Development of glucose biosensors using nanostructured composites

Developing a biosensor capable of measuring glucose and other whole blood analytes for monitoring diabetes has been a major challenge for over four decades. In this thesis, an attempt has been made to develop three different novel metallophthalocyanine-based (MPcs) biosensors for this purpose. Three novel enzymatic biosensors have been fabricated to monitor glucose concentration and other whole blood analytes in vitro. The first fabricated biosensor is based on conducting multifunctional hydrogel (PAA-rGO/VS-PANI/LuPc2/GOx-MFH) utilising reduced graphene oxide (rGO) and lutetium phthalocyanine (LuPc2) dissolved in chloroform to produce three-dimensional (3D) matrix as platform to enhance the sensing performance. Utilising the aqueous properties of a novel water-soluble iron phthalocyanine (FePc) derivative on the other hand, added more simplicity for the fabrication process of another biosensor (PAA-CP/GPL-FePc/GOx-CH) for enzymatic detection of glucose. Graphene nanoplatelets (GPL) have been attached non-covalently to the FePc resulting in a conducting hydrogel-based platform (CH). A third novel bioprobe (SiO2(LuPc2)-PANI(PVIA)/GOx-CNB) based on silica nanoparticles (SiO2) grafted polyaniline (PANI) has formed a conducting nanobeads (CNB)-based biosensor. The latter is employed as an enzymatic biosensor platform for the detection of glucose with enhanced sensitivity. Full characterisation has been carried out for all the raw studied materials as well as prepared biosensing platforms. UV-Visible and FT-IR spectroscopies as well as SEM, TEM, XRD, and EDX have been employed in order to help gaining full understanding of the nature and properties of the studied materials. The electrochemical properties of the newly developed biosensing platforms have been fully studied using common analytical methods such as cyclic voltammetry (CV), amperometry, and electrochemical impedance spectroscopy (EIS). The freeze dry system alongside the Brunauer-Emmett-Teller (BET) method were employed to characterise the surface area of the produced platforms. The sensitivity of MFH biosensor studied in the range 2-12 mM of glucose is found to fall in the region of 15.31 μA mM−1 cm−2 with low detection limit of 25 μM. The biosensor based on CH platform exhibited a broad linear behaviour when glucose in the range 1-20 mM is studied, with high sensitivity of 18.11 μA mM−1 cm−2 and low detection limit of 1.1503 ng/mL. The conducting nanobeads-based biosensor (CNB) has led to a further improvement the sensitivity of glucose detection (38.53 μA mM−1 cm−2) with wide linear range of 1-16 mM and detection limit of 0.1 mM. All three biosensing platforms have exhibited excellent selectivity when examined against whole blood components

Gold Nanocage-Based Electrochemical Sensing Platform for Sensitive Detection of Luteolin

A simple and sensitive electrochemical sensor was developed for the detection of tracelevels of luteolin. The sensoris based on a novel type of chemically modified electrode: gold nanocage (AuNCs)-modified carbon ionic liquid electrode (CILE). To construct this electrochemical sensing platform for luteolin, CILE is initially prepared by using 1-hexylpyridinium hexafluorophosphate as the binder and then AuNCs are coated on the surface of CILE to fabricate AuNCs-modified CILE (AuNCs/CILE). Electrochemical studies have shown that AuNCs/CILE can exhibit enhanced electrocatalytic activity toward the redox reaction of luteolin, therefore, the redox peak current of luteolin can be greatly improved, resulting in the high sensitivity of the developed sensor. Under the optimal conditions, the oxidation peak currents of the sensor increase linearly with an increase in the luteolin concentration in a range from 1 to 1000 nM with a detection limit of 0.4 nM, which is lower than those of most reported electrochemical luteolin sensors. Moreover, the reproducibility, precision, selectivity, and stability of this sensor are excellent. Finally, the sensing system was applied to the analysis of luteolin-spiked drug samples and the recovery in all cases was 95.0–96.7%, indicating the potential application of this simple, facile, and sensitive sensing system in pharmaceutical analysis