An approach toin situdetection of hydrogen peroxide: application of a commercial needle-type electrode

A PRACTICAL NONINVASIVE BLOOD GLUCOSE MEASUREMENT SYSTEM USING NEAR-INFRARED SENSORS

Due to the drastic fluctuation of glucose level in diabetic patients throughout a day, especially when they take a sweet breakfast, and greasy lunch and dinner, their insulin must be promptly measured invasively after each meal. However, invasive measurement of the blood glucose level (BGL) is painful and might lead to infection. In this paper, we design a hardware–software system for estimating BGL in a real-time manner, according to the amount of near-infrared (NIR) absorption at 950 nm. The received light wave is amplified and passed through a low-pass filter (LPF) to eliminate the irrelevant frequency components. We have executed our experiment according to three scenarios: (i) Certain amount of glucose is dissolved in water and the glucose concentration is measured by our equipment, (ii) 5-cm3 blood sample of participants is taken and the BGL is measured in a test tube by our apparatus and then this sample is moved to the gold-standard equipment and the actual value of BGL is measured. The measured voltage versus BGL in our designed optical equipment indicates a fairly linear relation between them. (iii) BGL is measured over the fingertip and compared to the gold-standard value. In this case, the measurement error does not exceed 25% and the voltage change with respect to the BGL shows a nonlinear behavior. The designed system has a low cost and provides an acceptable error, making it suitable to be commercialized for diabetic patients.

Catalase-Containing Silica Particles as Ultrasound-Based Hydrogen Peroxide Sensors to Determine Infected From Noninfected Fluid Collections in Humans

OBJECTIVE. Hydrogen peroxide (H₂O₂) plays a key role in neutrophil oxidative defense against infection. Catalase-containing silica nanoshells are nanoparticles that generate O₂ microbubbles imaged with ultrasound in the presence of elevated H₂O₂. We aimed to determine whether ultrasound-detectable O₂ microbubbles produced by catalase-containing silica nanoshells can determine whether fluid collections drained from patients are infected. SUBJECTS AND METHODS. During this HIPAA-compliant, institutional review board-approved study, 52 human fluid samples were collected from clinically required image-guided percutaneous drainage procedures. Catalase-containing silica nanoshells were added to the fluid samples during imaging in real time using a Sequoia-512 15L8-S linear transducer (Siemens Healthcare). Production of detectable microbubbles was graded subjectively as negative (noninfected) or positive (infected) with low, moderate, or high confidence by a single observer blinded to all clinical data. The truth standard was microbiology laboratory culture results. Performance characteristics including ROC curves were calculated. RESULTS. Microbubble detection to distinguish infected from noninfected fluids was 84% sensitive and 72% specific and offered negative and positive predictive values of 89% and 64%, respectively. The AUC was 0.79. Six of nine false-positive samples were peritoneal fluid collections that were all collected from patients with decompensated cirrhosis. CONCLUSION. The presence of elevated H₂O₂ indicated by microbubble formation in the presence of catalase-containing silica nanoshells is sensitive in distinguishing infected from noninfected fluids and offers a relatively high negative predictive value. False-positive cases may result from noninfectious oxidative stress. Catalase-containing silica nanoshells may constitute a novel point-of-care test performed at time of percutaneous drainage, potentially obviating placement of drains into otherwise sterile collections and minimizing risk of secondary infection or other complication.