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Fluorescent test papers are promising for the wide applications in the assays of diagnosis, environments and foods, but unlike classical dye-absorption-based pH test paper, they are usually limited in the qualitative yes/no type of detection by fluorescent brightness, and the colorimetry-based quantification remains a challenging task. Here, we report a single dual-emissive nanofluorophore probe to achieve the consecutive color variations from blue to red for the quantification of blood glucose on its as-prepared test papers. Red quantum dots were embedded into silica nanoparticles as a stable internal standard emission, and blue carbon dots (CDs) were further covalently linked onto the surface of silica, in which the ratiometric fluorescence intensity of blue to red is controlled at 5:1. While the oxidation of glucose induced the formation of Fe 3+ ions, the blue emission of CDs was thus quenched by the electron transfer from CDs to Fe 3+ , displaying a serial of consecutive color variations from blue to red with the dosage of glucose. The high-quality test papers printed by the probe ink exhibited a dosage-sensitive allochromatic capability with the clear differentiations of ~5, 7, 9, 11 mM glucose in human serum (normal: 3–8 mM). The blood glucose determined by the test paper was almost in accordance with that measured by a standard glucometer. The method reported here opens a window to the wide applications of fluorescent test paper in biological assays. [ABSTRACT FROM AUTHOR]

Abstract: Trace penicilloic acid allergen frequently leads to various fatal immune responses to many patients, but it is still a challenge to directly discriminate and detect its residue in penicillin by a chemosensing way. Here, we report that silver-coated gold nanoparticles (Au@Ag NPs) exhibit a structure-selective hot-spot Raman enhancement capability for direct identification and detection of trace penicilloic acid in penicillin. It has been demonstrated that penicilloic acid can very easily link Au@Ag NPs together by its two carboxyl groups, locating itself spontaneously at the interparticle of Au@Ag NPs to form strong Raman hot-spot. At the critical concentration inducing the nanoparticle aggregation, Raman-enhanced effect of penicilloic acid is ~60,000 folds higher than that of penicillin. In particular, the selective Raman enhancement to the two carboxyl groups makes the peak of carboxyl group at C6 of penicilloic acid appear as a new Raman signal due to the opening of β-lactam ring of penicillin. The surface-enhanced Raman scattering (SERS) nanoparticle sensor reaches a sensitive limit lower than the prescribed 1.0‰ penicilloic acid residue in penicillin. The novel strategy to examine allergen is more rapid, convenient and inexpensive than the conventional separation-based assay methods. [Copyright &y& Elsevier]

Recent advancements in super-resolution nanoscopy allowed the study of mitochondrial biology at nanoscale and boosted the understanding its correlated cellular processes those were previously poorly understood. Nevertheless, studying mitochondrial ultrastructure remains a challenge due to the lack of probes that could target specific mitochondrial substances (e.g. cristae or mtDNA) and survive under harsh super-resolution optical conditions. Herein, in this work, we have rationally constructed a pyridine-BODIPY (Py-BODIPY) derivative that could target mitochondrial membrane in living cells without interfering its physiological microenvironments. Furthermore, we found Py-BODIPY is a membrane potential independent probe, hence it is not limit to live-cell staining but also showed a strong internalization into pre-fixed and stimulus disrupted sample. Importantly, its cristae specificity and superb photostability allow the observation of mitochondrial dynamic nano-structures with an unprecedented resolution, allow demonstrating how mitochondrial 3D ultrastructure evolved under oxidative phosphorylation condition. • Py-BODIPY is a ΔΨm independent mitochondrial probe. • Py-BODIPY showed superb photostability and increased cristae resolution. • Py-BODIPY revealed mitochondrial 3D dynamics at nanoscale. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) ultrastructure progression under proteohormone stimulation provide valuable clues for understanding conditions associated with obesity and diabetes. Current available LDs probes either alter intra-LDs environments or lack photo-resistance; thus, this research domain is poorly understood. In this work, a N–B–O type BODIPY- hexylcarbazole derivative named BoCz-Lip was rationally designed while achieving specific LDs live-cell targeting. BoCz-Lip showed minimal impact on cell viability as well as internal LDs' protein, triglyceride and cholesterol level. Along with its good photostability, it can be used to monitor LDs evolution under super-resolution nanoscopy. More importantly, we concluded how proteohormone could influence LDs ultrastructure, offering a better understanding for correlating diseases at the nanoscale. • BoCz-Lip has specific fluorescent response against LDs' phospholipids. • BoCz-Lip to uncover LDs morphology under STED nanoscopy. • BoCz-Lip showed minimal impact on cell viability as well as internal LDs' protein, triglyceride and cholesterol level. [ABSTRACT FROM AUTHOR]