Photocatalytic interaction of aminophylline-riboflavin leads to ROS-mediated DNA damage and cell death: A novel phototherapeutic mechanism for cancer.

The accompanied tissue devastation and systemic toxicity of chemotherapy has shifted the quest for having an effective and palliative cancer therapy towards photodynamic therapy (PDT). Riboflavin (Rf), an essential micronutrient is emerging as a potent tool of PDT, due to its excellent photosensitizing properties. It can be used as an efficient adjuvant for various anticancer drugs. The hemolytic and proteolytic effect of photoilluminated aminophylline (Am), a xanthine derivative, and Rf is well documented in literature. In this study, using human peripheral lymphocytes we have demonstrated the strong pro-oxidant effects of photocatalytic interaction between Am and Rf. The photo degradation kinetics of Am in the presence of Rf was monitored using UV spectroscopy, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The resultant pro-oxidant action of Am was monitored through various assays like lipid peroxidation, protein carbonylation, and reactive oxygen species (ROS) generation. Furthermore, the cytotoxic potential of this system was studied using comet and MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay. Treated lymphocytes were visualized using fluorescence and scanning electron microscopy to further validate apoptosis. ROS scavengers ameliorated the oxidative damage caused by this system suggesting pivotal role of ROS in causing apoptotic cell death. As cancer cells exhibit increased absorption of Rf as well as are very sensitive in any further ROS level increment, this putative pathway can serve as an effective anodyne phototherapeutic strategy for cancer treatment. © 2017 IUBMB Life, 69(8):611-622, 2017.

Determination of Aminophylline in Human Serum Using Hydrogel Microspheres for Coupled Surface-Enhanced Raman Spectroscopy (SERS) and Solid-Phase Extraction.

Aminophylline (AMP) is a bronchodilator. The therapeutic and toxic doses are very close. Therefore, therapeutic drug monitoring (TDM) of AMP is essential in clinical practice. Microgels were synthesized by free radical precipitation polymerization. Silver@poly(N-isopropyl acrylamide) (Ag@PNIPAM) hybrid microgels were obtained by loading silver (Ag) nanoparticles into the three-dimensional network of the microgels by in situ reduction. The microgel is a three-dimensional reticular structure with tunable pore size, large specific surface area, and good biocompatibility, which can be used as a sorbent for solid-phase extraction (SPE) of target molecules in complex matrices and as a surface-enhanced Raman spectroscopy (SERS) substrate. We optimized the conditions affecting SERS enhancement, such as silver nitrate (AgNO3) concentration and SPE time, according to the SERS strategy of Ag@PNIPAM hybrid microgels to achieve label-free TDM for trace AMP in human serum. The results showed good linearity between the logarithmic concentration of AMP and its SERS intensity in the range of 1-1.1 × 102 µg/mL, with a correlation coefficient (R2) of 0.9947 and a low detection limit of 0.61 µg/mL. The assay accuracy was demonstrated by spiking experiments, with recoveries ranging from 93.0 to 101.8%. The method is rapid, sensitive, reproducible, requires simple sample pretreatment, and has good potential for use in clinical treatment drug monitoring.

Preliminary evaluation of the in vitro release and in vivo absorption in rabbits of the modified-release dosage forms.

OBJECTIVE: The suitability of the rabbit as an animal model for the primary screening and selection of the pilot scale batches during the early stages of the formulation development was studied. MATERIALS AND METHODS: Three modified-release formulations of aminophylline consisted of Carbopol® 971P/HPMC K4M (F-I), and HPMC K100M (F-II) or HPMC K4M (F-III) were used. Commercial products were Aminofilin retard 350 mg tablets, Srbolek, Serbia (R-I) and Phyllocontin(®) 350, tablets Purdue Frederic, Canada (R-II). RESULTS: Calculated release rate constants and the ƒ2 values between R-I/F-I (84.1) and R-II/F-III (83.4) indicated similar in vitro release while the coefficient n showed presence of different mechanisms of release from Anomalous transport, Fickian diffusion to Case-II transport. Higher Tmax, was found in the rabbits, dosed with F-II (12.00 h), F-III (10.50 h), and R-II (15.00 h) formulation. The highest Cmax (9.22 mg/L) was obtained with F-II, similar lower values was seen for F-I and F-III, while commercial products showed the lowest values R-I (5.58 mg/L) and R-II (4.18 mg/L). Higher AUC values were detected for all three formulations (from 115.90 to 204.06 mgh/L) in relation to commercial products (105.33 and 113.25 mgh/L). DISCUSSION AND CONCLUSION: The results demonstrated a good correlation of Level A (r(2) = 0.97) for the two formulations (F-I, F-III) and commercial product (R-I) indicates that there is a reasonable assumption that the rabbit might be use as a model for the preliminary comparison of scale up formulations in the early stages of the product development.

An investigation into effects of in vitro test condition on the release properties of theophylline from HPMC matrices using factorial design.

The purpose of this study was to investigate the effect of various in vitro test conditions, on the release properties of theophylline (TP) from aminophylline (AP) matrices based on different hydroxypropylmethylcellulose (HPMC) ratio and viscosity grades. The general full factorial experimental design 3 x 3 x 3 was used, based on three independent variables: applied in vitro test (X1), HPMC/drug ratio (X2) and polymer viscosity grade (X3). The drug release percent at 2h (Y(2h)), 4h (Y(4h)) and 8 h (Y(8h)) and time for 50% of TP release from matrices (Y(T50%)) were response variables. Three in vitro tests were used: test 1 and test 4 (theophylline extended-release capsules, USP 30) and half-change method. According to factorial design analyses, in vitro test was the most significant factor influencing mechanism and amount of drug release. For half change method erosion was the predominant mechanism indicating case - II transport, while for test 1 the release mechanism were followed by both diffusion and erosion. The lowest release exponent n values, obtained from Ritger-Pepass equation, for test 4 indicate diffusion process inclining from Fickian diffusion to anomalous transport. Therefore, it is in the stage of development, useful to consider the influence of various in vitro test conditions on the formulation, in order to choose an optimal test for the purpose of future drug release examination.

Surface crosslinking for delayed release of proxyphylline from PHEMA hydrogels.

Delayed release systems find applications in chronotherapeutics and colon-specific delivery. They have also been considered suitable carriers for the oral delivery of peptides and proteins. In prior work, our research group has reported surface crosslinking as an effective technique to modify drug release profiles for poly(vinyl alcohol) (PVA) hydrogels, reducing the early burst effect in particular. Here, we demonstrate the feasibility of delayed release of proxyphylline from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels via surface crosslinking. Studies on in vitro drug release and the morphology changes of PHEMA hydrogels during swelling and drug release showed that the highly surface crosslinked layers and the ruptures occurring in these layers during swelling were likely responsible for the delayed release. In addition, the initial burst was significantly reduced or even eliminated from the drug release profile for PHEMA to achieve near zero-order release by judicious selection of two surface crosslinking parameters: crosslinking reagent concentration and exposure time used for the surface crosslinking treatment.

Modifying the release of proxyphylline from PVA hydrogels using surface crosslinking.

Drug release profiles were altered to prevent the initial burst effect or introduce a lag phase by creating surface crosslinked layers in poly(vinyl alcohol) (PVA) hydrogels. Confocal laser scanning microscopy (CLSM) confirmed the successful introduction of these surface crosslinked layers. The thickness and crosslinking density of the surface crosslinked layer were highly dependent on the surface crosslinking conditions (i.e., exposure time and glutaraldehyde (GTA) concentration used). By judicious selection of these parameters, the initial burst release could be eliminated and a reproducible delayed release could be achieved. Highly surface crosslinked layers had a tendency to rupture during the swelling process of PVA hydrogels; these raptures were found to coincide with delayed release of proxyphylline from surface crosslinked PVA hydrogels.

Synthesis, pharmacological activity and nitric oxide generation by nitrate derivatives of theophylline.

Nitrates of theophylline derivatives - potential nitric oxide (NO) donors - were synthesized by esterification of 7-hydroxyalkyl theophylline derivatives with fuming nitric acid. The nitrates obtained were tested in-vitro in reactions with sulfydryl compounds at appropriately adjusted pH and temperature. Under the applied conditions, the synthesized compounds underwent decomposition to release NO, quantified using a polarographic method using a selective isolated (ISO-NO) sensor. The effects of dyphylline and proxyphylline and their new synthesized nitrates on arterial blood pressure (BP) were measured in spontaneously hypertensive (SH) rats. BP was measured in conscious SH rats using the tail-cuff method. Both short- and long-term administration of the xanthines tested significantly decreased systolic, diastolic and mean BP. The hypotensive effect of a single dose of nitrate dyphylline on mean BP was greater than that of the parent compound (P = 0.000012; P=0.000472 at 30 and 60 min post-dose, respectively), whereas proxyphylline and its nitrate derivative had similar activity. In rats treated with the tested compounds for 9 days twice daily, the decrease in BP persisted for at least 16 h after the last dose. Proxyphylline produced the most marked decrease in diastolic and mean BP. Among the xanthines examined, proxyphylline nitrate had the strongest hypotensive effect when administered in a single dose to animals pretreated with the same compound for 9 days. These results indicate that insertion of a nitrate group weakly modifies the hypotensive action of the studied xanthines in SH rats.

A novel spectrophotometric method for the determination of aminophylline in pharmaceutical samples in the presence of methanol.

A rapid, simple and sensitive method for the determination of aminophylline (Ami) using sodium 1, 2-naphthoquine-4-sulfonate (NQS) and methanol is established in this paper. It is based on the fact that a russety product can be formed by the reaction between aminophylline (Ami) and sodium 1, 2-naphthoquine-4-sulfonate (NQS) in pH 13.00 buffer solution. When methanol is added to the solution, the sensitivity of the color development reaction between Ami and NQS is improved, and the color of the system of NQS-Ami becomes a salmon pink. Beer's law is obeyed in a range of 4.97-69.5 microg ml(-1) of Ami at the maximum absorption of 453 nm (epsilon=4.87 x 10(3) l mol(-1) cm(-1)). The linear regression equation of the calibration curve is A=0.14458+0.00832C (microg ml(-1)), with a linear regression correlation coefficient of 0.9944. The detection limit is 0.7 microg ml(-1) (3sigma/k), R.S.D. is 1.1% and the recovery rate is in range of 92.5-105%. Furthermore, this method has been successfully applied to the determination of Ami in pharmaceutical samples.

Vehicle and enhancer effects on human skin penetration of aminophylline from cream formulations: evaluation in vivo.

The effects of four essential oils (rosemary, ylang, lilacin, and peppermint oils), and three plant oils (jojoba oil, corn germ oil, and olive oil) on the permeation of aminophylline were studied using human skin. The permeation effects of these oils were compared with those of three chemical penetration enhancers. Although all oils enhanced the permeation of aminophylline, their effects were less than that of ethanol. Jojoba oil was found to be the most active, causing about a 32% peak height decrease of N-H bending absorbances in comparison with the control, while peppermint, lilacin, rosemary, and ylang oils caused 28%, 24%, 18%, and 12% peak height decreases, respectively. Microemulsions containing 10% jojoba oil and 30% corn germ oil were found to be superior vehicles for the percutaneous absorption of aminophylline. Comparision with results obtained from high-performance liquid chromatography shows good agreement.

[Studies on drug release from aminophylline konjac glucomannan matrix tablet].

OBJECTIVE: In vitro aminophylline release from matrix tablets with konjac glucomannan (KGM) were studied to elevate the feasibility of KGM used as carrier materials to prepare matrix tablets. METHOD: KGM hydrophilic matrix tablets were prepared by direct compression method with aminophylline as the model drug. The effects of test methods, pH values, ionic strength of dissolution media and rotation speeds on drug release were studied by in vitro dissolution experiment. RESULT: The MDT value tested by Paddle method was less than that tested by Basket method (P < 0.05). Among the rate of drug release in different dissolution media, distillded water is the fastest, pH 6. 8 PBS is the second, 0.1 mol x L(-1) HCL is the slowest. MDT increased with increasing the ionic strength of dissolution media (P < 0.05). MDT decreased with increasing the rotation speed, but the rate of drug release did not increase when the rotation speed was more than 100 r x min(-1) (P > 0.1). The mechanism of drug release were diffusion and erosion. CONCLUSION: KGM can be used in sustained delivery systems as a good candidate of hydrophilic polymer.

Biodegradable cross-linked prodrug of the bronchial dilator Vephylline. 2. Kinetics and quantum chemical studies on the release mechanism.

Experimental thermodynamics studies and quantum chemical reaction path calculations on the hydrolytic degradation of Poly-vephyllinemalate microspheres in acidic and basic media were performed. It was possible to make a conclusion on the release mechanism of free Vephylline as follows: a hydrolytic cleavage of the ester bonds between molecular fragments of R,S-malic acid takes place and leads to a soluble oligoester fraction. Then, further hydrolysis of the ester bonds between the xanthine fragment and R, S-malic acid leads to the release of Vephylline as free base. The hydrolytic process takes place in acidic solution with rapid degradation of the ester bonds between the malic acid monomers and by far slower degradation of the ester bonds between the malic acid and Vephylline. In basic solution both steps of the hydrolysis are fast processes leading to a complete release of free Vephylline within 1 h. The process of Vephylline release is under entropic control. The experimental results are well correlated to the results obtained after kinetics investigation and after AM1 quantum chemically calculated energy barriers in the reaction path leading to the tetrahedral intermediates of the hydrolytic reactions. This conclusion is in good accordance with an indirect study on the release mechanism of Vephylline from its polymeric prodrug, paying attention to the biological response, reported previously.

Biopharmaceutical characterization of oral theophylline and aminophylline tablets. Quantitative correlation between dissolution and bioavailability studies.

Considering the narrow therapeutic index of theophylline and the low range between the safe and toxic serum concentrations of this drug, the study of its pharmacokinetic properties is necessary. However, considering the time consuming and expensive in vivo tests, quantitative correlation between in vivo bioavailability and in vitro dissolution tests can be used routinely in quality control tests of these drug products to predict the in vivo pharmacokinetic parameters. For this reason healthy human volunteers were used for in vivo studies and serum samples were analyzed by a fluorescence polarization immunoassay analysis (FPIA) method. The results showed that an open one compartmental model could best describe the pharmacokinetic properties of orally administered theophylline and aminophylline tablets. Linear regression analysis by least-square method showed a good correlation between some in vivo and in vitro parameters obtained from dissolution studies by rotating basket and paddle methods. D(30)% (percentage of drug dissolved in vitro after 30 min) and F(0.5)% (drug absorbed in vivo after half an hour calculated by Wagner-Nelson equation) showed best correlation (r=0. 99036). C(max) (maximum serum concentration) of this drug also correlates well with t(25%) (time required to dissolve 25% of the drug). The calculated correlation coefficients could best predict the actual values of some pharmacokinetic parameters; AUC(0-->infinity), AUC(0-->1), F(0.5)% and C(max).

Rheological behavior of drug suspensions in Gelucire mixtures and proxyphylline release from matrix hard gelatin capsules.

Mixtures of Gelucires 50/02 and 50/13 showing different hydrophilic-lipophilic balances (HLB) and of proxyphylline were used to prepare suspensions at a concentration of 25% and to manufacture extended release hard gelatin capsules by cooling. The rheological behaviors of Gelucire mixtures with and without drug were determined by adjustment of the rheograms to the Ostwald power-law and by statistical assessment of the flow index. Pure Gelucire mixtures were very slightly shear thickening whereas proxyphylline suspensions had a thixotropic shear thinning behavior. These rheological behaviors can be explained by the chemical composition and by the ratio of the two Gelucires used. Extended release of proxyphylline was obtained with all these mixtures. Drug release increased with Gelucire mixture HLB owing to higher erosion. A viscosity-release relationship was found and allowed, with these two Gelucires of extreme HLB and viscosities, to define the formulations which will give an optimal drug release, by the determination of their suspension viscosity. Modeling of dissolution kinetics has generally shown the predominance of surface erosion of the plugs relative to drug diffusion inside the matrix. This was confirmed by the better linearization of percentage released, according to Hixson-Crowell as compared with Higuchi.

Rheology of polyol behenates and drug release from matrix monolithic capsules.

Three polyol behenates with similar melting points (MP) and different hydrophilic-lipophilic balances (HLB) were studied (MP/HLB: 70/02, 63/05 and 57/13). After melting at MP+30 degrees C, the rheological behaviour of behenates was determined by adjustment of the rheograms to the Ostwald power-law and by statistical assessment of the flow index. Behenates showed slight shear thickening. This shear thickening increased when HLB of behenates decreased. This behaviour accounted for a reorganization of the particles under the shear, which became easier when the proportion of the polyethylene glycol chains in the wax decreased. Proxyphylline was used to prepare suspensions at a concentration of 25% in the melted behenates, and to manufacture monolithic capsules by cooling. The suspensions had a shear-thinning behaviour with or without thixotropy. Colloidal particles and aggregates formed in these suspensions directly influenced the rheological properties, as observation of solidified suspensions by scanning electron microscopy confirmed. Extended release of proxyphylline was obtained with the three waxes. Behenates 63/05 and 70/02 gave inert matrices and released drug very slowly. Hydrodispersible behenate 57/13 swelled and made up a kind of hydrophilic matrix that released proxyphylline more quickly, due to slight erosion. In the three cases, the release mechanism was basically diffusional in nature.

The effect of the cross-linking time period upon the drug release and the dynamic swelling of gelatin microspheres.

The cross-linking time period affected both the swelling and release processes of cross-linked gelatin microspheres. In the dynamic swelling procedure, the combination of both phenomena of microparticle swelling and drug diffusion produced at first the increase and then the decrease of the diameter of a loaded microsphere. The increase of the cross-linking time period produced the shift of the penetrant transport from anomalous to super-case II kinetics. This behaviour could justify the decrease of the diffusion component of the drug release as the cross-linking time period increased.

[Comparative evaluation of dissolution and membrane transport methods of suppositories]. / Kioldódás és membrántranszport vizsgáló módszerek összehasonlító értékelése kúpkészítményekben.

The dissolution and transport rate constants of Diaphyllin, Feldene, Naprosyn and Tilcotil suppositories originated from the same batches were studied. The dissolution tests were carried out with Desaga type flow cell. The membrane transport experiments were performed in "Mühlemann-tester" and in the own designed "membrane-diffusion cell". The values of the dissolution rate constants were higher than the diffusion rate constants. The results of the same batches of the suppositories tested in Mühlemann-tester or in the own designed membrane-diffusion cell were in good correlation. On the basis of the experiments carried out by the membrane-diffusion cell we can state that it is able to be standardised, automated and the results show good reproducibility.

Comparative study of the binding of pepsin to four alkaloids by spectrofluorimetry.

The interactions between pepsin and four alkaloids, including caffeine (Caf), aminophylline (Ami), acefylline (Ace), diprophylline (Dip), were investigated by fluorescence, UV-visible absorption, resonance light scattering, synchronous fluorescence spectroscopy and 3D spectroscopy under mimic physiological conditions. The results revealed that Caf (Ami/Ace/Dip) caused the fluorescence quenching of pepsin by the formation of Caf (Ami/Ace/Dip)-pepsin complex. The binding constants and thermodynamic parameters at three different temperatures, the binding locality and the binding power were obtained. The hydrophobic and electrostatic interactions were the predominant intermolecular forces to stabilize the complex. Results showed that aminophylline was the stronger quencher and bound to pepsin with higher affinity than other three alkaloids.

pH- and Temperature-Responsive P(DMAEMA-GMA)-Alginate Semi-IPN Hydrogels Formed by Radical and Ring-Opening Polymerization for Aminophylline Release.

A novel poly((2-dimethylamino) ethyl methacrylate-glycidyl methacrylate)-alginate (P(DMAEMA-GMA)alginate) semi-IPN hydrogel was synthesized via radical polymerization of the double bonds and ring-opening of the epoxy groups without using catalyst and cross-linker. (1)H-NMR, FT-IR and DSC data were consistent with the expected structures for the hydrogels. The interior morphology of the hydrogels was also investigated by SEM. The swelling ratio and compressive strength of the hydrogels were measured. The semi-IPN hydrogel had pH and temperature sensitivity, and pH-sensitive points of all hydrogels were found to be at pH 5.0. The release behavior of the model drug, aminophylline, was found to be dependent on the hydrogel composition and environment pH, which manifests that these materials have potential applications as intelligent drug carriers.