Detection of Breast Cancer-Specific Extracellular Vesicles with Fiber-Optic SPR Biosensor.

Extracellular vesicles (EVs) have attracted great attention as potential biomarkers for cancer diagnostics. Although several technologies have been developed for EV detection, many of them are still not applicable to clinical settings as they rely on complex EV isolation processes, while lacking sensitivity, specificity or standardization. To solve this problem, we have developed a sensitive breast cancer-specific EV detection bioassay directly in blood plasma using a fiber-optic surface plasmon resonance (FO-SPR) biosensor, previously calibrated with recombinant EVs. First, we established a sandwich bioassay to detect SK-BR-3 EVs by functionalizing the FO-SPR probes with anti-HER2 antibodies. A calibration curve was built using an anti-HER2/Banti-CD9 combination, resulting in an LOD of 2.1 × 107 particles/mL in buffer and 7 × 108 particles/mL in blood plasma. Next, we investigated the potential of the bioassay to detect MCF7 EVs in blood plasma using an anti-EpCAM/Banti-mix combination, obtaining an LOD of 1.1 × 10 8 particles/mL. Finally, the specificity of the bioassay was proven by the absence of signal when testing plasma samples from 10 healthy people unknown to be diagnosed with breast cancer. The remarkable sensitivity and specificity of the developed sandwich bioassay together with the advantages of the standardized FO-SPR biosensor highlight outstanding potential for the future of EV analysis.

Minimization of Fresnel reflection by anti-reflection fiber Bragg grating inscribed at the fiber ends.

In this paper, we proposed and numerically demonstrated a novel method to effectively minimize Fresnel reflection from a perpendicularly cleaved fiber using a uniform fiber Bragg grating (FBG) inscribed at the fiber end. By matching the reflectivity of an in-line FBG with the reflectivity caused by the glass-air boundary, the FBG acts as a virtual boundary, which provides destructive interference and suppresses Fresnel reflection. We achieved an anti-reflection FBG with a return loss of more than 80 dB by ensuring that the product of the index contrast and grating period number is almost constant, with a value of 0.2695.

Quantitative Prediction of CYP3A4 Induction: Impact of Measured, Free, and Intracellular Perpetrator Concentrations from Human Hepatocyte Induction Studies on Drug-Drug Interaction Predictions.

Typically, concentration-response curves are based upon nominal inducer concentrations for in-vitro-to-in-vivo extrapolation of CYP3A4 induction. The limitation of this practice is that it assumes the hepatocyte culture model is a static system. We assessed whether correcting for: 1) changes in perpetrator concentration in the induction medium during the incubation period, 2) perpetrator binding to proteins in the induction medium, and 3) nonspecific binding of perpetrator can improve the accuracy of CYP3A4 induction predictions. Of the seven compounds used in this evaluation, significant parent loss and nonspecific binding were observed for rifampicin (29.3-38.3%), pioglitazone (64.3-78.6%), and rosiglitazone (57.1-75.5%). As a result, the free measured EC50 values (EC50u) of pioglitazone, rosiglitazone, and rifampicin were significantly lower than the nominal EC50 values. In general, the accuracy of the induction predictions, using multiple static models, improved when corrections were made for measured medium concentrations, medium protein binding, and nonspecific binding of the perpetrator, as evidenced by 18-29% reductions in the root mean square error. The relative induction score model performed better than the basic static and mechanistic static models, resulting in lower prediction error and no false-positive or false-negative predictions. However, even when the EC50u value was used, the induction prediction for bosentan, which is a substrate of organic anion transporter proteins, was overpredicted by approximately 2-fold. Accounting for the ratio of unbound intracellular concentrations to unbound medium concentrations (Kpuu,in vitro) (0.5-7.5) and the predicted multiple-dose Kpuu,in vivo (0.6) for bosentan resulted in induction predictions within 35% of the observed interaction.

Application of Micropatterned Cocultured Hepatocytes to Evaluate the Inductive Potential and Degradation Rate of Major Xenobiotic Metabolizing Enzymes.

Long-term coculture models of hepatocytes are promising tools to study drug transport, clearance, and hepatoxicity. In this report we compare the basal expression of drug disposition genes and the inductive response of prototypical inducers (rifampin, phenobarbital, phenytoin) in hepatocyte two-dimensional monocultures and the long-term coculture model (HepatoPac). All the inducers used in the study increased the expression and activity of CYP3A4, CYP2B6 and CYP2C enzymes in the HepatoPac cultures. The coculture model showed a consistent and higher induction of CYP2C enzymes compared with the monocultures. The EC50 of rifampin for CYP3A4 and CYP2C9 was up to 10-fold lower in HepatoPac than the monocultures. The EC50 of rifampin calculated from the clinical drug interaction studies correlated well with the EC50 observed in the HepatoPac cultures. Owing to the long-term stability of the HepatoPac cultures, we were able to directly measure a half-life (t1/2) for both CYP3A4 and CYP2B6 using the depletion kinetics of mRNA and functional activity. The t1/2 for CYP3A4 mRNA was 26 hours and that for the functional protein was 49 hours. The t1/2 of CYP2B6 was 38 hours (mRNA) and 68 hours (activity), which is longer than CYP3A4 and shows the differential turnover of these two proteins. This is the first study to our knowledge to report the turnover rate of CYP2B6 in human hepatocytes. The data presented here demonstrate that the HepatoPac cultures have the potential to be used in long-term culture to mimic complex clinical scenarios.

Evaluation of the Interplay between Uptake Transport and CYP3A4 Induction in Micropatterned Cocultured Hepatocytes.

Previously we assessed the inductive response of prototypical inducers in hepatocyte monocultures and the long-term coculture model HepatoPac using cryopreserved hepatocytes from the same donors. We noted that the rifampicin EC50 generated using the HepatoPac model corresponded better to the EC50 based on clinical data compared with data generated in the monoculture system. We postulated that there may be differences in the functioning of uptake transporters between the two systems that may have led to the EC50 difference. In this study, we characterized the functional activity of multiple uptake transporters in the two systems using cryopreserved hepatocytes from the same donors. Our data suggest that uptake transporter activity is higher in HepatoPac compared with the monoculture system. As a follow up to this study, we measured the intracellular concentrations of rifampicin and bosentan, which are known substrates of uptake transporters; we observed significantly higher intracellular concentrations of both compounds in HepatoPac relative to the monoculture system. This finding equated to lower cytochrome P450 isoform 3A4 (CYP3A4) EC50 values in the HepatoPac system compared with the monoculture system for both mRNA and activity. In parallel, no significant EC50 shift was observed for carbamazepine and phenytoin, which are not known to be substrates of uptake transporters. Our data suggest that next generation liver models such as HepatoPac may be a useful in vitro tool to quantitatively predict drug-drug interactions when it is known that the perpetrator is also a substrate of drug transporters.

VX-509 (Decernotinib)-Mediated CYP3A Time-Dependent Inhibition: An Aldehyde Oxidase Metabolite as a Perpetrator of Drug-Drug Interactions.

(R)-2-((2-(1H-pyrrolo[2,3-b]pyridin-3-yl)pyrimidin-4-yl)amino)-2-methyl-N-(2,2,2-trifluoroethyl)butanamide (VX-509, decernotinib) is an oral Janus kinase 3 inhibitor that has been studied in patients with rheumatoid arthritis. Patients with rheumatoid arthritis often receive multiple medications, such as statins and steroids, to manage the signs and symptoms of comorbidities, which increases the chances of drug-drug interactions (DDIs). Mechanism-based inhibition is a subset of time-dependent inhibition (TDI) and occurs when a molecule forms a reactive metabolite which irreversibly binds and inactivates drug-metabolizing enzymes, potentially increasing the systemic load to toxic concentrations. Traditionally, perpetrating compounds are screened using human liver microsomes (HLMs); however, this system may be inadequate when the precipitant is activated by a non-cytochrome P450 (P450)-mediated pathway. Even though studies assessing competitive inhibition and TDI using HLM suggested a low risk for CYP3A4-mediated DDI in the clinic, VX-509 increased the area under the curve of midazolam, atorvastatin, and methyl-prednisolone by approximately 12.0-, 2.7-, and 4.3-fold, respectively. Metabolite identification studies using human liver cytosol indicated that VX-509 is converted to an oxidative metabolite, which is the perpetrator of the DDIs observed in the clinic. As opposed to HLM, hepatocytes contain the full complement of drug-metabolizing enzymes and transporters and can be used to assess TDI arising from non-P450-mediated metabolic pathways. In the current study, we highlight the role of aldehyde oxidase in the formation of the hydroxyl-metabolite of VX-509, which is involved in clinically significant TDI-based DDIs and represents an additional example in which a system-dependent prediction of TDI would be evident.

1590-nm-pumped passively Q-switched thulium all-fiber laser at 1900 nm.

We propose and demonstrate a passively Q-switched 1900-nm thulium all-fiber laser using the mode-field-area mismatch method. A thulium fiber laser was core-pumped at 1590 nm and saturable-absorber Q-switched at 1900 nm through the use of a thulium saturable absorber fiber that had a relatively smaller mode field area than the gain medium. Sequential pulsing with a pulse energy of 12 µJ and a pulse duration of 160 ns was obtained. The pulse repetition rate was increased linearly with the applied pump power. With a pump power of 4.5 W, an average output power of 0.61 W and a pulse repetition rate of 50.7 kHz were achieved.

Passively cascade-pulsed erbium ZBLAN all-fiber laser.

We propose and numerically demonstrate a cascade pulsing mechanism in a CW-pumped Er³âº:ZBLAN all-fiber laser system. In the design, the laser was pumped at 980 nm and passively Q-switched at 1.6 µm. The Q-switched resonance reduced the population on 4/13/2 of the erbium gain fiber, thereby creating a population inversion between the levels of 4/11/2 and 4/13/2, and instantly inducing an intense gain-switched pulse at 2.7 µm. Sequential 2.7-µm single-mode pulsing with a pulse energy of 170 µJ and a peak power of 6 kW was achieved with an absorbed pump power of 0.65 W.

Lensless intracavity focusing in a passively Q-switched all-fiber laser using the mode-field-area mismatch.

Intense lensless intracavity focusing in a saturable absorber Q-switched all-fiber laser resonator by use of loss arrangement and mode-field-area mismatch between the fibers is investigated for the first time. The intracavity power distribution was related to the locations and values of the cavity losses as the saturable absorption loss, the reflection loss of the output coupler, and the splicing loss between the gain fiber and the absorber fiber. With a mode-field-area mismatch and a reduced splicing loss with the gain fiber, a power density in the absorber fiber was achieved that was 11.9 times higher than that in the gain fiber.

Saturable absorber Q- and gain-switched all-Yb3+ all-fiber laser at 976 and 1064 nm.

We demonstrate a novel passively pulsed all-Yb3+ all-fiber laser pumped by a continuous-wave 915-nm pump laser diode. The laser was saturable absorber Q-switched at 976 nm and gain-switched at 1064 nm, using the method of mode-field-area mismatch. With a pump power of 105 mW, the laser iteratively produced a 976-nm pulse with an energy of 2.8 µJ and a duration of 280 ns, followed by a 1064-nm pulse with 1.1 µJ and a 430-ns duration at a repetition rate of 9 kHz. A set of rate equations was established to simulate the self-balancing mechanism and the correlation between the Q- and gain-switched photon numbers and the populations of the gain and absorber fibers.

All-fiber passively Q-switched erbium laser using mismatch of mode field areas and a saturable-amplifier pump switch.

We propose and demonstrate an all-fiber self-Q-switched erbium laser system that is saturable-absorber Q switched by the mismatch of the mode-field areas in the resonator and stabilized with a saturable-amplifier pump switch. Sequential pulses with a pulse energy of 8-6 microJ and a pulse duration of 80-320 ns, corresponding to a pulse repetition rate of 0.25-1 kHz, were obtained using a cw 980 nm laser-diode pump. A peak pulse power of near 100 W was achieved.

Evaluating LC-MS/MS To Measure Accumulation of Compounds within Bacteria.

A general method for determining bacterial uptake of compounds independent of antibacterial activity would be a valuable tool in antibacterial drug discovery. LC-MS/MS assays have been described, but it has not been shown whether the data can be used directly to inform medicinal chemistry. We describe the evaluation of an LC-MS/MS assay measuring association of compounds with bacteria, using a set of over a hundred compounds (inhibitors of NAD-dependent DNA ligase, LigA) for which in vitro potency and antibacterial activity had been determined. All compounds were active against an efflux-deficient strain of Escherichia coli with reduced LigA activity ( E. coli ligA251 Δ tolC). Testing a single compound concentration and incubation time, we found that, for equipotent compounds, LC-MS/MS values were not predictive of antibacterial activity. This indicates that measured bacteria-associated compound was not necessarily exposed to the target enzyme. Our data suggest that, while exclusion from bacteria is a major reason for poor antibacterial activity of potent compounds, the distribution of compound within the bacterial cell may also be a problem. The relative importance of these factors is likely to vary from one chemical series to another. Our observations provide directions for further study of this difficult issue.

Minimizing matrix effects while preserving throughput in LC-MS/MS bioanalysis.

BACKGROUND: Phospholipids are known to cause matrix effects in LC-MS analysis and are not effectively removed by one of the most common method of sample preparation: organic solvent protein precipitation. The objective of this research is to minimize phospholipid interferences chromatographically. RESULTS: In this article we examine several chromatographic approaches and highlight the method we developed that allows for the rapid gradient separation of model drug molecules from phospholipids. CONCLUSION: The new approach (which utilizes a mixture of methanol and acetonitrile as the organic mobile phase on a 2.1 × 20 mm C18 column) minimized phospholipids-related matrix effects in the analysis of plasma samples prepared by protein precipitation and is suitable for high-throughput bioanalysis in drug discovery.

In vitro and in vivo isotope effects with hepatitis C protease inhibitors: enhanced plasma exposure of deuterated telaprevir versus telaprevir in rats.

Telaprevir 2 (VX-950), an inhibitor of the hepatitis C virus (HCV(a)) NS3-4A protease, is in phase 3 clinical trials. One of the major metabolites of 2 is its P1-(R)-diastereoisomer, 3 (VRT-394), containing an inversion at the chiral center next to the alpha-ketoamide on exchange of a proton with solvent. Compound 3 is approximately 30-fold less active against HCV protease. In an attempt to suppress the epimerization of 2 without losing activity against the HCV protease, the proton at that chiral site was replaced with deuterium (d). The compound 1 (d-telaprevir) is as efficacious as 2 in in vitro inhibition of protease activity and viral replication (replicon) assays. The kinetics of in vitro stability of 1 and 2 in buffered pH solutions and plasma samples, including human plasma, suggest that 1 is significantly more stable than 2. Oral administration (10 mg/kg) in rats resulted in a approximately 13% increase of AUC for 1.