Ultrasensitive SERS platform made via femtosecond laser micromachining for biomedical applications

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a research method in which a lack of cost-effective, versatile platforms with high enhancement factor (EF) is still a major obstacle to its widespread use. The platforms should be also easy to manufacture, stable in time (for weeks or even for months) and manufactured with a highly reproducible method.We demonstrate SERS platforms based on silicon modified on the surface by laser ablation and covered with SERS-active metal. The substrates were fabricated by a femtosecond laser, thus the method is simple, very fast and creates highly uniform SERS platforms in a large number. The platform was tested with para-mercaptobenzoic acid (p-MBA) in terms of sensitivity and reproducibility. The calculated EF was at the level of 108 and the standard deviation (SD) gives 7% for 10−6 M solution of p-MBA based on the intensity of the band at 1073 cm−1. Optimized SERS substrate also exhibits excellent stability for up to six months.We also give the proof-of-concept of using our platform and, for the first time, the SERS analysis of the most important human opportunistic fungal pathogen Candida spp. (Candida glabrata, Candida albicans SN148 and C. albicans BWP17). Finally, the chemometric analysis in the form of Principal Component Analysis (PCA) allowed to strain differentiation of Candida spp., and to distinguish the studied Candida species from Gram-positive bacterial samples with Staphylococcus aureus. Our results demonstrate that the proposed SERS platform is a perfect substrate for detection, identification and differentiation between fungal and bacterial pathogens using SERS technique.

Keywords

• Surface-enhanced Raman spectroscopy
• SERS
• Femtosecond laser
• Laser ablation
• Candida
• Staphylococcus aureus