Gold Rod-Polyethylene Glycol-Carbon Dot Nanohybrids as Phototheranostic Probes

Abstract

Emphasis using phototheranostics has been placed on the construction of multifunctional nanoplatforms for simultaneous tumor diagnosis and therapy. Herein, we put forth a novel nanosized luminescent material using the incorporation of red emissive carbon dots on gold nanorods through polyethylene glycol as a covalent linkage for dual-modal imaging and photothermal therapy. The novel nanohybrids, not only retain the optical properties of the gold nanorod and carbon dots, but also possess superior imaging performance in both confocal laser scanning microscopy and fluorescence lifetime imaging microscopy. The nanohybrids also exhibit excellent photothermal performance as phototheranostic nanohybrid probes for in vitro assays. This study promises a new multifunctional nanoplatform for cancer diagnostics and therapeutics.

Keywords: bioimaging; carbon dots; gold nanorod; nanohybrids; photothermal therapy.

Scheme 1

Schematic illustration of GNR–PEG and GNR–PEG–CDs.

Figure 1

TEM images of GNRs (a), CDs (b) and GNR-PEG-CD (c), inset of (b) is high-resolution (HR) TEM image of CDs.

Figure 2

(a) The Fourier transform infrared (FT-IR) spectra of CDs, GNR-PEG and GNR-PEG-CDs; (b) the UV-vis and PL spectra (excited at 480 nm) of CDs; (c) the UV-vis and PL spectra (excited at 480 nm) of GNR–PEG–CDs.

Figure 3

(a) The concentration-dependent temperature elevation; (b) a time-dependent increase in the temperature; (c) photothermal effect of GNR-PEG-CDs; (d) the time constant for heat transfer from the solution is determined by applying the linear time data from the cooling stage in (c) versus the negative natural logarithm of the driving force temperature. Samples were carried out under 808 nm (1.5 W cm⁻²) irradiation.

Figure 4

Confocal laser scanning microscopy (CLSM) images of HeLa cells incubated with CDs (a,b,c) and GNR–PEG–CDs (d,e,f) for 24 h under laser excitation of 405 nm (b,e) and 485 nm (c,f) respectively. Scale bar, 10 μm.

Figure 5

FLIM images of HeLa cells incubated with CDs (a) and GNR-PEG-CDs (b) for 24 h. Scale bar, 50 μm.

Figure 6

(a) In vitro viability results of HeLa cells treated using GNR-PEG-CDs without lasers irradiation (from 0 to 400 µg mL⁻¹); (b) in vitro viability results of HeLa cells treated with GNR-PEG-CDs (from 0 to 100 µg mL⁻¹); (c) CLSM images of GNR-PEG-CDs (100 µg mL⁻¹) before and after NIR irradiation with Calcein-acetoxymethylester and propidium iodide (PI) co-staining. Scale bars: 100 μm.