water for up to 3 months.
- The drug loading efficiency reached 50 ± 7% with non-covalent interactions confirmed by multiple spectroscopic techniques.
- AuNRs and their conjugates were biocompatible with Vero E6 cells, showing no significant toxicity under normal conditions.

## Abstract

Gold nanorods (AuNRs) were synthesized and optimized with the aim of obtaining strongly hydrophilic nanomaterials, suitable as a drug delivery system (DDS) for copper-based drugs. After careful purification, AuNRs were characterized by ultraviolet–visible–near-infrared spectroscopy (UV–Vis–NIR), showing two typical localized surface plasmon resonance (LSPR) bands in the range 550–750 nm. Fourier Transform Infrared (FT-IR) and high-resolution X-ray photoelectron (HR-XPS) spectroscopies verified the surface functionalization. Transmission electron microscopy (TEM) showed AuNRs with regular shape and size, with an aspect ratio (AR) of 2.6. Dynamic Light Scattering (DLS) measurements confirmed the size and the stability in water for up to 3 months. The AuNRs were conjugated with copper(I) drugs, i.e., [Cu(PTA)4]BF4 (PTA = 1,3,5-triaza-7-phosphadamantane). The drug loading procedures and efficiency were optimized, and the best loading was η (%) = 50 ± 7%. The non-covalent interactions of the Cu(I) complex with the AuNRs were studied by means of UV–Vis–NIR, ζ-potential, HR-TEM, FT-IR, synchrotron radiation-induced X-ray photoelectron (SR-XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. The MTT assay performed on Vero E6 cells showed that AuNRs and AuNR-Cu(I) conjugates had no significant effect on cell viability, being biocompatible, causing a reduction in cell viability only after prolonged exposure.