Antibacterial activity of gold nanorods against <em>Staphylococcus aureus</em> and<em> Propionibacterium acnes</em>: misinterpretations and artifacts

Abstract

The antibacterial activity of gold nanorod (GNR) suspensions of different surface functionalities was investigated against standard strains of Staphylococcus aureus and Propionibacterium acnes , taking into consideration two commonly “overlooked” factors: the colloidal stability of GNR suspensions upon mixing with bacterial growth media and the possible contribution of “impurities/molecules” in GNR suspensions to the observed antibacterial activity. The results demonstrated that cationic polyallylamine hydrochloride (PAH)-GNR were severely aggregated when exposed to bacterial growth media compared to other GNR suspensions. In addition, the free cetyltrimethylammonium bromide (CTAB) present in GNR suspensions is most likely the origin of the observed antibacterial activity. However, the antibacterial activity of GNR themselves could not be excluded. Probing these two critical control studies prevents misinterpretations and artifacts of the antibacterial activity of nanoparticles. Unfortunately, these practices are usually ignored in the published studies and may explain the significant conflicting results. In addition, this study indicates that GNR could be a promising candidate for the treatment of skin follicular diseases such as acne vulgaris.

Preferential Accumulation of Phospholipid-PEG and Cholesterol-PEG Decorated Gold Nanorods into Human Skin Layers and Their Photothermal-Based Antibacterial Activity

“…CTAB-assisted synthesis protocol was used to prepare GNR having aspect ratio (length/width; AR) of ~4 and ~2. This particular shape of GNP was selected owing to their uncommon optical characteristics, superior photothermal and antibacterial activities, and their potential accumulation into skin layers 13,15,18,35,37,38 .…”

“…The antibacterial and photothermal-based antibacterial activities of m-PEG-GNR were investigated in our previous work. PEGylated GNR have MIC value of ~0.45 nM against S. aureus and demonstrated 4-log reduction in S. aureus viable count at concentration range of 0.06–0.25 nM upon treatment with NIR laser beam light 35,37 .…”

Nano-Photothermal ablation effect of Hydrophilic and Hydrophobic Functionalized Gold Nanorods on Staphylococcus aureus and Propionibacterium acnes

“…We have previously reported the antibacterial activity of GNR coated with different hydrophilic ligands 33 . However, the antibacterial activity of hydrophobic GNR was rarely evaluated in the literature.…”

Glucosamine Phosphate Induces AuNPs Aggregation and Fusion into Easily Functionalizable Nanowires

“…We believe that our results are very important for several applications, particularly in the field of nanomedicine [55] in view of the great interest in nanosystems presenting plasmon resonance bands shifted in the IR region where cells and tissues do not absorb the radiation. Accordingly, also because of the use of non-toxic GAP in water and without any organic solvent or surfactant [56] and the ease of functionalization, they can be addressed for therapeutically relevant or analytical purposes.…”