A simple and rapid radioimmunoassay for human interleukin-6

An electrochemical paper-based hydrogel immunosensor to monitor serum cytokine for predicting the severity of COVID-19 patients

Analysis of cytokines levels in human serum is critical as it can be a "symptom diagnostic biomarker" in COVID-19, giving real-time information about human health status. Here, we present the construction and performance of a low-price immunosensor (∼US$0.428 per test) based on microfluidic paper-based system to detect cytokine for predicting the health status of COVID-19 patients. Interleukin-6 (IL-6) was selected as the detection model for the close relationship between IL-6 and COVID-19. The assay, which we integrated into foldable paper system, leverages the magnetic immunoassay, the streptavidin-horseradish peroxidase (HRP) associated with tetramethyl benzidine/hydrogen peroxide (TMB/H₂O₂) to amplify the signal for electrochemical readout. To improve the sensitivity of cytokine detection, a hybrid of gold nanoparticles (AuNPs) and polypyrrole (PPy) hydrogel was modified on the working electrode to increase the conductivity and improve the electron transfer rate. With our prototypic origami paper-based immunosensor operated in differential pulse voltammetry (DPV) mode, we achieved excellent results with a dynamic range from 5 to 1000 pg/mL and a lower detection limit (LOD) of 0.654 pg/mL. Furthermore, we evaluated the capability of the clinical application of the proposed immunosensor using human serum samples from a hospital. The results indicate that our proposed immunosensor has great potential in early diagnosing high-risk COVID-19 patients.

Fabrication of antibody microarrays by light-induced covalent and oriented immobilization

Antibody microarrays have important applications for the sensitive detection of biologically important target molecules and as biosensors for clinical applications. Microarrays produced by oriented immobilization of antibodies generally have higher antigen-binding capacities than those in which antibodies are immobilized with random orientations. Here, we present a UV photo-cross-linking approach that utilizes boronic acid to achieve oriented immobilization of an antibody on a surface while retaining the antigen-binding activity of the immobilized antibody. A photoactive boronic acid probe was designed and synthesized in which boronic acid provided good affinity and specificity for the recognition of glycan chains on the Fc region of the antibody, enabling covalent tethering to the antibody upon exposure to UV light. Once irradiated with optimal UV exposure (16 mW/cm(2)), significant antibody immobilization on a boronic acid-presenting surface with maximal antigen detection sensitivity in a single step was achieved, thus obviating the necessity of prior antibody modifications. The developed approach is highly modular, as demonstrated by its implementation in sensitive sandwich immunoassays for the protein analytes Ricinus communis agglutinin 120, human prostate-specific antigen, and interleukin-6 with limits of detection of 7.4, 29, and 16 pM, respectively. Furthermore, the present system enabled the detection of multiple analytes in samples without any noticeable cross-reactivities. Antibody coupling via the use of boronic acid and UV light represents a practical, oriented immobilization method with significant implications for the construction of a large array of immunosensors for diagnostic applications.

Modulation by progesterone of interleukin-6 production by gingival fibroblasts

The gingivitis associated with pregnancy has been attributed to increased concentrations of circulating estrogen and/or progesterone. However, the mechanism by which these steroids increase gingival inflammation is not known. Interleukin-6 (IL-6), a pleiotropic cytokine produced by many cell types including human gingival fibroblasts (hGF), is secreted in response to inflammatory challenges such as bacterial lipopolysaccharide and interleukin-1 (IL-1). This study tested the hypothesis that progesterone could modulate the local production of IL-6 by hGF. The effects of progesterone on IL-6 production were measured in vitro in serum-free, phenol red-free medium to eliminate possible effects of such medium additives. The concentration of IL-6 secreted into supernatant medium after a 24 hour challenge with IL-1 beta was estimated by radioimmunoassay. Total RNA from steroid-treated hGF was probed for IL-6 mRNA. In serum-free medium, progesterone dose-dependently and significantly (P < 0.05) inhibited IL-6 production by hGF, as did the glucocorticoids hydrocortisone (HC) and dexamethasone. At progesterone concentrations common in late pregnancy, IL-6 production was reduced to levels 40 to 50% of control. In addition, mRNA was significantly down-regulated by progesterone and HC, at both basal levels and after IL-1 beta challenge. These results suggest that high levels of progesterone during pregnancy affect the development of localized inflammation by down-regulation of IL-6 production, rendering the gingiva less efficient at resisting the inflammatory challenges produced by bacteria.

Relationship of functional and antigenic interleukin 6 to disease activity in inflammatory bowel disease

BACKGROUND

Intestinal and peripheral blood mononuclear cell interleukin 6 (IL-6) production in inflammatory bowel disease might present an increased quantity of IL-6 into the systemic circulation. The aim of the present study was to examine the relationship of circulatory IL-6 to the clinical and laboratory expression of inflammatory bowel disease in children.

METHODS

Sera were obtained from 26 children with ulcerative colitis, 49 with Crohn's disease, and 29 control patients. Serum functional IL-6 was measured by a bioassay and antigenic IL-6 by enzyme linked immunosorbent assay.

RESULTS

Functional and antigenic serum IL-6 levels were higher in Crohn's disease than in ulcerative colitis or controls (P < 0.0001) and higher in ulcerative colitis than controls (P < 0.04). In Crohn's disease affecting the colon, functional and antigenic serum IL-6 levels were greater than in disease limited to the small bowel (P < 0.002). Increasing disease severity was reflected by increasing antigenic but not functional IL-6 levels in both Crohn's disease (P < 0.001) and ulcerative colitis (P < 0.02). Serum antigenic IL-6 levels were related to acute phase reactants in both diseases (P < 0.001) whereas functional levels were not.

CONCLUSIONS

Our results underscore the importance of using both functional and antigenic methodologies in examining the relationship of circulating cytokines to the clinical manifestations of inflammatory bowel disease.