TB and SERS

The plasma sample for this study was retrieved from our previous study (attached). In brief, a thousand of participants were recruited from community and hospital networks across eight provinces in northeastern Thailand. Of these, 500 cases were positive to interferon-gamma release assay (IGRA) or IGRA-positive and considered latent tuberculosis cases, while the other 500 individuals were IGRA-negative and served as healthy controls. The participants included 258 males and 742 females, aged 5 to 99 years. The study was approved by the Khon Kaen University Ethics Committee (Ethics number HE651163). All experiments were performed in accordance with relevant guidelines and regulations.
Protein was extracted from human plasma by published protocol. Then, the SERS measurements were conducted using a confocal Raman microscopic system (inVia Reflex confocal Raman microscope, Renishaw plc., UK). Each dried protein sample was individually mixed with sterile water to achieve a final concentration of 0.25 g/l. Subsequently, 2.0 µl of protein sample was carefully placed onto the center of silver-based SERS sensors and allowed to air-dry for 10 min. A Raman spectrum was collected from a central region on each SERS sensor using a 785 nm wavelength laser through a 50× objective lens. Each spectral acquisition was performed with 25 mW laser power and a 10-second exposure time. For each sample, spectral data were collected from 49 points covering a grid area of 7×7 at 15 µm steps.