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A new method based on scanning atmospheric plasma for an ultrafast reduction of graphene oxide (GO) and preparation of highly conductive graphene films and patterns is presented. This simple method is shown to provide a direct and scalable fabrication of graphene films on flexible and shaped substrates with a variety of patterns for broad applications. An effective and ultrafast (similar to 60 s) reduction of GO films into highly conductive graphene films at room temperature is demonstrated by this process that is impossible to achieve by conventional wet chemical and thermal reduction process. The software controlled x-y scanning unit allows fabrication of graphene films with variety of patterns on different substrates including glass, plastic, ceramics and metals with complex shapes required for flexible and wearable electronics and devices. Characterization results confirmed that a thin transparent graphene film can be produced with a surface sheets resistance of 22 k Omega/sq at the transparency of 88%, and a thick film (similar to 25 mu m) with a sheet resistance of 186 Omega/sq. A practical application of plasma fabricated graphene films was demonstrated for a supercapacitor devices able to deliver an outstanding volumetric capacitance of 536.55 F/cm(3) at a current density of 1 A/g. (C) 2017 Elsevier Ltd. All rights reserved. Refereed/Peer-reviewed

In comparison with inorganic and dry polymeric materials, conductive polymer hydrogels are promising soft electrode materials due to their unique solid-liquid interface. Nevertheless, the existing hydrogels lack either excellent electrochemical performance or mechanical resilience. Here we report a strategy to overcome this limitation by integrating two types of conducting polymers – polyaniline and PEDOT – through a molecular bridge provided by phytic acid. The acid replaces some of PSS, promoting transformation of PEDOT chains from the benzoic structure to the quinoid structure. The resulting hydrogel consists of a 3D network of PEDOT sheets where PANi are inlaid; it has highly improved mechanical properties in comparison with PEDOT hydrogel due to molecular interactions between PANi and PEDOT. A flexible solid-state supercapacitor based on PEDOT/PANi hydrogel delivered a high volumetric energy density of 0.25 mWh cm−3 at a power density of 107.14 mW cm−3, surpassing many of previously reported solid-state supercapacitors based on PEDOT and hydrogels of other conducting polymers and graphene oxide. This study represents a new direction for the development of conductive polymer composite hydrogels which combine excellent electrochemical performance with mechanical resilience Refereed/Peer-reviewed

In this report, we employed surface-initiated atom transfer radical polymerisation to graft thermo-responsive copolymers of oligo(ethylene glycol) methacrylates from the surface of diatom biosilica microcapsules. We demonstrate the application of the resulting composites for thermo-responsive drug delivery Refereed/Peer-reviewed

Since the initial emergence of two-dimensional graphene (Gr) nano-material, there has been a great interest in its potential applications due to its excellent conductivity, enormous surface area and good mechanical strength. Microbial fuel cells (MFCs) are one of these important promising applications. The limited productivity of MFCs compared to other fuel cell technologies along with the high cost of their components are the two major obstacles to commercialization. Gr is proposed to help overcome such challenges by integrating with biocatalysts for the construction of Gr based MFCs, either as an anode to increase the electron transfer efficiency, or as a cathode to effectively catalyze the oxygen reduction reaction (ORR). This integration is relevant only if the favorable environment for bacterial biofilm adherence to Gr modified surfaces is available. Unfortunately, there is insufficient understanding of the interaction mechanism of bacterial cells with such modified surfaces. Despite this challenge, along with the complexity of the Gr modified electrode fabrication, Gr-based electrodes remain a promising option for developing MFCs to achieve sustainable wastewater treatment and bioelectricity generation. As a reflection on these facts, the aim of this review is to provide critical overview and to evaluate the recent advances for the applications of Gr in MFCs, focusing on electrode fabrication and power generation. Within that context, the concerns about microbial compatibility of Gr will be addressed. Refereed/Peer-reviewed

Nanoporous alumina (NPA) arrays prepared by electrochemical anodization have been attractive platform for application in molecular separations, biosensing, drug delivery and fuel cells due to their highly ordered pore structures, controllable pore dimensions and unique physical, optical, transport and electrochemical properties. However, there is still a lack of knowledge about the influence of the pore dimensions, shape and surface area on these properties. Hence the aim of this work is to use a focused ion beam (FIB) to mill a barrier layer of NPA to open a either single nanopore, several nanopores and 1 μm and 20 μm square areas of nanopore arrays to explore their electrochemical properties and biosensing performances. The internal surface of opened NPA nanopores was modified by covalent attachment of streptavidin and used for impedance label-free biosensing. The biosensor performance of this antibody modified nanopore biosensing platform was evaluated using various concentrations of biotin as a model analyte. Electrochemical impedance spectrometric (EIS) measurements of pore resistivity were carried out for different patterns of nanopore arrays. The results showed that small areas or number of pores provide better biosensing performance compared to large nanopore arrays. Refereed/Peer-reviewed

Aim: This study aimed to demonstrate radiofrequency (RF)-triggered release of drugs and drug carriers from drug-eluting implants using gold nanoparticles as energy transducers. Materials & methods: Titanium wire with a titania nanotube layer was used as an implant loaded with indomethacin and micelles (tocopheryl PEG succinate) as a drug and drug carrier model. RF signals were generated from a customized RF generator to trigger in vitro release. Results & discussion: Within 2.5 h, 18 mg (92%) of loaded drug and 14 mg (68%) of loaded drug carriers were released using short RF exposure (5 min), compared with 5 mg (31%) of drug and 2 mg (11%) of drug carriers without a RF trigger. Gold nanoparticles can effectively function as RF energy transducers inside titania nanotubes for rapid release of therapeutics at arbitrary times. Conclusion: The results of this study show that RF is a promising strategy for triggered release from implantable drug delivery systems where on-demand delivery of therapeutics is required. Original submitted 19 November 2012; Revised submitted 1 April 2013

Anodic aluminium oxide (AAO) has been investigated and utilized in numerous products for almost a century. But the rapidly increasing interest in nanoscale materials and their outstanding properties has propelled nanoporous AAO to the fore as one of the most popular nanomaterial with applications across a gamut of areas including molecular separation, catalysis, energy generation and storage, electronics and photonics, sensors and biosensors, drug delivery and template synthesis. Material fabrication of AAO is based on facile and inexpensive electrochemical anodization with the self-ordering process of nanopores not requiring any lithography or templating, and the outcome of the process are perfectly ordered and size controlled nanopores with distinctive pore geometries. Recent research on AAO is characterized by a remarkable trajectory of innovation, in particular with regards to control of surface functionality and, concomitantly, to the design of intricate structural features such as modulated, branched, and multilayered pore architectures. This review illuminates research on recent development of AAO focussing on surface and structural engineering, and on emerging applications. Key examples and critical preparative issues and resulting improvements sparking opportunities for further applications in AAO properties are discussed. We conclude this review with an outlook providing a critical perspective on future trends on surface and structural engineering of AAO. Refereed/Peer-reviewed

The conversion of titania (TiO2) nanotubes into titanium (Ti), while preserving their nanotubular structures, is demonstrated. Their application as bone implants and electrodes for combined local drug delivery and electrical stimulation therapy is proposed. Refereed/Peer-reviewed

Bacterial infection, extensive inflammation and poor osseointegration have been identified as the major reasons for [early] orthopaedic implant failures based on titanium. Creating implants with drug-eluting properties to locally deliver drugs is an appealing way to address some of these problems. To improve properties of titanium for orthopaedic applications, this study explored the modification of titanium surfaces with titaniananotube (TNT) arrays, and approach that combines drug delivery into bone and potentially improved bone integration. A titania layer with an array of nanotube structures (∼120 nm in diameter and 50 μm in length) was synthesized on titanium surfaces by electrochemical anodization and loaded with the water-insoluble anti-inflammatory drug indomethacin. A simple dip-coating process of polymer modification formed thin biocompatible polymer films over the drug-loaded TNTs to create TNTs with predictable drug release characteristics. Two biodegradable and antibacterial polymers, chitosan and poly(lactic-co-glycolic acid), were tested for their ability to extend the drug release time of TNTs and produce favourable bone cell adhesion properties. Dependent on polymer thickness, a significant improvement in the drug release characteristics was demonstrated, with reduced burst release (from 77% to >20%) and extended overall release from 4 days to more than 30 days. Excellent osteoblast adhesion and cell proliferation on polymer-coated TNTs compared with uncoated TNTs were also observed. These results suggest that polymer-modified implants with a TNT layer are capable of delivering a drug to a bone site over an extended period and with predictable kinetics. In addition, favourable bone cell adhesion suggests that such an implant would have good biocompatibility. The described approach is broadly applicable to a wide range of drugs and implants currently used in orthopaedic practice. Refereed/Peer-reviewed

The unique morphologies and properties of the diatom silica shell with its intricate, hierarchically organized three dimensional (3-D) structures with nanoscale dimensions have attracted considerable interest in materials science and nanotechnology in recent years. This review highlights recent emerging applications from diatom nanotechnology research with particular emphasis on applications based on the integration of micro and nanostructures including sensing/biosensing, drug delivery and chemical-free pest control. © 2011 Bentham Science Publishers.

Aim: This study explores the use of natural silica-based porous material from diatoms, known as diatomaceous earth, as a drug carrier of therapeutics for implant- and oral-delivery applications. Materials & Methods: To prove this concept, two drugs models were used and investigated: a hydrophobic (indomethacin) and hydrophilic (gentamicin). Results & Discussion: Results show the effectiveness of diatom microcapsules for drug-delivery application, showing 14–22 wt% drug loading capacity and sustained drug release over 2 weeks. Two steps in the drug release from diatom structures were observed: the first, rapid release (over 6 h is attributed to the surface deposited drug) and the second, slow and sustained release over 2 weeks with zero order kinetics. Conclusion: These results confirm that natural material based on diatom silica can be successfully applied as a drug carrier for both oral and implant drug-delivery applications, offering considerable potential to replace existing synthetic nanomaterials.

In this review article we collect and analyse preparation, chemistry and properties of silica materials relevant for drug delivery applications. We review some of the most relevant milestones in the research of silica materials for implantable, oral, intravenous and dermal drug delivery systems. Preparation, chemistry and drug delivery characteristics of fumed silica nanoparticles (oral and dermal delivery route), silica xerogels (implant delivery), mesoporous silica materials (implant and oral delivery) and mesoporous silica spheres (intravenous delivery) with particular emphasis on their role in anticancer therapy and the design of stimuli responsive drug delivery systems are analysed. Recent progress in the research of silica materials for controlled drug delivery, namely, biocompatibility aspects, research on hybrid materials, anticancer and stimuli-responsive mesoporous silica materials are particularly emphasized. Refereed/Peer-reviewed

Carbon nanotubes are attractive approach for designing of new membranes for advanced molecular separation because of their unique transport properties and ability to mimic biological protein channels. In this work the synthetic approach for fabrication of carbon nanotubes (CNTs) composite membranes is presented. The method is based on growth of multi walled carbon nanotubes (MWCNT) using chemical vapour deposition (CVD) on the template of nanoporous alumina (PA) membranes. The influence of experimental conditions including carbon precursor, temperature, deposition time, and PA template on CNT growth process and quality of fabricated membranes was investigated. The synthesis of CNT/PA composites with controllable nanotube dimensions such as diameters (30-150 nm), and thickness (5-100 μm), was demonstrated. The chemical composition and morphological characteristics of fabricated CNT/PA composite membranes were investigated by various characterisation techniques including scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM) and x-ray diffraction (XRD). Transport properties of prepared membranes were explored by diffusion of dye (Rose Bengal) used as model of hydrophilic transport molecule. Refereed/Peer-reviewed

Transition metal hexacyanoferrate (MeHCF) have attracted extensive attention because of their outstanding properties including, electrocatalysis, molecular magnetism, biosensing and ion-exchange. This paper describes an approach for fabrication of ordered nanoarrays of Ni hexacyanoferrate (NiHCF) structures with different morphologies such as dots, rods and tubes in order to advance their properties and applications. The method is based on the conversion of Ni into NiHCF nanostructures by electrochemical oxidation in the presence of hexacyanoferrate ions, using nanoporous anodic alumina oxide (AAO) as a template. The structure and morphology of formed Ni and NiHCF nanoarrays were confirmed by scanning electron microscopy (SEM), showing agreement with the pore structures of the AAO template. The electrocatalytic activity of NiHCF nanorod array electrodes showed high catalytic properties for the detection of hydrogen peroxide and the potential to be used as a platform for direct biosensing applications. The ion-exchange ability of fabricated NiHCF nanostructures (nanorods and nanotubes) toward alkali cations such as Na + has been successfully confirmed.

The application of nanotechnology to medicine termed as 'nanomedicine' is recognised as an emerging field with enormous potential for developing new therapeutic concepts. A range of nanoscale materials have been explored in the last few years for drug delivery to address the problems associated with conventional drug therapies such as limited drug solubility, poor biodistribution, lack of selectivity and unfavourable pharmacokinetics. Among them, nanoporous materials with ordered and controlled pore structures, high surface area and pore volume, attracted great attention, particularly for implantable drug delivery systems. This review presents the recent progress in this field focused on electrochemically engineered nanopores/nanotube materials such as nanoporous alumina and nanotubular titania. The basic concept of fabrication of these unique materials using a self-ordering process, description of their structural properties, biocompatibility and recent applications for therapeutic implants is presented.

Diatoms occupy sunlit aquatic environments. From a materialsscientist’s point of view, these unicellular algae are microscopicsilica nanofabrication factories that use two overlapping valvessealed together by girdle bands to encase themselves in a silicafrustule. The frustule is created with 3D precision of tens ofnanometers, in a hierarchical manner, and with multifunctionalproperties (Fig. 1).

The fabrication of three-dimensional (3D) architectures withnanoscale dimensions is still an evolving research area ofnanotechnology. Various methodologies including conven-tional and unconventional fabrications, such as photolitho-graphy, scanning beam lithography, molding, embossing, andimprinting, have been developed in the past decade.

The fabrication of microstructured surfaces using biological tem- plates was investigated with the aim of exploring of a facile and low cost approach for the fabrication of structured surfaces with superhydrophobic properties. Two soft lithographic techniques, i.e., replica moulding and nano-imprinting, were used to replicate the surfaces of a biological substrate. Leaves of the Agave plant (Agave attenuate), a cost-free biological template, were used as a model of a biosurface with superhydrophobic properties. The replication process was performed using two polymers: an elastomeric polymer, poly(dimethylsiloxane) (PDMS), and a polyurethane (PU) based, UV-curable polymer (NOA 60). In the first replication step, negative polymer replicas of the surface of leaves were fabricated, which were used as masters to fabricate positive polymer replicas by moulding and soft imprinting. The pattern with micro and nanostructures of the surface of the leaf possesses superhydrophobic properties, which was successfully replicated into both polymers. Finally, the positive replicas were coated with a thin gold film and modified with self-assembled monolayers (SAMs) to verify the importance of the surface chemistry on the hydrophobic properties of the fabricated structures. Wetting (contact angle) and structural (light microscopy and scanning electron microscopy) characterization was performed to confirm the hydrophobic properties of the fabricated surfaces (>150°), as well as the precision and reproducibility of the replication process. Refereed/Peer-reviewed

Here, we report on the development of advanced biopolymer-coated drug-releasing implants based on titanium (Ti) featuring titania nanotubes (TNTs) on its surface. These TNT arrays were fabricated on the Ti surface by electrochemical anodization, followed by the loading and release of a model antibiotic drug, gentamicin. The osteoblastic adhesion and antibacterial properties of these TNT–Ti samples are significantly improved by loading antibacterial payloads inside the nanotubes and modifying their surface with two biopolymer coatings (PLGA and chitosan). The improved osteoblast adhesion and antibacterial properties of these drug-releasing TNT–Ti samples are confirmed by the adhesion and proliferation studies of osteoblasts and model Gram-positive bacteria (Staphylococcus epidermidis). The adhesion of these cells on TNT–Ti samples is monitored by fluorescence and scanning electron microscopies. Results reveal the ability of these biopolymer-coated drug-releasing TNT–Ti substrates to promote osteoblast adhesion and proliferation, while effectively preventing bacterial colonization by impeding their proliferation and biofilm formation. The proposed approach could overcome inherent problems associated with bacterial infections on Ti-based implants, simultaneously enabling the development of orthopedic implants with enhanced and synergistic antibacterial functionalities and bone cell promotion.

A new method mapping the defects in self-assembled monolayers (SAMs) is described. The method is based on electrochemical polymerisation of nonconductive tyramine in defect sites of a monolayer and subsequent visualisation of the polymer structures by atomic force microscopy (AFM). SAMs of hexadecanthiol (HDT) on gold prepared by deposition from solution and microcontact printing were used as a model for this study. The method allows easy mapping of defects on monolayers and provides information about their shape, size, size distribution, defect density and spatial distribution. Comparative electrochemical characterisation of defects in SAMs before and after polymerisation shows that polymer growth occurs on the sites of uncovered gold. The approach should be applicable for the characterisation of defects in other types of ultra-thin organic films on conducting surfaces.

In the quest for solutions to meeting future energy demands, solar fuels play an important role. A particularly promising example is photocatalysis since even incremental improvements in performance in this process are bound to translate into significant cost benefits. Here, we report that semiconducting and high surface area 3D silicon replicas prepared from abundantly available diatom fossils sustain photocurrents and enable solar energy conversion. Refereed/Peer-reviewed

Molecular or ion transport through a single nanopore or nanopore array is a key process in a number of applications including: molecular separation, biosensing, energy storage, nanofluidics and nanoelectronics. In this study, the electrochemical and electrical properties of nanopore arrays were investigated by electrochemical impedance spectroscopy (EIS), to explore their capability towards the development of improved nanopore biosensing devices. Anodic aluminum oxide (AAO) nanopore arrays with square patterns were fabricated by a photolithographic technique for use as a biosensing platform. To demonstrate the potential capability of these nanoporous arrays for biosensing applications, their internal surfaces were functionalized with a self-assembled monolayer of phosphonic acid; followed by covalent bonding with the model binding molecule streptavidin. The sensing performance of the prepared sensing device was characterized by EIS using different concentrations of biotin as probe molecule. The changes in impedance signal in response to the specific binding of biotin molecules to the streptavidin inside nanopores were monitored and explored depending on pore morphology. The results obtained for this system exhibit a high level of sensitivity and selectivity, which could provide the basis for the development of superior biosensing devices. Refereed/Peer-reviewed

The influence of the topography of the underlying gold surface on the integrity of self-assembled monolayers (SAMs) of hexadecanethiol (HDT) prepared by solution assembly and microcontact printing was assessed using six different gold substrates. The bare substrates were evaluated for roughness and defects using scanning tunneling microscopy (STM). The structural integrity of self-assembled monolayers on these substrates has been evaluated using both surface methods (STM) and electrochemical measurements. Perhaps not surprisingly, the flattest substrates seem to produce the highest quality monolayer. It is surprising to note, however, that the layer quality is not necessarily traceable to a variation in coverage. Despite both the solution-formed and printed SAMs appearing similar in STM images, electrochemical assessment of the SAM integrity indicated the printed SAMs were inferior, forming a less effective passivating barrier with many more pinholes. The quality of printed SAMs could be improved consider...

Karan Gulati1,2, Moom Sinn Aw1, Dusan Losic1,21Ian Wark Research Institute, The University of South Australia, Adelaide, SA, Australia; 2School of Chemical Engineering, The University of Adelaide, Adelaide, SA, AustraliaAbstract: The blood–brain barrier (BBB) blocks the passage of active molecules from the blood which makes drug delivery to the brain a challenging problem. Oral drug delivery using chemically modified drugs to enhance their transport properties or remove the blocking of drug transport across the BBB is explored as a common approach to address these problems, but with limited success. Local delivery of drugs directly to the brain interstitium using implants such as polymeric wafers, gels, and catheters has been recognized as a promising alternative particularly for the treatment of brain cancer (glioma) and neurodegenerative disorders. The aim of this study was to introduce a new solution by engineering a drug-releasing implant for local drug delivery in the brain, based on titanium (Ti) wires with titania nanotube (TNT) arrays on their surfaces. Drug loading and drug release characteristics of this system were explored using two drugs commonly used in oral brain therapy: dopamine (DOPA), a neurotransmitter agent; and doxorubicin (DOXO), an anticancer drug. Results showed that TNT/Ti wires could provide a considerable amount of drugs (>170 µg to 1000 µg) with desirable release kinetics and controllable release time (1 to several weeks) and proved their feasibility for use as drug-releasing implants for local drug delivery in the brain.Purpose: In this report, a new drug-releasing platform in the form of nanoengineered Ti wires with TNT arrays is proposed as an alternative for local delivery of chemotherapeutics in the brain to bypass the BBB. To prove this concept, drug loading and release characteristics of two drugs important for brain therapy (the neurotransmitter DOPA and the anticancer drug DOXO) were explored.Methods: Titania nanotube arrays on the surface of Ti wires (TNT/Ti) were fabricated using a simple anodization process, followed by separate loading of two drugs (DOPA and DOXO) inside the nanotube structures. The loading and in vitro release characteristics of prepared TNT/Ti implants were examined using thermogravimetric analysis (TGA) UV-Vis spectroscopy.Results: Scanning electron microscopy studies confirmed that well-ordered, vertically aligned, densely packed nanotube arrays with an average diameter of 170 nm and length 70 µm were formed on the surface of TNT/Ti wires. TGA results showed a total drug loading of 170 µg and 1200 µg inside the TNTs for DOPA and DOXO respectively. Two-phase drug release behavior was observed including a fast release (burst) for the first 6 hours and a prolonged slow release phase for 8 days, both with acceptable dosage and desirable release kinetics. The physical, structural, loading and release characteristics of prepared TNT/Ti implants showed several advantages in comparison with existing and clinically proved brain implants.Conclusion: Our results confirmed that TNT/Ti wires can be successfully employed as a suitable platform to release neurotransmitters such as DOPA and anticancer drugs such as DOXO. Hence, they are a feasible alternative as drug-releasing implants for local drug delivery in the brain to combat neurodegenerative disorders or brain tumors.Keywords: titania nanotubes, brain implants, local drug delivery, dopamine, doxorubicinA Letter to the Editor has been received and published for this article.

A multi-drug delivery system with sequential release based on titania nanotube arrays and polymer micelles as drug carriers is presented. Delivery of multiple water insoluble and soluble drugs required for combined local therapy is demonstrated. Refereed/Peer-reviewed

A study of reflective interference spectroscopy [RIfS] properties of nanoporous anodic aluminium oxide [AAO] with the aim to develop a reliable substrate for label-free optical biosensing is presented. The influence of structural parameters of AAO including pore diameters, inter-pore distance, pore length, and surface modification by deposition of Au, Ag, Cr, Pt, Ni, and TiO2 on the RIfS signal (Fabry-Perot fringe) was explored. AAO with controlled pore dimensions was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid at different voltages (30 to 70 V) and anodization times (10 to 60 min). Results show the strong influence of pore structures and surface modifications on the interference signal and indicate the importance of optimisation of AAO pore structures for RIfS sensing. The pore length/pore diameter aspect ratio of AAO was identified as a suitable parameter to tune interferometric properties of AAO. Finally, the application of AAO with optimised pore structures for sensing of a surface binding reaction of alkanethiols (mercaptoundecanoic acid) on gold surface is demonstrated. Refereed/Peer-reviewed

Stimulus-responsive drug delivery system using titania nanotube arrays loaded with polymer micelles as drug-carriers is presented. Amagnetic stimulated release of drug-carriers was achieved by activating magnetic nanoparticles loaded at the bottom of the nanotubes. Refereed/Peer-reviewed

In this report, a label-free reflectometric interference spectroscopy (RIfS) based microchip biosensor for the detection of circulating tumour cells (CTCs) is demonstrated. Highly ordered nanoporous anodic aluminium oxide (AAO) fabricated by electrochemical anodization of aluminium foil was used as the RIfS sensing platform. Biotinylated anti-EpCAM antibody that specifically binds to human cancer cells of epithelial origin such as pancreatic cancer cells (PANC-1) was covalently attached to the AAO surface through multiple surface functionalization steps. Whole blood or phosphate buffer saline spiked with low numbers of pancreatic cancer cells were successfully detected by specially designed microfluidic device incorporating an AAO RIfS sensor, without labour intensive fluorescence labelling and/or pre-enhancement process. Our results show that the developed device is capable of selectively detecting of cancer cells, within a concentrations range of 1000–100,000 cells/mL, with a detection limit of fewer than 1000 cells/mL, a response time of fewer than 5 min and sample volume of 50 μL of. The presented RIfS method shows considerable promise for translation to a rapid and cost-effective point-of-care diagnostic device for the detection of CTCs in patients with metastatic cancer. Refereed/Peer-reviewed

This work presents the use of nanoporous anodic aluminium oxide [AAO] for reflective interferometric sensing of volatile sulphur compounds and hydrogen sulphide [H2S] gas. Detection is based on changes of the interference signal from AAO porous layer as a result of specific adsorption of gas molecules with sulphur functional groups on a gold-coated surface. A nanoporous AAO sensing platform with optimised pore diameters (30 nm) and length (4 µm) was fabricated using a two-step anodization process in 0.3 M oxalic, followed by coating with a thin gold film (8 nm). The AAO is assembled in a specially designed microfluidic chip supported with a miniature fibre optic system that is able to measure changes of reflective interference signal (Fabry-Perrot fringes). When the sensor is exposed to a small concentration of H2S gas, the interference signal showed a concentration-dependent wavelength shifting of the Fabry-Perot interference fringe spectrum, as a result of the adsorption of H2S molecules on the Au surface and changes in the refractive index of the AAO. A practical biomedical application of reflectometric interference spectroscopy [RIfS] Au-AAO sensor for malodour measurement was successfully shown. The RIfS method based on a nanoporous AAO platform is simple, easy to miniaturise, inexpensive and has great potential for development of gas sensing devices for a range of medical and environmental applications.

The concept of a microfluidic biosensing device based on reflective interferometric spectroscopy (RIfS) is presented in this article. The key element of the sensor is a highly ordered nanoporous structure of anodic aluminium oxide (AAO) integrated into a microfluidic chip combined with an optical fiber spectrophotometer. AAO was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid. The structural and geometrical features of the AAO porous structures were controlled to provide optimal RIfS sensing characteristics and there sensing capabilities were explored using two different strategies; i) detection based on the response generated by pefusion of analyte ions inside the pores and ii) detection based on specific adsorption of analyte molecules on surface of AAO pores. The second strategy is based on chemical modification of the AAO surface to target molecules based on specific surface binding reactions. In this work two cases are presented, including the binding of small thiol molecules on gold-modified AAO (Au-AAO) and binding of larger targets such as circulating tumour cells (CTC) on antibody-modified AAO. Our preliminary results show an excellent capability of our system in the detection of different analytes using both strategies, and confirm good potential for the development and application of interferometric label-free biosensing devices in a wide range of biomedical applications. Refereed/Peer-reviewed

In the past two decades, nanoscale advanced materials have been explored for biosensing molecules, so new horizons have opened up for identifying and quantifying biomolecules, and possible early diagnosis of diseases. DNA nanobiosensors show promise. This article provides an overview on their optical and electrochemical aspects. We discuss recent progress in this field, describing basic concepts of molecular beacons and quantum dots as optical nano-imaging systems. Also, carbon nanotubes provide a platform for development and advancement of electrochemical DNA nanobiosensors, which are increasingly being implemented as robust tools for detection in biomedical sciences. Refereed/Peer-reviewed

The design of a microfluidic nanoporous reflective interferometric (RIfS) sensor is presented. The key element of the sensor is a highly ordered nanoporous structure of anodic aluminium oxide (AAO) integrated into a microfluidic chip and combined with an optical fibre spectrophotometer and notebook computer. AAO with controlled pore dimensions was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid at 50V for 40 minutes. The performance of the microfluidic RIfS for sensing of surface binding reaction of alkanethiols (mercapto undecanoic acid) on gold is evaluated showing excellent sensitivity. The results show potential for development and application of interferometric label-free biosensing elements for a wide range of biomedical applications. Keywords: Reflective interferometric spectroscopy, Fabry-Perot fringes, microchip interference sensor, nanoporous alumina. Refereed/Peer-reviewed

Electroless deposition was used to coat porous alumina membranes with gold. This process reduced the pore diameters and provided a platform suitable for surface modifications with self assembled monolayers (SAMs). The surface enhanced Raman scattering (SERS) effect was employed in order to confirm and characterise the formation of SAMs of 3-mercaptobenzoic acid (mMBA) inside the pores of gold nanotube membranes prepared using porous alumina (PA) templates. The investigation of the coverage and reproducibility of SAMs within porous matrices is of utmost importance in the design of filtration membranes and sensing platforms. Raman spectroscopy is capable of spatially resolved techniques such as mapping which was used to characterise the distribution of mMBA assembly within the pores. Due to the highly ordered structure of porous alumina and well controlled electroless gold deposition, these gold coated membranes have the potential to develop into SERS active substrates for ultrasensitive sensing technologies. Refereed/Peer-reviewed

This Letter reports the use of nanoporous anodic aluminium oxide (AAO) for reflective interferometric gas sensing. Gas detection is based on changes of the interference signal from AAO porous layer as a result of the specific adsorption of gas molecules on a metal coated surface. Two different metal coatings – gold (Au) and platinum (Pt) – were used and their application for the detection of hydrogen sulphide (H2S) and hydrogen (H2) is shown. The practical application of a microchip Au-AAO sensor for measurement of H2S concentration and monitoring of malodour is also presented. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, we present recent work from our group focussed on the fabrication of nanopore and nanotube arrays using self-ordered electrochemistry, and their application in several key areas including template synthesis, molecular separation, optical sensing, and drug delivery. We have fabricated nanoporous anodic aluminium oxide (AAO) with controlled pore dimensions (20-200 nm) and shapes, and used them as templates for the preparation of gold nanorod/nanotube arrays and gold nanotube membranes with characteristic properties such as surface enhanced Raman scattering and selective molecular transport. The application of AAO nanopores as a sensing platform for reflective interferometric detection is demonstrated. Finally, a drug release study on fabricated titania nanotubes confirms their potential for implantable drug delivery applications. Refereed/Peer-reviewed

We report the fabrication of highly ordered TiO 2 nanotube arrays employing electrochemical anodization of titanium using an organic electrolyte comprised of water, NH 4 F , and ethylene glycol. To achieve the self-ordering regime of TiO 2 nanotube growth and reliable fabrication optimal potential window between 80 and 100 V was determined. We show that anodization voltage can be used not only to control nanotube diameters (70–180 nm) but also to have impact on nanotube growth rate. The anodization voltage and anodization time were used to adjust the length of TiO 2 nanotube (thickness of nanotube layer). TiO 2 nanotube array films and self-supporting layers with thickness from < 5 μm to > 250 μm were routinely fabricated.

The attractiveness of sell-ordered electrochemical synthesis of nanopore and nanotube arrays is based on its' simplicity, low cost and nanoscale precision to create highly-organized and uniform structures with controllable dimensions and unique properties. In this work the fabrication of titania nanotubes (TNT) array and their application as implantable drug delivery platform is explored. Prepared TNT were loaded with anti-inflammatory drug (indomethacin). Sustained drug release including triggered release by external magnetic field from TNT implant was monitored by UV-VIS and reflective interference spectroscopy. Refereed/Peer-reviewed

New nanomaterials have been extensively explored in recent years for drug delivery applications to address problems associated with the conventional drug therapies such as limited drug solubility, poor biodistribution, lack of selectivity and unfavourable pharmacokinetics. Among them, carbon nanotubes (CNTs) have attracted great attention due to their unique physicochemical architecture and properties. This comprehensive review summarizes the recent advances regarding the use of CNTs for drug delivery. This review includes general information about CNT structures and properties, methods for their dispersion in aqueous solution and basic concepts for CNTs functionalization relevant for their applications in biological systems and delivery of therapeutics. Some toxicological and biocompatibility issues related to the use of CNTs as pharmaceutical excipients are discussed. Last, recent progress on development of CNT drug delivery systems with a specific emphasis on gene delivery was reviewed. Refereed/Peer-reviewed