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Raman spectroscopic markers have been determined for fatigue-related microdarnage in bovine bone. Microdamage was induced using a cyclic fatigue loading regime. After loading, the specimens were stained en-bloc with basic fuchsin to facilitate damage visualization and differentiate fatigue-induced damage from cracks generated during subsequent histological sectioning. Bone tissue specimens were examined by light microscopy and hyperspectral near-infrared Raman imaging microscopy. Three regions were defined - tissue with no visible damage, tissue with microcracks, and tissue with diffuse damage. Raman transects, lines of 150-200 Raman spectra, were used for initial tissue surveys. Exploratory factor analysis of the transect Raman spectra has identified spectroscopically distinct chemical microstmctures of the bone specimens that correlate with damage. In selected regions of damage, full hyperspectral Raman images were obtained with 1.4-(mu)m spatial resolution. In regions of undamaged tissue, the phosphate (nu)(sub 1) band is found at 957 cm(super -1), as expected for the carbonated hydroxyapatic bone mineral. However, in regions of visible microdamage, an additional phosphate (nu)(sub 1) band is observed at 963 cm(super -1) and interpreted as a more stoichiometric, less carbonated mineral species. Raman imaging confirms the qualitative relationship between the Rarnan spectral signature of bone mineral and the type of microdamage in bovine bone. Two tentative explanations for the presence of less carbonated phosphate in damaged regions are proposed.

As a prominent concern regarding implantable devices, eliminating the threat of opportunistic bacterial infection represents a significant benefit to both patient health and device function. Current treatment options focus on chemical approaches to negate bacterial adhesion, however, these methods are in some ways limited. The scope of this study was to assess the efficacy of a novel means of modulating bacterial adhesion through the application of vibrations using magnetoelastic materials. Magnetoelastic materials possess unique magnetostrictive property that can convert a magnetic field stimulus into a mechanical deformation. In vitro experiments demonstrated that vibrational loads generated by the magnetoelastic materials significantly reduced the number of adherent bacteria on samples exposed to Escherichia coli, Staphylococcus epidermidis and Staphylococcus aureus suspensions. These experiments demonstrate that vibrational loads from magnetoelastic materials can be used as a post-deployment activated means to deter bacterial adhesion and device infection. [ABSTRACT FROM AUTHOR]

Silica-based sol-gel and bioglass materials are used in a variety of biomedical applications including the surface modification of orthopedic implants and tissue engineering scaffolds. In this work, a simple system for vapor depositing silica sol-gel nano- and micro-particles onto substrates using nebulizer technology has been developed and characterized. Particle morphology, size distribution, and degradation can easily be controlled through key formulation and manufacturing parameters including water:alkoxide molar ratio, pH, deposition time, and substrate character. These particles can be used as a means to rapidly modify substrate surface properties, including surface hydrophobicity (contact angle changes >15°) and roughness (RMS roughness changes of up to 300 nm), creating unique surface topography. Ions (calcium and phosphate) were successfully incorporated into particles, and induced apatitie-like mineral formation upon exposure to simulated body fluid Preosteoblasts (MC3T3) cultured with these particles showed up to twice the adhesivity within 48 h when compared to controls, potentially indicating an increase in cell proliferation, with the effect likely due to both the modified substrate properties as well as the release of silica ions. This novel method has the potential to be used with implants and tissue engineering materials to influence cell behavior including attachment, proliferation, and differentiation via cell-material interactions to promote osteogenesis. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. [ABSTRACT FROM AUTHOR]

Interfacial fibrosis is known to dramatically decrease the lifespan, stability, and function of biomedical implants and bone-anchored prosthetics. Bioactive coatings aimed at mitigating fibrous adhesions are one of the approaches to alleviate the problem. In this paper, we are developing a bioactive coating based upon a magnetoelastic (ME) material that vibrates in response to an ac magnetic field. In order to establish these coatings for this purpose, the ME material was first rendered bioactive through the sequential addition of polyurethane and chitosan thin films. Indirect live/dead assays were performed showing increased cell viability for polyurethane and chitosan-coated sensors compared to the uncoated controls. Direct adhesion experiments were performed to test the response of fibroblasts cultured on static and vibrated ME materials. Results showed cells adherent to static but not vibrated coatings. Detached cells showed no viability loss compared to controls. The finding that submicrometer ME vibrations can prevent cell adhesion in vitro without inducing cell death suggests the potential of these coatings to effectively control interfacial fibrosis. Future work will address the effect of vibrations on cell morphology and local gene expression in vitro, as well as fibrous tissue formation in vivo. [ABSTRACT FROM PUBLISHER]

Magnetoelastic (ME) materials have many advantages for use as sensors and actuators due to their wireless, passive nature. This paper describes the application of ME materials as biodegradable implants with controllable degradation rates. Experiments have been conducted to show that degradation rates of ME materials are dependent on the material compositions. In addition, it was shown that the degradation rates of the ME materials can be controlled remotely by applying a magnetic field, which causes the ME materials to generate low-magnitude vibrations that hasten their degradation rates. Another concern of ME materials for medical applications is biocompatibility. Indirect cytotoxicity analyses were performed on two types of ME materials: Metglas™ 2826 MB (FeNiMoB) and iron–gallium alloy. While results indicate Metglas is not biocompatible, the degradation products of iron–gallium materials have shown no adverse effects on cell viability. Overall, these results present the possibility of using ME materials as biodegradable, magnetically-controlled active implants. [ABSTRACT FROM AUTHOR]

Hydroxyl radical ( • OH) is a potent reactive oxygen species with the ability to degrade hazardous organic compounds, kill bacteria, and inactivate viruses. However, an off-the-shelf, portable, and easily activated biomaterial for generating • OH does not exist. Here, microgels were functionalized with catechol, an adhesive moiety found in mussel adhesive proteins, and hematin (HEM), a hydroxylated Fe 3+ ion-containing porphyrin derivative. When the microgel was hydrated in an aqueous solution with physiological pH, molecular oxygen in the solution oxidized catechol to generate H 2 O 2 , which was further converted to • OH by HEM. The generated • OH was able to degrade organic dyes, including orange II and malachite green. Additionally, the generated • OH was antimicrobial against both gram-negative ( Escherichia coli ) and gram-positive ( Staphylococcus epidermidis ) bacteria with the initial concentration of 10 6 -10 7 CFU/mL. These microgels also reduced the infectivity of a non-enveloped porcine parvovirus and an enveloped bovine viral diarrhea virus by 3.5 and 4.5 log reduction values, respectively (99.97-99.997% reduction in infectivity). These microgels were also functionalized with positively charged [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC), which significantly enhanced the antibacterial and antiviral activities through electrostatic interaction between the negatively charged pathogens and the microgel. These microgels can potentially serve as a lightweight and portable source of disinfectant, for an on-demand generation of • OH with a wide range of applications.

The development of biomaterials for the restoration of the normal tissue structure⁻function relationship in pathological conditions as well as acute and chronic injury is an area of intense investigation. More recently, the use of tailored or composite hydrogels for tissue engineering and regenerative medicine has sought to bridge the gap between natural tissues and applied biomaterials more clearly. By applying traditional concepts in engineering composites, these hydrogels represent hierarchical structured materials that translate more closely the key guiding principles required for improved recovery of tissue architecture and functional behavior, including physical, mass transport, and biological properties. For tissue-engineering scaffolds in general, and more specifically in composite hydrogel materials, each of these properties provide unique qualities that are essential for proper augmentation and repair following disease and injury. The broad focus of this review is on physical properties in particular, static and dynamic mechanical properties provided by composite hydrogel materials and their link to native tissue architecture and, ultimately, tissue-specific applications for composite hydrogels.

A system was developed for real-time, in vivo investigation of the relationship between local cell-level nano-mechanical perturbation and cell response to chemical-physical biomaterial surface properties. The system consisted of a magnetoelastic (ME) layer that could be remotely set to vibrate, at submicron levels, at a predetermined amplitude and profile. Experiments result indicated that submicron localized vibrations coupled with tailored biomaterial surface properties could selectively control cellular adhesion and possibly guide phenotypic gene expression. Practical application of this system includes modulation and monitoring of the surface of implantable biomaterials. The ME based vibrational system is the first of its kind for use in vitro for culture based mechanical testing, which could be readily deployed in situ as an in vivo system to apply local mechanical loads. It could be applied to specific implant surface sites and then subsequently sealed prior to long-term implantation. The potential advantage of this system over other similar approaches is that the system is translatable--the functional layer can serve as a "cellular workbench" material but could also be adapted and applied to the surface of implantable biomaterials and devices.