Fabrication of a totally renewable off-channel amperometric platform for microchip electrophoresis

Potentiometric Carbon Quantum Dots-Based Screen-Printed Arrays for Nano-Tracing Gemifloxacin as a Model Fluoroquinolone Implicated in Antimicrobial Resistance

Antimicrobial resistance (AMR) is a neglected issue that poses a serious global threat to public health, causing long-term negative consequences at both humanitarian and economic levels. Herein, we report an unprecedented economic fabrication method of seven potentiometric screen-printed sensors for the ultra-trace determination of gemifloxacin (GEMI) as a model of the fluoroquinolones antibiotics deeply involved in the growing AMR problem. Sensors were constructed by depositing homemade carbon ink on a recycled X-ray sheet, patterned using stencils printed with an office printer in simple, cost-effective steps requiring no sophisticated equipment. Four sensors were modified using carbon quantum dots (CQDs) synthesized from dextrose through a single-step method. Sensors exhibited a linear response in the concentration ranges 10−5–10−2 M (sensors 1, 3 and 4), 10−6–10−3 M (sensor 2) and 10−6–10−2 M (sensors 5, 6 and 7). LOD allowed tracing of the target drug at a nano-molar level down to 210 nM. GEMI was successfully determined in pharmaceutical formulations and different water samples without any pretreatment steps with satisfactory recovery (96.93–105.28% with SD values < 3). All sensors revealed a long lifetime of up to several months and are considered promising tools for monitoring water quality and efficiency of water treatment measures.

Polycaprolactone-enabled sealing and carbon composite electrode integration into electrochemical microfluidics

Combining electrochemistry with microfluidics is attractive for a wide array of applications including multiplexing, automation, and high-throughput screening. Electrochemical instrumentation also has the advantage of being low-cost and can enable high analyte sensitivity. For many electrochemical microfluidic applications, carbon electrodes are more desirable than noble metals because they are resistant to fouling, have high activity, and large electrochemical solvent windows. At present, fabrication of electrochemical microfluidic devices bearing integrated carbon electrodes remains a challenge. Here, a new system for integrating polycaprolactone (PCL) and carbon composite electrodes into microfluidics is presented. The PCL : carbon composites have excellent electrochemical activity towards a wide range of analytes as well as high electrical conductivity (∼1000 S m-1). The new system utilizes a laser cutter for fast, simple fabrication of microfluidics using PCL as a bonding layer. As a proof-of-concept application, oil-in-water and water-in-oil droplets are electrochemically analysed. Small-scale electrochemical organic synthesis for TEMPO mediated alcohol oxidation is also demonstrated.

A plug-in electrophoresis microchip with PCB electrodes for contactless conductivity detection

A plug-in electrophoresis microchip for large-scale use aimed at improving maintainability with low fabrication and maintenance costs is proposed in this paper. The plug-in microchip improves the maintainability of a device because the damaged microchannel layer can be changed without needing to cut off the circuit wires in the detection component. Obviously, the plug-in structure reduces waste compared with earlier microchips; at present the whole microchip has to be discarded, including the electrode layer and the microchannel layer. The fabrication cost was reduced as far as possible by adopting a steel template and printed circuit board electrodes that avoided the complex photolithography, metal deposition and sputtering processes. The detection performance of our microchip was assessed by electrophoresis experiments. The results showed an acceptable gradient and stable detection performance. The effect of the installation shift between the microchannel layer and the electrode layer brought about by the plug-in structure was also evaluated. The results indicated that, as long as the shift was controlled within a reasonable scope, its effect on the detection performance was acceptable. The plug-in microchip described in this paper represents a new train of thought for the large-scale use and design of portable instruments with electrophoresis microchips in the future.