Aluminum Foil vs. Gold Film: Cost-Effective Substrate in Sandwich SERS Immunoassays of Biomarkers Reveals Potential for Selectivity Improvement.

The first application of aluminum foil (Al F) as a low-cost/high-availability substrate for sandwich immunoassay using surface-enhanced Raman spectroscopy (SERS) is reported. Untreated and unmodified Al F and gold film are used as substrates for sandwich SERS immunoassay to detect tuberculosis biomarker MPT64 and human immunoglobulin (hIgG) in less than 24 h. The limits of detection (LODs) for tuberculosis (TB) biomarker MPT64 on Al foil, obtained with commercial antibodies, are about 1.8-1.9 ng/mL, which is comparable to the best LOD (2.1 ng/mL) reported in the literature for sandwich ELISA, made with fresh in-house antibodies. Not only is Al foil competitive with traditional SERS substrate gold for the sandwich SERS immunoassay in terms of LOD, which is in the range 18-30 pM or less than 1 pmol of human IgG, but it also has a large cost/availability advantage over gold film. Moreover, human IgG assays on Al foil and Si showed better selectivity (by about 30-70% on Al foil and at least eightfold on Si) and a nonspecific response to rat or rabbit IgG, in comparison to the selectivity in assays using gold film.

Development and validation of hybrid Brillouin-Raman spectroscopy for non-contact assessment of mechano-chemical properties of urine proteins as biomarkers of kidney diseases.

BACKGROUND: Proteinuria is a major marker of chronic kidney disease (CKD) progression and the predictor of cardiovascular mortality. The rapid development of renal failure is expected in those patients who have higher level of proteinuria however, some patients may have slow decline of renal function despite lower level of urinary protein excretion. The different mechanical (visco-elastic) and chemical properties, as well as the proteome profiles of urinary proteins might explain their tubular toxicity mechanism. Brillouin light scattering (BLS) and surface enhanced Raman scattering (SERS) spectroscopies are non-contact, laser optical-based techniques providing visco-elastic and chemical property information of probed human biofluids. We proposed to study and compare these properties of urinary proteins using BLS and SERS spectroscopies in nephrotic patient and validate hybrid BLS-SERS spectroscopy in diagnostic of urinary proteins as well as their profiling. The project ultimately aims for the development of an optical spectroscopic sensor for rapid, non-contact monitoring of urine samples from patients in clinical settings. METHODS: BLS and SERS spectroscopies will be used for non-contact assessment of urinary proteins in proteinuric patients and healthy subjects and will be cross-validated by Liquid Chromatography-Mass Spectrometry (LC-MS). Participants will be followed-up during the 1 year and all adverse events such as exacerbation of proteinuria, progression of CKD, complications of nephrotic syndrome, disease relapse rate and inefficacy of treatment regimen will be registered referencing incident dates. Associations between urinary protein profiles (obtained from BLS and SERS as well as LC-MS) and adverse outcomes will be evaluated to identify most unfavored protein profiles. DISCUSSION: This prospective study is focused on the development of non-contact hybrid BLS - SERS sensing tool and its clinical deployment for diagnosis and prognosis of proteinuria. We will identify the most important types of urine proteins based on their visco-elasticity, amino-acid profile and molecular weight responsible for the most severe cases of proteinuria and progressive renal function decline. We will aim for the developed hybrid BLS - SERS sensor, as a new diagnostic & prognostic tool, to be transferred to other biomedical applications. TRIAL REGISTRATION: The trial has been approved by ClinicalTrials.gov (Trial registration ID NCT04311684). The date of registration was March 17, 2020.

Detection of Paracetamol in Water and Urea in Artificial Urine with Gold Nanoparticle@Al Foil Cost-efficient SERS Substrate.

We demonstrated that a cost-efficient, easy to prepare, hybrid SERS substrate-gold nanoparticles (AuNPs) on untreated Al foil (AlF) can effectively detect pharmaceuticals, such as paracetamol and clinical biomarkers, like urea in artificial urine. The limit of detection (LOD) for paracetamol on AuNPs on AlF is superior (0.1 vs. 1 mM ) to the LOD reported for SERS detection of paracetamol in the literature. For SERS detection of urea in urine, AuNPs on both Al foil and Au film performed much better than AuNPs on glass, in terms of the concentration range, linearity and LOD. However, assay on AuNPs on AlF showed a better semi-logarithmic trendline with R2 = 0.98 than an assay on AuNPs on Au film with R2 = 0.94. They have comparable sensitivity with LOD 0.024 and 0.017 M, respectively. The limit of quantification (LOQ) of the former is 0.026 M, which makes it sufficient for the quantification of urea in urine at both normal and pathophysiological (0.03 - 0.15 M) concentration.

In situ microarray fabrication and analysis using a microfluidic flow cell array integrated with surface plasmon resonance microscopy.

Surface Plasmon Resonance Microscopy (SPRM) is a promising label-free analytical tool for the real-time study of biomolecule interactions in a microarray format. However, flow cell design and microarray fabrication have hindered throughput and limited applications of SPRM. Here we report the integration of a microfluidic flow cell array (MFCA) with SPRM enabling in situ microarray fabrication and multichannel analysis of biomolecule probe-target interactions. We demonstrate the use of the MFCA for delivery of sample solutions with continuous flow in 24 channels in parallel for rapid microarray creation and binding analysis while using SPRM for real-time monitoring of these processes. Label-free measurement of antibody-antibody interactions demonstrates the capabilities of the integrated MFCA-SPRM system and establishes the first steps of the development of a high-throughput, label-free immunogenicity assay. After in situ probe antibody immobilization, target antibody binding was monitored in real time in 24 channels simultaneously. The limit of detection for this particular antibody pair is 80 ng/mL which is approximately 6 times lower than the industry recommended immunogenicity assay detection limit. The integrated MFCA-SPRM system is a powerful and versatile combination for a range of array-based analyses, including biomarker screening and drug discovery.