Enhanced Photothermal Bactericidal Activity of the Reduced Graphene Oxide Modified by Cationic Water-Soluble Conjugated Polymer

Abstract

Surface modification of graphene is extremely important for applications. Here, we report a grafting-through method for grafting water-soluble polythiophenes onto reduced graphene oxide (RGO) sheets. As a result of tailoring of the side chains of the polythiophenes, the modified RGO sheets, that is, RGO-g-P3TOPA and RGO-g-P3TOPS, are positively and negatively charged, respectively. The grafted water-soluble polythiophenes provide the modified RGO sheets with good dispersibility in water and high photothermal conversion efficiencies (ca. 88%). Notably, the positively charged RGO-g-P3TOPA exhibits unprecedentedly excellent photothermal bactericidal activity, because the electrostatic attractions between RGO-g-P3TOPA and Escherichia coli (E. coli) bind them together, facilitating direct heat conduction through their interfaces: the minimum concentration of RGO-g-P3TOPA that kills 100% of E. coli is 2.5 μg mL, which is only 1/16th of that required for RGO-g-P3TOPS to exhibit a similar bactericidal activity. The direct heat conduction mechanism is supported by zeta-potential measurements and photothermal heating tests, in which the achieved temperature of the RGO-g-P3TOPA suspension (2.5 μg mL, 32 °C) that kills 100% of E. coli is found to be much lower than the thermoablation threshold of bacteria. Therefore, this research demonstrates a novel and superior method that combines photothermal heating effect and electrostatic attractions to efficiently kill bacteria.

Two‐Dimensional Materials for Antimicrobial Applications: Graphene Materials and Beyond

“…Xiao and co-workersc ompared the photothermal antibacteriala ctivity of positivelya nd negatively charged rGO composites prepared by covalently graftingp oly[3-(3'-thienyloxy)propyltrimethylammonium bromide] (P3TOPA, ac ationic conjugated polymer) and poly[sodium 3-(3'-thienyloxy)propanesulfonate] (P3TOPS, an anionic conjugatedp olymer). [116] Despite the similar photothermal performance of the as-synthesized RGO-g-P3TOPAa nd RGO-g-P3TOPS, intimatec ontact with bacteria,m ediated by electrostatic attractions, led to a1 6 times highere fficacy of RGO-g-P3TOPA. Moreover,a sd emonstrated in our previous work, nanoparticles with long-alkylchain-linked quaternary ammonium salts have excellent antimicrobial performance with low cytotoxicity towardm ammalian cells.…”

“…Consequently,G Ms have also been used as nonmetal bactericide carriers to produce GM-metal-free nanohybrids. Antibiotics, [108,109] polymers, [110][111][112][113][114][115][116][117][118] quaternary ammonium/phosphonium salts, [119][120][121] and halogens [122] have been combined with GMs by noncovalent adsorption or chemical conjugation.A bdelhamid et al provedt hat water-soluble antibiotic gramicidin (GD) can be adsorbed by GO through physical interactions and the antibacterial activity of the resultant GOGD is enhanced because of an increased local concentration of GD. [108] Compared with antibiotics, polymers usually cannot efficiently inhibit the growth of microorganisms;h owever,w ith their structure-mediated properties, polymers can enhancet he antimicrobial performance of GMs through different mechanisms.…”

Recent Advances in Carbon Nanomaterials for Cancer Phototherapy

“…In combination of high tumor uptake due to the EPR effect and excellent photothermal conversion capability,N GS-PEG following NIR irradiation could lead to highly effective inhibition of tumor.S ince then, in vitro and in vivo GO-based PTT has been studied in detail by several different groups, in which hydrophilic molecules and functional moieties are covalently or noncovalently functionalized on the surfaceo fG O. [46] The oxidation of graphene causes the damage of p-conjugated structure in the GO, thus, its NIRa bsorption is decreased. The reduction of GO can be used to improvet he PTT efficacy of GO materials.…”

Membrane destruction-mediated antibacterial activity of tungsten disulfide (WS2)

“…[21][22][23] For instance, graphene (and graphene oxide) has been systematically studied 24 for its antimicrobial activities, [25][26][27][28] along with its underlying molecular mechanisms. [29][30][31][32] It was revealed that graphene and graphene oxide nanosheets can cut into cell membranes, 32 extract large amount of phospholipids, 32 and create holes (pores) on cell membranes, 33 through large scale molecular dynamics simulations.…”