Inhibition of amyloid formation of amyloid ß (1-42), amylin and insulin by 1,5-diazacyclooctanes, a spermine-acrolein conjugate.

Amyloid aggregates of proteins are known to be involved in various diseases such as Alzheimer's disease (AD). It is therefore speculated that the inhibition of amyloid formation can play an important role in the prevention of various diseases involving amyloids. Recently, we have found that acrolein reacts with polyamines, such as spermine, and produces 1,5-diazacyclooctane, such as cyclic spermine (cSPM). cSPM could suppress the aggregation of amyloid ß 1-40 (Aß40), one of the causative proteins of AD. This result suggests the potential inhibitory effect of cSPM against Aß 1-42 (Aß42) and other amyloid protein aggregation which are the main pathological features of AD and other diseases. However, the effect on the aggregation of such proteins remains unclear. In this study, the effect of cSPM on the amyloid formation of Aß42, amylin, and insulin was investigated. These three amyloidogenic proteins forming amyloids under physiological conditions (pH 7.4 and 37℃) served as model and are thought to be the causative proteins of AD, type 2 diabetes, and insulin-derived amyloidosis, respectively. Our results indicate that cSPM can suppress the amyloid aggregation of these proteins and reduce cytotoxicity. This study contributes to a better understanding of means to potentially counteract diseases by the means of polyamine and acrolein.

Degradation of insulin amyloid by antibiotic minocycline and formation of toxic intermediates.

Insulin balls, localized insulin amyloids formed at subcutaneous insulin-injection sites in patients with diabetes, cause poor glycemic control owing to impairments in insulin absorption. Our previous study has shown that some insulin balls are cytotoxic, but others are not, implying amyloid polymorphism. Interestingly, the patient with toxic insulin balls had been treated with antibiotic minocycline, suggesting a possible relationship between toxicity of insulin balls and minocycline. However, the direct effect of minocycline on the structure and cytotoxicity of the insulin amyloid is still unclear. Herein, we demonstrated that that minocycline at physiological concentrations induced degradation of insulin amyloids formed from human insulin and insulin drug preparations used for diabetes patients. Interestingly, the process involved the initial appearance of the toxic species, which subsequently changed into less-toxic species. It is also shown that the structure of the toxic species was similar to that of sonicated fragments of human insulin amyloids. Our study shed new light on the clarification of the revelation of insulin balls and the development of the insulin analogs for diabetes therapy.

Molecular detection using aptamer-modified gold nanoparticles with an immobilized DNA brush for the prevention of non-specific aggregation.

Gold nanoparticles (AuNPs) are often used for biosensing. In particular, aptamer-modified AuNPs are often used for colorimetric molecular detection, where target molecule-induced AuNP aggregates can be recognized by a color change from red to blue. However, non-specific aggregation could be induced by various compounds, leading to false-positive results. In this work we employed high-density ssDNA modification on the AuNP surface to prevent non-specific aggregation. The covalently immobilized DNA brush was used as an anchor for an aptamer specific for the target molecule. Herein, as a proof-of-concept study, we demonstrated detection of estradiol (E2), one of the endocrine-disrupting estrogen molecules as a model target, in the presence of antibiotic kanamycin (KN) as a model of co-contaminating compounds that induce non-specific aggregation of AuNPs. We also developed a smartphone dark field microscope (DFM) to visualize AuNP aggregation. Our previous study demonstrated that the observation of light scattering by AuNP aggregates with DFM can be applied for versatile molecular detection. In this work, we could successfully detect E2 with the smartphone DFM, and the results were verified by the results from a conventional benchtop DFM. This study would contribute to the future field applicability of AuNP-based sensors.

YestroSens, a field-portable S. cerevisiae biosensor device for the detection of endocrine-disrupting chemicals: Reliability and stability.

Farming, industry and urbanization lead to increases in the concentrations of potentially harmful compounds in waste, surface and drinking waters. One example of such pollution are estrogens, the steroidal female reproductive hormones. Already at a few nanograms per litre, these hormones can trigger endocrine disruption and cause acute and chronic health problems in humans and wildlife. Here, we present a Saccharomyces cerevisiae estrogen biosensor capable of detecting estradiol, as well as ethinylestradiol, at concentrations of 1 nM. After an initial characterization of the sensor strain performance in an optimal laboratory setting, we focused on developing a biosensor device. We addressed current limitations of biosensors, such as the requirement of the cells for a liquid growth matrix, controlled storage conditions required to preserve cell viability, and the usually required bulky, as well as expensive, laboratory equipment. Our study provides significant new insights into the field of applied biosensors. The system presented in this work takes microorganism-based analytics one step closer to field application in decentralized locations.

Strategies of Immobilizing Cells in Whole-cell Microbial Biosensor Devices Targeted for Analytical Field Applications.

This review summarizes the development of whole-cell biosensors with a special focus on device development and cell immobilization. Integration of biosensor functions in a device will pave the way for field applications in remote areas and resource-limited settings. Firstly, an introduction to the field of whole-cell biosensors is provided, followed by examples of genetic engineering of cells in order to fulfill sensor functions. A framework of requirements to enable future field applications of biosensors is elaborated. A special focus is on different cell immobilization techniques ranging from polymers, to microfluidic devices, immobilization on paper and combinations of these methods. Looking at globally successfully implemented point of care devices such as a home pregnancy test or a blood glucose meter, we conclude the review with thoughts on long-term stability, portability, ease of use and user safety design guidelines for whole-cell biosensor devices.

Silica-Encapsulated DNA-Based Tracers for Aquifer Characterization.

Environmental tracing is a direct way to characterize aquifers, evaluate the solute transfer parameter in underground reservoirs, and track contamination. By performing multitracer tests, and translating the tracer breakthrough times into tomographic maps, key parameters such as a reservoir's effective porosity and permeability field may be obtained. DNA, with its modular design, allows the generation of a virtually unlimited number of distinguishable tracers. To overcome the insufficient DNA stability due to microbial activity, heat, and chemical stress, we present a method to encapsulated DNA into silica with control over the particle size. The reliability of DNA quantification is improved by the sample preservation with NaN3 and particle redispersion strategies. In both sand column and unconsolidated aquifer experiments, DNA-based particle tracers exhibited slightly earlier and sharper breakthrough than the traditional solute tracer uranine. The reason behind this observation is the size exclusion effect, whereby larger tracer particles are excluded from small pores, and are therefore transported with higher average velocity, which is pore size-dependent. Identical surface properties, and thus flow behavior, makes the new material an attractive tracer to characterize sandy groundwater reservoirs or to track multiple sources of contaminants with high spatial resolution.