Cytotoxicity investigation of luminescent nanohybrids based on chitosan and carboxymethyl chitosan conjugated with Bi2S3 quantum dots for biomedical applications

Abstract

Bioengineered hybrids are emerging as a new class of nanomaterials consisting of a biopolymer and inorganic semiconductors used in biomedical and environmental applications. The aim of the present work was to determine the cytocompatibility of novel water-soluble Bi₂S₃ quantum dots (QDs) functionalized with chitosan and O-carboxymethyl chitosan (CMC) as capping ligands using an eco-friendly aqueous process at room temperature. These hybrid nanocomposites were tested for cytocompatibility using a 3-(4,5-dimethylthiazol-2yl) 2,5-diphenyl tetrazolium bromide (MTT) cell proliferation assay with cultured human osteosarcoma cells (SAOS), human embryonic kidney cells (HEK293T cells) and a LIVE/DEAD® viability-cytotoxicity assay. The results of the in vitro assays demonstrated that the CMC and chitosan-based nanohybrids were not cytotoxic and exhibited suitable cell viability responses. However, despite the "safe by design" approach used in this research, we have proved that the impact of the size, surface charge and biofunctionalization of the nanohybrids on cytotoxicity was cell type-dependent due to complex mechanisms. Thus, these novel bionanocomposites offer promising prospects for potential biomedical and pharmaceutical applications as fluorescent nanoprobes.

Fig. 1. (A) UV-Vis absorption spectra, (B) “TAUC” relation, and (C) PL emission spectra of Bi₂S₃ colloidal solutions: (a) QD_CHI_3.0, (b) QD_CMC_3.0, and (c) QD_CMC_10.0. (D) QD_CMC_3.0 QD solution under (a) natural light illumination and (b) fluorescence with illumination at 254 nm UV irradiation (dark chamber).

Fig. 2. (A) TEM image, (B) SAED pattern, and (C) XRD pattern of the QD_CHI_3.0 nanoparticles.

Fig. 3. Schematic representation of the dependence of H_D and ZP (ζ) on the surface capping ligands and pH (not to scale): (a) QD_CHI_3.0, (b) QD_CMC_3.0, and (c) QD_CMC_10.0.

Fig. 4. Cell viability response of the SAOS cultures using the MTT assay (a); SAOS cell morphology in the control (b) and QD_CMC_10.0 (c) after 24 hours of incubation in contact with the samples (scale bar = 100 μm, 200×). Cell viability (%) calculated to be 100% × (absorbance of the sample and cells)/(absorbance of the control).

Fig. 5. Cell viability response of the HEK293T cultures using the MTT assay (a), HEK293T cell morphology in the control (b) and QD_CMC_3.0 (c) after 24 h of incubation in contact with the samples (scale bar = 100 μm, 200×); top inset: Schematic representation of the interactions of the nanohybrids with different surface charges and the HEK293T cells at the bio-interfaces (not to scale). Cell viability (%) calculated to be 100% × (absorbance of the sample and cells)/(absorbance of the control).

Fig. 6. (A) Images of the LIVE/DEAD® assay in the control group (a), QD_CHI_3.0 (b), QD_CMC_3.0 (c), and QD_CMC_10.0 (d). (B) Summary of the LIVE/DEAD® results.