Toward Automatic Label-Free Whispering Gallery Modes Biodetection with a Quantum Dot-Coated Microsphere Population

We explore a new calibration-free approach to biodetection based on whispering gallery modes (WGMs) without a reference measure and relative shifts. Thus, the requirement to keep track of the sensor position is removed, and a freely moving population of fluorophore-doped polystyrene microspheres can now fulfill this role of sensing resonator. Breaking free from fixed surface-based biosensing promotes adhesion between the microsphere sensors and the analytes since both can now be thoroughly mixed. The 70-nm-wide spectrum of green fluorescent microbeads allows us to monitor over 20 WGMs simultaneously without needing evanescent light coupling into the microspheres, hence enabling remote sensing. Since the exact radius of each microsphere is unknown a priori, it requires algorithmic analyses to obtain a reliable result for the refractive index of a solution. We first test our approach with different solutions of alcohol in water obtaining 3 × 10−4 precision on the refractive index at lower concentrations. Then, the solutions of bacterial spores in water yield clear evidence of biodetection in the statistical analysis of WGMs from 50 microspheres. To extend the fluorescence spectral range of our WGM sensors, we present preliminary results on coating microspheres with CdSe/ZnS quantum dots

Sclerotherapy in extrahepatic portal venous obstruction.

One hundred and twenty two patients who presented with variceal bleeding as a result of extrahepatic portal vein obstruction (EHPO) were entered into the sclerotherapy programme with a mean follow up of 23.69 months (range four to 60 months). Eighteen (14.7%) patients were lost to follow up, three (2.4%) patients underwent surgery, and six (4.9%) patients died. Variceal obliteration was achieved in the remaining 95 patients requiring 5.4 (2.4) sessions of sclerotherapy (range 2-18). Seventeen episodes of upper gastrointestinal bleed occurred in 15 patients during sclerotherapy. Recurrence of oesophageal varices was seen in 15 patients. Ten patients developed bulbous gastric varices after obliteration. Major complications including perforation and strictures were seen more commonly in children. Sclerotherapy was associated with a significant reduction in the bleeding rate (bleeds/month/patient) as compared with the presclerotherapy period (p less than 0.001). Endoscopic sclerotherapy is an effective and safe modality in the prevention of variceal bleeds in patients with extrahepatic portal vein obstruction