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V. Laxmi et al.
sample processing time, sample volumes, consumption of costly reagents, parallel
processing, high throughputs, low power consumption, increased sensitivity as well
as precision in controlling fluid assays among others.
Development of blood-based point-of-care microdevices for disease diagnostics is
an area of tremendous growth and possibilities. In this study, we will focus on bloodbased point-of-care microdevices for the diagnosis of diseases. Although several
review articles are available on point-of-care technology [3, 4], this particular study
is dedicated to the current status and development in the field of blood-based microfluidic devices. Here, we will discuss functioning of lab-on-chip microdevices, which
are dedicated to point-of-care technologies for blood-based diagnostics available in
the literature. First, we briefly discuss the importance of a particular blood component, and this is followed by a discussion on prominent microfluidic devices which
have been reported in the literature including the common tests being carried out for
the disease diagnostic purposes. We also report and discuss lab-on-chip microdevices for studying circulating tumor cells (CTCs). Commercialized devices existing
in the market are also reported in this study. Finally, we highlight the current status,
challenges, and the future of point-of-care testing technology.
2 Plasma
Human blood plasma is the liquid medium in which cells are suspended. It makes
about 55% of the total blood volume. It contains approximately 91% water, 7%
proteins, 1% inorganic ions, and other organic substances. Common analytes found
in plasma are proteins, inorganic and organic compounds, metabolites, bacteria,
fungi, microorganisms, viruses, and circulating nucleic acids [6–8]. Due to the presence of large number of analytes or indicators, blood plasma serves as an index to
various diseases and testifies its importance in disease diagnostics and therapeutics.
Blood plasma is separated from other constituents on a routine basis. The conventional method of plasma separation is via centrifugation using a benchtop centrifuge.
Though commonly employed, it involves manual and time-consuming steps. Several
testing procedures demand immediate separation of plasma from the blood sample.
Prolonged exposure of plasma with blood cells may deteriorate the quality of analytes
present in plasma and can adversely affect the test results which will lead to inaccurate diagnosis. In order to detect the analytes effectively high-quality cell-free
plasma is desired. Use of plasma is preferred over whole blood in several diagnostic
tests due to clogging, cell lysis, and cell interference issues associated with whole
blood testing [9, 10]. Plasma holds incredible clinical potential. It is required for a
wide variety of clinical tests, such as glucose test for detecting diabetes mellitus,
cholesterol, brain natriuretic peptide (BNP), troponin T (CTnI) for detecting heart
diseases, C-reactive protein (CRP) for inflammation, Prostate-specific antigen (PSA)
for Prostate cancer, cytokines for cancers, alanine aminotransferase/aspartate aminotransferase (ALT/ASP) for liver disorders, and several other analytes for diagnosis
of various diseases.
V. Laxmi et al.
sample processing time, sample volumes, consumption of costly reagents, parallel
processing, high throughputs, low power consumption, increased sensitivity as well
as precision in controlling fluid assays among others.
Development of blood-based point-of-care microdevices for disease diagnostics is
an area of tremendous growth and possibilities. In this study, we will focus on bloodbased point-of-care microdevices for the diagnosis of diseases. Although several
review articles are available on point-of-care technology [3, 4], this particular study
is dedicated to the current status and development in the field of blood-based microfluidic devices. Here, we will discuss functioning of lab-on-chip microdevices, which
are dedicated to point-of-care technologies for blood-based diagnostics available in
the literature. First, we briefly discuss the importance of a particular blood component, and this is followed by a discussion on prominent microfluidic devices which
have been reported in the literature including the common tests being carried out for
the disease diagnostic purposes. We also report and discuss lab-on-chip microdevices for studying circulating tumor cells (CTCs). Commercialized devices existing
in the market are also reported in this study. Finally, we highlight the current status,
challenges, and the future of point-of-care testing technology.
2 Plasma
Human blood plasma is the liquid medium in which cells are suspended. It makes
about 55% of the total blood volume. It contains approximately 91% water, 7%
proteins, 1% inorganic ions, and other organic substances. Common analytes found
in plasma are proteins, inorganic and organic compounds, metabolites, bacteria,
fungi, microorganisms, viruses, and circulating nucleic acids [6–8]. Due to the presence of large number of analytes or indicators, blood plasma serves as an index to
various diseases and testifies its importance in disease diagnostics and therapeutics.
Blood plasma is separated from other constituents on a routine basis. The conventional method of plasma separation is via centrifugation using a benchtop centrifuge.
Though commonly employed, it involves manual and time-consuming steps. Several
testing procedures demand immediate separation of plasma from the blood sample.
Prolonged exposure of plasma with blood cells may deteriorate the quality of analytes
present in plasma and can adversely affect the test results which will lead to inaccurate diagnosis. In order to detect the analytes effectively high-quality cell-free
plasma is desired. Use of plasma is preferred over whole blood in several diagnostic
tests due to clogging, cell lysis, and cell interference issues associated with whole
blood testing [9, 10]. Plasma holds incredible clinical potential. It is required for a
wide variety of clinical tests, such as glucose test for detecting diabetes mellitus,
cholesterol, brain natriuretic peptide (BNP), troponin T (CTnI) for detecting heart
diseases, C-reactive protein (CRP) for inflammation, Prostate-specific antigen (PSA)
for Prostate cancer, cytokines for cancers, alanine aminotransferase/aspartate aminotransferase (ALT/ASP) for liver disorders, and several other analytes for diagnosis
of various diseases.