Surface-enhanced Raman spectroscopy of blood plasma and serum using Ag and Au nanoparticles: a systematic study

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a good candidate for the development of fast and easy-to-use diagnostic tools, possibly used on biofluids in point-of-care or screening tests. In particular, label-free SERS spectra of blood serum and plasma, two biofluids widely used in diagnostics, could be used as a metabolic fingerprinting approach for biomarker discovery. This study aims at a systematic evaluation of SERS spectra of blood serum and plasma, using various Ag and Au aqueous colloids, as SERS substrates, in combination with three excitation lasers of different wavelengths, ranging from the visible to the near-infrared. The analysis of the SERS spectra collected from 20 healthy subjects under a variety of experimental conditions revealed that intense and repeatable spectra are quickly obtained only if proteins are filtered out from samples, and an excitation in the near-infrared is used in combination with Ag colloids. Moreover, common plasma anticoagulants such as EDTA and citrate are found to interfere with SERS spectra; accordingly, filtered serum or heparin plasma are the samples of choice, having identical SERS spectra. Most bands observed in SERS spectra of these biofluids are assigned to uric acid, a metabolite whose blood concentration depends on factors such as sex, age, therapeutic treatments, and various pathological conditions, suggesting that, even when the right experimental conditions are chosen, great care must be taken in designing studies with the purpose of developing diagnostic tests.

Blood equivalent phantom vs whole human blood, a comparative study

“…38 Result of the data processing (Fig. 8) shows that the acquired spectral pro¯le of plasma is very similar to those presented in the literature, 39,40 with prominent bands related mostly to the presence of proteins. Spectrum of saline is, as expected, void of identi¯able features, and the detected signal is on similar levels as the background and noise interference.…”

Identification of Individual Exosome-Like Vesicles by Surface Enhanced Raman Spectroscopy

“…[36] Moreover, other less stringent purification protocols (i.e. UC and commercial precipitation kits) suffer from limited purity due to co-purification of vesicleindependent proteins and nucleic acids, which might preclude the AuNP from interacting with the ELVs [42] and interfere with the Raman fingerprint.…”

SERS analysis of serum for detection of early and locally advanced breast cancer

“…Recently, several groups reported SERS spectra of blood plasma or serum [16,[18][19][20][21][22], often with diagnostic purposes. We also reported that using metal nanoparticles as SERS substrates in the absence of aggregating agents, filtration of proteins from serum or plasma is important to rapidly obtain intense, repeatable SERS spectra of these biofluids [19].…”