Microwave‐Assisted Synthesis of Quasi‐Pyramidal CuInS 2 –ZnS Nanocrystals for Enhanced Near‐Infrared Targeted Fluorescent Imaging of Subcutaneous Melanoma

Microwave-assisted synthesis of ZnS@CuInxSy for photocatalytic degradation of coloured and non-coloured pollutants

Copper indium sulfide (CuInS2) exhibits strong visible light absorption and thus has the potential for good photocatalytic activity; however, rapid charge recombination limits its practical usage. An intriguing strategy to overcome this issue is to couple CuInS2 with another semiconductor to form a heterojunction, which can improve the charge carrier separation and, hence, enhance the photocatalytic activity. In this study, photocatalysts comprising CuInS2 with a secondary CuS phase (termed CuInxSy) and CuInxSy loaded with ZnS (termed ZnS@CuInxSy) were synthesized via a microwave-assisted method. Structural and morphological characterization revealed that the ZnS@CuInxSy photocatalyst comprised tetragonal CuInS2 containing a secondary phase of hexagonal CuS, coupled with hexagonal ZnS. The effective band gap energy of CuInxSy was widened from 2.23 to 2.71 as the ZnS loading increased from 0 to 30%. The coupling of CuInxSy with ZnS leads to long-lived charge carriers and efficient visible-light harvesting properties, which in turn lead to a remarkably high activity for the photocatalytic degradation of brilliant green (95.6% in 5 h) and conversion of 4-nitrophenol to 4-nitrophenolate ions (95.4% in 5 h). The active species involved in these photocatalytic processes were evaluated using suitable trapping agents. Based on the obtained results, photocatalytic mechanisms are proposed that emphasize the importance of h+, O2•-, and OH- in photocatalytic processes using ZnS@CuInxSy.

The Photoluminescence and Biocompatibility of CuInS2-Based Ternary Quantum Dots and Their Biological Applications

Semiconductor quantum dots (QDs) have become a unique class of materials with great potential for applications in biomedical and optoelectronic devices. However, conventional QDs contains toxic heavy metals such as Pb, Cd and Hg. Hence, it is imperative to find an alternative material with similar optical properties and low cytotoxicity. Among these materials, CuInS2 (CIS) QDs have attracted a lot of interest due to their direct band gap in the infrared region, large optical absorption coefficient and low toxic composition. These factors make them a good material for biomedical application. This review starts with the origin and photophysical characteristics of CIS QDs. This is followed by various synthetic strategies, including synthesis in organic and aqueous solvents, and the tuning of their optical properties. Lastly, their significance in various biological applications is presented with their prospects in clinical applications.

Human Umbilical Cord Wharton's Jelly-Derived Mesenchymal Stem Cells Labeled with Mn2+ and Gd3+ Co-Doped CuInS2-ZnS Nanocrystals for Multimodality Imaging in a Tumor Mice Model

Mesenchymal stem cell (MSCs) therapy has recently received profound interest as a targeting platform in cancer theranostics because of inherent tumor-homing abilities. However, the terminal tracking of MSCs engraftment by fluorescent in situ hybridization, immuno-histochemistry, and flow-cytometry techniques to translate into clinics is still challenging because of a dearth of inherent MSCs-specific markers and FDA approval for genetic modifications of MSCs. To address this challenge, a cost-effective noninvasive imaging technology based on multifunctional nanocrystals (NCs) with enhanced detection sensitivity, spatial-temporal resolution, and deep-tissue diagnosis is needed to be developed to track the transplanted stem cells. A hassle-free labeling of human umbilical cord Wharton's Jelly (WJ)-derived MSCs with Mn²⁺ and Gd³⁺ co-doped CuInS₂-ZnS (CIS-ZMGS) NCs has been demonstrated in 2 h without requiring an electroporation process or transfection agents. It has been found that WJ-MSCs labeling did not affect their multilineage differentiation (adipocyte, osteocyte, chondrocyte), immuno-phenotypes (CD44⁺, CD105⁺, CD90⁺), protein (β-actin, vimentin, CD73, α-SMCA), and gene expressions. Interestingly, CIS-ZMGS-NCs-labeled WJ-MSCs exhibit near-infrared (NIR) fluorescence with a quantum yield of 84%, radiant intensity of ∼3.999 × 10¹¹ (p/s/cm²/sr)/(μW/cm²), magnetic relaxivity (longitudinal r₁ = 2.26 mM^-1 s^-1, transverse r₂ = 16.47 mM^-1 s^-1), and X-ray attenuation (78 HU) potential for early noninvasive multimodality imaging of a subcutaneous melanoma in B16F10-tumor-bearing C57BL/6 mice in 6 h. The ex vivo imaging and inductively coupled plasma mass-spectroscopy analyses of excised organs along with confocal microscopy and immunofluorescence of tumor results also significantly confirmed the positive tropism of CIS-ZMGS-NCs-labeled WJ-MSCs in the tumor environment. Hence, we propose the magnetofluorescent CIS-ZMGS-NCs-labeled WJ-MSCs as a next-generation nanobioprobe of three commonly used imaging modalities for stem cell-assisted anticancer therapy and tracking tissue/organ regenerations.

Noninvasive Tracking and Regenerative Capabilities of Transplanted Human Umbilical Cord-Derived Mesenchymal Stem Cells Labeled with I-III-IV Semiconducting Nanocrystals in Liver-Injured Living Mice

Acute liver injury is a critical syndrome ascribed to prevalent death of hepatocytes and imperatively requires liver transplantation. Such a methodology is certainly hampered due to the deficit of healthy donors. In this regard, stem cell-based regenerative therapies are attractive in repairing injured tissues and organs for medical applications. However, it is crucial to understand the migration, engraftment, and regeneration capabilities of transplanted stem cells in the living animal models. For the first time, we demonstrate rapid labeling of umbilical cord-derived mesenchymal stem cells (MSCs) with near-infrared (NIR)-fluorescent CuInS₂-ZnS nanocrystals (CIZS-NCs) to develop innovative nanobioconjugates (MSCs-CIZS-NBCs) that exhibit 98% labeling efficiency. Before nanobioconjugate synthesis, the pristine CIZS-NCs were prepared via a two-step, hot-injection, rapid and low-cost domestic-microwave-refluxing (MW-R) method within 6 min. The as-synthesized CIZS-NCs display high photoluminescence quantum yield (∼88%) and long-lived lifetime (23.4 μs). In contrast to unlabeled MSCs, the MSCs-CIZS nanobioconjugates show excellent biocompatibility without affecting the stemness, as confirmed by cell viability, immunophenotyping (CD44⁺, CD105⁺, CD90⁺), multi-lineage-specific gene expressions, and differentiation into adipocytes, osteocytes, and chondrocytes. The in vivo fluorescence tracking analyses revealed that the MSCs-CIZS-NBCs after tail-vein injection were initially trapped in the lungs and gradually engrafted in the injured liver within 2 h. The regeneration potential of MSCs-CIZS-NBCs was confirmed via renewal of the portal tract composed of portal veins, bile ducts, and hepatic arteries around the hepatocytes. Consequently, no apparent inflammations, necrosis, or apoptosis was observed in the acetaminophen (APAP)-induced liver-injured BALB/c mice model over 3 days after transplantation, as corroborated using laser-scanning confocal microscopy and histopathological and hematological analyses. Hence, our innovative NIR-fluorescent MSCs-CIZS-NBCs offer an off-the-self technology for noninvasive tracking of transplanted MSCs in an acute-liver-injured animal model for future image-guided cell-therapies.