Biomimetic protein‐based elastomeric hydrogels for biomedical applications

In recent years, protein‐based elastomeric hydrogels have gained increased research interest in biomedical applications for their remarkable self‐assembly behaviour, tunable 3D porous structure, high resilience (elasticity), fatigue lifetime (durability), water uptake, excellent biocompatibility and biological activity. The proteins and polypeptides can be derived naturally (animal or insect sources) or by recombinant (bacterial expression) routes and can be crosslinked via physical or chemical approaches to obtain elastomeric hydrogels. Here we review and present the recent accomplishments in the synthesis, fabrication and biomedical applications of protein‐based elastomeric hydrogels such as elastin, resilin, flagelliform spider silk and their derivatives. © 2013 Society of Chemical Industry     

Designing crosslinked hyaluronic acid hydrogels with tunable mechanical properties for biomedical applications

This study develops a simple copolymerization/crosslinking technique to control the swelling and mechanical properties of hyaluronic acid‐based hydrogels. Because of the widespread acceptance of poly(ethylene glycol) in biomedical applications, functionalized oligomers of ethylene glycol (EG) were used as comonomers to crosslink methacrylated hyaluronic acid (MHA). The swelling degree, shear and elastic moduli, and fracture properties (stress and strain) of the gels were investigated as a function of the crosslinking oligomer length and reactive group(s). It was hypothesized that acrylated oligomers would increase the crosslink density of the gels through formation of kinetic chains by reducing the steric hindrances that otherwise may limit efficient crosslinking of hyaluronic acid into gels. Specifically, after crosslinking 13 wt % MHA (47% degree of methacrylation) with 0.06 mol % of (EG)_n‐diacrylate, the swelling ratio of the MHA gel decreased from 27 to 15 g/g and the shear modulus increased from 140 to 270 kPa as n increased from 1 to 13 units. The length and functionality (i.e., acrylate vs. methacrylate) of the oligomer controlled the crosslink density of the gels. The significant changes in the gel properties obtained with the addition of low levels of the PEG comonomer show that this method allows precise tuning of the physical properties of hyaluronic acid (HA) gels to achieve desired target values for biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42009.     

Antibacterial ciprofloxacin HCl incorporated polyurethane composite nanofibers via electrospinning for biomedical applications

We report on the preparation and characterization of polyurethane (PU) composite nanofibers by electrospinning. Two different approaches were adopted to obtain the PU composite nanofibers. In the first approach, a homogeneous solution of 10 wt% PU containing ciprofloxacin HCl (CipHCl) drug was electrospun to obtain PU/Drug composite nanofibers. And in the second approach, the PU with ciprofloxacin HCl drug and ceramic hydroxyapatite (HA) particles were electrospun to obtain the PU/Drug and PU/Drug/HA composite nanofibers. The surface morphology, structure, bonding configuration, optical and thermal properties of the resultant products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and UV–vis spectroscopy. The antibacterial activity was tested against common food borne pathogenic bacteria, namely, Staphylococcus aureus, Escherichia coli by the minimum inhibitory concentration (MIC) method. Our result results demonstrate that these composite nanofibers possess superior characteristics which can utilized for variety of applications.     

Properties of electrically responsive hydrogels as a potential dynamic tool for biomedical applications

Hydrogels with electric responsive properties are gaining research focus due to increasing demand for miniaturized devices that can be precisely controlled using an external stimulus. Such systems are well suited due to their ability to expand and contract when in contact with different types of fluid. This study reports on the synthesis of a “smart” electroresponsive network, using a neutral, “non‐smart,” biocompatible hydrogel forming building block, Pluronic F127 (PF127), as a starting molecule. The PEO–PPO–PEO copolymer was modified with telechelic methacrylic end functionalities to form a triblock linear prepolymer with crosslinkable end groups (crosslinker). This bifunctional prepolymer, PF127 bismethacrylate (PF127BMA), was copolymerized covalently with anionic methacrylic acid sodium salt groups into a nonsoluble 3D hydrogel network in the presence of redox initiators. The polyelectrolyte domains in the pluronic hydrogel afforded controllable swelling capabilities with volumetric expansion exceeding 8500% in deionized water or 1400% in Krebs solution. The hydrogels were further assessed for their mechanical and electroactive response as a function of increasing acid salt content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41195.     

Optimization of electrical stimulation parameters for electro‐responsive hydrogels for biomedical applications

Electro‐responsive hydrogels (ERH) are highly researched materials for biomedical applications. However, most of the research is concentrated on the synthesis of novel hydrogels for various applications, and little effort has been made to investigate electrode configuration and optimization of electrical stimulation parameters. This article used a three‐dimensional interdigitated (IDT) electrode configuration device to investigate the optimization of electrical actuation parameters in order to radially deswell an ERH. A Pluronic‐bismethacrylate hydrogel modified with hydrolyzed methacrylic acid was used as the ERH material. This article reports on using novel electro‐actuation parameters and electrode configurations to maximize radial deswelling of an ERH for biomedical applications. The optimal waveform was assessed for, varying electrode spacing's, voltages, duty cycles, and frequencies. The results show that a maximum deswelling occurred with a DC pulsed monophasic waveform, with IDT electrodes spaced close enough to create a relatively uniform electric field, with a peak voltage of 5 V at 1 kHz, and 50% duty cycle. This resulted in a deswelling of 320% in Krebs solution. Electrochemical impedance spectroscopy results show that the impedance is dependent on the ionic concentration of the fluid environment and that the impedance decreases with increasing frequency. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41687.     

A green and simple process to develop conductive polyurethane foams for biomedical applications

Abstract

In this work, conductive polyurethane (PU) foam is developed to be used as skin electrode for long term use medical devices. Water based polyurethane and other eco-friendly substances are selected to implement a green process, where the composite is produced in the shape of film and foam, by a transfer coating process. Different formulation and process materials are considered to evaluate the effect on surface resistivity and percolation threshold. The time stability, water vapor transmission, elongation and stress-strain properties, are studied. Results show that the realized material is suitable to be used as electrode for biomedical applications.     

Synthesis and properties of novel hydrogels from oxidized pectin crosslinked gelatin for biomedical applications

Gelatin (G) edible films with a new kind of dialdehyde polysaccharide, oxidized pectin (OP) as crosslinking agent are successfully prepared using casting techniques. FTIR and X-ray diffraction studies demonstrate that crosslinking is achieved through the reaction of aldehyde groups of oxidized pectin with the free amino groups in gelatin with a small affectation of the triple helix of gelatin. The qualitative and quantitative data about structures of films were determined by atomic force microscopy. Thermogravimetric analysis reveals that G/OP film has improved thermal stability in comparison with pure gelatin. Examination of the hemolytic potential showed that the obtained hydrogels are non-hemolytic in nature. These hydrogels are also nontoxic and blood-compatible. This kind of hydrogel is expected to be useful in the biomedical field, e.g., as wound dressing.     

Castor oil and PEG‐based shape memory polyurethane films for biomedical applications

A series of polyurethane film were prepared from poly(ethylene glycol) with different molecular weight (PEG 1500, 3000, and 8000) and castor oil by one‐shot bulk polymerization method. Hexamethylene diisocyanate and 1,4‐buthane diol were used as diisocyanate and chain extender, respectively. In order to characterize the samples, their density, swelling ratio, water contact angle, surface free energy, gel content, thermal, and viscoelastic properties were determined. The effect of the soft segment length (SSL) and hard segment content (HSC) of all polyurethane films on their shape memory behavior such as shape fixity (R_f) and shape recovery (R_r) rates were investigated by bending test. Direct contact and MTT tests were used for assessment of cell adhesion and proliferation. The relatively high R_f and R_r values were obtained for the samples programmed at high temperature difference. R_f increased with decreasing HSC. On the other hand, R_r tended to decrease with increasing SSL. After evaluating experimental data by a nonlinear equation, it was found that HSC is more effective parameter on shape memory property than SSL. The gel content, swelling ratio, and water contact angle of the samples were dependent on both SSL and HSC in their structures. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40590.     

Materials for biomedical applications

The various materials used in biomedical applications, viz., metals and alloys, polymers, ceramics, and composites, are reviewed, and their respective areas of application discussed. Problems of compatibility with tissue and body fluids are reviewed and the performance of the various materials systems examined. Some examples of failure of implanted devices are shown, and the need for careful control of quality as well as of material specification is emphasized. Finally, the importance of close cooperation between medical, engineering and metallurgical specialists in this area is noted, together with the requirement of a better knowledge of materials on the part of the surgical personnel involved.     

Novel semi-interpenetrated networks based on collagen-polyurethane-polysaccharides in hydrogel state for biomedical applications

The development of collagen hydrogels with tailored properties for improved applications in biomedicine represents an area of opportunity for materials science. The collagen can form semi-interpenetrated networks (semi-IPN) with various natural and/or synthetic polymers. This work aims the preparation of novel hydrogels generated from a collagen matrix cross-linked with polyurethane (PU), and the subsequent inclusion of polysaccharide chains to form semi-IPN systems with improved properties. The choice of polysaccharides for this purpose is related to their ability to modulate the biocompatibility and the antibacterial capacity in various biomedical strategies. The work contemplates to study the effect of the chemical structure of polysaccharide (hydroxyethylcellulose (HEC), hydroxypropylmethylcellulose (HPMC) or starch (Alm)) on the properties of these novel hydrogels. The results indicate that the semi-IPN hydrogels that include Alm exhibit the formation of stronger intermolecular interactions promoted by hydrogen bonds than HEC and HPMC, significantly improving the mechanical properties and their degradation rate in acidic, alkaline, and proteolytic media; also showing high capacity to inhibit the growth of E. colli. The semi-IPN hydrogels based on HEC and HPMC exhibit excellent improvement in both thermal and proteolytic degradation, compared with the collagen-PU matrix. On the other hand, this semi-IPN system does not present cytotoxic character for monocytes and fibroblasts growing for up to 48 h of culture. Therefore, these innovative 3D matrices will be excellent candidates with potential application in biomedical strategies such as wound healing dressings.     

Synthesis and characterization of photopolymerizable hydrogels based on poly (ethylene glycol) for biomedical applications

Hydrogels are polymeric materials widely used in medicine due to their similarity with the biological components of the body. Hydrogels are biocompatible materials that have the potential to promote cell proliferation and tissue support because of their hydrophilic nature, porous structure, and elastic mechanical properties. In this work, we demonstrate the microwave-assisted synthesis of three molecular weight varieties of poly(ethylene glycol) dimethacrylate (PEGDMA) with different mechanical and thermal properties and the rapid photo of them using 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184) as UV photoinitiator. The effects of the poly(ethylene glycol) molecular weight and degree of acrylation on swelling, mechanical, and rheological properties of hydrogels were investigated. The biodegradability of the PEGDMA hydrogels, as well as the ability to grow and proliferate cells, was examined for its viability as a scaffold in tissue engineering. Altogether, the biomaterial hydrogel properties open the way for applications in the field of regenerative medicine for functional scaffolds and tissues.     

Protein-based nanotubes for biomedical applications

This review presents highlights of our latest results of studies directed at developing protein-based smart nanotubes for biomedical applications. These practical biocylinders were prepared using an alternate layer-by-layer (LbL) assembly of protein and oppositely charged poly(amino acid) into a nanoporous polycarbonate (PC) membrane (pore diameter, 400 nm), with subsequent dissolution of the template. The tube wall typically comprises six layers of poly-L-arginine (PLA) and human serum albumin (HSA) [(PLA/HSA)(3)]. The obtained (PLA/HSA)(3) nanotubes (NTs) can be dispersed in aqueous medium and are hydrated significantly. Several ligands for HSA, such as zinc(II) protoporphyrin IX (ZnPP), were bound to the HSA component in the cylindrical wall. Similar NTs comprising recombinant HSA mutant, which has a strong binding affinity for ZnPP, captured the ligand more tightly. The Fe(3)O(4)-coated NTs can be collected easily by exposure to a magnetic field. The hybrid NTs bearing a single avidin layer as an internal wall captured biotin-labeled nanoparticles into the central channel when their particle size is sufficiently small to enter the pores. The NTs with an antibody surface interior entrapped human hepatitis B virus with size selectivity. It is noteworthy that the infectious Dane particles were encapsulated completely into the hollows. Other HSA-based NTs having an α-glucosidase inner wall hydrolysed a glucopyranoside to yield α-D-glucose. A perspective of the practical use of the protein-based NTs is also described.     

Smart membranes for biomedical applications

Smart membranes with tunable permeability and selectivity have drawn widespread attention because of their unique biomimetic characteristics. Constructed by incorporating various stimuli-responsive materials into membrane substrates, smart membranes could self-adjust their physical/chemical properties(such as pore size and surface properties) in response to environmental signals such as temperature,pH, light, magnetic field, electric field, redox and specific ions/molecules. Such smart membranes...     

Hydrolytic stabilities of some polyurethane hydrogels

The hydrolytic stability of some polyurethane hydrogels derived from UV-curable urethane prepolymers and hydrophilic monomers was addressed. It was found that polyurethane hydrogels derived from prepolymers with hydrophilic polypropylene glycol soft segments were not stable when the films were cast from nonpolar solvent, whereas they are stable if the films were cast from neat monomer mix. The causes for this instability were analyzed. Spectroscopic and gel permeation chromatographic studies of the water extractables suggested that improper curing of hydrophilic monomers with the urethane prepolymers in nonpolar solvent was mainly responsible for the instability phenomenon.     

Development of pH-sensitive and antibacterial gelatin/citric acid/Ag nanocomposite hydrogels with potential for biomedical applications

This work aimed to prepare pH-sensitive and antibacterial drug releasing systems through a completely green route. To achieve this, the gelatin natural biopolymer was crosslinked with citric acid in the presence of Ag nanoparticles (NPs). Interestingly, Ag NPs formation and gelatin crosslinking were simultaneously occurred during annealing of samples without need for any toxic chemicals, which were confirmed by FTIR, UV-vis spectra, SEM and TEM observations. In addition, potential of the citric acid crosslinked-gelatin/Ag nanocomposite hydrogels was successfully explored for drug delivery applications using cefixime as a model drug. It was found that these hydrogels have pH-dependent swelling and drug release behavior with higher drug release at pH 7.4 compared to pH 1.2. Also, an antibacterial effect against the E. coli and S. aureus microorganisms was achieved by incorporation of Ag NPs into hydrogels. These hydrogels can be considered as stimuli responsive materials for oral drug delivery and wound dressing applications.     

Novel and simple methodology to fabricate porous and buckled fibrous structures for biomedical applications

Reproducible buckled and porous sub-micron diameter polycaprolactone (PCL) fibers were produced by simple electrospinning process for biomedical applications. In this study, six types of solvent combinations with different vapor pressures were used to study the effect of phase separation on the morphology of electrospun fibers. The fiber morphology, Infrared spectroscopy, water contact angle and tensile test were performed to study the material properties. It is evident that the fiber morphology was affected by solvent combinations used for the fabrication of sub-micron fibers. The solution viscosity, the collecting distance and the type of solvent combination used could be an optimum parameter for the generation of porous-buckled fibers with narrow pore size distribution. The simplicity of the set-up is the immense advantage for producing buckled and porous elastomeric fibers for tissue engineering applications. All the fibers were spun on a motionless collector plate to study the properties of fibers. The combination of surface pores with the buckled pattern could be of great importance in the field of biomedical engineering.     

Monodisperse magnetic nanoparticles for biomedical applications

Magnetic nanoparticles that are superparamagnetic with high saturation moment have great potential for biomedical applications. Solution‐phase syntheses have recently been applied to make various kinds of monodisperse magnetic nanoparticles with standard deviation in diameter of less than 10%. However, the surface of these nanoparticles is coated with a layer of hydrocarbon molecules due to the use of lipid‐like carboxylic acid and amine in the syntheses. Surface functionalization leads to the formation of water‐soluble nanoparticles that can be further modified with various biomolecules. Such functionalization has brought about several series of monodisperse magnetic nanoparticle systems that have shown promising applications in protein or DNA separation, detection and magnetic resonance imaging contrast enhancement. The goal of this mini review is to summarize the recent progress in the synthesis and surface modification of monodisperse magnetic nanoparticles and their applications in biomedicine. Copyright © 2007 Society of Chemical Industry     

Polymeric nanostructured materials for biomedical applications

Polymeric nanostructured materials (PNMs), which are polymeric materials in nanoscale or polymer composites containing nanomaterials, have become increasingly useful for biomedical applications. In specific, advances in polymer-related nanoscience and nanotechnology have brought a revolutionary change to produce new biomaterials with tailored properties and functionalities for targeted biomedical applications. These materials, including micelles, polymersomes, nanoparticles, nanocapsules, nanogels, nanofibers, dendrimers and nanocomposites, have been widely used in drug delivery, gene therapy, bioimage, tissue engineering and regenerative medicine. This review presents a comprehensive overview on the various types of PNMs, their fabrication methods and biomedical applications, as well as the challenges in research and development of future PNMs.     

Biopolymeric nanocomposites for potential biomedical applications

This review reports recent advances in the field of biopolymeric composites and nanocomposites for potential biomedical applications. These materials have attracted both academic and, for several composites, industrial attention because they exhibit properties required in the biomedical field. Herein, the structure, preparation and properties of biopolymeric composite blends are discussed in general, and detailed examples are also drawn from the scientific literature and practical work. In this review the most common natural polymers collagen, chitosan and their composites and nanocomposites with inorganic particles are discussed. © 2016 Society of Chemical Industry