Biosynthesis of silver nanoparticles using indigenous Xanthorrhoea glauca leaf extract and their antibacterial activity against Escherichia coli and Staphylococcus epidermis

Background: This study for the first time presents an environmentally friendly, room temperature procedure for synthesizing silver (Ag) nanoparticles via the leaf extract taken from Xanthorrhoea glauca. Methods: The simple and straightforward green chemistry based technique uses the leaf extract that acts as both reducing agent and capping agent to produce Ag nanoparticles which are subsequently quantified using advanced characterisation techniques. In addition, antibacterial studies were conducted using the Kirby-Bauer sensitivity method. Results: Advanced characterisation revealed the synthesised particles had a variety of shapes including cubes, truncated triangular and hexagonal plates, and ranged in size from 50 nm up to 200 nm. The Gram-positive bacteria Staphylococcus epidermis showed the maximum zone of inhibition at 11 mm. Conclusions: The study has shown that the leaf extract was able to synthesis Ag nanoparticles with antibacterial activity against Escherichia coli and Staphylococcus epidermis

Growth and corrosion behaviour of amorphous micrometre scale calcium phosphate coatings on magnesium substrates

Amorphous calcium phosphate (ACP) coatings were formed on magnesium substrates via a straightforward electrochemical technique in order to improve the corrosion resistance of the substrates. X-ray diffraction spectroscopy and microscopy techniques were used to investigate the size, morphology, composition and structure of the ACP coatings. Analysis of the ACP coatings revealed the presence of micrometre scale fissures and tubular structures. Despite the presence of these features, the coatings were still capable of significantly reducing the corrosion rate in both PBS and Ringer’s solutions. Ringer’s solution was found to be the most aggressive towards Mg substrates with a corrosion rate of 3.828 mm/yr. However, after electrochemical treatment, the corrosion rate of substrates coated with ACP was reduced to 0.557 mm/yr. The significant improvement in corrosion resistance is a first step in controlling the corrosion rate of biodegradable Mg substrates for potential use in hard tissue applications

Chemical immersion coatings to improve biological degradability of magnesium substrates for potential orthopaedic applications

Historically, cobalt-chromium, stainless steel and titanium alloys have been the main principal materials used in a variety of medical procedures for load-bearing implants in the body. Magnesium and magnesium-based alloys have the potential to be used as short-term structural support during the healing process of damaged hard tissues and diseased bone. Unlike traditional biologically compatible metals, which are not biologically degradable, magnesium based alloys offer both biological degradability and biological absorbability. Despite the many advantages offered by magnesium, its rapid degradation rate in the highly aggressive and corrosive body fluid environment has severely limited its present day medical application. This article reviews the chemical immersion technique for producing calcium phosphate coatings on magnesium substrates for slowing down the degradation rate while maintaining the biological compatibility and absorbability

Growth of flower-like Brushite structures on magnesium substrates and their subsequent low temperature transformation to hydroxyapatite

Dicalcium phosphate dihydrate (DCPD) Brushite coatings composed of flower-like structures were formed on magnesium substrates via a straightforward chemical immersion technique in order to slow down the corrosion rate of the metallic substrates. Moreover, the synthesised DCPD coatings were also converted to hydroxyapatite (HAP) coating using a low-temperature hydrothermal process to further investigate their ability to reduce the corrosion rate of the substrates in phosphate buffer saline (PBS) and Ringer’s solutions. Degradation studies found DCPD coatings were capable of providing the most significant reduction in the corrosion rate of around 0.100 mm/yr compared to 3.828 mm/yr for the uncoated substrates soaked in Ringer’s solution at 37ºC

Synthesis of a bone like composite material derived from waste pearl oyster shells for potential bone tissue bioengineering applications

Background: Hydroxyapatite is generally considered a viable substitute for bone in a number of medical procedures such as bone repair, bone augmentation and coating metal implants. Unfortunately, hydroxyapatite has poor mechanical properties that make it unsuitable for many load bearing applications. Methods: In the present work various grades of finely crushed Pinctada maxima (pearl oyster shell) were combined with a nanometer scale hydroxyapatite powder to form novel composite materials. A comparative study was made between the various powder based composites synthesized. The crystalline structure and morphology of the various powder based composites were investigated using X-ray diffraction and field emission scanning electron microscopy. The composite materials were also evaluated and characterized. Results: Manufactured hydroxyapatite powders were composed of crystalline spherical/granular particles with a mean size of 30 nm. Also produced were hydroxyapatite and finely crushed calcium carbonate from Pinctada maxima (pearl oyster shell) powder mixtures. Hydroxyapatite coatings produced on Pinctada maxima nacre substrates were investigated and their surface characteristics reported. Conclusions: Pinctada maxima nacre pre-treated with sodium hypo chlorate before hydroxyapatite deposition produced a superior coating and could be used for bone tissue engineering. But further in vitro and in vivo studies are needed to validate the biocompatibility and long term stability of this composite coating

Synthesis of a hydroxyapatite nanopowder via ultrasound irradiation from calcium hydroxide powders for potential biomedical applications

Nanoscale hydroxyapatite based ceramics are a relatively new form of materials that are currently being investigated for a number of potential biomedical applications. This study reports on a straightforward wet chemical method that uses calcium hydroxide and phosphoric acid as precursors. After chemical synthesis a conventional thermal treatment was used to produce an ultrafine hydroxyapatite nanopowder. Varying ultrasonic power between zero and 400 W during the synthesis process produced crystallite sizes ranging from 15.4 nm down to 12.2 nm. The morphology of particles synthesized under the influence of ultrasonic irradiation was predominantly spherical and granular. Also present were a small number of irregular shaped plates. Energy dispersive spectroscopy revealed the samples had a Ca:P ratio of 1.66, which was very close to the ideal value of 1.67. FT-IR studies identified functional groups and confirmed the results of the X-ray diffraction data that the powders were indeed composed of nanoscale hydroxyapatite

Biogenic synthesis of silver nanoparticles via indigenous Anigozanthos manglesii, (red and green kangaroo paw) leaf extract and its potential antibacterial activity

Background: Metallic silver nanoparticles with antibacterial properties were biosynthesised for the first time using an indigenous Australian plant Anigozanthos manglesii. Methods: A practical, straight-forward and eco-friendly technique used the Anigozanthos manglesii leaf extract, which acted as both reducing and capping agents to create stable silver nanoparticles. The antibacterial activities of the nanoparticles were investigated using the Kirby-Bauer sensitivity method. Results: Characterisation revealed the nanoparticles ranged in size from 50 nm up to 150 nm, and their morphologies included cubes, triangular plates and hexagonal plates. Antibacterial studies revealed Deinococcus was sensitive and susceptible to the biosynthesised nanoparticles. Escherichia coli and Staphylococcus Epidermis strains were also found to be less susceptible to the silver nanoparticles. Conclusions: The present study has shown that silver nanoparticles biosynthesised using Anigozanthos manglesii leaf extracts have antibacterial activity against Deinococcus, Escherichia coli and Staphylococcus Epidermis bacterial strain

Nanostructures and super-hydrophobic properties on the leaves of an indigenous Australian plant Eucalyptus pleurocarpa

This study presents the results of a topographical survey of the surface features found on the leaves of an indigenous Australian plant Eucalyptus pleurocarpa (Tallerack). Field emission scanning electron microscopy was used to examine the size and morphology of various micrometer and nanometre scale features presented on the leaf surface. In particular, the features formed by the epicuticular waxes were investigated and quantified. Analysis of water contact angle measurements carried out on the adaxial surface indicated that the leaf surface was super-hydrophobic (158.00 ± 4.30°), while the abaxial surface was found to be hydrophobic (150.20 ± 3.90°). Microscopy examination revealed that the leaf surfaces contained an array of stomata surrounded by a rugged surface region dominated by a rim and bumps. The stomata rims and surface bumps surrounding the stomata were adorned with nanometre scale pillar structures. On the adaxial surface the mean diameter of these pillar structures was estimated to be 300 ± 50 nm and lengths ranging from 1 to 7µm. While the self-cleaning experiments demonstrated that the Tallerack leaf could be effectively cleaned using a fine spray of water droplets that rolled over the surface picking up both hydrophilic (Ballotini microspheres) and hydrophobic (carbon black toner) contaminants

Biosynthesis of silver nanoparticles using indigenous Xanthorrhoea glauca leaf extract and their antibacterial activity against Escherichia coli and Staphylococcus epidermis

Background:This study for the first time presents an environmentally friendly, room temperature procedure for synthesizing silver (Ag) nanoparticles via the leaf extract taken from Xanthorrhoea glauca.Methods: The simple and straightforward green chemistry based technique uses the leaf extract that acts as both reducing agent and capping agent to produce Ag nanoparticles which are subsequently quantified using advanced characterisation techniques. In addition, antibacterial studies were conducted using the Kirby-Bauer sensitivity method.Results: Advanced characterisation revealed the synthesised particles had a variety of shapes including cubes, truncated triangular and hexagonal plates, and ranged in size from 50 nm up to 200 nm. The Gram-positive bacteria Staphylococcus epidermis showed the maximum zone of inhibition at 11 mm.Conclusions: The study has shown that the leaf extract was able to synthesis Ag nanoparticles with antibacterial activity against Escherichia coli and Staphylococcus epidermis