Department of Chemistry , McGill University , 801 Sherbrooke Street West , Montreal , Quebec H3A 0B8 , Canada.
Institute of Parasitology , McGill University , Sainte Anne de Bellevue , Quebec H9X 3 V9 , Canada.
Anal Chem. 2019 Feb 5;91(3):2216-2223. doi: 10.1021/acs.analchem.8b04791. Epub 2019 Jan 15.
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.
尽管全球都在努力消除疟疾，但在世界上许多国家，它仍然是一个严重的健康问题。这种疾病是由血液寄生虫疟原虫引起的，由雌性疟蚊传播，表现为普通的发热症状，临床上难以诊断。为了有效地解决这个问题，需要一种有效的检测方法来筛选潜在的疟疾患者是否感染。迄今为止，疟疾检测的金标准仍然是对载玻片上经吉姆萨染色的患者血液进行基本的光学显微镜检查，首先进行检测，然后由显微镜检查人员手动计数确定寄生虫密度。虽然这种方法在检测寄生虫方面非常有效，但需要大量的时间和熟练的人员。作为一种替代方法，我们提出了一种新的疟疾检测方法，称为基于三次谐波成像、高速机动扫描和自动软件处理的三次谐波产生图像扫描细胞术（THGISC）。三次谐波产生（THG）是一种非线性光学过程，其中入射光子的频率在样品材料中增加三倍。我们之前已经证明，疟原虫的代谢副产物血色素呈现出显著的三次谐波信号。我们现在提出了一种实用的方法，该方法利用这种对比机制的选择性对患者的血涂片进行无标记图像扫描细胞术，以进行自动疟疾检测。在这项工作中，我们将该技术应用于实验室培养的寄生虫和从疟疾患者身上获得的全血中的寄生虫。我们还将其与经典方法获得的寄生虫计数进行了比较。通过 THG 轻松快速地确定疟原虫血症的能力不仅有可能在出现症状后轻松确认疟疾诊断，还可以跟踪现有患者的治疗进展，从而使医生能够为每个患者调整药物和剂量。
