Chitosan capped CuInS2 and CuInS2/ZnS by wet stirred media milling: in vitro verification of their potential bio-imaging applications

Single-step synthesis of ternary metal chalcogenides (sf-CuInS2 and sf-CuInSe2) stripped off the organic cover and their use as a catalyst for symmetric Glaser-Hay coupling reactions

Generally, inorganic nano/microparticles produced by chemical routes are covered by organic surfactants or polymers to control their agglomeration during their synthesis. However, these surfactants and polymers negatively affect their catalytic activity because these molecules mask the surface. This work presents the synthesis of surfactant-free CuInS2 and CuInSe2 (sf-CuInS2 and sf-CuInSe2) nano/microparticles through simple reactions without surfactant or polymer coatings using LiBH4 under a thermodynamically favourable condition. These reactions are rare observations of a single-step process to produce ternary metal chalcogenides without any template assistance. We have also demonstrated efficient catalysis by sf-CuInS2 nanoparticles in the coupling reaction of substituted phenylacetylenes. We tested it as catalysts in dimerizing 1,3-diyne derivatives while using 8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base. These Glassar-Hay coupling reactions are conducted at room temperature in acetonitrile (4-7 h, depending on the substrate) using 10 mg of sf-CuInS2. The maximum yield obtained in these reactions is 97%, while the catalyst is reusable for five cycles with little difference in its ability to catalyse. The effectiveness of the catalyst is credited to the availability of a free catalytic surface.

Luminescent Quantum Dots: Synthesis, Optical Properties, Bioimaging and Toxicity

Luminescent nanomaterials such as semiconductor nanocrystals (NCs) and quantum dots (QDs) attract much attention to optical detectors, LEDs, photovoltaics, displays, biosensing, and bioimaging. These materials include metal chalcogenide QDs and metal halide perovskite NCs. Since the introduction of cadmium chalcogenide QDs to biolabeling and bioimaging, various metal nanoparticles (NPs), atomically precise metal nanoclusters, carbon QDs, graphene QDs, silicon QDs, and other chalcogenide QDs have been infiltrating the nano-bio interface as imaging and therapeutic agents. Nanobioconjugates prepared from luminescent QDs form a new class of imaging probes for cellular and in vivo imaging with single-molecule, super-resolution, and 3D resolutions. Surface modified and bioconjugated core-only and core-shell QDs of metal chalcogenides (MX; M = Cd/Pb/Hg/Ag, and X = S/Se/Te,), binary metal chalcogenides (MInX₂; M = Cu/Ag, and X = S/Se/Te), indium compounds (InAs and InP), metal NPs (Ag, Au, and Pt), pure or mixed precision nanoclusters (Ag, Au, Pt), carbon nanomaterials (graphene QDs, graphene nanosheets, carbon NPs, and nanodiamond), silica NPs, silicon QDs, etc. have become prevalent in biosensing, bioimaging, and phototherapy. While heavy metal-based QDs are limited to in vitro bioanalysis or clinical testing due to their potential metal ion-induced toxicity, carbon (nanodiamond and graphene) and silicon QDs, gold and silica nanoparticles, and metal nanoclusters continue their in vivo voyage towards clinical imaging and therapeutic applications. This review summarizes the synthesis, chemical modifications, optical properties, and bioimaging applications of semiconductor QDs with particular references to metal chalcogenide QDs and bimetallic chalcogenide QDs. Also, this review highlights the toxicity and pharmacokinetics of QD bioconjugates.

Mechanochemical Preparation, Characterization and Biological Activity of Stable CuS Nanosuspension Capped by Bovine Serum Albumin

The biocompatible nanosuspension of CuS nanoparticles (NPs) using bovine serum albumin (BSA) as a capping agent was prepared using a two-stage mechanochemical approach. CuS NPs were firstly synthetized by a high-energy planetary ball milling in 15 min by milling elemental precursors. The stability of nanoparticles in the simulated body fluids was studied, revealing zero copper concentration in the leachates, except simulated lung fluid (SLF, 0.015%) and simulated gastric fluid (SGF, 0.078%). Albumin sorption on CuS NPs was studied in static and dynamic modes showing a higher kinetic rate for the dynamic mode. The equilibrium state of adsorption was reached after 90 min with an adsorption capacity of 86 mg/g compared to the static mode when the capacity 59 mg/g was reached after 2 h. Then, a wet stirred media milling in a solution of BSA was introduced to yield the CuS-BSA nanosuspension, being stable for more than 10 months, as confirmed by photon cross-correlation spectroscopy. The fluorescent properties of the nanosuspension were confirmed by photoluminescence spectroscopy, which also showed that tryptophan present in the BSA could be closer to the binding site of CuS than the tyrosine residue. The biological activity was determined by in vitro tests on selected cancer and non-tumor cell lines. The results have shown that the CuS-BSA nanosuspension inhibits the metabolic activity of the cells as well as decreases their viability upon photothermal ablation.

Biocompatible CuInS2 Nanoparticles as Potential Antimicrobial, Antioxidant, and Cytotoxic Agents

A simple hydrothermal route is employed to synthesize pure copper indium disulfide (CIS) and CIS nanoparticles (NPs) mediated by various natural plant extracts. The plant extracts used to mediate are Azadirachta indica (neem), Ocimum sanctum (basil), Cocos nucifera (coconut), Aloe vera (aloe), and Curcuma longa (turmeric). The tetragonal unit cell structure of as-synthesized NPs is confirmed by X-ray diffraction. The analysis by energy-dispersive X-rays shows that all the samples are near-stoichiometric. The morphologies of the NPs are confirmed by high-resolution scanning and transmission modes of electron microscopy. The thermal stability of the synthesized NPs is determined by thermogravimetric analysis. The optical energy band gap is determined from the absorption spectra using Tauc's equation. The antimicrobial activity analysis and the estimation of the minimum inhibitory concentration (MIC) value of the samples are performed for Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Enterobacter aerogenes, and Staphylococcus aureus pathogens. It shows that the aloe-mediated CIS NPs possess a broad inhibitory spectrum. The best inhibitory effect is observed against S. aureus, whereas the least effect was exhibited against P. vulgaris. The least MIC value is found for aloe-mediated CIS NPs (0.300 mg/mL) against S. aureus, P. aeruginosa, and E. aerogenes, along with basil-mediated NPs against E. coli. The antioxidant activity study showed that the IC₅₀ value to inhibit the scavenging activity is maximum for the control (vitamin C) and minimum for pure CIS NPs. The in vivo cytotoxicity study using brine shrimp eggs shows that the pure CIS NPs are more lethal to brine shrimp than the natural extract-mediated CIS NPs. The in vitro cytotoxicity study using the human lung carcinoma cell line (A549) shows that the IC₅₀ value of turmeric extract-mediated CIS NPs is minimum (15.62 ± 1.58 μg/mL). This observation reveals that turmeric extract-mediated CIS NPs are the most potent in terms of cytotoxicity toward the A549 cell line.

Assaying of Cu2+ with near-infrared l-cysteine-capped CdSeTe/CdS quantum dots and its effect on cell imaging

Near-infrared (NIR) core-shell CdSeTe/CdS quantum dots (QDs) modified with l-cysteine were synthesized in aqueous solution. The QDs had a special NIR-emitting spectrum, high fluorescence stability and low cytotoxicity. In addition, they exhibited an obvious fluorescence quenching when Cu²⁺ was present. An NIR nanosensor was prepared for rapidly, sensitively, and selectively determining Cu²⁺ in solution quantitatively and monitoring the changes in Cu²⁺ in cells with fluorescence imaging in a semiquantitative way. The linear relationship between the relative fluorescence intensity (F₀ /F) and the concentration of Cu²⁺ from 5.12 × 10^-8  M to 2.56 × 10^-5  M in solution was observed using an NIR fluorescence spectrophotometer with R² equal to 0.9958. Moreover, in the experiment with the fluorescence microscope, F₀ /F versus the concentration of Cu²⁺ from 5.00 × 10^-8  M to 7.68 × 10^-6  M also showed a good linear relationship with R² equal to 0.9817. Practical water sample ion detecting experiments had good accuracy and recovery rates. Cell experiments showed that the NIR imaging intensity of cells was inversely proportional to the concentration of copper ions, therefore NIR QDs have great potential for detection of metal ions in solution and in cells.