tumor cells from normal cells both in ex-vivo and in-vivo imaging. The authors suggested

that the FL probe can assist surgeons during tumor resection [48].

The detection of chloride ions in biofluids is necessary as their abnormal levels lead to

multiple diseases including cystic fibrosis. Cystic fibrosis is diagnosed by monitoring the

chloride ions levels in sweat. A fluorescence sensor was used for detecting chloride ions

because of its high sensitivity and rapid response kinetics. A citrate-based fluorescent

sensor was fabricated for chloride ions detection in the sweat of cystic fibrosis patients.

The fabricated sensor exhibited characteristics of a low-cost multi-analysis system and

can be used in the point-of-care diagnosis of cystic fibrosis in clinical applications [49].

8.9 Nuclear Magnetic Resonance (NMR) Spectroscopy

NMR spectroscopy is a multivariate metabolic profiling technique in disease diagnosis. It

requires one internal standard for biochemical alteration investigation. It is a rapid and

single-step technique with high specificity for identifying multiple analytes in a single

run. In NMR spectroscopy, a minute quantity of targeted sample is required for the

quantification of metabolites in micromolar concentrations. NMR spectroscopy provides

insight about tumor biomarkers for early diagnosis of disease, biochemical changes

linked to disease progression, and provides information about disease biology [50].

Chronic inflammatory bowel disease (IBD) exists in two subtypes i.e., Crohn’s disease

(CD) and ulcerative colitis (UC). The diagnosis of IBD depends on the histologic, endo­

scopic, and radiologic techniques, which are expensive and time-consuming. Clinical di­

agnosis of IBD is less invasive and useful for primary diagnosis and early-stage detection of

disease. In a study, NMR-based metabolic profiles of serum, plasma, and urine of IBD

patients were examined. The authors concluded that the levels of methanol, mannose,

isoleucine, formate, and 3-methyl-2-oxovalerate were high in serum and plasma while le­

vels of creatinine, xylose, allantoin, and mannitol were high in the urine. These clinical

results can be used as biomarkers in early-stage diagnosis of IBD [51].

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease that develops without

prior symptoms. In pancreatic ductal carcinoma, genetic mutations occur in KRAS, TP53,

SMAD4, and CDKN2A genes which lead to alterations in metabolic pathways with ag­

gressive phenotypes. Identification of non-invasive biomarkers indicates the aggressive

subtypes and therapeutic targets to improve the patient’s survival. NMR spectroscopic

study was designed on patients’ derived-PDAC xenograft models to investigate the asso­

ciation between glycolytic metabolism and tumor aggressiveness. The authors found

pyruvate conversion to lactate, which enhances the levels of lactate dehydrogenase (LDH)

enzyme in aggressive patients’ derived-PDAC xenografts [52].

8.10 Microfluidic Devices

Microfluidic devices have dimensions less than 1 mm and are used in molecular biology

and cell separations for disease diagnosis [53]. Microfluidics is also known as lab on chip

technology and is used in a variety of biological assays due to minimal reagent

Biomarker Detection

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