**3.3 Diagnostic uses**

Biomedicine research involves advancing our understanding of biology and the processes behind physiological activity and disorders. As a result, in addition to illness therapy, one of the most significant goals is diagnostics, wherein bio-sensitive materials have shown promising potential in detecting low concentrations of biochemical, proteins, and genes that act as sickness-specific indicators. Those indicators are typically tested using high-cost chromatography techniques like high-performance liquid chromatography and gas chromatography-mass spectrometry, but using stimuli-sensitive systems, easy, rapid, precise, and low-cost detection procedures may be established.

For instance, metallic nanoparticles with a size of 4 nm may greatly boost T1 distinction in magnetic resonance imaging; however, their aggregation led in T2 contrasting augmentation owing to in uniform magnetic field around the aggregates. As a result, IONs like these have been employed as a T2 contrast media to diagnose liver disorders. They are, nevertheless, unsuitable for the identification of smaller hepatocellular carcinomas that requires a good detection to improve the individuals' average five-year rate of survival [78]. The fall in pH dispersed the aggregation of the functional metallic nanoparticles when they were treated using i-Motif DNAs that really can convert from unistranded to fused quadruple-helical structure in an acidic medium. Because acidification of the tumor encouraged the breakdown of the metallic nanoparticles aggregates and shifted the MRI signal between T2 to T1 augmentation to better the differentiation between hepatocyte and tiny hepatocytic carcinoma tissues, tiny hepatocytic carcinoma may be diagnosed with these bifunctional metallic nanoparticles [79]. pH-sensitive surfaces made comprised of nanoparticles with just an amino group having a silane layer are another intriguing instance. In an acidic medium, the amino groups are protonated, making the surfaces highly hydrophilic, whereas in a highly alkaline, the surfaces become really hydrophobic. The amount of glucose in the mouth and pee may be reliably determined in one second using this surface via measuring the contact area of the liquid specimen, which is dependent on the created gluconic acid following adding glucose oxidase to the specimen [80]. This non-invasive, economic approach of fast glucose measurement is useful for overcoming the drawbacks of standard intrusive diagnosis of diabetes, including such discomfort and infection hazard. While contemporary research has demonstrated the stimuli-sensitive system's potential and performance in preclinical testing for diagnostic uses, the majority of the built systems do not fulfill the standards for clinical usage. This is owing to the large variety of chemicals found in real specimens collected from individuals with varying situations (e.g., various diets, ethnicities, and lifestyles), which considerably affects the measurement's specificity and stability [81]. Aside from identifying biochemical levels, constant monitoring and distribution centres in human, both of which are challenging to perform, may be required. As a result, motivated monitoring technologies are still in the early stages of development, and more investigation is necessary before they can be used in clinical illness treatment.
