Design and characterization of conductive biopolymer nanocomposite electrodes for medical applications

Metal-based electrodes, despite being the most widely used for biomedical applications, are limited by a poor reliable skin-surface interface and patients suffer from comfort issues. The most common problems/inconveniences are caused by stiff electrodes, skin irritation, allergic reaction or corrosion. In order to overcome these problems, we produced and tested flexible electrodes involving biopolymer nanocomposite materials. Conductive polymers have been intensively studied and applied in the field of organic photovoltaics and flexible organic electronics. Recently, the use of conductive biopolymer nanocomposite has also emerged as an interesting and promising material for biomedical applications. In this study, we have designed and characterized electrodes made of a flexible and conductive nanocomposite material using a biocompatible and biodegradable polymeric matrix of poly (3- hydroxyalkanoate) (PHA, in particular poly (3-hydroxybutyrate), PHB) containing conductive nanowires. The biopolymer nanocomposites and their electrical conductivities were investigated by optical microscopy, scanning electron microscopy (SEM) and electrical four-point probing. The electrical conductivities obtained in the different PHA-polymer nanocomposites containing different concentrations of conductive additives is discussed in relation to the nanocomposite structure at the microscopic level. Finally, our developed biopolymer nanocomposite prototype electrodes have successfully been tested for transcutaneous electrical nerve stimulation (TENS) and electrocardiography ECG applications in comparison to conventional electrodes

Novel RP-HPLC based assay for selective and sensitive endotoxin quantification

The paper presents a novel instrumental analytical endotoxin quantification assay. It uses common analytical laboratory equipment (HPLC-FLD) and allows quantifying endotoxins (ETs) in different matrices from about 109 EU / mL down to about 40 EU / mL (RSE based). Test results are obtained in concentration units (e.g. ng ET / mL), which can then be converted to commonly used endotoxin units (EU / mL) in case of known pyrogenic activity. During endotoxin hydrolysis, the endotoxin specific rare sugar acid KDO is obtained quantitatively. After that, KDO is stoichiometrically reacted with DMB, which results in a highly fluorescent derivative. The mixture is separated using RP-HPLC followed by KDO-DMB quantification with a fluorescence detector. Based on the KDO content, the endotoxin content in the sample is calculated. The developed assay is economic and has a small error. Its applicability was demonstrated in applied research. ETs were quantified in purified bacterial biopolymers, which were produced by Gram-negative bacteria. Results were compared to LAL results obtained for the same samples. A high correlation was found between the results of both methods. Further, the new assay was utilized with high success during the development of novel endotoxin specific depth filters, which allow efficient, economic and sustainable ET removal during DSP. Those examples demonstrate that the new assay has the potential to complement the animal-based biological LAL pyrogenic quantification tests, which are accepted today by the major health authorities worldwide for the release of commercial pharmaceutical products