Introducing a Semi-Coated Model to Investigate Antibacterial Effects of Biocompatible Polymers on Titanium Surfaces

Peri-implant infections from bacterial biofilms on artificial surfaces are a common threat to all medical implants. They are a handicap for the patient and can lead to implant failure or even life-threatening complications. New implant surfaces have to be developed to reduce biofilm formation and to improve the long-term prognosis of medical implants. The aim of this study was (1) to develop a new method to test the antibacterial efficacy of implant surfaces by direct surface contact and (2) to elucidate whether an innovative antimicrobial copolymer coating of 4-vinyl-N-hexylpyridinium bromide and dimethyl(2-methacryloyloxyethyl) phosphonate (VP:DMMEP 30:70) on titanium is able to reduce the attachment of bacteria prevalent in peri-implant infections. With a new in vitro model with semi-coated titanium discs, we were able to show a dramatic reduction in the adhesion of various pathogenic bacteria (Streptococcus sanguinis, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis), completely independently of effects caused by soluble materials. In contrast, soft tissue cells (human gingival or dermis fibroblasts) were less affected by the same coating, despite a moderate reduction in initial adhesion of gingival fibroblasts. These data confirm the hypothesis that VP:DMMEP 30:70 is a promising antibacterial copolymer that may be of use in several clinical applications.     

CR摄影技术在皮下埋植剂取出术中的应用价值

目的探讨CR摄影技术在皮下埋植剂取出术中的应用价值。方法在对584例育龄妇女进行左炔诺孕酮硅胶棒皮下埋植避孕剂(简称皮下埋植剂)的取出术中,有12例在取出时,出现取出困难。取出前常规消毒,在受术者的上臂内缘皮肤触摸,能触及皮下埋植剂,然后在上臂内侧缘肘关节上方3.0cm处皮肤上做一切口,进行皮下埋植剂的取出术,取出1根后,另1根反复寻找仍不见皮下埋植剂,然后拍上臂正、侧位CR片。结果在受术者上臂内侧缘肘关节上方3.0cm肌层深0.6cm处可见一纵形长约4.5cm直径0.3cm的管状阴影,长度直径均符合皮下埋植剂。结论 CR摄影技术能准确定位皮下埋植剂,尤其是侧位片定位更为准确。使手术医生能顺利取出皮下埋植剂,减少受术者痛苦,因此有推广价值。     

A review of surface topographical modification strategies of 3Y-TZP: Effect in the physicochemical properties,microstructure, mechanical reliability,and biological response

The development of zirconia dental implants has become increasingly popular over the last years due to the outstanding mechanical properties, superior aesthetic appearance and high biocompatibility of this material. However, premature implant failure as a result of an incomplete osseointegration still represents a major concern. In this sense, surface modifications have been applied to dental zirconia to improve the biological interactions of the implant with the surrounding tissue. Nevertheless, surface modification of zirconia is challenging due to the formation of a monoclinic phase associated with ageing and loss of mechanical integrity. This review focuses on the most common surface topographical modification strategies currently applied to zirconia, namely grinding, sandblasting, chemical etching and laser treatment. A comprehensive and comparative analysis has been performed to assess the effects of these techniques on the physicochemical properties, mechanical performance, hydrothermal degradation behavior and biological response of the modified surfaces.     

Nanocharacterization in Dentistry

About 80% of US adults have some form of dental disease. There are a variety of new dental products available, ranging from implants to oral hygiene products that rely on nanoscale properties. Here, the application of AFM (Atomic Force Microscopy) and optical interferometry to a range of dentistry issues, including characterization of dental enamel, oral bacteria, biofilms and the role of surface proteins in biochemical and nanomechanical properties of bacterial adhesins, is reviewed. We also include studies of new products blocking dentine tubules to alleviate hypersensitivity; antimicrobial effects of mouthwash and characterizing nanoparticle coated dental implants. An outlook on future “nanodentistry” developments such as saliva exosomes based diagnostics, designing biocompatible, antimicrobial dental implants and personalized dental healthcare is presented.     

Carbon Nanotubes: Biocompatibility of Immobilized Aligned Carbon Nanotubes (Small 8/2011)

In vivo host responses to an electrode‐like array of aligned carbon nanotubes (ACNTs) embedded within a biopolymer sheet are reported. This biocompatibility study assesses the suitability of immobilized carbon nanotubes for bionic devices. Inflammatory responses and foreign‐body histiocytic reactions are not substantially elevated when compared to negative controls following 12 weeks implantation. A fibrous capsule isolates the implanted ACNTs from the surrounding muscle tissue. Filamentous nanotube fragments are engulfed by macrophages, and globular debris is incorporated into the fibrous capsule with no further reaction. Scattered leukocytes are observed, adherent to the ACNT surface. These data indicate that there is a minimal local foreign‐body response to immobilized ACNTs, that detached fragments are phagocytosed into an inert material, and that ACNTs do not attract high levels of surface fouling. Collectively, these results suggest that immobilized nanotube structures should be considered for further investigation as bionic components.     

Compression molding of biodegradable drug‐eluting implants for sustained release of metronidazole and doxycycline

The purpose of this report was to develop solvent‐free biodegradable drug‐eluting implants that provide sustained release of metronidazole and doxycycline. The drug‐eluting implants were prepared using the compression molding technique. To fabricate the implants, polylactide‐polyglycolide copolymers were premixed with metronidazole or doxycycline. The mixture was then compression molded and sintered to form implants of various sizes and geometries. An elution method and an HPLC assay were used to characterize the in vitro release rates of the antibiotics over a 28‐day period. A bacterial inhibition test was also carried out to determine the bioactivity of released antibiotics. The concentrations of both metronidazole and doxycycline were much greater than the minimum inhibitory concentration of Escherichia coli for up to 3 and 4 weeks, respectively, and the bioactivities of the antibiotics remained high after the fabrication process. Furthermore, the initial burst could be minimized and the release rate could be reduced by increasing the size of the implants and by adopting low drug to polymer ratios. By using this compression molding technique and appropriate processing parameters, we will be able to fabricate biodegradable implants of various types of antibacterial drugs for long‐term local deliveries. Eventually, biodegradable drug‐eluting implants may be used to treat various periodontal diseases. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Transmission electron microscopy of the interface between bone and pseudowollastonite implant

This paper reports on the structural morphology of the interface in vivo between implants composed of bioactive synthetic pseudowollastonite ceramic and bone in rat tibias. Thin sections of the interfaces were examined after 6 and 8 weeks of implantation period in a high resolution transmission electron microscope up to the lattice plane resolution level.
The interfaces developed normal biological and chemical activities and remained reactive over the 8-week period. The regions showing direct bone tissue bonding to the implant contained nanocrystals of hydroxyapatite-like phase growing epitaxially across the interface in the [002] direction. The nanocrystals were also identified in the bone tissue formed in the interfacial area.
The reactivity of the implant caused in the first instance formation of an amorphous woven type of bone, which transformed into a crystalline lamellar type containing collagen fibres. The Ca/P ratio of the interfacial region was found to be between 1.67 in the mature bone tissue formed about 5 µm from the interface, and 2.06 in the regions right at the interface.     

An active microphotodiode array of oscillating pixels for retinal stimulation

We have developed an active microphotodiode array (MPDA) for retinal stimulation. The unique feature of the device is that each pixel acts as an independent oscillator, whose frequency is controlled by the incident light intensity. The design is based on a double inverter relaxation oscillator, and the photodiodes are of PIN-type. These oscillating pixels stimulate the nervous tissue with bipolar pulses. The prototype stimulator chips are realized in standard 0.35 μm CMOS technology. The reported preliminary data and performance demonstrate the potential of the new concept for future retinal prostheses.     

A TiO2‐Binding Protein isolated from Rhodococcus Strain GIN‐1 (NCIMB 40340) – Purification,Properties and Potential Applications

A Rhodocuccus strain (Rh. GIN1, NCIMB 40340), which is capable of adsorption to titanium dioxide (TiO₂) and TiO₂‐containing coal fly ash particles, has been isolated previously in our Lab. Selectivity experiments showed that the bacterium is capable of adsorption to other metal oxides as well (e.g. magnetite and Al₂O₃) but at lower affinities. The bacterium binds tightly both to rutile and anatase TiO₂. In electronmicrograms the formation of “bridge‐like” structures between the bacterium and the oxide is observed. A specific protein fraction, located on the cell wall of the bacterium was isolated from the bacterium. This protein was found to adhere strongly to TiO₂ particles at high salt concentrations, similarly to the binding to TiO₂ of the intact bacteria. TiO₂ (rutile) was found to bind the protein faster, stronger and at a higher capacity than the anatase isoform. The 55 kDa Ti‐Binding Protein (TiBP) was isolated from the bacteria after homogenization by French Press. It was purified by affinity chromatography on TiO₂ particles, hydrophobic chromatography on a Fractogel‐propyl column and gel filtration on a Superdex G‐200 column. The same protein was isolated from the bacteria by treatment with mutanolysin, an enzyme which is commonly used to retrieve cell‐wall proteins from Gram‐positive bacteria, demonstrating the outer cell location of the protein in Rh. GIN1. TiBP exhibits metal oxide binding selectivity similar to that of the intact bacterium, namely TiO₂>ZnO>Al₂O₃ >Fe₂O₃(magnetite). Hydrophobic forces seem to dominate the interactions of the protein with TiO₂ as its binding capability is greatly enhanced in the presence of high concentrations of NaCl and its desorption requires high concentrations of urea and SDS. These features differentiate TiBP from other proteins known to adsorb TiO₂ (such as hemoglobin, cytochrome c and bovine serum albumin), mainly by weak, charge‐based interactions.