Although commercial screen‐printed electrodes (SPEs) are used extensively for biosensor purposes nowadays, detailed studies on characterization are still limited. In this study, the surface of the gold‐based screen‐printed electrode (SPGE) was carefully modified with self‐assembly‐monolayer through an optimized immobilization procedure. The key physical and chemical properties with regeneration capacity of the developed biosensors were assessed by various characterization techniques. Then SPGE was used to determine its sensitivity, limit of detection (LOD) and limit of quantification (LOQ) for a toxin substance of domoic acid in seafood that has become more common and rising concern of marine wildlife and seawater pollution. LOD in phosphate buffered saline (PBS) and cell culture media were obtained as 2.93 ng mL−1 and 4.28 ng mL−1, respectively. The reduced sensitivity for antibody‐based biosensors in the cell culture medium was probably due to interaction of nonspecific compounds with DA in the culture medium compared to the much less complex environment of PBS. In addition, the regeneration capacity has been found very limited due to inherent heterogeneity and low robustness. This study can be used for the main challenges with the design requirements of commercial SPE‐based biosensors to provide a detailed perspective for further toxicity studies.

Mesenchymal stem cells (MSCs) are multipotent stem cells that can support various tissues including bone marrow, adipose tissue, and synovial fluids, from which they can be readily isolated. The objective of this study is to harness the advantages of microfluidic systems for controlling and enhancing the maintenance and viability, and regenerative properties of MSCs by providing a 3D culture microenvironment with gelatin methacrylate (GelMA) hydrogel and exposing the cells to a slow fluid flow and low shear stress conditions. GelMA has methacryloyl groups and can be crosslinked by a photocuring process using biocompatible photoinitiators. The most common used photoinitiator for cellular encapsulation within hydrogels is the ultraviolet (UV) initiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959 or I2959), but due to its low water solubility and the necessity of using a shorter wavelength light (365 nm), it can lead to cellular phototoxic and genotoxic effects. To overcome these limitations, lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) have recently been used with GelMA as an alternative photoinitiator. Because LAP is highly water soluble and has a 10 times faster polymerization rate, and it requires a visible light (λ = 405 nm) which makes it much safer for the cells, we use 10% GelMA together with 0.05% LAP photoinitiator for bioprinting human adipose tissue derived MSCs (hAT-MSCs) onto a membrane that has a 40 µm mesh size. To demonstrate a microfluidic culture advancement for improving the biological activities and regenerative capacity of the cells including cell adhesion, growth, viability and proliferation capacity as ultimate goals of this study, the membrane carrying the bioprinted construct was placed in a PDMS microchannel and exposed to the fluid to obtain dynamic microenvironments found in the human body. As a result, the cells were successfully maintained in the microfluidic 3D cell culture for two days, with a high cell viability of 99%.

ecently increasing attention has been paid to the development of highly sensitive and selective electrochemical sensors for accurate and cost-effective detection in various fields. In this study, gold nanoparticles (AuNPs) were electro-deposited onto screen printed gold electrode (SPGE) surfaces at different times to determine the optimum modification conditions. Determining the optimum modification for the SPGE surface, AuNP modification under −0.3 V potential with 2 mM HAuCl4 (in 0.5 M H2SO4) solution were investigated. In this case, for the optimum AuNP modification, electrochemical impedance spectroscopy (EIS) analysis was performed at the following deposition times: 30, 60, 90, 120, and 150 s. As a result of modeling the Nyquist graph obtained in the range of 10 kHz to 0.1 Hz with the EIS analysis based on the equivalent circuit model, the outcomes for each modification time were analyzed. After the modification with AuNPs, scanning electron microscope (SEM) images of the SPGE surfaces were discussed. As a result, the optimum deposition time was determined as 90 s by the analysis. This study can be used for electrochemical investigation and target detection in complex media in terms of AuNPs on SPGE surfaces with a detailed perspective for nanoparticle deposition.