Editorial
Humankind
has faced against different kinds of diseases since the dawn of time. A wide
range of methods and technologies have been developed in order to reach a
correct diagnosis, which is essential to achieve an effective treatment and
control of outbreaks [1]. Although symptom-based diagnosis has been
the most practiced in time, it is subjective and often performs a late
detection [2]. Modern society demands yet faster and more
reliable diagnostic information therefore in response to this need, biological
sensing of pathogenic agents such as the one that performs a biosensor has been
developed in the last decades [3, 4].Biosensors are
analytical devices comprised of a biological recognition element and a transducer
[5](Figure 1).
Emulating
the responses of living biological systems, using different kind of
bioreceptors and converting them in visible or electrical signals, allows
biosensors to have multiple applications. Its main fields of operations are not
only related to the diagnosis and control of diseases, also within the sectors
of agriculture, food safety, homeland security, and environmental monitoring [6]. Furthermore, they can be classified either by their bioreceptor or
their transducer type. Some examples of common bioreceptors are antibodies,
enzymes, DNA, and cells [7]. On the other
hand, to translate the biological behavior, which can occur at a small and fast
scale to a signal that could be measured and characterized, the transducers are
needed. In particular, they transform the reaction result in something that
could be measured with lab equipment such as colorimetry or fluoresce change of
a substance in proportion to a specific analyte [8], or modify
properties like the electric impedance [9].
With
the use of transducers to get new interpretations to the information given to
us by the biological world, it is also possible to group some sensing
techniques. An example of them is the colorimetric sensing techniques, that are
those in which the outcome of
a biological reaction or behavior is
transduced in a variation of color, this could be either on the visible or
invisible spectrum of light, such examples include the modification of bacteria
to make them fluorescent [10], or use chemical
reactions that generate a difference in color proportional to an enzyme
activity [8,11].Enzyme sensors complies another group. The
basis of enzyme sensors is the use of enzymes as the biological recognition
element. The vast majority of enzyme sensors uses an electrode as the transducer
and employs a type of enzymes, normally oxidoreductases or peroxidases, to
perform the chemical reactions that will be measured [12]. Enzyme-based sensors have been extensively studied because of the
ease of isolation and purification of the enzymes from different sources but
enzyme stability and the ability to maintain enzyme activity for a long period
of time are still an obstacle [6].
Biosensor
applications in disease diagnostics have been common practices for many years [11]. Its advantages are a high selectivity and sensitivity, potential for
miniaturization and portability, low cost, detection in real time, use of small
sample volumes and rapid response. One of the most widespread is the use of
glucose oxidase enzyme, and peroxidase to create a shift in color relative to
the level of glucose in the sample. This technique is used in the glucometer
and is used to aid the diagnosis and continuous control of the diabetes disease
[5]. Likewise, the development of methods that
can facilitate low-cost diagnosis of infectious diseases has been widely
studied especially in neglected diseases such as Chagas disease.
Within
the main biosensors of diagnosis of Chagas disease at the chronic state, can be
found the immunosensors for serological diagnosis. During this phase, the
infected subjects develop antibodies against the parasite, while immobilized
antigens sometimes coupled with microfluidic systems and electrodes; allow
asserting the existence of the disease [13,14]. Yet,
only a few studies have focused on the acute state of the disease. Because
there is no reported presence of antibodies in the body at this stage, the
biosensors developed need to assert the presence of the parasite directly from
a sample of blood. Some works suggest that after a proper separation of the
parasite from the blood particles, employing a microfluidic system, is possible
to detect the presence of the parasite with an impedance biosensor which could
generate a characteristic response for each particle type in the sample, among them,
the parasite.
Another
approach in the use of biological behaviors to detect the presence of diseases
is taking advantage of the antibodies, which are used by the immune system and
bind themselves to bacteria or viruses [15]. An
example of this approach is the use of antibodies immobilized on gold as
biosensors to detect the presence of the Human Papilloma Virus (HPV). The
change of impedance of wells with gold electrodes are measured, where the monoclonal
antibody (mAb)5051 was immobilized. Those variations are due to the existence
of the HPV in the sample, which bind to the antibodies and change the impedance
of the system [9].
The
prospects of diagnostic biosensors are promising. Although the rate of growth
of the biosensors market still has to reach that of its state of the art in the
Academy, they are expected to be faster, easy to manufacture and use for
untrained individuals, which will allow them to reach a wide percentage of the
people affected by these diseases. To achieve an ideal scenario where every
smartphone is transformed in a compete lab on a chip with disease diagnostics
capabilities, the study and use of biosensors is crucial. Generation of
developments in this area and their continuous publication will allow these
advances to be adequately given and hopefully Biosensors and Bioelectronics
Open Access will publish many of these findings.
editorial 