Luminescent Gold Nanoclusters for Bioimaging: Increasing the Ligand Complexity

Abstract

Fluorescence, and more in general, photoluminescence (PL), presents important advantages for imaging with respect to other diagnostic techniques. In particular, detection methodologies exploiting fluorescence imaging are fast and versatile; make use of low-cost and simple instrumentations; and are taking advantage of newly developed powerful, low-cost, light-based electronic devices, such as light sources and cameras, used in huge market applications, such as civil illumination, computers, and cellular phones. Besides the aforementioned simplicity, fluorescence imaging offers a spatial and temporal resolution that can hardly be achieved with alternative methods. However, the two main limitations of fluorescence imaging for bio-application are still (i) the biological tissue transparency and autofluorescence and (ii) the biocompatibility of the contrast agents. Luminescent gold nanoclusters (AuNCs), if properly designed, combine high biocompatibility with PL in the near-infrared region (NIR), where the biological tissues exhibit higher transparency and negligible autofluorescence. However, the stabilization of these AuNCs requires the use of specific ligands that also affect their PL properties. The nature of the ligand plays a fundamental role in the development and sequential application of PL AuNCs as probes for bioimaging. Considering the importance of this, in this review, the most relevant and recent papers on AuNCs-based bioimaging are presented and discussed highlighting the different functionalities achieved by increasing the complexity of the ligand structure.

Effect of Size, Shape and Surface Functionalization on the Antibacterial Activity of Silver Nanoparticles

“…In the last 15 years, researchers have deeply investigated the properties of nanoparticles for biomedical applications [17]; these can be metallic nanoparticles [18], such as silver and zinc [19], as well as metalloids [20], and even organic/inorganic compounds. [21,22] Indeed, due to their size, nanoparticles can be internalized in cells via mechanisms that are different with respect to small molecules [23], and that can change based on the physiochemical parameters of the nanoparticles [24][25][26][27].…”

Nanotechnology’s frontier in combatting infectious and inflammatory diseases: prevention and treatment

“… 712 – 714 For example, the combination of AuNPs with fluorescence detection can expand the detection range and improve specificity. 715 A dual-mode detection method (colorimetric-fluorescence) combining PCR has been designed to achieve rapid and sensitive detection of Salmonella. 716 CRISPR-based detection systems, such as SHERLOCK, DETECTR, and STOPCovid, are becoming important emerging tools for viral detection due to their speed, specificity, and ease of use.…”

Metal Nanoclusters in Point-of-Care Sensing and Biosensing Applications

“…AuNCs comprise a few to hundreds of gold atoms with a diameter of less than 5 nm. 87 These nanostructures have attracted worldwide attention in various biomedical applications because of their supernormal physicochemical features and excellent biocompatibility. At this small scale, the continuous energy states are divided into separate states due to the intense quantum effect of electrons.…”

“…Reducing its size and shape results in unique properties far different from bulk counterparts. AuNCs comprise a few to hundreds of gold atoms with a diameter of less than 5 nm . These nanostructures have attracted worldwide attention in various biomedical applications because of their supernormal physicochemical features and excellent biocompatibility.…”