NIR-Triggered Hyperthermal Effect of Polythiophene Nanoparticles Synthesized by Surfactant-Free Oxidative Polymerization Method on Colorectal Carcinoma Cells

Abstract

In this work, polythiophene nanoparticles (PTh-NPs) were synthesized by a surfactant-free oxidative chemical polymerization method at 60 °C, using ammonium persulphate as an oxidant. Various physicochemical properties were studied in terms of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy, and differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA). Photothermal performance of the as-synthesized PTh-NPs was studied by irradiating near infra-red of 808 nm under different concentration of the substrate and power supply. The photothermal stability of PTh-NPs was also studied. Photothermal effects of the as-synthesized PTh-NPs on colorectal cancer cells (CT-26) were studied at 100 µg/mL concentration and 808 nm NIR irradiation of 2.0 W/cm² power. Our in vitro results showed remarkable NIR laser-triggered photothermal apoptotic cell death by PTh-NPs. Based on the experimental findings, it is revealed that PTh-NPs can act as a heat mediator and can be an alternative material for photothermal therapy in cancer treatment.

Keywords: CT-26 cells; apoptotic cell death; cancer treatment; chemical polymerization; photothermal; polythiophene nanoparticles.

Figure 1

Physicochemical characterization of polythiophene particles. (a) FESEM image, and (b) EDX mapping of PTh–NPs, which shows the presence of C and S elements, which are the constituent elements of polythiophene. Particles size dirstribution diagram by (c) DLS anaysis and (d) by Biological Transmission Electron Microscopy.

Figure 2

Characterization of PTh–NPs of (a) Thermogravimetric curve (wt. % vs. temperature curve) and differential scanning curve (heat flow vs. temperature curve, and (b) X-ray diffraction.

Figure 3

Photothermal study of PTh–NPs. (a) Photothermal performance of polythiophene nanocomposites, and (b) photothermal stability curve by real time temperature record for PTh–NPs, 100 µg/mL, under irradiation of 2.0 W/cm².

Figure 4

Cytotoxicity study of PTh–NPs. (a) Cell viability and (b) Crystal violet stained microscope images of CT-26 cell by treatment with PTh–NPs at concentration of (25, 50, 100, 200, and 500) μg/mL. Each value is expressed as the mean ± standard deviation. * P < 0.05, when compared with the control.

Figure 5

In vitro cellular uptake and photothermal effects of PTh–NPs. (a) Cellular uptake image of PTh–NPs in CT-26 cells using microscopy after 3 h of incubation. (b) Infrared photothermal image of PTh–NPs (100 μg/mL) dispersed in CT-26 cells culture media under 808 nm laser irradiation after 5 min at 2.0 W/cm². (c) Live/dead fluorescence images of PTh–NPs treated CT-26 cells with/without 808 nm laser irradiation (2.0 W/cm², 5 min).

Figure 6

Photothermal effects of PTh–NPs on apoptotic cell death. (a) Cell viability of PTh–NPs (100 μg/mL) treated CT-26 cells with/without 808 nm laser irradiation (2.0 W/cm², 5 min) at 24 h of cultivation. (b) Flow cytometric analysis to determine cell death of CT-26 cells after PTh–NPs with/without NIR irradiation. (c) Percentage of apoptotic CT-26 cells. Each value is expressed as the mean ± standard deviation. * P < 0.05 and ** P < 0.01, when compared to the control.