Selective determination of an ovarian cancer biomarker at low concentrations with surface imprinted nanotube based chemosensor.

In this study, an electrochemical chemosensor that utilizes a conductive polymer-based molecularly imprinted polymer (MIP) surface for rapid and reliable determination of CA125 was devised. A novel method has been applied to fabricate CA125 imprinted polypyrrole nanotubes (MI-PPy NT) via vapor deposition polymerization (VDP) as a recognition element for highly selective and sensitive determination of CA125. The chemosensor was prepared by immobilizing MI-PPy NT onto screen-printed gold electrodes (Au-SPE) and the performance of the sensor was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in terms of selectivity, sensitivity, linear dynamic concentration range (LDR) and limit of detection (LOD). The MI-PPy NT@Au-SPE sensor exhibited high sensitivity (68.57 µA per decade) to the CA125 concentration ranging from 0.1 U mL-1 to 100 U mL-1 at an LOD of 0.4 U mL-1 with a correlation coefficient of 0.9922. The developed chemosensors with their novel design combined with a facile fabrication method, prove to be promising as future state-of-the-art biosensors.

Cross-linked enzyme lyophilisates (CLELs) of urease: A new method to immobilize ureases.

In this study, we presented a new approach for immobilizing JBU (Jack bean urease), by producing urease cross-linked enzyme lyophilisates (CLELs). Through the use of bovine serum albumin (BSA), lyophilisation, cross-linking with dextran polyaldehyde (DPA), and optimizing cross-linker pH, the urease-CLELs produced show an increase in relative catalytic activity that is 1.47 times higher than that of free urease, while remaining stable up to temperatures of 85 °C. Urease-CLEL activity increases in direct proportion with the increasing BSA content due to the offered additional lysine (Lys) groups which are potential cross-linking points providing better immobilization and retention of JBU, while lyophilisation also enables stabilization by eliminating solvating water molecules and intra-molecular reactions that may block the cross-linking residues. Two most commonly used cross-linkers that are reacting with the available Lys groups, i.e.glutaraldehyde (GA) and bulkier alternative DPA, have been selected for the immobilization of urease. The catalytic activity increase with DPA suggests an improved access to the active site through hindering blockage, while the increase with alkaline pH of the cross-linkers indicates decreased buffer inhibition. The long lifetime (113% residual activity after 4 weeks), recyclability (132% residual activity after 10 cycles) and thermal stability (276% relative activity at 85 °C) of these urease-CLELs demonstrate that they are technologically attractive as green biocatalysts, while our immobilization approach offers an alternative to conventional methods for proteins that are difficult to immobilise.