Bright and durable scintillation from colloidal quantum shells.

Efficient, fast, and robust scintillators for ionizing radiation detection are crucial in various fields, including medical diagnostics, defense, and particle physics. However, traditional scintillator technologies face challenges in simultaneously achieving optimal performance and high-speed operation. Herein we introduce colloidal quantum shell heterostructures as X-ray and electron scintillators, combining efficiency, speed, and durability. Quantum shells exhibit light yields up to 70,000 photons MeV-1 at room temperature, enabled by their high multiexciton radiative efficiency thanks to long Auger-Meitner lifetimes (>10 ns). Radioluminescence is fast, with lifetimes of 2.5 ns and sub-100 ps rise times. Additionally, quantum shells do not exhibit afterglow and maintain stable scintillation even under high X-ray doses (>109 Gy). Furthermore, we showcase quantum shells for X-ray imaging achieving a spatial resolution as high as 28 line pairs per millimeter. Overall, efficient, fast, and durable scintillation make quantum shells appealing in applications ranging from ultrafast radiation detection to high-resolution imaging.

Large two-photon cross sections and low-threshold multiphoton lasing of CdS/CdSe/CdS quantum shells.

Colloidal quantum shells are spherical semiconductor quantum wells, which have shown strong promise as optical materials, particularly in classes of experiments requiring multiple excitons. The two-photon properties of CdS/CdSe/CdS quantum shell samples are studied here to demonstrate large non-linear absorption cross-sections while retaining advantageous multiexciton physics conferred by the geometrical structure. The quantum shells have large two-phonon cross sections (0.4-7.9 × 106 GM), which highlights their potential use in upconversion imaging in which large per particle two-photon absorption is critical. Time-resolved measurements confirmed that the quantum shells have long biexciton lifetime (>10 ns in the largest core samples reported here) and large gain bandwidth (>300 meV). The combination of these attributes with large two-photon cross sections makes the CdS/CdSe/CdS quantum shells excellent gain media for two-photon excitation. With a broad gain bandwidth and long gain lifetime, quantum shell solids support multimodal amplified spontaneous emission from excitons, biexcitons, and higher excited states. Thresholds for amplified spontaneous emission and lasing, which are as low as 1 mJ cm-2, are comparable to, or lower than, the thresholds reported for other colloidal materials.

Quantification of human serum insulin concentrations in clinical pharmacokinetic or bioequivalence studies: what defines the "best method"?

BACKGROUND: Historically, quantitative clinical diagnostic assays (QCDAs) have not been accepted for use in pharmacokinetic or bioequivalence studies because they do not fully comply with the US Food and Drug Administration (FDA) Guidance for Industry: Bioanalytical Method Validation (e.g., full calibration curve not generated with each analytical run). Samples from a bioequivalence study were analysed for insulin and C-peptide concentrations with QCDAs and guidance-conforming radioimmunoassays (RIAs) and the results compared across and within assays. METHODS: Serum samples (n=1913) from study MKC-TI-142 were analysed first using the Roche E170 electrochemiluminescence immunoassay (ECLIA) for insulin concentration and the Immulite 2000 chemiluminescence immunoassay (CLIA) for C-peptide, and then using the corresponding Millipore RIAs. RESULTS: The insulin assays were highly correlated: r2=0.92 excluding samples requiring dilution and R2=0.88 including all samples. There was increasing negative bias of the ECLIA compared with the RIA with increasing insulin, especially with samples that required dilution for the RIA. The ECLIA had significantly fewer below-quantifiable-limit samples, a larger dynamic analysis range without dilution, and tighter agreement within incurred sample reanalysis (ISR) as compared with the RIA. The C-peptide assays showed good agreement but the CLIA method produced ISR results that were in closer agreement with the original values. CONCLUSIONS: The science indicates that the QCDAs are appropriate for the quantification of serum insulin (ECLIA) and C-peptide (CLIA) concentrations in human pharmacokinetic and bioequivalence studies even though the calibration curve is not generated in each analytical run.

Insulin lung deposition and clearance following Technosphere® insulin inhalation powder administration.

PURPOSE: To determine distribution and deposition of Technosphere® Insulin (TI) inhalation powder and the rate of clearance of fumaryl diketopiperazine (FDKP; major component of Technosphere particles) and insulin from the lungs. METHODS: Deposition and distribution of (99m)pertechnetate adsorbed onto TI immediately after administration using the MedTone® inhaler was quantified by gamma-scintigraphy. Clearance from the lungs was studied in a second experiment by serial bronchoalveolar lavage (BAL) after administration of TI inhalation powder and assay of the recovered fluid for FDKP and insulin. RESULTS: Following inhalation, ~60% of radioactivity (adsorbed on TI) emitted from the inhaler was delivered to the lungs; the remainder of the emitted dose was swallowed. Clearance from the lung epithelial lining fluid (ELF) of FDKP and insulin have a half-life of ~1 hour. CONCLUSION: TI inhalation powder administered via the MedTone inhaler was uniformly distributed throughout the lungs; ~40% of the initial cartridge load reached the lungs. Insulin and FDKP are quickly cleared from the lungs, mainly by absorption into the systemic circulation. The terminal clearance half-life from the lung ELF, estimated from sequential BAL fluid measurements for both components, was ~1 hour. Since there is an overnight washout period, the potential for accumulation on chronic administration is minimal.

Selenium for the prevention of cutaneous melanoma.

The role of selenium (Se) supplementation in cancer prevention is controversial; effects often depend on the nutritional status of the subject and on the chemical form in which Se is provided. We used a combination of in vitro and in vivo models to study two unique therapeutic windows for intervention in the process of cutaneous melanomagenisis, and to examine the utility of two different chemical forms of Se for prevention and treatment of melanoma. We studied the effects of Se in vitro on UV-induced oxidative stress in melanocytes, and on apoptosis and cell cycle progression in melanoma cells. In vivo, we used the HGF transgenic mouse model of UV-induced melanoma to demonstrate that topical treatment with l-selenomethionine results in a significant delay in the time required for UV-induced melanoma development, but also increases the rate of growth of those tumors once they appear. In a second mouse model, we found that oral administration of high dose methylseleninic acid significantly decreases the size of human melanoma xenografts. Our findings suggest that modestly elevation of selenium levels in the skin might risk acceleration of growth of incipient tumors. Additionally, certain Se compounds administered at very high doses could have utility for the treatment of fully-malignant tumors or prevention of recurrence.

Pharmacokinetic characterization of the novel pulmonary delivery excipient fumaryl diketopiperazine.

BACKGROUND: Technosphere® [Bis-3,6(4-fumarylaminobutyl)-2,5-diketopiperazine (FDKP)] microparticles, the integral component of the Technosphere inhalation system, deliver drugs to the deep lung and have been used to administer insulin and glucagon-like peptide-1 via inhalation in clinical studies. Three studies were conducted to characterize FDKP pharmacokinetics, including assessments in subjects with diabetic nephropathy (DNP), in subjects with chronic liver disease (CLD), and in healthy subjects. METHODS: An open-label, nonrandomized, two-period, fixed-sequence crossover absorption, distribution, metabolism, and excretion (ADME) study was conducted in six healthy nonsmoking men who received single intravenous and oral doses of [(14)C]FDKP solution, with serial sampling of blood, urine, feces, and expired air. Additionally, two single-dose, open-label, parallel-design studies with 20 mg of inhaled FDKP were conducted in (1) 12 diabetic subjects with normal renal function and 24 DNP subjects and (2) 12 healthy subjects and 21 CLD subjects. RESULTS: In the ADME study, >95% of the intravenous dose and <3% of the oral dose were recovered in urine, with no evidence of metabolism. No significant pharmacokinetic differences were observed between healthy subjects and CLD subjects [geometric mean (% coefficient of variation) area under the curve from time 0 to 480 minutes (AUC(0-480)): 26,710 (34.8) and 31,477 (28.8) ng/ml·min, respectively]. Maximum observed drug concentration (C(max)) and AUC(0-480) were higher in DNP subjects than in subjects with normal renal function [C(max): 159.9 (59.4) ng/ml versus 147.0 (44.3) ng/ml; AUC(0-480): 36,869 (47.2) ng/ml·min versus 30,474 (31.8) ng/ml·min]. None of the differences observed were considered clinically significant. CONCLUSIONS: Fumaryl diketopiperazine is predominantly cleared unchanged by the kidney with essentially no oral bioavailability. Technosphere is a safe delivery vehicle for medications administered via inhalation.