Current Status of the Development of Blood-Based …
183
to various disorders. WBC handheld point-of-care analyzers are also commercially
available. The Hemocue WBC can provide total WBC count whereas the Chempaq
XBC provides total WBC count with 3-part differential. These counters are based
on the impedance cell counting method. Cell-based assays for detecting HIV depend
on the CD4+ T-cell counts. A CD4 count of fewer than 350 cells/mm
3 is indicative
of the disease and is one of the qualifications for a diagnosis of Acquired immune
deficiency syndrome (AIDS) [4, 97, 98]. Cheng et al. [65] reported a CD4+ T-cell
counting device based on microfluidic cell affinity chromatography. In this device,
label-free whole blood, 10μL is directly injected into the microdevice, and CD4+
T cells are directly captured using controlled shear stress. The PDMS microdevice
was functionalized by antibodies to capture CD4+ T cells, which were later counted
using a simple microscope (Fig. 9B). The results were found to be in close agreement
with the conventional counting using the expensive flow cytometer.
Various CD4 counting portable devices also exist in the market today. For example,
CyFlow miniPOC, PointCare NOW, Daktari CD4 Counter, Visitect CD 4, BDFACS
Presto, Zyomyx CD4 Test, and Pima Analyzer, to name a few [4, 98, 99]. Among these
POCT devices, the Daktari CD4 counter and Zyomyx counters are quite attractive
as they are very portable and low cost and easy to use systems with high sensitivity
and specificity.
5 Platelets
Platelets are cytoplasmic fragments of the megakaryocytes [39]. They contain several
proteins, enzymes, and platelet-derived growth factors which help in blood clotting
and soft tissue healing. Blood clotting also known as hemostasis, is a multistep
process including vascular constriction, platelet plug formation, and blood coagulation [100]. Although hemostasis is an essential phenomenon for sustenance of human
life, the disorders of hemostasis known as thromboembolic disorders and bleeding
disorders are life threatening [39]. Thromboembolic disorders arise when undesired
clot forms inside the vessels or travels in microcirculation and block circulation of
blood whereas bleeding disorders are those which prevent normal clot formation
[39]. Platelet disorders may be linked with various diseases such as cardiovascular
disease, diabetes, inflammation, haemorrage, sepsis, Von Willebrand disease, scurvy
etc. [100–104]. Platelets separation have many applications such as in transfusion
purpose, preparation of platelet-rich plasma (PRP), and study of hemostatic disorder.
Clinically, platelets are separated using centrifugation-based methods known as
PRP method, buffy coat method, and apheresis. These methods involve multistep
processing, need trained personnel, are time consuming, and have adverse effect
on the quality of platelets [100]. Separation of platelets on microfluidics devices is
categorized as active and passive separation methods. The active separation methods
involve dielectrophoresis (DEP) [105, 106] and acoustophoresis methods [107–110].
The passive separation method involves inertial methods [111], hydrophoretic techniques [101, 112], deterministic lateral displacement (DLD) method [113, 114],
183
to various disorders. WBC handheld point-of-care analyzers are also commercially
available. The Hemocue WBC can provide total WBC count whereas the Chempaq
XBC provides total WBC count with 3-part differential. These counters are based
on the impedance cell counting method. Cell-based assays for detecting HIV depend
on the CD4+ T-cell counts. A CD4 count of fewer than 350 cells/mm
3 is indicative
of the disease and is one of the qualifications for a diagnosis of Acquired immune
deficiency syndrome (AIDS) [4, 97, 98]. Cheng et al. [65] reported a CD4+ T-cell
counting device based on microfluidic cell affinity chromatography. In this device,
label-free whole blood, 10μL is directly injected into the microdevice, and CD4+
T cells are directly captured using controlled shear stress. The PDMS microdevice
was functionalized by antibodies to capture CD4+ T cells, which were later counted
using a simple microscope (Fig. 9B). The results were found to be in close agreement
with the conventional counting using the expensive flow cytometer.
Various CD4 counting portable devices also exist in the market today. For example,
CyFlow miniPOC, PointCare NOW, Daktari CD4 Counter, Visitect CD 4, BDFACS
Presto, Zyomyx CD4 Test, and Pima Analyzer, to name a few [4, 98, 99]. Among these
POCT devices, the Daktari CD4 counter and Zyomyx counters are quite attractive
as they are very portable and low cost and easy to use systems with high sensitivity
and specificity.
5 Platelets
Platelets are cytoplasmic fragments of the megakaryocytes [39]. They contain several
proteins, enzymes, and platelet-derived growth factors which help in blood clotting
and soft tissue healing. Blood clotting also known as hemostasis, is a multistep
process including vascular constriction, platelet plug formation, and blood coagulation [100]. Although hemostasis is an essential phenomenon for sustenance of human
life, the disorders of hemostasis known as thromboembolic disorders and bleeding
disorders are life threatening [39]. Thromboembolic disorders arise when undesired
clot forms inside the vessels or travels in microcirculation and block circulation of
blood whereas bleeding disorders are those which prevent normal clot formation
[39]. Platelet disorders may be linked with various diseases such as cardiovascular
disease, diabetes, inflammation, haemorrage, sepsis, Von Willebrand disease, scurvy
etc. [100–104]. Platelets separation have many applications such as in transfusion
purpose, preparation of platelet-rich plasma (PRP), and study of hemostatic disorder.
Clinically, platelets are separated using centrifugation-based methods known as
PRP method, buffy coat method, and apheresis. These methods involve multistep
processing, need trained personnel, are time consuming, and have adverse effect
on the quality of platelets [100]. Separation of platelets on microfluidics devices is
categorized as active and passive separation methods. The active separation methods
involve dielectrophoresis (DEP) [105, 106] and acoustophoresis methods [107–110].
The passive separation method involves inertial methods [111], hydrophoretic techniques [101, 112], deterministic lateral displacement (DLD) method [113, 114],