Current Status of the Development of Blood-Based …
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stained with Giemsa dye and analyzed by experienced personnel. This method is time
consuming and needs skilled and trained personnel [55]. Nowadays, rapid diagnostic
tests (RDTs) and nucleic acid amplification tests (NATT) are commonly used. RDTs
also termed as point-of-care testing are fast and easy to perform and do not require
any specific instrument and power supply [56]. RDTs are based on lateral flow
technique using specific antibodies which bind to three types of plasmodium antigen
named as P. falciparum histidine-rich protein 2 (P fHRP2), P. falciparum lactate
dehydrogenase (PfLDH), and Plasmodium Pan-specific antigens to detect malaria
[43, 57]. RDTs can detect specific antigen in 15 min from a finger-prick of blood
[43]. RDTs do suffer from a few drawbacks, such as degradation of reagents in
adverse environmental condition and low sensitivity in field along with high cost as
compared to the conventional method [56].
Recently, several microfluidics-based lab-on-chip microdevices for detection of
malaria in early stage have been proposed. These microdevices are based on detection
of protein and changes in the physical properties of RBCs. Nam et al. [54] reported
an active microdevice to separate early and late-stage malaria-infected RBCs based
on their paramagnetic properties using magnetic field gradient. Their device consists
of 100 μm wide and 50 μm deep PDMS microchannel bonded on to a glass slide
and integrated with a ferromagnetic wire as shown in Fig. 6B. They successfully
separated early stage and late-stage infected RBCs with recovery rate of 73% and
98.3%, respectively. Hou et al. [58] presented a passive microfluidics device for
isolating iRBCs based on margination of stiffer iRBCs which get pass through an
outlet, as shown in Fig. 7A. Their device comprises 100 μm wide channel at the inlet
and constricted to 15 μm and expanded to 100 μm at the outlet and asymmetrically
divided in three outlets. The microchannel is 10 μm deep and 3 cm long. They have
utilized margination phenomenon (lateral migration of stiff iRBCs toward the channel
walls) to separate iRBCs and achieved approximately 75% separation efficiency of
early stage iRBCs and 90% late stage. Warkiani et al. [59] reported a PDMS-based
inertial microfluidics device utilizing inertial lift forces acting on healthy and infected
RBCs to isolate iRBCs for downstream polymerase chain reaction (PCR) application
as shown in Fig. 7B.
They designed three constrictions and expansion array of 85 units of dimension
30/90 μm (contraction/expansion), 40/120 μm, and 50/150 μm with a depth of
100 μm. They achieved 99.99% WBC depletion and a malaria parasite collection with
yield of 70.9 ± 11.4% after two-cycle run with their 30/90 constriction–expansion
design.
There are many malaria POC test kits are available in market based on
immunoassay lateral flow. These kits are Carestart Malaria Pf/Pan, OptiMAL,
OptiMAL-IT, and Parabank, BinaxNow Malaria to name few. In past few years,
world health organization (WHO 2015) has approved 86 RDTs manufactured by
different companies [57].
179
stained with Giemsa dye and analyzed by experienced personnel. This method is time
consuming and needs skilled and trained personnel [55]. Nowadays, rapid diagnostic
tests (RDTs) and nucleic acid amplification tests (NATT) are commonly used. RDTs
also termed as point-of-care testing are fast and easy to perform and do not require
any specific instrument and power supply [56]. RDTs are based on lateral flow
technique using specific antibodies which bind to three types of plasmodium antigen
named as P. falciparum histidine-rich protein 2 (P fHRP2), P. falciparum lactate
dehydrogenase (PfLDH), and Plasmodium Pan-specific antigens to detect malaria
[43, 57]. RDTs can detect specific antigen in 15 min from a finger-prick of blood
[43]. RDTs do suffer from a few drawbacks, such as degradation of reagents in
adverse environmental condition and low sensitivity in field along with high cost as
compared to the conventional method [56].
Recently, several microfluidics-based lab-on-chip microdevices for detection of
malaria in early stage have been proposed. These microdevices are based on detection
of protein and changes in the physical properties of RBCs. Nam et al. [54] reported
an active microdevice to separate early and late-stage malaria-infected RBCs based
on their paramagnetic properties using magnetic field gradient. Their device consists
of 100 μm wide and 50 μm deep PDMS microchannel bonded on to a glass slide
and integrated with a ferromagnetic wire as shown in Fig. 6B. They successfully
separated early stage and late-stage infected RBCs with recovery rate of 73% and
98.3%, respectively. Hou et al. [58] presented a passive microfluidics device for
isolating iRBCs based on margination of stiffer iRBCs which get pass through an
outlet, as shown in Fig. 7A. Their device comprises 100 μm wide channel at the inlet
and constricted to 15 μm and expanded to 100 μm at the outlet and asymmetrically
divided in three outlets. The microchannel is 10 μm deep and 3 cm long. They have
utilized margination phenomenon (lateral migration of stiff iRBCs toward the channel
walls) to separate iRBCs and achieved approximately 75% separation efficiency of
early stage iRBCs and 90% late stage. Warkiani et al. [59] reported a PDMS-based
inertial microfluidics device utilizing inertial lift forces acting on healthy and infected
RBCs to isolate iRBCs for downstream polymerase chain reaction (PCR) application
as shown in Fig. 7B.
They designed three constrictions and expansion array of 85 units of dimension
30/90 μm (contraction/expansion), 40/120 μm, and 50/150 μm with a depth of
100 μm. They achieved 99.99% WBC depletion and a malaria parasite collection with
yield of 70.9 ± 11.4% after two-cycle run with their 30/90 constriction–expansion
design.
There are many malaria POC test kits are available in market based on
immunoassay lateral flow. These kits are Carestart Malaria Pf/Pan, OptiMAL,
OptiMAL-IT, and Parabank, BinaxNow Malaria to name few. In past few years,
world health organization (WHO 2015) has approved 86 RDTs manufactured by
different companies [57].