Reagent-Free Colorimetric Assay for Galactose Using Agarose Gel Entrapping Nanoceria and Galactose Oxidase

Smartphone-based 3D-printed electrochemiluminescence enzyme biosensor for reagentless glucose quantification in real matrices

Three-dimensional (3D) printed electrochemical devices are increasingly used in point-of-need and point-of-care testing. They show several advantages such as simple fabrication, low cost, fast response, and excellent selectivity and sensitivity in small sample volumes. However, there are only a few examples of analytical devices combining 3D-printed electrodes with electrochemiluminescence (ECL) detection, an electrochemical detection principle widely employed in clinical chemistry analysis. Herein, a portable, 3D-printed miniaturized ECL biosensor for glucose detection has been developed, based on the luminol/H₂O₂ ECL system and employing a two-electrode configuration with carbon black-doped polylactic acid (PLA) electrodes. The ECL emission is obtained by means of a 1.5V AA alkaline battery and detected using a smartphone camera, thus providing easy portability of the analytical platform. The ECL system was successfully applied for sensing H₂O₂ and, upon coupling the luminol/H₂O₂ system with the enzyme glucose oxidase, for glucose detection. The incorporation of luminol and glucose oxidase in an agarose hydrogel matrix allowed to produce ECL devices preloaded with the reagents required for the assay, so that the analysis only required sample addition. The ECL biosensor showed an excellent ability to detect glucose up to 5 mmol L^-1, with a limit of detection of 60 μmol L^-1. The biosensor was also used to analyse real samples (i.e., glucose saline solutions and artificial serum samples) with satisfactory results, thus suggesting its suitability for point-of-care analysis. Coupling with other oxidases could further extend the applicability of this analytical platform.

Colorimetric Nanoparticle-Embedded Hydrogels for a Biosensing Platform

Hydrogels containing colorimetric nanoparticles have been used for ion sensing, glucose detection, and microbial metabolite analyses. In particular, the rapid chemical reaction owing to both the hydrogel form of water retention and the sensitive color change of nanoparticles enables the rapid detection of target substances. Despite this advantage, the poor dispersibility of nanoparticles and the mechanical strength of nanoparticle-hydrogel complexes have limited their application. In this study, we demonstrate a milliliter agarose gel containing homogeneously synthesized polyaniline nanoparticles (PAni-NPs), referred to as PAni-NP-hydrogel complexes (PNHCs). To fabricate the optimal PNHC, we tested various pH solvents based on distilled water and phosphate-buffered saline and studied the colorimetric response of the PNHC with thickness. The colorimetric response of the prepared PNHC to the changes in the pH of the solution demonstrated excellent linearity, suggesting the possibility of using PNHC as a pH sensor. In addition, it was verified that the PNHC could detect minute pH changes caused by the cancer cell metabolites without cytotoxicity. Furthermore, the PNHC can be stably maintained outside water for approximately 12 h without deformation, indicating that it can be used as a disposable patch-type wearable biosensing platform.

Quantitative analysis of galactose using LDI-TOF MS based on a TiO2 nanowire chip

A novel method for quantifying galactose was developed to serve as a newborn screening test for galactosemia using laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry (MS) with a TiO2 nanowire chip. Herein, phosphate citrate buffer, serum, and dried blood spot (DBS) were employed for the quantitative analysis of galactose. To quantitatively analyze galactose, its reduction potential was used to oxidize o-phenylene diamine (OPD) into 2,3-diaminophenazine (DA), which were both detected using LDI-TOF MS with a TiO2 nanowire chip according to the concentration of galactose. The reproducibility and the interference of glucose were determined to demonstrate the applicability of this method. Moreover, mixtures of galactose, phenylalanine, and 17 α-OHP were analyzed to determine the interference induced by other biomarkers of metabolic disorders. The OPD oxidation of galactose was found to be selectively achieved under high-glucose conditions, similar to human blood, thereby showing good reproducibility. The intensities of the mass peaks of OPD and DA based on LDI-TOF MS with a TiO2 nanowire chip were linearly correlated in the galactose concentration range of 57.2–220.0 μg/mL (r2 = 0.999 and 0.950, respectively) for serum samples and 52.5–220.0 μg/mL (r2 = 0.993 and 0.985, respectively) for DBS after methanol precipitation/extraction. The enzyme immunoassay and LDI-TOF MS analysis results were statistically analyzed, and a mixture of phenylalanine, 17 α-OHP, and galactose was simultaneously investigated quantitatively at the cutoff level.

Highly Sensitive Fluorescent Detection of Acetylcholine Based on the Enhanced Peroxidase-Like Activity of Histidine Coated Magnetic Nanoparticles

Inspired by the active site structure of natural horseradish peroxidase having iron as a pivotal element with coordinated histidine residues, we have developed histidine coated magnetic nanoparticles (His@MNPs) with relatively uniform and small sizes (less than 10 nm) through one-pot heat treatment. In comparison to pristine MNPs and other amino acid coated MNPs, His@MNPs exhibited a considerably enhanced peroxidase-imitating activity, approaching 10-fold higher in catalytic reactions. With the high activity, His@MNPs then were exploited to detect the important neurotransmitter acetylcholine. By coupling choline oxidase and acetylcholine esterase with His@MNPs as peroxidase mimics, target choline and acetylcholine were successfully detected via fluorescent mode with high specificity and sensitivity with the limits of detection down to 200 and 100 nM, respectively. The diagnostic capability of the method is demonstrated by analyzing acetylcholine in human blood serum. This study thus demonstrates the potential of utilizing His@MNPs as peroxidase-mimicking nanozymes for detecting important biological and clinical targets with high sensitivity and reliability.

Soft, Biological and Composite Nanomaterials

The progress in the area of nanotechnology has opened the door for the fabrication of soft, biological and composite nanomaterials for targeted applications [...].

Biological Effects of Tricalcium Silicate Nanoparticle-Containing Cement on Stem Cells from Human Exfoliated Deciduous Teeth

Nanomaterials can enhance interactions with stem cells for tissue regeneration. This study aimed to investigate the biological effects of tricalcium silicate nanoparticle-containing cement (Biodentine™) during or after setting on stem cells from human exfoliated deciduous teeth (SHED) to mimic clinically relevant situations in which materials are adapted. Specimens were divided into four groups depending on the start of extraction time (during (3, 6 and 12 min) or after setting (24 h)) and extracted in culture medium for 24 h for further physicochemical and biological analysis. After cell viability in serially diluted extracts was evaluated, odontogenic differentiation on SHED was evaluated by ARS staining using nontoxic conditions. A physicochemical analysis of extracts or specimens indicated different Ca ion content, pH, and surface chemistry among groups, supporting the possibility of different biological functionalities depending on the extraction starting conditions. Compared to the 'after setting' group, all 'during setting' groups showed cytotoxicity on SHED. The during setting groups induced more odontogenic differentiation at the nontoxic concentrations compared to the control. Thus, under clinically simulated extract conditions at nontoxic concentrations, Biodentine™ seemed to be a promising odontoblast differentiating biomaterial that is helpful for dental tissue regeneration. In addition, to simulate clinical situations when nanoparticle-containing cement is adjusted, biological effects during setting need to be considered.