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A magnetoelastic (ME) biosensor for wireless detection of analytes in liquid is described. The ME biosensor was tested against human IgG in the range 0&ndash, 20 &mu, g∙mL&minus, 1. The sensing elements, anti-human IgG produced in goat, were immobilized on the surface of the sensor by using a recently introduced photochemical immobilization technique (PIT), whereas a new amplification protocol exploiting gold coated magnetic nanoparticles (core-shell nanoparticles) is demonstrated to significantly enhance the sensitivity. The gold nanoflowers grown on the magnetic core allowed us to tether anti-human IgG to the nanoparticles to exploit the sandwich detection scheme. The experimental results show that the 6 mm &times, 1 mm &times, 30 &mu, m ME biosensor with an amplification protocol that uses magnetic nanoparticles has a limit of detection (LOD) lower than 1 nM, works well in water, and has a rapid response time of few minutes. Therefore, the ME biosensor is very promising for real-time wireless detection of pathogens in liquids and for real life diagnostic purpose.

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.

Complex architectural rearrangements are associated to the control of the HoxD genes in different cell types; yet, how they are implemented in single cells remains unknown. By use of polymer models, we dissect the locus 3D structure at the single DNA molecule level in mouse embryonic stem and cortical neuronal cells, as the HoxD cluster changes from a poised to a silent state. Our model describes published Hi-C, 3-way 4C, and FISH data with high accuracy and is validated against independent 4C data on the Nsi-SB 0.5-Mb duplication and on triple contacts. It reveals the mode of action of compartmentalization on the regulation of the HoxD genes that have gene- and cell-type-specific multi-way interactions with their regulatory elements and high cell-to-cell variability. It shows that TADs and higher-order 3D structures, such as metaTADs, associate with distinct combinations of epigenetic factors, including but not limited to CCCTC-binding factor (CTCF) and histone marks. Bianco et al. reconstruct the 3D structure of the murine HoxD locus by using polymer models at the single DNA molecule level. The locus architecture rearranges upon differentiation from embryonic stem cells to cortical neurons in connection to epigenetic changes, as cell-type- and gene-specific multi-way contacts are established with regulatory elements.