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Vitamin D is associated with various diseases such as obesity, digestive problems, osteoporosis, depression, and infections, which has emerged as an interest in public healthcare. Recently, vitamin D has received more attention because of the potential implication with coronavirus disease 2019. In this study, we developed a localized surface plasmon resonance (LSPR) aptasensor based on polyethylene-glycol(PEG)-free gold nanorods (AuNRs) for the wide-range and direct detection of 25-hydroxyvitamin D 3. The surfactant on AuNRs was removed by exchanging with polystyrene sulfonate (PSS) instead of PEG then the PSS was exchanged with citrate. By exchanging the stabilizer of AuNRs from PEG to PEG-free (i.e., citrate), the sensing efficiency of LSPR aptasensor was significantly improved. Additionally, LSPR aptasensor was functionalized with aptamer and blocking agent to enhance the sensing performance. The LSPR aptasensor achieved the direct, highly sensitive, and selective detection of 25-hydroxyvitamin D 3 over a wide concentration range (0.1–105 ng/mL), with a limit of detection of 0.1 ng/mL. This detection range included the concentration of vitamin D from deficiency to excess. The PEG-free AuNR-based LSPR aptasensor affords a new avenue for the development of robust sensing technology for vitamins. • LSPR aptasensor developed for wide-range detection of 25-hydroxyvitamin D 3 with polyethylene-glycol(PEG)-free gold nanorod. • The PEG-free gold nanorod LSPR aptasensor can measure wide range concentrations (0.1–105 ng/mL) of 25-hydroxyvitamin D 3. • The PEG-free gold nanorod based LSPR aptasensor was able to detect 25-hydroxyvitamin D 3 in human serum albumin. [ABSTRACT FROM AUTHOR]

• LSPR aptasensor has been developed for label-free detection of salivary cortisol with high sensitivity and selectivity. • Using the LSPR aptasensor, a wide range of cortisol concentrations (0.1–1000 nM) per a single droplet (5 μL) was detectable. • Our method was able to detect salivary cortisol, and the sensing performance was comparable to that of ELISA. Cortisol, which is a stress biomarker that causes various mental disorders, is found in sweat, saliva, blood, and urine. Because mental disorders resulting from stress are a silent contributor to various diseases, the detection of cortisol level is an important step in their prevention. Here, we developed a highly sensitive, localized surface plasmon resonance (LSPR) aptasensor for the direct detection of cortisol in saliva. The LSPR aptasensor was constructed using gold nanoparticles of different sizes. Subsequently, the surface of the LSPR substrate was immobilized using an aptamer for capturing cortisol. The detection capability of the LSPR aptasensor was compared with that of the antibody- immobilized sensor. The LSPR aptasensor displayed excellent detection capability for a wide range of cortisol concentrations extending from 0.1–1000 nM with a detection limit of 0.1 nM. In addition, the LSPR aptasensor was able to selectively detect cortisol among other substances with similar chemical structures (e.g., cortisone, corticosterone, progesterone, and triamcinolone). These results indicate that the LSPR aptasensor may be used for the highly sensitive and selective detection of cortisol in salivary samples. [ABSTRACT FROM AUTHOR]

Vitamin D has been identified as an essential biomarker for various diseases such as rheumatoid arthritis, cancer, and cardiovascular diseases. Recently, many reports have demonstrated a potential link between vitamin D and systemic infections, including coronavirus disease 2019. The villi of the small intestine increase the surface area of the intestinal walls, demonstrating exceptionally efficient absorption of nutrients in the lumen and adding digestive secretions. In this study, based on the villi structure, we developed a bio-inspired silver nanovilli-based sandwich-type surface enhanced Raman scattering aptasensor for the ultrasensitive and selective detection of 25-hydroxy vitamin D 3. The densely packed nanovilli structure enhanced the Raman signal, forming hotspots owing to its large surface area. Using experiments and electromagnetic simulations, we optimized the nanovilli structure as a SERS sensor. The sandwich-type aptasensor was designed using an aptamer and 4-Phenyl-1,2,4-triazoline-3,5-dione-methylene blue complex. The nanovilli-based aptasensor could sensitively detect various concentrations of 25-hydroxy vitamin D 3 , ranging from those found in deficient to excess conditions. The detection limit of the nanovilli-based sandwich-type aptasensor for 25-hydroxy vitamin D 3 was 0.001 ng/mL, which is much lower than the deficiency concentration, and was detectable even in the human serum. In addition, our proposed sensor exhibited good repeatability (17.76%) and reproducibility (7.47%). Moreover, the nanovilli-based sandwich-type SERS aptasensor could selectively distinguish 25-hydroxy vitamin D 3 from other vitamins. The silver nanovilli-based sandwich-type surface enhanced Raman scattering aptasensor opens a new avenue for the development of a bio-inspired vitamin-sensing platform. • Developed a bio-inspired AgNV-based aptasensor for detection of 25OHD3. • The LOD of the AgNV-based aptasensor was 0.001 ng/mL with human serum solution. • The AgNV-based aptasensor could selectively detect 25OHD3 from other vitamins. • This method can shed light on the development of SERS-based vitamin sensors. [ABSTRACT FROM AUTHOR]