Glucose In Body Fluids Research Articles

Liquid Chromatography with Orbitrap High-Resolution Mass Spectrometry for the Determination of Glucose in Saliva Following Derivatization with Dibenzylamine

As an important circulating metabolite in the body, the accurate determination of glucose in body fluids is very important for the evaluation of physiological status. However, liquid chromatography–mass spectrometry (LC–MS) methods present challenges for glucose due to poor ionization combined with weak chromatographic retention. Here, a method for determining salivary glucose using LC–MS after derivation by dibenzylamine is described in which 3-O-methyl-D-glucopyranose was used as internal standard. Saliva samples were prepared by protein precipitation, and the analytes were separated on a polar-copolymerized C18 reversed phase column. Detection took place by high-resolution orbitrap mass spectrometry after ionization in the positive mode. The calibration function was linear from 0.35 to 50 ng/mL. The recoveries were from 97.82 to 104.51% for intraday assays and 98.96 to 106.61% for interday assays. The intraday precision of salivary glucose was from 0.37% to 1.43% and the interday precision from 1.33% to 1.43%. The limits of detection and quantification in saliva were 0.2 and 0.6 ng/mL. The samples after derivatization were stored at 4 °C and 25 °C and analyzed every two days with five repeats. The relative standard deviations were 0.09% and 0.27% at 4 °C and 25 °C. This method was employed for the determination of the glucose in saliva for healthy male college students after exercise.

Smart Contact Lens for Colorimetric Visualization of Glucose Levels in the Body Fluid.

Frequent blood glucose monitoring is a crucial routine for diabetic patients. Traditional invasive methods can cause discomfort and pain and even pose a risk of infection. As a result, researchers have been exploring noninvasive techniques. However, a limited number of products have been developed for the market due to their high cost. In this study, we developed a low-cost, highly accessible, and noninvasive contact lens-based glucose monitoring system. We functionalized the surface of the contact lens with boronic acid, which has a strong but reversible binding affinity to glucose. To achieve facile conjugation of boronic acid, we utilized a functional coating layer called poly(tannic acid). The functionalized contact lens binds to glucose in body fluids (e.g., tear) and releases it when soaked in an enzymatic cocktail, allowing for the glucose level to be quantified through a colorimetric assay. Importantly, the transparency and oxygen permeability of the contact lens, which are crucial for practical use, were maintained after functionalization, and the lenses showed high biocompatibility. Based on the analysis of colorimetric data generated by the smartphone application and ultraviolet-visible (UV-vis) spectra, we believe that this contact lens has a high potential to be used as a smart diagnostic tool for monitoring and managing blood glucose levels.

Ultra‐Sensitive and Unlabeled SERS Nanosheets for Specific Identification of Glucose in Body Fluids

AbstractThe detection of biomolecules utilizing surface‐enhanced Raman spectroscopy (SERS) is highly trending in research, but the unlabeled and sensitive detection of saccharides in body fluids is challenging. Here, a novel SERS substrate (AgNS600) is fabricated by physical scratching of smooth silver sheets, which successfully achieves enhanced SERS fingerprinting by capturing glucose molecules through nanoscale grooves on the surface of the substrate to form multi‐dimensional “hot spot” regions. The platform proves to be rapid, reliable, and reproducible, with a lower detection limit of 0.5 amol L−1 in deionized water. Further detection of multiple monosaccharides, polysaccharides, and mix samples, which are distinguished with machine learning and heat map, demonstrates the versatility and specificity of the platform. Importantly, real samples are explored and the results show that the platform is able to detect and recognize SERS signals of glucose in the blood, urine, tears, and perspiration, and non‐destructive predict diabetes by analyzing the signal intensity of different characteristic peaks. In this work, it is the first non‐chemical, unlabeled determination of glucose with high sensitivity via SERS, which provides a potential strategy for advancing the clinical development of SERS technology and the early diagnosis of glucose metabolic diseases.

In situ synthesis copper phosphate-protein hybrid nanoflower on nickel foam for the sensitive detection of glucose in body fluids

We have synthesized copper phosphate-protein hybrid heterostructure nanoflowers (Cu(II)-HNFs) in situ on nickel foam for the first time. The interaction between protein and copper ions facilitated the nucleation growth of copper phosphate crystals and self-assembly of hybrid nanosheets into exquisite flower-like nanostructures. The unique high-specific surface structure of Cu(II)-HNFs provided high-density catalytically active sites for copper phosphate. Also, the direct growth of Cu(II)-HNFs on the NiF surface enhanced the electron transfer efficiency during catalysis. As a result, Cu(II)-HNFs exhibit an excellent electrocatalytic efficacy in glucose sensing. Including wide linear range of 0.1-3000 μM, high sensitivity of 2497.1 μA mM−1 cm−2, ultra-low detection limit of 0.03 μM, good selectivity, and stability. Moreover, Cu(II)-HNFs@NiF has been validated as a reliable tool for detecting glucose in urine samples, with recoveries ranging from 92.9 % to 101.9 %. These findings demonstrate that the developed Cu(II)-HNFs@NiF has immense potential for non-invasive glucose monitoring through body fluids.

Chameleon-inspired multifunctional plasmonic nanoplatforms for biosensing applications

One of the most fascinating areas in the field of smart biopolymers is biomolecule sensing. Accordingly, multifunctional biomimetic, biocompatible, and stimuli-responsive materials based on hydrogels have attracted much interest. Within this framework, the design of nanostructured materials that do not require any external energy source is beneficial for developing a platform for sensing glucose in body fluids. In this article, we report the realization and application of an innovative platform consisting of two outer layers of a nanocomposite plasmonic hydrogel plus one inner layer of electrospun mat fabricated by electrospinning, where the outer layers exploit photoinitiated free radical polymerization, obtaining a compact and stable device. Inspired by the exceptional features of chameleon skin, plasmonic silver nanocubes are embedded into a poly(N-isopropylacrylamide)-based hydrogel network to obtain enhanced thermoresponsive and antibacterial properties. The introduction of an electrospun mat creates a compatible environment for the homogeneous hydrogel coating while imparting excellent mechanical and structural properties to the final system. Chemical, morphological, and optical characterizations were performed to investigate the structure of the layers and the multifunctional platform. The synergetic effect of the nanostructured system’s photothermal responsivity and antibacterial properties was evaluated. The sensing features associated with the optical properties of silver nanocubes revealed that the proposed multifunctional system is a promising candidate for glucose-sensing applications.

Flexible Nonenzymatic Glucose Sensing with One‐Step Laser‐Fabricated Cu2O/Cu Porous Structure

Integrated flexible nonenzymatic electrochemical glucose sensors have attracted substantial interest because they enable portable noninvasive glucose detection stably and accurately. Manufacturing of these sensors generally requires complex step‐by‐step processes, including synthesis of noble and functional materials, patterning the as‐synthesized noble materials into electrodes/contacts, and subsequent working electrode functionalizing. Herein, the one‐step fabrication of a working electrode and electrical contacts on a flexible substrate for an integrated sensor is realized through laser writing of a low‐cost Cu ionic precursor. The obtained Cu2O/Cu porous structure not only has a low sheet resistance of 1.3 Ω sq−1 to ensure signal transmission in the sensor, but also provides a remarkable sensing performance for glucose detection, especially at a low detection potential of 0.3 V and a low detection limit of 0.34 μm. Due to its anti‐interference and flexibility, the integrated sensor has the potential to directly detect trace amounts of glucose in body fluids as demonstrated in sweat sensing. This work highlights an efficient route to fabricate low‐cost integrated flexible electrochemical sensors.

Glucose-triggered in situ forming keratin hydrogel for the treatment of diabetic wounds

The development of protein-based in situ forming hydrogel remains a big challenge due to the limited chemical groups in proteins. Keratins are a group of cysteine-rich structural protein found abundant in skin and skin appendant. Recently, our lab has established a disulfide shuffling strategy to prepare keratin hydrogels via oxygen (O2) oxidation. However, such hydrogel still needed to be molded in advance. In this work, inspired by the fact that glucose commonly exists in body fluids, a glucose-triggered in situ forming keratin hydrogel was developed based on the disulfide shuffling strategy via a higher oxidation force of hydrogen peroxide (H2O2). The hydrogel precursor solution consisted of keratin, cysteine and glucose oxidase (GOD), which could generate H2O2 in an indirect and mild way via GOD-catalyzed oxidation of glucose in body fluids. Our findings demonstrated that the GOD-catalyzed oxidation method not only shortened the gelation time but improved the mechanical strength of the hydrogel by comparison with O2 oxidation and direct addition of H2O2 solution methods, and realized in situ gelation within 3 min on a full-thickness wound bed in normal mice. Moreover, the in situ forming keratin hydrogel was applied as a drug depot for wound repair, and the deferoxamine-loaded one accelerated healing in the full-thickness wounds of streptozotocin-induced diabetic rats, notably by promoting angiogenesis and neovascularization in wounds. Statement of SignificanceStudies show that keratin hydrogels possess tissue regeneration capacity, especially in skin wound repair. However, most of the reported keratin hydrogels needed to be molded in advance and cannot fit irregular wound shape. This work describes a glucose-triggered in situ forming keratin hydrogel via a disulfide shuffling strategy under the oxidation of hydrogen peroxide. Of note, the hydrogen peroxide was supplied indirectly by glucose oxidase-catalyzed oxidation of glucose in wound fluids, and this method needed no additional crosslinking agents or chemical modifications on keratins. Our findings showed that this hydrogel realized in situ gelation within 3 min on a full-thickness wound bed and enabled an injectable mode with good filling ability toward irregular wounds. Moreover, this hydrogel could be applied as a drug depot for the treatment of diabetic wounds.

Correction: Novel enzyme-functionalized covalent organic frameworks for the colorimetric sensing of glucose in body fluids and drinks

Correction for ‘Novel enzyme-functionalized covalent organic frameworks for the colorimetric sensing of glucose in body fluids and drinks’ by Jie-Yu Yue et al., Mater. Chem. Front., 2021, 5, 3859–3866, DOI: 10.1039/D1QM00314C.

Novel enzyme-functionalized covalent organic frameworks for the colorimetric sensing of glucose in body fluids and drinks

Covalent organic frameworks (COFs) are promising platforms for use in enzyme immobilization.

A Portable Smartphone-based Platform with an Offline Image-processing Tool for the Rapid Paper-based Colorimetric Detection of Glucose in Artificial Saliva.

In this study, a microfluidic paper-based analytical device (μPAD) was integrated with a smartphone app capable of offline (without internet access) image processing and analysis for the rapid colorimetric detection of glucose. A self-inking stamp was used to form hydrophobic channels on a piece of paper-towel due to its superior water absorption efficiency. As demonstrated, the developed sensor was employed for the colorimetric detection of glucose in artificial saliva in the linear scope of 0 - 1 mM with a calculated detection limit of 29.65 μM. The experimental results show that the quantitative analysis of glucose with the proposed smartphone platform could be completed in less than one minute. The app developed for the smartphone platform is capable of extracting the color-changing area with an embedded image processing tool which could address the problem of color uniformity in the detection zones of μPAD. The integrated platform has great potential to be used for non-invasive measurements of glucose in body fluids, like tears, sweat and saliva.

Docking Linear Ligands to Glucose Oxidase

GOX (3QVR), glucose oxidase, is an oxidoreductase enzyme, which has found many applications in biotechnology and modern diagnostics with typical assays including biosensors useful in the determination of free glucose in body fluids. PEI (polyethylenimines) are polymer molecules made up of amine groups and two aliphatic carbons, which are cyclically repeated. PEI are transfection reagents which, using positively charged units, bind well to anionic DNA residues. During the studies on GOX, PEI were used both in their linear and branched structures. Rhombellanes, RBL, are structures decorated with rhombs/squares. The aim of the paper is to study the interactions of two kinds of linear ligands: PEIs (Polyethylenimines) and CHRs (ethers of Hexahydroxy-cyclohexane) with the glucose oxidase enzyme, GOX (3QVR). To understand the structure-activity relationship between the GOX enzyme and the linear ligands PEI and CHR, two steps of docking simulation were performed; mapping the whole area of the 3QVR enzyme and docking on the first and second surface of the enzyme, separately. The studied ligands interacted with amino acids of GOX inside the protein and on its surface, with stronger and shorter bonds inside of the protein. However, long chain ligands can only interact with amino acids on the external protein surface. After the study, two domains of the enzyme were clearly evidenced; the external surface domain more easily creates interactions with ligands, particularly with CHR ligands.

Direct Immobilization of Glucose Oxidase on the Hydrophilic Copolymer Support Containing Oxirane

Glucose oxidase (GOD) (EC 1.1.3.4) is an oxido-reductase that catalyses the oxidation action of glucose to hydrogen peroxide and D-glucono-δ-lactone [. GOD is widely used in the determination of free glucose in body fluids, in vegetal raw material and in the food industry [. It also has many applications in biotechnologies, typically enzyme assays for biochemistry including biosensors in nanotechnologies. Free GOD will be denatured and inactivated rapidly due to its structural instability under extreme pH or temperature [. Four immobilizing methods, including physical adsorption, covalent binding, crosslinking and embedding methods, were used to improve their economic feasibility. Covalent binding combined active functional group monomers of carriers onto enzymes [4-. Researches showed that oxirane groups can react with-NH2 and-HS of enzymes under mild conditions so that the enzyme molecules were immobilized on the copolymer support containing oxirane [.

Preparation of chitosan/glucose oxidase nanolayered films for electrode modification by the technique of layer-by-layer self-assembly

Enzyme immobilization onto the electrode surface is a critical step in assembling amperometric biosensors. Recently, layer-by-layer (LBL) techniques have been developed for the immobilization of enzyme on various matrices [1, 2]. The multilayer films of various proteins alternating with synthetic or natural polyanions and polycations were prepared to fabricate biosensors by this novel technique [3–10]. The glucose oxidase is widely used for the detection of glucose in body fluids and in removing residual glucose and oxygen from beverages and foodstuffs. The glucose oxidase (β-D-glucose: oxygen 1-oxidoreductase, EC1.1.3.4) catalyses the oxidation of β-D-glucose to D-glucono1,5-lactone and hydrogen peroxide, using molecular oxygen as the electron acceptor (as Fig. 1 shows). The chitosan, an N-deacetylated derivative of chitin, is a naturally occurring biopolymer found in the exoskeleton of crustaceans, in fungal cell walls, and in other biological materials [11]. It has an unusual combination of properties [12], which includes excellent membrane-forming ability towards water, good adhesion, nontoxicity, high mechanical strength, especially good biocompatibility and susceptibility to chemical modification due to the presence of reactive amino and hydroxyl functional groups. In recent years, the artificial polyelectrolytes have mainly been used to immobilize various enzymes by LBL techniques [13]. Chitosan was generally used to immobilize various enzymes by techniques such as sol-gel [14], crosslinking [15] etc. The LBL techniques could control the enzyme loading by changing the adsorption cycles with fewer side effects on glucose oxidase while the chitosan was used for preparing LBL films, which was expected to be an alternative method for the chitosan to immobilize glucose oxidase. In this paper, we report the first attempt to prepare chitosan/GOx nanolayered films for electrode modification by the technique of layer-by-layer selfassembly. In situ gravimetric measurement of quartz crystal microbalance (QCM, QCA917, EG&G) was applied to investigate the assembly process. An AFM (Nanoscope IIIa, Digital Instruments) was used to characterize the surface morphology. The electrochemical

Electrocatalytic determination of glucose in a Ringer's solution by pulse-voltammetry.

Improvement of the electrocatalytic method of glucose determination was achieved by applying the pulse voltammetry technique. This technique, compared. to previously applied cyclic voltammetry, enhances selectivity of a platinum-black working electrode for glucose measurement. A low catalytic load working electrode has been used which is less susceptible to poisoning and has longer term stability. With cyclic voltammetry previously applied, those electrodes were limited by their narrow concentration range for glucose detection. By applying a pulsing technique, these electrodes exhibit linearity up to a glucose concentration 200 mg/dl with correlation coefficients greater than 0.9. The pulse voltammetry diminishes interference by low molecular weight serum components such as serum urea. Concentrations from 20. to 40 mg/di had an interference of 4 percent compared to 40 percent with cyclic voltammetry. Further investigations are carried on to adopt pulse voltammetry for direct measurements of glucose in body fluids.

Quantitative method for the detection of glucose in body fluids by high-performance liquid chromatography with fluorescence detection

Quantitative method for the detection of glucose in body fluids by high-performance liquid chromatography with fluorescence detection

Development and present status of an electrocatalytic glucose sensor.

For the determination of glucose in body fluids the electrocatalytic sensor seems to be quite favorable, particularly for long-term intracorporeal operation. The measuring response is disturbed by the fluctuating concentrations of interfering substances that are present in body fluids. However, the disturbance can be for the most part controlled, as shown in the case of amino acids. Their marked influence on glucose oxidation is suppressed at a membrane-covered sensor electrode by using a potential step method.

A rapid and specific method for the estimation of glucose using an oxygen electrode and simple differentiating circuit

A simple differentiating circuit is described which, together with an oxygen electrode assembly, provides a rapid (20 sec) and cheap system for the estimation of glucose in body fluids using a sample volume of 20 μl. Response was linear over the range 0–22 mmol/1. The complete system has been evaluated using plasma and whole blood. “Within-day” precision on control plasmas over the concentration range 2.73–8.33 mmol/1 lies between 2.0 and 3.3% (C.V., n = 23); “day-to-day” precision was 4.6% (C.V., n = 23). On whole blood, to which nitrite had been added, precision was 4.5% (C.V., n = 15); precision using standard glucose solutions was never greater than 3.3% (C.V., n = 15) over the concentration range 1.1–22.2 mmol/1. Recoveries of added glucose to plasma and whole blood were greater than 90%. Good correlation between glucose values obtained by the oxygen electrode system described here and an automated system were obtained for plasma ( r = 0.9902, n = 35) and whole blood ( r = 0.9610, n = 35), although whole blood gave values on average 27% lower than plasma. The use of the system for the measurement of plasma cholesterol is also demonstrated.

Biochemical and physiological studies of certain ticks (Ixodoidea). The sugar content and concentration in Argas and Hyalomma biological fluids.

Following engorgement, glucose was the only circulating sugar in the hemolymph of Argas (Persicargas) persicus (Oken) and A. (P.) arboreus Kaiser, Hoogstraal & Kohls (♂, ♀, N2,N3.) (family Argasidae) and of Hyalomma (H.) dromedarii Koch and H. (H.) anatolicum excavatum Koch (♀) (family Ixodidae). Trehalose was absent. Body fluid glucose concentrations were higher in Hyalomma ticks than in rabbit host plasma but lower in Argas ticks than in pigeon host plasma. Argas coxal fluid glucose concentrations were much higher than those in Hyalomma pilocarpine-stimulated oral secretion, possibly indicating a difference in the efficiency of the 2 concentration systems or in specific requirements for this sugar.

A simple automated determination of glucose in body fluids using an aqueous o-toluidine-acetic acid reagent

An automated method for use with continuous flow systems is presented for the determination of glucose in deproteinized blood, urine or other body fluids. In the deproteinized samples, which can be stored for 24 h without alteration in their glucose values, the glucose content is determined using an o-toluidine-acetic acid reagent containing 40% of water. The sensitivity of the reagent is considerably raised by increasing the percentage of o-toluidine and by the addition of borax. These changes do not affect the high degree of specificity of the o-toluidine reaction for glucose. Dextran products do not give rise to falsely high values as has been the case with other o-toluidine-acetic acid reagents. Beer's law is obeyed up to a concentration of at least 30 mmoles/1. In routine use the method gives a standard deviation of 0.16 mmole/1 and a coefficient of variation of 2.8%. The improvements result in an effective, easily handled glucose reagent that is only moderately aggressive and lends itself both to automated and manual procedures.