Fabrication of and characterization of directional antibody-conjugated gold nanourchin colloid and effect of laser polarization on SERS detection of breast cancer biomarker in serum

Abstract

We describe the results of citrate-stabilized 100 nm gold nanourchins (GNU) functionalized and conjugated with monoclonal antibody (mAb) in directional orientation to investigate the interaction with breast cancer serum (BCS) overexpressed with CA 15–3 biomarker. UV-Vis, fluorescence, FT-NIR spectroscopy, and SERS with 637 nm Raman probe were employed for non-destructive analysis. UV-Vis spectroscopy exhibited two distinct peaks at 230 and 280 nm related to tyrosine (Tyr) and tryptophan (Trp) with the corresponding fluorescence peaks at 285 and 315 nm respectively. FT-NIR showed some new lines after the interaction such as CH2 combination in carbohydrates, and NH2 amino acids. Directional orientation indicated a higher SERS intensity than random due to higher parallel dipole moments of asymmetric molecules and the polarization sensitivity of GNU. The SERS signals increased significantly after the interaction and the intensity of the Raman lines varied nonlinearly with the laser power. The data were filtered using the filtfilt filter from scipy.signals, baseline corrected using the Improved Asymmetric Least Squares (isals) function from the pybaselines.Whittaker library, and normalized using the minmax_scale function from sklearn.preprocessing. The scikit-learn Principal Component Analysis (PCA) function was used to analyze the dataset by identifying the directions of maximum variability in the data.