Alginate/polyethylene glycol blend fibers and their properties for drug controlled release

Fibers of alginate and polyethylene glycol (PEG), with salicylic acid (SA) as model drug incorporated in different concentrations, were obtained by spinning their solution through a viscose-type spinneret into a coagulating bath containing aqueous CaCl(2) and ethanol. Chemical, morphological, and mechanical properties characterization were carried out, as well as the studies of the factors that influence the drug releasing from alginate/PEG fibers. These factors included the component ratio of alginate and PEG, the loaded amount of SA, the pH, and the ionic strength of the release solution and others. The best values of the tensile strength at 13.41 cN/tex and breaking elongation at 23.13% of blend fibers were obtained when the PEG content was 5 wt %; the water swelling ratio (WSR) of blend fibers increased as the composition of PEG was raised. The results of controlled release tests showed that the amount of SA released increased with an increase in the proportion of PEG present in the fiber. Moreover, the release rate of drug decreased as the amount of drug loaded in the fiber increased, but the cumulative release amount is increasing. The alginate/PEG fibers were also sensitive to pH and ionic strength. For pH 7.4 the drug release was faster compared to pH 1.0, being simultaneously accelerated by a higher ionic strength. All the results indicated that the alginate/PEG fiber was potentially useful in drug delivery systems.     

载表柔比星的壳聚糖纳米粒的制备及其特性研究

目的 制备经聚乙二醇修饰的壳聚糖纳米粒(PEG/CS NP),并负载表柔比星(EPI),研究载表柔比星的壳聚糖纳米粒(PEG/CS-EPI NP)体外释药性能.方法 应用阴离子凝聚法制备PEG/CS-EPI NP,透射电镜观察纳米粒的形态特征,激光粒度分析仪测定粒径大小,紫外分光光度法测定纳米粒的载EPI量,动态透析法考察载EPI纳米粒的体外释放特性.结果 当壳聚糖与三聚磷酸钠质量比为6∶1,壳聚糖与EPI质量比为8∶1时,制备的PEG/CS-EPI NP呈圆形或椭圆形,分散性良好,平均粒径(322.1±14.4)nm,载EPI量为(13.9±1.1)%,包封率(74.2±1.8)%,72 h累积释药率达(82.0±2.1)%.结论 采用阴离子凝聚法制备的PEG/CS-EPI NP形状规则、粒度分布均匀,具有较高包封率和较好缓释性能.     

Radiation synthesis of poly(ethylene glycol)/acrylic acid hydrogel as carrier for site specific drug delivery

pH-sensitive hydrogels were prepared from poly(ethylene glycol) (PEG) and acrylic acid (AAc) in aqueous solution employing gamma-radiation-induced copolymerization and crosslinking. The swelling behavior of the prepared hydrogels was determined by investigating the time and pH-dependent swelling of the (PEG/AAc) hydrogels of different PEG content. The effect of environmental parameters such as pH and ionic strength on the swelling kinetics was studied. The results not only show the dependence of the swelling indices on the pH value of the swelling medium but also show a clear dependence of the diffusion coefficient on the ionic strength of the medium. To estimate the ability of the prepared copolymer to be used as a colon-specific drug carrier, the release of ketoprofen was studied as a function of time at pH 1 and pH 7.     

Fibrous scaffolds loaded with protein prepared by blend or coaxial electrospinning

The aim of the present study was to fabricate polycaprolactone-based nanofibrous scaffolds with incorporated protein via either the blend or coaxial electrospinning technique. Both techniques were compared with respect to processing set-up and scaffold characteristics as well as the release kinetics and biological activity of the loaded protein. Bovine serum albumin was used as a model protein to determine release profiles, while alkaline phosphatase was used to determine protein activity after the electrospinning process. Coaxial electrospinning resulted in a uniform fiber morphology with a core–shell structure, and a homogeneous protein distribution throughout the core of the fibers. In contrast, blend electrospinning formed bead-like fibers with a heterogeneous protein distribution in the fibers. The coaxial scaffold exhibited more sustained release profiles than the comparative blend scaffold, and the additive poly(ethylene glycol) (PEG) in the coaxial scaffold accelerated protein release. Both electrospinning processes decreased the biological activity of the incorporated protein, but coaxial electrospinning with PEG as an additive showed up to 75% preservation of the initial biological activity. Thus, coaxial electrospinning was demonstrated to be superior to blend electrospinning for the preparation of nanofibrous scaffolds with a uniform fibrous structure and protein distribution and sustained protein release kinetics as well as high preservation of the protein activity.     

Release characteristics and processing-structure-performance relationship of electro-spinning curcumin-loaded polyethersulfone based porous ultrafine fibers

Abstract

Polymeric porous ultrafine fibers with different structures as drug carrier could be facilely prepared. However, the drug release characteristics and relevant mechanism of different structural porous ultrafine fibers were not well studied. In the present work, different structural Poly-Ether-Sulfone (PES) based porous ultrafine fibers, namely PES, PES/Poly-Ethylene-Glycol (PEG) and PES/Water were prepared by electro-spinning. Curcumin was chosen as drug model loaded in these fibers. Investigation of curcumin release characteristics was carried out by the total immersion in buffer solution. The surface and inner structure of PES based ultrafine fibers were studied by scanning electron microscopy (SEM) in detail. It is found that there is significant difference in the accumulate release amount and release rate with similar structure. About 92.5% of curcumin released within 600?min for PES/PEG ultrafine fibers and only 58.9% of curcumin flowed out from PES with 1000?min. In order to discuss the fact of this phenomenon, the development structure of PES based porous ultrafine fibers was studied with curcumin release. The results indicated that the curcumin release was directly involved with the structure. For PES/PEG, curcumin around the surface layer released in advance. And then, some penetrable structure emerged with PEG dissolving in the buffer solution, which result in larger specific surface area and more embedded curcumin from the interior structure of the ultrafine fibers diffusing out. For the others, curcumin release only through its own pores of ultrafine fibers. Finally, the processing-structure-performance relationship of PES based porous ultrafine fibers were confirmed by the diversity of porosity and contact angle. The research results demonstrate that PES based porous ultrafine fibers have the potential to be used as drug carrier in the drug delivery according to the practical clinical requirements.     

Interpolymer complexes of poly(acrylic acid) and chitosan: influence of the ionic hydrogel-forming medium

Non-covalent polyionic complexes were developed for localized antibiotic delivery in the stomach. Freeze-dried interpolymer complexes based on polyacrylic acid (PAA) and chitosan (CS) were prepared in a wide range of copolymer compositions by dissolving both polymers in acidic conditions. The influence of hydrogel-forming medium on the swelling and drug release was evaluated. The properties of these complexes were investigated by using scanning electron microscopy, dynamic swelling/eroding and release experiments in enzyme-free simulated gastric fluid (SGF). The electrostatic polymer/polymer interactions generate polyionic complexes with different porous structures. In a low pH environment, the separation of both polymer chains augmented as the amount of cationic and carboxilic groups increased within the network. However, the presence of higher amount of ions in the hydrogel-forming medium produced a network collapse, decreasing the maximum swelling ratio in SGF. PAA:CS:A (1:2.5:2)-1.75 M complexes released around 54% and 71% of the amoxicillin in 1 and 2 h, respectively, in acidic conditions. A faster drug release from this interpolymer complex was observed when the ionic strength of the hydrogel-forming medium increased. Complexes with a high amount of both polymer chains within the network, PAA:CS:A(2.5:5:2), showed a suitable amoxicillin release without being affected by an increased amount of ions in the hydrogel-forming medium. These freeze-dried interpolymer complexes could serve as potential candidates for amoxicillin delivery in an acidic enviroment.     

Controlled release of DNA from poly(vinylpyrrolidone) capsules using cleavable linkers

The design of polymer carriers with tunable degradation and cargo release is fundamental for applications in drug and gene delivery. In this study, we report low-fouling poly(N-vinyl pyrrolidone) (PVPON) capsules assembled via hydrogen bonding and stabilized using covalent cross-linking. We first investigated the effects of pH and ionic strength to optimize the assembly conditions. A model therapeutic cargo (plasmid DNA) was then loaded in the capsules and used for encapsulation and release studies. Two bisazide cross-linkers that contain a disulfide bond, termed PEG? (poly(ethylene glycol)) and PEG(16), were employed to stabilize the multilayer films, and used to tune the degradation and cargo release behavior of the capsules in simulated cytoplasmic conditions. The results suggest that PEG?-stabilized capsules were more efficiently cross-linked, and hence displayed higher plasmid encapsulation. Consequently, the capsules cross-linked with PEG? also showed a two-fold reduction in degradation rate. This ability to achieve controlled carrier degradation and cargo release makes these capsules of potential interest for drug and gene delivery.     

Core-sheath structured fibers with pDNA polyplex loadings for the optimal release profile and transfection efficiency as potential tissue engineering scaffolds

Emulsion electrospinning was initially applied to prepare core-sheath structured fibers with a core loading of pDNA or pDNA polyplexes inside a fiber sheath of poly(DL-lactide)-poly(ethylene glycol) (PELA). The inclusion of poly(ethylene imine) (PEI) and poly(ethylene glycol) (PEG) were expected to modulate the release profiles and achieve a balance between cytotoxicity and transfection efficiency. The core-sheath fibers enhance the structural integrity and maintain the biological activity of pDNA during the electrospinning process, incubation in release buffer and enzyme digestion. The addition of hydrophilic PEI into the fiber matrix accelerates pDNA release, while the encapsulation of pDNA polyplexes within the fibers led to no further release after an initial burst. However, sustained release of pDNA polyplexes has been achieved through PEG incorporation, and the effective release lifetime can be controlled between 6 and 25 days, dependent on the amount loaded and the molecular weight of PEG. Higher N/P ratios of PEI to DNA result in lower cell attachment, while cell viability is dependent on the effective concentration of pDNA polyplexes released from the fibers. While no apparent transfection is detected for pDNA-loaded PELA fibers, PEG incorporation into fibers containing pDNA polyplexes leads to over an order of magnitude increase in the transfection efficiency. pDNA polyplex-loaded fibers containing 10% PEG show the best performance in balancing transfection efficiency and cell viability. It is suggested that electrospun core-sheath fibers integrated with DNA condensation techniques provide the potential to produce inductive tissue engineering scaffolds able to manipulate the desired signals at effective levels within the local tissue microenvironment.     

Cell proliferation and controlled drug release studies of nanohybrids based on chitosan-g-lactic acid and montmorillonite

The present paper reveals the potential uses of novel hybrids of chitosan-g-lactic acid and sodium montmorillonite (MMT) in controlled drug delivery and tissue engineering applications. The drug-loaded novel nanohybrid films and porous scaffolds have been prepared by solvent casting and freeze-drying of the grafted polymer solution, respectively. Sodium Ibuprofen was loaded into nanohybrids of chitosan-g-lactic acid/sodium montmorillonite (CS-g-LA/MMT). Grafting of lactic acid and the drug loading were characterized by Fourier transform infrared spectroscopy. Formation of intercalated nanocomposites was confirmed by X-ray diffraction. Mechanical properties measurements have shown improvement in modulus and strength with expense of elongation by MMT reinforcement. The nanohybrids were found to be stable regardless of pH of the medium. The cell proliferation profile also shows that prepared nanohybrids are biocompatible. MMT reinforcement was found to control the drug (Ibuprofen) release rate in phosphate buffer saline solution (pH 7.4). MMT clay is therefore a viable additive for formulating sustained drug delivery systems based on lactic acid grafted chitosan.     

Effects of preparative parameters on the properties of chitosan hydrogel beads containing Candida rugosa lipase

The influences of the pH, tripolyphosphate (TPP) concentration, and ionic strength of the gelling medium on the entrapment efficiency, release, and activity of lipase in chitosan hydrogel beads were studied. A solution of Candida rugosa lipase was prepared in a 1.5% w/v chitosan and 1% (v/v) acetic acid medium, and dropped into a TPP solution. Release of lipase in pH 7.2 Tris buffer was monitored over 36 h using the micro BCA protein assay. The activity of the entrapped enzyme was assayed using the Sigma lipase activity method. Following preliminary studies, an experimental design was followed to develop mathematical models that describe bead characteristics as functions of the pH and the TPP concentration in the gelling medium. The pH and the TPP concentration each had an effect on the entrapment, retention, and activity of lipase. Entrapped lipase retained a high degree of activity in multiple reactions. The ionic strength, in the range studied, exerted a minimal effect on bead characteristics. Statistical analysis allowed optimization within the factor space with respect to maximizing the enzyme entrapment efficiency and activity, and also minimizing the amount released after 36 h in the Tris buffer.     

Changes in cisplatin delivery due to surface-coated poly (lactic acid)-poly(epsilon-caprolactone) microspheres

Smooth muscle cell proliferation plays a major role in the genesis of restenosis after angioplasty or vascular injury. Local delivery of agents capable of modulating vascular responses, have the potential to prevent restenosis. However, the development of injectable microspheres for sustained drug delivery to the arterial wall is a major challenge. We demonstrated the possibility of entrapping an antiproliferative agent, cisplatin, in a series of surface coated biodegradable microspheres composed of poly(lactic acid)poly(caprolactone) blends, with a mean diameter of 2-10 pm. The microspheres were surface coated with poly ethylene glycol (PEG), chitosan (Chit), or alginate (Alg). A solution of cisplatin and a 50:50 blend of polylactic acid (PLA)-polycaprolactone (PCL) dissolved in acetone-dichloromethane mixture was poured into an aqueous solution of PEG (or polyvinyl alcohol or Chit or Alg) with stirring using a high speed homogenizer, for the formation of microspheres. Cisplatin recovery in microspheres ranged from 25-45% depending on the emulsification system used for the preparations. Scanning electron microscopy revealed that the PLA-PCL microspheres were spherical in shape and had a smooth surface texture. The amount of drug release was much higher initially (20-30%), this was followed by a constant slow-release profile for a 30-day period of study. It has been found that drug release depends on the amount of entrapped drug, on the presence of extra cisplatin in the dispensing phase, and on the polymer coatings. This PEG or Alg-coated PLA/PCL microsphere formulation may have potential for the targeted delivery of antiproliferative agents to treat restenosis.     

Paclitaxel-eluting composite fibers: drug release and tensile mechanical properties

New core/shell fiber structures loaded with paclitaxel were developed and studied. These composite fibers are ideal for forming thin, delicate, biomedically important structures for various applications. Possible applications include fiber-based endovascular stents that mechanically support blood vessels while delivering drugs for preventing restenosis directly to the blood vesel wall, or drug delivery systems for treatment of cancer. The core/shell fiber structures were formed by "coating" dense core fibers with porous paclitaxel-containing poly(DL-lactic-co-glycolic acid) (PDLGA) structures. Shell preparation ("coating") was performed by freeze-drying water in oil emulsions. The present study focused on the effects of the emulsion's formulation (composition) and processing conditions on the paclitaxel release profile and on the fibers' tensile mechanical properties. In general, the porous PDLGA shell released approximately 40% of the paclitaxel, with most of the release occurring during the first 30 days. The main release mechanism during the tested period is diffusion, rather than polymer degradation. The release rate and quantity increased with increased drug content or decreased polymer content, whereas the organic:aqueous phase ratio had practically no effect on the release profile. These new composite fibers are strong and flexible enough to be used as basic elements for stents. We demonstrated that proper selection of processing conditions based on kinetic and thermodynamic considerations can yield polymer/drug systems with the desired drug release behavior and good mechanical properties.     

Ampicillin-incorporated alginate-chitosan fibers from microfluidic spinning and for vitro release

The fibrous drug-loading capability, degradation profile, drug release behavior and mechanical performance were found to be controlled by regulating the amount of IPA and chitosan, which delayed the degradable time-scale and improved the drug loading capacity. Six types of alginate fibers were spun by combining two distinct core flows with deionized water-based, ethanol-based and isopropyl alcohol-based sheath fluid, respectively. The as prepared fibers were analyzed and compared by the characterization of SEM, mass loss, ICP, FTIR, XRD, UV, mechanics performance testing and antibacterial activity tests. The results showed that fibers in the isopropyl alcohol with low polarity sheath flow exhibited higher-ordered structure. Also, incorporation of chitosan for the core stream strengthened the degree of crosslinking among the molecular chain, and thus made the fiber entrapped more drug of ampicillin molecular. The fibers, possessing superior mechanical properties, preferable drug loading capability, more prolonged drug release behavior and outstanding antibiotic activity, may offer a promising candidate for biomaterials, such as fibrous drug carrier and antibacterial sutures.     

Controlled release of transforming growth factor beta1 from biodegradable polymer microparticles

Recombinant human transforming growth factor beta1 (TGF-beta1) was incorporated into biodegradable microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) at 6 ng/1 mg microparticles. Fluorescein isothiocynate labeled bovine serum albumin (FITC-BSA) was coencapsulated as a porogen at 4 microg/1 mg of microparticles. The effects of PEG content (0, 1, or 5 wt %) and buffer pH (3, 5, or 7.4) on the protein release kinetics and the degradation of PLGA were determined in vitro for up to 28 days. The entrapment yield of TGF-beta1 was 83.4 +/- 13.1 and 54.2 +/- 12.1% for PEG contents of 0 and 5%, respectively. The FITC-BSA and TGF-beta1 were both released in a multiphasic fashion including an initial burst effect. Increasing the PEG content resulted in the decreased cumulative mass of released proteins. By day 28, 3.8 +/- 0. 1 and 2.8 +/- 0.3 microg (based on 1 mg microparticles) of loaded FITC-BSA and 3.4 +/- 0.2 and 2.2 +/- 0.3 ng of loaded TGF-beta1 were released into pH 7.4 phosphate buffered saline (PBS) from microparticles with 0 and 5% PEG, respectively. Aggregation of FITC-BSA occurred at lower buffer pH, which led to decreased release rates of both proteins. For microparticles with 5% PEG, 2.3 +/- 0.1 microg of FITC-BSA and 2.0 +/- 0.2 ng of TGF-beta1 were released in pH 7.4 buffer after 28 days, while only 1.7 +/- 0.3 microg and 1.3 +/- 0.4 ng of the corresponding proteins were released in pH 3 buffer. The degradation of PLGA was also enhanced at 5% PEG content, which was significantly accelerated at acidic pH conditions. The calculated half-lives of PLGA were 20.3 +/- 0.9 and 15.9 +/- 1.2 days for PEG contents of 0 and 5%, respectively, in pH 7.4 PBS and 14.8 +/- 0.4 and 5.5 +/- 0.1 days for 5% PEG in pH 7.4 and 3 buffers, respectively. These results suggest that PLGA/PEG blend microparticles are useful as delivery vehicles for controlled release of growth factors.     

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.     

Xanthan gum as a carrier for controlled release of drugs

Systems based on xanthan gum matrix containing 1%, 2% and 5% salicylic acid were prepared and studied as controlled release devices. Swelling of the matrix in distilled water and buffer solutions showed that the ionic strength of the liquid has a strong effect on the sorptive properties of the matrix. From the release experiments, conducted in distilled water at 37 +/- 0.5 degrees C, it was found that the drug delivery process was accomplished within the first 10 hours after immersion and salicylic acid was always released via a non-Fickian transport. The phenomenon can be described by a release exponent (n) in the area of 0.77 independently of the initial concentration of salicylic acid in the xanthan matrix. These results can be interpreted taking into consideration the dimensional and physical changes of the polymeric matrix during swelling.     

Multifunctional superparamagnetic nanocarriers with folate-mediated and pH-responsive targeting properties for anticancer drug delivery

Multifunctional nanocarriers with multilayer core-shell architecture were prepared by coating superparamagnetic Fe(3)O(4) nanoparticle cores with a mixture of the triblock copolymer methoxy poly(ethylene glycol)-b-poly(methacrylic acid-co-n-butyl methacrylate)-b-poly(glycerol monomethacrylate) and the folate-conjugated block copolymer folate-poly(ethylene glycol)-b-poly(glycerol monomethacrylate). The model anticancer agent adriamycin (ADR), containing an amine group and a hydrophobic moiety, was loaded into the nanocarrier at pH 7.4 by ionic bonding and hydrophobic interactions. The release rate of the loaded drug molecules was slow at pH 7.4 (i.e. mimicking the blood environment) but increased significantly at acidic pH (i.e. mimicking endosome/lysosome conditions). Acid-triggered drug release resulted from the polycarboxylate protonation of poly(methacrylic acid), which broke the ionic bond between the carrier and ADR. Cellular uptake by folate receptor-overexpressing HeLa cells of the folate-conjugated ADR-loaded nanoparticles was higher than that of non-folated-conjugated nanoparticles. Thus, folate conjugation significantly increased nanoparticle cytotoxicity. These findings show the potential viability of a folate-targeting, pH-responsive nanocarrier for amine-containing anticancer drugs.     

载盐酸四环素壳聚糖缓释膜的制备

背景：壳聚糖具有良好的生物相容性、生物可降解性及较好的抗菌活性。 目的：使用流延法制备载有不同盐酸四环素的壳聚糖载药纳米纤维膜,观察其缓释性能和抑菌性能。 方法：采用流延法制备厚度为0.03 mm的载有不同含量(0,3%,5%,10%,20%)盐酸四环素的壳聚糖载药缓释膜,测定载药率,绘制盐酸四环素缓释曲线。分别用液体培养和固体培养检测载药缓释膜的体外抑菌性能,用磷酸盐缓冲液观察载药缓释膜的降解性能。 结果与结论：随盐酸四环素含量的增加,缓释膜载药率降低,突释量增大。载药壳聚糖膜可有效抑制金黄色葡萄球菌的生长,并随盐酸四环素含量的增加,抑菌效果提高,当盐酸四环素含量超过10%时,载药壳聚糖膜抑菌率的变化不明显。盐酸四环素的加入加快了壳聚糖膜降解,并随着盐酸四环素含量的增加,降解速率增大,当盐酸四环素载药量超过10%时,降解可在8 d内完成。相比较得出,盐酸四环素含量在10%时,在疗效和性价比上是较好的选择。     

Electrospun chitosan-P(LLA-CL) nanofibers for biomimetic extracellular matrix

Chitosan-poly(L-lactic acid-co-epsilon-caprolactone)(50:50) (P(LLA-CL)) (CS/P(LLA-CL)) blends were electrospun into nanofibers using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents. Chitosan, which is difficult to electrospin into nanofibers, could be easily electrospun into nanofibers with addition of a small portion of P(LLA-CL). The fiber diameter depended on both the polymer concentration and the blend ratio of chitosan to P(LLA-CL). The average fiber diameter increased with increasing polymer concentration and decreasing the blend ratio of chitosan to P(LLA-CL). X-ray diffractometry (XRD) and Fourier-transform infrared (FT-IR) spectra were measured to characterize blended nanofibers. The porosity of CS/P(LLA-CL) nanofiber mats increased with increasing the weight ratio of chitosan to P(LLA-CL), while both the tensile strength and the ultimate strain increased with increasing P(LLA-CL) ratio. Fibroblast cell growth on nanofiber mats were investigated with MTT assay and scanning electron microscope (SEM) observation. The highest cell proliferation was observed on the nanofiber mats when the weight ratio of chitosan to P(LLA-CL) was 1:2. As SEM images shown, fibroblast cells showed a polygonal shape on blend nanofiber mats and migrated into the nanofiber mats.     

Drug release from a porous ion-exchange membrane in vitro.

The effect of environmental ionic strength on the rate of drug release from a cation exchange membrane was evaluated. Cationic propranolol-HCl, timolol, sotalol-HCl, atenolol and dexmedetomidine-HCl and neutral diazepam were adsorbed onto a porous poly(vinylidene fluoride) (PVDF) membrane that was grafted with bioadhesive poly(acrylic acid) chains (PAA-PVDF). Despite its porosity, the PAA-PVDF membrane acted as a cation exchange membrane. The release of adsorbed drug from the PAA-PVDF membrane was investigated by using a USP rotating basket apparatus. Adsorption of cationic drugs onto the PAA-PVDF membrane tended to increase with increasing lipophilicity of the drug. A decrease in the ionic strength of the adsorption medium increased the amount of the cationic drugs adsorbed onto the membrane, but had no effect on diazepam adsorption. The release of cationic drugs from the PAA-PVDF membrane was greatly affected by the ionic strength of both the adsorption medium and the dissolution medium, while ionic strengths did not affect diazepam release. Our results suggest that the ionic strength of both the adsorption and dissolution media substantially affects the release rate of a drug that has been adsorbed onto the ion exchange membrane, primarily via electrostatic interactions, while ionic strength has no effect on the release of a drug which has been adsorbed onto the membrane via non-electrostatic forces.