Surface Engineering of Gold Nanorods for Cytochrome c Bioconjugation: An Effective Strategy To Preserve the Protein Structure

Abstract

The surface of gold nanorods (Au NRs) has been appropriately engineered to achieve a suitable interface for bioconjugation with horse heart cytochrome c (HCc). HCc, an extensively studied and well-characterized protein, represents an ideal model for nanoparticle (NP)–protein conjugation studies because of its small size, high stability, and commercial availability. Here, the native state of the protein has been demonstrated for the first time, by means of Raman spectroscopy, to be retained upon conjugation with the anisotropic Au nanostructures, thus validating the proposed protocol as specifically suited to mostly preserve the plasmonic properties of the NRs and to retain the structure of the protein. The successful creation of such bioconjugates with the retention of the protein structure and function along with the preservation of the NP properties represents a challenging but essential task, as it provides the only way to access functional hybrid systems with potential applications in biotechnology, medicine, and catalysis. In this perspective, the organic capping surrounding the Au NRs plays a key role, as it represents the functional interface for the conjugation step. Cetyltrimethylammonium bromide-coated Au NRs, prepared by using a seed-mediated synthetic route, have been wrapped with polyacrylic acid (PAA) by means of electrostatic interactions following a layer-by-layer approach. The resulting water-dispersible negatively charged AuNRs@PAA NPs have then been electrostatically bound to the positively charged HCc. The bioconjugation procedure has been thoroughly monitored by the combined analysis of UV–vis absorption, resonance Raman and Fourier transform infrared spectroscopies, transmission electron microscopy microscopy, and ζ-potential, which verified the successful conjugation of the protein to the nanorods.

Engineered Gold-Based Nanomaterials: Morphologies and Functionalities in Biomedical Applications. A Mini Review

“…This review shows the advantages and disadvantages of the different morphologies, considering the dimension, functionalization and bioapplication. In this regard, in the wide biomedicine field, four main areas of applications are typically identified: therapy, diagnostics, drug/gene delivery, and sensors, as schematically shown in Figure 2 [4,8,10,12,16,17,18,21,28,29,30,31,32,33,34,37,38,39,48,51,53,70,71,72,75,76,77,78,79,80,81,82,83,84,85,90,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,…”

“…For example, AuNRs can now be organized in arrays by using oligonucleotides as superficial ligands (see Figure 4). Furthermore, dendrimers and poly(ethylene glycol) (PEG), can be used to substitute CTAB on the AuNRs’ surface, enhancing their biocompatibility, or magnetic nanoparticles can coat their surface, giving magnetic traceability [31,155,156].…”

“…In the last decade, nanotechnology allowed for an improvement of materials properties in many application fields, such as sensing [1,2,3,4,5,6,7,8,9], optoelectronics [10,11,12,13,14,15], energy [16,17,18,19,20,21], catalysis [22,23,24] and biotechnology [25,26,27,28,29,30,31]. Gold was used to produce many different nanostructures through a bottom-up approach, such as spheres, rods, stars, cubes, hollow nanoparticles, and nanocapsules, widely used in biomedicine and reported in a schematic way in Figure 1.…”

Plasma Fabrication and SERS Functionality of Gold Crowned Silicon Submicrometer Pillars

“…Surface engineering techniques are increasingly spanning into the field of optics, allowing the design of intricate material configurations with photonic [1], luminescent [2], photochemical [3], plasmonic [4], photovoltaic [5], or even dual [6] properties. The engineering of these structures requires a sequential fabrication in which, most often, a plasma-processing step is involved.…”

Highly Hydrophilic Gold Nanoparticles as Carrier for Anticancer Copper(I) Complexes: Loading and Release Studies for Biomedical Applications

“…Moreover, AuNPs present optical properties, which can be easily tuned to desirable wavelengths according to their shape (e.g., nanoparticles, nanoshells, nanorods, etc. ), size (e.g., 1 to 100 nm) and composition (e.g., core/shell or alloy noble metals) [16,17,18,19,20], enabling their imaging and photothermal applications [21,22,23,24,25,26]. AuNPs can also be easily functionalized with different moieties, such as antibodies, peptides and/or DNA/RNA to specifically target different cells [10,27,28], and with biocompatible molecules to prolong their in vivo circulation for drug delivery applications [29,30].…”