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• A proof-of-concept for CGM based on a non-enzymatic MNEAs. • Electrodeposition of catalytic Pt-black on Au MNs for CGM in-vitro and in-vivo. • MNs showed a good dynamic range (1-20 mM) and detection limit (10 µM) in PBS. • The fabricated device showed a good stability as CGMS for 7 days in-vivo. Individuals with diabetes can considerably benefit from continuous glucose monitoring (CGM). Addressing this challenge, a proof-of-concept for a pain-free CGM was presented based on a highly porous platinum black (Pt-black)-modified non-enzymatic microneedle electrode arrays (MNEAs). Porous Pt-black was electrodeposited on microneedle substrates using potentiometry by employing a charge density of -2.5 mA cm˗2. The surface of the porous Pt-black-modified microneedles (MNs) was optimally packed using Nafion (Nf) biocompatible ionomer. The dimensions of the fabricated microneedles were 650 µm × 110 µm × 150 µm in height, width, and thickness, respectively. The surface morphology of the modified MNs was studied using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The microneedle sensor showed a wide glucose dynamic range (1 − 20 mM) in phosphate buffer saline (PBS) and artificial interstitial fluid (ISF) in-vitro with good sensitivities (PBS: 5.786 µA mM−1 cm−2, ISF: 4.380 µA mM−1 cm−2), detection limits (PBS: 10 µM, ISF: 22.5 µM), stability (2% lost at the end of 7 h), selectivity, reproducibility (2.32% RSD), and a response time of 2 s with good glucose recoveries in ISF (98%-102.5%). The device exhibited good stability (7 days) as a sensor in-vivo and lost its functional activity after 7 days due to electrode biofouling. [ABSTRACT FROM AUTHOR]

Individuals with diabetes can benefit considerably from continuous blood glucose monitoring. To address this challenge, a proof-of-concept was performed for continuous glucose monitoring (CGM) based on an enzymeless porous nanomaterial (pNM)-modified microneedle electrode array (MNEA). The pNM sensing layer was electrochemically deposited on MNs by applying a fixed negative current of −2.5 mA cm˗2 for 400 s. The pNM-modified MNEA was packed using a biocompatible Nafion ionomer. The fabricated MNEAs were 600 × 100 × 150 µm in height, width, and thickness, respectively. The surfaces of the modified MNs were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The fabricated MNEAs showed a wide dynamic range (1–30 mM) in phosphate-buffered saline (PBS) and in artificial interstitial fluid (ISF), with good sensitivities (PBS: 1.792 ± 0.25 µA mM−1 cm−2, ISF: 0.957 ± 0.14 µA mM−1 cm−2) and low detection limits (PBS: 7.2 µM, ISF: 22 µM). The sensor also showed high stability (loss of 3.5% at the end of 16 days), selectivity, and reproducibility (Relative standard deviations (RSD) of 1.64% and 0.70% for intra- and inter-assay, respectively) and a good response time (2 s) with great glucose recovery rates in ISF (98.7–102%). [ABSTRACT FROM AUTHOR]

An electrochemical capacitance immunosensor based on an interdigitated wave-shaped micro electrode array (IDWµE) for direct and label-free detection of C-reactive protein (CRP) was reported. A self-assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). The nature of gold-sulfur interactions on SAM-treated electrode array was probed by X-ray photoelectron spectroscopy (XPS). The covalent linking of anti-CRP-antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate-buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti-CRP-antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01–10,000 ng mL−1. The electrode showed detection limits of 0.025 ng mL−1 and 0.23 ng mL−1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation (RSD), 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS. [ABSTRACT FROM AUTHOR]

The authors report a label-free and direct detection of rheumatoid factor- Immunoglobulin M (IgM-RF) based on an impedimetric-interdigitated wave type microelectrode array (IDWμE). IDWμE was functionalized with a self-assembled monolayer (SAM) of thioctic acid for antigen immobilization. The SAM functionalized IDWμE were characterized by atomic force microscopy, Energy Dispersive X-Ray Spectroscopy, and X-ray photoelectron spectroscopy. The covalent immobilization of IgG-Fc onto the SAM modified electrode arrays was characterized morphologically via AFM and electrochemically via cyclic voltammetry and electrochemical impedance spectroscopy. Impedimetric measurements in the presence of redox probe (Potassium ferrocyanide and potassium ferricyanide) showed a significant change in both the impedance spectrum and charge transfer resistance upon IgM-RF binding. Impedance measurements were target specific and linear with an increase in IgM-RF concentrations between 1 and 200 IU mL−1 in redox probe and human serum, respectively. The sensor showed detection limits of 0.6 IU mL−1 in the presence of redox probe and 0.22 IU mL−1 in the human serum. The biosensor exhibited good reproducibility (relative standard deviation (RSD), 4.96%) and repeatability (RSD, 2.31%) with an acceptable selectivity towards IgM-RF detection. The sensor also showed a good stability for 3 weeks at 4 °C in 1X PBS. Therefore, the sensitive and stable immunosensor exhibiting IDWμE features can be integrated with a miniaturized potentiostat to develop a sensing system that detects IgM-RF for point-of-care applications. • IDWμE array was fabricated using photolithography and a chemical wet etching. • Immunosensor based on self-assembled monolayers of thioctic acid was prepared. • IgM-RF was detected using a sensitive label-free impedimetric Immunosensor. • Biosensor presents good stability and selectivity to quantify IgM-RF in serum samples. [ABSTRACT FROM AUTHOR]