ORCID Profile
0000-0002-0956-6145
Current Organisation
University of South Australia
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Publisher: Wiley
Date: 03-10-2022
Abstract: An ever‐present risk of medical device associated infection has driven a significant body of research toward development of novel anti‐infective materials. Surfaces bearing sharp nanostructures are an emerging technology to address this concern. The in vitro efficacy of antimicrobial nanostructures has previously been verified using single species cultures, but there remains a paucity of data to address the threat of infections containing more than one species. Polymicrobial infections are a concerning threat because they can complicate treatment, promote drug resistance, and harshen patient prognosis. In the present study, dual‐species cultures are employed to challenge the mechano‐bactericidal properties of nanostructured surfaces. Escherichia coli is used with either Staphylococcus aureus or Enterococcus faecalis due to their clinical relevance in implant associated infection. Despite the presence of two mixed species, a high rate of bactericidal activity is found. Interestingly, in the mixed culture containing Escherichia coli with Enterococcus faecalis , the nanostructured surface triggers a shift in species distribution to favor Enterococcus faecalis . Overall, this study highlights the potential for mechano‐bactericidal surfaces to minimize the burden of infections containing more than one species. It also serves as an enticing foundation for further research into more complex biointerfacial interactions.
Publisher: Springer Science and Business Media LLC
Date: 26-11-2013
DOI: 10.1038/NCOMMS3838
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5RA05206H
Abstract: A “super surface” with superhydrophobic, self-cleaning and bactericidal properties for use in medical devices, instruments and microfluidics is presented.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8TB03295E
Abstract: Inspired by the surface topography of cicada wings, Ti nanopillars were fabricated. The fabricated surfaces were bactericidal and cytocompatible.
Publisher: Springer Science and Business Media LLC
Date: 10-12-2014
Publisher: Elsevier BV
Date: 11-2014
Publisher: American Chemical Society (ACS)
Date: 22-05-2019
Publisher: Bentham Science Publishers Ltd.
Date: 08-2011
DOI: 10.2174/092986711796504673
Abstract: 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.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5NR04156B
Abstract: Recent advances in the field of topography driven antibacterial surfaces are presented. Micro-structured antibiofouling and nano-structured bactericidal surfaces are reviewed.
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.MIMET.2011.05.021
Abstract: Atomic force microscopy (AFM) is a technique that has long been employed in materials science, but is now increasingly being used in the biological sciences. AFM provides excellent topographical information on prokaryotic and eukaryotic cell surfaces, and the extracellular material produced by the cells. It helps to generate important data on the mechanical properties of cells, such as hardness and elasticity. AFM can also be used to measure the strength of adhesion, attraction, and repulsion forces between cells and surfaces or even between in idual molecules. Additionally, by combining AFM with other complementary techniques such as fluorescence microscopy or Raman spectroscopy, the chemistry of given surface structures can be identified. This review aims to provide an update on the AFM techniques currently used in cell biology studies, along with a description of the range of recently developed research methodologies in which AFM plays a key role.
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.COLSURFB.2018.02.036
Abstract: Neonatal cardiomyocytes cultured on flat surfaces are commonly used as a model to study cardiac failure of erse origin. A major drawback of such a system is that the cardiomyocytes do not exhibit alignment, organization and calcium transients, similar to the native heart. Therefore, there is a need to develop in vitro platforms that recapitulate the cellular microenvironment of the murine heart as organotypic models to study cardiovascular diseases. In this study, we report an engineered platform that mimics cardiac cell organization and function of the heart. For this purpose, microscale ridges were fabricated on silicon using ultraviolet lithography and reactive ion etching techniques. Physical characterization of the microstructures was done using scanning electron microscopy and atomic force microscopy. Cardiomyocytes grown on these micro-ridges showed global parallel alignment and elliptical nuclear morphology as observed in the heart. Interestingly, calcium currents traversed the engineered cardiomyocytes in a coordinated and directional manner. Moreover, the cardiomyocytes on the engineered substrates were found to be responsive to hypertrophic stimuli, as observed by the expression of a fetal gene, atrial natriuretic peptide and increase in calcium transients upon agonist treatment. Taken together, our work demonstrates that micro-ridges can be used to obtain cardiomyocyte response in vitro, which closely resembles mammalian heart.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0RA08878A
Abstract: Micro/nanostructured surfaces (MNSS) have shown the ability to inactivate bacterial cells by physical means.
Publisher: American Chemical Society (ACS)
Date: 31-08-2020
Publisher: Elsevier BV
Date: 02-2013
Publisher: American Chemical Society (ACS)
Date: 27-01-2021
Publisher: Springer Science and Business Media LLC
Date: 23-01-2017
DOI: 10.1038/SREP41118
Abstract: We have developed a chlorine based reactive ion etching process to yield randomly oriented anisotropic nanostructures that render the titanium metal surface ‘black’ similar to that of black silicon. The surface appears black due to the nanostructures in contrast to the conventional shiny surface of titanium. The nanostructures were found to kill bacteria on contact by mechanically rupturing the cells as has been observed previously on wings of certain insects. The etching was optimized to yield nanostructures of ≈1 μm height for maximal bactericidal efficiency without compromising cytocompatibility. Within 4 hours of contact with the black titanium surface, 95% ± 5% of E. coli, 98% ± 2% of P. aeruginosa , 92% ± 5% of M. smegmatis and 22% ± 8% of S. aureus cells that had attached were killed. The killing efficiency for the S. aureus increased to 76% ± 4% when the cells were allowed to adhere up to 24 hours. The black titanium supported the attachment and proliferation of human mesenchymal stem cells and augmented osteogenic lineage commitment in vitro . Thus, the bioinspired nanostructures on black titanium impart multi-biofunctional properties toward engineering the next-generation biomaterials for orthopedic implants.
Publisher: IOP Publishing
Date: 19-11-2020
Abstract: The interaction of bacteria on nanopatterned surfaces has caught attention since the discovery of the bactericidal property of cicada wing surfaces. While many studies focused on the inspiration of such surfaces, nanolithography-based techniques are seldom used due to the difficulties in fabricating highly dense (number of pillars per unit area), geometrical nanostructured surfaces. Here we present a systematic modelling approach for optimising the electron beam lithography parameters in order to fabricate biomimicked nanopillars of varying patterned geometries. Monte Carlo simulation was applied to optimize the beam energy and pattern design prior to the experimental study. We optimized the processing parameters such as exposure factor, write field size, pitch, the different types and thicknesses of the PMMA resist used, and the shape of the feature (circle or a dot) for the fabrication of nanopillars to achieve the best lift-off with repeatable result. Our simulation and experimental results showed that a circle design with a voltage of 30 kV and 602 nm thickness of PMMA 495 A4 as base layers and 65 nm of PMMA 950 A2 as top layer achieves the best results. The antibacterial activity was also validated on the representative fabricated titanium nanopillar surface. The surface with a base diameter of 94.4 nm, spike diameter of 12.6 nm, height of 115.6 nm, density of 43/ μ m 2 , aspect ratio of 2.16 and centre to centre distance of 165.8 nm was the optimum surface for antibacterial activity. Such a systematic design approach for fabrication of insect wing-mimicked closely packed nanopillars have not been investigated before which provides an excellent platform for biomedical Ti implants.
Publisher: Elsevier BV
Date: 2021
Publisher: American Chemical Society (ACS)
Date: 07-05-2020
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.COLSURFB.2022.112600
Abstract: Medical-grade titanium alloys used for orthopaedic implants are at risk from infections and complications such as wear and tear. We have recently shown that hydrothermally etched (HTE) nanostructures (NS) formed on the Ti6AlV4 alloy surfaces impart enhanced anti-bacterial activity which results in inhibited formation of bacterial biofilm. Although these titanium alloy nanostructures may resist bacterial colonisation, their frictional properties are yet to be understood. Orthopaedic devices are encapsulated by bone and muscle tissue. Contact friction between orthopaedic implant surfaces and these host tissues may trigger inflammation, osteolysis and wear. To address these challenges, we performed simulation of the contact behaviour between a smooth control Ti6Al4V alloy and HTE surfaces against a hardwearing SiO
Publisher: American Chemical Society (ACS)
Date: 04-10-2021
Abstract: Since the discovery of the bactericidal properties of cicada wing surfaces, there has been a surge in the number of studies involving antibacterial nanostructured surfaces (NSS). Studies show that there are many parameters (and thus, thousands of parameter combinations) that influence the bactericidal efficiency (BE) of these surfaces. Researchers attempted to correlate these parameters to BE but have so far been unsuccessful. This paper presents a meta-analysis and perspective on bactericidal NSS, aiming to identify trends and gaps in the literature and to provide insights for future research. We have attempted to synthesize data from a wide range of published studies and establish trends in the literature on bactericidal NSS. Numerous research gaps and findings based on correlations of various parameters are presented here, which will assist in the design of efficient bactericidal NSS and shape future research. Traditionally, it is accepted that BE of NSS depends on the bacterial Gram-stain type. However, this review found that factors beyond Gram-stain type are also influential. Furthermore, it is found that despite their higher BE, hydrophobic NSS are less commonly studied for their bactericidal effect. Interestingly, the impacts of surface hydrophobicity and roughness on the bactericidal effect were found to be influenced by a Gram-stain type of the tested bacteria. In addition, cell motility and shape influence BE, but research attention into these factors is lacking. It was found that hydrophobic NSS demonstrate more promising results than their hydrophilic counterparts however, these surfaces have been overlooked. Confirming the common belief of the influence of nanofeature diameter on bactericidal property, this analysis shows the feature aspect ratio is also decisive. NSS fabricated on silicon substrates perform better than their titanium counterparts, and the success of these silicon structures maybe attributed to the fabrication processes. These insights benefit engineers and scientists alike in developing next-generation NSS.
Publisher: Elsevier BV
Date: 06-2013
DOI: 10.1016/J.COLSURFB.2013.01.042
Abstract: Numerous natural surfaces possess superhydrophobicity and self-cleaning properties that would be extremely beneficial when applied in industry. Dragonfly wings are one ex le of such surfaces, and while their general surface structure is known, their precise chemical composition is not. Here, the epicuticular lipids of dragonfly wing membranes were characterized to investigate their significance in contributing to self-cleaning and superhydrophobic properties. After just 10s of lipid extraction using chloroform, the water contact angles exhibited by the wings decreased below the accepted threshold for superhydrophobicity (150°). Infrared spectra collected at the Australian Synchrotron contained characteristic absorption bands of amide, ester and aliphatic hydrocarbons moieties on the wing surfaces, the latter of which was decreased post-extraction with chloroform. GC-MS data analysis revealed that the epicuticular wax components were dominated by n-alkanes with even-numbered carbons, especially n-hexacosane, and palmitic acid. SEM and AFM data analysis conducted on the untreated and chloroform-extracted wing surfaces demonstrated that surface topography changed after extraction the surface nanostructure was progressively lost with extended extraction times. The data presented here indicate that epicuticular lipids contribute not only to self-cleaning and superhydrophobic properties through their inherent hydrophobic nature, but also by forming the physical structure of the wing surface. This knowledge will be extremely valuable for reconstruction of dragonfly wing structures as a biomimetic template.
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.TIBTECH.2013.01.017
Abstract: In this review we attempt to clarify the notion of what is meant by the term antibacterial surfaces and categorise the approaches that are commonly used in the design of antibacterial surfaces. Application of surface coatings and the modification of the surface chemistry of substrata are generally considered to be a chemical approach to surface modification (as are surface polymerisation, functionalisation, and derivatisation), whereas, modification of the surface architecture of a substrate can be considered a physical approach. Here, the antifouling and bactericidal effects of antibacterial surfaces are briefly discussed. Finally, several recent efforts to design a new generation of antibacterial surfaces, which are based on mimicking the surface nanotopography of natural surfaces, are considered.
Publisher: Informa UK Limited
Date: 17-01-2013
DOI: 10.1080/08927014.2012.757697
Abstract: Despite the volume of work that has been conducted on the topic, the role of surface topography in mediating bacterial cell adhesion is not well understood. The primary reason for this lack of understanding is the relatively limited extent of topographical characterisation employed in many studies. In the present study, the topographies of three sub-nanometrically smooth titanium (Ti) surfaces were comprehensively characterised, using nine in idual parameters that together describe the height, shape and distribution of their surface features. This topographical analysis was then correlated with the adhesion behaviour of the pathogenic bacteria Staphylococcus aureus and Pseudomonas aeruginosa, in an effort to understand the role played by each aspect of surface architecture in influencing bacterial attachment. While P. aeruginosa was largely unable to adhere to any of the three sub-nanometrically smooth Ti surfaces, the extent of S. aureus cell attachment was found to be greater on surfaces with higher average, RMS and maximum roughness and higher surface areas. The cells also attached in greater numbers to surfaces that had shorter autocorrelation lengths and skewness values that approached zero, indicating a preference for less ordered surfaces with peak heights and valley depths evenly distributed around the mean plane. Across the sub-nanometrically smooth range of surfaces tested, it was shown that S. aureus more easily attached to surfaces with larger features that were evenly distributed between peaks and valleys, with higher levels of randomness. This study demonstrated that the traditionally employed litudinal roughness parameters are not the only determinants of bacterial adhesion, and that spatial parameters can also be used to predict the extent of attachment.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR03424B
Abstract: The array highly efficiently promotes cardiomyogenic commitment of stem cells via integrin-mediated signalling compared to the smooth surface and is a potential platform for ex vivo differentiation of stem cells for cell therapy in cardiac tissue repair and regeneration.
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier BV
Date: 11-2012
DOI: 10.1016/J.CIS.2012.06.015
Abstract: Substratum surface roughness is known to be one of the key factors in determining the extent of bacterial colonization. Understanding the way by which the substratum topography, especially at the nanoscale, mediates bacterial attachment remains ambiguous at best, despite the volume of work available on the topic. This is because the vast majority of bacterial attachment studies do not perform comprehensive topographical characterization analyses, and typically consider roughness parameters that describe only one aspect of the surface topography. The most commonly reported surface roughness parameters are average and root mean square (RMS) roughness (R(a) and R(q) respectively), which are both measures of the typical height variation of the surface. They offer no insights into the spatial distribution or shape of the surface features. Here, a brief overview of the current state of research on topography-mediated bacterial adhesion is presented, as well as an outline of the suite of roughness characterization parameters that are available for the comprehensive description of the surface architecture of a substratum. Finally, a set of topographical parameters is proposed as a new standard for surface roughness characterization in bacterial adhesion studies to improve the likelihood of identifying direct relationships between substratum topography and the extent of bacterial adhesion.
Publisher: American Chemical Society (ACS)
Date: 14-10-2022
DOI: 10.1021/ACSBIOMATERIALS.2C00540
Abstract: Titanium and its alloys are frequently the biomaterial of choice for dental implant applications. Although titanium dental implants have been utilized for decades, there are yet unresolved issues pertaining to implant failure. Dental implant failure can arise either through wear and fatigue of the implant itself or peri-implant disease and subsequent host inflammation. In the present report, we provide a comprehensive review of titanium and its alloys in the context of dental implant material, and how surface properties influence the rate of bacterial colonization and peri-implant disease. Details are provided on the various periodontal pathogens implicated in peri-implantitis, their adhesive behavior, and how this relationship is governed by the implant surface properties. Issues of osteointegration and immunomodulation are also discussed in relation to titanium dental implants. Some impediments in the commercial translation for a novel titanium-based dental implant from "bench to bedside" are discussed. Numerous in vitro studies on novel materials, processing techniques, and methodologies performed on dental implants have been highlighted. The present report review that comprehensively compares the in vitro , in vivo , and clinical studies of titanium and its alloys for dental implants.
Publisher: International Union of Crystallography (IUCr)
Date: 22-03-2013
DOI: 10.1107/S0909049513004056
Abstract: The wings of some insects, such as cicadae, have been reported to possess a number of interesting and unusual qualities such as superhydrophobicity, anisotropic wetting and antibacterial properties. Here, the chemical composition of the wings of the Clanger cicada ( Psaltoda claripennis ) were characterized using infrared (IR) microspectroscopy. In addition, the data generated from two separate synchrotron IR facilities, the Australian Synchrotron Infrared Microspectroscopy beamline (AS-IRM) and the Synchrotron Radiation Center (SRC), University of Wisconsin-Madison, IRENI beamline, were analysed and compared. Characteristic peaks in the IR spectra of the wings were assigned primarily to aliphatic hydrocarbon and amide functionalities, which were considered to be an indication of the presence of waxy and proteinaceous components, respectively, in good agreement with the literature. Chemical distribution maps showed that, while the protein component was homogeneously distributed, a significant degree of heterogeneity was observed in the distribution of the waxy component, which may contribute to the self-cleaning and aerodynamic properties of the cicada wing. When comparing the data generated from the two beamlines, it was determined that the SRC IRENI beamline was capable of producing higher-spatial-resolution distribution images in a shorter time than was achievable at the AS-IRM beamline, but that spectral noise levels per pixel were considerably lower on the AS-IRM beamline, resulting in more favourable data where the detection of weak absorbances is required. The data generated by the two complementary synchrotron IR methods on the chemical composition of cicada wings will be immensely useful in understanding their unusual properties with a view to reproducing their characteristics in, for ex le, industry applications.
Publisher: Public Library of Science (PLoS)
Date: 09-07-2013
Publisher: Wiley
Date: 13-02-2012
DOI: 10.1002/SCA.21002
Abstract: The nanoarchitecture and surface roughness of metallic thin films prepared by magnetron sputtering were analyzed to determine the topographical statistics that give the optimum description of their nanoarchitechture. Nanoscale topographical profiles were generated by performing atomic force microscopy (AFM) scans of 1 μm × 1 μm areas of titanium and silver films of three different thicknesses (3 nm, 12 nm, and 150 nm). Of the titanium films, the 150-nm film had the highest average roughness (R(a) = 2.63 nm), more than four times that of the 3-nm and 12-nm titanium films. When silver films were coated on top of 150-nm titanium films, the average roughness increased further the 3-nm (R(a) = 4.96 nm) and 150-nm (R(a) = 4.65 nm) silver films average roughnesses were approximately twice that of the 150-nm titanium film. For topographical analysis, seven statistical parameters were calculated. These parameters included commonly used roughness measurements, as well as some less commonly used measurements, in order to determine which combination of parameters gave the best overall description of the nanoarchitecture of the films presented. Skewness (R(skw)), surface area increase (R(sa)), and peak counts (R(pc)) provided the best description of horizontal surface dimensions, and in conjunction with vertical descriptors R(a) and R(q) gave the best characterization of surface architecture. The five roughness parameters R(a), R(q), R(skw), R(sa), and R(pc) are proposed as a new standard for describing surface nanoarchitecture.
No related grants have been discovered for Jafar Hasan.