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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5533_Библиотеки_им_академика_М_И_Перельмана.pdf
Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
The operational characteristics of biosensors are determined by their design and
structural features. The sensor sensitivity, cost, physical limitations and signal
processing properties are primarily determined by the signal transducer. The
instrument cost is determined by the signal transducer primarily. This also decides
the size, portability, data acquisition and signal processing. The sensor interface
plays an important role in operational characteristics in many ways owing to
binding of an analyte with a bio-affinity-based sensor that is stoichiometric in
nature, therefore immobilization of affinity element is crucial.
2.7.5 Immunosensors
Analytical devices which are precisely based on affinity are known as immunosensors. Such type of sensors consists of an antibody or antigen as biorecognition
moieties, which are immobilized on the transducer surface, showing immunochemical reactions providing the basis of the analysis. Immunosensors have long been
known for their pivotal role in the label-free and non-invasive detection of various
biomolecules like cancerous molecules, proteins, lipids, LDLs and microorganisms
like bacteria and viruses due to high specificity. Immunosensors are known to be
very sensitive and could detect molar concentration of biomolecules up to pico- and
femto-range. Immunosensor-based tools are able to detect the changes in various
parameters like RI, current, resistance etc, which come from the immunocomplexes
formed by the reaction occuring between the antigen and antibody.
Traditionally, an immunoassay employs an antibody (Y) that possesses two sites
capable of binding to antigens. The binding between an antigen and its corresponding antibody is characterized by a high degree of specificity, reproducibility, and
suitability for detecting a wide range of target biomolecules in biosensing applications. The paratope refers to a specific binding region that is located on the surface of
Y and is responsible for recognizing and attaching to the antigen (Ag). However, an
antigen possesses an epitope that plays a crucial role in the identification process of
the immune system, namely through the assistance of antibodies or T cells. The
creation of an Ag–Y complex necessitates a greater level of complementarity
between the binding sites of Ag and Y in order to facilitate non-covalent interaction.
2.7.6 Microbial biosensors
Microbial biosensors utilize microorganisms with a transducer to produce rapid,
accurate and sensitive detection of target analytes. These biosensors are used in
diverse fields such as medicine, monitoring of the environment, food processing,
defense and safety. The former microbial biosensors utilized the functions of
respiration and metabolism to detect a substance as substrate or inhibitor of these
processes. Currently, a microorganism based on a reporter gene fused with an
inducible gene promoter is modified genetically and widely used to assay bioavability and toxicity. Microorganisms basically provide improvement of performance
to detect a range of chemical substances via genetic modification in the broad range
of pH and temperature, making them an ideal biological sensing material [18].
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2.7.7 DNA-based biosensors
DNA-based sensors employ nucleic acids as the biorecognition elements on the surfaces
of transducers. DNA-based biosensors have recently emerged as a compelling approach
due to their quick performance and cost-effectiveness in identifying specific DNA
sequences. These techniques are dependent on the immobilization of a DNA probe,
which consists of a single-stranded oligonucleotide, onto the surface of a transducer.
The transducers under consideration encompass optical, electrochemical, and piezoelectric varieties. The probe DNA exhibits specificity towards the target complementary
DNA sequence, which is identified by the process of hybridization, leading to the
generation of a detectable signal. The conversion of the specific binding energy between
a single stranded DNA probe and its complementary DNA strand results in the
generation of relative output signals. Different amplification techniques including
electrochemicals such as amperometric, potentiometric and impedimetric and optical
such as SPR, absorption, FRET, fluorescence etc, have been employed for fabrication
of DNA-based sensors. Various transducing materials such as carbon-based, metal
nanoparticles, semiconductor nanomaterials, nanocomposites etc have been utilized due
to their large surface-to-volume ratio and biocompatibity with DNA [19].
2.7.8 Phage sensors
In this method a bacteriophage is immobilized at the surface of the sensor to detect
pathogens in the sample. Phage-mediated biosensors demonstrate high sensitivity,
precision, and dependability in their outcomes. Biosensors utilizing bacteriophages
have been employed for the direct identification of pathogens in perishable food
items, particularly milk and water [20]. Recently, phages-based optical biosensors
have been employed for the diagnosis of food-borne pathogens and several
pathogens have been detected using such biosensors.
2.7.9 Optical biosensors
Optical biosensors use an optical transducer for biorecognition of biomolecules that
generate a signal directly proportional to the target analyte concentration. Optical
biosensors can exploit a range of biological materials as biorecognition elements
such as antigens, antibodies, enzymes, nucleic acids, receptors, whole cells and
tissues. The change in the optical properties like surface plasmon resonance,
evanescent wave fluorescence and optical waveguide interferometery are monitored
to measure the interaction of the target analyte with the recognition element [21].
2.7.10 Cantilever-based biosensors
The key element in most of the mechanical biosensors is a cantilever having a
specific resonance frequency or amplitude. Cantilever devices measure the quasistatic deflection of the cantilever caused upon binding of biomolecules with a
functional group on the device surface. As the biomolecules bind, stress on the
surface developed due to electrostatic repulsion or attraction causes the change of
frequency/amplitude. The amount of deflection is generally measured by a laser
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
beam incident on the cantilever. This technique has been employed to examine
binding proteins and DNA [22].
2.7.11 Bio-MEMS
Biomedical (or biological) microelectromechanical systems (Bio-MEMS) have
emerged as a new area for biological and medical applications. It is often referred
as lab-on-a-chip or micro total analysis system. This method is more focused on
technology of mechanical parts and microfabrication for various applications.
Alternatively, lab-on-a-chip is related to miniaturization and incorporation of
laboratory processes and experiments on a single chip. Bio-MEMS can be broadly
defined as the science of operating at microscale level for biomedical and biological
applications such as proteomics, genomics, point-of-care testing etc [23].
2.8 Physical biosensors
2.8.1 Thermometric biosensors
The fundamental properties of biological reactions such as absorption and heat
evolution are exploited by thermoelectric biosensors. Calorimetric is an example of
thermometric techniques that measure the heat change to calculate degree of reaction
or structural dynamics of biomolecules in a solution by measuring the temperature
change of circulating fluid due to reaction between substrate and immobilized
enzymes. The temperature change evolves both by absorption or radiation of heat
during a biochemical reaction which is directly proportional to the molar enthalpy
and overall number of products formed in the biochemical reaction.
2.8.2 Acoustic biosensors
Acoustic sensors are basically microelectromechanical systems (MEMS) that use
modulation of surface acoustic waves as a function of input parameter. The
alterations in amplitude, phase, frequency, or time-delay observed between the
input and output electrical signals are utilized for the purpose of quantifying the
input characteristics. Piezoelectric materials are used in acoustic sensors to generate
waves. Due to excellent mechanical properties and stability, quartz is commonly
employed as it is abundant in Nature and allows low-cost manufacturing.
2.8.3 Magnetic biosensors
Magnetic biosensors measure the change in properties of the magnetic field like
strength, direction and flux as a function of the input parameter. These sensors are
divided in two different groups. The first category of sensor is employed to estimate
total magnetic field, whereas the second type is used to estimate vector component of
the magnetic field and later is utilized to develop a range of sensors employed.
2.8.4 Wearable skins as biosensors
These sensors are currently being used in various biomedical applications. An
important example is smart watches integrated with various health-related issues
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
such as heart rate monitor, pulse oxymeters, gyroscope accelerometer etc. Wearable
sensors are user-friendly and do not need having technical expertise [24]. The
wearable technology extracts information without involving surgical procedures and
implantation that may cause long-term effects.
2.9 Electrochemical biosensors
The electrochemical signal is produced during the exclusive reaction between bioreceptors and target analytes mainly as an enzyme kinetic reaction on a transducer
surface with improved signal-to-volume proportion and offering label-free and invasive
detection. The target analytes are then quantified depending on the strength of output
electrical signal in the form of current, voltage, capacitance and impedance etc. This
sensor typically consists of three electrodes; a working electrode, a reference electrode
and a counter electrode. The reaction occurs at the surface of the electrode leading either
to transfer of electrons across the double layer (give rise to a current) or passing through
to double-layer potential (causing a voltage). Therefore, either the current or potential is
recorded as a function of input analyte. Electrochemical biosensors are classified on the
basis of operating principle such as potentiometric, impedometric, voltammetric,
coulometric, conductimetric, amperometric, impedimetric, capacitive etc, which convert
the electrochemical reactions into a quantifiable signal.
2.9.1 Potentiometric
This particular chemical biosensor has the capability to ascertain the analytical
concentration of a target analyte, whether it is in the form of a gas or a solution. It
achieves this by measuring the potential of the electrode, even in the absence of
current flow between the working and reference electrodes. The relationship between
the value of potential and the concentration of the target analyte in the solution or
gas is exactly proportional.
2.9.2 Coulometry methods
This is distinguished from voltammetry and amperometry methods as it does not depend
on control of current mass transport to obtain a signal dependent on concentration. This
method does not require calibration. In this technique the total current passed is
measured directly or indirectly in order to determine the number of passed electrons.
2.9.3 Conductometry methods
The small variation in electrical conductivity of the solution during electrochemical
reactions is measured using a sinusoidal signal to avoid the effect of double-layer
charging, Faradaic process and concentration polarization by generating an electric field.
2.9.4 Potentiometric titration
This is a chemical analysis technique in which the endpoint is observed using an indicator
electrode while changing the concentration during titration and the information is
regarding the nature of reaction. These methods are particularly versatile because the
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
indicator electrodes are suitable for examining a wide range of chemical reactions. This
technique is reliable, using low cost apparatus and easily available in laboratories.
2.9.4.1 Potentiometric electrochemical cells
The electrochemical cells comprise two half-cells; in each half an electrode is
immersed in a solution of ions which play an important role in determining the
electrode potential. The two half-cells are connected via a salt bridge which has an
inert electrolyte such as KCl. A potentiometric measurement system consists of two
electrodes such as reference electrode, anode, cathode and indicator. The potential
of a reference electrode is fixed, however, the change of indicators potential depends
upon the ion concentration present in the analyte.
2.9.4.1.1 Cyclic voltammetry
Voltammetry electrochemical is a technique in which target analyte information is
obtained by measuring the resulting current while varying a potential. Therefore, it
is referred as an amperometric tool. Cyclic voltammetry (CV) is valuable to
acquire information regarding the electrochemical reaction and redox potential of
solutions with target analyte. The voltage is swept in both directions in a range at a
fixed rate, as shown in figure 2.4. The enzyme kinetics and progression of the
Figure 2.4. Typical voltammogram.
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
chemical reaction can be monitored by varying the scan rate that offers
enough time to permit significant chemical reactions to take place [25]. The
current is measured among the working electrode and the counter electrode, while
voltage is measured between reference electrode and working electrode. A
voltammogram is plotted for different concentrations. The redox peak is obtained
and analyzed.
The information regarding the nature of reaction, i.e. reversible, quasi-reversible
or non-reversible is estimated from the voltage difference in the oxidation and
reduction peaks [26]. The voltammogram shape for a certain compound relies on the
scan rate, surface of electrode and concentration of catalyst. For example, increase
in concentration of enzymes specific to a reaction at a particular scan rate results in a
higher current in comparison to non-catalyzed reactions [27]. CV is not only helpful
for sensing but also to understand the processes occurring on the surface of the
sensing electrode. The voltammetry methods also measure the current in pulsed
mode (current due to charging) upon changing the potential. When potential is
applied between working electrode and reference electrode, electron exchange
occurrs between the working electrode and the electroactive species. The change
in the potential difference is due to charging and discharging phenomena by forming
an electrical double layer.
2.9.4.1.2 Impedance spectroscopy
Electrochemical impedance spectroscopy (EIS) is a powerful analytical tool to
estimate the interfacial characteristics of the surface modified electrode.
Electrochemical impedance is generally obtained by measuring the current through
the cell when AC potential is applied through an electrochemical cell. The angular
frequency is varied at a fix applied potential, and the complex impedance is
recorded. Therefore, EIS involves the study of both the real and imaginary
impedance, referred as electrical resistance and reactance. The information content
in EIS is much higher than that obtained using DC techniques. It is also helpful to
differentiate between the two electrochemical reactions; to identify diffusion limited
reactions and the capacitive behavior of a system.
Impedance spectra are represented by a Nyquist plot which consists of a
semicircle region noticed at higher frequencies due to the process of electron transfer
at the Z′ axis and a linear straight line observed at lower frequencies at an angle of
45° to the real axes as shown in figure 2.5. The straight-line segment demonstrates
the electron transfer process as diffusion limited. The complex impedance is
represented by the sum of real (Z′) and imaginary (Z′) parts obtained due to
resistance and capacitance present in the cell. Charge transfer resistance (R
ct
corresponds to the diameter of the semicircle. EIS is capable of studying the
intrinsic properties of a material or particular processes that might influence the
conductive/resistive or capacitive properties of the electrochemical system. The plot
of R
versus concentration of the analyte is used to extract the information about
ct
the system, which makes it the most valuable tool in the development and material
analysis for biosensor transduction.
)
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
Figure 2.5. Typical EIS curve.
2.10 Materials for biosensors
2.10.1 Nanomaterials for biosensors
Nanomaterials have attracted much interest in the past few years owing to the
increasing demand to manage molecules of interest found in the environment.
Nanomaterials are grown below 100 nm in all dimensions. Nanotechnology deals
with small-sized material, especially below sub-nanometer or a few hundreds of
nanometers [3]. Nanomaterials with unique properties have attracted researchers
worldwide in different fields including health, food, information technology, security
and transport etc. Biosensors have been speculated to realize various needs in the
manufacturing of diagnostics with their fast response and portability. Devices for
microfluidic biosensors have many advantages, especially in clinical diagnosis. The
sensitivity, selectivity and reproducibility of biosensors is still a challenge, and
continuous efforts are still being made to improve these parameters and towards the
miniaturization of biosensors for quantification of biomolecules together with
controlling of microfluids [4]. These miniaturized devices require lowest volume in
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
channels and containers having sizes in microns (10−9to 10
−18
l), leading to the
production of lab-on-a-chip. Nanomaterials have potential for early diagnosis and
hence can play a vital role in detecting a disease leading to prognosis and prevention
of the disease and improved detection performance with lowest value of limit of
detection (LOD). Recently, nanostructured materials having different morphology
such as nanowires, nanotubes etc are being explored as transducers in fabrication of
biosensors and diagnostic devices. The tailored nanomaterials offer enhanced
electrical conductivity, and are biocompatible, therefore, they can be utilized to
amplify characteristic output signals [28]. The utilization of nanomaterials has
demonstrated to result in improved performance of biosensors such as enhanced
sensitivities and lower LOD by magnitude of several orders [29]. Nanostructured
materials provide enhanced surface-to-volume ratio, electrocatalytic properties,
mechanical strength, chemical activity and diffusivity play a key role in enhanced
performance of biosensors.
2.10.2 Gastrointestinal diseases (GIDs) biosensor
The early detection of GIDs plays a significant role in clinical diagnosis and
managing of GIDs-related problems or susceptibility to high GI risk, and is
important to provide timely therapeutics aid to save lives and reduce healthcare
costs. GIDs has become a potential threat to human health and hence rapid,
sensitive, accurate, reliable sensing devices are explored for early confirmation of
GID [10]. Significant endeavors have been dedicated to the advancement of
innovative diagnostic and therapeutic approaches aimed at enhancing patient
well-being and extending their lifespan. The enhancement of patient outcomes
could be significantly facilitated through advancements in image-based identification, targeted medicine distribution, and metastases ablation. The classical
approaches commonly employed in medical practice often fail to meet the expectations of patients as a result of their limited specificity and inadequate patient
classification. There is a pressing need for the development of more precise and
tailored therapeutic interventions. In pursuit of this objective, researchers have
investigated the potential use of nanotechnologies and nano-devices in advancing
tailored medicinal techniques. Efforts are also made for early diagnosis of various
GI biomarkers for detection of GID such as CRP, anti-neutrophil cytoplasmic
antibodies (ANCA), calprotectin etc [30]. Available classical techniques for diagnosis of GID involving classical methods including immunoassays, enzyme-linked
immunosorbent assay (ELISA), x-ray, ultrasound, MRI, CT scan, endoscopy etc are
performed in central laboratories, which takes a long time to reveal the result after
collection of samples from the patient [10].
A number of different methods like electrochemical, capacitor-based biosensors,
optical field-effect transistor, piezoelectric or calorimetric biosensors are used for
biomarker detection [31, 32]. Nano-biosensors are emerging as a promising
substitute to classical methods to detect GIDs biomarkers. These sensors are fast,
sensitive, reliable and low concentration level, capable of multi-analyte detection at
low-cost, user-friendly and portable [11], and will lead to reduced healthcare
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
expenditure. In addition, nanomaterial-based electrochemicals exhibit better sensor
characteristics owing to their unique properties such as conductivity, high surfaceto-volume ratio and good biocompatibility with enhanced performance [12, 33].
2.10.2.1 Tailored materials for bio-detection
The identification of physiological and pathological signals within the intestinal
system is of utmost importance in order to gain a comprehensive understanding of
various disorders. Investigation of the underlying processes inside the GI tract holds
promise for advancing the field of oral drug development. This is due to the fact that
the absorption of drugs in the intestines is influenced by various factors, including
molecular weight, solubility, and others. Overcoming these challenges has long been
a key hurdle for numerous pharmaceutical compounds. Given the current focus of
numerous contemporary investigations on the conversion of bioactive compounds
into oral pharmaceuticals, it becomes imperative to identify and comprehend the
receptive signals inside the GI system. While in vitro or animal model simulations
have successfully discovered physical signals, the number of conclusions drawn from
real human body situations remains limited [34]. Currently, the clinical identification
of intestinal disorders mostly relies on stool analysis and a limited number of bloodrelated tests. However, it is important to note that these diagnostic methods do not
possess the capability to provide accurate and real-time detection of intestinal
diseases. Moreover, the outcomes obtained from the process of detection often lack
precision and need a considerable amount of time to be generated.
Moreover, the survival of probes within the digestive system is challenging owing
to the unique attributes of the intestinal environment. While the application of
conventional molecular probes and antigen–antibody detection methods presents
difficulties in real-time detection of the intestine, the signals present in the GI tract
still have potential for early intervention in patients to prevent disease progression [35].
The detection and monitoring of intestinal health in contemporary times have proven to
be challenging. The primary strategies employed in this circumstance are the utilization
of an ingestible device and an in vitro customized mechanical analysis.
2.10.2.2 Signals from intestine for detection
Intestinal signals exhibit a significant association with nearly all other organs. While the
major activities of the GI tract encompass digestion and absorption, alterations in the
physiological composition of the intestine can exert a direct influence on the optimal
functioning of several organs such as the kidneys, lungs, brain, liver, and others. One
example of potential consequences is the disruption of the intestinal barrier and
subsequent translocation of germs, which can lead to illnesses inside the circulatory
and respiratory systems [36]. Hence, it is imperative to discern GI symptoms. The
assessment and examination of organ functions in the intestine can provide valuable
insights into the likelihood of organ damage. This can be achieved by detecting several
indicators such as pH, temperature, pressure, gas, and specific compounds.
The most common indicators of abnormal changes in the organs are biomarkers
associated with the GI tract. By doing an analysis of the metabolites produced by the
gut microbiota, it is possible to explore the correlation between biomarkers and
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Nanobiotechnology and Artificial Intelligence in Gastrointestinal Diseases
various disorders. The detection of diseases relies on both biological and physical
cues. Bowel sounds play a crucial role in the assessment of intestinal obstruction and
serve as diagnostic indicators for conditions such as intestinal ischemia and
peritonitis. The identification of intestinal contents is a crucial aspect of the study.
In order to modify the treatment regimen, it may be necessary to assess the patient’s
dietary and pharmaceutical consumption through the detection of intestinal contents. Collectively, these characteristics underscore the need of examining gut signals
for the purposes of diagnosing illnesses and providing treatment support. Currently,
there exists a diverse range of sensors that can be tailored to fulfill specific needs.
Electrochemical sensors have the capability to detect many types of waveforms, such
as cyclic waves, square waves, and differential pulse, within the GI tract.
Voltammetry techniques have the capability to detect bioactive medicinal constituents within the GI tract [37].
2.10.2.3 Sensors for signal detection
Thus far, oral sensors have been employed in various manners for the purpose of
detecting microsignals, including alterations in intestinal pH, temperature, and
pressure. An example of a commercially available device capable of evaluating the
pH levels within the GI tract is the SmartPill capsule endoscope [38]. Furthermore,
the biomarkers present in the digestive system, including proteins, DNA, electrolytes, and physiological gases, can be utilized as potential targets for the real-time
assessment of both health and disease conditions [39]. For example, the presence of
calprotectin and lactoferrin, which are markers of intestinal inflammation, has been
found to be correlated with ulcerative colitis. Moreover, the presence of specialized
and precise sensing elements enables the identification and analysis of signals within
the GI fluid. For instance, the GCN2 molecule in the intestinal region exhibits a
robust response to the amino acid signal. Enteritis can be induced by a deficiency of
leucine in the intestinal tract. Hence, the presence of intestinal inflammation can be
predicted through the monitoring of leucine levels inside the colon [40].
The identification of human diseases can be facilitated by considering not only the
small molecules present in the colon, but also the intestinal microbiota, which serves
as a significant biomarker. Qin et al established a causal relationship between
modifications in the human gut microbiota and the occurrence of liver cirrhosis. It is
possible to predict the onset of liver disease by monitoring changes in gut flora.
Bacterial metabolites are also essential gut signals [41]. According to Yang et al’s
genome-wide shotgun metagenomic cross-sectional study, significant depression
may be triggered by 47 different bacterial species and 50 different metabolites found
in feces. Finding these signs may help in figuring out what causes mental illness [42].
Moreover, gut flora has a big impact on how medications are metabolized. Multiple
studies have demonstrated that microbes possess the ability to alter medicine
molecules subsequent to their oral delivery, resulting in drug activation (as
exemplified by sulfasalazine), inactivation (as exemplified by digoxin), and modifications in toxicity (as exemplified by solivudine). A thorough analysis of the
connection between microorganisms and drugs was conducted by Zimmermann et al
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