Immobilization of Candida antarctica Lipase B on Silicone Nanofilaments

Candida antarctica lipase B was immobilized on a series of silicone nanofilament-coated matrices of different porosities. In addition to creating a more open surface, SNF’s hydrophobicity allows for a simple immobilization pathway via adsorption. In order to study the impact of the nanostructure, the performance was compared with control samples lacking SNFs. For all materials, the surface was characterized with BET measurements, and the immobilized enzyme was measured as well as the catalytic activity. Enzyme loads ranged between 3.85% w / w and 2.53% w / w and decreased with the decreasing surface area of the carrier material from 200 m2/g to 0.04 m2/g, while the activity per enzyme increases from 824 U to 2040 U. The data suggest that the coating seals off inner surfaces, forcing the enzyme to be immobilized at more accessible positions allowing for higher activity per enzyme. Optimization of the immobilization conditions allowed us to create a thinner enzyme layer which further improved the activity per enzyme to 3129 U. While this activity is comparable to the commercial Novozyme 435 with 3073 U, the SNF-based system performs the catalysis in a thin surface layer of around 13 μm. A favorite area of application is, for example, the creation of enzyme-based detection systems, where the high activity per surface area of up to 89622 U · mg/m2 would lead to high signal strength.

Development and Optimization of a Glucose Biosensor Based on Tris [5-amino-1,10-Phenanthroline]Iron(II) Polymer Films

A bilayered glucose biosensor consisting of tris[5-amino-1, 10-phenanthroline]iron(II) polymer film redox mediator and a glucose oxidase layer was prepared on glassy carbon surfaces. The polymer film of the iron complex was immobilized onto the electrode using cyclic voltammetry via electropolymerization reactions, while the enzyme layer was formed using a BSA and glutaraldehyde crosslinking reaction. The biosensors gave the largest response in the pH range of 7-8 and were evaluated with respect to storage conditions of room temperature and 4oC. There was no significant difference between the detection of glucose using the biosensor stored at room temperature versus one stored at 4°C and both bilayered films remained active for 20 days. The detection limit of the biosensors was found to be 0.30 mM which corresponds to a signal to noise ratio of 3:1.

Biocatalytic Activity of Glucose Oxidase Immobilized on Functionalized Supports for Enzymatic Biosensors

The present study reports on a novel approach for the development of enzymatic biosensor systems using chemically functionalized supports. Silica glass slides were surface-modified by reacting with organosilanes at room temperature and a glucose oxidase (GOx) enzyme layer was covalently immobilized using the bi-functional linker glutaraldehyde (GA). The activities of enzymes in solution and immobilized on hydroxyl-, amine-and thiol-modified glass surfaces were tested by sensing β-D-glucose with the horseradish peroxidase (HRP) mediated oxidation of 3,3’,5,5’-tetramethylbenzidime hydrochloride (TMB) by H2O2based on biochemical reactions. The results indicated that the intensity and overall kinetics of the enzymatic catalysis were dependent on solid support chemical functionality with the amine-modified support providing the highest enzymatic catalytic activity.

Quantitative Analysis Of Performance Of A Hydrogen Peroxide–Based Glucose Biosensor

Satu biosensor glukosa separa telah dibina menggunakan satu lapisan dalaman yang selektif, satu lapisan enzim dan satu elektrod emas. Kedua–dua lapisan membran tersebut adalah berasaskan polivinil alcohol (PVA) tersambung silang. Prestasi biosensor glukosa tersebut telah dinilai terutamanya prestasi terhadap gangguan asetaminofen, yang merupakan molekul tak ionik. Sensitiviti enzim tersekat gerak tersebut terhadap glukosa adalah tinggi tetapi ianya tidak mencukupi untuk melawan gangguan asetaminofen. Kehadiran lapisan dalaman PVA yang hanya sederhana selektif tidak menyebabkan kesan yang ketara pada gangguan. Satu model matematik kemudiannya digunakan untuk menganalisis prestasi biosensor yang lengkap. Satu lapisan luar ditambah secara simulasi kepada dua lapisan terdahulu. Model matematik tersebut meramalkan bahawa penambahan satu lapisan luar yang mempunyai kebolehtelapan yang rendah terhadap bahan larut mampu memperbaiki prestasi sensor. Kata kunci: Biosensor glukosa; model matematik; asetaminofen; gangguan elektrokimia; polivinil alkohol tersambung silang A partial glucose biosensor was constructed using a selective internal layer, an enzyme layer and a gold electrode. Both membrane layers are based on cross–linked polyvinyl alcohol (PVA). The performance of the partial glucose biosensor was analyzed particularly with respect to the interfering effects of acetaminophen, a non–ionic molecule. The sensitivity of the immobilized enzyme to glucose was high but it was not high enough to counter acetaminophen interference. The addition of the moderately selective PVA internal layer did not seem to have a significant effect on interference. A mathematical model was then used to analyze the performance of a completed biosensor. A simulated external layer was added to the two layers. The mathematical model predicted that the addition of an external layer with lowered permeability to solutes could improve the performance of the sensor. Key words: Glucose biosensor; mathematical modeling; acetaminophen; electrochemical interference; cross-linked polyvinyl alcohol

Construction of Reagentless Biosensor Based on Self-Assembly and Electrodeposition for Determination of Hydrogen Peroxide

A general methodology to prepare reagentless biosensor was developed based on self-assembly and electrodeposition. Redox active inorganic multilayers consisting of copper hexacyanoferrate (CuHCF) multilayers were formed by successive self-assembly. A simple and controllable electrodeposition approach was established for one-step fabrication of chitosan-enzyme layer on CuHCF modified electrode. Horseradish peroxidase was selected as the model enzyme. With CuHCF as the electroactive mediator, the developed reagentless biosensor exhibited a fast amperometric response for the determination of hydrogen peroxide (H2O2). The linear response ranged from 1.4 × 10-5 to 2.0 × 10-4 M with a detection limit of 1.2 × 10-6 M. The biosensor exhibited high reproducibility and long-time storage stability. The proposed methodology could serve as a versatile platform for fabrication of electrochemical biosensors.

Amperometrinių biojutiklių su sinerginių substratų stiprinimu kompiuterinis modeliavimas

Šiame straipsnyje yra tiriamas amperometrinis biojutiklis, kuriame biojutiklio atsakas yra stiprinamas chemiškai – sinerginiais substratais. Tokiuose biojutikliuose, be substrato, kurio koncentracija matuojama, naudojamas ir pagalbinis substratas, reikalingas substratų sinergetikai. Biojutiklis yra modeliuojamas naudojant nestacionarias netiesines reakcijos-difuzijos lygtis. Modeliuojami keturi biojutiklio sluoksniai: fermento sluoksnis, kuriame vyksta visos biocheminės reakcijos ir difuzija, dializėsmembrana ir difuzijos sluoksnis, kuriuose vyksta tik difuzija ir reakcijos, kuriose nedalyvauja fermentas, o ketvirtasis sluoksnis yra tirpalo dalis, kurioje palaikoma vienoda medžiagų koncentracija. Lygčių sistema sprendžiama skaitiškai, naudojant baigtinių skirtumų metodą. Tiriama biojutiklio atsako bei jautrio priklausomybė nuo substratų koncentracijų ir nuo difuzijos sluoksnio storio.Modelling Amperometric Biosensors with Synergistic Substrate AmplificationDainius Šimelevičius, Romas Baronas SummaryComputational modelling of a biosensor in which chemical amplification by synergistic substrates takes place was investigated in this study. In the biosensors of this type, in addition to the substrate (analyte), another auxiliary substrate is used. It is necessary to achieve the substrates synergy. The operation of the biosensor is modelled using non-stationary reactiondiffusion equations. The model involves four regions: the enzyme layer where the enzymatic reactions as well as the mass transport by diffusion take place, the dialysis membrane and the diffusion limiting region where the mass transport by diffusion and non-enzymatic reactions take place, and the convective region in which the analyte concentration is maintained constant. The equation system is solved numerically using the finite difference technique. The biosensor response dependency on substrate concentrations and the diffusion layer thickness, as well as the biosensor sensitivity dependence on the same parameters have been studied."line-height: 18px;">

Kompiuterinis optinio biojutiklio savybių tyrimas taikant bedimensį modelį

Šiame darbe, siekiant nustatyti pagrindinius kinetinius peroksidazinio optinio biojutiklio matematinio modelio parametrus, buvo sudarytas bedimensis modelis. Biojutikliui taikomos reakcijos-difuzijos lygtys su netiesiniu nariu, aprašančiu fermentinę reakciją. Biojutiklio veikimas modeliuojamas fermento ir difuzijos sluoksniuose. Ištirta biojutiklio atsako ir jautrio priklausomybė nuo bedimensio biojutiklio modulio. Suformuluotas uždavinys sprendžiamas baigtinių skirtumų metodu. Gauti rezultatai pagrindžia šio modelio pritaikomumą. Atliekami peroksidazinio optinio biojutiklio eksperimentiniai tyrimai leis nustatyti modelio taikymo ribas.A Computational Investigation of the Optical Biosensor by a Dimensionless ModelEvelina Gaidamauskaitė, Romas Baronas SummaryIn order to determine the main governing parameters, a dimensionless mathematical model of a peroxidase-based optical biosensor is derived. The mathematical model of the biosensor is based on a system of non-linear reaction-diffusion equations. The modelled biosensor comprises two compartments, an enzyme layer and an outer diffusion layer. The influence of the dimensionless diffusion modulus on the biosensor response and the sensitivity is investigated. The digital simulation was carried out using a finite difference method.