Developing an improved optical biosensing system based on gold nanoparticles acting as interferometric enhancers in Lactoferrin detection

We report for the first time the whole development of a biosensing system based on the Interferometric Optical Detection Method (IODM) enriched with gold nanoparticles (AuNPs), acting as interferometric enhancers for improving the performance of immunoassays. For this purpose, the Lactoferrin sandwich immunoassay model was employed. We describe in detail the entire value chain from the AuNPs production, its functionalization, and characterization with anti-Lactoferrin (anti-LF), the biosensing response of these conjugates as well as their corresponding calculation of the kinetic constants, performance comparison of the readout interferometric signals versus Scanning Electron Microscopy (SEM) and the percentage of the sensing surface covered. Finally, a Lactoferrin sandwich immunoassay was carried out and correlated with Enzyme-Linked ImmunoSorbent Assay (ELISA), and the Limit of Detection and sensitivity figures were obtained. As a result, we demonstrate how the AuNPs act as interferometric amplifiers of the IODM for improving the biosensing response, opening the possibility of being applied in multiple biological detection applications.

Developing an Optical Interferometric Detection Method based biosensor for detecting specific SARS-CoV-2 immunoglobulins in Serum and Saliva, and their corresponding ELISA correlation

The standard rapid approach for the diagnosis of coronavirus disease 2019 (COVID-19) is the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. The detection of specific anti-SARS-CoV-2 immunoglobulins is crucial for screening people who have been exposed to the virus, whether or not they presented symptoms. Recent publications report different methods for the detection of specific IgGs, IgMs, and IgAs against SARS-CoV-2; these methods mainly detect immunoglobulins in the serum using conventional techniques such as rapid lateral flow tests or enzyme-linked immunosorbent assay (ELISA). In this article, we report the production of recombinant SARS-CoV-2 spike protein and the development of a rapid, reliable, cost-effective test, capable of detecting immunoglobulins in serum and saliva samples. This method is based on interferometric optical detection. The results obtained using this method and those obtained using ELISA were compared. Owing to its low cost and simplicity, this test can be used periodically for the early detection, surveillance, detection of immunity, and control of the spread of COVID-19.

Arrays of resonant nanopillars for biochemical sensing

In this Letter, we demonstrate for the first time the experimental capability for the biochemical sensing of resonant nanopillars (RNPs) arrays. These arrays are fabricated over a glass substrate and are optically integrated from the backside of this substrate. The reflectivity profiles of the RNPs arrays are measured by infiltrating different ethanol fractions in water in order to evaluate the optical response for the different refractive indexes, which range from 1.330 to 1.342. A linear fit of the resonant modes shift is observed as a function of the bulk refractive index of the liquid infiltrated. For the type of transducer analyzed, a relative sensitivity of 10017  cm(-1)/Refractive Index Unit (RIU) is achieved, allowing us to reach a competitive Limit of Detection (LoD) in the order of 1×10(-5)  RIU.

Insulin directly stimulates VEGF-A production in the glomerular podocyte

Podocytes are critically important for maintaining the integrity of the glomerular filtration barrier and preventing albuminuria. Recently, it has become clear that to achieve this, they need to be insulin sensitive and produce an optimal amount of VEGF-A. In other tissues, insulin has been shown to regulate VEGF-A release, but this has not been previously examined in the podocyte. Using in vitro and in vivo approaches, in the present study, we now show that insulin regulates VEGF-A in the podocyte in both mice and humans via the insulin receptor (IR). Insulin directly increased VEGF-A mRNA levels and protein production in conditionally immortalized wild-type human and murine podocytes. Furthermore, when podocytes were rendered insulin resistant in vitro (using stable short hairpin RNA knockdown of the IR) or in vivo (using transgenic podocyte-specific IR knockout mice), podocyte VEGF-A production was impaired. Importantly, in vivo, this occurs before the development of any podocyte damage due to podocyte insulin resistance. Modulation of VEGF-A by insulin in the podocyte may be another important factor in the development of glomerular disease associated with conditions in which insulin signaling to the podocyte is deranged.

Apoptosis: from advances in PD to therapeutic targets in DM

A high glucose concentration is shared by peritoneal dialysis (PD) and diabetes mellitus (DM). High glucose leads to tissue injury in diabetes. Peritoneal dialysis research has emphasized the role of glucose degradation products in tissue injury. Apoptosis induction is one of the mechanisms of tissue injury induced both by glucose and glucose degradation products. We now review the role of apoptosis and its regulation by glucose degradation products in antibacterial defense and loss of renal function in diabetes mellitus and peritoneal dialysis. The pathogenic role of the recently identified glucose degradation product 3,4-di-deoxyglucosone- 3-ene (3,4-DGE) is detailed. Available therapeutic strategies include the use of peritoneal dialysis solutions containing a low concentration of glucose degradation products. Based on preclinical results, specific targeting of apoptosis regulatory factor should be explored in the clinical setting.

Prevalence of IgG anti-{alpha}-fodrin antibodies in Sjogren's syndrome

The objective of this study was to determine the prevalence of antibodies against alpha-fodrin (alpha-fodrin) of the immunoglobulin G (IgG) isotype in Sjögren's syndrome (SS), as defined by European Community Study Group (ESG) and ESG-modified criteria. We arrived at the prevalence and mean concentrations of IgG anti-alpha-fodrin antibodies using enzyme-linked immunosorbent assay (ELISA) in 507 patients with SS, primary SS (pSS), and secondary SS (sSS), classified according to either the ESG or the ESG-modified criteria. IgG anti-alpha-fodrin antibodies were detected in 6/507 (1.2%) and 4/228 (1.7%) of the SS group, according to the ESG or ESG-modified criteria, respectively. Similar prevalence was found for patients with pSS or sSS. Anti-Ro/SSA antibodies were present in 151/409 (36.9%) vs. 149/213 (70.0%) of the SS group, 85/195 (43.6%) vs. 83/101 (82.2%) of the pSS group, and 66/214 (30.8%) vs. 66/112 (58.9%) of the sSS group. Anti-La/SSB antibodies were detected in 77/403 (19.1%) vs. 73/212 (34.4%) of the SS group, 47/194 (24.2%) vs. 45/101 (44.5%) of the pSS group, and 30/209 (14.3%) vs. 28/111 (25.2%) of the sSS group. No clinical associations were found. Only two IgG anti-alpha-fodrin-positive sera were anti-Ro/SSA-negative. We conclude that IgG antibodies against alpha-fodrin are present in a small percentage of people with SS, pSS, and sSS. The lower prevalence in patients classified according to the ESG criteria reflects the lower specificity of these criteria. IgG anti-alpha-fodrin antibodies can be detected in some SS patients whose sera do not contain anti-Ro/SSA antibodies.

Phosphofructokinase from Dictyostelium discoideum is a potent inhibitor of tubulin polymerization

We identified the nonallosteric phosphofructokinase from the slime mold Dictyostelium discoideum as a potent protein factor that inhibits the rate of polymerization of tubulin at a molar ratio of 1 molecule to about 300 tubulin dimers for half-maximal action (IC50 = 32 nM). This effect was (i) assessed by turbidity measurements, pelleting of microtubules, and electron microscopy, (ii) observed when tubulin assembly was induced by taxol as well as by GTP in the presence of microtubule-associated proteins or glutamate, and (iii) specific as it was not produced by the phosphofructokinase from rabbit muscle. Also in contrast to the latter, neither tubulin nor microtubules modified the catalytic activity of the slime mold isozyme. Immunoelectron microscopy provided further evidence that D. discoideumphosphofructokinase physically interacts with tubulin, leading to the formation of aggregates. The process seems to be reversible since microtubules eventually formed in the presence of the inhibitor with concomitant reduction of tubulin aggregates. Limited proteolysis by subtilisin showed that the hypervariable C-termini of tubulin is not involved in the interaction with the enzyme. The possible physiological relevance of this novel function of D. discoideum phosphofructokinase different from its glycolytic action is discussed.

Evaluation of Dirofilaria immitis excretory/secretory products for seroepidemiological studies on human dirofilariosis

The usefulness of excretory/secretory (E/S) products of adult Dirofilaria immitis for the diagnosis of human dirofilariosis was evaluated in 97 human sera using an ELISA and a Western Blot analysis with E/S antigens. Results of the ELISA analysis show that in healthy individuals from an endemic area seropositivity is high (22%). Immuno Blot analysis shows that the reaction pattern with E/S antigens differentiates healthy seropositives, which recognize a 43 kDa band, from patients with pulmonary dirofilariosis, which specifically recognize bands between 22-28 kDa.

Serological diagnosis of subcutaneous dirofilariosis

We present serological evidence that Dirofilaria immitis was the causative agent of subcutaneous nodules in two patients. ELISA and enzyme-linked immunoblot analysis showed that the two human sera had a reactivity pattern similar to that of D. immitis rabbit immune serum. The reaction pattern of the human sera was very different to that of Dirofilaria repens rabbit immune serum. In the light of our findings, the traditional view that subcutaneous filarial nodules are due to D. repens has to be revised.