A nonenzymic microfiber optic-biosensor modified phenylboric acid for sensitively and specifically detecting low glucose concentration

A microfiber interferometer coated with sensitive films formed by amide bond between 3-Carboxy-4-fluorophenylboronic acid (FPBA) and polydopamine (PDA) for the detection of trace glucose concentration is designed and demonstrated. Due to a huge evanescent field, this microfiber interferometer has a very sensitive response to the refractive index (RI) of the surrounding environment, which has excellent sensing performance including RI sensitivity response of 1825.83 nm/RIU and low temperature response of -0.04 nm/°C. Due to the good film-forming performance of PDA, whose the amino group coupled with the carboxyl molecule on FPBA to form an amide bond, PDA/FPBA can be attached to the microfiber interferometer for detecting different concentrations of glucose. The concentration range of glucose detection is 0.1-20 mM with a sensitivity of 1.71 nm/mM and a limit of detection of 12.6 ppm. Finally, the sensor is tested in actual samples of human urine to detect different concentrations of glucose and proved to be responsive and reproducible in urine. We can estimate the concentration of glucose in urine by wavelength shift. The sensor has the advantages of simple manufacture, low cost, high sensitivity, and specific recognition glucose in urine. In addition, the success of this sensor shows that the combination of ultrafine fiber and organic chemical materials has broad prospects in the field of optical detection.

Effect of carbon and nitrogen concentrations on lipid accumulation and regulation of acetyl-CoA carboxylase in Papiliotrema laurentii

Biodiesel is an interesting alternative to petroleum diesel as it is renewable, biodegradable, and has a low pollutant content. Yeast oils can be used for biodiesel production instead of edible oils, mitigating the use of arable land and water for biodiesel production. Maximum lipid accumulation is reached at 48 h of cultivation by the oleaginous yeast Papiliotrema laurentii UFV-1. Nevertheless, the effects of carbon and nitrogen concentrations on lipid accumulation, as well as the regulation of lipid metabolism in this yeast are still not well-characterised. Therefore, this work evaluated the effects of carbon and nitrogen concentrations on the lipid accumulation in P. laurentti, the expression of the ACC gene, and the activity of the enzyme acetyl-CoA carboxylase (ACCase) in different carbon:nitrogen ratios (C:N) and glucose concentrations. The variation of ammonium sulfate concentration did not affect the growth and lipid accumulation in P. laurentii UFV-1. On the other hand, glucose concentration remarkably influenced biomass and lipid production by this yeast. Therefore, the carbon concentration is more important than the nitrogen concentration for lipid production by P. laurentii UFV-1. Importantly, the levels of both ACC gene expression and ACCase activity were maximum during the late-exponential growth phase and decreased after reaching the highest lipid contents, which was easier evidenced during the accumulation and maximum lipid levels. As such, the reduction of ACCase enzyme activity seems to be related to the decrease in the expression level of the ACC gene.

HyfF subunit of hydrogenase 4 is crucial for regulating FOF1 dependent proton/potassium fluxes during fermentation of various concentrations of glucose

Escherichia coli anaerobically ferment glucose and perform proton/potassium exchange at pH 7.5. The role of hyf (hydrogenase 4) subunits (HyfBDF) in sensing different concentrations of glucose (2 g L^-1 or 8 g L^-1) via regulating H⁺/K⁺ exchange was studied. HyfB, HyfD and HyfF part of a protein family of NADH-ubiquinone oxidoreductase ND2, ND4 and ND5 subunits is predicted to operate as proton pump. Specific growth rate was optimal in wild type and mutants grown on 2 g L^-1 glucose reaching ~ 0.8 h^-1. It was shown that in wild type cells proton but not potassium fluxes were stimulated ~ 1.7 fold reaching up to 1.95 mmol/min when cells were grown in the presence of 8 g L^-1 glucose. Interestingly, cells grown on peptone only had similar proton/potassium fluxes as grown on 2 g L^-1glucose. H⁺/K⁺ fluxes of the cells grown on 2 g L^-1 but not 8 g L^-1 glucose depend on externally added glucose concentration in the assays. DCCD-sensitive H⁺ fluxes were tripled and K⁺ fluxes doubled in wild type cells grown on 8 g L^-1 glucose compared to 2 g L^-1 when in the assays 2 g L^-1glucose was added. Interestingly, in hyfF mutant when cells were grown on 2 g L^-1glucose and in 2 g L^-1 assays DCCD-sensitive fluxes were not determined compared to wild type while in hyfD mutant it was doubled reaching up to 0.657 mmol/min. In hyf mutants DCCD-sensitive K⁺ fluxes were stimulated in hyfD and hyfF mutants compared to wild type but depend on external glucose concentration. DCCD-sensitive H⁺/K⁺ ratio was equal to ~ 2 except hyfF mutant grown and assayed on 2 g L^-1glucose while in 8 g L^-1 conditions role of hyfB and hyfD is considered. Taken together it can be concluded that Hyd-4 subunits (HyfBDF) play key role in sensing glucose concentration for regulation of DCCD-sensitive H⁺/K⁺ fluxes for maintaining proton motive force generation.

The effect of disinfecting procedure on the glucose concentration using a personal glucose meter

BACKGROUND

Personal glucose meters, primarily designed for self-control of glucose concentration in patients with diabetes, are frequently used in clinical practice as point-of-care equipment. The procedure of washing hands with water and soap before testing, as recommended by the manufacturer of personal glucose meters, in hospital wards is often difficult to fulfil and is replaced by disinfecting the place of blood sampling with isopropyl alcohol.

AIM

The purpose of the research was to evaluate the effect of different disinfecting procedures on glycemia measurement in capillary blood using personal glucose meters.

MATERIALS AND METHODS

Four measurements of glycemia were taken in each of 50-volunteer group using Accu-Check Performa (Roche, Swiss) glucose meter using different procedures: washing hands with soap and drying them (1), disinfection with isopropyl alcohol and waiting for the disinfectant to evaporate (2) and the immediate puncture after disinfection. In the latter case two kind of single-use lancets were use - typical for adult (3) and smaller preferred by diabetics or children (4).

RESULTS

Paired T-student test showed no statistically significant difference between measurements 1st and 2nd 95% CI (-4.282 to 0.322), p = 0.09. However, the comparison between 1st/3rd and 1st/4th showed statistically significant difference, 95% CI (-4.964 to -0.796), p = 0,0077 (p < 0,01) and 95% CI (-7.842 to -2.917), p = 0.00006 (p < 0.001).

CONCLUSIONS

The procedure of disinfection when fluid completely evaporates has no effect on glucose measurements. Sampling the wet finger influences results of glucose measurement but observed changes were clinically irrelevant.

Accuracy of differences in blood and peritoneal glucose to differentiate between septic and non-septic peritonitis in horses

Difference in blood and peritoneal glucose (DBPG) is used in clinical practice to support a diagnosis of septic peritonitis in horses. It is inexpensive, easy and rapid to perform. The aim of this study was to evaluate the accuracy of the DBPG to differentiate between septic and non-septic peritonitis in horses. Blood and peritoneal fluids were harvested from suspected animals. Plasma and peritoneal glucose levels, total nucleated cell count, direct microscopic and microbiological examinations of the peritoneal fluid were evaluated. Using DBPG levels, the animals were classified into two groups: difference ≥ 50 mg/dL (positive test) and difference < 50 mg/dL (negative test). Positive microbiological examination and/or presence of bacteria in direct microscopic examination was used as a gold standard to detect septic peritonitis. The accuracy parameters analysed were: sensitivity, specificity, and positive/negative predictive values, for which the results were respectively: 0.23, 0.91, 0.60 and 0.67. Due to poor accuracy, other cut-off margins and peritoneal glucose concentrations were evaluated. The test was considered most accurate when the DBPG was zero with sensitivity, specificity, and positive/negative predictive values of 0.85, 0.82, 0.73, 0.90 respectively. Peritoneal glucose concentrations alone were not a reliable feature to detect peritonitis. DBPG ≥50 mg/dL, widely used for the diagnosis of septic peritonitis, does not have a good accuracy and the DBPG = 0 has a better accuracy for detecting the disease.

Comparative study on different pretreatment on enzymatic hydrolysis of corncob residues

Under the situation of increasingly severe challenge of energy consumption, it is of great importance to make full use of bioresources such as forestry and agricultural residues. Herein, the corncob residues generated after processing corncob were enzymatically hydrolyzed to yield fermentable sugars. To overcome the recalcitrance of corncob residues, three kinds of pretreatment methods, i.e., sulfonation, PFI refining, and wet grinding, were applied; their effects on enzymatic hydrolysis and main characteristics of corncob residues substrate were investigated. The results showed that the enzymatic digestibility of the substrate was greatly enhanced by employing each method. The wet grinding exhibited obvious advantages, e.g., the conversion yield of cellulose to glucose and glucose concentration reached 96.7% and 32.2 g/L after 59 h of enzymatic hydrolysis, respectively. The improvement in enzymatic hydrolysis was mainly attributed to the altered characteristics of the substrate such as swelling ability, specific surface area, and particle size and distribution.

The rise in glucose concentration in saliva samples mixed with test foods monitored using a glucometer: An observational pilot study

OBJECTIVES

The aim of this study was to quantify the changes in glucose concentration in unstimulated saliva samples mixed with finely crushed salted sticks or oat meal using a readily available portable glucometer.

METHODS

Glucose measurements were taken every 10 min during a 1 h monitoring period, for a total of 14 saliva samples mixed with test foods. Salivary amylase activity was measured immediately after saliva collection (T0) and after 1h (T60). Level of salivary amylase activity was correlated with an increase in glucose concentration.

RESULTS

We observed significant differences in the rate of increase in glucose concentration between the two different test foods, with salted sticks leading to greater increase in glucose concentration. No significant association was found between salivary amylase activity and the rate of increase in glucose concentration. The mean level of amylase activity at T60 was higher than that at T0, but this difference was not significant.

CONCLUSIONS

This pilot study presents glucose release rate characteristics from specific food particles mixed with saliva in vitro suggesting that the same process takes place in the oral cavity. However, the characteristics of this process when occurring in the mouth would expectedly be modified by different factors such as rinsing effect of salivary flow, oral temperature, etc. Prolonged release of low molecular carbohydrates such as maltose and glucose from food particles can be considered cariogenic and therefore unfavorable for individuals with other risk factors contributing to the development of dental caries.

Microwave sensor for the investigation of glucose-dependent reflection properties in aqueous samples

The reported paper presents the development of a microwave sensor with a resonant frequency 2.4 GHz. The sensor is also demonstrated in vitro to investigate the variation in its response as a function of glucose concentration. The sensor could be used for the monitoring of blood glucose level in diabetics through non-invasive technology. The approach followed is based on the notion that, change in glucose concentration in the blood affects dielectric properties of blood which in turn produce an impact on reflection properties of the sensor. This effect on response of sensor will be ultimately used to estimate blood glucose concentration. The design specifications considered for the development of sensor are defined in the paper. The experimental setup for in vitro experiment and procedure employed for the investigation of the reflection properties of the sensor as a function of glucose concentration are also discussed in detail. The shift in resonance frequency and the change in the magnitude of the reflection coefficient of proposed sensor have been observed. The reported measurement results are the preliminary results in exploring the implementation of proposed sensor for non-invasive blood glucose monitoring.

The effects of oxygen level and glucose concentration on the metabolism of porcine TMJ disc cells

OBJECTIVE

To determine the combined effect of oxygen level and glucose concentration on cell viability, ATP production, and matrix synthesis of temporomandibular joint (TMJ) disc cells.

DESIGN

TMJ disc cells were isolated from pigs aged 6-8 months and cultured in a monolayer. Cell cultures were preconditioned for 48 h with 0, 1.5, 5, or 25 mM glucose DMEM under 1%, 5%, 10%, or 21% O2 level, respectively. The cell viability was measured using the WST-1 assay. ATP production was determined using the Luciferin-Luciferase assay. Collagen and proteoglycan synthesis were determined by measuring the incorporation of [2, 3-(3)H] proline and [(35)S] sulfate into the cells, respectively.

RESULTS

TMJ disc cell viability significantly decreased (P < 0.0001) without glucose. With glucose present, decreased oxygen levels significantly increased viability (P < 0.0001), while a decrease in glucose concentration significantly decreased viability (P < 0.0001). With glucose present, decreasing oxygen levels significantly reduced ATP production (P < 0.0001) and matrix synthesis (P < 0.0001). A decreased glucose concentration significantly decreased collagen synthesis (P < 0.0001). The interaction between glucose and oxygen was significant in regards to cell viability (P < 0.0001), ATP production (P = 0.00015), and collagen (P = 0.0002) and proteoglycan synthesis (P < 0.0001).

CONCLUSIONS

Although both glucose and oxygen are important, glucose is the limiting nutrient for TMJ disc cell survival. At low oxygen levels, the production of ATP, collagen, and proteoglycan are severely inhibited. These results suggest that steeper nutrient gradients may exist in the TMJ disc and it may be vulnerable to pathological events that impede nutrient supply.