Exosomes are a subpopulation of nanosized extracellular vesicles (EVs), formed by a lipid bilayer and naturally secreted by cells. They transport RNA, microRNAs, bioactive proteins, and lipids and play an important role in intercellular communication. Exosomes are a promising alternative cell-free therapy in regenerative medicine, immunotherapy, and drug delivery. The implementation of new exosomes treatments requires knowledge of its concentration, purity, and full characterization. However, comparing different studies is highly challenging due to the lack of validated methodologies for isolation and determination, as well as a lack of well-characterized exosomes reference standards. In this work, human uterine cervical mesenchymal stem cell (hUCESC) EVs have been isolated by ultracentrifugation and characterized, discussing the current limitations of characterization methods. First, total protein assays are heavily influenced by free-protein and lipid contaminations which confirm the need of employing several methods for vesicular protein determination. This purity variation seems heavily influenced by the vesicles origin as more complex mediums originate more matrix interferences. Size exclusion high performance liquid chromatography has been demonstrated as a new methodology for purity assessment of hUCESC-EVs and commercial EVs (adipose stem cells and human serum). The results found low purity in the commercial exosomes highlighting that protein and lipid purity must be included in the commercial EVs. Finally, the combination of this chromatography method with total protein assays proved that particle concentration could be estimated using vesicular protein concentration.Graphical abstract

A novel impedimetric magneto-immunosensor based on iron oxide (Fe3O4) nanoparticles coated with 3-phosphonopropionic acid (3-PPA) (functionalized magnetic beads, or FMBs) was created for the highly sensitive and selective detection of anti-tissue transglutaminase antibody (anti-tTG) in human serum. This label-less immunosensor was introduced by magnetically attaching FMBs onto the working electrode surface with a neodium magnet. The FMBs were utilized as a sensing interface and had carboxylic acid groups for tTG molecules, which could selectively link the target anti-tTG antibody. The FMBs modification steps were carried out in microcentrifuge tubes and concentrated with magnetic force before electrochemical analyses. The specific immuno-interactions on the FMBs surface were characterized by using the electrochemical and microscopic techniques, and in the presence of anti-tTG antibodies, they were captured by tTG-immobilized magnetic beads, and significant increases were observed in impedimetric response. The magneto biosensor response was linearly related to the anti-tTG antibody level in a broad linear range of 0.125–15.62 U/mL and a low detection limit (LOD) of 0.04 U/mL. Additionally, this magneto sensor was stable, repeatable, reproducible, selective, and sensitive for determination of the anti-tTG. The commercial enzyme-linked immunosorbent assay (ELISA) method was employed to compare the responses of the suggested immunosensor in actual samples. The magneto biosensor results were in good agreement with the ELISA reference technique results. Consequently, the biosensor performance in the analysis of serum samples was acceptable.Graphical

The escalating global prevalence of allergies presents a substantial public health challenge. Immunoglobulin E (IgE) serves as a key biomarker for allergic diseases, often measured in blood serum by ELISA immunoassays. Despite recent interest in minimally invasive sampling of biological fluids, the low sample volumes and IgE concentrations demand highly sensitive methodologies, typically confined to centralized laboratories. In this article, a decentralizable approach based on competitive immunoassays using Pd nanocluster (PdNCs)-labelled antibodies for electrochemical detection is proposed. With this aim, PdNCs were successfully bioconjugated with an anti-hIgE antibody to perform competitive immunoassays. To improve the analytical capabilities of the methodology, disposable screen-printed carbon electrodes with dual working electrodes were used for enhancing precision. Prior electrodeposition of PdNCs at − 0.6 V for 90 s significantly improved sensitivity (7.1 µA g ng⁻1) and lowered the limit of detection (LoD) to 0.3 ng g⁻1 for PdNCs determination. The use of PdNCs as labels resulted in an improvement in the LoD for IgE determination. Calibration curves performed using competitive immunoassays for IgE determination, ranging from 10−5 to 102 ng g−1, demonstrated sensitivity comparable to high-tech methods, with a LoD of 0.008 ng g−1 for electrochemical measurements. Bimodal detection of Pd (linear sweep voltammetry and inductively coupled plasma–mass spectrometry) in various biological fluids (saliva, tears, nasal exudate, capillary blood, and blood serum) revealed significant differences in IgE levels between allergic and non-allergic individuals. Notably, capillary blood correlated strongly with serum blood, and a certain correlation has also been found with nasal exudate. The electrochemical approach, combining sensitivity and precision with non-invasive sampling, offers a simplified alternative for IgE determination in allergic disease.Graphical

Carbon quantum dot (CQD)–based fluorescent nanosensor platforms were developed using gastric cancer-associated Heliobacter pylori (H. pylori) genes. N-doped CQDs were synthesized using two different organic acids (citric acid and malic acid) and ethylenediamine by the microwave method. The photophysical and photochemical properties of the synthesized CQDs were investigated by ultraviolet–visible, fluorescence, and Fourier-transform infrared spectra. The surface of the synthesized N-doped CQDs was conjugated with single-stranded DNA (ssDNA), which is specific for gastric cancer. Ethidium bromide, a selective dye, shows enhanced fluorescence intensity upon intercalating with DNA. In the blue-emissive CQD-ssDNA nanoprobe system, the fluorescence intensity was quenched by ethidium bromide due to Förster resonance energy transfer (FRET) processes. When complementary ssDNA was introduced, the ethidium bromide strongly intercalated with the newly formed double-stranded DNA, shifting to a red emission. Using this ratiometric system, the detection method was improved for gastric cancer–associated genes, achieving a limit of detection (LOD) of 0.098 µM, within a concentration range 1.30 to 11.49 µM. Spike and recovery tests were also conducted to evaluate the precision of the presented method in synthetic saliva solutions, with recoveries ranging from 93.06% to 101.85% The performance of the nanosensors was compared using two different synthesized CQDs.Graphical abstract

A label-free, flexible, and disposable aptasensor was designed for the rapid on-site detection of vancomycin (VAN) levels. The electrochemical sensor was based on lab-printed carbon electrodes (C-PE) enriched with cauliflower-shaped gold nanostructures (AuNSs), on which VAN-specific aptamers were immobilized as biorecognition elements and short-chain thiols as blocking agents. The AuNSs, characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), enhanced the electrochemical properties of the platform and the aptamer immobilization active sites. The developed disposable aptasensor allowed label-free detection of VAN via electrochemical impedance spectroscopy (EIS) across a wide range of concentrations (50–1000 nM), with a limit of detection (LOD) of 1.721 nM. The aptasensor presented good selectivity against some commonly found interferences in human serum and milk and was successfully applied to the analysis of these samples.Graphical

The hydrothermal synthesis is presented of copper-doped carbon dots (Cu-CDs) from citric acid, urea, and copper chloride, resulting in blue-fluorescent particles with stable emission at 438 nm when excited at 340 nm. Through comprehensive spectroscopic and microscopic characterization (FTIR, XPS, UV, and HRTEM), the Cu-CDs demonstrated remarkable stability across varying pH levels, ionic strengths, temperatures, and UV exposure. Notably, Cu-CDs exhibit ultra-sensitive and selective detection of hexavalent chromium [Cr(VI)] ions in aqueous environments driven by fluorescence quenching. The system showed a robust linear response to Cr(VI) in the 0–80 µM range, with an impressive limit of detection (LOD) of 0.186 µM, significantly lower than the WHO’s permissible limit of 0.96 µM. These findings position Cu-CDs as an effective tool for environmental monitoring and water safety applications.Graphical

A lateral flow assay (LFA) has been developed that can be used in point-of-care (PoC) use for the sensitive determination of leptin hormone. The limit of detection value was 0.158 ng/mL and the limit of quantification value was 0.479 ng/mL for leptin hormone. The stability studies showed that the assay response was equal to the initial value even after 6 months. LFA accuracy tests performed in commercial artificial serum samples were compared with the enzyme-linked immunosorbent assay (ELISA). The obtained recovery values between 95 and 110% show that the developed LFA can be used for quantitative determination of leptin hormone. As the result of the study, a fast and disposable assay was developed for the determination of leptin hormone, which can be performed with a small amount of sample in less than 15 min without the need for long-term analysis stages, qualified personnel, expensive equipment and devices.Graphical

Accurately detecting cell secretions in complex microenvironments is crucial for understanding cellular communication, disease progression, and therapeutic responses. Traditional methods, such as ELISA, provide limited insight into the spatiotemporal dynamics of secretions, often requiring invasive or endpoint analyses. To address these challenges, we have functionalized the CellStudio platform—previously developed to integrate cell adhesion areas and microbeads patterns—with a novel self-reporting structure-switching signaling aptamer (SSSA) for vascular endothelial growth factor (VEGF) detection. This functionalization enables in situ single-step, real-time quantification of VEGF secretion from hundreds of live mesenchymal stem cell (MSC) clusters over a 24-h period, using standard fluorescence microscopy without the need for cell fixation. The spatial resolution provided by this system enables precise, localized monitoring of secretion events without the need to add extra reagents. This user-friendly platform is easily adaptable to conventional laboratory workflows, offering a versatile tool with potential for studying cellular behavior in real time with minimal technical barriers.Graphical abstract

PdRuO2/PVP nanomaterial was synthesized using a straightforward method and characterized using advanced analytical methods such as TEM, XRD, XPS, elemental mapping and SEM. The synthesized PdRuO2/PVP nanomaterial was used as an ionophore in potentiometric sensor electrodes and successfully adapted to Cr3+ ion detection in a large number of aqueous samples. Several experimental parameters of the PdRuO2/PVP sensor such as potentiometric behavior, selectivity, repeatability, response time, pH, titration, and recovery in real samples were investigated. Potentiometric behavioral characteristics were performed in the concentration range 1 × 10−6–1.0 × 10−1 M. The repeated experiments performed six times showed that there was no deviation in the measurements. The limit of detection of the PdRuO2/PVP potentiometric sensor was very low with a value of 8.6 × 10−8 M. The potentiometric measurements showed that the synthesized PdRuO2/PVP ionophore was highly effective in detecting Cr3+ in a wide pH range of 2.0–8.0 and was found to have a shelf life of over 1 year. As a result, the synthesized PdRuO2/PVP electrode material was found to be highly selective, stable, and applicable for Cr3+ detection.Graphical

In stereolithographic (SLA) 3D printing, objects are constructed by exposing layers of photocurable resin to UV light. It is a highly user-friendly fabrication method that opens a possibility for technology sharing through CAD file online libraries. Here, we present a prototyping procedure of a microfluidics-enhanced dot-blot device (Affiblot) designed for simple and inexpensive screening of affinity molecule characteristics (antibodies, oligonucleotides, cell receptors, etc.). The incorporation of microfluidic features makes sample processing user-friendly, less time-consuming, and less laborious, all performed completely on-device, distinguishing it from other dot-blot devices. Initially, the Affiblot device was fabricated using CNC machining, which required significant investment in manual post-processing and resulted in low reproducibility. Utilization of SLA 3D printing reduced the amount of manual post-processing, which significantly streamlined the prototyping process. Moreover, it enabled the fabrication of previously impossible features, including internal fluidic channels. While 3D printing of sub-millimeter microchannels usually requires custom-built printers, we were able to fabricate microfluidic features on a readily available commercial printer. Open microchannels in the size range 200–300 μm could be fabricated with reliable repeatability and sealed with a replaceable foil. Economic aspects of device fabrication are also discussed.Graphical abstract