Rapid Isolation and Diagnosis of Brain Injury Marker in Plasma by SERS Nanosensor

Introduction S100B, calcium-binding protein, is an important biomarker for the clinical diagnosis for brain damage. It is also associated with neurodegenerative diseases like Alzheimer or other chronic neurological diseases.... [ view full abstract ]

Introduction

S100B, calcium-binding protein, is an important biomarker for the clinical diagnosis for brain damage. It is also associated with neurodegenerative diseases like Alzheimer or other chronic neurological diseases. Due to its clinical value, it is critical to develop a rapid and sensitive methodology for its detection in biological fluids. This work presents a new nanosensor for the combined isolation and Raman detection of S100B in blood by handheld devices.

Method

Extractor nanomaterial was fabricated by functionalising magnetic gold nanoparticles with monoclonal anti-S100B antibody thiol-ended fragments. To block the nanoparticle’s remaining bare sites and eliminate nonspecific binding of foreign molecules, an alkanethiol was chemisorbed onto the gold surface of the nanoparticles. The functionalized nanoparticles were used for the selective capture of S100B from plasma within 15 minutes. After magnetic separation using a simple magnet, the protein-bound nanoparticles were washed and reconstituted in a releasing buffer to release the purified protein for detection. The released protein was scanned by surface enhanced Raman spectroscopy (SERS) using a nanostructured gold substrate and handheld device (fig.1).

Results and Discussion

To synthesis target-specific extractor nanomaterial for S100, thiol-ended antibody fragments were developed by reducing the disulphide bonds of the antibody’s hinge region and the formed free SH groups covalently bound to the nanoparticles gold surface in a highly oriented monolayer. Using this oriented immobilization strategy, the capture efficiency of the extractor nanoparticles was maximized. After selective capture of the protein from blood samples within 15 minutes, it was released from the extractor nanomaterial within 5 minutes by manipulating the pH of nanoparticles. The released protein was then loaded onto a nanostructured gold substrate and detected down to 100 pM by handheld device (fig.2). The wide optical field and the raster orbital scanning mode of the handheld Raman spectrometer allowed for reproducible and average SERS spectra of the protein to be acquired within 10 seconds. The method was cross validated against ELISA to confirm the determination of S100B in the samples. The new method has strong potential for the rapid and sensitive screening of protein biomarkers and environmental toxins in biomedical and environmental monitoring applications.