No abstract

Rapid diagnostic tests (RDTs) designed to function at the point of care are becoming more prevalent in malaria diagnostics because of their low cost and simplicity. While many of these tests function effectively with high parasite density samples, their poor sensitivity can often lead to misdiagnosis when parasitemia falls below 100 parasites/l. In this study, a flow-through pipette-based column was explored as a cost-effective means to capture and elute more histidine-rich protein II (HRPII) antigen, concentrating the biomarker available in large-volume lysed whole blood samples into volumes compatible with-specific RDTs. A systematic investigation of immobilized metal affinity chromatography divalent metal species and solid phase supports established the optimal design parameters necessary to create a flow-through column incorporated into a standard pipette tip. The bidirectional flow inherent to this format maximizes mixing efficiency so that in less than 5 min of sample processing, the test band signal intensity was increased up to a factor of twelve from HRPII concentrations as low as 25 pM. In addition, the limit of detection per sample was decreased by a factor of five when compared to the RDT manufacturer's suggested protocol. Both the development process and commercial viability of this application are explored, serving as a potential model for future applications.

To help address the limitations of operating conventional microbiological culture incubators in low resource environments, a new incubator design was developed and tested to meet the requirements of operation in laboratories without reliable power (power outages up to 12 contiguous hours) or climate control (ambient indoor temperatures from 5 °C to 45 °C). The device is designed to enable adherence to incubation temperatures recommended for growth detection, identification, and drug susceptibility testing (DST) of human pathogenic bacteria. During power outages, stable temperatures are maintained in the device's internal sample compartment by employing phase change material (PCM) as a bi-directional thermal battery to maintain incubation temperature. Five prototypes were tested in a laboratory setting using environmental test chambers and programmable power supplies, and three were field tested in the Lao PDR in situations of intended use. The prototypes successfully held their temperature to within ±1 °C in both laboratory environmental chamber testing as well as during the field test. The results indicate that the device will maintain stable culture temperatures across periods of intermittent power supply, while enabling normal workflow of this could greatly increase the availability of microbiological culture for diagnosis and antimicrobial resistance (AMR) monitoring.

Measurements in dry desert soils have shown significant complex resistivity (or impedivity) variations across the frequency range from 1 kHz to 1 MHz. The impedivity of various soils are measured in-situ in field experiments using a custom apparatus, consisting of a probe head and accompanying custom electronics. Four galvanic electrodes are fixed in the probe head, and arranged in a Wenner array, such that the geometric factor is 1.00 m. In this way, impedance measurements (in Ω) are easily converted to estimates of impedivity (in Ω · m). Field measurements made in-situ are important for obtaining accurate results, because impedance measurements typically change value significantly once soil samples are extracted from their natural environment. These changes are due to changes in the grain boundaries, as well as changes in moisture, temperature, etc. Soil impedivity signatures collected on a variety of soils in the south west region of the USA over the frequency band up to 1 MHz are presented.

No abstract