Analysis of the optical response of a SARS-CoV-2-directed colorimetric immunosensor

The optical response of different configurations of functionalized gold nanoparticles (f-AuNPs) and SARS-CoV-2 virions is simulated in order to explore the behavior of a colloidal solution containing 105–1013 virions/ml. The analysis herein reported is carried out for three concentration regimes: (i) low (≲108 virions/ml), (ii) intermediate (∼109–1010 virions/ml), and (iii) high (≳1011 virions/ml). Given the high binding effectiveness of f-AuNPs to virions, three different configurations are expected to arise: (i) virions completely surrounded by f-AuNPs, (ii) aggregates (dimers or trimers) of virions linked by f-AuNPs, and (iii) single f-AuNP surrounded by virions. It is demonstrated that 20 nm diameter gold nanoparticles functionalized against all three kinds of SARS-CoV-2 proteins (membrane, envelope, and spike) allow one to reach a limit of detection (LOD) of ∼106 virions/ml, whereas the use of only one kind of f-AuNP entails a ten-fold worsening of the LOD. It is also shown that the close proximity (∼5 nm) of the f-AuNP to the virions assumed throughout this analysis is essential to avoid the hook effect, thereby pointing out the importance of realizing an apt functionalization procedure that keeps thin the dielectric layer (e.g., proteins or aptamers) surrounding the gold nanoparticles

High Growth Rate of Benign Thyroid Nodules Bearing RET/PTC Rearrangements

Context: Benign thyroid nodules display a broad range of behaviors from a stationary size to a progressive growth. The RET/PTC oncogene has been documented in a fraction of benign thyroid nodules, besides papillary thyroid carcinomas, and it might therefore influence their growth. Objective: The aim of the present work was to evaluate whether RET/PTC in benign thyroid nodules associates with a different nodular growth rate. Study Design: In this prospective multicentric study, 125 subjects with benign nodules were included. RET rearrangements were analyzed in cytology samples; clinical and ultrasonographic nodule characteristics were assessed at the start and at the end of the study. Results: RET/PTC was present in 19 nodules. The difference between the mean baseline nodular volume of the RET/PTC− and RET/PTC+ nodules was not significant. After 36 months of follow-up, the RET/PTC+ group (n = 16) reached a volume higher than the RET/PTC− group (n = 90) (5.04 ± 2.67 vs. 3.04 ± 2.26 ml; P = 0.0028). We calculated the monthly change of nodule volumes as a percentage of baseline. After a mean follow-up of 36.6 months, the monthly volume increase of nodules bearing a RET rearrangement was 4.3-fold that of nodules with wild-type RET (1.83 ± 1.2 vs. 0.43 ± 1.0% of baseline volume; P < 0.0001). Conclusions: Benign thyroid nodules bearing RET rearrangements grow more rapidly than those with wild-type RET. Searching for RET rearrangements in benign thyroid nodules might be useful to the clinician in choosing the more appropriate and timely therapeutic option

Gold decorated magnetic nanoparticles for biosensing

The aim of the work in this thesis was to propose novel effective protocols for gold coating of commercial MNPs to improve the applicability of biosensors in environmental control, food safety and clinical analysis. Three different types of gold decorated magnetic nanoparticles were designed and tested in combination with as many types of biosensors. The introduction of MNPs@Au was aimed at improving the performance of already widespread biosensing setups, narrowing the gap in terms of sensitivity and applicability with gold standard techniques. This thesis work has been organized to provide the reader with the basic theoretical and experimental notions before delving into the innovative content. To this end, Chapter 1 briefly introduces biosensors focusing on the types of transducers exploited in the following part of the work. Then, in the context of functionalization techniques, the main advantages of Photochemical Immobilization Technique (PIT) over conventional methods are listed. In the final part of the Chapter, nanoparticles are introduced, focusing on AuNPs and MNPs@Au. In Chapter 2 is presented a magnetoelastic (ME) biosensor for wireless detection of analytes in liquid. A new amplification protocol exploiting MNPs@Au is demonstrated to significantly enhance the sensitivity. The superiority of MNPs@Au over AuNPs, has been demonstrated by testing the ME biosensor against Human IgG in the range 0–20 μg∙mL−1. The experimental results show that the ME biosensor works well in water and has a rapid response time, being promising for real-time wireless detection of pathogens in liquids and for real life diagnostic purposes. In Chapter 3 a simple, easy-to-use and efficient colorimetric immunosensor that exploits spinning MNPs@Au in a rotating magnetic field is presented. The proposed biosensor was tested against glyphosate in tap water, being able to detect the pesticide in concentration lower than the ones legally permitted in food according to several authorities. The excellent result in terms of sensitivity was achieved thanks to the adoption of MNPs@Au, as shown by the comparison made with the AuNPs based biosensor. This performance makes the colorimetric approach described in Chapter 3 an interesting tool for on-site detection or even POC diagnosis. In Chapter 4 is reported a fast, simple and effective protocol for coating commercial MNP clusters with AuNPs. The resulting core@satellite magnetic particles (CSMPs) consist of isolated gold nanoparticles stuck onto an aggregate of individual iron oxide crystals (core). The CSMPs were used in combination with a powerful MR biochip equipped with a unique highly-portable detection platform properly designed to achieve a POC device. The biosensing setup was tested against Human IgG at concentrations of clinical interest. The novel CSMPs have an enormous potential for excellent sensing applications, especially in the target protein quantitative detection field with quick response (within 1 hour), potential multiplexing analysis (up to 6 different analytes at the same time) and signal redundancy (up to 30 measurements). The global conclusions of the thesis work are summarized in the final remarks

Update on anesthesia and the immune response in newborns delivered by cesarian section

In infants delivered by cesarian section, the immune system could be influenced by anesthetic drugs that may cross the placenta and reach the fetal circulation. Factors that determine placental transfer of anesthetics and their distribution into and ultimate removal from fetal tissue include physiochemical properties of the compound; the anatomic features of the maternal circulation, placenta, and fetus; and the hemodynamic and pharmacokinetic events that occur within them. Because the anesthetic agents can interfere with many neonatal function, the aim of this manuscript is to review the interference of regional or general anesthesia on neonatal immune respons

Randomly positioned gold nanoparticles as fluorescence enhancers in apta-immunosensor for malaria test

A plasmon-enhanced fluorescence-based antibody-aptamer biosensor — consisting of gold nanoparticles randomly immobilized onto a glass substrate via electrostatic self-assembly — is described for specific detection of proteins in whole blood. Analyte recognition is realized through a sandwich scheme with a capture bioreceptor layer of antibodies — covalently immobilized onto the gold nanoparticle surface in upright orientation and close-packed configuration by photochemical immobilization technique (PIT) — and a top bioreceptor layer of fluorescently labelled aptamers. Such a sandwich configuration warrants not only extremely high specificity, but also an ideal fluorophore-nanostructure distance (approximately 10–15 nm) for achieving strong fluorescence amplification. For a specific application, we tested the biosensor performance in a case study for the detection of malaria-related marker Plasmodium falciparum lactate dehydrogenase (PfLDH). The proposed biosensor can specifically detect PfLDH in spiked whole blood down to 10 pM (0.3 ng/mL) without any sample pretreatment. The combination of simple and scalable fabrication, potentially high-throughput analysis, and excellent sensing performance provides a new approach to biosensing with significant advantages compared to conventional fluorescence immunoassay

LSPR-based colorimetric immunosensor for rapid and sensitive 17β-estradiol detection in tap water

We propose a highly sensitive immunosensor based on the Localized Surface Plasmon Resonance (LSPR) for 17β-estradiol (E2) quantification in water. E2 molecules are recognized by polyclonal antibodies immobilized onto gold nanoparticles (AuNPs) and act as linkers that cause nanoparticles aggregation. This leads to the change in the optical properties of the solution visible even by naked eyes. The aggregates were characterized by Dynamic Light Scattering (DLS) and Scanning Transmission Electron Microscopy (STEM) that provided an accurate assessment of the inter-particle distance. The finite-difference time-domain (FDTD) method applied to a Mie problem like workspace allowed us to describe the optical behaviour of the AuNP aggregates with excellent agreement between the experimental and numerical results. The limit of detection (LOD), without any preconcentration step, is 3 pg/mL (11 pM), whereas the detection range extends over five decades up to 105 pg/mL. The proposed E2 immunosensor was tested in tap water, where no significant cross-reaction signal was detected by similar molecules (testosterone, progesterone, estrone and estriol). The device described here represents a significant improvement of low E2 levels determination in terms of affordability, time and measuring simplicity, making it suitable for environmental applications