Enzymatic biomineralization of biocompatible CuInS₂, (CuInZn)S₂and CuInS₂/ZnS core/shell nanocrystals for bioimaging

Abstract

a This work demonstrates a bioenabled fully aqueous phase and room temperature route to the synthesis of CuInS2/ZnS core/shell quantum confined nanocrystals conjugated to IgG antibodies and used for fluorescent tagging of THP-1 leukemia cells. This elegant, straightforward and green approach avoids the use of solvents, high temperatures and the necessity to phase transfer the nanocrystals prior to appli-cation.Non-toxic CuInS2, (CuInZn)S2, and CuInS2/ZnS core/shell quantum confined nanocrystals are synthesized via a biomineralization process based on a single recombinant cystathionine γ-lyase (CSE) enzyme. First, soluble In-S complexes are formed from indium acetate and H2S generated by CSE, which are then stabilized by L-cysteine in solution. The subsequent addition of copper, or both copper and zinc, precursors then results in the immediate formation of CuInS2 or (CuInZn)S2 quantum dots. Shell growth is realized through subsequent introduction of Zn acetate to the preformed core nanocrystals. The size and optical properties of the nanocrystals are tuned by adjusting the indium precursor concentration and initial incubation period. CuInS2/ZnS core/shell particles are conjugated to IgG antibodies using EDC/NHS crosslinkers and then applied in the bioimaging of THP-1 cells. Cytotoxicity tests confirm that CuInS2/ ZnS core/shell quantum dots do not cause cell death during bioimaging. Thus, this biomineralization enabled approach provides a facile, low temperature route for the fully aqueous synthesis of non-toxic CuInS2/ZnS quantum dots, which are ideal for use in bioimaging applications.

Single enzyme direct biomineralization of ZnS, ZnxCd1−xS and ZnxCd1−xS–ZnS quantum confined nanocrystals

“…10 The same mechanism of biomineralization of smCSE is realized in our previous works to react with other metal cations and synthesize nanocrystals such as PbS, 13 CulnS 2 and (CuInZn)S 2 . 46 However, simply adding H 2 S, or more easily Na 2 S, to an aqueous solution of metal cations leads to the formation of bulk material rather than nanocrystals. Nanocrystal formation requires a templating agent to arrest growth.…”

Biogenic Sulfur-Based Chalcogenide Nanocrystals: Methods of Fabrication, Mechanistic Aspects, and Bio-Applications

“…Additionally, the impact of sulfide source and capping agent availability on the NP growth kinetics, size, and stability was elucidated. Similarly, the parent enzyme cystathionine, γ-lyase (CSE), isolated from recombinant E. coli, and synthesized biocompatible CuInS 2 , (CuInZn)S 2 and CuInS 2 /ZnS core/shell QDs [201]. CuInS 2 /ZnS core/shell QDs were further conjugated to IgG antibodies and successfully applied in the bioimaging of THP-1 cells that remained alive, thus highlighting the biocompatibility of these nanocrystals.…”

“…This feature is attributed to the various biomolecules involved in this process as they participate in overcoming the toxicity of the reagents, and contribute to the NP production and stabilization. One of the biomolecules most found adsorbed on the S-NP surface is L-cysteine, especially produced by bacteria and fungi [131,200,201]. In addition to its function as a capping agent, it is also the source of sulfur for S-NP formation through the catalytic activity of several enzymes, such as cysteine desulfhydrase, cysteine synthase, cystathionine γ-lyase, and threonine dehydratase [77,80,95,96,130,200,202].…”

Hydrothermal Synthesis of Aqueous-Soluble Copper Indium Sulfide Nanocrystals and Their Use in Quantum Dot Sensitized Solar Cells

“…Aqueous synthesis also addresses ecological (avoiding toxic solvents) and economic (low temperatures, low cost) concerns related to NC syntheses in organics. Several methods have been proposed for CIS NCs [ 9 ], relying on classical heat-up approaches, using ambient pressure and standard heating [ 10 , 11 , 12 , 13 , 14 ], microwave heating [ 15 , 16 , 17 , 18 , 19 ], or hydrothermal [ 20 , 21 , 22 , 23 , 24 , 25 ] syntheses ( Table S1 ). The latter presents several advantages, such as the possibility to achieve higher temperatures yielding improved solubility of precursors and reaction products.…”