Highly Reproducible Au-Decorated ZnO Nanorod Array on a Graphite Sensor for Classification of Human Aqueous Humors

Abstract

Gold-decorated, vertically grown ZnO nanorods (NRs) on a flexible graphite sheet (Au/ZnONRs/G) were developed for surface-enhanced Raman scattering (SERS)-based biosensing to identify trace amounts of human aqueous humors. This Au/ZnONRs/G SERS-functionalized sensor was fabricated via two steps: hydrothermal synthesis-induced growth of ZnO NRs on graphite sheets for nanostructure fabrication, followed by e-beam evaporator-induced gold metallization on ZnONRs/G for SERS functionalization. The thickness of the Au layer and the height of the ZnO NRs for enhancing SERS performance were adjusted to maximize Raman intensity, and the optimized Au/ZnONRs/G nanostructures were verified by the electric finite element computational models to maximize the electric fields. The proposed Au/ZnONRs/G SERS sensor showed an enhancement factor of 2.3 × 10 via rhodamine 6G Raman probe and excellent reproducibility (relative standard deviation of <10%) via Raman mapping of a SERS active area with a square of 100 × 100 μm. To evaluate the actual bioapplicability of point-of-care-testing (POCT) analysis in clinics, SERS data acquisition was performed with an integration time of 1 s from a 1 μL analytic droplet of the sample. The performance of this Au/ZnONRs/G sensor was evaluated using human aqueous humors with cataract and two oxidative stress-induced eye diseases, age-related macular degeneration, and diabetic macular edema. These three eye diseases could be identified without any labeling or modification using the Au/ZnONRs/G SERS sensor and the computational algorithm incorporating a support vector machine and multivariate statistical prediction. Therefore, these findings indicate that our label-free, highly reproducible and flexible Au/ZnONRs/G SERS-functionalized sensor supported by a multivariate statistics-derived bioclassification method has great potential in POCT applications for identifying eye diseases.

Gold nanoparticles in ophthalmology

“…Interestingly, other biosensors based on gold wire or gold layer, whose properties differ from those of nanoparticles, were also developed for the classification of human lachrymal liquid or human aqueous humors . These new platforms could be developed for point‐of‐care diagnosis of ocular pathologies.…”

Rapid label-free identification of Klebsiella pneumoniae antibiotic resistant strains by the drop-coating deposition surface-enhanced Raman scattering method

“…The SERS-EF for the R6G peak at 1361 cm −1 was determined to be 11.3 × 10 6 . Since SERS activity was evaluated based on an enhancement factor (EF) that was commonly N10 4 , this SERS-EF value indicates the presence of strong SERS activity for the proposed Platypus® gold substrate [36][37][38]. This SERS activity was responsible for the uniform distribution of nanoparticles (grain) on the Platypus® gold substrate (Fig.…”

Enhancement of the Au/ZnO-NA Plasmonic SERS Signal Using Principal Component Analysis as a Machine Learning Approach

“…Additionally, researchers have published a label-free biological classification system based on an Au/ZnO-NR/G sensor that was implemented using a PCA projected SVM-classified calculation algorithm. The group used aqueous human tumor samples from patients with cataracts and two oxidative stress-induced eye diseases, which were analyzed using the proposed sensor [10]. Researchers have demonstrated a SERS platform to help ensure normal delivery without infection and premature delivery of maternal diseases.…”