The Characterisation and Quantification of Immobilised Concanavalin A on Quartz Surfaces Based on The Competitive Binding to Glucose and Fluorescent Labelled Dextran

The competition between various carbohydrates in the binding to Concanavalin A (Con A) can be exploited in gravimetric microsensors that detect changes in mass or viscoelasticity as a function of glucose concentration. Such sensors are based on the immobilisation of Con A as the ligand specific element, and a successful application requires that the binding property of Con A is retained. This paper presents a simplified immobilisation procedure of Con A on a quartz surface, a common material for gravimetric microsensors. Structural assessment with atomic force microscopy confirmed that the surface was covered with a layer of macromolecules. This layer shows the presence of entities of various sizes, presumably monomers, dimers and tetramers among which dimers of the Con A are the most dominant structure. Functional assessment using fluorescent labelled dextran (FITC and Alexa 488) suggests a surface coverage ranging from 1.8 × 1011 to 2.1 × 1012 immobilised fluorescent molecules per cm2. The assay was responsive to glucose over a concentration range from 0–40 mM, but became gradually saturated above 20 mM. Hence, the immobilised Con A is able to bind dextran, which is displaced by glucose in a concentration dependent manner, thus triggering a mass change proportional to the MW of dextran

The Characterisation and Quantification of Immobilised Concanavalin A on Quartz Surfaces Based on The Competitive Binding to Glucose and Fluorescent Labelled Dextran

The competition between various carbohydrates in the binding to Concanavalin A (Con A) can be exploited in gravimetric microsensors that detect changes in mass or viscoelasticity as a function of glucose concentration. Such sensors are based on the immobilisation of Con A as the ligand specific element, and a successful application requires that the binding property of Con A is retained. This paper presents a simplified immobilisation procedure of Con A on a quartz surface, a common material for gravimetric microsensors. Structural assessment with atomic force microscopy confirmed that the surface was covered with a layer of macromolecules. This layer shows the presence of entities of various sizes, presumably monomers, dimers and tetramers among which dimers of the Con A are the most dominant structure. Functional assessment using fluorescent labelled dextran (FITC and Alexa 488) suggests a surface coverage ranging from 1.8 × 1011 to 2.1 × 1012 immobilised fluorescent molecules per cm2. The assay was responsive to glucose over a concentration range from 0–40 mM, but became gradually saturated above 20 mM. Hence, the immobilised Con A is able to bind dextran, which is displaced by glucose in a concentration dependent manner, thus triggering a mass change proportional to the MW of dextran

The Characterisation and Quantification of Immobilised Concanavalin A on Quartz Surfaces Based on The Competitive Binding to Glucose and Fluorescent Labelled Dextran

The competition between various carbohydrates in the binding to Concanavalin A (Con A) can be exploited in gravimetric microsensors that detect changes in mass or viscoelasticity as a function of glucose concentration. Such sensors are based on the immobilisation of Con A as the ligand specific element, and a successful application requires that the binding property of Con A is retained. This paper presents a simplified immobilisation procedure of Con A on a quartz surface, a common material for gravimetric microsensors. Structural assessment with atomic force microscopy confirmed that the surface was covered with a layer of macromolecules. This layer shows the presence of entities of various sizes, presumably monomers, dimers and tetramers among which dimers of the Con A are the most dominant structure. Functional assessment using fluorescent labelled dextran (FITC and Alexa 488) suggests a surface coverage ranging from 1.8 × 1011 to 2.1 × 1012 immobilised fluorescent molecules per cm2. The assay was responsive to glucose over a concentration range from 0–40 mM, but became gradually saturated above 20 mM. Hence, the immobilised Con A is able to bind dextran, which is displaced by glucose in a concentration dependent manner, thus triggering a mass change proportional to the MW of dextran

Excitonic light emission decay time measurements in moderately δ-doped GaAs/AlAs multiple quantum wells

The radiative recombination rate of moderately doped n-type and p-type GaAs/AlAs multiple quantum wells using a timecorrelated single photon counting system is presented. The experimental study has been obtained within a wide temperature range from liquid helium to room temperature and the work has focused on identifying photoluminescence decay rates based on freeexciton recombinations. It was found that the free exciton decay time was reduced in doped multiple GaAs/AlAs quantum wells, and that the reduction rate depends on both the concentration and doping type