Everlasting rhodamine dyes and true deciding factors in their STED microscopy performance.

The authors took an independent and closer look at the family of red-emitting rhodamine dyes known for a decade due to their excellent performance in STED microscopy. After the family was further extended, the true grounds of this performance became clear. Small-molecule protective agents and/or auxiliary groups were attached at two different sites of the dye's scaffold. Thus, a rhodamine core, which is already quite photostable as it is, and an intramolecular stabilizer - a 4-nitrobenzyl or a 4-nitrobenzylthio group were combined to give potentially "everlasting dyes". The fluorescence quantum yields (Φf) and the fluorescence lifetimes (τ) of the modified dyes were thoroughly measured with comparison to those of the parent dyes. The correlation of their STED performance with photostability and fluorescence color stability under illumination in water were explored. Unexpectedly, the anaerobic GSDIM (GOC) buffer proved unhelpful with respect to STED performance. It was demonstrated that, even dyes with a Φf of only 14-17% allow STED imaging with a sufficient photon budget and good signal-to-noise ratio. For the dyes with photostabilizing groups (PSG) the Φf values are 4-5 times lower than in the reference dyes, and lifetimes τ are also strongly reduced. Noteworthy are very high fluorescence color stability and constant or even increasing fluorescence signal under photobleaching in bulk aqueous solutions, which suggests a sacrificing role of the 4-nitrobenzyl-containing moieties. Straightforward and improved recipes for "last-minute" modifications and preparations of "self-healing" red-emitting fluorescent tags are described.

Selective flexible packaging pathways of the segmented genome of influenza A virus.

The genome of influenza A viruses (IAV) is encoded in eight distinct viral ribonucleoproteins (vRNPs) that consist of negative sense viral RNA (vRNA) covered by the IAV nucleoprotein. Previous studies strongly support a selective packaging model by which vRNP segments are bundling to an octameric complex, which is integrated into budding virions. However, the pathway(s) generating a complete genome bundle is not known. We here use a multiplexed FISH assay to monitor all eight vRNAs in parallel in human lung epithelial cells. Analysis of 3.9 × 105 spots of colocalizing vRNAs provides quantitative insights into segment composition of vRNP complexes and, thus, implications for bundling routes. The complexes rarely contain multiple copies of a specific segment. The data suggest a selective packaging mechanism with limited flexibility by which vRNPs assemble into a complete IAV genome. We surmise that this flexibility forms an essential basis for the development of reassortant viruses with pandemic potential.

Three dimensional live-cell STED microscopy at increased depth using a water immersion objective.

Modern fluorescence superresolution microscopes are capable of imaging living cells on the nanometer scale. One of those techniques is stimulated emission depletion (STED) which increases the microscope's resolution many times in the lateral and the axial directions. To achieve these high resolutions not only close to the coverslip but also at greater depths, the choice of objective becomes crucial. Oil immersion objectives have frequently been used for STED imaging since their high numerical aperture (NA) leads to high spatial resolutions. But during live-cell imaging, especially at great penetration depths, these objectives have a distinct disadvantage. The refractive index mismatch between the immersion oil and the usually aqueous embedding media of living specimens results in unwanted spherical aberrations. These aberrations distort the point spread functions (PSFs). Notably, during z- and 3D-STED imaging, the resolution increase along the optical axis is majorly hampered if at all possible. To overcome this limitation, we here use a water immersion objective in combination with a spatial light modulator for z-STED measurements of living samples at great depths. This compact design allows for switching between objectives without having to adapt the STED beam path and enables on the fly alterations of the STED PSF to correct for aberrations. Furthermore, we derive the influence of the NA on the axial STED resolution theoretically and experimentally. We show under live-cell imaging conditions that a water immersion objective leads to far superior results than an oil immersion objective at penetration depths of 5-180 µm.

Multicolour nanoscopy of fixed and living cells with a single STED beam and hyperspectral detection.

The extension of fluorescence nanoscopy to larger numbers of molecular species concurrently visualized by distinct markers is of great importance for advanced biological applications. To date, up to four markers had been distinguished in STED experiments featuring comparatively elaborate imaging schemes and optical setups, and exploiting various properties of the fluorophores. Here we present a simple yet versatile STED design for multicolour imaging below the diffraction limit. A hyperspectral detection arrangement (hyperSTED) collects the fluorescence in four spectral channels, allowing the separation of four markers with only one excitation wavelength and a single STED beam. Unmixing of the different marker signals based on the simultaneous readout of all channels is performed with a non-negative matrix factorization algorithm. We illustrate the approach showing four-colour nanoscopy of fixed and living cellular samples.

SRpHi ratiometric pH biosensors for super-resolution microscopy.

Fluorescence-based biosensors have become essential tools for modern biology, allowing real-time monitoring of biological processes within living cells. Intracellular fluorescent pH probes comprise one of the most widely used families of biosensors in microscopy. One key application of pH probes has been to monitor the acidification of vesicles during endocytosis, an essential function that aids in cargo sorting and degradation. Prior to the development of super-resolution fluorescence microscopy (nanoscopy), investigation of endosomal dynamics in live cells remained difficult as these structures lie at or below the ~250 nm diffraction limit of light microscopy. Therefore, to aid in investigations of pH dynamics during endocytosis at the nanoscale, we have specifically designed a family of ratiometric endosomal pH probes for use in live-cell STED nanoscopy.Ratiometric fluorescent pH probes are useful tools to monitor acidification of vesicles during endocytosis, but the size of vesicles is below the diffraction limit. Here the authors develop a family of ratiometric pH sensors for use in STED super-resolution microscopy, and optimize their delivery to endosomes.

Comparison of intuitiveness, ease of use and preference among three prefilled, disposable growth hormone injection pens.

BACKGROUND: Growth hormone (GH) therapy is an effective treatment for growth failure in children. Adherence rates are often low, resulting in poor linear growth. Intuitive and easy-to-use injection devices may improve adherence. OBJECTIVES: To determine injection time, ease of use, intuitiveness and subjects' preference for Norditropin FlexPro (FP) pen (Novo Nordisk A/S, Denmark) versus Genotropin GoQuick (GQ; Pfizer Inc., USA) and Norditropin NordiFlex (NF; Novo Nordisk) pens. METHODS: Subjects aged ≥ 10 to < 18 years, with GH deficiency, Turner syndrome or short stature following small-for-gestational-age birth were randomized to intuitiveness (no instruction) or instruction groups. Time taken to perform an injection, dose accuracy and errors were recorded. Intuitiveness, ease-of-learning and overall preference were assessed using questionnaires. RESULTS: Sixty-four subjects, randomized to intuitiveness (n = 32; mean [SD] age, 13.1 [2.1] years) and instruction (n = 32; 13.4 [2.0] years) groups, required less time to perform the injection with FP than with GQ (mean [SD], intuitiveness 39.8 s [17.0] vs. 65.6 s [42.9], p < 0.01; instruction 40.7 s [19.7] vs. 48.1 s [25.8], p < 0.05), and a similar amount of time with NF. NF and FP were more accurate than GQ (intuitiveness group only). Fewer errors were recorded with NF followed by FP and GQ. FP and NF were considered easier to learn than GQ in both groups. In the intuitiveness group, the majority of subjects (31/32) felt confident using FP without instruction. FP was the device of overall preference in both groups. CONCLUSION: FP was the device that was most intuitive, easiest to use and the device of overall preference.

Intuitiveness, ease of use, and preference of a prefilled growth hormone injection pen: a noninterventional, randomized, open-label, crossover, comparative usability study of three delivery devices in growth hormone-treated pediatric patients.

BACKGROUND: Growth hormone (GH) is used to treat pediatric and adult GH deficiency (GHD) and growth failure in, among others, patients with Turner syndrome or children born small for gestational age. To improve treatment adherence, self-injection devices should be easy to learn, easy to use, and well accepted, especially in pediatric patients. Several GH pen devices are available, each with distinct features designed for specific patient needs. OBJECTIVES: This study compared injection time and intuitiveness of a prefilled test injection device (Norditropin FlexPro, Novo Nordisk A/S, Bagsværd, Denmark) with those of 2 commercially available durable injection devices (easypod, Merck Serono SA, Geneva, Switzerland; and Genotropin, Pfizer Inc, New York, New York) in GH-treated pediatric patients. Dose accuracy, application errors, intuitiveness, usability, device features, ease of learning, ease of use, and overall preference were also assessed. METHODS: This noninterventional, randomized, open-label, crossover study enrolled patients aged ≥10 to <18 years who were diagnosed with GHD or Turner syndrome or were born small for gestational age. Patients were allocated to an intuitiveness group (without instruction) or an instruction group and assigned to 1 of 3 sequences of device testing. For each device, time taken to deliver a mock injection of test medium (FlexPro) or GH (easypod and Genotropin) into an Eppendorf tube and the delivered dose were measured. Dose accuracy and application errors were assessed by a health care professional. Patients assessed the intuitiveness (intuitiveness group only), device features, ease of learning, ease of use, and overall preference of the devices using questionnaires. RESULTS: Included in the study were 56 patients (mean [SD] age, 13.6 [2.1] years; 63% male; GHD, 44 patients; Turner syndrome, 3; born small for gestational age, 9): 30 in the intuitiveness group and 26 in the instruction group. In the intuitiveness group, the mean (SD) mock injection time was significantly shorter with FlexPro (47.0 [49.0] seconds) than with the easypod (219.2 [72.6] seconds; P < 0.001) or the Genotropin pen (95.1 [78.4] seconds; P < 0.01). In the instruction group, injection time was also shortest with FlexPro (30.7 [10.8] seconds vs 59.6 [13.1] with easypod and 40.7 [18.6] with the Genotropin pen; both, P < 0.001). Most patients (70%) ranked FlexPro as the most intuitive device (easypod, 0%; Genotropin, 30%). In both the intuitiveness and instruction groups, a significantly greater proportion of patients considered FlexPro easiest to learn compared with the easypod and Genotropin devices (both, P < 0.001), although more patients preferred the easypod or Genotropin devices than FlexPro with regard to appearance (intuitiveness group: FlexPro, 8 patients; easypod, 9; and Genotropin, 13; instruction group: FlexPro, 4; easypod, 10; and Genotropin, 12) and quality (intuitiveness group: FlexPro, 6 patients; easypod, 10; and Genotropin, 14; instruction group: FlexPro, 8; easypod, 12; and Genotropin, 6), and easy- pod's delivery feedback feature was preferred by more patients (intuitiveness group: FlexPro, 8 patients; easypod, 14; Genotropin, 8; instruction group: FlexPro, 8; easypod, 14; and Genotropin, 4). Dose accuracies (as assessed by weighing the delivered dose and calculating variation in the delivered dose by device) were 4.6% with FlexPro, 14.6% with easypod, and 20.6% with the Genotropin pen in the intuitiveness group, and 2.7% with FlexPro, 5.8% with easypod, and 24.4% with the Genotropin pen in the instruction group. CONCLUSION: In this study, Norditropin FlexPro was associated with shorter injection times, higher dose accuracy, and greater intuitiveness, and was rated as easier to learn compared with the easypod and Genotropin devices.

Laser-assisted photoablation of human pluripotent stem cells from differentiating cultures.

Due to their pluripotency and their self-renewal capacity, human pluripotent stem cells (hPSC) provide fascinating perspectives for biomedical applications. In the long term, hPSC-derived tissue-specific cells will constitute an important source for cell replacement therapies in non-regenerative organs. These therapeutic approaches, however, will critically depend on the purity of the in vitro differentiated cell populations. In particular, remaining undifferentiated hPSC in a transplant can induce teratoma formation. In order to address this challenge, we have developed a laser-based method for the ablation of hPSC from differentiating cell cultures. Specific antibodies were directed against the hPSC surface markers tumor related antigen (Tra)-1-60 and Tra-1-81. These antibodies, in turn, were targeted with nanogold particles. Subsequent laser exposure resulted in a 98,9 +/- 0,9% elimination of hPSCs within undifferentiated cell cultures. In order to study potential side effects of laser ablation on cells negative for Tra-1-60 and Tra-1-81, hPSC were mixed with GFP-positive hPSC-derived neural precursors (hESCNP) prior to ablation. These studies showed efficient elimination of hPSC while co-treated hESCNP maintained their normal proliferation and differentiation potential. In vivo transplantation of treated and untreated mixed hPSC/hESCNP cultures revealed that laser ablation can dramatically reduce the risk of teratoma formation. Laser-assisted photothermolysis thus represents a novel contact-free method for the efficient elimination of hPSC from in vitro differentiated hPSC-derived somatic cell populations.