The synthesis and characterization of nanophase hydroxyapatite using a novel dispersant-aided precipitation method

The synthesis of nanophase hydroxyapatite (nHA) is of importance in the field of biomaterials and bone tissue engineering. The bioactive and osteoconductive properties of nHA are of much benefit to a wide range of biomedical applications such as producing bone tissue engineered constructs, coating medical implants, or as a carrier for plasmid DNA in gene delivery. This study aimed to develop a novel low-temperature dispersant-aided precipitation reaction to produce nHA particles (

Examination of surface properties and in vitro biological performance of amorphous diamond-like carbon-coated polyurethane

Despite the emerging use of diamond-like carbon (DLC) as a coating for medical devices, few studies have examined the resistance of DLC coatings onto medical polymers to both microbial adherence and encrustation. In this study, amorphous DLC of a range of refractive indexes (1.7-1.9) and thicknesses (100-600 nm) was deposited onto polyurethane, a model polymer, and the resistance to microbial adherence (Escherichia coli; clinical isolate) and encrustation examined using in vitro models. In comparison to the native polymer, the advancing and receding contact angles of DLC-coated polyurethane were lower, indicating greater hydrophilic properties. No relationship was observed between refractive index, thickness, and advancing contact angle, as determined using multiple correlation analysis. The resistances of the various DLC-coated polyurethane films to encrustation and microbial adherence were significantly greater than that to polyurethane; however, there were individual differences between the resistances of the various DLC coatings. In general, increasing the refractive index of the coatings (100 nm thickness) decreased the resistance of the films to both hydroxyapatite and struvite encrustation and to microbial adherence. Films of lower thicknesses (100 and 200 nm; of defined refractive index, 1.8), exhibited the greatest resistance to encrustation and to microbial adherence. In conclusion, this study has uniquely illustrated both the microbial antiadherence properties and resistance to urinary encrustation of DLC-coated polyurethane. The resistances to encrustation and microbial adherence were substantial, and in light of this, it is suggested that DLC coatings of low thickness and refractive index show particular promise as coatings of polymeric medical devices. (c) 2006 Wiley Periodicals, Inc.

Evaluation of a poly(vinyl pyrollidone)-coated biomaterial for urological use

The associated problems of bacterial biofilm formation and encrustation that may cause obstruction or blockage of urethral catheters and ureteral stents often hinders the effective use of biomaterials within the urinary tract. In this in vitro study, we have investigated the surface properties of a hydrophilic polyvinyl pyrollidone) (PVP)-coating applied to polyurethane and determined its suitability for use as a urinary tract biomaterial by comparing its lubricity and ability to resist bacterial adherence and encrustation with that of uncoated polyurethane and silicone. The PVP-coated polyurethane was significantly more hydrophilic and more lubricious than either uncoated polyurethane or silicone. Adherence of a hydrophilic Escherichia coli isolate to PVP-coated polyurethane and uncoated polyurethane was similar but significantly less than adherence to silicone. Adherence of a hydrophobic Enterococcus faecalis isolate to PVP-coated polyurethane and silicone was similar but was significantly less than adherence to uncoated polyurethane. Struvite encrustation was similar on the PVP-coated polyurethane and silicone but significantly less than on uncoated polyurethane. Furthermore, hydroxyapatite encrustation was significantly less on the PVP-coated polyurethane than on either uncoated polyurethane or silicone. The results suggest that the PVP-coating could be useful in preventing complications caused by bacterial biofilm formation and the deposition of encrustation on biomaterials implanted in the urinary tract and, therefore, warrants further evaluation. (C) 2002 Elsevier Science Ltd. All rights reserved.

Effects of plastic coating on K-alpha yield from ultra-short pulse

A study of the K-alpha radiation emitted from Ti foils irradiated with intense, similar to0.2 J, 67 fs, 800 nm laser pulses, scanning a range of intensities (similar to10(15)-10(18) W cm(-2)), is reported. The brightness of single-shot K-alpha line emission from the front of the targets is recorded. The yield from bare titanium (Ti) is compared to that from plastic (parylene-E) coated Ti. It is demonstrated that, for a defocused beam, a thin layer of plastic increases the yield.

Conformal oxide coating of carbon nanotubes

The International Roadmap for Ferroelectric Memories requires three-dimensional integration of high-dielectric materials onto metal interconnects or bottom electrodes by 2010. Here, we demonstrate the possibility of conformally coating carbon nanotubes with high-dielectric oxide as a first step toward ultrahigh integration density of three-dimensional ferroelectric random access memories.

Low-pressure synthesis and characterisation of hydroxyapatite derived from mineralise red algae

There is a great need to design functional bioactive substitute materials capable of surviving harsh and diverse conditions within the human body. Calcium-phosphate ceramics, in particular hydroxyapatite are well established substitute materials for orthopaedic and dental applications. The aim of this study was to develop a bioceramic from alga origins suitable for bone tissue application. This was achieved by a novel synthesis technique using ambient pressure at a low temperature of 100 degrees C in a highly alkaline environment. The algae was characterised using SEM, BET, XRD and Raman Spectroscopy to determine its physiochemical properties at each stage. The results confirmed the successful conversion of mineralised red alga to hydroxyapatite, by way of this low-pressure hydrothermal process. Furthermore, the synthesised hydroxyapatite maintained the unique micro-porous structure of the original algae, which is considered beneficial in bone repair applications. (C) 2007 Elsevier B.V. All rights reserved.

Development of composite tissue scaffolds containing naturally sourced mircoporous hydroxyapatite

The aims of this work were to investigate the conversion of a marine alga into hydroxyapatite (HA), and furthermore to design a composite bone tissue engineering scaffold comprising the synthesised HA within a porous bioresorbable polymer. The marine alga Phymatolithon calcareum, which exhibits a calcium carbonate honeycomb structure, with a natural architecture of interconnecting permeable pores (microporosity 4-11 mu m), provided the initial raw material for this study. The objective was to convert the alga into hydroxyapatite while maintaining its porous morphology using a sequential pyrolysis and chemical synthesis processes. Semi-quantitative XRD analysis of the post-hydrothermal material (pyrolised at 700-750 degrees C), indicated that the calcium phosphate (CaP) ceramic most likely consisted of a calcium carbonate macroporous lattice, with hydroxyapatite crystals on the surface of the macropores. Cell visibility (cytotoxicity) investigations of osteogenic cells were conducted on the CaP ceramic (i.e., the material post-hydrothermal analysis) which was found to be non-cytotoxic and displayed good biocompatibility when seeded with MG63 cells. Furthermore, a hot press scaffold fabrication technique was developed to produce a composite scaffold of CaP (derived from the marine alga) in a polycaprolactone (PCL) matrix. A salt leaching technique was further explored to introduce macroporosity to the structure (50-200 mu m). Analysis indicated that the scaffold contained both micro/macroporosity and mechanical strength, considered necessary for bone tissue engineering applications. (C) 2008 Published by Elsevier B.V.

High-solid-content hydroxyapatite slurry for the production of bone substitute scaffolds

Key to various bone substitute scaffold production techniques is the development of free-flowing ceramic slurry with optimum theological properties. The aim is to achieve a colloidal suspension with as high a solid content as possible while maintaining a low viscosity which easily penetrates the pores of relevant sacrificial templates. The following investigation describes the optimization of a hydroxyapatite slip and demonstrates its potential application in scaffold production. Using predominantly spherical particles of hydroxyapatite of between 0.82 mu m and 16.2 mu m, coupled with a 2 wt % addition of the anionic polyelectrolyte, ammonium polyacrylate, an 80 wt % (55.9 vol %) hydroxyapatite solid loaded slip with a viscosity of approximately 126 mPa s has been developed. Its ability to infiltrate and replicate porous preforms has been shown using polyurethane foam. The enhanced particle packing achieved has allowed for the production of scaffolds with highly dense and uniform grain structures. The results represent a significant improvement in current slurry production techniques and can be utilized to develop high-density ceramic bone substitute scaffolds.

Performance of calcium deficient hydroxyapatite-polyglycolic acid composites: An in vitro study

The strategic incorporation of bioresorbable polymeric additives to calcium-deficient hydroxyapatite cement may provide short-term structural reinforcement and modify the modulus to closer match bone. The longer-term resorption properties may also be improved, creating pathways for bone in-growth. The aim of this study was to investigate the resorption process of a calcium phosphate cement system containing either in polyglycolic acid tri-methylene carbonate particles or polyglycolic acid fibres. This was achieved by in vitro aging in physiological conditions (phosphate buffered solution at 37°C) over 12 weeks. The unreinforced CPC exhibited an increase in compressive strength at 12 weeks, however catastrophic failure was observed above a critical loading. The fracture behaviour of cement was improved by the incorporation of PGA fibres; the cement retained its cohesive structure after critical loading. Gravimetric analysis and scanning electron microscopy showed a large proportion of the fibres had resorbed after 12 weeks allowing for the increased cement porosity, which could facilitate cell infiltration and faster integration of natural bone. Incorporating the particulate additives in the cement did not provide any mechanism for mechanical property augmentation or did not demonstrate any appreciable level of resorption after 12 weeks.