Preparation of semi-interpenetrating polymer networks composed of chitosan and poloxamer

Through semi-interpenetration of polymer networks with poloxamer, mechanical properties of chitosan (CS) sponge were increased for wound dressing application. Synthesis of poloxamer macromer was confirmed by proton nuclear magnetic resonance (1H NMR) spectra. Possible interactions between CS and poloxamer in semi-interpenetrating polymer networks (SIPNs), and changes in crystalline structures of both polymers were evaluated by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. Swelling behavior, thermal analysis, mechanical properties, and morphology of SIPNs were studied by thermal gravimetric analysis, differential scanning calorimetry (DSC), compressive modulus measurement, and scanning electron microscopy (SEM), respectively. Preparation of poloxamer macromer, and intermolecular hydrogen bonding between CS and poloxamer were confirmed by NMR and FTIR, respectively. Melting temperature of poloxamer in SIPNs decreased due to prevention of crystallization by incorporation of CS. Formation of SIPNs with poloxamer and increasing poloxamer content in CS/poloxamer SIPNs increased mechanical strength of CS sponge compared with CS/poloxamer blend. Formation of SIPNs with poloxamer remarkably increased water content of CS due to hydrophilicity of CS and poloxamer. These results suggest CS/poloxamer sponges prepared by SIPNs method have good possibility for wound dressing application owing to rapid water adsorption, high mechanical strength, and interconnected cross-sectional morphology of SIPNs.     

Preparation of semi-interpenetrating polymer networks composed of silk fibroin and poloxamer macromer

A system was designed to utilize silk fibroin (SF) as a matrix for wound dressing. For this system, we prepared a sponge type of porous semi-interpenetrating networks (SIPNs) hydrogel composed of SF and poloxamer 407 macromer to enhance the mechanical and functional properties of SF. The thermal and mechanical properties of the hydrogels as well as their swelling behaviors were studied by means of differential scanning calorimetry, compressive modulus measurement, and gravimetric method, respectively. The morphology and crystalline structure of these SIPN hydrogels were also investigated by scanning electron microscopy (SEM) and wide-angle diffractometry, respectively. Conformational change of SF from random coil to beta-sheet structure was accelerated by formation of SIPNs with poloxamer. The melting temperature of poloxamer in the SIPNs decreased due to the prevention of crystallization by the incorporation of SF. The mechanical strength of SIPNs hydrogel was much higher than those of SF itself or SF/poloxamer blend and increased with the poloxamer content. The equilibrium water content of SF was remarkably increased by formation of SIPNs with poloxamer due to the hydrophilicity of poloxamer. The crystallinity and morphology of SIPNs hydrogel were affected by SIPNs hydrogel composition.     

Thermosensitive transparent semi-interpenetrating polymer networks for wound dressing and cell adhesion control

Thermosensitive, transparent, and flexible semi-interpenetrating polymer networks (semi-IPNs) composed of segmented polyurethane urea/poly(N-isopropylacrylamide) (SPUU/ PNiPAAm) were new class of materials, which holds promise for its potential use as wound dressings. A series of semi-IPNs, obtained via thermal initiated polymerization of NiPAAm, were characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR), dynamic viscoelastic measurements, wide-angle X-ray diffraction (WAXD), and mechanical properties. The resulting semi-IPNs were also investigated for their dynamic water contact angles, thermodynamic interaction parameters, in vitro drug release, and cell adhesion and detachment. The semi-IPNs with differing compositions possess good mechanical properties in both dry and hydrated states. In addition, NIH3T3 fibroblasts can attach to and detach from these semi-IPN films with varying temperature. In addition, these film extracts do not show significant cytotoxicity. Therefore, these materials have great potential for the construction of a new generation of dressings and cell transplantation for wound healing.     

Hemoglobin recognition by imprinting in semi-interpenetrating polymer network hydrogel based on polyacrylamide and chitosan

Semi-interpenetrating polymer network (semi-IPN) hydrogel was prepared to recognize hemoglobin, by molecularly imprinted method, in the mild aqueous media of chitosan and acrylamide in the presence of N,N'-methylenebisacrylamide as the cross-linking agent. The hydrogel obtained has been investigated by using thermal analysis, X-ray diffraction, differential scanning calorimetry (DSC), and environmental scanning electron microscope (ESEM). Langmuir analysis showed that an equal class of adsorption was formed in the hydrogel, and the adsorption equilibrium constant and the maximum adsorption capacity were evaluated to be 4.27 g/mL and 36.53 mg/g wet hydrogel, respectively. The imprinted semi-IPN hydrogel has a much higher adsorption capacity for hemoglobin than the nonimprinted hydrogel with the same chemical composition and also has a higher selectivity for the imprinted molecule.     

Effects of molecular weight on the miscibility and properties of polyurethane/benzyl starch semi-interpenetrating polymer networks

We successfully prepared a series of semi-interpenetrating polymer networks (semi-IPNs) from castor oil-based polyurethane (PU) and 20 wt % benzyl starch (BS) with different weight-average molecular weights (M(w)), coded as the PU/BS films. The M(w) values of a series of BSs were determined by size-exclusion chromatography combined with laser light scattering. The effects of the BS M(w) on the miscibility and properties of the resulting PU/BS films were investigated using reflection Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, scanning electron microscopy, optical microscopy, ultraviolet-visible spectroscopy, and tensile testing. The results revealed that the PU/BS films possessed much higher optical transmittance and tensile strength than the pure PU film. Interestingly, with a decrease of the BS M(w) from 1.69 x 10(7) to 5.70 x 10(5), the optical transmittance, tensile strength, and elongation at break of the PU/BS films increased from 82% to 89%, from 11.7 to 15.7 MPa, and from 121% to 180%, respectively. Therefore, the M(w) of BS plays an important role in the improvement of the miscibility and properties of the semi-IPN materials. On the basis of the analysis of the miscibility and the morphology of the PU/BS films, the interaction between the PU and the BS with relatively low M(w) was stronger than that with high M(w).     

Multifunctional poly(ethylene glycol) semi-interpenetrating polymer networks as highly selective adhesive substrates for bioadhesive peptide grafting

Novel artificial extracellular matrices were synthesized in the form of semi-interpenetrating polymer networks containing copolymers of poly(ethylene glycol) and acrylic acid (PEG-co-AA) grafted with synthetic bioadhesive peptides onto exposed carboxylic acid moieties. These substrates were very resistant to cell adhesion, but when they were grafted with adhesive peptides they were highly biospecific in their ability to support cell adhesion. Extensive preadsorption of adhesive proteins or peptides did not render these materials cell adhesive; yet covalent grafting of adhesive peptides did render these materials highly cell adhesive even in the absence of serum proteins. Polymer networks containing immobilized PEG-co-AA were grafted with peptides at densities of 475 +/- 40 pmol/cm(2). Polymer networks containing immobilized PEG-co-AA N-terminally grafted with GRGDS supported cell adhesion efficiencies of 42 +/- 4% 4 h after seeding and became confluent after 12 h. These cells displayed cell spreading and cytoskeletal grafted with inactive control peptides (GRDGS, GRGES, or no peptide) supported cell adhesion efficiencies of 0 +/- 0%, even when challenged with high seeding densities (to 100,000 cell/cm(2)) over 14 days. These polymer networks are suitable substrates to investigate in vitro cell-surface interactions in the presence of serum proteins without nonspecific protein adsorption adhesion signals other than those immobilized for study.     

Synthesis of hydroxypropylcellulose-poly(acrylic acid) particles with semi-interpenetrating polymer network structure

To develop a novel type of semi-IPN particles using biocompatible materials, hydroxypropylcellulose-poly(acrylic acid) (HPC-PAA) particles with semi-interpenetrating polymer network structure and a porosity-structural surface were prepared by direct polymerization of acrylic acid monomer in the reaction system comprised of HPC and AA monomer and N,N'-methylenebisacrylamide (MBAAm). The properties of HPC-PAA gel particles were characterized by dynamic light scattering, FT-IR, transmission electron microscopy, and atomic force microscope. It is found that the formation of HPC-PAA gel particles is driven by the hydrogen bonding interaction between proton-donating PAA and proton-accepting HPC. These HPC-PAA gel particles exhibit thermo and pH dual-responsive behaviors. Depending on the chemical composition and the degree of cross-linking, the thermo-responsive property of HPC-PAA gel particles can be shifted from the UCST to the LCST property, and particle sizes can be changed from 100 to 1 microm in a controllable way. Successful loading of the gel particles with oxaliplatin, a hydrophilic antitumor drug, was achieved by take advantage of the complex interaction between the platinum atom of oxaliplatin and the carboxylic group of PAA in the gel particles. In vitro cytotoxicity assay indicates that the oxalipatin-loaded HPC-PAA gel particles have high anticancer activity. Considering the good biosafety, simple and mild preparation strategy and tunable size as well as the stimuli-responsive properties, the HPC-PAA gel particles should be a promising candidate for the drug delivery system.     

Poly (l-lysine) based semi-interpenetrating polymer network as pH-responsive hydrogel for controlled release of a model protein drug streptokinase

With the aim of developing a pH-sensitive controlled drug release system, a poly (L-lysine) (PLL) based cationic semi-interpenetrating polymer network (semi-IPN) has been synthesized. This cationic hydrogel was designed to swell at lower pH and de-swell at higher pH and therefore be applicable for achieving regulated drug release at a specific pH range. In addition to the pH sensitivity, this hydrogel was anticipated to interact with an ionic drug, providing another means to regulate the release rate of ionic drugs. This semi-IPN hydrogel was prepared using a free-radical polymerization method and by crosslinking of the polyethylene glycol (PEG)-methacrylate polymer through the PLL network. The two polymers were penetrated with each other via interpolymer complexation to yield the semi-IPN structures. The PLL hydrogel thus prepared showed dynamic swelling/de-swelling behavior in response to pH change, and such a behavior was influenced by both the concentrations of PLL and PEG-methacrylate. Drug release from this semi-IPN hydrogel was also investigated using a model protein drug, streptokinase. Streptokinase release was found to be dependent on its ionic interaction with the PLL backbones as well as on the swelling of the semi-IPN hydrogel. These results suggest that a PLL semi-IPN hydrogel could potentially be used as a drug delivery platform to modulate drug release by pH-sensitivity and ionic interaction.     

A model of cell wall expansion based on thermodynamics of polymer networks.

A theory of cell wall extension is proposed. It is shown that macroscopic properties of cell walls can be explained through the microscopic properties of interpenetrating networks of cellulose and hemicellulose. The qualitative conclusions of the theory agree with the existing experimental data. The dependence of the cell wall yield threshold on the secretion of the wall components is discussed.     

Poly(N-isopropylacrylamide)-based semi-interpenetrating polymer networks for tissue engineering applications. 1. Effects of linear poly(acrylic acid) chains on phase behavior

Poly(N-isopropylacrylamide)-based [P(NIPAAm)-based] semi-interpenetrating polymer networks (semi-IPNs), consisting of P(NIPAAm)-based hydrogels and linear poly(acrylic acid) [P(AAc)] chains, were synthesized, and the effects of the P(AAc) chains on semi-IPN injectability and phase behavior were analyzed. In P(NIPAAm)- and P(NIPAAm-co-AAc)-based semi-IPN studies, numerous reaction conditions were varied, and the effects of these factors on semi-IPN injectability, transparency, phase transition, lower critical solution temperature (LCST), and volume change were examined. The P(AAc) chains did not significantly affect the LCST or volume change of the semi-IPNs, compared to control hydrogels. However, the P(AAc) chains affected the injectability, transparency, and phase transition of the matrices, and these effects were dependent on chain amount and molecular weight (MW) and on interactions between the P(AAc) chains and the solvent and/or copolymer chains in P(NIPAAm-co-AAc) hydrogels. These results can be used to design "tailored" P(NIPAAm)-based semi-IPNs that have the potential to serve as functional scaffolds in tissue engineering applications.     

Smart hydrogels based on semi-interpenetrating polymeric networks of collagen-polyurethane-alginate for soft/hard tissue healing,drug delivery devices,and anticancer therapies

In this work, hydrogels based on semi-interpenetrating polymeric networks (semi-IPN) based on collagen-polyurethane-alginate were studied physicochemically and from different approaches for biomedical application. It was determined that the matrices in the hydrogel state are crosslinked by the formation of urea and amide bonds between the biopolymer chains and the polyurethane crosslinker. The increment in alginate content (0–40 wt%) significantly increases the swelling capacity, generating semi-crystalline granular structures with improved storage modulus and resistance to thermal, hydrolytic, and proteolytic degradation. The in vitro bioactivity results indicated that the composition of these novel hydrogels stimulates the metabolic activity of monocytes and fibroblasts, benefiting their proliferation; while in cancer cell lines, it was determined that the composition of these biomaterials decreases the metabolic activity of breast cancer cells after 48 h of stimulation, and for colon cancer cells their metabolic activity decreases after 72 h of contact for the hydrogel with 40 wt% alginate. The matrices show a behavior of multidose release of ketorolac, and a higher concentration of analgesic is released in the semi-IPN matrix. The inhibition capacity of Escherichia coli is higher if the polysaccharide concentration is low (10 wt%). The in vitro wound closure test (scratch test) results indicate that the hydrogel with 20 wt% alginate shows an improvement in wound closure at 15 days of contact. Finally, the bioactivity of mineralization was evaluated to demonstrate that these hydrogels can induce the formation of carbonated apatite on their surface. The engineered hydrogels show biomedical multifunctionality and they could be applied in soft and hard tissue healing strategies, anticancer therapies, and drug release devices.     

Biodegradable polymer networks based on oligolactide macromers: synthesis,properties and biomedical applications

Novel linear and star-shaped oligolactide macromers were synthesized by ring-opening oligomerization of L-lactide in the presence of suitable initiators (di- and polyols, amino acid esters) and subsequent endgroup-functionalization of the formed oligolactides with methacrylate moities. The obtained liquid macromers are valuable building blocks for the preparation of biocompatible polymer networks. Based on these macromers, the fabrication and the material properties including biodegradation behaviour of highly porous polymer network devices will be described. The application of these materials as resorbable scaffolds in tissue engineering will be discussed.     

Sensor system based on molecular-imprinted polymer membranes for the selective recognition of aflatoxin B1

lymer membranes, synthesized using acrylamide as a functional monomer, were characterized by sufficient mechanical stability and high adsorbtion capability towards aflatoxin B1. The molecularly-imprinted polymer membranes were characterized by the pronounced imprinting effect as well as by insignificant adsorbtion of aflatoxins B2 and G2. Therefore, the synthetic analogues of bioreceptors able to individual recognition of aflatoxin B1 were obtained and used as a basis for the optical sensor system for aflatoxin B1 detection in a concentration range 1-500 ng/ml.     

Native supported membranes on planar polymer supports and micro-particle supports

To bridge soft biological materials and hard inorganic materials is an interdisciplinary scientific challenge. Despite of experimental difficulties, the deposition of native biological membranes on supports is a straightforward strategy. This review provides an overview of advances in the fabrication and characterization of native biological membranes on planar polymer supports and micro-particles.     

Conducting polymer polypyrrole supported bilayer lipid membranes

Electrochemically synthesized conducting polymer polypyrrole (PPy) film on gold electrode surface was used as a novel support for bilayer lipid membranes (BLMs). Investigations by surface plasmon resonance (SPR) suggest that dimyristoyl-L-alpha-phosphatidylcholine (DMPC) and dimyristoyl-L-alpha-phosphatidyl-L-serine (DMPS) can form BLMs on PPy film surface but dimyristoyl-L-alpha-phosphatidylglycerol (DMPG) and didodecyldimethylammonium bromide (DDAB) can not do so, indicating the formation of PPy supported bilayer lipid membranes (s-BLMs) is dependent on the chemical structure of the lipids used. The self-assembly of DMPC induces a smoother topography than the PPy layer with rms roughness decreasing from 4.484 to 2.914 nm convinced by atomic force microscopy (AFM). Impedance spectroscopy measurements confirm that the deposition of BLM substantially increases the resistance of the system indicating a very densely packed BLM structures. The little change of PPy film in capacitance shows that solvent and electrolyte ions still retain within the porous PPy film after BLM deposition. Therefore, the PPy supported BLM is to some extent comparable to conventional BLM with aqueous medium retaining at its two sides. As an example and preliminary application, horseradish peroxidase (HRP) reconstituted into the s-BLM shows the expected protein activity and can transfer electron from or to the underlying PPy support for its response to electrocatalytic reduction of hydrogen peroxide in solution. Thus the system maybe possesses potential applications to biomimetic membrane studies.     

Effect of vibration on the structure and properties of polymer membranes

The influence of vibration (nonlinear wave effects) on the properties of films based on mixtures of some butadiene-styrene and acrylic latex by infrared spectroscopy was investigated. An enhancement of interactions in heterogenous systems was found, which may cause changes in their local and translation mobility.     

Immobilization of glucose oxidase on polymer membranes treated by low-temperature plasma

Low-temperature plasma was employed for activation of polymer membranes as a carrier for enzyme immobilization. Glucose oxidase was immobilized on polypropylene (PP), polyvinylidene fluoride (PVDF), or polytetrafluoroethylene (PTFE) membrane surfaces treated by nitrogen or ammonia gas plasma using glutaraldehyde as a linking agent. Enzyme activity was evaluated by the response of glucose sensor composed of the immobilized enzyme membrane and a dissolved oxygen electrode. The sensor response was found to depend on the kind of carrier membrane and to become maximum at suitable conditions of plasma treatment.     

Effect of vibration on the structure and properties of polymer membranes

The structural memory effect in a wave field has been studied by IR spectroscopy using butadiene-styrene and acrylic latex blend films as polymer membrane models. Notable is the enhancement of interactions between phases in such systems, which can cause changes in their local and translational mobility. The response of disperse polymer systems and their composites to nonlinear vibrations means that their deformation properties are affected by vibration, by analogy with orientation phenomena in solid polymers (where the Rebinder effect can appear), and can be considered as a means for modifying polymers, including the manufacture of nanocomposites, polymer biocarriers, etc.     

Preparation and hydrolytic degradation of semi-interpenetrating networks of poly(3-hydroxyundecenoate) and poly(lactide-co-glycolide)

Semi-interpenetrating networks (semi-IPNs), where poly(lactide-co-glycolide) (PLGA) molecules were entrapped in the crosslinked matrices of poly(3-hydroxyundecenoate) (PHU), were prepared by irradiating homogeneous solutions of PHU and PLGA in chloroform with UV light. Attenuated total reflectance infrared spectroscopy showed that the PLGA chains were entrapped in PHU networks. The semi-IPNs showed enhanced mechanical strength as the PLGA content increased. The semi-IPNs were incubated at 37 °C in a 0.01N NaOH solution, and the extent of hydrolytic degradation was investigated by monitoring changes in various parameters such as water uptake, pH, mass, and morphology. Hydrolysis of semi-IPNs were significantly affected by the presence of PLGA. A semi-IPN prepared from a 9:1 (by weight) mixture of PHU and PLGA lost 25% of its original weight in 12 weeks while a PHU sample containing no PLGA lost only 5% of its weight during the same period under identical conditions. The hydrolysis was most likely accelerated when the pH of the medium was lowered by the hydrolyzed products of PLGA, 2-hydroxyalkanoic acids. These results showed that hydrolysis of PHA could be enhanced by incorporating a second component that lowered the pH of the hydrolysis system.     

The swelling behavior and network parameters of guar gum/poly(acrylic acid) semi-interpenetrating polymer network hydrogels

Guar gum/poly(acrylic acid) semi-interpenetrating polymer network (IPN) hydrogels have been prepared via free radical polymerization in the presence of a crosslinker of N,N′-methylene bisacrylamide (MBA). The kinetics of swelling and the water transport mechanism were studied as a function of the composition of the hydrogels and the pH of the swelling medium. Hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics, which were highly dependent on the chemical composition of the hydrogels and pH of the medium in which hydrogels were immersed (ionic strength I = 0.15 mol/L). The semi-INP hydrogels were characterized by evaluating various network parameters such as average molecular weight between crosslinks (M_c) crosslink density (ρ) and mesh size ξ.