Transdermal Diagnosis of Malaria Using Vapor Nanobubbles

The effect of preparation time and aeration rate on the properties of bulk micro-nanobubble water using hydrodynamic cavitation

Fundamental research on bulk micro-nanobubbles (BMNBs) has grown rapidly due to the demand for their industrial applications and potential role in interfacial sciences. This work focuses on examining properties of such bubbles, including the number, concentration, zeta potential, and surface tension in water. For this purpose, BMNBs were generated by the hydrodynamic cavitation (HC) mechanism. Distilled water and air in the experiments were the liquid and gas phases, respectively. The characterization of bulk microbubbles (BMBs) and bulk nanobubbles (BNBs) were performed through focused beam reflectance measurement (FBRM) and nanoparticle tracking analysis (NTA) techniques, respectively. Zeta potential and surface tension of aqueous solutions were measured at different time and aeration rates. The results showed that aeration rate and preparation time had an important role in the properties of BNBs (concentration, bubble size, and surface charge) and BMBs (number, and bubble size). The instability of BMBs led to the rapid changes in the dissolved oxygen (DO) content in the water. The number of BMBs decreased when preparation time and aeration rate increased, but their size remained constant. By enhancing the preparation time and aeration rate, the concentration of BNBs improved first and then reduced. Additionally, the surface tension of an aqueous solution containing BNBs was significantly lower than that of pure water.

Quantitative diffuse optical spectroscopy for noninvasive measurements of the malaria pigment hemozoin

Hemozoin (Hz) is a crystal by-product of hemoglobin consumption by malaria parasites. There are currently no in vivo deep tissue sensing methods that can quantify Hz presence noninvasively, which would be advantageous for malaria research and treatment. In this work, we describe the broadband near-infrared optical characterization of synthetic Hz in static and dynamic tissue-simulating phantoms. Using hybrid frequency domain and continuous-wave near-infrared spectroscopy, we quantified the broadband optical absorption and scattering spectra of Hz and identified the presence of Hz at a minimum tissue-equivalent concentration of 0.014 µg/mL in static lipid emulsion phantoms simulating human adipose. We then constructed a whole blood-containing tissue-simulating phantom and demonstrated the detection of Hz at physiologically-relevant tissue oxygen saturations ranging from 70-90%. Our results suggest that quantitative diffuse optical spectroscopy may be useful for detecting deep tissue Hz in vivo.

Malaria Detection by Third-Harmonic Generation Image Scanning Cytometry

Despite global efforts aimed at its elimination, malaria is still a significant health concern in many countries across the world. The disease is caused by blood-borne parasites, Plasmodium species, and is transmitted by female Anopheles mosquitoes and presents with generic febrile symptoms that are challenging to diagnose clinically. To adequately tackle this issue, an effective detection method is required for screening potential malaria patients for infection. To this day, the gold standard for malaria detection remains basic light microscopy of Giemsa-stained patient blood smears to first enable detection and manual counting to determine the parasite density by a microscopist. While effective at detecting parasites, this method requires both significant time and skilled personnel. As an alternate approach, we propose a new malaria detection method that we call third-harmonic generation image scanning cytometry (THGISC) based on the combination of third-harmonic generation imaging, high-speed motorized scanning, and automated software processing. Third-harmonic generation (THG) is a nonlinear optical process in which the frequency of incident photons is tripled within the sample material. We have previously demonstrated that hemozoin, a metabolic byproduct of the malaria parasite, presents a significant THG signal. We now present a practical approach that uses the selectivity of this contrast mechanism to perform label-free image scanning cytometry of patient blood smears for automated malaria detection. In this work, we applied this technique to lab-cultured parasites and parasites in whole blood obtained from malaria patients. We also compared its effectiveness to parasite counts obtained by classical methods. The ability to easily and rapidly determine parasitemia by THG offers potential not only for the easy confirmation of malaria diagnoses following symptoms, but also the tracking of treatment progress in existing patients, potentially allowing physicians to adjust medication and dosage for each individual.