Pt-Decorated MWCNTs–Ionic Liquid Composite-Based Hydrogen Peroxide Sensor To Study Microbial Metabolism Using Scanning Electrochemical Microscopy

Abstract

Hydrogen peroxide (H2O2) is a highly relevant metabolite in many biological processes, including the oral microbiome. To study this metabolite, we developed a 25 μm diameter, highly sensitive, non/enzymatic H2O2 sensor with a detection limit of 250 nM and a broad linear range of 250 nM to 7 mM. The sensor used the synergistic activity of the catalytically active Pt nanoparticles on a high surface area multiwall carbon nanotube and conducting ionic liquid matrix to achieve high sensitivity (2.4 ± 0.24 mA cm−2 mM−1) for H2O2 oxidation. The unique composite allowed us to miniaturize the sensor and couple it with a Pt electrode (25 μm diameter each) for use as a dual scanning electrochemical microscopy probe. We could detect 65±10 >M of H2O2 produced by Streptococcus gordonii (Sg) biofilms at a 50 μm above its surface in the presence of 1 mM glucose and artificial saliva solution (pH 7.2 at 37°C). Because of the high stability and low detection limit, the sensor showed a promising chemical image of H2O2 produced by Sg biofilms. We were also able to detect 30 μM of H2O2 at 50 μm above the biofilm in the presence of the H2O2-decomposing salivary lactoperoxidase and thiocyanate, which would not otherwise be possible by existing H2O2 assay. Thus, this sensor can potentially find application in the study of other important biological processes in a complex matrix where circumstance demands a low detection limit in a compact space.

Real-Time Metabolic Interactions between Two Bacterial Species Using a Carbon-Based pH Microsensor as a Scanning Electrochemical Microscopy Probe

“…A H 2 O 2 sensor was prepared by using a similar procedure to that reported in our earlier study 30 . In short, a dual Pt UME (each Pt disc having a 25-μm diameter) with RG 10 (ratio of the insulating glass diameter to the conducting Pt diameter) was fabricated.…”

“…In short, a dual Pt UME (each Pt disc having a 25-μm diameter) with RG 10 (ratio of the insulating glass diameter to the conducting Pt diameter) was fabricated. To make the H 2 O 2 sensor, one of the two Pt electrodes was etched in 60:36:4 v/v saturated CaCl 2 :H 2 O:HCl solution to make a 10-μm cavity by applying 5 V across a graphite rod 30 . The cavity was then cleaned in a water/ethanol mixture by sonication and subsequently dried under nitrogen.…”

“…We used our newly developed ionophore containing carbon-based SECM pH probe, along with H 2 O 2 microsensors, 30 to study how the microbial metabolic interactions shape species composition, eventually self-selecting for a disease-associated community. To better understand how metabolic changes in a polymicrobial consortium favor a pathogenic composition, we used a polymicrobial biofilm model comprising the commensal species S. gordonii and the pathogenic species S. mutans .…”

Scanning electrochemical microscopy and its potential for studying biofilms and antimicrobial coatings

“…While electrochemical methods have been used in microbial studies for quite some time, SECM has only been employed more frequently in microbial research within the last decade. Gram-positive and Gram-negative bacteria such as Staphylococcus aureus [ 90 ], Rhodobacter sphaeroides [ 79 ], Salmonella typhimurium [ 91 ], Pseudomonas aeruginosa [ 92 , 93 ], Vibrio fischeri [ 94 ], Streptococcus gordonii [ 95 ] and Escherichia coli [ 82 , 96 – 98 ] have been investigated with SECM. Earlier SECM studies were mainly focused on mapping oxygen consumption of microbial cells [ 99 ].…”

Boron Doped ZIF‐67@Graphene Derived Carbon Electrocatalyst for Highly Efficient Enzyme‐Free Hydrogen Peroxide Biosensor

“…Based on this, a better H 2 O 2 sensor needs electrode material with higher catalytic activity, which could accelerate the electron transfer rate and reduce the production of intermediate product (·OH ad ). Because the intermediate product has strong oxidation capacity and will damage the electrode …”