Detection of malarial byproduct hemozoin utilizing its unique scattering properties

Abstract

The scattering characteristics of the malaria byproduct hemozoin, including its scattering distribution and depolarization, are modeled using Discrete Dipole Approximation (DDA) and compared to those of healthy red blood cells. Scattering (or dark-field) spectroscopy and imaging are used to identify hemozoin in fresh rodent blood samples. A new detection method is proposed and demonstrated using dark-field in conjunction with cross-polarization imaging and spectroscopy. SNRs greater than 50:1 are achieved for hemozoin in fresh blood without the addition of stains or reagents. The potential of such a detection system is discussed.

In vivo microscopy of hemozoin: towards a needle free diagnostic for malaria

“…This by-product is converted by the parasite in a crystallization process, forming the insoluble hemozoin [4]. Owing to its crystalline nature, hemozoin is a highly scattering, birefringent material with strong optical absorbance and paramagnetic properties, making it an ideal candidate for in vivo optical interrogation [5,6]. Hemozoin has been explored as an endogenous malaria optical biomarker using laser desorption mass spectrometry, magnetooptic detection, and vapor nanobubble acoustical detection [7][8][9].…”

Staining-free malaria diagnostics by multispectral and multimodality light-emitting-diode microscopy

“…10 Despite the increasing number of sophisticated technologies, Giemsa staining of thin and thick blood smears remains the gold standard for malaria diagnosis. 11,12 Due to the transparency of the infected erythrocytes [red blood cells (RBCs)], under bright field microscopy, a dye agent is required to enhance the visual contrast of the parasite and its various shapes for accurate identification. Fluorescence staining techniques can, under optimum conditions, detect 20 to 50 parasites∕μL, 11 but is rather time-consuming and requires well-trained personnel; moreover, it requires manual examination using high-power microscopy of typically hundred fields of the slide for providing a confident decision.…”

“…Another approach has been to develop antigen-based rapid diagnostic tests (RDTs), which can be self-administered outside the laboratory. There is contradicting information with regard to the sensitivity of antigen-based techniques 11 versus microscopy, 12 but the reports agree on the fact that the cumulative costs for administering the test on a wide scale poses a monetary problem, since the cost of a test ranges between $0.50 to $1.50. Since nearly 500 million cases of malaria are reported on a yearly basis, all the above-mentioned factors must be optimized in order to tackle the problem head on.…”

“…The scattering coefficient is dependent on the shape, orientation, and refractive-index distribution of the RBC since the scattering cross-section will vary across the disc-shaped RBC. 12,19,24,25 The refractive index is related to the absorption coefficient through the Kramer-Kronig relation. 26 In a thin film on a microscopy slide, there is ideally one layer of RBCs deposited, and single scattering by light can be assumed, whereas from a thick blood film having multiple layers of RBCs, multiple scattering is expected.…”

Automated bacterial identification by angle resolved dark-field imaging

“…Dark-field (DF) microscopy has seen relatively little use in clinical microscopy applications [11][12][13]. DF has been used to image bacterial flagella [14] and is an established procedure for the diagnosis of syphilis infections [13].…”