Sensors & diagnostics最新文献

Screen printing and inkjet printing are attractive processes to produce low-cost and mass producible electroanalytical sensors. Despite important advances in the field, obtaining a printed electrochemical reference element that satisfies analytical requirements has not yet been realized satisfactorily. This paper investigates the use of screen printing and inkjet printing to produce a self-contained, all-solid state reference element that can be integrated with a wide range of electroanalytical sensing principles. The principle relies on a silver/silver iodide element that self-generates its potential by the application of a so-called pulstrode protocol. Specifically, a defined quantity of iodide is released by a short cathodic current pulse, and the reference potential defined by the released iodide is subsequently recorded at zero current. Both screen and inkjet-printed reference electrodes are fabricated and characterized, and the methodology optimized and assessed. As an application example, a single-point calibration method is used to quantify ions in undiluted filtered urine samples by potentiometry. The screen-printing approach was less successful owing to the low purity of the silver ink used. The inkjet printing approach allowed one to quantify chloride and sodium in urine. Using a conventional silver/silver chloride reference electrode as standard, relative errors of respectively 7.7 and 14.1% for chloride and sodium were obtained. While the approach would benefit from further optimization for long term applications, especially the use of high purity silver inks, it is a promising strategy for the realization of fully integrated all-solid-state microfabricated sensing systems.

A bimodal sensor, (E)-2-(4-(diphenylamino)styryl)-1-methylquinolin-1-ium (DSM), was designed and synthesized for the simultaneous fluorescence turn-on detection of Ni²⁺ ion and biomolecules such as ct-DNA, BSA, and ovalbumin. Due to its distinct size and steric properties, DSM exhibits different binding modes when interacting with Ni²⁺ and DNA/proteins. The probe DSM possesses dual functionalities, allowing it to selectively detect Ni²⁺ at one binding site while interacting with ct-DNA, BSA, and ovalbumin at another. Thus, interactions of DSM with Ni²⁺ result in fluorescence enhancement at 377 nm and 400 nm, with a detection limit of 1.53 μM and binding constant of 1.2 × 10⁶ M⁻¹. Moreover, the binding of DSM with Ni²⁺ has been demonstrated via UV-vis, mass spectra, Jobs plots and DFT analysis. Conversely, binding of DSM with ct-DNA, ovalbumin and BSA led to an increase in the fluorescence at 425 nm and 435 nm, respectively, with the detection limit at micromolar (ct-DNA) and nanomolar (BSA and ovalbumin) levels. These interactions have been validated through UV-vis spectroscopy, fluorescence studies, and molecular docking analysis. Thus, this study underscores the potential of DSM as a versatile tool for simultaneous detection of both metal ions and biomolecules with a unique bimodal approach.

Alcohol is one of the most widespread mind-affecting substances increasing the internal feeling of happiness, euphoria, conviviality and pleasance, but the improperly distilled (adulterated) beverages containing methanol pose risk to the human health. Measures for preventing the intoxication with counterfeit alcohol comprise point-of-use analysis of the alcohol via portable metal-oxide devices, liquid crystal-based detectors and spectrometric sensors with limited effectiveness due to periodic clogging of the separation column, uncertainties induced by the color of emitted light or unstable signal caused by the different optical transparencies of alcohol containers. Contemporary electronics may provide sustainable solutions to these problems by launching miniature metal–phenolic film-coated quartz crystal microbalances (MPF-QCMs) for selective detection of methanol in spirits; however, the effect of surface profile of the sorptive layer on the sensor response of these devices is unknown. We eliminate this knowledge gap by spin coating metal–phenolic films with different morphology, chemistry, wettability and thickness on the surface of six 5 MHz QCMs and subjecting them to the saturated vapor of methanol, ethanol, isopropanol, water, petroleum ether and ammonium hydroxide. The execution of over hundred experiments shows that the MPF-QCMs discriminate the chemical analytes in a repeatable and reproducible manner depending on their molecular size and acidity, and the morphochemical peculiarities of the solid surface, facilitating the registration of methanol fractions up to three orders of magnitude below the admissible concentrations in spirits. Our results provide scientific advance that has potential to address the global challenge related to the consumption of denatured alcohol.

Electroanalytical methods which can aid in the selective quantitation of saccharides such as the sialic acid N-acetyl-D-neuraminic acid (Neu5Ac) are very attractive due to their significance in a wealth of human diseases and food/nutritional products. Using cyclic voltammetry, boronic acid–diol recognition based on a redox indicator displacement assay (RIDA) strategy was exploited for non-enzymatic comparative electroanalysis of Neu5Ac vs. fructose using the redox active reporter Alizarin Red S (ARS). The concept has its foundation in the classical competition between an analyte and an indicator (ARS) for the same binding site on a host (boronic acid) molecule. The pH dependent assay employed first-time use of (thiophen-3-yl)boronic acid (TBA) as heterocyclic chemoreceptor. Electrochemistry of ARS in equilibrium with TBA resulted in proton coupled redox processes at −0.48 V (free ARS), −0.29 V (ARS–TBA boronate ester) and +0.51 V vs. Ag|AgCl (free ARS) correlating with ARS concentration in the TBA–ARS equilibrium or in competition equilibrium with a sugar species. Saccharide driven boronic acid displacement resulted in the reinstatement of the free ARS redox processes, forming the basis for the analytical signal. Voltammetry and optical investigations established the optimum conditions for Neu5Ac measurement relative to competing species such as fructose, enabling pH tunable ratiometric quantitation over the range 1–10 mM Neu5Ac (0.1 M sodium acetate buffer pH 5.6) with sensitivity 0.119 ± 0.009 μA mM⁻¹ and LOD 0.63 mM (using differential pulse voltammetry). The homogeneous studies paved the way for film formation and preliminary displacement testing when ARS was surface confined within a chitosan biopolymer layer on a glassy carbon electrode.

Multimodal optical resonators can integrate multiple sensing functions on a single device by assigning specific tasks to different modes. To facilitate such expanded functionality, this study demonstrates a photopatterning approach in which resonantly-amplified light within whispering gallery mode (WGM) sensors is used to direct chemical modification of the corresponding surface region addressed by the mode. A Ru(II) metallo–organic complex containing a caged aminopropyltriethoxysilane (APTES) moiety, [Ru(tpy)(biq)(APTES)](PF₆)₂, was synthesized and applied as a covalently immobilized layer to solid supports to be patterned, including spheroidal silica WGM resonators. Exciting a mode caused the area exposed to the light to be deprotected, leaving behind a pattern of reactive amine groups available for further derivatization. A two-photon deprotection process enabled the use of near-IR sources for patterning. The photopatterning technique was applied to self-referenced measurements, in which signals from two modes, a sensing and a reference mode, were used to detect specific binding of avidin against a much larger background of nonspecific adsorption. This was accomplished by patterning the sensing mode with biotin to specifically bind avidin while the reference mode tracked nonspecific adsorption.

This work explores label-free biosensing as an effective method for biomolecular analysis, ensuring the preservation of native conformation and biological activity. The focus is on a novel electronic biosensing platform utilizing micro-fabricated nanowell-based impedance sensors, offering rapid, point-of-care diagnosis for SARS-CoV-2 (COVID-19) detection. The nanowell sensor, constructed on a silica substrate through a series of microfabrication processes including deposition, patterning, and etching, features a 5 × 5 well array functionalized with antibodies. Real-time impedance changes within the nanowell array enable diagnostic results within ten minutes using small sample volumes (<5 μL). The research includes assays for SARS-CoV-2 spike proteins in phosphate-buffered saline (PBS) and artificial saliva buffers to mimic real human SARS-CoV-2 samples, covering a wide range of concentrations. The sensor exhibits a detection limit of 0.2 ng mL⁻¹ (1.5 pM) for spike proteins. Middle East respiratory syndrome (MERS-CoV) spike proteins are differentiated from SARS-CoV-2 spike proteins, demonstrating specificity.

In this work, we developed a small-molecule fluorescent probe (termed as LJTP3) for the specific detection of Hg²⁺ with high sensitivity in living plant tissues. LJTP3 can not only effectively indicate the spatiotemporal distribution of Hg²⁺ in the plant subcellular level, but also enable to realize 3D imaging of Hg²⁺ in plant roots.

Early and accurate detection of HIV-1 p24 antigen is crucial for timely diagnosis and treatment, particularly in resource-limited settings where traditional methods often lack the necessary sensitivity for early-stage detection or is expensive. Here, we developed a layer-by-layer signal amplification platform employing fluorescent silica nanoparticles functionalized via bioorthogonal TCO/TZ chemistry. We evaluated nanoparticles of different sizes (25, 50, and 100 nm) and two dye-doped nanoparticle formulations to optimize signal intensity, detection limits, and nonspecific binding. The 25 nm RITC-doped nanoparticles demonstrated superior performance, achieving an ultra-low detection limit of 7 fg mL⁻¹ with a broad linear range up to 1 ng mL⁻¹. Compared to FITC-doped nanoparticles, RITC-doped nanoparticles provided enhanced brightness and signal strength. Further optimization revealed that using 50 μg of 25 nm nanoparticles yielded the best sensitivity while minimizing nonspecific binding. This nanoparticle-based assay significantly outperformed commercial ELISA kits, offering a broad dynamic range and improved sensitivity. Our platform presents a highly sensitive and adaptable approach for HIV-1 p24 antigen detection, with broad potential applications in point-of-care diagnostics and detection of other low-abundance biomarkers, ultimately enhancing early disease detection and treatment accessibility.

The analysis of down-regulator of transcription 1 (DR1) offers significant information for the rapid and non-invasive diagnosis of Hashimoto's thyroiditis (HT). In this study, we report a novel dual-signal amplification electrochemical biosensor for the sensitive detection of DR1. Gold nanoparticle (AuNP)-modified molybdenum disulfide (MoS₂@AuNPs), which has extremely strong electron transfer ability and abundant binding sites, is first modified on an electrode surface as a substrate material to implement the first signal amplification. After the formation of the sandwich structure based on the specific recognition of antigens and antibodies, the electroactive molecules hyaluronic acid-based thionine (HA@Thi) are introduced to achieve the second signal amplification. Using this dual-signal amplification strategy, the proposed biosensor achieves a linear range of 1 × 10⁻⁴–1 × 10² ng mL⁻¹ with a low detection limit of 10.99 fg mL⁻¹. In addition, the electrochemical biosensor has high selectivity and good stability, and is applicable to the assay of DR1 in the presence of complex biological matrices, which is expected to provide a scientific approach for the clinical application of serum DR1 monitoring. More importantly, our method may extend the application of protein-based biosensors in disease diagnosis techniques.

Poisoning of agricultural products through the use of pesticides has created a high risk to the environment and human health. In recent years, substantial research has been devoted to replacing harmful chemical pesticides with naturally derived organic compounds and the safer detection of pernicious pesticide residues by selective and sensitive methods using suitable sensor systems has also been given equal priority. Among various sensing methods that are currently available, fluorescence-based sensing has acquired widespread acceptance and become a feasible technique for the trace analysis of pesticide residues due to several practical advantages. In this review article, we provide a systematic overview of the recent progress made in using fluorescence-based chemosensing of different classes of pesticides and their success in real-world applications. Various fluorescence chemosensors highlighted in this article are categorized based on their sensing propensity for a particular class of pesticides. In the initial section of the article, we have highlighted a detailed discussion on the classification of pesticides, and various methods available for pesticide detection, and the later sections report various chemosensors reported to date for sensing different classes of pesticides. Finally, we put forward a short discussion on the advantages and existing practical difficulties in employing fluorescent chemosensors for pesticide detection and also state the future perspective of this field toward developing practically useful sensing systems.