Radiation Hardness Study of Single-Photon Avalanche Diode for Space and High Energy Physics Applications.

The radiation hardness of 180 nm complementary metal-oxide-semiconductor (CMOS) and 55 nm bipolar-CMOS-double-diffused MOS single-photon avalanche diodes (SPADs) is studied using 10 MeV and 100 MeV protons up to a displacement damage dose of 1 PeV/g. It is found that the dark count rate (DCR) levels are dependent on the number and the type of defects created. A new stepwise increase in the DCR is presented. Afterpulsing was found to be a significant contributor to the observed DCR increase. A new model for DCR increase prediction is proposed considering afterpulsing. Most of the samples under test retain reasonable DCR levels after irradiation, showing high tolerance to ionizing and displacement damage caused by protons. Following irradiation, self-healing was observed at room temperature. Furthermore, high-temperature annealing shows potential for accelerating recovery. Overall, the results show the suitability of SPADs as optical detectors for long-term space missions or as detectors for high-energy particles.

A Scaling Law for SPAD Pixel Miniaturization.

The growing demands on compact and high-definition single-photon avalanche diode (SPAD) arrays have motivated researchers to explore pixel miniaturization techniques to achieve sub-10 µm pixels. The scaling of the SPAD pixel size has an impact on key performance metrics, and it is, thereby, critical to conduct a systematic analysis of the underlying tradeoffs in miniaturized SPADs. On the basis of the general assumptions and constraints for layout geometry, we performed an analytical formulation of the scaling laws for the key metrics, such as the fill factor (FF), photon detection probability (PDP), dark count rate (DCR), correlated noise, and power consumption. Numerical calculations for various parameter sets indicated that some of the metrics, such as the DCR and power consumption, were improved by pixel miniaturization, whereas other metrics, such as the FF and PDP, were degraded. Comparison of the theoretically estimated scaling trends with previously published experimental results suggests that the scaling law analysis is in good agreement with practical SPAD devices. Our scaling law analysis could provide a useful tool to conduct a detailed performance comparison between various process, device, and layout configurations, which is essential for pushing the limit of SPAD pixel miniaturization toward sub-2 µm-pitch SPADs.

Fluorescence lifetime imaging with a megapixel SPAD camera and neural network lifetime estimation.

Fluorescence lifetime imaging microscopy (FLIM) is a key technology that provides direct insight into cell metabolism, cell dynamics and protein activity. However, determining the lifetimes of different fluorescent proteins requires the detection of a relatively large number of photons, hence slowing down total acquisition times. Moreover, there are many cases, for example in studies of cell collectives, where wide-field imaging is desired. We report scan-less wide-field FLIM based on a 0.5 MP resolution, time-gated Single Photon Avalanche Diode (SPAD) camera, with acquisition rates up to 1 Hz. Fluorescence lifetime estimation is performed via a pre-trained artificial neural network with 1000-fold improvement in processing times compared to standard least squares fitting techniques. We utilised our system to image HT1080-human fibrosarcoma cell line as well as Convallaria. The results show promise for real-time FLIM and a viable route towards multi-megapixel fluorescence lifetime images, with a proof-of-principle mosaic image shown with 3.6 MP.

High fill-factor miniaturized SPAD arrays with a guard-ring-sharing technique.

We present a novel guard-ring-sharing technique to push the limit of SPAD pixel miniaturization, and to demonstrate the operation of SPAD arrays with a 2.2 µm-pitch, the smallest ever reported. Device simulation and preliminary tests suggest that the optimized device design ensures the electrical isolation of SPADs with guard-ring sharing. 4×4 SPAD arrays with two parallel selective readout circuits are designed in 180 nm CMOS technology. SPAD characteristics for the pixel pitch of 2.2, 3, and 4 µm are systematically measured as a function of an active diameter, active-to-active distance, and excess bias. For a 4 µm-pitch, the fill factor is 42.4%, the maximum PDP 33.5%, the median DCR 2.5 cps, the timing jitter 88 ps, and the crosstalk probability is 3.57%, while the afterpulsing probability is 0.21%. Finally, we verified the feasibility of the proposed technique towards compact multi-megapixel 3D-stacked SPAD arrays.

Angular momentum transfer from photon polarization to an electron spin in a gate-defined quantum dot.

Gate-defined quantum dots (QDs) are such a highly-tunable quantum system in which single spins can be electrically coupled, manipulated, and measured. However, the spins in gate-defined QDs are lacking its interface to free-space photons. Here, we verify that a circularly-polarized single photon can excite a single electron spin via the transfer of angular momentum, measured using Pauli spin blockade (PSB) in a double QD. We monitor the inter-dot charge tunneling which only occur when the photo-electron spin in one QD is anti-parallel to the electron spin in the other. This allows us to detect single photo-electrons in the spin-up/down basis using PSB. The photon polarization dependence of the excited spin state was finally confirmed for the heavy-hole exciton excitation. The angular momentum transfer observed here is a fundamental step providing a route to instant injection of spins, distributing single spin information, and possibly towards extending quantum communication.

An Image Signal Accumulation Multi-Collection-Gate Image Sensor Operating at 25 Mfps with 32 × 32 Pixels and 1220 In-Pixel Frame Memory.

The paper presents an ultra-high-speed image sensor for motion pictures of reproducible events emitting very weak light. The sensor is backside-illuminated. Each pixel is equipped with multiple collection gates (MCG) at the center of the front side. Each collection gate is connected to an in-pixel large memory unit, which can accumulate image signals captured by repetitive imaging. The combination of the backside illumination, image signal accumulation, and slow readout from the in-pixel signal storage after an image capturing operation offers a very high sensitivity. Pipeline signal transfer from the the multiple collection gates (MCG) to the in-pixel memory units enables the sensor to achieve a large frame count and a very high frame rate at the same time. A test sensor was fabricated with a pixel count of 32 × 32 pixels. Each pixel is equipped with four collection gates, each connected to a memory unit with 305 elements; thus, with a total frame count of 1220 (305 × 4) frames. The test camera achieved 25 Mfps, while the sensor was designed to operate at 50 Mfps.

Comparison of the measurement properties of the Functional Independence and Difficulty Scale with the Barthel Index in community-dwelling elderly people in Japan.

BACKGROUND: The new Functional Independence and Difficulty Scale (FIDS) is a tool for assessing the performance of basic activities of daily living (BADL). Because many BADL measures already exist, it is important to know whether FIDS can offer added benefit over the existing measures. AIMS: This study compared measurement properties between the FIDS and a representative BADL assessment tool, the Barthel Index (BI). METHODS: Recruitment of the participants was done on the basis of convenience sampling. Participants were community-dwelling elderly Japanese subjects (n = 314; age ≥65 years) divided into a healthy elderly group [n = 225; subjects not using long-term care insurance (LTCI) services] and frail elderly group (n = 89; subjects using LTCI services). For each group, ceiling effect (percent participation with the maximum score) was calculated, and it was compared between the two scales. Associations between the FIDS, BI and Medical Outcomes Study Short Form 8 Health Survey (SF-8) were evaluated by Spearman correlation coefficient and partial correlations. Partial correlations coefficients to SF-8 were compared between the two scales. RESULTS: FIDS showed a relatively small ceiling effect compared to the BI. Compared to the BI, FIDS showed a significant positive partial correlation with the broader aspect of the SF-8 subscales, but the strength of correlation between FIDS and SF-8 was weak to negligible. CONCLUSIONS: The FIDS might be less affected by ceiling effect than the BI. Additional studies using a sufficient number of probability samples are needed to clarify whether FIDS has any benefit over BI in terms of correlations with the SF-8.

A stem-less probe using spontaneous pairing between Cy3 and quencher for RNA detection.

We herein report a stem-less probe for the detection of RNA that depends on pairing between Cy3 and nitro methyl red. In our design, two Cy3 residues and two nitro methyl red residues were introduced into an oligonucleotide. In the absence of the target, these dyes formed a complex, and emission of Cy3 was efficiently quenched. Hybridization with the target RNA disrupted this interaction and resulted in Cy3 emission. Under optimized conditions, the signal to background ratio was as high as 180. We demonstrated specific detection of target RNA in cells using a wash-free FISH protocol.

Sustained distribution of aerosolized PEGylated liposomes in epithelial lining fluids on alveolar surfaces.

The distribution characteristics of aerosolized PEGylated liposomes in alveolar epithelial lining fluid (ELF) were examined in rats, and the ensuing mechanisms were investigated in the in vitro uptake and protein adsorption experiments. Nonmodified or PEGylated liposomes (particle size 100 nm) were aerosolized into rat lungs. PEGylated liposomes were distributed more sustainably in ELFs than nonmodified liposomes. Furthermore, the uptake of PEGylated liposomes by alveolar macrophages (AMs) was less than that of nonmodified liposomes. In further in vitro uptake experiments, nonmodified and PEGylated liposomes were opsonized with rat ELF components and then added to NR8383 cells as cultured rat AMs. The uptake of opsonized PEGylated liposomes by NR8383 cells was lower than that of opsonized nonmodified liposomes. Moreover, the protein absorption levels in opsonized PEGylated liposomes were lower than those in opsonized nonmodified liposomes. These findings suggest that sustained distributions of aerosolized PEGylated liposomes in ELFs reflect evasion of liposomal opsonization with surfactant proteins and consequent reductions in uptake by AMs. These data indicate the potential of PEGylated liposomes as aerosol-based drug delivery system that target ELF for the treatment of respiratory diseases.

Effect of Physiological Changes in the Skin on Systemic Absorption of Tacrolimus Following Topical Application in Rats.

Tacrolimus (TL) ointment is a topical treatment for atopic dermatitis, a disease that exhibits various skin conditions. The effect of skin pathologies on the systemic absorption of TL and related side effects remains unknown. This study aimed to investigate factors affecting the cutaneous absorption of TL. We prepared various skin models in hairless rats by tape stripping, injection of prophlogistic material solution (PMS), and continuous subcutaneous adrenaline (Adr) infusion. In vivo absorption studies were conducted, with measurements of transepidermal water loss (TEWL) and skin blood flow as physiological parameters. Very little TL absorption was observed through intact skin. Greater TL absorption was noted in skins with high TEWL values and fully stripped skin with PMS injections. In contrast, Adr infusion, which reduced skin blood flow, resulted in decreased TL absorption through fully stripped skin. Combined use of TL and Adr on skin with PMS injections resulted in suppression of TL absorption. Our results revealed that TL absorption following topical application is affected by alterations in the skin barrier, blood flow, and vascular permeability. We propose an administration plan for TL in a flowchart as a means of preventing systemic side effects.

Molecular design of Cy3 derivative for highly sensitive in-stem molecular beacon and its application to the wash-free FISH.

We herein describe a novel in-stem molecular beacon (ISMB) containing multiple Cy3-quencher pairs on d-threoninol scaffolds in the stem region. The designed Cy3 derivative was not significantly quenched by the adjacent nucleobases, self-quenching of the fluorophore was minimal, and the fluorophore did not severely destabilize the duplex. Using newly designed Cy3, we synthesized ISMBs containing two Cy3 moieties. The signal to background ratio of the ISMB containing two Cy3 moieties was above 100, whereas that with one Cy3 was 30. A Cy3-derivative containing ISMB used in a fluorescence in situ hybridization (FISH) detected endogenous ß-actin mRNA in fixed cells without need for washing procedures.

Involvement of intestinal permeability in the oral absorption of clarithromycin and telithromycin.

The involvement of intestinal permeability in the oral absorption of clarithromycin (CAM), a macrolide antibiotic, and telithromycin (TEL), a ketolide antibiotic, in the presence of efflux transporters was examined. In order independently to examine the intestinal and hepatic availability, CAM and TEL (10 mg/kg) were administered orally, intraportally and intravenously to rats. The intestinal and hepatic availability was calculated from the area under the plasma concentration-time curve (AUC) after administration of CAM and TEL via different routes. The intestinal availabilities of CAM and TEL were lower than their hepatic availabilities. The intestinal availability after oral administration of CAM and TEL increased by 1.3- and 1.6-fold, respectively, after concomitant oral administration of verapamil as a P-glycoprotein (P-gp) inhibitor. Further, an in vitro transport experiment was performed using Caco-2 cell monolayers as a model of intestinal epithelial cells. The apical-to-basolateral transport of CAM and TEL through the Caco-2 cell monolayers was lower than their basolateral-to-apical transport. Verapamil and bromosulfophthalein as a multidrug resistance-associated proteins (MRPs) inhibitor significantly increased the apical-to-basolateral transport of CAM and TEL. Thus, the results suggest that oral absorption of CAM and TEL is dependent on intestinal permeability that may be limited by P-gp and MRPs on the intestinal epithelial cells.

Subcellular distribution of azithromycin and clarithromycin in rat alveolar macrophages (NR8383) in vitro.

Azithromycin (AZM), a 15-membered ring macrolide antimicrobial agent, has an antibacterial spectrum that includes intracellular parasitic pathogens that survive or intracellularly multiply in alveolar macrophages (AMs). The subcellular distribution of AZM in AMs was evaluated in vitro in comparison with clarithromycin (CAM). AZM and CAM (50 µM) were applied to the NR8383 cells, used as an in vitro model of AMs, followed by incubation at 37°C or 4°C. The total amount of AZM in cells and subcellular distribution (cell fractionation) was determined after incubation. High level of AZM accumulation was observed in the NR8383 cells at 37°C, and the equilibrium intracellular to extracellular concentration ratio (I/E ratio) was approximately 680, which was remarkably higher than that of CAM (equilibrium I/E ratio=28). The intracellular accumulation of AZM and CAM was temperature dependent. In addition, AZM distributed to the granules fraction including organelles and soluble fraction including cytosol in the NR8383 cells, whereas CAM mainly distributed in soluble fraction. The amount of AZM in the granules fraction was markedly reduced in the presence of ammonium chloride for increase in intracellular pH. These results indicate that AZM is distributed in acidic compartment in AMs. This study suggests that high AZM accumulation in the NR8383 cells is due to the trapping and/or binding in acidic organelles, such as lysosomes.

[Designs of optimized microbial therapy systems of respiratory infections].

Several respiratory infections are frequently induced by pathogenic microorganisms in lung epithelial lining fluid (ELF) and alveolar macrophages (AM). Then, two studies concerning designs of antimicrobial therapy systems of respiratory infections were carried out; one was the distribution mechanisms of three macrolide and ketolide antibiotics, clarithromycin (CAM), azithromycin (AZM) and telithromycin (TEL) in plasma, ELF and AM, and the other was the efficient drug delivery to AM by pulmonary administration of fluoroquinolone antibiotic, a ciprofloxacin (CPFX) incorporated into liposomes (CPFX-liposome). In the first study, the areas under drug concentration-time curves (AUCs) in ELF following oral administration of three macrolide and ketolide antibiotics to rats were significantly higher than AUCs in plasma, furthermore AUCs in AM significantly higher than AUCs in ELF. The high distribution of these antibiotics to the respiratory infection site is due to the transport from blood to ELF via MDR1 in lung epithelial cells as well as the uptake by AM. These antibiotics were taken up by AM via active transport system and the trapping in organelles. In the second study, drug delivery efficacy of CPFX-liposome to AM was particle size-dependent over the 100-1000 nm and then become constant at over 1000 nm by pulmonary aerosolization to rats. This result indicates that the most effective size is 1000 nm. Furthermore, the drug delivery efficacy of mannosylated CPFX-liposome (particle size: 1000 nm) was highly delivered to AM and antibacterial effects were significantly higher than those of unmodified CPFX-liposome. This review provides useful findings for microbial therapy systems of respiratory infections.

Aerosol-based efficient delivery of azithromycin to alveolar macrophages for treatment of respiratory infections.

The efficacy of aerosol-based delivery of azithromycin (AZM) for the treatment of respiratory infections caused by pathogenic microorganisms infected in alveolar macrophages (AMs) was evaluated by comparison with oral administration. The aerosol formulation of AZM (0.2 mg/kg) was administered to rat lungs using a Liquid MicroSprayer(®). The oral formulation of AZM (50 mg/kg) was used for comparison. Time-courses of concentrations of AZM in AMs following administration were obtained, and then the therapeutic availability (TA) was calculated. In addition, the area under the concentrations of AZM in AMs - time curve/minimum inhibitory concentration at which 90% of isolates ratio (AUC/MIC90) were calculated to estimate the antibacterial effects in AMs. The TA of AZM in AMs following administration of aerosol formulation was markedly greater than that following administration of oral formulation. In addition, the AUC/MIC90 of AZM in AMs was markedly higher than the effective values. This indicates that the aerosol formulation could be useful for the treatment of respiratory infections caused by pathogenic microorganisms infected in AMs. This study suggests that aerosolized AZM is an effective pulmonary drug delivery system for the treatment of respiratory infections.

Myoepithelial carcinoma of the breast with focal rhabdoid features.

Myoepithelial carcinoma of the breast is extremely rare and only 33 cases have been reported in the English literature. Herein, we report a case of myoepithelial carcinoma of the breast with focal rhabdoid features. The patient was a 67-year-old woman, who presented with a lump of the left breast that rapidly grew to 3 cm in diameter within 3 months. Lumpectomy revealed a solid and whitish colored tumor, which was composed mainly of elongated spindle-shaped cells with mild atypia, focal necrosis, and infiltrative margin. In a small area of the lesion, ovoid tumor cells exhibited eccentric nuclei with centrally located nucleoli and plump cytoplasm including round eosinophilic inclusions, resembling a rhabdoid tumor. Immunohistochemically, both types of tumor cells exhibited a myoepithelial phenotype. MIB-1 index was 30%. The cytoplasmic inclusion of the ovoid cells exhibited immunopositivity for both vimentin and cytokeratin. From these findings, this tumor was diagnosed as a myoepithelial carcinoma with focal rhabdoid features. Although rhabdoid features have been reported in some types of malignant and benign tumors, this is the first report of such features in myoepithelial carcinoma of the breast.

Enantioselective uptake of fexofenadine by Caco-2 cells as model intestinal epithelial cells.

OBJECTIVES: Fexofenadine contains a chiral carbon in its chemical structure and is orally administered as a racemic mixture. This study evaluated the selective uptake of fexofenadine enantiomers by Caco-2 cells as a model of intestinal epithelial cells. METHODS: R(+)-fexofenadine or S(-)-fexofenadine was applied to Caco-2 cells, followed by incubation. After incubation, the amounts of fexofenadine enantiomers in cells were determined. The kinetic parameters for the uptake of fexofenadine enantiomers by Caco-2 cells were estimated using the Michaelis-Menten equation. KEY FINDINGS: The transporter-mediated uptake rate of R(+)-fexofenadine was 1.7-fold higher than that of S(-)-fexofenadine. The difference in transporter-mediated R(+)-fexofenadine and S(-)-fexofenadine uptake was completely diminished under ATP-depleted conditions and in the presence of organic anion transporter peptide (OATP) inhibitors. Also, a Dixon plot showed that each fexofenadine enantiomer was competitively inhibited by the other enantiomer. The ratio of R(+)-fexofenadine uptake to S(-)-fexofenadine uptake in the case of a racemic mixture was higher than that in the case of a single enantiomer. CONCLUSION: This study suggested that the selective absorption of fexofenadine enantiomers by intestinal epithelial cells might have been due to the selective uptake mediated by OATPs and that the difference in intestinal absorption was enhanced with a racemic mixture.

Aerosol-based efficient delivery of clarithromycin, a macrolide antimicrobial agent, to lung epithelial lining fluid and alveolar macrophages for treatment of respiratory infections.

BACKGROUND: Macrolide antimicrobial agents are generally given by the oral route for the treatment of respiratory infections caused by pathogenic microorganisms infected in lung epithelial lining fluid (ELF) and alveolar macrophages (AMs). However, because macrolides distribute to many different tissues via the blood after oral administration, systemic side effects are frequently induced. In contrast with oral administration, aerosolization may be an efficient method for delivering macrolides directly to ELF and AMs. In this study, the efficacy of aerosol-based delivery of clarithromycin (CAM), as a model macrolide, for the treatment of respiratory infections was evaluated by comparison with oral administration. METHOD: The aerosol formulation of CAM (0.2 mg/kg) was administered to rat lungs using a Liquid MicroSprayer(®). The oral formulation of CAM (50 mg/kg) was used for comparison. Time courses of concentrations of CAM in ELF and AMs following administration were obtained, and then the bioavailability (BA) was calculated. In addition, the area under the concentrations of CAM in ELF and AMs-time curve/minimum inhibitory concentration at which 90% of isolates ratio [area under the curve (AUC/MIC(90))] were calculated to estimate the antibacterial effects in ELF and AMs. RESULTS: The BA of CAM in ELF and AMs following administration of aerosol formulation were markedly greater than that following administration of oral formulation. This indicates that the aerosol formulation is more effective in delivering CAM to ELF and AMs, compared with the oral formulation, despite a low dose. The AUC/MIC(90) of CAM in ELF and AMs were markedly higher than the effective values. This indicates that the aerosol formulation could be useful for the treatment of respiratory infections caused by pathogenic microorganisms infected in ELF and AMs. CONCLUSIONS: This study suggests that aerosol formulation of macrolides is an effective pulmonary drug delivery system for the treatment of respiratory infections.

Distribution characteristics of clarithromycin and azithromycin, macrolide antimicrobial agents used for treatment of respiratory infections, in lung epithelial lining fluid and alveolar macrophages.

The distribution characteristics of clarithromycin (CAM) and azithromycin (AZM), macrolide antimicrobial agents, in lung epithelial lining fluid (ELF) and alveolar macrophages (AMs) were evaluated. In the in vivo animal experiments, the time-courses of the concentrations of CAM and AZM in ELF and AMs following oral administration (50 mg/kg) to rats were markedly higher than those in plasma, and the area under the drug concentration-time curve (AUC) ratios of ELF/plasma of CAM and AZM were 12 and 2.2, and the AUC ratios of AMs/ELF were 37 and 291, respectively. In the in vitro transport experiments, the basolateral-to-apical transport of CAM and AZM through model lung epithelial cell (Calu-3) monolayers were greater than the apical-to-basolateral transport. MDR1 substrates reduced the basolateral-to-apical transport of CAM and AZM. In the in vitro uptake experiments, the intracellular concentrations of CAM and AZM in cultured AMs (NR8383) were greater than the extracellular concentrations. The uptake of CAM and AZM by NR8383 was inhibited by ATP depletors. These data suggest that the high distribution of CAM and AZM to AMs is due to the sustained distribution to ELF via MDR1 as well as the high uptake by the AMs themselves via active transport mechanisms.

[Effects of sperminated pullulans on the pulmonary absorption of insulin].

Sperminated pullulans (SP) having different molecular weights (MWs) were prepared, and the enhancing effect on the pulmonary absorption of insulin in rats was examined. SP acted as enhancers of insulin absorption when a 0.1% solution was applied with insulin simultaneously and their enhancing effects depended on the MW of the SP; the same solutions exhibited low toxicity in the in vivo LDH leaching test. In the in vitro experiments using Calu-3 cells, tight junction-opening effects and a toxic effect of SP in the MTT assay were observed at lower concentrations compared with the in vivo experiments. A mucus layer might interfere with the interaction between SP and the cell surface and might suppress both these effects and toxicity. SP having a high MW will be useful for preparing safe and efficient formulations of peptide and protein drugs. The change in the localization of the tight junction proteins may be related to the permeation-enhancing mechanism of SP.