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Abstract: A novel synthetic route to fluorescent nitrogen bridgehead fused pyridines (NBFPs) was discovered serendipitously during attempts to synthesize a thiazole derivative via a Hantzsch-type thiazole reaction from 2-cyanoethanethioamide and chloroacetone. A mechanism was proposed to rationalize the formation of NBFPs, which guided the subsequent expansion of the reaction scope and optimization of reaction conditions. The scope of the reaction was extended to include arylacetonitriles and esters of 2-(heteroaryl)acetic acids bearing an ortho-positioned pyridine-type nitrogen as a starting material. The structures of selected compounds were confirmed by single-crystal X-ray diffraction. All synthesized NBFPs exhibited pH-sensitive fluorescence and Stokes shifts exceeding 100 nm in several cases. Two compounds, methylthiazole derivative 1 and quinoline derivative 8, displayed pH-dependent emission suitable for lysosomal labelling. However, live-cell microscopy revealed limited colocalization with lysosomal probe Lysotracker Red, suggesting that these probes may localize to other acidic environments as well. Both compounds showed pronounced spectral responsiveness and fluorescence lifetime variations, indicating potential for use as environment-sensitive intracellular sensors. The methyl thiazole derivative 1 exhibited particularly favourable properties, including high photostability, low background fluorescence, minimal cytotoxicity and polarity sensitivity. These findings position NBFPs as a promising class of fluorophores for live-cell imaging and intracellular sensing applications, and warrant further investigation into their structure–function relationships and environmental responsiveness.
Keywords: nitrogen bridgehead fused pyridine, Fluorescence, pH sensitive probes, live-cell imaging, fluorescence lifetime imaging
Published in DiRROS: 03.02.2026; Views: 105; Downloads: 58
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Abstract: Background: The differential diagnosis of cardiac myxomas (CM), the most common benign primary cardiac tumors, is broad and a thorough diagnostic workup is required to establish accurate diagnosis prior to surgical resection. Transthoracic echocardiography (TTE) is usually the first imaging modality used for diagnosis of suspected CM. In a single tertiary centre study, we sought to determine the accuracy, sensitivity, and specificity of TTE in the diagnosis of CM and to determine echocardiographic characteristics indicative of CM. Patients and methods: We retrospectively analyzed clinical, echocardiographic, and pathohistological findings of 73 patients consecutively admitted for suspected CM. Results: After diagnostic workup, 53 (73%) patients were treated surgically at our institution. Based on preoperative TTE, patients were divided into a CM group (n=45, 85%) and non-myxoma (NM) group. Of the 53 pathohistological specimens obtained during surgery, 39 (73%) were CM. The sensitivity and specificity of preoperative echocardiography were 97% and 50%, respectively. The overall accuracy was 85%. All NM tumors were found in an atypical location and 72% of CM were found in a typical position in the left atrium (p < 0.001). Tumors in NM group were significantly smaller than CM (24.3 ± 13.2 mm vs. 37.9 ± 18.3 mm, p = 0.017). Conclusions: Our study confirms very good accuracy of TTE in the diagnosis of CM. The most important echocardiographic characteristics to differentiate between CM and tumors of different etiology are tumor location and size. Smaller tumors presenting at an atypical location are less likely to be diagnosed as CM, and these require additional imaging modalities for accurate diagnosis.
Keywords: cardiac mass, cardiac myxoma, cardiovascular imaging, echocardiography
Published in DiRROS: 16.12.2025; Views: 274; Downloads: 90
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Abstract: Correlative imaging is a powerful tool for revealing information on cell-type structures and their biochemistry, with the potential to inform healthier food choices and improved dietary recommendations. Determination of plant structures and their structural biochemistry advances our understanding of specific structures designed to store different biomolecules within cells and tissues. Compared to the classical biochemical separation techniques, the key advantage of sequential correlative imaging techniques is in relating spatial plant (micro)structures to their biochemistry in a nondestructive manner. Sequential imaging reported here comprises six methodologies on a single sample, a cross-section of a Tartary buckwheat (Fagopyrum tataricum) grain, namely, bright-field and autofluorescence microscopy, fluorescence microspectroscopy, MeV-secondary ion mass spectrometry, micro-particle-induced X-ray emission, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and laser ablation-inductively coupled plasma-mass spectrometry. Results confirm that the stepwise addition of the desired information across several classes of biomolecules and several spatial scales informs the quality and safety of plant-based produce across scales. Therefore, a viable workflow is proposed, enabling sequential spatial analysis of grain and highlighting plant structures' in situ specificity. The advantages and disadvantages of the selected methodologies were critically evaluated.
Keywords: autofluorescence, correlative molecular imaging, element distribution, grain tissues
Published in DiRROS: 07.11.2025; Views: 288; Downloads: 155
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Abstract: Diffractive optical elements such as periodic gratings are fundamental devices in X-ray imaging – a technique that medical, material science, and security scans rely upon. Fabrication of such structures with high aspect ratios at the nanoscale creates opportunities to further advance such applications, especially in terms of relaxing X-ray source coherence requirements. This is because typical grating-based X-ray phase imaging techniques (e.g., Talbot self-imaging) require a coherence length of at least one grating period and ideally longer. In this paper, the fabrication challenges in achieving high-aspect ratio nanogratings filled with gold are addressed by a combination of laser interference and nanoimprint lithography, physical vapor deposition, metal assisted chemical etching (MACE), and electroplating. This relatively simple and cost-efficient approach is unlocked by an innovative post-MACE drying step with hexamethyldisilazane, which effectively minimizes the stiction of the nanostructures. The theoretical limits of the approach are discussed and, experimentally, X-ray nanogratings with aspect ratios >40 are demonstrated. Finally, their excellent diffractive abilities are shown when exposed to a hard (12.2 keV) monochromatic X-ray beam at a synchrotron facility, and thus potential applicability in phase-based X-ray imaging.
Keywords: nanogratings, X-ray imaging, mechanical stability
Published in DiRROS: 08.09.2025; Views: 369; Downloads: 152
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Abstract: Skin cancer is a severe and rapidly advancing condition that can be impacted by multiple factors, including alcohol and tobacco use, allergies, infections, physical activity, exposure to UV light, viral infections, and the effects of climate change. While the steep death tolls continue rising at an alarming rate, lack of symptoms recognition and its preventive measures further worsen the case. In this article, we employ the ISBI-2017 dataset to present an improved FrCN-based hybrid image segmentation method with U-Net to improve detection performance. This paper proposes a hybrid approach using the FrCN-(U-Net) image segmentation technique to enhance results compared to an advanced method for detecting skin cancer types, such as Benign or Melanoma. The classification phase is then handled using the R-CNN algorithm. Our model shows better performance in both training and testing accuracy than any other existing approaches. The results show that the combined method is effective in enhancing early disease diagnosis, which in turn improves treatment outcomes and prognosis. This paper presents an alternative technique for skin cancer detection, which can serve as a guide for clinical practices and public health strategies on how to lower skin-cancer-related deaths.
Keywords: skin tumors, cutaneous melanoma, lesions, imaging techniques, cancel detection and diagnosis, melanoma, preprocessing, melignant tumors
Published in DiRROS: 19.06.2025; Views: 592; Downloads: 316
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