Silver-particle-incorporated polyurethane films were evaluated for antimicrobial activity towards two different bacteria: Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Distributed silver particles sourced from silver nitrate, silver lactate and preformed silver nanoparticles were mixed with polyurethane (PU) and variously characterized by field emission scanning electron microscopy (FESEM), fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD) and contact angle measurement. Antibacterial activity against E.coli was confirmed for films loaded with 10% (w/w) AgNO3, 1% and 10% (w/w) Ag lactate and preformed Ag nanoparticles. All were active against S. aureus, but Ag nanoparticles loaded with PU had a minor effect. The apparent antibacterial performance of Ag lactate-loaded PU is better than other Ag ion-loaded films, revealed from the zone of inhibition study. The better performance of silver lactate-loaded PU was the likely result of a porous PU structure. FESEM and FTIR indicated direct interaction of silver with the PU backbone, and XRD patterns confirmed that face-centred cubic-type silver, representative of Ag metal, was present. Young’s modulus, tensile strength and the hardness of silver containing PU films were not adversely affected and possibly marginally increased with silver incorporation. Dynamic mechanical analysis (DMA) indicated greater thermal stability.
This paper presents time-resolved adsorption behavior of lysozyme, bovine serum albumin (BSA), and immunogamma globulin (IgG) onto a liquid crystal phthalocyanine surface and concentrates on the kinetic, viscoelastic variation, interfacial hydration, and structural details obtained by quartz crystal microbalance dissipating monitoring (QCM-D) technique with the Voigt model. The rate of adsorption for lysozyme is faster than that of BSA and IgG. The Freundlich model can explain the adsorption isotherm of lysozyme, whereas an exponential growth model can describe that of BSA and IgG. Layer surface coverage has been found to increase for all three proteins with significant variation in surface packing density and viscoelastic parameters within the investigated concentration range. The adsorbed IgG and BSA form soft, water-rich multilayers with large energy dissipation. The layer viscosity and shear modulus have been found to decrease as the protein hydration increases with concentration in these cases. On the other hand, lysozyme forms a rigid, negligibly hydrated multilayer with higher values of viscosity, shear modulus. Among three proteins, IgG is found to be a good adsorbent for liquid crystal surface comparing their theoretical monolayer surface coverage.
Polymeric membranes have been used as interfaces between implantable devices and biological tissues to operate as a protective barrier from water exchanging and to enhance biocompatibility. Polyurethanes have been used as biocompatible membranes for decades. In this study, copolymers of polyether urethane (PEU) with polydimethylsiloxane (PDMS) were synthesised with the goal of creating materials with low water permeability and high elasticity. PDMS was incorporated into polymer backbone as a part of the soft segment during polyurethane synthesis and physical properties as well as water permeability of resulting copolymer were studied in regard to PDMS content. Increase in PDMS content led to increase of microphase separation of the copolymer and corresponding increase in elastic modulus. Surface energy of the polymer was decreased by incorporating PDMS compared to unmodified PEU. PDMS in copolymer formed a hydrophobic surface which caused reduction in water permeability and water uptake of the membranes. Thus, PDMS containing polyurethane with its potent water resistant properties demonstrated a great promise for use as an implantable encapsulation material.
The detection sensitivity of silver nanoparticle (AgNP)-tagged goat immunoglobulin G (gIgG) microarrays was investigated by studying surface plasmon resonance (SPR) images captured in the visible wavelength range with the help of a Kretchmann-configured optical coupling set-up. The functionalization of anti-gIgG molecules on the AgNP surface was studied using transmission electron microscopy, photon correlation measurements and UV-visible absorption spectroscopy. A value of 1.3 Â 10 7 M 21 was obtained for the antibody-antigen binding constant by monitoring the binding events at a particular resonance wavelength. The detection limit of this SPR imaging instrument is 6.66 nM of gIgG achieved through signal enhancement by a factor of larger than 4 owing to nanoparticle tagging with the antibody.
Abstract:Medical polyurethanes have shown good bio-stability and mechanical properties and have been used as coating for implantable medical devices. However, despite their excellent properties, they are relatively permeable to liquid water and water vapour which is a drawback for electronic implant encapsulation. In this study polyether polyurethanes with different soft segment molecular weights were modified by incorporating isopropyl myristate (IPM), as a hydrophobic modifying agent, and the effect of IPM on water resistant and biocompatibility of membranes were investigated. IPM changed the surface properties of the polyurethane film and reduced its surface energy. Polyurethane films were found to be stable with IPM concentrations of 1-5 wt% based upon their chemistry; however it leached out in BSA at higher concentrations. Though, low concentrations of IPM reduced both liquid water and water vapour permeability; at higher IPM content liquid OPEN ACCESSPolymers 2010, 2 103 permeability did not improved significantly. In general, the polyurethane materials showed much lower water permeability compared with currently used silicone packaging material for electronic implants. In addition, cytotoxicity assessment of IPM containing polyurethanes showed no evidence of cytotoxcity up to 5 wt% IPM.
Polyurethanes have been widely used in medicine for coating and packaging implantable and other medical devices. Polyether-urethanes, in particular, have superior mechanical properties and are biocompatible, but in common with other medical materials they are susceptible to microbial film formation. In this study, polyether-urethane was end-capped with silver lactate and silver sulfadiazine functional groups to produce a bacterially resistant polymer without sacrificing the useful mechanical properties of the polyether-polyurethane. The silver ions were covalently incorporated into the polymer during chain extension of the prepolymer. The functionalized polymers were structurally characterized by light scattering, electron microscopy, NMR, FTIR and Raman spectroscopy. Mechanical properties, hydrophilicity, in vitro stability and antibacterial action of polymers were also investigated. Results indicate that both silver salts were successfully incorporated into the polymer structure without significant effect on mechanical properties, whilst conferring acceptable bacterial resistance.
Polyurethane films have potential applications in medicine, especially for packaging implantable medical devices. Although polyether-urethanes have superior mechanical properties and are biocompatible, achieving water resistance is still a challenge. Polyether based polyurethanes with two different molecular weights (PTMO1000, PTMO2000) were prepared from 4,4’-diphenylmethane diisocyanate and poly(tetra-methylene oxide). Polymer films were introduced using different concentrations (0.5-10 wt %) of isopropyl myristate lipid (IPM) as a non-toxic modifying agent. The physical and mechanical properties of these polymers were characterised using physical and spectroscopy techniques (FTIR, Raman, DSC, DMA, tensile testing). Water contact angle and water uptake of the membranes as a function of IPM concentration was also determined accordingly. The FTIR and Raman data indicate that IPM is dispersed in polyurethane at ≤ 2wt% and thermal analysis confirmed this miscibility to be dependent on soft segment length. Modified polymers showed increased tensile strength and failure strain as well as reduced water uptake by up to 24% at 1-2 wt% IPM.
The biostability of the polymer is one of the critical parameter to use them for biomaterial application. Polyurethane being one of the most compliant polymer but there are concerns regarding its resistance to degradation, particularly from hydrolysis and oxidation. The aim of this study is to synthesise a novel bioactive composite by creating a covalent linkage between polyurethane and nano-apatites and to analyse the in-vitro hydrolytic degradation of a series of newly synthesised polyurethane (PU) and polyurethane/nano-hydroxyapatite (PU/n-HA) composites. Nanoapatite powder was produced through sol-gel technique. A novel polyurethane composite material was prepared by chemically bonding the n-HA to the diisocyanate component in the polyurethane backbone by utilising solvent polymerisation. The concentration of nano-apatite was 5, 10, 15 and 20% wt/wt in polyurethane. Hydrolytic degradation of the PU and PU/n-HA composites were carried out both in deionised water and in phosphate buffer solution (PBS) having (pH 7.4) at 37 C for a predetermined time interval of 90 days. The PU and PU/n-HA composites were physically and chemically characterised by using contact angle measurement, weight loss, Fourier Transform Infrared spectroscopy couples with Photoacoustic Sampling Cell (FTIR-PAS), Raman Spectroscopy, X-ray Diffraction (XRD) and Scanning electron microscopy (SEM). These characterisations showed that with the addition of n-HA the composite exhibits hydrophobic behaviour and degradation rate reduces due to covalent linkage between n-HA and PU. Hence it has been concluded that the degradation rate of the newly developed PU/n-HA composites can be controlled, which helps in tailor making the biomaterial for specific applications.
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