Microfluidic fabrication of SERS-active microspheres for molecular detection

Abstract

In this paper, we demonstrated a microfluidic system for fabricating microspheres with hierarchical surface nanopatterns for molecular detection based on surface-enhanced Raman scattering (SERS). Briefly, a photocurable silica suspension was emulsified into monodisperse droplets using a microfluidic device composed of two coaxial glass capillaries. The silica particles in each droplet protruded through the interface and spontaneously formed a hexagonal array. After polymerization of the droplets, we selectively decorated the exposed areas of the silica particles with silver nanoparticles through electroless deposition. The resulting hierarchically-structured microspheres showed high sensitivity and fast binding kinetics in molecular detection based on SERS, owing to the dense array of hot spots on each microsphere and high mobility of the microspheres, respectively. Notably, the SERS signals from molecules adsorbed on the microspheres could be detected in both the dried and suspension states. In addition, we demonstrated that the SERS-active microspheres can be functionalized into structural colored or magnetoresponsive microspheres for advanced applications.

Surface-enhanced Raman spectroscopy at single-molecule scale and its implications in biology

“…As indicated in figure 4a, by implementing a flow-based system with higher throughput, the detected event can be accomplished in a very short analysis time [75]. Due to the advantages of the microfluidic system in SERS, immunoassays for protein detection have been developed based on microfluidics by SERS [76,77]. By using a magnetic pull-down system, proteins and DNA from viruses were detected effectively and such a system was very beneficial for SM or single-particle SERS study [78,79].…”

Microfluidic Platforms toward Rational Material Fabrication for Biomedical Applications

“…Microfluidics is versatile for producing structural color barcode micro/nanoparticles as biosensors that can be encoded with tunable or even multiple colors (Figure d) . These structural color barcode micro/nanoparticles can be formed by means of droplet evaporation, optofluidic, droplet template generation, multiple emulsification, and UV cross‐linking of photocurable resins on specifically designed microfluidic devices, demonstrating attractive potentials in the monitoring and even quantification of different biomarkers with high physiological and medical significance such as microRNAs (Figure e) and skin interstitial fluid (Figure f) . By simply functionalized with SERS‐active nanotags, structural color micro/nanoparticles formed by microfluidics can realize significantly improved sensitivity in biomarker detection due to the coupling effects .…”

Bioanalytical application of surface‐ and tip‐enhanced Raman spectroscopy

“…The unique formation of droplets in a flow channel is utilized to generate droplets loaded with silica solution. These droplets are polymerized and covered with silver nanoparticles to produce SERS‐active microbeads . In a similar procedure, gold nanoparticle coated chitosan microbeads are fabricated, which subsequently can be used as SERS substrate .…”