The cartridges were kept at 23C during the measurement through a thermalized holder, and rapid mixing of the solution was provided by a magnetic stirring bar rotating at 30 Hz. that vaccinated subjects displayed a larger Alosetron (Hydrochloride(1:X)) quantity of total Ig and a lower portion of IgA relative to the population of convalescent unvaccinated subjects. Keywords:label-free biosensor, reflective phantom interface, antibody repertoire, quick detection, wash-free assay, serological assay, immunoglobulins, IgA == 1. Introduction == The easy access to individual antibody repertoire, which results from a complex interplay of factors (1), would constitute an important achievement in providing epidemiological information, controlling disease outbreaks, and developing effective clinical therapeutics and vaccine strategies (2). During the COVID-19 pandemic, quantitative measurement of SARS-CoV-2 antibody titer enabled assessing variability in the immune response to contamination, evaluating vaccine efficacy and potential for long-term immunity, and identifying donors for blood transfusion therapy (310). Large-scale antibody quantification and characterization are commonly accomplished using enzyme-linked immunosorbent assay (ELISA) in laboratory facilities and lateral circulation assay (LFA) as the quick serological test at the point of care (POC). Notably, both ELISA and LFA do not allow parallel quantification of unique antibodies and are thus not suitable for the fingerprinting of antibody repertoire (1113). Multiplexed antigen assay platforms represent a key development for TFR2 the accurate identification of antibody repertoires (14). A high-throughput approach is offered by peptide microarrays, which enable identifying immunoreactive epitopes from your blood of individuals with different histories of exposure to infective brokers (1519). The relevance of this approach in serodiagnostics is usually, however, still to be confirmed. In the context of SARS-CoV-2, a few multiplexed antigen assay platforms have been proposed, which include fluorescence protein microarray (20,21), as well as bead-based methods (22). Despite the validity of these methodologies, the COVID-19 pandemic experience has highlighted the crucial need for affordable new assay types that offer highly sensitive, quantitative, multiplexed, and quick immune protection profiling. Here, we show that it is possible to discriminate antibody repertoires in serum up to the resolution of a single SARS-CoV-2 computer virus variant with a simple yet sensitive and quantitative assay based on label-free readout of an antigen microarray, without additional markers to provide the transmission (e.g., colorimetric, fluorescent, and chemiluminescent). With the same multiplex assay, it is also possible to discriminate between vaccinated and unvaccinated subjects through their total Ig profile and IgA amount. These results are based on a multi-spot biosensing technique, the reflective phantom interface (RPI) (23,24), which enables real-time quantification of molecular binding. Overall, the proposed antibody fingerprinting method paves the way to POC characterization of antibody repertoire against specific panels of protein antigens for purposes of either individual diagnostic or populace screening. == 2. Methods == == 2.1. Serum samples, reagents, and materials == All receptor-binding domain name (RBD) of SARS-CoV-2 spike proteins (WT-RBD,-RBD,-RBD,-RBD, ando-RBD) obtained from HEK293 human embryonic kidney immortalized cell collection were purchased from Sino Biological (Beijing, China). Nucleocapsid protein was obtained from InvivoGen (Toulouse, France; product code his-sars2-n). WT-LtRBD was expressed in the protozoa parasiteLeishmania tarentolaeand purified (Patent N. IT 1020210000041625). Trimeric spike protein HexaPro was donated by Anton Schmitz and Gnter Mayer (26,27). Rabbit polyclonal antibody anti-human IgG was obtained Abcam (Cambridge, UK; product code ab7155). Goat polyclonal antibody anti-human IgA was obtained from Invitrogen (Rockford, IL, USA; product code SA5-10252). Wedge-like glass chips Alosetron (Hydrochloride(1:X)) (F2 optical glass, Schott), with a 5 angle, a maximum thickness of 2 mm, and a size of 8 mm 12 mm, were coated with SiO2to form an anti-reflection layer of 80 nm. After ozone cleaning, the chips were dip-coated with a copolymer of dimethylacrylamide (DMA),N-acryloxysuccinimide (NAS), and 3-(trimethoxysilyl)propyl methacrylate (MAPS)copoly(DMANASMAPS) called MCP2 purchased from Lucidant Polymers Inc. (Sunnyvale, CA, Alosetron (Hydrochloride(1:X)) USA;28). All the buffers and reagents were purchased from Sigma-Aldrich (St. Louis, MO, USA) and prepared using Milli-Q pure water. Plasma samples were obtained from healthy volunteer donors and patients at the Sacco Hospital in Milan. == 2.2. Preparation of RPI antigen microarray cartridge == Antigen proteins and control antibodies were covalently immobilized on the surface of RPI sensing chips in spots with 150200-m diameter. Droplets of spotting buffer (phosphate-buffered saline (PBS) 1, pH 7.4, and trehalose 50 mM) containing probe proteins at concentrations of 1 1 mg/mL were deposited around the chip surface by an automated, non-contact dispensing system (sciFLEXARRAYER S3; Scienion AG, Berlin, Germany). After overnight incubation,.
