A highly sensitive silicon nanowire (SiNW)-based sensor device was developed using electron beam lithography integrated with complementary metal oxide semiconductor (CMOS) technology. The top-down fabrication approach enables the rapid fabrication of device miniaturization with uniform and strictly controlled geometric and surface properties. This study demonstrates that SiNW devices are well-aligned with different widths and numbers for pH sensing. The device consists of a single nanowire with 60 nm width, exhibiting an ideal pH responsivity (18.26 × 106 Ω/pH), with a good linear relation between the electrical response and a pH level range of 4–10. The optimized SiNW device is employed to detect specific single-stranded deoxyribonucleic acid (ssDNA) molecules. To use the sensing area, the sensor surface was chemically modified using (3-aminopropyl) triethoxysilane and glutaraldehyde, yielding covalently linked nanowire ssDNA adducts. Detection of hybridized DNA works by detecting the changes in the electrical current of the ssDNA-functionalized SiNW sensor, interacting with the targeted ssDNA in a label-free way. The developed biosensor shows selectivity for the complementary target ssDNA with linear detection ranging from 1.0 × 10−12 M to 1.0 × 10−7 M and an attained detection limit of 4.131 × 10−13 M. This indicates that the use of SiNW devices is a promising approach for the applications of ion detection and biomolecules sensing and could serve as a novel biosensor for future biomedical diagnosis.
Cardiovascular disease (CVD) is a major threat to global health, estimated to be the cause 30 % (17.3 million in 2008) of deaths every year, and the number of deaths caused by CVD is expected to increase further, reaching 23.3 million by 2030. Hence, there is a growing demand for simpler sample extraction, rapid screening results, and intervention of the subsequent analysis in emergency units. In this paper, we reviewed CVD biomarkers in blood- and saliva-based specimens. The history of cardiac biomarkers indicates that in the beginning, cardiac troponin I (cTnI) was a widely accepted 'gold standard' marker due to its high specificity and selectivity. Considering the advantages of salivary-based cardiac biomarkers, we examined correlations between non-invasive (salivary) and invasive (blood) diagnoses, and it was found that C-reactive protein (CRP) provides a better correlation. Despite the low abundance of salivary CRP, several reports displayed the detection limit down to pg/ml using existing technologies. Thus, salivary CRP has the potential to be used for future forefront diagnostics for the early assessment of cardiac risks.
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