MXene (Ti3C2Tx)-Embedded Nanocomposite Hydrogels for Biomedical Applications: A Review

Abstract

Polymeric nanocomposites have been outstanding functional materials and have garnered immense attention as sustainable materials to address multi-disciplinary problems. MXenes have emerged as a newer class of 2D materials that produce metallic conductivity upon interaction with hydrophilic species, and their delamination affords monolayer nanoplatelets of a thickness of about one nm and a side size in the micrometer range. Delaminated MXene has a high aspect ratio, making it an alluring nanofiller for multifunctional polymer nanocomposites. Herein, we have classified and discussed the structure, properties and application of major polysaccharide-based electroactive hydrogels (hyaluronic acid (HA), alginate sodium (SA), chitosan (CS) and cellulose) in biomedical applications, starting with the brief historical account of MXene's development followed by successive discussions on the synthesis methods, structures and properties of nanocomposites encompassing polysaccharides and MXenes, including their biomedical applications, cytotoxicity and biocompatibility aspects. Finally, the MXenes and their utility in the biomedical arena is deliberated with an eye on potential opportunities and challenges anticipated for them in the future, thus promoting their multifaceted applications.

Keywords: MXenes (Ti3C2Tx); biomedical; nanocomposites; nanomaterials; nanotechnology.

Figure 2

(A) MAX phases M_n+1AX_n forming elements. (B) SEM pictures of the characteristic layered structure and the mechanical response of Ti₂AlC, Cr₂AlC, Ti₃SiC₂ and Ti₃AlC₂ [39].

Figure 1

Yearly distribution of scientific articles published on MXenes in PubMed-indexed scientific journals from 2012 to December 2021.

Figure 3

SEM and micro-CT images for the (A,E) reference CH/SHA matrix nanocomposite and modified with (B,F) 1 wt.%, (C,G) 5 wt.% and (D,H) 10 wt.% of 2D Ti₃C₂T_x MXene lakes [69].

Figure 4

(A) E. coli and (B) S. aureus antibacterial activity B-X and GA-X are mats that have been treated with NaOH and glutaraldehyde, respectively. On the 0.75 wt.% Ti₃C₂Tz/CS nanofiber mat, SEM micrographs reveal (C) undamaged and (D) destroyed E. coli bacteria. The star symbol denotes samples that differ substantially from the control, p ≤ 0.05 [63].

Figure 5

Schematics for the synthesis of MXene/alginate composites [66].

Figure 6

SBM sheet fabrication and structural characterization. (A) Vacuum filtering was used to assemble the MXene-SA hybrid building blocks into an HBM sheet. The Ca²⁺ was subsequently absorbed by the HBM sheet, resulting in the formation of an SBM sheet. (B) A photograph of an SBM sheet demonstrating its pliability. (C) A low-resolution SEM picture of the SBM sheet’s fracture surface. (D) A high-resolution SEM picture of the region indicated in (C). (E) Ca²⁺ EDS mapping and (F) EDS spectra of the region delineated in (D). WAXS patterns for an incident Cu-K X-ray beam parallel to the sheet plane and related azimuthal scan profiles for the 002 peak for the sheets: (G) MXene, (H) IBM, (I) HBM and (J) SBM. Scale bars: (B) 1 cm, (C) 5 μm and (D) 1 μm [77].

Figure 7

Schematic representation of assorted applications of MXene composites.

Figure 8

In vitro PTT efficacy (A) relative viabilities of HaCaT, A375, MCF-10A and MCF-7 cells after the PTT procedure with the use of various concentrations of Ti₂C_PEG flakes. (B) Comparison of the efficacy of 2D Ti₂C-PEG as a novel PTT agent with the measured temperature changes for cancer and non-cancer cells on the example of human mammary gland-derived cell lines. (C) Exemplary microscopic images after PTT treatment, including the NIR group and groups exposed to various concentrations of the test material and NIR [92].

Figure 9

Ta₄C₃-SP MXene nanosheets have photothermal treatment effects both in vitro and in vivo. (A) Schematic representation of Ta₄C₃-SP MXene nanosheets employed in PTT. (B) Ta₄C₃-SP MXene nanosheet absorbance spectra and photothermal stability after five heating and cooling cycles. (C) Confocal fluorescence imaging of in vitro photothermal ablation of 4T1 cells following multiple treatments at 1.5 W cm⁻¹ (scale bar: 100 m). (D) Infrared thermal pictures at the tumor site of 4T1 tumor-bearing mice in control, Ta₄C₃-SP (i.v.) + NIR laser and Ta₄C₃-SP (i.t.) + NIR laser groups at different time intervals during laser irradiation. (E) Tumor growth curves following various treatments. (F) Images of tumor-bearing mice following PTT [80].

Figure 10

Multilayered Ti3C2Tx MXene film characterization. (A) Photograph of the MXene film, which is flexible and free-standing. (B) SEM picture of a cross-section of MXene sheets, scale bars: 5 mm, 1 μm. (C) SEM picture of the surface of MXene films. Scale bars are 50 μm long. (D) Ti₃C₂T_x MXene and Ti₃AlC₂ MAX XRD patterns. (E) Water contact angles (n = 3) on Ti₃C₂T_x MXene films [96].

Figure 11

Schematic depiction of antibacterial activity of Ti₃C₂T_x MXene [3].

Figure 12

(A) Photographs of agar plates onto which E. coli (top panel) and B. subtilis (bottom panel) bacterial cells were re-cultivated after treatment for 4 h with a control (a), and 100 µg/mL of Ti₃AlC₂ (b), ML-Ti₃C₂T_x (c) and delaminated Ti₃C₂T_x (d). (B) Percentage of growth inhibition of bacterial cells treated with 100 µg/mL of Ti₃AlC₂, ML-Ti₃C₂T_x and delaminated Ti₃C₂T_x [3].

Figure 13

Ti₃C₂T_x MXene has antibacterial action. (A) Photographs of E. coli and B. subtilis growth on unmodified PVDF (control), fresh and aged Ti₃C₂Tx MXene-coated PVDF membranes cultured for 24 h at 35 °C. (B) Cell viability measurements of E. coli and B. subtilis treated with Ti₃C₂T_x, Fresh Ti₃C₂T_x/PVDF and Aged Ti₃C₂T_x/PVDF. The colony-forming count method was used to calculate survival rates. Reproduced with permission from [3].