Discovery of oral chemotherapeutic reversal agents for treating multidrug resistance cancer.

The major limitation of cancer treatment is multidrug resistance (MDR), which leads to the inactivation of chemotherapeutic drugs and greater than 90% mortality. To solve this ordeal, we applied ligand-based drug design and bioiosteric replacement strategy from an indazole to a pyrazole ring to discover compounds 27 and 43 with good potential for reversing drug resistance in combination with paclitaxel, and their reversal fold values were 53.2 and 51.0 at 5 µM, respectively, against an MDR cancer cell line (KBvin). Based on the PK profile results, we selected compound 43 with a longer half-life for mechanistic and animal experiments. Combination treatment with compound 43 and paclitaxel-induced apoptosis and enhanced subG1 by decreasing mitochondrial membrane potential in KBvin cells. In addition, 43 also inhibited P-gp function by interfering with ATPase activity. Meanwhile, cotreatment with compound 43 and paclitaxel significantly suppressed tumor growth (TGI = 55.5%) at a dose of 200 mg/kg (PO) in a xenograft model and showed no obvious liver or kidney toxicity by H&E staining. Overall, compound 43 may serve as a safe and effective oral resistance reversal chemotherapeutic agent.

Design and synthesis of pyrazole derivatives against neutrophilic inflammation.

Neutrophils are the most abundant immune cells. However, neutrophil dysregulation leads to acute and chronic inflammation and is involved in various diseases. The aim of this study was to develop anti-inflammatory agents in human neutrophils. A drug screening was conducted on in-house compounds with the potential to inhibit the respiratory burst, which involves the generation of superoxide anions in human neutrophils. Bioisosteric replacement was then applied to design more active derivatives. The most potent inhibitors of superoxide anion generation activity were compounds 58 and 59, which had IC50 values of 13.30 and 9.06 nM, respectively. The inhibitory effects of 58 and 59 were reversed by H89, a PKA inhibitor. PDE selective screening indicated that the best inhibitory effects were PDE4B1 and PDE4D2, and the inhibitory activities were 83% and 85%, respectively, at a 10 µM concentration of 59. The final molecular simulation experiment highlighted the slightly different binding poses of 58 and 59 in the PDE4 active site. An in vivo pharmacokinetic study revealed that the half-life of 59 was approximately 79 min when using intravenous bolus administration. This work introduced a new class structure of PDE4 inhibitors resulting in potent neutrophil inactivation activity, with the aim of contributing to new anti-inflammatory drug discovery.

Durability of single tablet regimen for patients with HIV infection in Southern Taiwan: data from a real-world setting.

BACKGROUND: A single-tablet regimen (STR) has been associated with better drug adherence. However, the durability of different STRs was unknown in the real-world settings. Our aim was to investigate the durability of different initial STR regimens in antiretroviral-naive patients starting STR in southern Taiwan. METHOD: This was a retrospective study of antiretroviral-naive patients that initiated first-line antiretroviral regimens with STRs between May 2016 and December 2017. The primary endpoint was time to virological failure. Secondary endpoints were STR discontinuation due to toxicity/intolerance. Durability was defined as time from the initiation until discontinuation/modification. Kaplan- Meier curves were plotted assessing time to virological suppression, treatment failure and discontinuation for the three STRs and Cox proportional hazards model was used to analyze the factors associated with time to viral suppression, treatment failure or discontinuation. RESULTS: Two hundred and twenty-three patients were included: The median follow-up duration (IQR) was 73.9 (48-101.6) weeks, 25 patients (11%) experienced virological failure; the 48 weeks probability of treatment failure was 22.9% (16/70) for Efavirenz/Emtricitabine/Tenofovir Disoproxil Fumarate (EFV/FTC/TDF), 24.1% (13/54) for Emtricitabine/Rilpivirine/Tenofovir Disoproxil Fumarate (FTC/RPV/TDF) and 24.2% (24/99) for Abacavir/Dolutegravir/Lamivudine (ABC/DTG/3TC) (p=0.16). Fifty-six patients (25%) discontinued their STRs owing to toxicity/intolerance. When compared to EFV/FTC/TDF, treatment with FTC/RPV/TDF (aHR 8.39, CI 1.98-35.58, p = 0.004) and ABC/DTG/3TC (aHR 8.40, CI 2.39-29.54, p=0.001) were more likely to have treatment failure. The predictors for treatment failure included age ≦ 30 years old (aHR 3.73, CI 1.25-11.17, p = 0.018), switch between different STR (aHR 2.3, CI 1.18-4.50, p = 0.001) and free of active syphilis infection (aHR 0.24, CI 0.08-0.73, p = 0.012). The risk factor for treatment discontinuation included younger age ≦ 30 years old (aHR 3.82, CI 1.21-12.37, p = 0.023), treatment with EFV/FTC/TDF (aHR 8.65, CI 2.64-28.39, p < 0.001) and free of active syphilis infection (aHR 0.16, CI 0.04-0.62, p = 0.006). CONCLUSION: Younger age was associated with treatment failure and drug discontinuation. Active syphilis infection s/p treatment was associated with free from treatment failure and discontinuation. This probably driven by the more frequently sexual health education and counseling when patients had syphilis infection. Treatment with ABC/DTG/3TC was associated with higher risk of treatment failure. The STR durability was dependent on the drug toxicity/intolerance, age and syphilis infection.

Outcomes After Switching to BIC/FTC/TAF in Patients with Virological Failure to Protease Inhibitors or Non-Nucleoside Reverse Transcriptase Inhibitors: A Real-World Cohort Study.

PURPOSE: This study evaluated the real-world tolerability and treatment effectiveness of BIC/FTC/TAF in treatment-experienced patients living with HIV-1 in Taiwan, especially in those with viremia at switch. PATIENTS AND METHODS: This was a retrospective cohort study of adult patients in Taiwan with HIV-1 who received BIC/FTC/TAF from between November 2019 and November 2020. The primary endpoint was the rate of viral suppression (plasma HIV RNA load <50 copies/mL) while on BIC/FTC/TAF. The secondary endpoints included durability of treatment, incidence of and reasons for discontinuation of BIC/FTC/TAF, and changes in weight and lipid profiles. RESULTS: A total of 175 patients were switched to BIC/FTC/TAF. Among them, 74 patients (42%) were using INSTI based regimen, 34 patients (19%) NNRTI based regimen and 65 patients (37%) with PI based regimen before switching. Before starting BIC/FTC/TAF, 84.6% of the patients were virologically suppressed, of whom 97.3% maintained suppression while on BIC/FTC/TAF. Overall, 15.4% of the patients (n=27) had a detectable viral load before BIC/FTC/TAF, of whom 81.5% achieved and maintained virologic suppression on BIC/FTC/TAF during follow-up. Only two patients discontinued BIC/FTC/TAF due to adverse events, with rash being the predominant cause. By month 12, the median changes in weight was +4 kg (IQR, -1.8 to 8.2). There were no significant differences from baseline to the end of follow-up in triglycerides (p = 0.07), total cholesterol (p = 0.92), LDL-C (p = 0.12), and HDL-C (p = 0.053). CONCLUSION: The results of this real-world cohort study suggest that switching to BIC/FTC/TAF may be an option to achieve and maintain virological suppression, even in patients with residual viremia at baseline. Our results also demonstrated a low discontinuation rate, a moderate gain in weight, and no significant increases in lipid levels with BIC/FTC/TAF. However, studies with larger sample sizes are warranted to evaluate the clinical implications of our findings.

Model-based simulation to support the extended dosing regimens of atezolizumab.

PURPOSE: The currently recommended dosages of atezolizumab for patients with non-small cell lung cancer (NSCLC) and urothelial carcinoma (UC) is 840 mg every 2 weeks, 1200 mg every 3 weeks (q3w), and 1680 mg every 4 weeks (q4w). However, it has been argued that these dosages may not be optimal. This study aimed to explore the feasibility of extended dosing regimens by population pharmacokinetics (PK) simulations and exposure-response (E-R) relationships. METHODS: All simulations were conducted based on the established population PK and E-R model for safety (i.e., adverse events of special interest, AESI) and efficacy (i.e., objective response rate, ORR) for patients with NSCLC or UC. The PK, AESI, and ORR profiles of the following dosing regimens were simulated: (i) 840 mg q4w, (ii) 1200 mg every 6 weeks (q6w), and (iii) 1680 mg q8w. These regimens were compared with those of the 1200 mg q3w standard regimen. RESULTS: The simulation revealed that the ranking of efficacy for different extended dosing regimens were 1680 mg q8w ≅ 1200 mg q3w ≅ 1200 mg q6w > 840 mg q4w based on the predicted probability of ORR in patients with NSCLC and UC, and this ranking order was similar to that of the safety outcome of the AESI. The minimum serum concentration at steady-state (Cmin,ss) values for all dosing regimens was all higher than the target effective concentration of 6 µg/mL. CONCLUSION: The findings from this simulation suggest that extended dosing regimens are unlikely to significantly impair clinical outcomes and may provide more therapeutic benefits to patients in terms of safety.

Studies of Coumarin Derivatives for Constitutive Androstane Receptor (CAR) Activation.

Constitutive androstane receptor (CAR) activation has found to ameliorate diabetes in animal models. However, no CAR agonists are available clinically. Therefore, a safe and effective CAR activator would be an alternative option. In this study, sixty courmarin derivatives either synthesized or purified from Artemisia capillaris were screened for CAR activation activity. Chemical modifications were on position 5,6,7,8 with mono-, di-, tri-, or tetra-substitutions. Among all the compounds subjected for in vitro CAR activation screening, 6,7-diprenoxycoumarin was the most effective and was selected for further preclinical studies. Chemical modification on the 6 position and unsaturated chains were generally beneficial. Electron-withdrawn groups as well as long unsaturated chains were hazardous to the activity. Mechanism of action studies showed that CAR activation of 6,7-diprenoxycoumarin might be through the inhibition of EGFR signaling and upregulating PP2Ac methylation. To sum up, modification mimicking natural occurring coumarins shed light on CAR studies and the established screening system provides a rapid method for the discovery and development of CAR activators. In addition, one CAR activator, scoparone, did showed anti-diabetes effect in db/db mice without elevation of insulin levels.

Association between ABCB1 Polymorphisms and Antidepressant Treatment Response in Taiwanese Major Depressive Patients.

OBJECTIVE: The multidrug resistance 1 (ABCB1, MDR1) gene, encoding P-glycoprotein, is extensively distributed and expressed in various tissues, such as a blood-brain barrier transporter. P-glycoprotein plays an important role in controlling the passage of substances between the blood and brain. The current study aimed to investigate possible associations of functional ABCB1polymorphisms (C3435T, G2677T and C1236T) with response to antidepressant treatment and serum cortisol levels in Taiwanese patients with major depressive disorder (MDD). METHODS: We recruited 112 MDD patients who were randomized to fluoxetine (n=58, mean dose: 21.4±4.5 mg/day) or venlafaxine (n=54, 80.2±34.7 mg/day) treatment for 6 weeks. The 21-item Hamilton Depression Rating Scale (HDRS) was administered initially and biweekly after treatment, and cortisol levels were assessed initially and after 6-week antidepressant treatment. RESULTS: The initial HDRS scores and the HDRS scores after six weeks of antidepressant treatment were not significantly different among the different genotypes in each polymorphism of ABCB1. The percentage changes of HDRS scores over time were significantly different in the polymorphisms of ABCB1G2677T (p=0.002). MDD patients with the G/G genotype of ABCB1G2677T had a worse antidepressant treatment response. However, the polymorphisms of ABCB1genotypes were not significantly associated with cortisol levels before and after antidepressant treatment in MDD patients. CONCLUSION: The results suggested that the variants of ABCB1may influence the short-term antidepressant response in MDD patients. Further details of the underlying mechanisms of ABCB1in antidepressant treatment remain to be clarified.

Lauroyl/palmitoyl glycol chitosan gels enhance skin delivery of magnesium ascorbyl phosphate.

Palmitoyl glycol chitosan (GCP) hydrogel has been reported as erodible controlled-release systems for the delivery of both hydrophilic and hydrophobic molecules. In this study we prepared lauroyl/palmitoyl glycol chitosan (GCL/GCP) in gel form and evaluated their application for skin delivery of the hydrophilic compound, magnesium ascorbyl phosphate (MAP), which is widely used in cosmetic formulations. Release of MAP from the polymer gels was significantly decreased with increasing concentration of GCL/GCP in the formulations in comparison with glycol chitosan (GC). In both aqueous and 10% ethanol vehicles, MAP flux was increased 1.58- to 3.96-fold of 1% GC from 1% GCL/GCP. Increase in MAP flux was correlated to the increase in GCL/GCP concentration prepared in 10% ethanol vehicle. GCL/GCP, in either water or 10% ethanol vehicles, increased the skin penetration and skin deposition of MAP in comparison with GC, hydroxypropylmethylcellulose, and carbopol, while sustaining its release from the polymer gels. Both the enhancement in skin penetration/deposition and sustained release of MAP were depended on polymer concentration. Also, with increase in polymer concentration, epidermal to dermal drug deposition ratio tended to increase, which will be beneficial to its activity in the epidermis, such as inhibition of tyrosinase and protection from UV damage. These data suggested both GCL and GCP can be applied as delivery vehicles to improve percutaneous absorption of MAP.

Dose-normalization for exposure to mycophenolic acid and the early clinical outcome in patients taking tacrolimus after heart transplantation.

BACKGROUND: The early phase of MPA exposure has rarely been investigated after solid organ transplantation, especially in heart transplantation patients. We evaluated the association between exposure to mycophenolic acid (MPA), a main metabolite of mycophenolate mofetil (MMF), and clinical events within 3 months after heart transplantation. MATERIAL AND METHODS: Trough (C0) and area under the curve (AUC)0-12h levels of MPA and its metabolite, mycophenolic acid glucuronide (MPAG), were determined using high-performance liquid chromatography. Corresponding clinical endpoints included acute rejection or MMF-related adverse events (gastrointestinal symptoms, leucopenia, and anemia). AUC measurements (n=77) were collected from 21 patients. Dose-normalized C0 and AUC0-12h levels were used to evaluate the association between MPA or MPAG exposure and MMF-related adverse events. RESULTS: No acute rejection or mortality occurred during the follow-up period. Twelve patients (57%) developed 13 MMF-related adverse events. The MMF dose was tapered from 2.50 g/day on D1 to 1.55±0.54 g/day on D90. Significantly higher levels of dose-normalized MPA C0 and AUC0-12h were associated with the events than with the absence of the events (C0: 1.04±0.42 vs. 0.84±0.85 µg/mL/g [p=0.047]; AUC0-12h: 20.37±3.21 vs. 14.97±1.13 µg × h/mL/g; [p=0.038]). Conclusions Dose-normalized MPA exposure may protect against MMF toxicity in the early stage after heart transplantation. The MMF dose can be decreased to near 1.5 g/day 3 months post-transplantation without jeopardizing patient safety; a well-planned, tapered MMF regimen should also be considered.

C825T polymorphism of the GNB3 gene on valproate-related metabolic abnormalities in bipolar disorder patients.

BACKGROUND: Valproate (VPA) is a mood stabilizer for treating patients with bipolar disorder (BD). It may cause metabolic abnormalities in certain bipolar patients. However, the genetic factors that influence the susceptibility remain unclear. Genetic polymorphism of the G-protein ß3 subunit (GNB3) is reported to be associated with metabolic phenotypes. In the current study, we investigated the possible associations between the GNB3 variation and VPA-induced metabolic abnormalities. METHODS: Subjects (n = 96) who met the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for BD were recruited from the National Cheng Kung University Hospital. Their metabolic indices were measured. RESULTS: The variation of GNB3 C825T showed an association with higher plasma total cholesterol (P = 0.037), triglyceride (P = 0.014), and leptin (P < 0.001) levels in BD patients treated with VPA. After adjusting for age, sex, types of BDs, and serum concentration of VPA, the variation of GNB3 C825T remained significantly associated with the levels of serum leptin and body mass index (BMI; P < 0.001 and P = 0.030, respectively). In addition, the GNB3 C825T showed significant drug-single-nucleotide polymorphism interactions with insulin levels (P = 0.033), triglyceride levels (P = 0.013), leptin levels (P = 0.013), and BMI (P = 0.018). These results indicated that the T allele may be associated with lower serum leptin levels and BMI in BD patients treated with VPA. CONCLUSIONS: The current study provides evidence that BD patients who are T allele carriers of the GNB3 C825T polymorphism have a lower risk for VPA-induced metabolic abnormalities. Further studies about the underlying mechanisms of G protein in VPA-induced metabolic abnormalities are warranted.

HPLC-fluorescence assay for measuring mosapride in small volumes of rat plasma.

A simple and sensitive HPLC-fluorescence assay was developed for the determination of a gastroprokinetic agent mosapride in small volumes of rat plasma. Samples (50 microL) were treated with 200 microL of the internal standard solution (cisapride, 0.1 microg/mL in acetonitrile). Chromatographic separation was achieved on a C(18) column by gradient elution with the mobile phase of acetonitrile-water containing 20 mM potassium dihydrogen phosphate, at a flow rate of 1 mL/min. Fluorescence was measured with excitation and emission set at 315 and 354 nm, respectively. The retention time was about 16 min for cisapride and 20 min for mosapride. No endogenous substances were found to interfere. The calibration curve was linear from 0.015 to 10 microg/mL. The lower limit of quantification was 0.015 microg/mL. The intra- and inter-day precision expressed as relative standard deviation did not exceed 7.7%, and the accuracy was within 4.7% deviation of the nominal concentration. The method was used successfully to investigate the disposition kinetics of mosapride in rats.

High prevalence of metabolic disturbances in patients with bipolar disorder in Taiwan.

BACKGROUND: Both ethnicity and lifestyle may contribute to these abnormalities. High prevalences of obesity and metabolic disturbances in patients with bipolar disorder (BD) have been reported in western countries. However, reports about the prevalences in Asian countries remain scant. METHOD: The cross-sectional study included 117 patients diagnosed as BD and treated with lithium (Li), valproate (VPA), or both at a university psychiatric outpatient clinic. Their body mass index and plasma levels of glucose and lipid were measured. The prevalence of metabolic syndrome was determined based on the IDF 2005 criteria. RESULTS: 13.7%, 36.8%, 53.0%, 18.6%, and 61.0% of the patients met the criteria for hyperglycemia, hypertriglyceridemia, low high-density lipoprotein cholesterol (HDL-C), hypertension and large waist circumference, respectively. 33.9% of the patients met the IDF 2005 criterion for metabolic syndrome. The prevalence of metabolic abnormalities was significantly higher in patients who have been cotreated with second-generation antipsychotics (SGAs). CONCLUSION: This study provides evidence of high prevalence of metabolic syndrome in BD patients in Taiwan. Such metabolic disturbances can increase morbidity and mortality. Further studies that focus on the underlying mechanisms and effective intervention strategies are warranted.

Methotrexate conjugated to gold nanoparticles inhibits tumor growth in a syngeneic lung tumor model.

Methotrexate (MTX), a stoichiometric inhibitor of dihydrofolate reductase, is a chemotherapeutic agent for treating a variety of neoplasms. Impairment of drug import into cells and increase in drug export from cells may render cells resistant to MTX. MTX, when locally administered in a soluble form, is rapidly absorbed through capillaries into the circulatory system, which may also account for therapeutic failure in patients. To retain MTX within tumor cells for longer duration and alter its pharmacokinetic behavior, we proposed a new formulation of MTX bound to the gold nanoparticle (AuNP) that serves as drug carriers. In this study, we developed the MTX-AuNP conjugate and examined its cytotoxic effect in vitro and antitumor effect in vivo. Spectroscopic examinations revealed that MTX can be directly bound onto AuNP via the carboxyl group (-COOH) to form the MTX-AuNP complex and kinetically released from the nanoparticles. The accumulation of MTX is faster and higher in tumor cells treated with MTX-AuNP than that treated with free MTX. Notably, MTX-AuNP shows higher cytotoxic effects on several tumor cell lines compared with an equal dose of free MTX. This can be attributed to the "concentrated effect" of MTX-AuNP. Administration of MTX-AuNP suppresses tumor growth in a mouse ascites model of Lewis lung carcinoma (LL2), whereas an equal dose of free MTX had no antitumor effect. In conclusion, these results suggest that by combining nanomaterials with anticancer drugs MTX-AuNP may be more effective than free MTX for cancer treatment.

Determination of norfloxacin in rat liver perfusate using capillary electrophoresis with laser-induced fluorescence detection.

A capillary zone electrophoresis method has been developed for the direct determination of norfloxacin in the physiological perfusate of isolated rat liver. Norfloxacin and the internal standard triamterene were detected using laser-induced fluorescence (LIF) detection with the excitation and emission wavelength of 325 and 435 nm, respectively. The background electrolyte (BGE) was 50 mM phosphate buffer (pH 4.6). The effect of pH and concentration of BGE on the electrophoretic migration and fluorescence response of analytes were examined. Calibration curves were linear over a wide range of 0.01-100 microg/mL. The limit of quantitation was 0.01 microg/mL. The intra- and inter-day relative standard deviation was 3.7%, or less, and the accuracy was 93.2% of the nominal concentration. No endogenous substances were found to interfere. The method was used to characterize the steady-state and transient pharmacokinetics of norfloxacin in the rat liver.

Development and validation of a high-performance liquid chromatographic method using fluorescence detection for the determination of vardenafil in small volumes of rat plasma and bile.

A new, simple and sensitive high-performance liquid chromatography (HPLC) method with fluorescence detection was developed and validated for the determination of vardenafil in small volumes of rat plasma and bile. The absorbance and fluorescence characteristics of vardenafil were studied and factors that affect the HPLC resolution and fluorescence intensity were examined and optimized. Vardenafil and the internal standard cisapride were extracted using acetonitrile. The separation was achieved on a C18 column at 35 degrees C using acetonitrile-50 mM ammonium acetate aqueous solution (pH 6.8) (40:60) as mobile phase. At a flow rate of 1 ml/min, the total run time was 18 min. Fluorescence was measured with excitation and emission set at 280 and 470 nm, respectively. The calibration curves were linear from 10 to 1000 ng/ml and 0.2-100 microg/ml for plasma and bile samples, respectively. The intra- and inter-day imprecision did not exceed 10.8%, and the accuracy was within 9.6% deviation of the nominal concentration. The method was used successfully to investigate the disposition and biliary excretion of vardenafil in rats.

Amelioration of collagen-induced arthritis in rats by nanogold.

OBJECTIVE: Angiogenesis plays a part in the pathogenesis of rheumatoid arthritis (RA), and nanogold inhibits the activity of an angiogenic factor, vascular endothelial growth factor (VEGF). We therefore investigated whether intraarticular delivery of nanogold ameliorates collagen-induced arthritis (CIA) in rats. METHODS: Binding of 13-nm nanogold to VEGF in human RA synovial fluid (SF) and its effects on RA SF-induced endothelial cell proliferation and migration were assessed. Nanogold was administered intraarticularly to rats with CIA before the onset of arthritis. Progression of CIA was monitored by measures of clinical, radiologic, and histologic changes. In addition, the microvessel density and extent of infiltrating macrophages as well as levels of tumor necrosis factor alpha (TNFalpha) and interleukin-1beta (IL-1beta) in the ankle joints were determined. RESULTS: Nanogold bound to VEGF in RA SF, resulting in inhibition of RA SF-induced endothelial cell proliferation and migration. Significant reductions in ankle circumference, articular index scores, and radiographic scores were observed in the nanogold-treated rats with CIA compared with their control counterparts. In addition, the histologic score (of synovial hyperplasia, cartilage erosion, and leukocyte infiltration), microvessel density, macrophage infiltration, and levels of TNFalpha and IL-1beta were also significantly reduced in the ankle joints of nanogold-treated rats. CONCLUSION: Our results are the first to demonstrate that intraarticular administration of nanogold ameliorates the clinical course of CIA in rats. Nanogold exerted antiangiogenic activities and subsequently reduced macrophage infiltration and inflammation, which resulted in attenuation of arthritis. These results demonstrate proof of principle for the use of nanogold as a novel therapeutic agent for the treatment of RA.

Determination of tadalafil in small volumes of plasma by high-performance liquid chromatography with UV detection.

Tadalafil is a potent reversible phosphodiesterase-5 inhibitor used for the treatment of erectile dysfunction. This study describes a simple and sensitive high-performance liquid chromatographic (HPLC) method for the determination of tadalafil in 50 microl of rat plasma. Tadalafil and the internal standard lamotrigine were extracted with 0.5 ml of tert-butyl methyl ether, after the samples alkalinized with 20 microl of sodium hydroxide solution (1N). Chromatographic separation was achieved on a C18 column with the mobile phase of acetonitrile-water containing 20 mM phosphate buffer (pH 7) (35/65, v/v), at a flow rate of 1 ml/min. The eluant was detected at 290 nm. The retention time was about 4.5 min for lamotrigine and 15 min for tadalafil. No endogenous substances were found to interfere. Calibration curves were linear from 10 to 2000 ng/ml. The recovery of tadalafil from plasma was greater than 77%. The limit of quantitation was 10 ng/ml. The intra- and inter-day imprecision (expressed as coefficient of variation, C.V.) did not exceed 10.7%, and the accuracy was within 5.9% deviation of the nominal concentration. The method is suitable in pharmacokinetic investigation and monitoring tadalafil concentration.

Aqueous dispersions of magnetite nanoparticles with NH3+ surfaces for magnetic manipulations of biomolecules and MRI contrast agents.

In the current study, amine surface modified iron-oxide nanoparticles of 6 nm diameter without polymer coating were fabricated in an aqueous solution by organic acid modification as an adherent following chemical coprecipitation. Structure and the superparamagnetic property of magnetite nanoparticles were characterized by selected area electron diffraction (SAED) and superconducting quantum interference measurement device (SQUID). X-ray photoelectron spectrometer (XPS) and zeta potential measurements revealed cationic surface mostly decorated with terminal -NH(3)(+). This feature enables them to function as a magnetic carrier for nucleotides via electrostatic interaction. In addition, Fe(3)O(4)/trypsin conjugates with well-preserved functional activity was demonstrated. The nanoparticles displayed excellent in vitro biocompatibility. The NMR and the in vitro MRI measurements showed significantly reduced water proton relaxation times of both T(1) and T(2). Significantly reduced T(2) and T(2)*-weighted signal intensity were observed in a 1.5 T clinical MR imager. In vivo imaging contrast effect showed a fast and prolonged inverse contrast effect in the liver that lasted for more than 1 week. In addition, it was found that the spherical Fe(3)O(4) assembled as rod-like configuration through an aging process in aqueous solution at room temperature. Interestingly, TEM observation of the liver tissue revealed the rod-like shape but not the spherical-type nanoparticles being taken up by the Kupffer cells 120 h after tail vein infusion. Combining these results, we have demonstrated the potential applications of the newly synthesized magnetite nanoparticles in a broad spectrum of biomedical applications.