Search

Magnetoresistive (MR) biosensors combine distinctive features such as small size, low cost, good sensitivity, and propensity to be arrayed to perform multiplexed analysis. Magnetic nanoparticles (MNPs) are the ideal target for this platform, especially if modified not only to overcome their intrinsic tendency to aggregate and lack of stability but also to realize an interacting surface suitable for biofunctionalization without strongly losing their magnetic response. Here, we describe an MR biosensor in which commercial MNP clusters were coated with gold nanoparticles (AuNPs) and used to detect human IgG in water using an MR biochip that comprises six sensing regions, each one containing five U-shaped spin valve sensors. The isolated AuNPs (satellites) were stuck onto an aggregate of individual iron oxide crystals (core) so that the resulting core@satellite magnetic particles (CSMPs) could be functionalized by the photochemical immobilization technique an easy procedure that leads to oriented antibodies immobilized upright onto gold. The morphological, optical, hydrodynamic, magnetic, and surface charge properties of CSMPs were compared with those exhibited by the commercial MNP clusters showing that the proposed coating procedure endows the MNP clusters with stability and ductility without being detrimental to magnetic properties. Eventually, the high-performance MR biosensor allowed us to detect human IgG in water with a detection limit of 13 pM (2 ng mL-1). Given its portability, the biosensor described in this paper lends itself to a point-of-care device; moreover, the features of the MR biochip also make it suitable for multiplexed analysis.

Background: The widespread use of prostate specific antigen (PSA) caused high rate of overdiagnosis. Overdiagnosis leads to unnecessary definitive treatments of prostate cancer (PCa) with detrimental side effects, such as erectile dysfunction and incontinence. The aim of this study was to evaluate the feasibility of an artificial neural network-based approach to develop a combinatorial model including prostate health index (PHI) and multiparametric magnetic resonance (mpMRI) to recognize clinically significant PCa at initial diagnosis. Methods: To this aim we prospectively enrolled 177 PCa patients who underwent radical prostatectomy and had received PHI tests and mpMRI before surgery. We used artificial neural network to develop models that can identify aggressive PCa efficiently. The model receives as an input PHI plus PI-RADS score. Results: The output of the model is an estimate of the presence of a low or high Gleason score. After training on a dataset of 135 samples and optimization of the variables, the model achieved values of sensitivity as high as 80% and 68% specificity. Conclusions: Our preliminary study suggests that combining mpMRI and PHI may help to better estimate the risk category of PCa at initial diagnosis, allowing a personalized treatment approach. The efficiency of the method can be improved even further by training the model on larger datasets.

A novel double-resonant plasmonic substrate for fluorescence amplification in a chip-based apta-immunoassay is herein reported. The amplification mechanism relies on plasmon-enhanced fluorescence (PEF) effect. The substrate consists of an assembly of plasmon-coupled and plasmon-uncoupled gold nanoparticles (AuNPs) immobilized onto a glass slide. Plasmon-coupled AuNPs are hexagonally arranged along branch patterns whose resonance lies in the red band (∼675 nm). Plasmon-uncoupled AuNPs are sprinkled onto the substrate, and they exhibit a narrow resonance at 524 nm. Numerical simulations of the plasmonic response of the substrate through the finite-difference time-domain (FDTD) method reveal the presence of electromagnetic hot spots mainly confined in the interparticle junctions. In order to realize a PEF-based device for potential multiplexing applications, the plasmon resonances are coupled with the emission peak of 5-carboxyfluorescein (5-FAM) fluorophore and with the excitation/emission peaks of cyanine 5 (Cy5). The substrate is implemented in a malaria apta-immunoassay to detect Plasmodium falciparum lactate dehydrogenase (PfLDH) in human whole blood. Antibodies against Plasmodium biomarkers constitute the capture layer, whereas fluorescently labeled aptamers recognizing PfLDH are adopted as the top layer. The fluorescence emitted by 5-FAM and Cy5 fluorophores are linearly correlated (logarithm scale) to the PfLDH concentration over five decades. The limits of detection are 50 pM (1.6 ng/mL) with the 5-FAM probe and 260 fM (8.6 pg./mL) with the Cy5 probe. No sample preconcentration and complex pretreatments are required. Average fluorescence amplifications of 160 and 4500 are measured in the 5-FAM and Cy5 channel, respectively. These results are reasonably consistent with those worked out by FDTD simulations. The implementation of the proposed approach in multiwell-plate-based bioassays would lead to either signal redundancy (two dyes for a single analyte) or to a simultaneous detection of two analytes by different dyes, the latter being a key step toward high-throughput analysis.

Glyphosate is the most widely used herbicide in the world and, in view of its toxicity, there is a quest for easy-to-use, but reliable methods to detect it in water. To address this issue, we realized a simple, rapid, and highly sensitive immunosensor based on gold coated magnetic nanoparticles (MNPs@Au) to detect glyphosate in tap water. Not only the gold shell provided a sensitive optical transduction of the biological signal – through the shift of the local surface plasmon resonance (LSPR) entailed by the nanoparticle aggregation –, but it also allowed us to use an effective photochemical immobilization technique to tether oriented antibodies straight on the nanoparticles surface. While such a feature led to aggregates in which the nanoparticles were at close proximity each other, the magnetic properties of the core offered us an efficient tool to steer the nanoparticles by a rotating magnetic field. As a result, the nanoparticle aggregation in presence of the target could take place at higher rate (enhanced diffusion) with significant improvement in sensitivity. As a matter of fact, the combination of plasmonic and magnetic properties within the same nanoparticles allowed us to realize a colorimetric biosensor with a limit of detection (LOD) of 20 ng∙L−1.

Two-dimensional materials have unique properties and their better functionality has created new paradigms in the field of sensing. Over the past decade, a new family of 2D materials known as MXenes has emerged as a promising material for numerous applications, including biosensing. Their metallic conductivity, rich surface chemistry, hydrophilicity, good biocompatibility, and high anchoring capacity for biomaterials make them an attractive candidate to detect a variety of analytes. Despite such notable properties, there are certain limitations associated with them. This review aims to present a detailed survey of MXene's synthesis; in particular, their superiority in the field of biosensing as compared to other 2D materials is addressed. Their low oxidative stability is still an open challenge, and recent investigations on MXene's oxidation are summarized. The hexagonal stacking network of MXenes acts as a distinctive matrix to load nanoparticles, and the embedded nanoparticles can bind an excess number of biomolecules (e.g., antibodies) thereby improving biosensor performance. We will also discuss the synthesis and corresponding performance of MXenes nanocomposites with noble metal nanoparticles and magnetic nanoparticles. Furthermore, Nb and Ti2C-based MXenes, and Ti3C2-MXene sandwich immunoassays are also reviewed in view of their importance. Different aspects and challenges associated with MXenes (from their synthesis to final applications) and the future perspectives described give new directions to fabricate novel biosensors.

Background: The Prostate Health Index (PHI) and Proclarix (PCLX) have been proposed as blood-based tests for prostate cancer (PCa). In this study, we evaluated the feasibility of an artificial neural network (ANN)-based approach to develop a combinatorial model including PHI and PCLX biomarkers to recognize clinically significant PCa (csPCa) at initial diagnosis. Methods: To this aim, we prospectively enrolled 344 men from two different centres. All patients underwent radical prostatectomy (RP). All men had a prostate-specific antigen (PSA) between 2 and 10 ng/mL. We used an artificial neural network to develop models that can identify csPCa efficiently. As inputs, the model uses [-2]proPSA, freePSA, total PSA, cathepsin D, thrombospondin, and age. Results: The output of the model is an estimate of the presence of a low or high Gleason score PCa defined at RP. After training on a dataset of up to 220 samples and optimization of the variables, the model achieved values as high as 78% for sensitivity and 62% for specificity for all-cancer detection compared with those of PHI and PCLX alone. For csPCa detection, the model showed 66% (95% CI 66–68%) for sensitivity and 68% (95% CI 66–68%) for specificity. These values were significantly different compared with those of PHI (p < 0.0001 and 0.0001, respectively) and PCLX (p = 0.0003 and 0.0006, respectively) alone. Conclusions: Our preliminary study suggests that combining PHI and PCLX biomarkers may help to estimate, with higher accuracy, the presence of csPCa at initial diagnosis, allowing a personalized treatment approach. Further studies training the model on larger datasets are strongly encouraged to support the efficiency of this approach.

Xanthomonas campestris pv. campestris is known as the causative agent of black rot disease, which attacks mainly crucifers, severely lowering their global productivity. One of the main virulence factors of this pathogen is its capability to penetrate and form biofilm structures in the xylem vessels. The discovery of novel approaches to crop disease management is urgent and a possible treatment could be aimed at the eradication of biofilm, although anti-biofilm approaches in agricultural microbiology are still rare. Considering the multifactorial nature of biofilm, an effective approach against Xanthomonas campestris implies the use of a multi-targeted or combinatorial strategy. In this paper, an anti-biofilm strategy based on the use of fatty acids and the bacteriophage (Xcc&phi, 1)-hydroxyapatite complex was optimized against Xanthomonas campestris mature biofilm. The synergic action of these elements was demonstrated and the efficient removal of Xanthomonas campestris mature biofilm was also proven in a flow cell system, making the proposed approach an effective solution to enhance plant survival in Xanthomonas campestris infections. Moreover, the molecular mechanisms responsible for the efficacy of the proposed treatment were explored.

Classically, the need for highly sophisticated instruments with important economic costs has been a major limiting factor for clinical pathology laboratories, especially in developing countries. With the aim of making clinical pathology more accessible, a wide variety of free or economical technologies have been developed worldwide in the last few years. 3D printing and Arduino approaches can provide up to 94% economical savings in hardware and instrumentation in comparison to commercial alternatives. The vast selection of point-of-care-tests (POCT) currently available also limits the need for specific instruments or personnel, as they can be used almost anywhere and by anyone. Lastly, there are dozens of free and libre digital tools available in health informatics. This review provides an overview of the state-of-the-art on cost-effective alternatives with applications in routine clinical pathology laboratories. In this context, a variety of technologies including 3D printing and Arduino, lateral flow assays, plasmonic biosensors, and microfluidics, as well as laboratory information systems, are discussed. This review aims to serve as an introduction to different technologies that can make clinical pathology more accessible and, therefore, contribute to achieve universal health coverage.

The green synthesis of highly conductive polyaniline by using two biological macromolecules, i.e laccase as biocatalyst, and DNA as template/dopant, was achieved in this work. Trametes versicolor laccase B (TvB) was found effective in oxidizing both aniline and its less toxic/mutagenic dimer N-phenyl-p-phenylenediamine (DANI) to conductive polyaniline. Reaction conditions for synthesis of conductive polyanilines were set-up, and structural and electrochemical properties of the two polymers were extensively investigated. When the less toxic aniline dimer was used as substrate, the polymerization reaction was faster and gave less-branched polymer. DNA was proven to work as hard template for both enzymatically synthesized polymers, conferring them a semi-ordered morphology. Moreover, DNA also acts as dopant leading to polymers with extraordinary conductive properties (∼6 S/cm). It can be envisaged that polymer properties are magnified by the concomitant action of DNA as template and dopant. Herein, the developed combination of laccase and DNA represents a breakthrough in the green synthesis of conductive materials.

Biosensors are easy-to-use and cost-effective devices that are emerging as an attractive tool, not only in settling diagnosis or in disease monitoring, but also in mass screening tests, a timely topic that impacts on daily life of the whole society. Nanotechnologies lend themselves to the development of highly sensitive devices whose realization has become a very interdisciplinary topic. Relying on the enhancement of the fluorescence signal detected at the surface of patterned gold nanoparticles, we report the behavior of an analytical device in detecting immunoglobulins in real urine samples that shows a limit of detection of approximately 8 μg/L and a linear range of 10-100 μg/L well below the detection limit of nephelometric method, which is the reference method for this analysis. These performances have been reached thanks to an effective surface functionalization technique and can be improved even more if superydrophobic features of the substrate we produce will be exploited. Since the analyte recognition is realized by antibodies the specificity is very high and, in fact, no interference has been detected by other compounds also present in the real urine samples. The device has been assessed on serum samples by comparing IgG concentrations values obtained by the biosensor with those provided by a nephelometer. In this step we found that our approach allows the analysis of the whole blood without any pretreatment; moreover, it is inherently extendable to the analysis of most biochemical markers in biological fluids.

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 immunoassays. Graphical abstract

Background: medical device-induced infections affect millions of lives worldwide and innovative preventive strategies are urgently required. Antimicrobial peptides (AMPs) appear as ideal candidates to efficiently functionalize medical devices surfaces and prevent bacterial infections. In this scenario, here, we produced antimicrobial polydimethylsiloxane (PDMS) by loading this polymer with an antimicrobial peptide identified in human apolipoprotein B, r(P)ApoBLPro. Methods: once obtained loaded PDMS, its structure, anti-infective properties, ability to release the peptide, stability, and biocompatibility were evaluated by FTIR spectroscopy, water contact angle measurements, broth microdilution method, time-killing kinetic assays, quartz crystal microbalance analyses, MTT assays, and scanning electron microscopy analyses. Results: PDMS was loaded with r(P)ApoBLPro peptide which was found to be present not only in the bulk matrix of the polymer but also on its surface. ApoB-derived peptide was found to retain its antimicrobial properties once loaded into PDMS and the antimicrobial material was found to be stable upon storage at 4 °C for a prolonged time interval. A gradual and significant release (70% of the total amount) of the peptide from PDMS was also demonstrated upon 400 min incubation and the antimicrobial material was found to be endowed with anti-adhesive properties and with the ability to prevent biofilm attachment. Furthermore, PDMS loaded with r(P)ApoBLPro peptide was found not to affect the viability of eukaryotic cells. Conclusions: an easy procedure to functionalize PDMS with r(P)ApoBLPro peptide has been here developed and the obtained functionalized material has been found to be stable, antimicrobial, and biocompatible.

The development of non-toxic fluorescent agents alternative to heavy metal-based semiconductor quantum dots represents a relevant topic in biomedical research and in particular in the bioimaging field. Herein, highly luminescent Si-H terminal microporous silicon nanoparticles with mu s-lived photoemission are chemically modified with a two step process and successfully used as label-free probes for in vivo time-gated luminescence imaging. In this context,Hydra vulgarisis used as model organism for in vivo study and validity assessment. The application of time gating allows to pursue an effective sorting of the signals, getting rid of the most common sources of noise that are fast-decay tissue autofluorescence and excitation scattering within the tissue. Indeed, an enhancement by a factor similar to 20 in the image signal-to-noise ratio can be estimated.

Mass testing is fundamental to face the pandemic caused by the coronavirus SARS-CoV-2 discovered at the end of 2019. To this aim, it is necessary to establish reliable, fast and cheap tools to detect viral particles in biological material so to identify the people capable to spread the infection. We demonstrate that a colorimetric biosensor based on gold nanoparticle (AuNP) interaction induced by SARS-CoV-2 lends itself as an outstanding tool for detecting viral particles in nasal and throat swabs. The extinction spectrum of a colloidal solution of multiple viral-target gold nanoparticles – AuNPs functionalized with antibodies targeting three surface proteins of SARS-CoV-2 (spike, envelope and membrane) – is redshifted in few minutes when mixed to a solution containing the viral particle. The optical density of the mixed solution measured at 560 nm was compared to the threshold cycle (Ct) of a Real Time-PCR (gold standard for detecting the presence of viruses) finding that the colorimetric method is able to detect very low viral load with a detection limit approaching that of RT-PCR. Since the method is sensitive to the infecting viral particle rather than to its RNA, the achievements reported here open new perspective not only in the context of the current and possible future pandemics, but also in microbiology as the biosensor proves itself to be a powerful though simple tool for measuring the viral particle concentration.

The development of a simple and low cost electrochemical impedance immunosensor based on screen printed gold electrode for rapid detection of Escherichia coli in water is reported. The immunosensor is fabricated by immobilizing anti-E. coli antibodies onto a gold surface in a covalent way by the photochemical immobilization technique, a simple procedure able to bind antibodies upright onto gold surfaces. Impedance spectra are recorded in 0.01 M phosphate buffer solution (PBS) containing 10 mM Fe(CN)63&minus, /Fe(CN)64&minus, as redox probe. The Nyquist plots can be modelled with a modified Randles circuit, identifying the charge transfer resistance Rct as the relevant parameter after the immobilization of antibodies, the blocking with BSA and the binding of E. coli. The introduction of a standard amplification procedure leads to a significant enhancement of the impedance increase, which allows one to measure E. coli in drinking water with a limit of detection of 3 &times, 101 CFU mL&minus, 1 while preserving the rapidity of the method that requires only 1 h to provide a &ldquo, yes/no&rdquo, response. Additionally, by applying the Langmuir adsorption model, we are able to describe the change of Rct in terms of the &ldquo, effective&rdquo, electrode, which is modified by the detection of the analyte whose microscopic conducting properties can be quantified.

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.

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.

A colorimetric immunosensor based on local surface plasmon resonance by gold nanoparticles is presented, and its application for the detection of human immunoglobulin G (IgG) is demonstrated. The color change of the colloidal solution is produced by nanoparticle aggregation, a process that can be tuned by the presence of the analyte once the nanoparticles are functionalized. In comparison to common functionalization techniques, the procedure described here is simpler, low-cost, and effective in binding antibodies upright on the gold surface. The dose–response curve is similar to that resulting in typical immunoassay platforms and is satisfactorily described by the proposed theoretical model. Human IgG at concentration levels of few hundreds of nanograms per milliliter can be detected by eyes within a few minutes, thereby making the colorimetric immunosensor proposed here a powerful tool in several areas, with urine test in medical diagnostics being the most immediate.

Conventional laboratory techniques exhibit impressive sensing performance and still constitute an irreplaceable tool in bioanalytics. Nevertheless, high costs, time consumption, and need for well-equipped laboratories and skilled personnel make highly desirable to explore novel strategies to carry out biochemical analyses. In this regard, biosensor-based methods represent a promising approach to keep affordability and rapidity, thus they can inherently pave the way to point of care tests and high-throughput analysis. Regrettably, most of them suffer from fabrication and biofunctionalization complexity, and poor sensitivities and reliability. Therefore, their adoption as a real alternative to the gold standards is still far from being achieved. However, the massive research on plasmonic nanostructures is revealing their potentialities in sensing field, since they own appealing performances resulting from the plasmon-related effects and can be easily adapted to a large variety of applications. In this review, a summary of plasmonic biosensors recently devised is reported. Though many nanostructures fit for shared applications, for clarity they are classified into two main categories: i) biosensors whose sensing parameters are plasmon-related observables (localized, coupled, lattice surface plasmon resonances) and ii) biosensors in which the nanostructure acts as amplifier for an external signal (surface-enhanced Raman and infrared spectroscopies and plasmon-enhanced fluorescence).

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.

The green synthesis of highly conductive polyaniline by using two biological macromolecules, i.e laccase as biocatalyst, and DNA as template/dopant, was achieved in this work. Trametes versicolor laccase B (TvB) was found effective in oxidizing both aniline and its less toxic/mutagenic dimer N‐phenyl‐p‐phenylenediamine (DANI) to conductive polyaniline. Reaction conditions for synthesis of conductive polyanilines were set‐up, and structural and electrochemical properties of the two polymers were extensively investigated. When the less toxic aniline dimer was used as substrate, the polymerization reaction was faster and gave less‐branched polymer. DNA was proven to work as hard template for both enzymatically synthesized polymers, conferring them a semi‐ordered morphology. Moreover, DNA also acts as dopant leading to polymers with extraordinary conductive properties (∼6 S/cm). It can be envisaged that polymer properties are magnified by the concomitant action of DNA as template and dopant. Herein, the developed combination of laccase and DNA represents a breakthrough in the green synthesis of conductive materials.

Purpose The use of bacteriophages represents a valid alternative to conventional antimicrobial treatments, overcoming the widespread bacterial antibiotic resistance phenomenon. In this work, we evaluated whether biomimetic hydroxyapatite (HA) nanocrystals are able to enhance some properties of bacteriophages. The final goal of this study was to demonstrate that biomimetic HA nanocrystals can be used for bacteriophage delivery in the context of bacterial infections, and contribute – at the same time – to enhance some of the biological properties of the same bacteriophages such as stability, preservation, antimicrobial activity, and so on. Materials and methods Phage isolation and characterization were carried out by using Mitomycin C and following double-layer agar technique. The biomimetic HA water suspension was synthesized in order to obtain nanocrystals with plate-like morphology and nanometric dimensions. The interaction of phages with the HA was investigated by dynamic light scattering and Zeta potential analyses. The cytotoxicity and intracellular killing activities of the phage–HA complex were evaluated in human hepatocellular carcinoma HepG2 cells. The bacterial inhibition capacity of the complex was assessed on chicken minced meat samples infected with Salmonella Rissen. Results Our data highlighted that the biomimetic HA nanocrystal–bacteriophage complex was more stable and more effective than phages alone in all tested experimental conditions. Conclusion Our results evidenced the important contribution of biomimetic HA nanocrystals: they act as an excellent carrier for bacteriophage delivery and enhance its biological characteristics. This study confirmed the significant role of the mineral HA when it is complexed with biological entities like bacteriophages, as it has been shown for molecules such as lactoferrin.

Surface functionalization is a key step in biosensing since it is the basis of an effective analyte recognition. Among all the bioreceptors, antibodies (Abs) play a key role thanks to their superior specificity, although the available immobilization strategies suffer from several drawbacks. When gold is the interacting surface, the recently introduced Photochemical Immobilization Technique (PIT) has been shown to be a quick, easy-to-use and very effective method to tether Abs oriented upright by means of thiols produced via tryptophan mediated disulphide bridge reduction. Although the molecular mechanism of this process is quite well identified, the detailed morphology of the immobilized antibodies is still elusive due to inherent difficulties related to the microscopy imaging of Abs. The combination of Mass Spectrometry, Surface-Enhanced Raman Spectroscopy and Ellman's assay demonstrates that Abs irradiated under the conditions in which PIT is realized show only two effective disulphide bridges available for binding. They are located in the constant region of the immunoglobulin light chain so that the most likely position Ab assumes is side-on, i.e. with one Fab (i.e. the antigen binding portion of the antibody) exposed to the solution. This is not a limitation of the recognition efficiency in view of the intrinsic flexibility of the Ab structure, which makes the free Fab able to sway in the solution, a feature of great importance in many biosensing applications.

Surface functionalization is a key step in biosensing and antibodies (Abs) occupy a key role in bio-recognition thanks to their superior specificity. When gold is the interacting surface, the recently introduced Photochemical Immobilization Technique (PIT) has shown to be quick, easy-to-use and very effective in tethering Abs oriented upright. The molecular base of PIT relies on the selective photo-reduction of the disulphide bridges in cys-cys/trp triads in IgGs, which in turn leads to the production of reduced SH groups with strong affinity towards noble metals. The selectivity of PIT arises from the presence of only 12 triads not all of them effective in yielding thiols. We demonstrate that by irradiating Abs in solution for only 30 s with UV light from an amalgam type lamp, the Abs are "activated" and approximately 7 thiols are produced. Once opened, SHs keep their properties for at least 200 s, a time long enough to convey Abs onto a gold surface on which they bind upright. The position of SH has been determined by mass spectrometry, which also confirms that only 8 thiols per Ab are reduced by UV and 4 of them (i.e. 2 disulphide bridges) are not exposed to the solvent lowering to two the number of bridges available for PIT. Moreover, SERS highlights that the signal from UV-treated Abs is much stronger than that coming from Abs physisorbed, thereby demonstrating higher proximity of Abs with the surface when they are UV-activated.

Water monitoring technologies are widely used for contaminant detection in a wide variety of water ecology applications such as water treatment plants and water distribution systems. A tremendous amount of research has been conducted over the past decades to develop robust and efficient techniques of contaminant detection with minimum operating cost and energy. Recent developments in spectroscopic techniques and biosensor approach have improved the detection sensitivities, quantitatively and qualitatively. The availability of in-situ measurements and multiple detection analyses has expanded water monitoring applications in various advanced techniques including successful development in hand-held sensing devices, which improves portability in real-time basis for the detection of contaminants, such as microorganisms, pesticides, heavy metal ions, and inorganic and organic components.

After skin cancer, prostate cancer (PC) is the most common cancer among men. The gold standard for PC diagnosis is based on the PSA (prostate-specific antigen) test. Based on this preliminary screening, the physician decides whether to proceed with further tests, typically prostate biopsy, to confirm cancer and evaluate its aggressiveness. Nevertheless, the specificity of the PSA test is suboptimal and, as a result, about 75% of men who undergo a prostate biopsy do not have cancer even if they have elevated PSA levels. Overdiagnosis leads to unnecessary overtreatment of prostate cancer with undesirable side effects, such as incontinence, erectile dysfunction, infections, and pain. Here, we used artificial neuronal networks to develop models that can diagnose PC efficiently. The model receives as an input a panel of 4 clinical variables (total PSA, free PSA, p2PSA, and PSA density) plus age. The output of the model is an estimate of the Gleason score of the patient. After training on a dataset of 190 samples and optimization of the variables, the model achieved values of sensitivity as high as 86% and 89% specificity. The efficiency of the method can be improved even further by training the model on larger datasets.

Interactions between biomolecules and between substrates and biomolecules is a crucial issue in physics and applications to topics such as biotechnology and organic electronics. The efficiency of bio- and mechanical sensors, of organic electronics systems, and of a number of other devices critically depends on how molecules are deposited on a surface so that these acquire specific functions. Here, we tackle this vast problem by developing a coarse grained model of biomolecules having a recognition function, such as antibodies, capable to quantitatively describe in a simple manner essential phenomena: antigen-antibody and antibody substrate interactions. The model is experimentally tested to reproduce the results of a benchmark case, such as (1) gold surface functionalization with antibodies and (2) antibody-antigen immune-recognition function. The agreement between experiments and model prediction is excellent, thus unveiling the mechanism for antibody immobilization onto metals at the nanoscale in various functionalization schemes. These results shed light on the geometrical packing properties of the deposited molecules, and may open the way to a novel coarse-grained based approach to describe other processes where molecular packing is a key issue with applications in a huge number of fields from nano- to biosciences.

The discovery of 2D conductivity at the LaAlO3/SrTiO3 interface has been linking, for over a decade, two of the major current research fields in materials science: correlated transition-metal-oxide systems and low-dimensional systems. Notably, despite the 2D nature of the interfacial electron gas, the samples are 3D objects with thickness in the mm range. This prevented researchers so far from adopting strategies that are only viable for fully 2D materials, or from effectively exploiting degrees of freedom related to strain, strain gradient and curvature. Here a method based on pure strain engineering for obtaining freestanding LaAlO3/SrTiO3 membranes with micrometer lateral dimensions is demonstrated. Detailed transmission electron microscopy investigations show that the membranes are fully epitaxial and that their curvature results in a huge strain gradient, each layer showing a mixed compressive/tensile strain state. Electronic devices are fabricated by realizing ad hoc circuits for individual micro-membranes transferred on silicon chips. The samples exhibit metallic conductivity and electrostatic field effect like 2D-electron systems in bulk heterostructures. The results open a new path for adding oxide functionalities into semiconductor electronics, potentially allowing for ultra-low voltage gating of a superconducting transistors, micromechanical control of the 2D electron gas mediated by ferroelectricity and flexoelectricity, and on-chip straintronics.

Salmonella Typhimurium is one of the main causes of outbreaks and sporadic cases of human gastroenteritis. At present, the rapid detection of this pathogen is a major goal of biosensing technology applied to food safety. In fact, ISO standardized culture method takes up to ten days to provide a reliable response. In this paper, we describe a relatively simple protocol for detecting Salmonella Typhimurium in chicken meat based on a Quartz-Crystal Microbalance (QCM), which leads to a limit of detection (LOD) less than of 10° CFU/mL and requires a pre-enrichment step lasting only 2 h at 37 °C. The reliability of the proposed immunosensor has been demonstrated through the validation of the experimental results with ISO standardized culture method. The cost-effectiveness of the procedure and the rapidity of the QCM-based biosensor in providing the qualitative response make the analytical method described here suitable for applications in food inspection laboratory and throughout the chain production of food industry.

The study of molecules that self-assemble through noncovalent interactions is one of the most attractive topics in supramolecular chemistry. The use of short peptides or modified nucleotides as building blocks for the aggregates is particularly intriguing because these are very easy to synthesize; moreover, subtle changes in the chemical structure of such building blocks may drastically affect the properties of the aggregates. The ability of peptide nucleic acids (PNA) to aggregate has been very little explored, despite its practical applications. In this work we investigated the self-assembling properties of a PNA dimer, conjugated at the N-terminus to a fluorenylmethoxycarbonyl group. This PNA dimer forms nano-aggregates at low concentration in CHCl3 /CH3 OH mixtures. The aggregates retain very interesting fluorescent properties (high quantum yield in the visible region with lifetimes on the nanosecond scale), which make them promising materials for applications in optoelectronics.