The Chemistry and Biology of Gold Nanoparticle-Mediated Photothermal Therapy: Promises and Challenges

Abstract

Under laser radiation, cells labeled with gold nanoparticles (AuNPs) are believed to suffer thermal damage due to the transfer of the absorbed light from the AuNPs to the cells. This process, which involves complex mechanisms such as the rapid electron–phonon decay in the AuNPs , followed by phonon–phonon relaxation, culminates in the localized heating of both the AuNPs and the cells, setting the rational for the use of these nanostructures, under laser light, in cancer photothermal therapy (PTT). Here, we discuss the chemical and biological aspects of this promising new therapeutic approach, including the advantages over conventional cancer therapies and the challenges that scientists still need to overcome to progress toward translation research.

Gold Nanoparticle Approach to the Selective Delivery of Gene Silencing in Cancer—The Case for Combined Delivery?

“…The AuNPs’ photoexcitation at their SPR maximum wavelength results in an efficient light-to-heat conversion [18,26]. Depending on the amount of heat generated and transferred to the surroundings, it can compromise or destroy cells, whether the AuNPs are within cancer cells or on their surface [39]. In addition, tumor tissue is thought to be more hypoxic, acidic, and nutrient-deficient than normal tissues, traits that are believed to increase the sensitivity of cancer cells to heat, though the effects of thermal therapy are dependent on cancer type [40].…”

“…Nowadays, in order to localize and moderate the heat, diverse heating sources are used, for instance, radiofrequency microwaves and ultrasounds. More recently, medical procedures have been revolutionized with the discovery of lasers, which allow an even more precise thermal damage to tumor tissue [39]. Metal nanoparticles, especially AuNPs, have shown unique photophysical properties.…”

“…However, using laser sources whose emission wavelength overlaps with the SPR peak of AuNPs is expected to allow a greater light-to-heat conversion. Besides, for small particles (10–40 nm in diameter), scattering is almost negligible and their extinction is almost equal to the absorption component [39]. …”

Gold Nanobeacons: A Potential Nanotheranostics Platform

“…Among the possible imaging modalities using AuNPs, we may include light scattering imaging, surface-enhanced Raman spectroscopy, photoacoustic imaging, x-ray computed tomography, two-photon fluorescence imaging and MRI [13].…”

“…Because the silencing moiety is bonded to the AuNPs, the antisense oligonucleotide shows an increased halflife in the presence of nucleases, since it has been shown that AuNPs confer considerable protection against enzymatic degradation [16,17]. What is more, the PEGylated AuNPs are extremely stable under physio logical conditions and will be able to evade macrophage clearance, thus increasing their in vivo efficacy [6,13]. Perhaps one of the most relevant features of such a design is the capability conveyed by the AuNPs to act as efficient transfection agents in aqueous media (i.e., the AuNPs act as carriers or vectors for the silencing moiety and confer protection while being an active part of the imaging and tracking of the events).…”