Glucose-selective optical sensors were fabricated by incorporating 3-phenylboronic acid and a tertiary amine, dimethylaminopropylacrylamide, into a hydrogel matrix. Determination of glucose in solution is based on the glucose-induced contraction of the hydrogel. The gel was fabricated on the end of an optical fiber, and the optical length was measured by an interferometric technique. Previously it was found the gel could be tuned for enhanced glucose sensitivity and selectivity by varying the 3-phenylboronic acid/tertiary amine ratio. The properties of the responsive hydrogel as a glucose sensor were determined in more detail with respect to swelling kinetics and equilibrium swelling degree. Temperature effects, size variation, molecular interference, and reversibility were addressed. Results showed there was a good degree of reversibility, both for equilibrium swelling and swelling kinetics. Fabricated hydrogel sensors with slight differences in size yielded an overlapping relative response indicating an excellent degree of sensor reproducibility. The sensor proved to be temperature-dependent; by increasing the temperature from 25 to 37 degrees C, the swelling was about 4-fold more rapid, and a concomitant decrease in equilibrium swelling was seen. Identified interference from other analytes with determination of glucose was used a basis for selecting ethylenediaminetetraacetic acid (EDTA) as an anticoagulant for in vitro determination of glucose concentration in blood plasma. Glucose measurements performed in blood plasma were promising, showing that the sensor is capable of measuring physiological glucose levels in blood with a minimal effect from interfering molecules. The obtained results indicate that the developed sensor is a candidate for continuous monitoring of glucose in blood.

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Phosphatidylethanol (PEth) is an alcohol biomarker formed in the presence of ethanol in the body. Both due to its specificity and because it has a detection window of up to several weeks after alcohol intake, its application potential is broader than for other ethanol biomarkers. The aim of this study was to develop and validate a robust method for PEth in whole blood with fast and efficient sample extraction and a short analytical runtime, suitable for high throughput routine purposes. A validated ultra-performance liquid chromatography tandem mass spectrometry (UPLC®-MSMS) method for quantification of PEth 16:0/18:1 in the range 0.05-4.00 μM (R2 ≥ 0.999) is presented. PEth 16:0/18:1 and the internal standard (IS) PEth-d5 (0.55 μM), were extracted from whole blood (150 μL) by simple protein precipitation with 2-propanol (450 μL). Chromatography was achieved using a BEH-phenyl (2.1 × 30 mm, 1.7 μm) column and a gradient elution combining ammonium formate (5 mM, pH 10.1) and acetonitrile at a flow rate of 0.5 mL/min. Runtime was 2.3 min. The mass spectrometer was monitored in negative mode with multiple reaction monitoring (MRM). The m/z 701.7 > 255.2 and 701.7 > 281.3 transitions were monitored for PEth 16:0/18:1 and the m/z 706.7 > 255.3 for PEth-d5. Limit of quantification was 0.03 μM (coefficient of variation, CV = 6.7%, accuracy = 99.3%). Within-assay and between-assay imprecision were 0.4-3.3% (CV ≤ 7.1%). Recoveries were 95-102% (CV ≤ 4.9%). Matrix effects after IS correction ranged from 107% to 112%. PEth 16:0/18:1 in patient samples were stable for several days at 30°C. Repeated freezing (-80°C) and thawing did not affect the concentration. After thawing and analysis patient samples were stable at 4-8°C for at least 4 weeks. Results from a proficiency test program, showing |Z| values ≤1.2, confirm the validity of the method. Analysis of the first 3,169 samples sent to our laboratory for routine use has demonstrated its properties as a robust method suitable for high throughput purposes.

We present a novel fiber-optic biosensor utilizing hydrogel functionalized with enzyme sensitive cross-links. A proof-of-concept PSA sensor demonstrated linear response up to 4 µM and sensitivity better than 40 nM, with time response of 2 minutes.