Viscoelastic Behavior of Drug-Loaded Polyurethane (original) (raw)
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Biostability and biological performance of a PDMS-based polyurethane for controlled drug release
Biomaterials, 2008
Polymers have been used to deliver therapeutic agents in a range of medical devices with drug eluting stents being the most widespread current application. Although polymers enable controlled release of a therapeutic agent, the polymeric surface has been reported to provide suboptimal biocompatibility and haemocompatibility and it has been suggested that currently used polymers may be at least partly responsible for the late adverse events observed in intravascular stent systems. In this study, the biostability and biological performance of a siloxane-based polyurethane elastomer (E2A) demonstrating excellent long-term biostability in the unloaded state was investigated following incorporation of a therapeutic agent. After implantation in an ovine model for 6 months, samples were assessed using SEM and ATR-FTIR to determine changes in the surface chemical structure and morphology of the materials and tensile testing was used to examine changes in bulk characteristics. Biological response was assessed using in vitro cytotoxicity testing and histological analysis. Results indicated that incorporation of 25 mg/g dexamethasone acetate (DexA) into the siloxane-based polyurethane resulted in no significant difference in the biostability and biocompatibility of the material. Some level of cytotoxic potential was exhibited which was believed to result from residual DexA leaching from samples during the extraction process. These findings suggest that E2A is a potential candidate for a delivery vehicle of therapeutic agents in implantable drug delivery applications.
Pharmaceutics, 2020
Following the huge clinical success of drug-eluting vascular stents, there is a significant interest in the development of drug-eluting stents for other applications, such as the treatment of gastrointestinal (GI) cancers. Central to this process is understanding how particular drugs are released from stent coatings, which to a large extent is controlled by drug-polymer interactions. Therefore, in this study we investigated the release of docetaxel (DTX) from a selection of non-degradable polymer films. DTX-polymer films were prepared at various loadings (1, 5 and 10% w/w) using three commercially available polymers including poly(dimethylsiloxane) (PSi), poly (ethylene-co-vinyl acetate) (PEVA) and Chronosil polyurethane (PU). The formulations were characterised using different techniques such as photoacoustic Fourier-transform infrared (PA-FTIR) spectrophotometry, X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The effect of DTX on the mechanical properties of ...
Polymers, Drug Release, and Drug-Eluting Stents
Journal of Interventional Cardiology, 2006
Implantable biomaterials mainly serve as physical support devices, carriers for bioactive molecules and guidance for tissue growth. For any application within or outside the cardiovascular area, biomaterials are subject to an extended set of requirements in order to establish safe application. These requirements mainly include acceptable biocompatibility and, if the material is to be degraded within the body, safe degradation characteristics. During degradation, biocompatible polymers are broken down into molecules that are metabolized and removed from the body via normal metabolic pathways. Major applications of these polymers include targeted drug delivery systems, resorbable sutures and orthopedic fixation devices. In the cardiovascular area they include biodegradable cardiovascular stents and drug-eluting stent (DES) coatings. This review focuses on general aspects of local drug delivery by implantable polymeric devices, with special emphasis on drug-eluting stents.
An Insight into the Structural Diversity and Clinical Applicability of Polyurethanes in Biomedicine
Polymers
Due to their mechanical properties, ranging from flexible to hard materials, polyurethanes (PUs) have been widely used in many industrial and biomedical applications. PUs’ characteristics, along with their biocompatibility, make them successful biomaterials for short and medium-duration applications. The morphology of PUs includes two structural phases: hard and soft segments. Their high mechanical resistance featuresare determined by the hard segment, while the elastomeric behaviour is established by the soft segment. The most important biomedical applications of PUs include antibacterial surfaces and catheters, blood oxygenators, dialysis devices, stents, cardiac valves, vascular prostheses, bioadhesives/surgical dressings/pressure-sensitive adhesives, drug delivery systems, tissue engineering scaffolds and electrospinning, nerve generation, pacemaker lead insulation and coatings for breast implants. The diversity of polyurethane properties, due to the ease of bulk and surface mod...
E3S Web of Conferences, 2021
With the aim of optimizing Drug Eluting Stents (DES), particular attention has been laid on computational methods of controlling the drug release profile among researchers. Consequently, various models and simulations are available in the literature. Nevertheless, validations based on biorelevant in-vitro trials are lacking. In the present study, a comparison of drug release from polyurethane samples between calculated results and experimental-data has been carried out. The calculation results are from a numerical simulation and a newly established mathematical model for reproducing the liberation kinetic. Different fluid flow rates and initial drug concentrations in polymer have been taken into account.
Material Parameters on Swelling and Drug Release
2016
In this study, we fabricated pH-sensitive polyvinylpyrrolidone/acrylic acid (PVP/AA) hydrogels by a free-radical polymerisation method with variation in the content of monomer, polymer and cross-linking agent. Swelling was performed in USP phosphate buffer solutions of pH 1.2, 5.5, 6.5 and 7.5 with constant ionic strength. Network structure was evaluated by different parameters and FTIR confirmed the formation of cross-linked hydrogels. X-ray crystallography showed molecular dispersion of tramadol HCl. A drug release study was carried out in phosphate buffer solutions of pH 1.2, 5.5 and 7.5 for selected samples. It was observed that swelling and drug release from hydrogels can be modified by changing composition and degree of cross-linking of the hydrogels under investigation. Swelling coefficient was high at higher pH values except for the one containing high PVP content. Drug release increased by increasing the pH of the medium and AA contents in hydrogels while increasing the concentration of cross-linking agent had the opposite effect. Analysis of the drug release mechanism revealed non-Fickian transport of tramadol from the hydrogels. Uniterms: Drugs/release. Hydrogels/pH sensitive. Polyvinylpyrrolidone-acrilic acid/hidrogels. Tramadol hydrochloride. Methylene bisacrylamide. Nesse estudo, preparamos hidrogéis de polivinilpirrolidona/ácido acrílico(PVP/AA), sensíveis ao pH, por meio de método de polimerização de radical livre, com variações no conteúdo de monômero, de polímero e de agente de ligação cruzada. O inchamento foi realizado em soluções tampão fosfato USP pH 1,2, 5,5, 6,5 e 7,5, com força iônica constante. A estrutura reticular foi avaliada por diferentes parâmetros e o FTIR confirmou a formação de hidrogéis de ligação cruzada. A cristalografia de raios X mostrou dispersão molecular do cloridrato de tramadol. Realizou-se estudo de liberação do fármaco em soluções tampão fosfato pH 1,2, 5,5 e 7,5 para amostras selecionadas. Observou-se que o inchamento e a liberação do fármaco dos hidrogéis podem ser modificados mudando-se a composição e o grau de ligação cruzada dos hidrogéis em estudo. O coeficiente de inchamento foi alto em pH mais altos, exceto para um deles com alto conteúdo de PVP. A liberação do fármaco aumentou com o aumento do pH do meio e do conteúdo em AA nos hidrogéis, enquanto que o aumento na concentração do agente de ligação cruzada apresentou efeito oposto. A análise do mecanismo de liberação do fármaco revelou transporte não Fickiano do tramadol dos hidrogéis. Unitermos: Fámacos/liberação. Hidrogéis/sensíveis ao pH. Polivinilpirrolidona-ácido acrílico/hidrogéis. Cloridrato de tramadol. Metileno bisacrilamida.
In vitro Interactions of Biomedical Polyurethanes with
2016
ABSTRACT: Three commercial medical-grade polyurethanes (PUs), a poly-ether-urethane (Pellethane), and two poly-carbonate-urethanes, the one aromatic (Bionate) and the other aliphatic (Chronoflex), were tested for macrophages and bacterial cells adhesion, in the presence or absence of adhesive plasma proteins. All the experiments were carried out on PUs films obtained by solvent casting. The wettability of these films was analysed by measuring static contact angles against water. The ability of the selected PUs to adsorb human fibronectin (Fn) and fibrinogen (Fbg) was checked by ELISA with biotin-labelled proteins. All PUs were able to adsorb Fn and Fbg (Fn>Fbg). Fn adsorption was in the order: Pellethane>Chronoflex>Bionate, the highest Fbg adsorption being detected onto Bionate (Bionate>Chronoflex>Pellethane). The human macrophagic line J111, and the two main bacterial strains responsible for infection in humans (Staphylococcus aureus Newman and Staphylococcus epiderm...
Long-term stable hydrogels for biorelevant dissolution testing of drug-eluting stents
Background: For the purpose of biorelevant dissolution testing hydrogels have recently been used to investigate release and distribution behavior of drugs released from specialized dosage forms such as drug-eluting stents. For stent testing using the vesselsimulating flow-through cell (vFTC) certain functional properties regarding life time of the used hydrogels such as hardening/softening, degradation/erosion and swelling/shrinkage during the time period of dissolution testing are of highest interest. Methods: Hydrogels composed of alginate, agar, agarose, polyacrylamide (PAA) and poly(vinyl alcohol) (PVA) were prepared using physical and chemical cross-linking methods. To characterize the mechanical stability of the test specimens stress-strain curves were recorded by texture analysis before and after perfusion in the vFTC for 28 days and Young's moduli were calculated. The surface morphology of the test specimens was examined using scanning electron microscopy. Water uptake upon incubation was determined. Results: Besides the previously established alginate gels, suitable hydrogels consisting of 2 wt% agar, 2 wt% agarose, 10 wt% PAA or 15 wt% PVA were identified. Comparison of stress-strain curves indicated a sample softening of reference as well as agar and a slight hardening of PVA whereas hardness of agarose and PAA remained unchanged. Young's moduli of agarose and PAA were almost unaffected after 28 days of perfusion. Swelling of PAA by 18 wt% and shrinkage of PVA by 14 wt% was observed compared to agar and agarose whose water uptake was negligibly small.
Journal of Pharmaceutical Analysis, 2017
It is a well-known fact that sirolimus (SRL) undergoes degradation process via hydrolysis in aqueous media, leading to incorrect assessment of drug amount and thus release characteristics of formulations. The main objective of the present study was to evaluate the effect of nonionic surfactants in media on invitro release profiles for sirolimus eluting stents (SES) coated with biodegradable polymeric matrix. Phosphate buffer and acetate buffer incorporating nonionic surfactants with varying concentrations were examined for adequate solubility and stability (by RP-HPLC). Good sink condition was achieved in phosphate buffer (at pH 4.0) with 1.0% Tween 20, 1.0% Brij 35% and 0.5% Brij 58. Hydrodynamic size (by DLS) and the micelle-water partition coefficient (P) with standard free energy of solubilization (ΔG s°) of drug were evaluated to get some understanding about the solubilization phenomena. About 80% of drug release during the period of 48 h was achieved in optimized drug release media which was 1.0% Tween 20 in phosphate buffer pH 4.0. The obtained accelerated SRL release profile in optimized medium correlated well with the real time in-vitro release in phosphate buffer (pH 7.4). Surface morphology changes (by SEM), changes in gravimetric weights and molecular weight change (by GPC) were examined before and after drug release to understand the drug release mechanism which explains that the polymer did not undergo degradation during the drug release.
Journal of Biomedical Materials Research Part A, 2008
Drug-eluting stents have proven superior to bare metal stents with lower restenosis rates. Local delivery of drugs from these stents is achieved in most cases with the help of biostable polymer coatings. However, since the polymer coating remains in the body well after all the drug is released, patients can potentially develop hypersensitivity to these polymers-leading to complications such as late-stent thrombosis. It is therefore important that the polymers are designed to be biocompatible and well tolerated by the body. The polymer coatings are also expected to be robust and provide good control over elution of the desired drug. This paper describes the devel-opment of a unique, proprietary polymer blend system, specially designed to meet these requirements. Mutually compatible, free-radical-initiated elastomeric polymers were designed to provide a robust coating and offer a steady, sustained release of the highly hydrophobic drug zotarolimus over an extended period. The polymer blend system is also well tolerated by the hydrophilic environment in vivo, as demonstrated through porcine studies.