Gold Nanorods for Doxorubicin Delivery: Numerical Analysis of Electric Field Enhancement, Optical Properties and Drug Loading/Releasing Efficiency

Abstract

The optical properties and electric field enhancement of gold nanorods for different cases were investigated in this study. The numerical analysis was carried out to understand the functionality and working of gold nanorods, while the experimental portion of the work was focused on the efficiency of gold nanorods for targeted drug delivery. COMSOL Multiphysics was used for numerical analysis. The theoretical results suggest the use of gold nanorods (AuNRs) for anticancer applications. The resonance peaks for gold nanorods of 10 nm diameter were observed at 560 nm. The resonance peaks shifted towards longer wavelengths with an increase in nanorod size. The resonance peaks showed a shift of 140 nm with a change in nanorod length from 25 to 45 nm. On the experimental side, 22 nm, 35 nm and 47 nm long gold nanorods were produced using the seed-mediated growth method. The surface morphology of the nanorods, as well as their optical characteristics, were characterized. Later, gold nanorods were applied to the targeted delivery of the doxorubicin drug. Gold nanorods showed better efficiency for doxorubicin drug loading time, release time, loading temperature, and release temperature. These results reveal that AuNRs@DA possess good ability to load and deliver the drug directly to the tumorous cells since these cells show high temperature and acidity.

Keywords: COMSOL Multiphysics; doxorubicin; drug delivery; gold nanorods.

Figure 1

(a) Schematic of interaction of an electromagnetic wave with a gold nanorod and (b) extinction cross-section of AuNR at λ = 635 nm, length = 35 nm and r = 10 nm.

Figure 2

(a) Electric field enhancement (V/m) (a) at λ = 460 nm, (b) at λ = 580 nm, (c) at plasmonic resonance (λ = 635 nm) and (d) at λ = 700 nm for the gold nanorod of 35 nm length under p-wave illumination.

Figure 3

Extinction cross-section of gold nanorods under p-wave illumination.

Figure 4

Change in extinction cross-section of the gold nanorods with incident wavelength for different refractive index values.

Figure 5

SEM images of AuNRs produced with (a) 3 mL of AgNO₃, (b) 4 mL of AgNO₃, and (c) 5 mL of AgNO₃.

Figure 6

UV-vis spectra of AuNRs produced with 3 mL, 4 mL and 5 mL of AgNO₃ solution.

Figure 7

XRD spectra of AuNRs produced with 3 mL, 4 mL and 5 mL of AgNO₃ solution.

Figure 8

Illustration of the drug loading mechanism.

Figure 9

(a) Change in UV absorbance with loading time; (b) bar graph shows the decrease in loading capacity with time; (c) change in UV absorbance with time during desorption; (d) bar graph of desorption with time.

Figure 10

(a) Variation in UV absorbance as a function of loading temperature; (b) a bar graph illustrates the reduction in loading capacity over temperature; (c) during desorption, the UV absorbance changes with temperature; (d) pattern of desorption over temperature is illustrated as a bar graph.

Figure 11

UV–Vis spectra of solutions prepared with different amounts of AuNPs (0.3, 0.4, 0.5 g).