Platinum Nanoparticle Size and Density Impacts Purine Electrochemistry with Fast-Scan Cyclic Voltammetry.

We demonstrate the density and shape of platinum nanoparticles (PtNP) on carbon-fiber microelectrodes with fast-scan cyclic voltammetry (FSCV) directly impacts detection of adenosine. Previously, we showed that metal nanoparticle-modified carbon significantly improves adenine-based purine detection; however, how the size and shape of the particles impact electrochemical detection was not investigated. Electrochemical investigations of how the surface topology and morphology impacts detection is necessary for designing ultrasensitive electrodes and for expanding fundamental knowledge of electrode-analyte interactions. To change the density and shape of the PtNP's on the surface, we varied the concentration of K2PtCl6 and electrodeposition time. We show that increasing the concentration of K2PtCl6 increases the density of PtNP's while increasing the electrodeposition time impacts both the density and size. These changes manipulate the adsorption behavior which impacts sensitivity. Based on these results, an optimal electrodeposition procedure was determined to be 1.0 mg/mL of K2PtCl6 deposited for 45 s and this results in an average increase in adenosine detection by 3.5 ±0.3-fold. Interestingly, increasing the size and density of PtNPs negatively impacts dopamine detection. Overall, this work provides fundamental insights into the differences between adenosine and dopamine interaction at electrode surfaces.

Metal Nanoparticle Modified Carbon-Fiber Microelectrodes Enhance Adenosine Triphosphate Surface Interactions with Fast-Scan Cyclic Voltammetry.

Adenosine triphosphate (ATP) is an important rapid signaling molecule involved in a host of pathologies in the body. Historically, ATP is difficult to directly detect electrochemically with fast-scan cyclic voltammetry (FSCV) due to limited interactions at bare carbon-fibers. Systematic investigations of how ATP interacts at electrode surfaces is necessary for developing more sensitive electrochemical detection methods. Here, we have developed gold nanoparticle (AuNP), and platinum nanoparticle (PtNP) modified carbon-fiber microelectrodes coupled to FSCV to measure the extent to which ATP interacts at metal nanoparticle-modified surfaces and to improve the sensitivity of direct electrochemical detection. AuNP and PtNPs were electrodeposited on the carbon-fiber surface by scanning from -1.2 to 1.5 V for 30 s in 0.5 mg/mL HAuCl4 or 0.5 mg/mLK2PtCl6. Overall, we demonstrate an average 4.1 ± 1.0-fold increase in oxidative ATP current at AuNP-modified and a 3.5 ± 0.3-fold increase at PtNP-modified electrodes. Metal nanoparticle-modified surfaces promoted improved electrocatalytic conversion of ATP oxidation products at the surface, facilitated enhanced adsorption strength and surface coverage, and significantly improved sensitivity. ATP was successfully detected within living murine lymph node tissue following exogenous application. Overall, this study demonstrates a detailed characterization of ATP oxidation at metal nanoparticle surfaces and a significantly improved method for direct electrochemical detection of ATP in tissue.