Preparation of Alginate-Based Biomaterials and Their Applications in Biomedicine.

Alginates are naturally occurring polysaccharides extracted from brown marine algae and bacteria. Being biocompatible, biodegradable, non-toxic and easy to gel, alginates can be processed into various forms, such as hydrogels, microspheres, fibers and sponges, and have been widely applied in biomedical field. The present review provides an overview of the properties and processing methods of alginates, as well as their applications in wound healing, tissue repair and drug delivery in recent years.

Hematite Nanoparticles from Unexpected Reaction of Ferrihydrite with Concentrated Acids for Biomedical Applications.

The development of synthetic ways to fabricate nanosized materials with a well-defined shape, narrow-sized distribution, and high stability is of great importance to a rapidly developing area of nanotechnology. Here, we report an unusual reaction between amorphous two-line ferrihydrite and concentrated sulfuric or other mineral and organic acids. Instead of the expected dissolution, we observed the formation of new narrow-distributed brick-red nanoparticles (NPs) of hematite. Different acids produce similar nanoparticles according to scanning (SEM) and transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDX). The reaction demonstrates new possibilities for the synthesis of acid-resistant iron oxide nanoparticles and shows a novel pathway for the reaction of iron hydroxide with concentrated acids. The biomedical potential of the fabricated nanoparticles is demonstrated by the functionalization of the particles with polymers, fluorescent labels, and antibodies. Three different applications are demonstrated: i) specific targeting of the red blood cells, e.g., for red blood cell (RBC)-hitchhiking; ii) cancer cell targeting in vitro; iii) infrared ex vivo bioimaging. This novel synthesis route may be useful for the development of iron oxide materials for such specificity-demanding applications such as nanosensors, imaging, and therapy.

Recent Progress in Polyhydroxyalkanoates-Based Copolymers for Biomedical Applications.

In recent years, naturally biodegradable polyhydroxyalkanoate (PHA) monopolymers have become focus of public attentions due to their good biocompatibility. However, due to its poor mechanical properties, high production costs, and limited functionality, its applications in materials, energy, and biomedical applications are greatly limited. In recent years, researchers have found that PHA copolymers have better thermal properties, mechanical processability, and physicochemical properties relative to their homopolymers. This review summarizes the synthesis of PHA copolymers by the latest biosynthetic and chemical modification methods. The modified PHA copolymer could greatly reduce the production cost with elevated mechanical or physicochemical properties, which can further meet the practical needs of various fields. This review further summarizes the broad applications of modified PHA copolymers in biomedical applications, which might shred lights on their commercial applications.

Silylation of bacterial cellulose to design membranes with intrinsic anti-bacterial properties.

In this work, we report a convenient method of grafting non-leachable bioactive amine functions onto the surface of bacterial cellulose (BC) nanofibrils, via a simple silylation treatment in water. Two different silylation protocols, involving different solvents and post-treatments were envisaged and compared, using 3-aminopropyl-trimethoxysilane (APS) and (2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPS) as silylating agents. In aqueous and controlled conditions, water-leaching resistant amino functions could be successfully introduced into BC, via a simple freeze-drying process. The silylated material remained highly porous, hygroscopic and displayed sufficient thermal stability to support the sterilization treatments generally required in medical applications. The impact of the silylation treatment on the intrinsic anti-bacterial properties of BC was investigated against the growth of Escherichia coli and Staphylococcus aureus. The results obtained after the in vitro studies revealed a significant growth reduction of S. aureus within the material.

Influence of acid treatment on surface properties and in vivo performance of Ti6Al4V alloy for biomedical applications.

The purpose of this work was to investigate the influence of acid treatment on the surface properties and in vivo performance of titanium grade 5 (Ti6Al4V) alloy. Mini-implants with surface treatment were inserted into New Zealand rabbit tibia for 1, 4 and 8 weeks. SEM analysis showed intercommunicated micropores in acid treated samples. AFM showed micron and sub-micron roughness. The thickness of the titanium oxide layer increased with surface treatment, with a significant reduction of Al and V concentration. Acid treated implant removal torque was larger than without treatment. The implants/bone interface of acid treated implants showed dense adhered Ca/P particles with spreading osteoblasts after 4 weeks and newly formed bone trabeculae after 8 weeks. Analysis of rabbit blood that received treated implant showed lower Al and V contents at all times. Acid treatment improved surface morphology and mechanical stability, which allowed initial events of osseointegration, while Al-V ion release was reduced. GRAPHICAL ABTSRACT.

Minimal Device Encrustation on Vesair Intravesical Balloons in the Treatment of Stress Urinary Incontinence: Analysis of Balloons Removed from Women in the SOLECT Trial.

INTRODUCTION: Encrustation of urinary biomaterials is common; however, the incidence of surface deposition on the Vesair® intravesical pressure-attenuation balloon has not been previously reported. The purpose of this analysis is to determine the incidence and potential risk factors for encrustation of the Vesair intravesical balloon. METHODS: The SOLECT trial is a prospective randomized controlled trial conducted at several European centers to evaluate the safety and efficacy of the Vesair balloon for the treatment of female stress urinary incontinence (SUI). Women included in the study demonstrated SUI symptoms for more than 12 months without complicating factors, such as history of recurrent urinary tract infections or nephrolithiasis. All balloons removed from women enrolled in the SOLECT trial were analyzed for surface characteristics and encrustation. Surface deposition severity was quantified and composition analyzed with infrared spectroscopy and scanning electron microscopy. Incidence of surface deposition was tabulated and risk factors analyzed. RESULTS: One hundred and five balloons removed from 75 women were included in this analysis. Measurable stone deposition of less than 1.5 mm was found on four balloons (3.8%), surface granules were noted on 42 (40.0%), surface film on 11 (10.5%), and both granules and film on two (1.9%). Analysis identified calcium oxalate both in measurable encrustation deposits as well as those with surface granulation. Pooled analysis found that dwell time was a risk factor for calcium deposition. CONCLUSION: The rate of encrustation on the Vesair intravesical balloon is low and does not appear to increase the rate of adverse outcomes or reduce clinical efficacy. FUNDING: Solace Therapeutics, Inc.

[Investigation of mechanical properties of materials used for functional stabilization in pilon fractures].

Existing methods of surgical treatment of the pilon fractures do not provide early functional rehabilitation of patients. The lack of confidence in secure fixation of fragments in significant quantity of patients causes necessity to apply a plaster immobilization during long time. While seeking possibilities of early functional treatment of the pilon fractures there was proposed a theory of "functional stabilization" (instead of "artificial", but necessary plaster immobilization), materials and technologies for its realization. For substantiating, from the biomechanical point of view, of expediency of a new materials (Softcost, Scotchcost) application the data about their physic-chemical properties were adduced, and in particular, there were studied the bowing values, depending on loading, and modules of elasticity of these materials.

Bioengineered collagens: emerging directions for biomedical materials.

Mammalian collagen has been widely used as a biomedical material. Nevertheless, there are still concerns about the variability between preparations, particularly with the possibility that the products may transmit animal-based diseases. Many groups have examined the possible application of bioengineered mammalian collagens. However, translating laboratory studies into large-scale manufacturing has often proved difficult, although certain yeast and plant systems seem effective. Production of full-length mammalian collagens, with the required secondary modification to give proline hydroxylation, has proved difficult in E. coli. However, recently, a new group of collagens, which have the characteristic triple helical structure of collagen, has been identified in bacteria. These proteins are stable without the need for hydroxyproline and are able to be produced and purified from E. coli in high yield. Initial studies indicate that they would be suitable for biomedical applications.

A self-referenced optical intensity sensor network using POFBGs for biomedical applications.

This work bridges the gap between the remote interrogation of multiple optical sensors and the advantages of using inherently biocompatible low-cost polymer optical fiber (POF)-based photonic sensing. A novel hybrid sensor network combining both silica fiber Bragg gratings (FBG) and polymer FBGs (POFBG) is analyzed. The topology is compatible with WDM networks so multiple remote sensors can be addressed providing high scalability. A central monitoring unit with virtual data processing is implemented, which could be remotely located up to units of km away. The feasibility of the proposed solution for potential medical environments and biomedical applications is shown.

[Effect of ozonated water on physical and chemical properties of vacuum sealing drainage material].

OBJECTIVE: To investigate the influence of ozonated water on physical and chemical properties of vacuum sealing drainage (VSD) materials. METHODS: VSD materials (foam and sealing membrane) were immersed in 10 µg/ml ozonated water for 1 h twice daily for 8 days. The foam appearance and microscopic structure of the materials were observed, and tensile tests and Raman spectrum scan were performed assess the effect of ozonated water. Simulated VSD devices were prepared and tested for leakproofness under negative pressure after ozonated water treatment. RESULTS: zonated water treatment for 8 days caused no obvious abnormal changes in the foam appearance or microscopic structure of the materials. The maximum tensile load of foam before and after ozonated water treatment was 4.25∓0.73 kgf and 2.44∓0.19 kgf (P=0.000), the momentary distance when the foam torn before and after intervention was 92.54∓12.83 mm and 64.44∓4.60 mm, respectively (P=0.000). The corresponding results for VSD sealing membrane were 0.70∓0.58 kgf and 0.71∓0.08 kgf (P=0.698), and 99.30∓10.27 mm and 100.95∓18.22 mm (P=0.966), respectively. Raman spectroscopy revealed changes in only several wave intensities and no new chemical groups appeared within the scan range of 400-4000 cm(-1). The VSD device was well hermetic after treatment with ozonated water. CONCLUSION: Except for a decreased stretch resistance property of the foam, VSD materials display no obvious changes in physical and chemical characteristics after treatment with ozonated water for 8 days.

Triblock copolymers of ε-caprolactone, trimethylene carbonate, and L-lactide: effects of using random copolymer as hard-block.

A series of triblock copolymers comprising end block of PLLA modified with PCL, and random copolymer of PCL and PTMC as soft segment were synthesized. DSC data show that PCL disrupted the crystallinity of PLLA, making the hard block to be completely amorphous when the PCL content is 50%. Correspondingly, the addition of PCL into PLLA block enhances the elongation of the triblock considerably. With regards to the elasticity, however, creep test results show that adding PCL to PLLA block seems to reduce the "equilibrium" recovery, while cyclic test results shows that the instantaneous recovery increased significantly with more PCL inside PLLA block. It was also observed that the degradation rate of triblock with added PCL inside the PLLA was slower compared to triblock with pure PLLA hard block. Compared to biodegradable polyurethane, these polymers are expected to yield less harmful degradation products, and offer more variables for the manipulation of properties. These polymers are also processable from the melt at temperatures exceeding about 130 °C. We expect to use these polymers in a variety of applications, including stent coatings, fully-degradable stents and atrial septal defect occluders.

Nature inspired structured surfaces for biomedical applications.

Nature has created an array of superhydrophobic surfaces that possess water-repellent, self-cleaning and anti-icing properties. These surfaces have a number of potential applications in the biomedical industry, as they have the potential to control protein adsorption and cell adhesion. Natural superhydrophobic surfaces are typically composed of materials with a low intrinsic surface free-energy (e.g the cuticular waxes of lotus leaves and insect wings) with a hierarchical structural configuration. This hierarchical surface topography acts to decrease the contact area of water droplets in contact with the surface, thereby increasing the extent of the air/water interface, resulting in water contact angles greater than 150º. In order to employ these surfaces in biotechnological applications, fabrication techniques must be developed so that these multi-scale surface roughness characteristics can be reproduced. Additionally, these fabrication techniques must also be able to be applied to the material required for the intended application. An overview of some of the superhydrophobic surfaces that exist in nature is presented, together with an explanation of the theories of their wettability. Also included is a description of some of the biomedical applications of superhydrophobic surfaces and fabrication techniques that can be used to mimic superhydrophobic surfaces found in nature.

Novel hard-block polyurethanes with high strength and transparency for biomedical applications.

Novel hard-block-only polyurethanes are prepared from 1,4-butanediol (BDO) and a pre-polymer synthesized separately from 1,3-bis (4-hydroxybutyl) tetramethyl disiloxane (BHTD) and 4,4'-diphenylmethane diisocyanate (MDI). Three (co)polymers using different proportions of these chain extenders were synthesized using reaction injection moulding, and their microstructure, mechanical properties and in vitro oxidative biostability were evaluated. These materials were found to form a single-phase system, and exhibit optical transparency, high elastic modulus and tensile strength, as well as significant in vitro oxidative biostability. By controlling the BDO/BHTD composition, the ductility can be tuned over orders of magnitude. These polyurethanes may be potentially suitable for biomedical applications, like electronic headers for defibrillators, pacemakers and neurostimulators, and orthopedic nail encapsulation.

The bioactivity and ion release of titanium-containing glass polyalkenoate cements for medical applications.

The ion release profiles and bioactivity of a series of Ti containing glass polyalkenoate cements. Characterization revealed each material to be amorphous with a T(g) in the region of 650-660°C. The network connectivity decreased (1.83-1.35) with the addition of TiO(2) which was also evident with analysis by X-ray photoelectron spectroscopy. Ion release from cements were determined using atomic absorption spectroscopy for zinc (Zn(2+)), calcium (Ca(2+)), strontium (Sr(2+)), Silica (Si(4+)) and titanium (Ti(4+)). Ions such as Zn(2+) (0.1-2.0 mg/l), Ca(2+) (2.0-8.3 mg/l,) Sr(2+) (0.1-3.9 mg/l), and Si(4+) (14-90 mg/l) were tested over 1-30 days. No Ti(4+) release was detected. Simulated body fluid revealed a CaP surface layer on each cement while cell culture testing of cement liquid extracts with TW-Z (5 mol% TiO(2)) produced the highest cell viability (161%) after 30 days. Direct contact testing of discs resulted in a decrease in cell viability of the each cement tested.

Physicochemical parameters influencing coaggregation between the freshwater bacteria Sphingomonas natatoria 2.1 and Micrococcus luteus 2.13.

The aim of this study was to explore the physicochemical parameters that influence coaggregation between the freshwater bacteria Sphingomonas natatoria 2.1 and Micrococcus luteus 2.13. Using visual coaggregation assays, the effect of different buffers, solutions of differing ionic strength, pH, temperature, and viscosity on the degree of coaggregation was assessed. Coaggregation occurred maximally in distilled water but was inhibited when coaggregates were suspended in a commonly-used oral bacterial coaggregation buffer, saline solutions, and Tris-Cl buffers. Coaggregation was weakly expressed in standard laboratory buffers. The ionic strength of inorganic salt solutions required to inhibit coaggregation depended upon the inorganic salt being tested. Coaggregation occurred at a pH of 3-10, between 5 and 80°C and was inhibited in solutions with a viscosity of 22.5 centipoises at 20°C. Inhibition of coaggregation with NaCl impaired biofilm development. When developing buffers to test for coaggregation, the natural liquid environment should be considered. Coaggregation between S. natatoria 2.1 and M. luteus 2.13 is only affected by physicochemical conditions beyond those typically found in natural freshwater ecosystems. Such a robust ability to coaggregate may enhance the ability of S. natatoria 2.1 and M. luteus 2.13 to develop a niche in freshwater biofilms.

Preparation and characterization of NaOH treated micro-fibrous polyethylene terephthalate nonwovens for biomedical application.

Recently, micro-fibrous polyethylene terephthalate nonwovens have been investigated and applied in many biotechnological and biomedical applications. NaOH treatment has been used as a simple and cost effective method to alter surface properties, in order to overcome their surface inertness. However, the effects of this treatment on the matrices mechanical and physical properties; particularly, those composed of fibers with small diameter (<20 microm); have been poorly investigated. This study investigates the variations, imposed by the NaOH treatment, in the physical and tensile properties of micro-fibrous polyethylene terephthalate mats. Polyethylene terephthalate webs with two different average fiber diameters of 6+/-2.5 and 10+/-4 microm were produced by melt blowing process. A number of these webs were consolidated to prepare fibrous matrices using a thermal treatment. The matrices were treated using NaOH 1 N at 65 degrees C for various durations (ranging from 20 min to 24 h). In addition to their physical properties such as weight loss, thickness, porosity, shrinkage and surface density; their morphology and tensile properties were also evaluated using scanning electron microscopy and micromechanical tester, respectively. In general, by increasing treatment duration, weight loss, porosity, and shrinkage increased, while thickness and density decreased. As a result of treatment duration, pores appeared on the surface of individual fibers, and tensile stress and Young's modulus decreased while tensile strain increased. Mats with different fiber diameters showed different physical and mechanical properties. These findings suggested that the structure of the matrices and the properties required for its end use, for biomedical applications including scaffolding materials for tissue engineering, should be considered in selecting NaOH treatment condition.

Water-mediated signal multiplication with Y-shaped carbon nanotubes.

Molecular scale signal conversion and multiplication is of particular importance in many physical and biological applications, such as molecular switches, nano-gates, biosensors, and various neural systems. Unfortunately, little is currently known regarding the signal processing at the molecular level, partly due to the significant noises arising from the thermal fluctuations and interferences between branch signals. Here, we use molecular dynamics simulations to show that a signal at the single-electron level can be converted and multiplied into 2 or more signals by water chains confined in a narrow Y-shaped nanochannel. This remarkable transduction capability of molecular signal by Y-shaped nanochannel is found to be attributable to the surprisingly strong dipole-induced ordering of such water chains, such that the concerted water orientations in the 2 branches of the Y-shaped nanotubes can be modulated by the water orientation in the main channel. The response to the switching of the charge signal is very rapid, from a few nanoseconds to a few hundred nanoseconds. Furthermore, simulations with various water models, including TIP3P, TIP4P, and SPC/E, show that the transduction capability of the Y-shaped carbon nanotubes is very robust at room temperature, with the interference between branch signals negligible.

Multicomponent solubility parameters for single-walled carbon nanotube-solvent mixtures.

We have measured the dispersibility of single-walled carbon nanotubes in a range of solvents, observing values as high as 3.5 mg/mL. By plotting the nanotube dispersibility as a function of the Hansen solubility parameters of the solvents, we have confirmed that successful solvents occupy a well-defined range of Hansen parameter space. The level of dispersibility is more sensitive to the dispersive Hansen parameter than the polar or H-bonding Hansen parameter. We estimate the dispersion, polar, and hydrogen bonding Hansen parameter for the nanotubes to be = 17.8 MPa(1/2), = 7.5 MPa(1/2), and = 7.6 MPa(1/2). We find that the nanotube dispersibility in good solvents decays smoothly with the distance in Hansen space from solvent to nanotube solubility parameters. Finally, we propose that neither Hildebrand nor Hansen solubility parameters are fundamental quantities when it comes to nanotube-solvent interactions. We show that the previously calculated dependence of nanotube Hildebrand parameter on nanotube diameter can be reproduced by deriving a simple expression based on the nanotube surface energy. We show that solubility parameters based on surface energy give equivalent results to Hansen solubility parameters. However, we note that, contrary to solubility theory, a number of nonsolvents for nanotubes have both Hansen and surface energy solubility parameters similar to those calculated for nanotubes. The nature of the distinction between solvents and nonsolvents remains to be fully understood.

Properties of shape memory polyurethane used as a low-temperature thermoplastic biomedical orthotic material: influence of hard segment content.

A series of PCL-based shape memory polyurethanes was synthesized via bulk pre-polymerization. Their thermal, mechanical properties, shape memory properties, softening and hardening processes were investigated by the experimental approach and made comparison with a commercially available orthotic material. The cytotoxicity of the low-temperature thermoplastic polyurethane was tested. The results suggest that the soft segment phase of the shape memory polyurethanes has a melting transition at about 36-46 degrees C, which makes them possible low-temperature thermoplastic materials. The hard segment phase has a two-fold effect on the shape memory polyurethane as a low-temperature thermoplastic orthotic material: increasing tensile mechanical strength at room temperature, which enables it to be used in circumstances where high tensile strength is required; and reducing low-temperature malleability and fixity ratio, which make it difficult to fabricate orthotic devices. To obtain a shape memory polyurethane with excellent low-temperature thermoplastic properties for orthopaedical surgical use, the hard segment content should not be above 22 wt%. At last, a prototype wrist orthosis was easily fabricated at 60 degrees C with hand using a shape memory polyurethane with 16 wt% hard segment content. Cytotoxicity tests indicate that the wrist orthotic material is not cytotoxic.

P(AAm-co-MAA) semi-IPN hybrid hydrogels in the presence of PANI and MWNTs-COOH: improved swelling behavior and mechanical properties.

A highly pH-sensitive hybrid hydrogel with semi-interpenetrating networks (semi-IPN)composed of co-polymer networks of acrylamide-methacrylic acid (P(AAm-co-MAA)) and polyaniline (PANI)/carboxyl-functionalized multi-walled carbon nanotubes (MWNTs-COOH) was designed and synthesized by a cross-linking co-polymerization route in the presence of N,N-methylene bisacrylamide (BIS) and ammonium persulfate (APS). The structural and morphological characterization and mechanical properties of the gels were investigated using a Equinx55 FT-IR spectrometer, an environmental scanning electron microscope and a dynamical viscoelasticity analyzer, respectively. Swelling capability of the hybrid hydrogels was examined under the conditions of various pH buffer solutions (1.35, 6.95 and 12.86) at a temperature of 27 degrees C. P(AAm-co-MAA) co-polymer hydrogels were discussed as a control sample at the same time. The experimental results indicated that the prepared P(AAm-co-MAA) co-polymer hydrogels showed a high equilibrium swelling ratio in distilled water, pH-responsive characteristics and excellent strain recoverability. After having incorporated the polyelectrolyte PANI and MWNTs-COOH into the above-mentioned network, the P(AAm-co-MAA)/PANI/MWNTs-COOH semi-IPN hybrid hydrogels obtained possessed an even higher sensitivity to pH environments, good swelling reversibility, higher ultimate compressive strength and good strain recoverable ability. Swelling experimentations in buffer solutions of different pH revealed that the semi-IPN hybrid hydrogels possessed higher tensile strengths at a lower pH than at a higher pH value. All the excellent properties may primarily be attributed to the formation and weakening or disappearance of a repulsive force based on hydrogen bonds, as well as appearance of attractive forces of pole-pole interactions between PANI chains at different pH values.