共查询到20条相似文献,搜索用时 15 毫秒
1.
Systemically injected nanoparticle (NPs) targeting tumor vasculature offer a venue for anti-angiogenic therapies as well as cancer detection and imaging. Clinical application has been limited, however, due to the challenge of elucidating the complex interplay of nanotechnology, drug, and tumor parameters. A critical factor representing the likelihood of endothelial adhesion is the NP vascular affinity, a function of vascular receptor expression and NP size and surface-bound ligand density. We propose a theoretical framework to simulate the tumor response to vasculature-bound drug-loaded NPs and examine the interplay between NP distribution and accumulation as a function of NP vascular affinity, size, and drug loading and release characteristics. The results show that uniform spatial distribution coupled with high vascular affinity is achievable for smaller NPs but not for larger sizes. Consequently, small (100 nm) NPs with high vascular affinity are predicted to be more effective than larger (1000 nm) NPs with similar affinity, even though small NPs have lower drug loading and local drug release compared to the larger NPs. Medium vascular affinity coupled with medium or larger sized NPs is also effective due to a more uniform distribution with higher drug loading and release. Low vascular affinity hampered treatment efficacy regardless of NP size, with larger NPs additionally impeded by heterogeneous distribution and drug release. The results further show that increased drug diffusivity mainly benefits heterogeneously distributed NPs, and would negatively affect efficacy otherwise due to increased wash-out. This model system enables evaluation of efficacy for vascular-targeted drug-loaded NPs as a function of critical NP, drug, and tumor parameters. 相似文献
2.
Fabiana S. Leite Marcus A. Silva Moacyr Araujo Rodolfo A. Silva Enrique L. Droguett 《人类与生态风险评估》2014,20(1):150-173
Despite the fast growth of underwater oil and gas exploration in low latitude regions, very few experimental data acquisition and modeling studies involving gas release in tropical and shallow waters are found in literature. In this article, a dataset of geophysical and gas release measurements obtained from an in situ experiment conducted off the northeastern Brazilian coast are used as a baseline for evaluating the GASOCEAN blowout model. Hydrological and hydrodynamic data were collected for distinct seafloor gas plume releases (3000 to 9000 L/hr) during neap/spring tides of summer/dry and winter/wet periods. Simulation results indicate that the gas plume is horizontally displaced by the horizontal current as it rises through seawater column. The extreme situation provided a critical radius (maximum horizontal displacement) from the gas release source of 35.2 m. The comparison between the measured and the calculated data showed that the model satisfactorily represented the main features of the gas release, such as the displacement (11.6–35.2 m), diameter (1.2–2.8 m), and ascending time (1.1–1.6 min) of the plumes. Although the mean plume widths have the same order of magnitude between the measurements and the calculations, improvements may enhance the model's performance during the earlier plume development. 相似文献
3.
新型功能性纳米材料在设计和制备技术方面的进步为纳米医学的发展提供了很大的机遇。在过去十年中,介孔碳纳米材料在制备和应用方面获得了巨大的进步。作为一种新型无机材料体系,介孔碳纳米材料结合了介孔的结构以及碳质组成的特点,显示出不同于传统介孔二氧化硅以及其它一些碳基材料体系(碳纳米管、石墨烯、富勒烯等)的优越特性。介孔碳纳米材料在药物的吸附与控释、光热治疗、协同治疗、肿瘤细胞的荧光标记、催化、生物传感、生物大分子的分离等诸多领域表现出其他多孔材料难以达到的优越性和应用潜力。本文对介孔碳纳米材料的制备和修饰技术进行介绍,重点关注介孔碳纳米颗粒在药物负载和光热控释方面的应用,最后对介孔碳纳米材料在生物医学领域的应用前景和所面临的关键问题进行讨论。 相似文献
4.
Pornsak Sriamornsak Jurairat Nunthanid Kamonrak Cheewatanakornkool Somkamol Manchun 《AAPS PharmSciTech》2010,11(3):1315-1319
Drug-loaded calcium pectinate gel (CaPG) beads were prepared by either mixing, absorption, or swelling method. The effects of drug loading method as well as the drug loading factors (i.e., drug concentration, soaking time in drug solution, type of solvent) on drug content and drug release were investigated. The amount of drug uptake (i.e., drug content) into CaPG beads increased as the initial drug concentration increased and varied depending on the loading method. The in vitro release studies in 0.1 N hydrochloric acid (HCl) and pH 6.8 buffer indicated that the drug loading method affected drug release and release parameter, time for 50% of drug release (T 50). The mixing method provided a faster drug release and lower T 50 than the absorption method and swelling method, respectively. This is probably due to higher drug content in CaPG beads. The increased concentration of drug in soaking solution and soaking time resulted in higher drug content and thus faster drug release (lower in T 50 values). When using 0.1 N HCl as solvent for soaking instead of water, the drug release was slower owing to the increase in molecular tortuosity of CaPG beads. The drug release was also affected by pH of the release medium in which drug release in 0.1 N HCl was faster than in pH 6.8 buffer. 相似文献
5.
Alka A. Potdar Joydeep Sarkar Nupur K. Das Paroma Ghosh Miklos Gratzl Paul L. Fox Gerald M. Saidel 《PLoS computational biology》2014,10(7)
A major process of iron homeostasis in whole-body iron metabolism is the release of iron from the macrophages of the reticuloendothelial system. Macrophages recognize and phagocytose senescent or damaged erythrocytes. Then, they process the heme iron, which is returned to the circulation for reutilization by red blood cell precursors during erythropoiesis. The amount of iron released, compared to the amount shunted for storage as ferritin, is greater during iron deficiency. A currently accepted model of iron release assumes a passive-gradient with free diffusion of intracellular labile iron (Fe2+) through ferroportin (FPN), the transporter on the plasma membrane. Outside the cell, a multi-copper ferroxidase, ceruloplasmin (Cp), oxidizes ferrous to ferric ion. Apo-transferrin (Tf), the primary carrier of soluble iron in the plasma, binds ferric ion to form mono-ferric and di-ferric transferrin. According to the passive-gradient model, the removal of ferrous ion from the site of release sustains the gradient that maintains the iron release. Subcellular localization of FPN, however, indicates that the role of FPN may be more complex. By experiments and mathematical modeling, we have investigated the detailed mechanism of iron release from macrophages focusing on the roles of the Cp, FPN and apo-Tf. The passive-gradient model is quantitatively analyzed using a mathematical model for the first time. A comparison of experimental data with model simulations shows that the passive-gradient model cannot explain macrophage iron release. However, a facilitated-transport model associated with FPN can explain the iron release mechanism. According to the facilitated-transport model, intracellular FPN carries labile iron to the macrophage membrane. Extracellular Cp accelerates the oxidation of ferrous ion bound to FPN. Apo-Tf in the extracellular environment binds to the oxidized ferrous ion, completing the release process. Facilitated-transport model can correctly predict cellular iron efflux and is essential for physiologically relevant whole-body model of iron metabolism. 相似文献
6.
Etodolac is a non-steroidal anti-inflammatory drug having an elimination half-life of 7 h; oral doses are given every 6–8 h. The aim of current work was the development of controlled-release etodolac lipid matrix tablets. The variables influencing design of these tablets (L1–L28) by the hot fusion method were investigated including; (1) lipid type (stearic acid, cetyl alcohol, cetostearyl alcohol, Imwitor® 900K, Precirol® ATO 5 and Compritol® ATO 888), (2) drug/lipid ratio (1:0.25 and 1:0.50, respectively), (3) filler type (lactose, Avicel® PH101 and their physical mixtures; 2:1, 1:1, and 1:2, respectively), (4) surfactant’s HLB (5 and 11), and (5) drug/surfactant ratio (20:1 and 10:1, respectively). Statistical analysis and kinetic modeling of drug release data were evaluated. The inner matrix of the tablet was visualized via scanning electron microscopy (SEM). An inverse correlation was observed between the drug/lipid ratio and the drug release rate. Precirol®- and Compritol®-containing formulae showed more retarded drug release rates. Lactose/Avicel® physical mixture (1:1) was considered as a filler of choice where it minimized the burst effect observed with Avicel®-free formulae. The higher surfactant’s HLB, the higher drug release rate. The similarity factor (f 2) between the drug release profiles revealed similarity within the investigated drug/surfactant ratios. Sucrose stearate D1805®-based matrix (L21) succeeded in delivering more than 90% of etodolac over 12 h, following anomalous (non-Fickian) controlled-release kinetics. SEM micrographs confirmed pore formation, within the latter matrix, upon contact with dissolution medium. 相似文献
7.
Palmer D Levina M Nokhodchi A Douroumis D Farrell T Rajabi-Siahboomi A 《AAPS PharmSciTech》2011,12(3):862-871
Anionic polymer sodium carboxymethylcellulose (CELLOGEN® HP-HS and/or HP-12HS) was investigated for its ability to influence the release of three model drugs propranolol hydrochloride, theophylline and ibuprofen from polyethylene oxide (POLYOX™ WSR 1105 and/or Coagulant) hydrophilic matrices. For anionic ibuprofen and non-ionic theophylline, no unusual/unexpected release profiles were obtained from tablets containing a mixture of two polymers. However, for cationic propranolol HCl, a combination of polyethylene oxide (PEO) with sodium carboxymethylcellulose (NaCMC) produced a significantly slower drug release compared to the matrices with single polymers. The potential use of this synergistic interaction can be a design of new extended release pharmaceutical dosage forms with a more prolonged release (beyond 12 h) using lower polymer amount, which could be particularly beneficial for freely water-soluble drugs, preferably for once daily oral administration. In order to explain changes in the obtained drug release profiles, Fourier transform infrared absorption spectroscopy was performed. A possible explanation for the more prolonged propranolol HCl release from matrices based on both PEO and NaCMC may be due to a chemical bond (i.e. ionic/electrostatic intermolecular interaction) between amine group of the cationic drug and carboxyl group of the anionic polymer, leading to a formation of a new type/form of the active (i.e. salt) with sustained release pattern.Key words: extended release, FT-IR, ibuprofen, matrix tablet, polyethylene oxide, polymer combination, propranolol hydrochloride, sodium carboxymethylcellulose, theophylline 相似文献
8.
Raxit Y. Mehta Shahrzad Missaghi Sandip B. Tiwari Ali R. Rajabi-Siahboomi 《AAPS PharmSciTech》2014,15(5):1049-1059
Hydrophilic matrix tablets are commonly used for extended release dosage forms. For low aqueous-solubility drugs, there may be challenges in modulation of release profiles and achieving consistent release in physiological conditions. To evaluate potential formulation strategies, matrix tablets of a low-soluble drug, hydrochlorothiazide, were developed using hypromellose and two fillers of different solubility, lactose (soluble) or partially pregelatinized maize starch (partially soluble). Additionally, application of an insoluble barrier membrane, aqueous ethylcellulose coating system, and a hydrophilic pore former onto matrix tablets was evaluated. Drug release from uncoated matrix tablets was variable at different agitation rates. Evaluation of tablets in bio-relevant media using physiologically relevant residence time indicated variable and higher initial release rate for uncoated matrices containing lactose but more robust behavior for tablets containing partially pregelatinized starch. Such in vitro behavior may lead to erratic drug release in vivo, when comparing fed versus fasted conditions. Dissolution profiles from barrier membrane-coated tablets showed initial delay, followed by zero-order release kinetics, with reduction or elimination of variability compared to uncoated matrices. Such reduced variability may mitigate mechanical effects of post-prandial stomach. Effects of coating weight gain and inclusion levels of pore former were evaluated and found to be critical in achieving robust and stable release profiles. 相似文献
9.
Zeki N. Al-Sokanee Abedl Amer H. Toabi Mohammed J. Al-assadi Erfan A. S. Alassadi 《AAPS PharmSciTech》2009,10(3):772-779
Hydroxyapatite (HAP) is an important biomedical material that is used for grafting osseous defects. It has an excellent bioactivity and biocompatibility properties. To isolate hydroxyapatite, pieces of cleaned cattle’s bone were heated at different temperature range from 400°C up to 1,200°C. A reasonable yield of 60.32% w/w HAP was obtained at temperature range from 1,000°C to 1,200°C. Fourier transform infrared spectra and the thermogravimetric measurement showed a clear removal of organic at 600°C as well as an excellent isolation of HAP from the bones which was achieved at 1,000–1,200°C. This was also confirmed from X-ray diffraction of bone sample heated at 1,200°C. The concentration ions were found to be sodium, potassium, lithium, zinc, copper, iron, calcium, magnesium, and phosphate present in bones within the acceptable limits for its role in the bioactivity property of HAP. Glucose powder was used as a porosifier. Glucose was novel and excellent as porogen where it was completely removed by heating, giving an efficient porosity in the used scaffolds. The results exhibited that the ceftriaxone drug release was increased with increasing the porosity. It was found that a faster, higher, and more regular drug release was obtained from the scaffold with a porosity of 10%. 相似文献
10.
Renata P. Raffin Paolo Colombo Fabio Sonvico Alessandra Rossi Denise S. Jornada Adriana R. Pohlmann Silvia S. Guterres 《AAPS PharmSciTech》2009,10(2):335-345
Pantoprazole-loaded microparticles were prepared using a blend of Eudragit® S100 and Methocel® F4M. The accelerated stability was carried out during 6 months at 40°C and 75% relative humidity. In order to improve technological characteristics of the pantoprazole-loaded microparticles, soft agglomerates were prepared viewing an oral delayed release and gastro-resistant solid dosage form. The agglomeration was performed by mixing the pantoprazole microparticles with spray-dried mannitol/lecithin powders. The effects of factors such as the amount of lecithin in the spray-dried mannitol/lecithin powders and the ratio between pantoprazole microparticles and spray-dried mannitol/lecithin powders were evaluated. The pantoprazole-loaded microparticles present no significant degradation in 6 months. The agglomerates presented spherical shape, with smooth surface and very small quantity of non-agglomerated particles. The agglomerates presented different yields (35.5–79.0%), drug loading (58–101%), and mechanical properties (tensile strength varied from 44 to 69 mN mm−2), when the spray-dried mannitol/lecithin powders with different lecithin amounts were used. The biopharmaceutical characteristics of pantoprazole microparticles, i.e., their delayed-release properties, were not affected by the agglomeration process. The gastro-resistance of the agglomerates was affected by the amount of spray-dried mannitol/lecithin powders. The ratio of lecithin in the spray-dried mannitol/lecithin powders was the key factor in the agglomerate formation and in the drug release profiles. The agglomerates presenting better mechanical and biopharmaceutical characteristics were prepared with 1:2 (w/w) ratio of pantoprazole-loaded microparticles and mannitol/lecithin (80:20) powder.Key words: agglomerates, delayed release, gastro-resistance, microparticles 相似文献
11.
Phaechamud T 《AAPS PharmSciTech》2008,9(2):668-674
The purpose of this study was to prepare and evaluate layered matrix tablets of propranolol HCl containing HPMC and phytowax
as matrix component using direct compression technique. Layering with this polymeric matrix could prolong the release of drug
and shift the release pattern approach to zero order as described from the least square curve fitting. Increasing the amount
of coating layer could apparently prolong the drug release. The longer lag time of drug release from one planar apparently
when the amount of coating layer was increased. HPMC concentration and compression force did not affect the drug release from
this three-layer tablet. The drug release from this three-layer tablet was influenced by hydrodynamic force. An increase in
stirring rate was a corresponding increasing in the release rate. From photoimage and SEM, gel mass of HPMC was increased
with time during dissolution and covered the core surface, therefore dissolved drug molecules were allowed to diffuse out
from the core through the polymer network of gel layer containing the porous structure. This suggested that HPMC and phytowax
could be fabricated into the layered matrix tablet exhibiting sustained drug release. 相似文献
12.
Haznar-Garbacz D Garbacz G Eisenächer F Klein S Weitschies W 《AAPS PharmSciTech》2011,12(4):1183-1185
A novel oral drug delivery system for the controlled release of liquid drugs, drug solutions, and semisolid drug preparations
is presented that is utilizing the constant vapor pressure of liquefied gas. The system is equipped with a capillary as an
element determining the drug delivery rate and contains a liquefied propellant with a suitable boiling point below human body
temperature. In the dissolution studies, polyacrylate gels of different viscosities containing paracetamol as model drug were
used. Zero-order release kinetics was obtained. The release rates were dependent on the gel viscosity. Besides, by gel viscosity,
the drug release rates could also be modified by changing the propellant type and the capillary parameters such as length
or diameter. Accordingly, the new system enables a wide range of drug delivery kinetics which can be modified in a case-by-case
basis in order to match the desired drug delivery characteristics. 相似文献
13.
Schijven Jack F. Hassanizadeh S. Majid Dowd Scot E. Pillai Suresh D. 《Quantitative Microbiology》2000,2(1):5-20
Experiments with batch suspensions, recirculating columns and flow-through columns have been carried out involving a sandy soil and five bacteriophages: MS2, PRD1, X174, Q and PM2. In batch and recirculating column experiments, attachment and detachment rate coefficients were determined by fitting a two-parameter (attachment and detachment) model. In general, attachment and detachment rate coefficients were not found to be significantly different between the two kinds of experiments. There was one exception, however: MS2 appeared to detach faster in the presence of strong advective flow. In the case of flow-through column experiments, it is shown that a two-site model, with adsorption to equilibrium and kinetic sites, fits the breakthrough curves of all the phages, except PM2, satisfactorily. A one-site kinetic model was found to be appropriate for phage PM2. A small proportion of bacteriophages MS2, PRD1, and Q adsorbed to equilibrium sites, whereas a large proportion of X174 adsorbed to equilibrium sites. Such a distinction between adsorption to equilibrium and kinetic sites cannot be made in the case of batch or recirculating column experiments. Kinetic attachment rate coefficients were found to be significantly higher for the bacteriophages with presumably stronger negative charge. This may be ascribed to the presence of multivalent cations. Under these conditions, bacteriophage X174 appears to behave more conservatively than more negatively charged viruses, and may then be a better choice as a relatively conservative tracer for virus transport through the subsurface. 相似文献
14.
Felix Schneider Melanie Hoppe Mirko Koziolek Werner Weitschies 《AAPS PharmSciTech》2018,19(7):2843-2850
Despite extensive research in the field of gastroretentive dosage forms, this “holy grail” of oral drug delivery yet remained an unmet goal. Especially under fasting conditions, the reproducible retention of dosage forms in the stomach seems to be an impossible task. This is why such systems are often advised to be taken together with food. But also the postprandial motility can contribute significantly to the failure of gastroretentive dosage forms. To investigate the influence of postprandial pressure conditions on drug release from such systems, we used a novel in vitro dissolution tool, the dissolution stress test device. With the aid of this device, we simulated three different intragastric pressure profiles that may occur after postprandial intake. These transit scenarios were based on recently obtained, postprandial SmartPill® data. The tested systems, Glumetza® 1000 and Madopar® HBS 125, are marketed dosage forms that are based on different approaches to achieve proper gastric retention. All three transit scenarios revealed a highly pressure-sensitive drug release behavior, for both drugs. For Madopar® HBS 125, nearly complete drug release was observed even after early occurring pressures. Glumetza® 1000 seemed to be more resistant to these, most likely due to incomplete wetting of the system. On the contrary to these findings, data from standard dissolution tests using the paddle apparatus displayed controlled drug release for both systems for about 6 h. Based on these results, it can be doubted that established gastroretentive systems stay intact over a longer period of time, even under postprandial conditions. 相似文献
15.
Predicting different forms of collective behavior in human populations, as the outcome of individual attitudes and their mutual influence, is a question of major interest in social sciences. In particular, processes of opinion formation have been theoretically modeled on the basis of a formal similarity with the dynamics of certain physical systems, giving rise to an extensive collection of mathematical models amenable to numerical simulation or even to exact solution. Empirical ground for these models is however largely missing, which confine them to the level of mere metaphors of the real phenomena they aim at explaining. In this paper we present results of an experiment which quantifies the change in the opinions given by a subject on a set of specific matters under the influence of others. The setup is a variant of a recently proposed experiment, where the subject’s confidence on his or her opinion was evaluated as well. In our realization, which records the quantitative answers of 85 subjects to 20 questions before and after an influence event, the focus is put on characterizing the change in answers and confidence induced by such influence. Similarities and differences with the previous version of the experiment are highlighted. We find that confidence changes are to a large extent independent of any other recorded quantity, while opinion changes are strongly modulated by the original confidence. On the other hand, opinion changes are not influenced by the initial difference with the reference opinion. The typical time scales on which opinion varies are moreover substantially longer than those of confidence change. Experimental results are then used to estimate parameters for a dynamical agent-based model of opinion formation in a large population. In the context of the model, we study the convergence to full consensus and the effect of opinion leaders on the collective distribution of opinions. 相似文献
16.
The purpose of this study was to investigate the formulation variables influencing the drug release from the layered tablets
containing chitosan and xanthan gum as matrix component. Increasing the amount of lactose could diminish pH sensitive release
behavior of these matrix tablets. Effect of formulation variables on drug release from the prepared three-layered matrix tablets
was investigated. The amount of drug loading did not affect the drug release which was influenced by the hydrodynamic force
and the matrix composition. An increase in stirring rate correspondingly increased the release rate. Moreover, incorporation
of soluble diluents in core or barrier could enhance the drug release. Least square fitting the experimental dissolution data
to the mathematical expressions (power law, first order, Higuchi’s and zero order) was carried out to study the drug release
mechanism. Most dissolution profiles of the prepared three-layered tablets provided a better fit to zero order kinetic than
to first order kinetic and Higuchi’s equation. 相似文献
17.
Jianbin Zhang Yan Lv Shan Zhao Bing Wang Mingqian Tan Hongguo Xie Guojun Lv Xiaojun Ma 《AAPS PharmSciTech》2014,15(3):731-740
The objective of this study is to investigate the effect of lipolysis on the release of poorly water-soluble drug from SMEDDS in the perspective of drug core/shell location. For this purpose, four SMEDDS formulations with various core/shell properties were developed based on long-chain lipid or medium-chain lipid as well as different surfactant/oil ratios. Poorly water-soluble drugs, hymecromone and resveratrol, were significantly solubilized in all SMEDDS formulations and the diluted microemulsions. Fluorescence spectra analysis indicated that hymecromone was mainly located in the shell of microemulsions, while resveratrol was located in the core. The effect of lipolysis on the release rates of drugs with different core/shell locations were investigated by a modified in vitro drug release model. For the drug located in the shell, hymecromone, the release profiles were not affected during the lipolysis process and no significant differences were observed among four formulations. For the drug located in the core, resveratrol, the release rates were increased to various degrees depending on the extent of digestion. In conclusion, the drug core/shell location plays an important role for determining the effect of lipolysis on drug release from SMEDDS formulation. 相似文献
18.
Dongdong Li 《仿生工程学报(英文版)》2017,14(4)
Multifunctional materials combining fluorescence for drug delivery have been successfully developed by post grafted Aggregation-Induced Emission luminogens (AIEgens) onto Mesoporous Bioactive Glass (MBG).The synthesized hybrid materials combine porous structure of MBG and strong luminescence of AIEgens,showing ordered two-dimensional hexagonal mesostructure and strong blue emission.It is worth noting that the emission color of the hybrid materials can reversible cycled between blue and yellow by changing the pH value of water solution.More importantly,the hybrid materials exhibit a drastically improved apatite forming ability by soaked in Simulated Body Fluid (SBF).Furthermore,the hybrid materials can be used for site-specific delivery of doxorubicin hydrochloride (DOX) triggered by the mildly acidic pH environment,suggesting that the AIEgens functionalized mesoporous bioactive glass have great potential applications as drug-loading biomaterial for imaging guided therapy. 相似文献
19.
Rainfall-Induced Release of Fecal Coliforms and Other Manure Constituents: Comparison and Modeling
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A. K. Guber D. R. Shelton Y. A. Pachepsky A. M. Sadeghi L. J. Sikora 《Applied microbiology》2006,72(12):7531-7539
Modeling release of fecal coliforms is an important component of fate and transport simulations related to environmental water quality. Manure constituents other than fecal coliforms may serve as natural tracers of fecal contamination provided that their release from manure to runoff is similar to the fecal coliform release. The objectives of this work were to compare release of fecal coliforms (FC), chloride (Cl−), organic carbon (OC), and water-soluble phosphorus (P) from dissolving manure and to assess the performance of three models in describing the observed release. Bovine manure was applied on 0.5- by 0.3-m bare and vegetated subplots with 20% slope on sandy loam and clay loam soils. Concentrations of Cl−, FC, OC, and P were measured in runoff collected from troughs at the edges of the subplots at 5-min intervals during 1-h rainfall simulations. The one-parametric exponential model and two-parametric Vadas-Kleinman-Sharpley model and Bradford-Schijven model were fitted to the data. The Bradford-Schijven model had uncorrelated parameters, one of which was linearly related to the irrigation rate, and another parameter reflected the presence or the absence of vegetation. Kinetics of the FC release from manure was similar to the release kinetics of P and OC. The Bradford-Schijven model is recommended to simulate the release of manure constituents. 相似文献
20.
Praveen Sher Ganesh Ingavle Surendra Ponrathnam Pankaj Poddar Atmaram P. Pawar 《AAPS PharmSciTech》2009,10(2):547-558
The purpose of this research work was to explore an application of uncoated porous drug carrier prepared by single-step drug
adsorption for a delivery system based on integration of floating and pulsatile principles intended for chronotherapy. This
objective was achieved by utilizing 32 factorial design, solvent volume (X
1) and drug amount (X
2) as selected variables, for drug adsorption using solvents, methanol, and dichloromethane (DCM), of varying polarity. Nitrogen
adsorption (N2), scanning electron microscopy of cross-sections, and atomic force microscopy were done to study adsorption patterns and
their effect on release pattern. Drug release study was customized by performing for 6 h in acidic environment to mimic gastroretention
followed by basic environment akin to transit phase. Correlation between porous data from mercury and N2 adsorption was probably studied for the first time. Observed regression analysis values for pore volume, surface area, and
drug release indicated the influence of selected variables. Total release range in acidic medium was 12.77–24.57% for methanol,
8.79–15.26% for DCM, and final release of 69.45–92.23% for methanol, and 60.16–99.99% for DCM influenced by varying internal
geometries was observed. Present form of drug delivery system devoid of any additives/excipients influencing drug release
shows distinct behavior from other approaches/technologies in chronotherapy by (a) observing desired low drug release (8%)
in acidic medium, (b) overcoming the limitations of process variables caused by multiple formulation steps and different characteristic
polymers, (c) reducing time consumption due to single step process, and (d) extending as controlled/extended release. 相似文献