Carboxylate Functional Groups Mediate Interaction with Silver Nanoparticles in Biofilm Matrix

Abstract

Biofilms causing medical conditions or interfering with technical applications can prove undesirably resistant to silver nanoparticle (AgNP)-based antimicrobial treatment, whereas beneficial biofilms may be adversely affected by the released silver nanoparticles. Isolated biofilm matrices can induce reduction of silver ions and stabilization of the formed nanosilver, thus altering the exposure conditions. We thus study the reduction of silver nitrate solution in model experiments under chemically defined conditions as well as in stream biofilms. Formed silver nanoparticles are characterized by state-of-the art methods. We find that isolated biopolymer fractions of biofilm organic matrix are capable of reducing ionic Ag, whereas other isolated fractions are not, meaning that biopolymer fractions contain both reducing agent and nucleation seed sites. In all of the investigated systems, we find that silver nanoparticle–biopolymer interface is dominated by carboxylate functional groups. This suggests that the mechanism of nanoparticle formation is of general nature. Moreover, we find that glucose concentration within the biofilm organic matrix correlates strongly with the nanoparticle formation rate. We propose a simple mechanistic explanation based on earlier literature and the experimental findings. The observed generality of the extracellular polymeric substance/AgNP system could be used to improve the understanding of impact of Ag+ on aqueous ecosystems, and consequently, to develop biofilm-specific medicines and bio-inspired water decontaminants.

Chlortetracycline-Functionalized Silver Nanoparticles as a Colorimetric Probe for Aminoglycosides: Ultrasensitive Determination of Kanamycin and Streptomycin

“…Briefly, dilute NaOH solution (0.1 mL, 1 mM) was added to 1 mM of CTC solution, and the total volume to 8 mL adjusted with nanopure water. The subsequent addition of AgNO 3 (2 mL, 20 mM) under different temperature conditions (20,40,60, and 80 • C) was performed to improve the AgNPs synthesis. The colorless reaction mixture rapidly turned brown within a few minutes, showing a well-defined SPR band centered at 400 nm.…”

“…The deprotonated species of CTC show improved solubility in water and reduction of Ag + ions. The addition of AgNO 3 (2 mL, 20 mM) to the preheated basic CTC solution was performed under different temperature conditions (20,40,60, and 80 • C). The resultant formation of AgNPs was monitored for 60 min.…”

Fabrication and Application of Highly Stretchable Conductive Fiber‐Based Electrode of Epoxy/NBR Electrospun Fibers Spray‐Coated with AgNW/PU Composites

“…A substrate with stronger σ‐donating polar head groups could tightly hold AgNW through strong coordination‐type bonding . The carboxyl (CO), nitrile (CN), and urethane (NH(CO)O) groups in NBR and WPU with unpaired electrons could provide the strong interaction with AgNW to form the highly conductive fibers for device applications . In addition, the epoxy/NBR blend fiber‐based substrate composed of elastomeric ES nanofibers could absorb conductive composites into the fiber network and further improve its mechanical property because of the large surface area .…”

“…[30] The carboxyl (CO), nitrile (CN), and urethane (NH(CO)O) groups in NBR and WPU with unpaired electrons could provide the strong interaction with AgNW to form the highly conductive fibers for device applications. [31][32][33] In addition, the epoxy/NBR blend fiber-based substrate composed of elastomeric ES nanofibers could absorb conductive composites into the fiber network and further improve its mechanical property because of the large surface area. [34,35] On the other hand, WPU is a water soluble elastomer, which has a good miscibility with AgNW dispersed in ethanol.…”

Evaluation of Phototrophic Stream Biofilms Under Stress: Comparing Traditional and Novel Ecotoxicological Endpoints After Exposure to Diuron

“…Changes in the EPS of stream biofilms have been shown to be important for nutrient cycling, biofilm stability, and the interaction with pollutants ( Flemming and Wingender, 2010 ; Stewart et al, 2013 ; Kroll et al, 2016 ). Interaction with silver nanoparticles, for example, is mediated by carboxylic groups in stream biofilm EPS ( Sambalova et al, 2018 ). Importantly, there have been only a few studies yet that have compared the effects of environmental stress on stream biofilms on these different endpoints using the same samples, and none of them focused specifically on endpoint sensitivity.…”