Progress on dot-blot assay as a promising analytical tool: Detection from molecules to cells

Upconversion Nanoparticle-Based Dot-Blot Immunoassay for Quantitative Biomarker Detection

Dot-blot immunoassays are widely used for the user-friendly detection of clinical biomarkers. However, the majority of dot-blot assays have only limited sensitivity and are only used for qualitative or semiquantitative analysis. To overcome this limitation, we have employed labels based on photon-upconversion nanoparticles (UCNPs) that exhibit anti-Stokes luminescence and can be detected without optical background interference. First, the dot-blot immunoassay on a nitrocellulose membrane was optimized for the quantitative analysis of human serum albumin (HSA), resulting in a limit of detection (LOD) of 0.19 ng/mL and a signal-to-background ratio (S/B) of 722. Commercial quantum dots were used as a reference label, reaching the LOD of 4.32 ng/mL and the S/B of 3, clearly indicating the advantages of UCNPs. In addition, the potential of UCNP-based dot-blot for real sample analysis was confirmed by analyzing spiked urine samples, reaching the LOD of 0.24 ng/mL and recovery rates from 79 to 123%. Furthermore, we demonstrated the versatility and robustness of the assay by adapting it to the detection of two other clinically relevant biomarkers, prostate-specific antigen (PSA) and cardiac troponin (cTn), reaching the LODs in spiked serum of 9.4 pg/mL and 0.62 ng/mL for PSA and cTn, respectively. Finally, clinical samples of patients examined for prostate cancer were analyzed, achieving a strong correlation with the reference electrochemiluminescence immunoassay (recovery rates from 89 to 117%). The achieved results demonstrate that UCNPs are highly sensitive labels that enable the development of dot-blot immunoassays for quantitative analysis of low-abundance biomarkers.

Development of DNA aptamers targeting B7H3 by hybrid-SELEX: an alternative to antibodies for immuno-assays

Antibodies have been extensively used in numerous applications within proteomics-based technologies, requiring high sensitivity, specificity, a broad dynamic range for detection, and precise, reproducible quantification. Seeking alternatives to antibodies due to several inherent limitations of antibodies is an area of active research of tremendous importance. Recently, aptamers have been receiving increasing attention, because they not only have all of the advantages of antibodies, but also have unique advantages, such as thermal stability, low cost, and unlimited applications. Aptamers are gaining importance in immunological studies and can potentially replace antibodies in immunoassays. B7H3, an immunoregulatory protein belonging to the B7 family, is an attractive and promising target due to its overexpression in several tumor tissues while exhibiting limited expression in normal tissues. This study employed hybrid-SELEX with next-generation sequencing to select ssDNA aptamers specifically binding to the B7H3 protein. These aptamers demonstrated versatility across various assays, including flow cytometry, dot-blot, and immunohistochemistry. Effective performance in sandwich dot-blot assays and western blot analysis suggests their potential for diagnostic applications and demonstrates their adaptability and cost-effectiveness in diverse protein detection techniques.

Nanozyme colourimetry based on temperate bacteriophage for rapid and sensitive detection of Staphylococcus aureus in food matrices

Although bacteriophage-based biosensors are promising tools for rapid, convenient, and sensitive detection of Staphylococcus aureus in food products, the effect of biosensors using temperate phages as biorecognition elements to detect viable S. aureus isolates remains unclear. In this study, three temperate S. aureus phages were isolated and their biological features (one-step growth, host range, pH stability, temperature stability, and adsorption rate) were evaluated as the biological element. The selected phage SapYZUs8 was immobilized on the nanozyme Cu-MOF via electrostatic interactions to generate SapYZUs8@Cu-MOF, and its detection performance in real food (skim milk and pork) was then evaluated. Compared with phages SapYZUm7 and SapYZUs16, phage SapYZUs8 exhibited a broader host range, greater pH stability (3-12), and a better absorption rate (92 %, 8 min) suitable for S. aureus detection, which is likely the result of the DNA replication (DNA helicase) and phage tail protein genes in the SapYZUs8 genome. Therefore, phage SapYZUs8 was fixed on Cu-MOF to generate SapYZUs8@Cu-MOF, which exhibited good sensitivity and specificity for rapid colourimetric detection of viable S. aureus. The method took <0.5 h, and the detection limit was 1.09 × 102 CFU/mL. In addition, SapYZUs8@Cu-MOF was successfully employed for the colourimetric detection of S. aureus in food samples without interference from different food additives, NaCl concentrations, or pH values. With these benefits, it allows rapid visual assessment of S. aureus levels.

Colistin Effects on Emphysematous Lung in an LPS-Sepsis Model

Emphysema is prevalent in various respiratory diseases like Chronic Obstructive Pulmonary Disease (COPD) and cystic fibrosis. Colistin and vasoconstrictive drugs are crucial for treating these patients when diagnosed with sepsis in the ICU. This study examines colistin impact in ether-induced emphysematous septic and non-septic animals, focusing on lung pathophysiology and inflammatory responses, including IL-1β, TNF-α, AMPK, caspase-3, cyclin-D1, and colistin levels in lung tissue. All animals exhibited significant emphysematous changes, accentuated by LPS-induced septic conditions, validating the emphysema model and highlighting the exacerbating effect of sepsis on lung pathology. Colistin, alone or with vasoconstrictive drugs, stimulated immune responses through increased inflammatory cell infiltration and the presence of lymphocytes, indicating potential immunomodulatory effects. Vasoconstriction did not alter the effects of colistin or sepsis but correlated with increased colistin levels in the lungs of septic animals. These observations suggest a potential interplay between vasoconstrictive drugs and colistin distribution/metabolism, leading to enhanced local concentrations of colistin in the lung microenvironment. The findings suggest the need for further investigations to optimize colistin and vasoconstrictive drug delivery in critically ill patients with lung pathologies. Understanding these complexities may guide more effective management of inflammatory responses and lung pathologies in these critical conditions.

Integrated multifunctional nanoplatform for fluorescence detection and inactivation of Staphylococcus aureus

Foodborne illness caused by Staphylococcus aureus (S. aureus) has posed a significant threat to human health. Herein, an integrated multifunctional nanoplatform was developed for fluorescence detection and inactivation of S. aureus based on cascade signal amplification coupled with single strand DNA-template copper nanoparticles (ssDNA-Cu NPs). Benefiting from reasonable design, one-step cascade signal amplification was achieved through strand displacement amplification combined with rolling circle amplification, followed by in-situ generation of copper nanoparticles. S. aureus detection could be performed through naked eye observation and microplate reader measurement of the red fluorescence signal. The multifunctional nanoplatform had satisfactory specificity and sensitivity, achieving 5.2 CFU mL^-1 detection limit and successful detection of 7.3 CFU of S. aureus in spiked egg after < 5 h of enrichment. Moreover, ssDNA-Cu NPs could eliminate S. aureus to avoid secondary bacterial contamination without further treatment. Therefore, this multifunctional nanoplatform has potential application in food safety dtection.

Critical-Illness: Combined Effects of Colistin and Vasoactive Drugs: A Pilot Study

Colistin is often used as a last resort for treating multidrug-resistant infections, particularly in critically ill patients in intensive care units. Nonetheless, its side effects, including myopathy, require careful monitoring. Vasoconstrictive drugs are also used in intensive care to increase blood pressure and improve blood flow to vital organs, which can be compromised in critically ill patients. The exact mechanism of colistin-induced muscle toxicity is of significant interest due to its potential intensive-care clinical implications. Colistin alone or in combination with vasoconstrictive agents was administrated in non-septic and LPS-induced septic animals for 10 days. Histopathological evaluation of the gastrocnemius muscle and dot-blot protein tissue analysis were performed. Increased intramuscular area, de-organization of the muscle fibers and signs of myopathy were observed in colistin-treated animals. This effect was ameliorated in the presence of vasoconstrictive drugs. Administration of colistin to septic animals resulted in a decrease of AMPK and cyclin-D1 levels, while it had no effect on caspase 3 levels. Vasoconstrictive drugs' administration reversed the effects of colistin on AMPK and cyclin D1 levels. Colistin's effects on muscle depend on septic state and vasoconstriction presence, highlighting the need to consider these factors when administering it in critically ill patients.

Cyanostilbene-based fluorescent paper array for monitoring fish and meat freshness via amino content detection

The detection of biogenic amines released from degraded meats is an effective method for evaluating meat freshness. However, existing traditional methods like titration are deemed tedious, while the use of sophisticated analytical instruments is not amenable to field testing. Herein, a cyanostilbene-based fluorescent array was rapidly fabricated using macroarray synthesis on a cellulose paper surface to detect amines liberated from spoiled beef, fish, and chicken. The fluorescence changes of immobilized molecules from the interaction with gaseous amines were used to monitor changes in freshness levels. Thanks to the high-throughput nature of macroarray synthesis, a set of highly responsive molecules such as pyridinium and dicyanovinyl moieties were quickly revealed. Importantly, this method offers flexibility in sensing applications including (1) sensing by individual sensor molecules, where the fluorescence response correlated well with established titration methods, and (2) collective sensing whereby chemometric analysis was used to provide a cutoff of freshness with 73-100% accuracy depending on meat types. Overall, this study paves the way for a robust and cost-effective tool for monitoring meat freshness.

Fast, low-cost and highly specific colorimetric RT-LAMP assays for inference of SARS-CoV-2 Omicron BA.1 and BA.2 lineages

The RT-LAMP assays can quickly and cheaply infer and distinguish colorimetrically two lineages (BA.1 and BA.2) of the Omicron variant, enabling the rationalization of genetic sequencing.