Fiber-optic glucose biosensor based on glucose oxidase immobilised in a silica gel matrix

A monolithic silica gel matrix with entrapped glucose oxidase was constructed as a bioactive element in an optical biosensor for glucose determination. Physicochemical and biochemical characterizations of the catalytic matrix were performed, and the intrinsic fluorescence of immobilised glucose oxidase (GOD) was investigated in the UV and visible range by performing steady state and time course measurements. In all cases, the silica gel matrix proved to be a suitable support for optical biosensing owing to its superior optical properties (e.g., high transmittance and reliable fluorescence and GOD absorption spectra after immobilisation). From steady state measurements, calibration curves were obtained as a function of glucose concentration. When time course measurements were performed, the silica gel support displayed a larger linear calibration range and higher sensitivity than other immobilisation systems. In addition, a glucose optical biosensor was developed and characterised using as catalytic element GOD immobilised on a gel disk bound to a bundle of optical fibres.     

Glucose concentration determination based on silica sol-gel encapsulated glucose oxidase optical biosensor arrays

Optical biosensor arrays for rapidly determining the glucose concentrations in a large number of beverage and blood samples were developed by immobilizing glucose oxidase (GOD) on oxygen sensor layer. Glucose oxidase was first encapsulated in silica based gels through sol-gel approach and then immobilized on 96-well microarrays integrated with oxygen sensing film at the bottom. The oxygen sensing film was made of an organically modified silica film (ORMOSIL) doped with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium dichloride (Ru(dpp)₃Cl₂). The oxidation reaction of glucose by glucose oxidase could be monitored through fluorescence intensity enhancement due to the oxygen consumption in the reaction. The luminescence changing rate evaluated by the dynamic transient method (DTM) was correlated with the glucose concentration with the wide linear range from 0.1 to 5.0 mM (Y = 13.28X − 0.128, R = 0.9968) and low detection limit (0.06 mM). The effects of pH and coexisting ions were systemically studied. The results showed that the optical biosensor arrays worked under a wide range of pH value, and normal interfering species such as Na⁺, K⁺, Cl⁻, PO₄³⁻, and ascorbic acid did not cause apparent interference on the measurement. The activity of glucose oxidase was mostly retained even after 2-month storage, indicating their long-term stability.     

Effect of hyaluronic acid encapsulation in a silica hydrogel matrix on drug penetration through the skin

It has been found that the encapsulation of high molecular weight hyaluronic acid in a biologically relevant silica hydrogel matrix provides its accelerated penetration into the skin compared to free acid. The developed hybrid hydrogels, in which high molecular weight hyaluronic acid retains its pronounced anti-inflammatory properties and strong hydrating effect, can become the basis for new, more effective soft formlations for the treatment of inflammatory skin diseases, as well as for products used in the beauty industry. It has been shown that the penetration of hyaluronic acid from the hybrid hydrogels depends on the conditions of their synthesis, the average molecular weight and the loading of the acid.     

Diffusion of protons in silica hydrogel

The effect of preparation pH of silica hydrogel on the effective diffusion coefficient of protons in silica hydrogel (D _e , m²/s), on surface area of silica gel (S, m²/s) and on particle size of silica gel (D _p , mm) was studied. Silica hydrosols were obtained by adding water glass to sulfuric acid. The effective diffusion coefficient of proton in silica hydrogel was determined by the method of diffusion from silica hydrogel plane sheet to a stirred solution of a limited volume. A numerical solution was obtained for the diffusion equation using the Regula Falsi method. Regression analyses of experimental data were conducted.Diffusion of protons in silica hydrogel is a complicated process due to a decelerating effect of the porous structure of silica hydrogel and to the accelerating effects of slow ions such as Na⁺ and surface diffusion. The effective diffusion coefficient increased with surface area of silica gel, indicating the diffusion of protons on the surface of the silica particles.     

The influence of non-rubber constituents on performance of silica reinforced natural rubber compounds

An in-rubber study of the interaction of silica with proteins present in natural rubber show that the latter compete with the silane coupling agent during the silanisation reaction; the presence of proteins makes the silane less efficient for improving dispersion and filler–polymer coupling, and thus influences the final properties of the rubber negatively. Furthermore, the protein content influences the rheological properties as well as filler–filler and filler–polymer interactions. Stress strain properties also vary with protein content, as do dynamic properties. With high amounts of proteins present in natural rubber, the interactions between proteins and silica are able to disrupt the silica–silica network and improve silica dispersion. High amounts of proteins reduce the thermal sensitivity of the filler–polymer network formation. The effect of proteins is most pronounced when no silane is used, but they are not able to replace a coupling agent.     

Synthesis and lectin-binding activity of luminescent silica particles peripherally functionalized with lactose

A novel O-protected lactose (Galβ1→4Glcβ1-) derivative bearing trimethoxysilyl group at the aglycon was developed as a silane coupling agent. Reaction of the coupling agent with tris(2,2′-bipyridine)ruthenium (II) dichloride (Rubpy) doped silica particle gave a Rubpy-doped silica particle peripherally functionalized with O-protected lactose derivative. De-O-protection of the particle with aqueous ammonia provided lactose-coating Rubpy-doped silica particles, combining luminophor encapsulated in silica matrix and carbohydrate having lectin-recognition ability. Specific adhesion of fluorescein isothiocyanate-labeled peanut agglutinin (FITC-PNA) to the lactose-coating Rubpy-doped silica particles was confirmed by fluorescence microscopic analysis.     

基于溶胶-凝壳聚糖/SiO2杂化材料的安培型葡萄糖生物传感器

近年来 ,基于溶胶 -凝胶技术的有机 /无机杂化复合材料由于具有有机物的柔性和易修饰性 ,以及无机物的刚性和稳定性等 ,因此有利于保持生物分子的活性和生物传感器的研制 [1] .壳聚糖 ( CS)具有易成膜性和生物相容性 ,其在生物传感器中的研究已受到重视 [2 ] .本文通过原位溶胶 -凝胶 ( Sol- gel)技术 ,用 CS和甲基三甲氧基硅烷 ( MTOS)制备了 CS/Si O2 有机 /无机杂化材料 ,并将其用于对葡萄糖氧化酶 ( GOD)的固定 ,研制出葡萄糖生物传感器 .采用人工过氧化物酶普鲁士蓝 ( PB) [3]作为电子传递的媒介体 ,并外加一层 Nafion膜以增强…     

New approach to the immobilization of glucose oxidase on non-porous silica microspheres functionalized by (3-aminopropyl)trimethoxysilane (APTMS)

The immobilization and encapsulation of glucose oxidase (GOD) onto the mesoporous and the non-porous silica spheres prepared by co-condensation of tetraethylorthosilicate (TEOS) and (3-aminopropyl)trimethoxysilane (APTMS) in the water-in-oil (W/O) emulsion system were studied. The terminal amine group was used as the important functionality for GOD immobilization on the silica substrate. When only TEOS is used as a silica source, the disordered mesoporous silica microspheres are obtained. As the molar ratio of APTMS to TEOS (R_AT) increases, the surface area and pore volume of the silica particles measured by nitrogen adsorption and desorption method and SEM decrease rapidly. Particularly, the largest change of the surface morphology is observed between R_AT = 0.20 and R_AT = 0.25. The amount and the adsorption time of immobilized enzyme were measured by UV spectroscopy. About 20 wt% of GOD was immobilized into the silica substrates above R_AT = 0.60 and was completely adsorbed into the substrate of R_AT = 0.80 with lapse of 4 h after addition. In the measurement of the thermal stability, GOD dissolved in buffer solution loses nearly all of its activity after 30 min at 65 °C. In contrast, GOD immobilized on the surface-modified silica particles still retains about 90% of its activity after the same treatment. At this temperature, the immobilized glucose oxidase retained half of its initial activity after 4 h. It is shown that the suitable usage of functionalizing agent like APTMS as well as the control of surface morphology is very important on the immobilization of enzyme.     

An integrated micropump and electrospray emitter system based on porous silica monoliths

The work presents the design of an integrated system consisting of a high-pressure electroosmotic (EO) micropump and a microporous monolithic emitter, which together generate a stable and robust electrospray. Both the micropump and electrospray emitter are fabricated using a sol-gel process. Upon application of an electric potential of sufficient amplitude (>2 kV), the pump delivers fluids with an electroosmotically induced high pressure (>1 atm). The same potential is also harnessed to electrostatically generate a stable electrospray at the porous emitter. Electrokinetic coupling between pump and spray produces spray features different from sprays pressurized by independent mechanical pumps. Four typical spray modes, each with different drop sizes and charge-to-mass ratios, are observed and have been characterized. Since the monolith is silica-based, this integrated device can be used for a variety of fluids, especially organic solvents, without the swelling and shrinking problems that are commonly encountered for polymer monoliths. The maximum pressure generated by a 100 microm id monolithic pump is 3 atm at an applied voltage of 5 kV. The flow rate can be adjusted in the range of 100 nL/min to 1 microL/min by changing the voltage. For a given applied voltage across the pump and emitter system, it is seen that there exists one unique flow rate for which flow balance is achieved between the delivery of liquid to the emitter by the pump and the liquid ejection from the emitter. Under such a condition, a stable Taylor cone is obtained. The principles that lead to these results are also discussed.     

Immobilization of Glucose Oxidase and 2-Hydroxybiphenyl 3-Monooxygenase in Mesoporous Silica: Characterization Studies and Construction of an Amperometric Glucose Biosensor

Immobilization techniques that preserve the activity of biomolecules have many potential applications. Mesoporous silica has been used to encapsulate a wide variety of biomolecules. In this particular work, MCM-41 silica has been used as a matrix for the immobilization of two important enzymes, HpbA and GOx. The enzyme 2-hydroxybiphenyl 3-monooxygenase (HpbA) is involved in the microbial degradation of 2-hydroxy and 2,2′-dihydroxybiphenyl, which occurs during the desulfurization of coal and petroleum, while Glucose oxidase (GOx) catalyzes the oxidation of β-D-glucose to δ-gluconolactone. The silica-enzyme hybrids were extensively characterized and the one with GOx was used for the construction of a biosensor.     

新型葡萄糖氧化酶电极用于临床血糖的测定

在稳定的普鲁士蓝修饰电极上先涂一酶层 ,然后将二氧化硅溶胶 -凝胶薄膜敷着其上用于固定酶 ,制成了葡萄糖氧化酶电极。采用恒电位安培检测 ,葡萄糖浓度在0.05～4.75mmol/L范围内与响应电流成线性关系 ,检出限为0.02mmol/L ,灵敏度高达1.182μA·mmol -1·L ,响应时间为12s ;该酶电极不受抗坏血酸、尿酸等电活性物质的干扰 ,稳定性较好。该电极用于临床血糖的测定 ,回收率为96 %～110 % ,测定结果与酶偶联比色法结果一致 ,可用于临床糖尿病人血糖的检测。     

Chelating sorbents based on silica gel and their application in atomic spectrometry

This mini-review covers chelating sorbents anchored to silica gel and their analytical applications for the preconcentration, separation and determination of trace metal ions, focussing mainly on the last 20 years. The article summarizes also the experience gathered by our research group in the synthesis and characterization of new modified silica gels via silanization, and their affinity toward selective extraction and separation of trace elements. The introduction of 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide silica gel (DPTH-gel) and methylthiosalicylate silica gel (TS-gel) chelating sorbents in trace and ultratrace analysis provide vital breakthroughs in preconcentration methods. These home-made materials allow certain analytes to be selectively extracted from complex matrices without matrix interference and good detection limits. The advantages of these new chelating sorbents in comparison with 8-hydroxyquinoline chelating sorbent immobilized on silica gel are discussed.     

Nonisocyanate based polyurethane/silica nanocomposites and their coating performance

A series of silica nano-particles with different size were prepared by sol–gel technique, then surface modification by using cyclic carbonate functional organoalkoxysilane (CPS) was performed. Various amounts of carbonated silica particles directly added into carbonated soybean oil (CSBO) and carbonated polypropylene glycol (CPPG) resin mixture to prepare polyurethane–silica nanocomposite coating compositions by nonisocyanate route using an aliphatic diamine as a curing agent. Cupping, gloss, impact, and taber abrasion tests were performed on aluminum panels coated with those nano-composite formulations and tensile tests, thermogravimetric and SEM analyses were conducted on the free films prepared from the same coating formulations. An increase in abrasion resistance of CSBO-CPPG resin combination with the addition of silica was observed. In addition, the maximum weight loss of CSBO-CPPG resin combination was shifted to higher temperatures with incorporation of silica nano-particles The positive effect of modified silica particles on thermal stability of CSBO-CPPG system could be explained in such a way that PPG chains are able to disperse particles in the medium throughout the interactions between ether linkages and silanol groups.     

蜘蛛丝素和聚乙烯醇固定葡萄糖氧化酶 制备葡萄糖传感器

用蜘蛛丝素和聚乙烯醇的混合材料把葡萄糖氧化酶固定在氧电极表面,制成葡萄糖氧化酶电极。传感器对葡萄糖有灵敏的响应,平均响应时间为20s,电位变化值与葡萄糖浓度在3.0×10     

A novel positively thermo-sensitive hydrogel based on ethylenediaminetetraacetic dianhydride and piperazine: Design, synthesis and characterization

A new positively thermo-sensitive hydrogel was designed and synthesized by a condensation polymerization reaction of ethylenediaminetetraacetic dianhydride（EDTAD） and piperazine（PA） to give poly（ethylenediaminetetraacetic dianhydride-copiperazine） （PEP）.The obtained polymers’ structure was characterized by FTIR and ¹³C NMR.The backbone of the polymer linked by amide bond and abundant of carboxyl groups as pendant group could form strong intermolecular and intramolecular hydrogen bond at lower temperature and dissociate at higher temperature,resulting in the polymer with thermo-sensitivity.The aqueous solution of PEP at lower temperature（<20℃） showed micro-gel formation and transformed to transparent solution at higher temperature（>40℃）.Transition temperature shifted to higher value with the increasing of concentration.The hydrogel exhibited reversible phase transition and the transmittance change was not weakened by multiple temperature changes.     

Glucose sensor based on redox-cycling between selectively modified and unmodified combs of carbon interdigitated array nanoelectrodes

We present a novel electrochemical glucose sensor employing an interdigitated array (IDA) of 1:1 aspect ratio carbon nanoelectrodes for the electrochemical-enzymatic redox cycling of redox species (ferricyanide/ferrocyanide) between glucose oxidase (GOx) and the two comb-shaped nanoelectrodes of the IDA. The carbon nanoelectrodes were fabricated using a simple, cost-effective, reproducible microfabrication technology known as the carbon-microelectromechanical-systems (C-MEMS) process. One comb (comb 1) of the IDA was selectively modified with GOx via the electrochemical reduction of an aryl diazonium salt, while the other comb (comb 2) remained unmodified; this facilitates electrochemically more active surface of comb 2, resulting in sensitive glucose detection. Ferricyanide is reduced to ferrocyanide by the GOx in the presence of glucose, and ferrocyanide diffuses to both combs of the IDA where it is oxidized. The limited electrochemical current collection at the surface-modified comb 1 is counterbalanced by the efficient redox cycling between the enzyme sites at comb 1 and the bare carbon surface of comb 2. Reducing the electrode-to-electrode gap between the two combs (gap = 1.9 μm) increases the diffusion flux of redox species at comb 2 hence, enhanced the sensitivity and limit of detection of the glucose sensor by ∼2.3 and ∼295 times, respectively at comb 2 compared to comb 1. The developed IDA-based glucose sensor demonstrated good amperometric response to glucose, affording two linear ranges from 0.001 to 1 mM and from 1 to 10 mM, with limits of detection of 0.4 and 61 μM and sensitivities of 823.2 and 70.0 μA mM⁻¹ cm⁻², respectively.     

基于金属有机框架水凝胶的一步式快速富集检测养殖水体中孔雀石绿北大核心CSCD

孔雀石绿是一种三苯甲烷类化合物,在水产品饲养中对疾病的防治有着不错的疗效,但因对人体健康有危害而被列为禁用药。由于实际样品中成分复杂,对于此类染料的检测方法难以同时兼具富集性好、灵敏度高且方便快速的优点。该工作制备了金属有机框架材料(MOF),采用MOF纳米材料掺杂的水凝胶(PAAM-SA/MOF)对养殖水体中的孔雀石绿进行吸附研究。采用一系列表征手段对MOF、PAAM-SA和PAAM-SA/MOF的微观形貌进行分析,结果表明吸附材料已成功合成。通过优化水凝胶吸附剂用量、吸附时间、孔雀石绿溶液pH、吸附温度、孔雀石绿溶液初始浓度等吸附萃取条件,使溶液中的孔雀石绿基本完全吸附在水凝胶中,在最优条件下,吸附效率最高可达97%。此外,采用不同极性的有机溶剂对吸附的孔雀石绿进行洗脱,通过优化洗脱液体积,脱附率最高达99%。在最佳条件下,该方法在高、中、低3个水平下的样品加标回收试验中回收率达到84.8%~118.1%,相对标准偏差小于5.1%,方法的检出限为0.083μg/L(S/N=3),定量限为0.25μg/L(S/N=10)。该方法简化了前处理过程,结合了MOF和水凝胶这二者各自的优点,添加的MOF材料可以在水凝胶体系中发挥其良好的吸附性,既解决了传统的MOF材料因粒径太小而回收率低的难题,便于吸附后直接提取,同时也解决了纯水凝胶吸附效率较低的问题,整体上提高了吸附效率和可回收性。实际样品测试表明该新型水凝胶吸附材料可用于养殖水体中孔雀石绿的快速萃取和检测,在食品检测领域具有很大潜力。     

Glucose biosensors based on the immobilization of copper oxide and glucose oxidase within a carbon paste matrix

The performance of amperometric glucose biosensors based on the dispersion of glucose oxidase (GOx) and copper oxide within a classical carbon (graphite) paste composite is reported in this work. Copper oxide promotes an excellent electrocatalytic activity towards the oxidation and reduction of hydrogen peroxide, allowing a large decrease in the oxidation and reduction overpotentials, as well as an important enhancement of the corresponding currents. Therefore, it is possible to perform the glucose biosensing at low potentials where there is no interference even in large excess of ascorbic acid, uric acid or acetaminophen. The influence of the copper oxide and glucose oxidase content in the paste on the analytical performance of the bioelectrode is discussed. The resulting biosensor shows a fast response, a linear relationship between current and glucose concentration up to 1.35 × 10⁻² M (2.43 g L⁻¹) and a detection limit of 2.0 × 10⁻⁵ M. The effect of the presence of the enzyme in the composite material on the dispersion of the copper oxide particles is also discussed.     

硅溶胶改性及其应用研究进展

二氧化硅在自然界中通常为晶态,而以溶胶-凝胶、水热、模板剂等方法人工合成的二氧化硅纳米颗粒(SiO₂ NPs)通常为无定形态。无定形SiO₂ NPs广泛应用于航空航天、催化剂载体、靶向送药等众多高端领域。生产SiO₂ NPs的方法有很多,但制备结构、形貌简单的SiO₂ NPs的主要方式为离子交换法、硅醇盐水解法、单质硅粉水解法,这些方法可制备粒径在10～800 nm的单分散SiO₂ NPs,同时可根据生产条件控制粒子的单分散性与粒径大小。寻找一种成本低廉且成品单分散性好、粒径可控的生产方法成为目前研究的热点。本文简介了SiO₂ NPs的结构形貌、基础性质、生产方法和最佳合成条件,总结了各方法的优缺点与适用领域。随后介绍了近年来SiO₂ NPs的改性研究与应用,最后在此基础上展望了合成硅溶胶存在的挑战与未来需解决的问题。     

Direct Electrochemistry of Glucose Oxidase on Nail‐like Carbon and Its Biosensing for Glucose

Nail‐like carbon (NLC) was synthesized by a simple hydrothermal method. It was the first time that a novel electrochemical biosensing of glucose was explored based on the glucose oxidase (GOx)‐NLC‐chitosan (CHIT) glassy carbon electrode. Morphology and structure of NLC were characterized by scanning electron microscope; meanwhile the chemical composition was determined by X‐ray diffraction and energy dispersive X‐ray spectroscopy. The cyclic voltammetry of immobilized GOx showed a pair of quasireversible redox peaks with the formal potential (E°′) of ?0.458 V and the peak‐to‐peak potential separation was 47 mV at a scan rate of 100 mV s^?1. The present biosensor has a linear range of glucose from 0.02 to 1.84 mM (correlation coefficient of 0.9991) and detection limit of 0.01 mM (S/N=3). Compared with the previous reports based on the carbon material biosensor, it has a high sensitivity of 165.5 μA mM^?1 cm^?2 and low apparent Michaelis–Menten constant of 0.506 mM. Thus, the NLC may have potential applications in the field of bioelectrochemistry, bioelectronics and biofuels.