Electronic tongue for simultaneous detection of endotoxins and other contaminants of microbiological origin.

Endotoxins, also referred to as pyrogens, are lipopolysaccharides (LPS) present in the outer membrane of Gram-negative bacteria, and represent one of the most dangerous microbiological contaminants in water for hemodialysis and intravenous infusion. A method is presented for the simultaneous detection of endotoxins and other bacterial lysis contaminating species in purified water for parenteral formulations. The technique used is electrochemical impedance spectroscopy, with data interpretation using principal component analysis (PCA), cluster analysis (CA), and multivariate discriminant analysis (MDA). Two types of electrode surfaces were modified with LPS recognition agents: (i) a 37 amino acids fragment of a 18 kDa cationic antimicrobial protein (CAP18F) that has LPS binding activity; (ii) the highly selective endotoxin neutralizing protein (ENP). Statistical multivariate analysis of the impedance spectral data allowed the detection of endotoxin at, and below, the threshold pharmaceutical regulatory level. Discrimination of LPS from samples containing proteins, nucleic acids, phospholipids or their mixtures was achieved. These results open a new route to a practical instrumental method capable of detecting and discriminating LPS from other potential pro-inflammatory species of microbiological origin, such as nucleic acids.