Charge‐Neutral, Stable, Non‐Cytotoxic, Near‐Infrared SnS Aqueous Quantum Dots for High Signal‐to‐Noise‐Ratio Biomedical Imaging

Abstract

We have synthesized charge-neutral, stable, non-cytotoxic, bright, near-infrared (NIR) SnS quantum dots (QDs) by first making Cysteamine-capped SnS QDs in glycerol under acidic conditions followed by lengthening the capping molecule with peptide bonds by reacting the capping molecules with glycine and subsequent heat treatment at 200°C for 4 hours. The obtained stable SnS QDs exhibited a band gap of 1.5 eV and a strong, narrow NIR emission peak at 830 nm with a quantum yield of 4.6%. The suspension could be stable for more than 1 month without aggregation or emission decay. The positively charged SnS QDs were further neutralized by 3-mercaptoproprionic acid (MPA) through electrostatic attraction. The MPA neutralized SnS QDs were shown to be non-cytotoxic at concentrations 6 times the typical QDs concentration for immunostaining. Low-noise, optimal NIR immunofluorescent imaging of vascular endothelial growth factor (VEGF) on 3T3 cells and Tn antigen on HT29 cells was achieved by using streptavidin (SA)-linked MPA-neutralized SnS QDs with a SA:QD molar ratio of 22:1 to bind to biotinylated secondary antibody bound on the primary antibody that was bound on the targeted antigen on the cell membrane with a high signal-to noise ratio (SNR) of 35.

Real‐Time Dissection of the Transportation and miRNA‐Release Dynamics of Small Extracellular Vesicles

“…[ 31 ] Real‐time high‐resolution single particle tracking of sEVs makes strict demands on the QD‐based labeling strategy. Even though the accumulation of multiple QDs could directly improve imaging quality by increasing signal intensity and signal‐to‐noise ratio, [ 32 ] too many QDs on the membrane surface of sEVs would potentially cause undesirable effects on their biological behaviors. That means, the ideal labeling strategy of sEVs based on QDs should focus on balancing the contradiction caused by the number of QDs between image quality and external interference.…”

The Effect of (3‐Mercaptopropyl)trimethoxysilane (MPS) Coating on the Genetic Detection Performance of Quartz Crystal Microbalance‐Dissipation (QCM‐D) Biosensor: Novel Intact Double‐Layered Surface Modification on QCM‐D

“…In biosensor researches, the main criterion showing that the signal is significant is that the SNR information is greater than 3. [28] Also, another indicator of whether the signal is significant is a statistically verified determination. [29] When the findings we obtained in the study were compared, there was a statistically significant difference between the negative control (0 copy/mL of tDNA) and the solution containing 10 8 copies/ml of tDNA.…”

Nanoengineering of Tin Monosulfide (SnS)‐Based Structures for Emerging Applications

“…In recent years, metal sulfides have received extensive attention in biomedical applications due to their fascinating properties, such as low-cost, suitable bandgap, environmentally high stability, etc. [24,26,203,[259][260][261][262][263][264] SnS is also biocompatible and nontoxic due to its poor absorption by human body and rapid excretion in faeces. [203,265] Up to now, 0D SnS QDs, 2D SnS NSs, and triangular SnS nanopyramids were used in biomedical applications such as photothermal therapy, chemo-therapy agents, and photoacoustic imaging.…”

“…[203,265] Up to now, 0D SnS QDs, 2D SnS NSs, and triangular SnS nanopyramids were used in biomedical applications such as photothermal therapy, chemo-therapy agents, and photoacoustic imaging. [24,26,203] In 2018, our group used 2D SnS NSsbased dual therapy nanoplatforms to achieve excellent tumor therapy by a combination of photothermal-and chemotherapy. [203] The 2D SnS NSs were successfully fabricated by a LPE method and were then functionalized with positively charged poly(ethylene glycol) amine (PEG-NH 2 ) by electrostatic interaction, which was characterized by TEM image with apparent halo coating of PEG on the surface of the 2D SnS NSs (Figure 26a).…”

“…Among Sn-X (X ¼ S, Se, Te) compounds, tin monosulfide (SnS) as a typical black phosphorus analogue, has also received intensive scientific attention due to its unique properties, such as inexpensive, sustainable, suitable bandgap between Si (1.12 eV) and GaAs (1.43 eV), [17] high absorption coefficient (10 À4 cm À1 ), [18] strong mechanical properties, and anisotropic optoelectronic, [19][20][21] which are of great value in optoelectronics, catalysis, sensors, and nanomedicines. [7,[22][23][24][25][26][27] In addition, layered SnS with suitable spacing structures hold promising potentials in the field of lithium (Li)-ion batteries and sodium (Na)-ion batteries due to their relatively high electrical conductivity and theoretical capacity. [28][29][30][31][32] However, although popular SnS has achieved great progress in a variety of fields, few comprehensive reviews have hitherto focused on the field of SnS-based nanostructures and their fascinating applications.Inspired by important reviews on SnSe reported by Chen [14] and Li [8] in recent years, we comprehensively summarized the synthesis, characterization, and the latest progress of SnS-based nanostructures, as shown in Figure 1.…”