药物从片状溶胀控制释放系统中释放的数学模型

本文对药物从可溶胀高分子材料中释放的机理进行了研究。建立了药物从可溶胀高分子材料中释放的数学模型。同时考虑溶剂渗透引起材料松驰膨胀，在模型中引入了刻画应力应变关系的弹性体方程。用摄动方法对方程进行了求解。利用溶胀界面数和扩散德伯拉数，对不同机理控制下的介质移动过程和药物释放过程，特别对材料松驰控制的过程进行了分析。     

药物从片状溶胀控制释放系统中释放的数学模型

本文对药物从可溶胀高分子材料中释放的机理进行了研究.建立了药物从可溶胀高分子材料中释放的数学模型.同时考虑溶剂渗透引起材料松驰膨胀,在模型中引入了刻画应力应变关系的弹性体方程.用摄动方法对方程进行了求解.利用溶胀界面数和扩散德伯拉数,对不同机理控制下的介质移动过程和药物释放过程,特别对材料松驰控制的过程进行了分析.     

药物从多孔骨架聚合物系统中控制释放的动力学模型

以组分的连续性方程为基础，建立了药物从多孔骨架聚合物系统中释放的数学模型。在模型中引入相对渗透速度来刻画药物释放过程中不同机理的影响，并用摄动方法对方程进行了求解。对所得结果进行了分析，特别对药物溶出机制控制的恒速释药现象进行了解释。     

药物从多孔骨架聚合物系统中恒速释放的机理

以组分的连续性方程为基础 ,建立了药物从多孔骨架聚合物系统中释放的数学模型。在模型中引入相对渗透速度来刻画药物释放过程中不同机理的影响。对药物从多孔骨架聚合物系统中non -Fickian扩散现象进行了研究 ,特别对药物溶出机制控制的恒速释药现象进行了解释。     

药物从玻璃状高分子材料中控制释放的机理研究

本文对药物从玻璃状高分子材料中扩散的机理进行了研究。将药物扩散方程和溶剂扩散方程结合起来。对药物采用Fick扩散定律得到扩散方程，考虑到溶剂的渗入引起材料粘弹性的改变，以及状态的改变对扩散的影响，将扩散方程与粘弹性模型结合起来构成扩散方程，最终得到一个能刻画药物从不同状态材料中扩散的模型。所得结果与实验结果相符。     

壳聚糖复合微胶囊的研制及在维生素D2可控释放中的应用

研究了以壳聚糖为核心壁材，以乙基纤维素为包衣材料的控制释放体系，以．维生素D2为模型药物，采用喷雾干燥方法对其进行有效包覆，并用乙基纤维进行了涂覆。对不同制备方法的微胶囊的形态及释放效果进行了测试。并探讨了制备过程中壳聚糖浓度，壳聚糖分子量，乙酸浓度，维生素D2负载量等因素对药物释放方式的影响。所制备的微胶囊不仅在肠液中具有显著的缓释效果。并且大大降低了维生素D2在胃中的释放，达到肠溶的目的。     

药物从玻璃状高分子材料中控制释放的机理研究

本文对药物从玻璃状高分子材料中扩散的机理进行了研究。将药物扩散方程和溶剂扩散方程结合起来。对药物采用Fick扩散定律得到扩散方程 ,考虑到溶剂的渗入引起材料粘弹性的改变 ,以及状态的改变对扩散的影响 ,将扩散方程与粘弹性模型结合起来构成扩散方程 ,最终得到一个能刻画药物从不同状态材料中扩散的模型。所得结果与实验结果相符     

盐酸四环素/α-TCP骨水泥载药体系的体外释放研究

对盐酸四环素/磷酸钙骨水泥药物释放体系进行了体外释放研究。XRD分析结果表明，一定含量的盐酸四环素的存在不会影响α-TCP的水化。在体外释放实验中，各种药物含量的载药体系均表现出了良好的缓释性能，持续释放时间超过1200h；由于盐酸四环素同磷酸钙的吸附与结合，当药物在体系中的含量发生改变时，释放控制机理发生改变。当抗生素在固相中含量较大时，药物释放速率以扩散控制为主。药物释放量满足时间平方根关系；当药物含量较低时，在释放前期，药物释放速率仍然以扩散控制为主；释放后期、药物分子从磷酸钙表面的解脱溶出与扩散对药物释放形成混合控制。     

用水凝胶作粘膜粘附剂和生物粘附剂材料

用生物粘附技术控制的药物释放的主要目的是在体内某一部位放置一个释放装置，使药物能在某一特定部位增加药物的吸收。生物粘附剂受聚合物释放装置的性质以及药物自身等生物环境协同作用的影响。释放部位的选择和装置的设计要根据药物的分子结构和药理学性质来考虑。本文将讨论几个以生物粘附剂释放为中心的研究命题。其次，简短的回顾一下生物粘附的各项技术。继之，讨论几个粘附机理。同时，对聚合物系统的主要机理，包括吸附和扩散作详细的介绍。     

用水凝胶作粘膜粘附剂和生物粘附剂材料

用生物粘附技术控制的药物释放的主要目的是在体内某一部位放置一个释放装置，使药物能在某一特定部位增加药物的吸收。生物粘附剂受聚合物释放装置的性质以及药物自身等生物环境协同作用的影响。释放部位的选择和位置的设计要根据药物的分子结构和药理学性质来考虑。本文将讨论几个以生物粘附剂释放为中心的研究命题。其次，简短的回顾一下生物粘附的各项技术。继之，讨论几个粘附机理。同时，对聚合物系统的主要机理，包括吸附和扩     

Modeling vancomycin release kinetics from microporous calcium phosphate ceramics comparing static and dynamic immersion conditions

The release kinetics of vancomycin from calcium phosphate dihydrate (brushite) matrices and polymer/brushite composites were compared using different fluid replacement regimes, a regular replacement (static conditions) and a continuous flow technique (dynamic conditions). The use of a constantly refreshed flowing resulted in a faster drug release due to a constantly high diffusion gradient between drug loaded matrix and the eluting medium. Drug release was modeled using the Weibull, Peppas and Higuchi equations. The results showed that drug liberation was diffusion controlled for the ceramics matrices, whereas ceramics/polymer composites led to a mixed diffusion and degradation controlled release mechanism. The continuous flow technique was for these materials responsible for a faster release due to an accelerated polymer degradation rate compared with the regular fluid replacement technique.     

Drug transport mechanisms and release kinetics from molecularly designed poly(acrylic acid-g-ethylene glycol) hydrogels

Controlled drug release devices of pH-sensitive, complexing poly(acrylic acid-g-ethylene glycol) (P(AA-g-EG)) hydrogels were prepared by free radical solution UV polymerization. The effects of hydrogel composition, polymerization conditions and surrounding environment on theophylline release kinetics and drug transport mechanisms were evaluated in these P(AA-g-EG) polymer networks. Release studies indicated a dependence of the theophylline release kinetics and diffusion coefficients on the hydrogel structure, polymerization conditions and pH of the environment. The theophylline transport mechanism was studied by fitting experimental data to five different model equations and calculating the corresponding parameters. The Akaike information criterion was also considered to elucidate the best-fit equation. Results indicated that in most release cases, the drug release mechanism was anomalous (non-Fickian). This indicates that such systems may, under certain conditions, provide release characteristics approaching zero-order release. The pH of the dissolution medium appeared to have a strong effect on the drug transport mechanism. At more basic pH values, Case II transport was observed, indicating a drug release mechanism highly influenced by macromolecular chain relaxation. The results obtained in this research work lead us to the conclusion that P(AA-g-EG) hydrogels can be successfully used as drug delivery systems. Their versatility to be designed with specifically tuned release properties renders these biomaterials promising pharmaceutical carriers for therapeutic agents.     

Characterization of a poly-epsilon-caprolactone polymeric drug delivery device built by selective laser sintering

Selective Laser Sintering (SLS), an established Rapid Prototyping (RP) process, is investigated for building controlled drug delivery devices (DDD). The drug and its matrix in a powder form were first mixed mechanically before being sintered on the SLS. Each cylindrical DDD is designed with a number of concentric rings separated from each other by a characteristic 'wall' created by the laser of the SLS. These rings act as diffusion obstacles to control the rate of release. Poly-epsilon-caprolactone (PCL) was used as the matrix and Methylene Blue (MB) as the drug model. Samples were built, characterized and tested for homogeneity using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared Spectrophotometry (FTIR). Experimental results show that the matrices fabricated are not affected by sintering and the polymer and drug model are evenly distributed throughout the matrix. The initial burst effect has been reduced by the increase of the numbers of rings. The linear curve using the Higuchi equation confirmed that the DDD matrix release profile is by diffusion. These results show that the DDD matrix design has promising potential for application in controlled release drug delivery.     

Sustained release of mitomycin-C from poly(DL-lactide) /poly(DL-lactide-co-glycolide) films

Mitomycin-C (MMC)-loaded poly(DL-lactide) (PLA)/poly(DL-lactide-co-glycolide) (PLGA) films which have different drug loading capacities and thicknesses were prepared by a solvent-evaporation technique. Degradation and release studies were conducted at 37 degrees C in pH 7.4 phosphate buffered saline. The results showed that both the rate and the percentage of released MMC increased as the glycolide content in the copolymer increased from 10 to 30% (w/w) and the drug load increased from 0.5 to 2 mg MMC per 300 mg of polymer. In contrast, they decreased depending upon increasing film thickness from 80 to 300 microm and polymer molecular weight. It was found that the drug release mechanism is diffusion-controlled according to a non-Fickian diffusion mechanism.     

Release of triamcinolone acetonide from mucoadhesive polymer composed of chitosan and poly(acrylic acid) in vitro

Transmucosal drug delivery (TMD) system using mucoadhesive polymer has been recently interested due to the rapid onset of action, high blood level, avoidance of the first-pass effect and the exposure of the drug to the gastrointestinal tract. A novel mucoadhesive polymer complex composed of chitosan and poly(acrylic acid) (PAA) was prepared by template polymerization of acrylic acid in the presence of chitosan for the TMD system. Triamcinolone acetonide (TAA) was loaded into the chitosan/PAA polymer complex film. TAA was evenly dispersed in chitosan, PAA polymer complex film without interaction with polymer complex. Release behavior of TAA from the mucoadhesive polymer film was dependent on time, pH, loading content of drug, and chitosan PAA ratio. The analysis of the drug release from the mucoadhesive film showed that TAA might be released from the chitosan/PAA polymer complex film through non-Fickian diffusion mechanism.     

Sustained release of mitomycin-C from poly(DL-lactide)/poly(DL-lactide-co-glycolide) films

Mitomycin-C (MMC)-loaded poly(DL-lactide) (PLA)/poly(DL-lactideco-glycolide) (PLGA) films which have different drug loading capacities and thicknesses were prepared by a solvent-evaporation technique. Degradation and release studies were conducted at 37°C in pH 7.4 phosphate buffered saline. The results showed that both the rate and the percentage of released MMC increased as the glycolide content in the copolymer increased from 10 to 30% (w/w) and the drug load increased from 0.5 to 2 mg MMC per 300 mg of polymer. In contrast, they decreased depending upon increasing film thickness from 80 to 300 μm and polymer molecular weight. It was found that the drug release mechanism is diffusion-controlled according to a non-Fickian diffusion mechanism.     

Present and future applications of biomaterials in controlled drug delivery systems

In this paper we review controlled drug release polymeric systems with emphasis on the polymer carriers as biomaterials. Polymer structure affects the diffusion mechanism and release behaviour of various drugs. Zero-order release can be achieved under certain conditions of polymer preparation and for specific geometric shapes. Physical, physicochemical, diffusive and toxicological tests for biomaterials used in controlled release applications are also discussed.     

Drug release from acrylic polymers via channels and cracks: in vitro studies with hydrocortisone

Release of hydrocortisone sodium succinate from acrylic resin was found to occur readily on elution in water at 37 degrees C. Increasing the degree of hydration of the acrylic resin by the addition of hydroxyethyl methacrylate impaired rather than enhanced the release of drug. The mechanism for the release of drug is believed to be surface release and drug dissolution into and diffusion via cracks and channels which are formed by incorporation of the drug, producing a 'drug-modified polymer'. Diffusion through the polymer matrix is believed to be insignificant. The results obtained are discussed in relation to this proposed model for drug release. A simple method for the manufacture of the core of an intra-oral insert capable of delivering drugs with MW greater than 400 for systemic and topical oral drug delivery is described.