Recent advances in the synthesis of metal nanoparticles (NPs) have led to tremendous expansion of their potential applications in different fields, ranging from healthcare research to microelectronics and food packaging. Among the approaches for exploiting nanotechnology in medicine, gold nanomaterials in particular have been found as the most promising due to their unique advantages, such as in sensing, image enhancement, and as delivery agents. Although, the first scientific article on gold nanoparticles was presented in 1857 by Faraday, during the last few years, the progress in manufacturing these nanomaterials has taken an enormous step forward. Due to the nanoscale counterparts of gold, which exhibit distinct properties and functionality compared to bulk material, gold nanoparticles stand out, in particular, in therapy, imaging, detection, diagnostics, and precise drug delivery. This review summarizes the current state-of-the-art knowledge in terms of biomedical applications of gold nanoparticles. The application of AuNPs in the following aspects are discussed: (i) imaging and diagnosing of specific target; (ii) treatment and therapies using AuNPs; and (iii) drug delivery systems with gold nanomaterials as a carrier. Among the different approaches in medical imaging, here we either consider AuNPs as a contrast agent in computed tomography (CT), or as a particle used in optical imaging, instead of fluorophores. Moreover, their nontoxic feature, compared to the gadolinium-based contrast agents used in magnetic resonance imaging, are shown. The tunable size, shape, and functionality of gold nanoparticles make them great carriers for targeted delivery. Therefore, here, we summarize gold-based nanodrugs that are FDA approved. Finally, various approaches to treat the specific diseases using AuNPs are discussed, i.e., photothermal or photodynamic therapy, and immunotherapy.

The study focuses on the synthesis of Fe₃O₄@SiO₂-NH₂-Au heterostructures with magneto-plasmonic properties composed of well-defined cubic Fe₃O₄ cores (79 nm) covered with 10 nm silica shell and gold nanoparticles (8 nm) fabricated on silica shell. The surface-anchored MHDA (16-mercaptohexadecanoic acid) linker facilitated cellulase bioconjugation, which was confirmed through Raman spectroscopy. The presence of gold nanoparticle islands on the heterostructure enabled surface-enhanced Raman scattering (SERS), demonstrating the potential for bioactive substance identification. Immobilization of cellulase allowed for pH enhancement and enzyme thermal stability. The optimal pH shifted from 4.0 (free enzyme) to 6.0 while thermal stability increased by 20 °C. The immobilized cellulase kept its 49% activity after five hydrolysis cycles, compared to significantly lower activity for free cellulase. The proposed heterostructures for cellulase immobilization demonstrate potential for practical applications.