Background MicroRNAs (miRNAs) are small, conserved, noncoding RNAs regulating gene expression that functions in RNA silencing and post-transcriptional regulation of gene expression. Altered miRNA profiles have been implicated in many human diseases, and due to their circulating abilities, they have excited great interest in their use as clinical biomarkers. The development of innovative methods for miRNA detection has become of high scientific and clinical interest. Methods We developed a diffusion-driven microbead assay and combined it with an antibody-based miRNA detection. The diffusion process was carried out in two different approaches a) co-diffusion of miRNA and antibodies (termed diffusion approach I, DAI) and b) diffusion of miRNA in an antibody-saturated environment (DAII). In both approaches, neutravidin-coated microbeads were loaded with specific biotinylated DNA capture probes, which targets either miR-21-5p, miR-30a-3p or miR-93-5p. The miRNAs were time- and dose-dependently detected in a diffusion microchamber by primary anti-DNA:RNA hybrid and fluorescence-labeled secondary antibodies using our in-house developed inverse fluorescence microscope imaging platform VideoScan. Results Our assay offers the advantage that several target molecules can be detected simultaneously and in real-time in one reaction environment (multiplex), without any amplification steps. We recorded the diffusion process over a period of 24 h and found that the reaction was almost completed after 2 h. The specificity of the assay was 96.7 % for DAI and 92.3 % for DAII. The detection limits were in a concentration range of 0.03-0.43 nM for DAI and 0.14-1.09 nM for DAII, depending on the miRNA. Conclusion The miRNAs are successively exposed to the capture probe-loaded randomly ordered microbeads (p value of CSR 0.23-0.96), which leads to microbeads that become saturated with the target molecules first in front rows. Non-bonded miRNAs continue to diffuse further and can therefore subsequently bind to the microbeads with free binding sites. Our detection principle differs from other microbead assays, in which all microbeads are simultaneously mixed with the sample solution, so that all target molecules bind equally distributed to the microbeads, resulting in an averaged signal intensity.

Neurodegenerative diseases (NDs) are characterized by abnormalities within neurons of the brain or spinal cord that gradually lose function, eventually leading to cell death. Upon examination of affected tissue, pathological changes reveal a loss of synapses, misfolded proteins, and activation of immune cells—all indicative of disease progression—before severe clinical symptoms become apparent. Early detection of NDs is crucial for potentially administering targeted medications that may delay disease advancement. Given their complex pathophysiological features and diverse clinical symptoms, there is a pressing need for sensitive and effective diagnostic methods for NDs. Biomarkers such as microRNAs (miRNAs) have been identified as potential tools for detecting these diseases. We explore the pivotal role of miRNAs in the context of NDs, focusing on Alzheimer’s disease, Parkinson’s disease, Multiple sclerosis, Huntington’s disease, and Amyotrophic Lateral Sclerosis. The review delves into the intricate relationship between aging and NDs, highlighting structural and functional alterations in the aging brain and their implications for disease development. It elucidates how miRNAs and RNA-binding proteins are implicated in the pathogenesis of NDs and underscores the importance of investigating their expression and function in aging. Significantly, miRNAs exert substantial influence on post-translational modifications (PTMs), impacting not just the nervous system but a wide array of tissues and cell types as well. Specific miRNAs have been found to target proteins involved in ubiquitination or de-ubiquitination processes, which play a significant role in regulating protein function and stability. We discuss the link between miRNA, PTM, and NDs. Additionally, the review discusses the significance of miRNAs as biomarkers for early disease detection, offering insights into diagnostic strategies.

Background Lipids and amphiphilic molecules are ubiquitous and play a central role in cell signalling, cell membrane structure, and lipid transport in the human body. However, they also appear in many diseases such as atherosclerosis, cardiovascular diseases, infections, inflammatory diseases, cancer, and autoimmune diseases. Thus, it is necessary to have detection systems for lipids and amphiphilic molecules. Microbeads can be one of these systems for the simultaneous detection of different lipophilic biomarkers. Methods Based on the fundamentals of microbead development, novel hydrophobic microbeads were produced. These not only have a hydrophobic surface, but are also fluorescently encoded and organic solvent resistant. The challenge after the development of the hydrophobic microbeads was to immobilise the amphiphilic molecules, in this study phospholipids, on the microbead surface in an oriented direction. After successful immobilisation of the biomarkers, a suitable antibody based detection assay was established. Results By passive adsorption, the phospholipids cardiolipin, phosphatidylethanolamine and phosphatidylcholine could be bound to the microbead surface. With the application of the enzymes phospholipase A2 and phospholipase C, the directional binding of the phospholipids to the microbead surface was demonstrated. The detection of directional binding indicated the need for the hydrophobic surface. Microbeads with no hydrophobic surface bound the phospholipids non-directionally (with the hydrophilic head) and were thus no longer reactively accessible for detection. Conclusion With the newly developed hydrophobic, dual coded and solvent stable microbeads it is possible to bind amphiphilic biomolecules directionally onto the microbead surfaces.

BACKGROUND: The 3D printing is relevant as a manufacturing technology of functional models for forensic, pharmaceutical and bioanalytical applications such as drug delivery systems, sample preparation and point-of-care tests. OBJECTIVE: Melting behavior and autofluorescence of materials are decisive for optimal printing and applicability of the product which are influenced by varying unknown additives. METHODS: We have produced devices for bioanalytical applications from commercially available thermoplastic polymers using a melt-layer process. We characterized them by differential scanning calorimetry, fluorescence spectroscopy and functional assays (DNA capture assay, model for cell adhesion, bacterial adhesion and biofilm formation test). RESULTS: From 14 tested colored, transparent and black materials we found only deep black acrylonitrile-butadiene-styrene (ABS) and some black polylactic acid (PLA) useable for fluorescence-based assays, with low autofluorescence only in the short-wave range of 300-400 nm. PLA was suitable for standard bioanalytical purposes due to a glass transition temperature of approximately 60 degrees C, resistance to common laboratory chemicals and easy print processing. For temperature-critical methods, such as hybridization reactions up to 90 degrees C, ABS was better suited. CONCLUSIONS: Autofluorescence was not a disadvantage per se but can also be used as a reference signal in assays. The rapid development of individual protocols for sample processing and analysis required the availability of a material with consistent quality over time. For fluorescence-based assays, the use of commercial standard materials did not seem to meet this requirement.

Antibodies are used in diagnostic tests, including enzyme-linked immunosorbent assay (ELISA) and protein arrays. They serve either as a detection molecule or target (e.g., autoantibodies). For point-of-care diagnostics it is important to develop efficient technologies for multiparametric antibody testing to simplify and accelerate the diagnostics. For the realization of microfluidic systems and low-cost alternatives, for example 3D printing or new polymer networks are used.

The rapid and simultaneous detection of DNA and protein biomarkers is necessary to detect the outbreak of a disease or to monitor a disease. For example, cardiovascular diseases are a major cause of adult mortality worldwide. We have developed a rapidly adaptable platform to assess biomarkers using a microfluidic technology. Our model mimics autoantibodies against three proteins, C-reactive protein (CRP), brain natriuretic peptide (BNP), and low-density lipoprotein (LDL). Cell-free mitochondrial DNA (cfmDNA) and DNA controls are detected via fluorescence probes. The biomarkers are covalently bound on the surface of size- (11–15 μm) and dual-color encoded microbeads and immobilized as planar layer in a microfluidic chip flow cell. Binding events of target molecules were analyzed by fluorescence measurements with a fully automatized fluorescence microscope (end-point and real-time) developed in house. The model system was optimized for buffers and immobilization strategies of the microbeads to enable the simultaneous detection of protein and DNA biomarkers. All prime target molecules (anti-CRP, anti-BNP, anti-LDL, cfmDNA) and the controls were successfully detected both in independent reactions and simultaneously. In addition, the biomarkers could also be detected in spiked human serum in a similar way as in the optimized buffer system. The detection limit specified by the manufacturer is reduced by at least a factor of five for each biomarker as a result of the antibody detection and kinetic experiments indicate that nearly 50 % of the fluorescence intensity is achieved within 7 min. For rapid data inspection, we have developed the open source software digilogger, which can be applied for data evaluation and visualization.

Cardiovascular diseases are one of the main reasons for adult mortality in western world, leading to huge liability on healthcare system. Lifestyle, genetic disposition, deficiency of clearly defined risk assessment criteria, as well as high occurrences of misdiagnosis directly contribute to this issue. Due to this fact a rapid and simultaneously detection of biomarkers is necessary. Biomarkers for cardiovascular diseases include hs-CRP, BNP, LDL, HbA1c, ST2 and creatinine. We started to integrated them in a microfluidic microbead chip system that is read-out with our VideoScan technology as proposed earlier. In addition, we develop a software which can be used for the analysis. We integrated the biomarkers in different detection methods (hybridization assays, ELISA, microbead ELISA) and tested those methods as multiplex assays.