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Biology subjects

Tsolaki, E.

Publications and source records attributed to Tsolaki, E..

7 recordsLinked to original sources

Density-Dependent Colour Scanning Electron Microscopy (DDC-SEM). Applications in the study of calcified tissues and visual impact.

Scanning Electron Microscopy (SEM) is widely used as a technique for materials characterization. It has also been successfully applied to the imaging of biological samples, providing invaluable insights into the topography, morphology and composition of biological structures. A particular method combining different SEM detectors, named Density-Dependent Coloured SEM (DDC-SEM), has proven to be most useful for the identification and visualization of minerals in soft tissues. The method consists of a manipulation of original greyscale SEM images to produce coloured images that provide both topography and density information for samples with components of different densities. Here we provide a discussion on how to use DDC-SEM to aid the visualization and intuitive understanding of pathological calcification. This method has become popular not only for its scientific improvement of conventional SEM greyscale images, but also for its aesthetical merits. Lay summaryScanning Electron Microscopes (SEM) are widely used tools for examining biological materials such as human tissue. Like other electron microscopes, it only produces images in greyscale. SEM has been useful, for instance, in improving our understanding of calcific diseases. These diseases involve the build-up of mineral in the bodys soft tissues, and frequently affect the heart, kidneys, or eyes. This work provides a discussion on using a SEM technique known as Density-Dependent Colour Scanning Electron Microscopy (DDC-SEM), which enhances SEM images through scanning the same area with different detectors, assigning a unique colour to each detectors output, and then overlaying these images.

scientific communication and education↗

Multiscale Multimodal Characterization and Simulation of Structural Alterations in Failed Bioprosthetic Heart Valves

Calcific degeneration is the most frequent type of heart valve failure, with rising incidence due to the ageing population. The gold standard treatment to date is valve replacement. Unfortunately, calcification oftentimes re-occurs in bioprosthetic substitutes, with the governing processes remaining poorly understood. Here, we present a multiscale, multimodal analysis of disturbances and extensive mineralisation of the collagen network in failed bioprosthetic bovine pericardium valve explants with full histoanatomical context. In addition to highly abundant mineralized collagen fibres and fibrils, calcified micron-sized particles previously discovered in native valves were also prevalent on the aortic as well as the ventricular surface of bioprosthetic valves. The two mineral types (fibers and particles) were detectable even in early-stage mineralisation, prior to any macroscopic calcification. Based on multiscale multimodal characterisation and high-fidelity simulations, we demonstrate that mineral occurrence coincides with regions exposed to high haemodynamic and biomechanical indicators. These insights obtained by multiscale analysis of failed bioprosthetic valves may serve as groundwork for the evidence-based development of more durable alternatives. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/529530v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@c7e0b5org.highwire.dtl.DTLVardef@71bdbdorg.highwire.dtl.DTLVardef@15fdc23org.highwire.dtl.DTLVardef@6dbd1c_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

Density-Dependent Color Scanning Electron Microscopy (DDC-SEM) for calcified tissue and pathological calcification.

Scanning electron microscopy (SEM) is widely used for materials characterization. It has also been successfully applied to the imaging of biological samples, providing invaluable insights into the topography, morphology and composition of biological structures, including pathological minerals, in diseases affecting cardiovascular, kidney and ocular tissues. Here we provide a comprehensive and detailed guide on how to use colored SEM to aid the visualization and characterization of pathological calcification, and identify the effects of different sample preparation protocols for the visualisation of these minerals.

pathology↗

Smart sealants for prevention and monitoring of gastrointestinal anastomotic leaks using portable smartphone-controlled ultrasound transducers

Millions of patients every year undergo gastrointestinal surgery. While often lifesaving, sutured and stapled reconnections leak in around 10% of the cases. Penetration of digestive fluids into the peritoneal cavity may lead to dreadful complications, including sepsis and premature death. Modern suture supports and tissue adhesives only insufficiently address the issue. Due to the scarcity of alternatives, surgeons rely on monitoring surrogate markers and clinical symptoms, which oftentimes lack sensitivity and specificity, hence only offering late-stage detection of already fully developed leaks. Here, a first-of-its-kind, modular, intelligent suture support patch capable of sealing and monitoring leaks under harsh gastrointestinal conditions is presented. The smart adhesive layered hydrogel patch provides, in addition to unprecedented tissue sealing under most demanding conditions, unique leak-detection capabilities based on pH and/or enzyme-responsive sensing elements, which can be read out by non-invasive point-of-need ultrasound imaging. Reliable detection of the breaching of sutures in as little as 3 hours in intestinal leak and 15 minutes in gastric leak conditions, and before an actual leak develops, is demonstrated. This technology paves the way for next-generation suture support materials that offer disambiguation in cases of anastomotic leaks based on point-of-need monitoring, without reliance on complex electronics or bulky (bio)electronic implantables. SummaryElectronic-free smart surgical hydrogel sealants leveraging tissue-penetrating polymer networks and trigger-responsive echogenic entities to enable point-of-need monitoring and early anastomotic leak detection using a hand-held ultrasound transducer and a smartphone.

bioengineering↗

Association of cellular and subcellular calcification with phosphorylated tau in the brains of Alzheimer's disease patients.

Brain calcification (calcium phosphate mineral formation) has been reported in the past 100 years in the brains of Alzheimers disease (AD) patients. However, the association between calcification and AD, the triggers for calcification, and its role within the disease are not clear. On the other hand, hyperphosphorylated tau protein (pTau) tangles have been widely studied and recognized as an essential factor in developing AD. In this work, calcification in the brains of AD patients is characterized by advanced electron microscopy and fluorescence microscopy. Results are then compared to samples from cognitively healthy, age-matched donors, and the colocalization of calcification and pTau is investigated. Here, we show that AD patients brains present microcalcification associated with the neural cell nuclei and cell projections, and that these are strongly related to the presence of pTau. The link between microcalcification and pTau suggests a potential new mechanism of brain cell damage. Together with the formation of amyloid plaques and neurofibrillary tangles, microcalcification in neuronal cells adds to a better understanding of the pathology of AD. Finally, the presence of microcalcification in the neuronal cells of AD patients may assist in AD diagnosis, and may open new avenues for developing intervention strategies based on inhibition of calcification.

pathology↗

Invasive breast tumors are characterized by the presence of crystalline nanoparticles

The presence of calcifications on mammograms is a widely used diagnostic marker for breast cancer. While the clinicopathological analysis of breast tissue is well-developed, an in-depth characterisation of the properties of calcifications at the micro and nano scale remained elusive. In this work, we use nano-analytical methods to investigate the calcification present in healthy breast tissue, as well as in benign and malignant breast tumour tissue biopsies. While polycrystalline apatite with lower crystallinity can be found in all breast tissue samples, we show that magnesium-containing nano and micro spherical particles are found only in malignant invasive breast cancers. These particles concentration increases with cancer progression. The discovery of these spherical particles provides new insights into the characteristics of breast calcification associated with malignant tumours and opens new research pathways to a better understanding of breast tumours and their microenvironment in general.

cancer biology↗

Electron microscopy characterization of minerals formed in vitro by human bone cells and vascular smooth muscle cells

Soft tissue mineralization has been found to be a major component of diseases such as aortic valve stenosis and rheumatic heart disease. Cardiovascular mineralization has been suggested to follow mechanisms similar to those of bone formation with several cell culture models been developed over the years to provide mechanistic insights. These cell models have been characterized by a wide range of biochemical and molecular methods, which identified the presence of osteogenic markers and bone-like cells. However, there is a surprisingly small number of studies where the mineral formed in these cell culture models has been characterized by physico-chemical methods, and even fewer studies have compared this mineral to the one produced by bone cells in cultures. Here we investigated the morphology and composition of the minerals formed in cell cultures of vascular smooth muscle cells and bone cells. Electron microscopy and traditional cell mineralization assays were applied, revealing that vascular cells are indeed able to form calcified nodules of elemental composition similar to bone, however with different morphology. Comparison of morphologies of the two minerals to that found in cardiovascular tissue shows that some of tissue calcification resembles the calcified fibers produced by bone cells in vitro. These results suggest that the characterization of the mineral is of utmost importance and its morphology and chemical properties can contribute an important piece of information in the comprehensive analysis of soft tissue mineralization mechanisms, both in in vitro cell culture as well as in clinical samples.

pathology↗