Lothar Müller

Mechanistic study of fluoride ion sensors

Fluoride ion sensitive semiconductor sensors were investigated with regard to the influence of pH, the limit of detection obtained and the response time. The results are the same as those obtained for a well-known single crystal electrode. The dissolution rate of LaF3 was determined using the isotope 140La. The OH–/F– exchange reaction and the isotope exchange kinetics of fluoride ions between the solution and the sensor layer were investigated. In the pH range from 4 to 8 it could be concluded that both the limit of detection and the response time are determined by the ion-exchange rate.

NCO-sP(EO-stat-PO) Coatings on Gold Sensors—a QCM Study of Hemocompatibility

The reliability of implantable blood sensors is often hampered by unspecific adsorption of plasma proteins and blood cells. This not only leads to a loss of sensor signal over time, but can also result in undesired host vs. graft reactions. Within this study we evaluated the hemocompatibility of isocyanate conjugated star shaped polytheylene oxide—polypropylene oxide co-polymers NCO-sP(EO-stat-PO) when applied to gold surfaces as an auspicious coating material for gold sputtered blood contacting sensors. Quartz crystal microbalance (QCM) sensors were coated with ultrathin NCO-sP(EO-stat-PO) films and compared with uncoated gold sensors. Protein resistance was assessed by QCM measurements with fibrinogen solution and platelet poor plasma (PPP), followed by quantification of fibrinogen adsorption. Hemocompatibility was tested by incubation with human platelet rich plasma (PRP). Thrombin antithrombin-III complex (TAT), β-thromboglobulin (β-TG) and platelet factor 4 (PF4) were used as coagulation activation markers. Furthermore, scanning electron microscopy (SEM) was used to visualize platelet adhesion to the sensor surfaces. Compared to uncoated gold sensors, NCO-sP(EO-stat-PO) coated sensors revealed significant better resistance against protein adsorption, lower TAT generation and a lower amount of adherent platelets. Moreover, coating with ultrathin NCO-sP(EO-stat-PO) films creates a cell resistant hemocompatible surface on gold that increases the chance of prolonged sensor functionality and can easily be modified with specific receptor molecules.