by non-DNA-based detection techniques. These pathogenic disease-related biomarkers

can be detected by methods involving nanostructures. Nanomaterials modified sensors

require minute sample concentrations and provide accurate results with high sensitivity.

Nanoparticles-based sensors possess magnetic and optical properties for detecting pa­

thogenic bacteria in real samples. Bimetallic gold-silver nanocluster was synthesized

for detecting Campylobacter jejuni. Bimetallic NPs possess optical properties and enhance

the optical intensity, color perception, and sensitivity for Campylobacter jejuni. The de­

tection of the bacterium was also done by immunoassay. The sensor exhibited an ac­

ceptable linear range with a LOD of 10 CFU/mL [42].

8.7.3 Acoustic Sensor

An acoustic wave sensor, also known as quartz crystal microbalance quantify thin film by

identifying the resonance frequency. These sensors simultaneously detect changes in

electrical and mechanical properties. They are used in biomarker detection, especially the

malignant tumor-related biomarkers for early-stage disease screening [43].

Glial-fibrillary-acidic protein is expressed by astrocytes in the central nervous system.

This protein acts as a biomarker in brain-related diseases. The presence of glial-

fibrillary-acidic protein in circulating blood is the indicator of diseases such as glio­

blastoma multiforme (GBM) and multiple sclerosis etc., In a study, an acoustic wave

sensor was used for the detection of glial-fibrillary-acidic protein. They fabricated an

ultra-high frequency wave sensor based on lab on a chip and detected the protein

from clinical samples with 35 pM concentrations. The authors suggested that this point

of care lab-on-a-chip can be used for multiple brain pathologies in detecting bio­

markers [44].

8.8 Fluorescence (FL) Methods

Fluorescent probes are used in analytical sensing and optical imaging. Fluorescent probes

specifically interact with the target analyte under optimized conditions. In ratiometric

fluorescent sensors, fluorescent probes cause target-induced FL-intensity which results in

emission bands at different wavelengths. Dual emission ratiometric FL methods influence

the detection systems and background signals by improving the accuracy and reliability

during the detection process. In FL detection methods, naked-eye identification of target

reflects content changes of biomarkers in the detection system [45]. Fluorescent detection

of biomarkers comes under the photonic techniques in which detection of target bio­

molecule occurs in the form of changes in absorbance, transmittance, luminescence, and

reflectance properties [46].

Norepinephrine is the biomarker of depression correlated with potassium ion con­

centration. Zhou et al. synthesized a fluorescent probe for detecting K⁺-induced nor­

epinephrine transduction signal in neuroendocrine PC12 cells [47]. Alkaline phosphatase

is the indicator of signal transduction and tumor metabolism. Alkaline phosphatase is the

combination of cysteine residues, Mg and Zn. In a study, a fluorescent probe was syn­

thesized by the combination of quinoline malononitrile core decorated with a hydrophilic

phosphate group. The as-synthesized probe causes fluorescent detection of ALP by DQM-

OH aggregates in the presence of alkaline phosphatase. The FL probe can differentiate

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Bioelectronics