Evaluation of back scatter interferometry, a method for detecting protein binding in solution

Back Scatter Interferometry (BSI) has been proposed to be a highly sensitive and versatile refractive index sensor usable for analytical detection of biomarker and protein interactions in solution. However the existing literature on BSI lacks a physical explanation of why protein interactions in general should contribute to the BSI signal. We have established a BSI system to investigate this subject in further detail. We contribute with a thorough analysis of the robustness of the sensor including unwanted contributions to the interferometric signal caused by temperature variation and dissolved gasses. We report a limit of the effective minimum detectability of refractive index at the 10(-7) level. Long term stability was examined by simultaneously monitoring the temperature inside the capillary revealing an average drift of 2.0 × 10(-7) per hour. Finally we show that measurements on protein A incubated with immunoglobulin G do not result in a signal that can be attributed to binding affinities as otherwise claimed in literature.

Endothelial thrombus formation: an unusual complication related to peripherally inserted central catheters

The Nutritional Support Service (NSS) at William Beaumont Hospital has successfully inserted over 2000 peripherally inserted central catheters (PICCs) since the inception of its PICC program in 1990. The following is a case study of a 43-year-old female with diabetes mellitus and multiple drug allergies who presented to the NSS after Wound Clinic personnel were unable to pull a 43 cm PICC more than 38 cm out of her left arm. Radiographic studies showed the remaining 5 cm of the catheter to be untangled, following the course of the cephalic vein. A surgical cutdown was performed to dilate the cephalic vein and remove the device. The PICC tip was encapsulated in an organic material which was confirmed by pathology to be a thrombus with endothelial lining.