14 results for Alkaisi, M.M.

  • Microfluidic Devices for Cellular Bioimprint

    Nock, V.; Murray, L.; Samsuri, F.; Alkaisi, M.M.; Evans, J.J. (2011)

    Conference Contributions - Other
    University of Canterbury Library

    We will discuss the advantages of using microfluidics for Bioimprint in general and of the two different platforms in particular. Both platforms allow for controls and experimental cultures to be carried out simultaneously. Similarly, time lapse samples can be taken from the same array minimizing variables between cell culture sets and thus enabling cell developmental studies.

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  • Control and measurement of hypoxia in microfluidic cancer assays

    Nock, V.; Murray, L.; Alkaisi, M.M.; Evans, J.J. (2011)

    Conference Contributions - Other
    University of Canterbury Library

    In this paper we will demonstrate spatially-resolved visualization of oxygen dissolved in a liquid medium and introduce two microfluidic devices for cell-culture experiments with integrated oxygen control. We will further show how these devices can be used to retain clusters or even individual cells within larger populations under hypoxic conditions, a capability which will allow the evaluation of cancer drugs on a cell-to-cell basis. In general, the combination of the oxygen sensor system with microfluidic culture devices has the potential to significantly improve the relevance of current cancer drug assays.

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  • On-chip analysis of C. elegans muscular forces and locomotion patterns in microstructured environments

    Johari, S.; Nock, V.; Alkaisi, M.M.; Wang, W. (2013)

    Journal Articles
    University of Canterbury Library

    The understanding of force interplays between an organism and its environment is imperative in biological processes. Noticeably scarce from the study of C. elegans locomotion is the measurement of the nematode locomotion forces together with other important locomotive metrics. To bridge the current gap, we present the investigation of C. elegans muscular forces and locomotion metrics (speed, amplitude and wavelength) in one single assay. This assay uses polydimethylsiloxane (PDMS) micropillars as force sensing elements and, by variation of the pillar arrangement, introduces microstructure. To show the usefulness of the assay, twelve wild-type C. elegans sample worms were tested to obtain a total of 4665 data points. The experimental results lead to several key findings. These include: (1) maximum force is exerted when the pillar is in contact with the middle part of the worm body, (2) C. elegans locomotion forces are highly dependent on the structure of the surrounding environment, (3) the worms’ undulation frequency and locomotion speed increases steadily from the narrow spacing of ‘honeycomb’ design to the wider spacing of ‘lattice’ pillar arrangement, and (4) C. elegans maintained their natural sinusoidal movement in the microstructured device, despite the existence of PDMS micropillars. The assay presented here focuses on wild type C. elegans, but the method can be easily applied to its mutants and other organisms. In addition, we also show that, by inverting the measurement device, worm locomotion behaviour can be studied in various substrate environments normally unconducive to flexible pillar fabrication. The quantitative measurements demonstrated in this work further improve the understanding of C. elegans mechanosensation and locomotion.

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  • Worm on the Run – A versatile force-sensing platform for the study of freely moving nematodes

    Nock, V.; Alkaisi, M.M.; Wang, W.; Johari, S. (2015)

    Conference Contributions - Other
    University of Canterbury Library

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  • Suspended Cell Patterning for Automatic Microrobotic Cell Injection

    Wang, W.H.; Alkaisi, M.M.; Liu, X.Y.; Sun, Y.; Chase, J.G.; Chen, X.Q.; Hann, C.E. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    Microinjection of DNA/mRNA/morpholinos is a critical technology for molecular biology and drug discovery. When dealing with suspended cells, state-of-the-art manual injection involves a time-consuming and tedious sample preparation procedure, to accurately align cells. To enable automatic microrobotic cell injection, this paper reports on two inexpensive, reusable, biocompatible, and easy-to-make devices that are capable of patterning a large number of cells in 10-30 seconds. One device is based on negative air pressure and made of polycarbonate using a conventional micro-machining process. It is particularly suitable for cells larger than 100¿m, such as the zebrafish embryo patterning and successful gene 'knock-down' products of the morpholino-injected embryos. The other device is based on dielectrophoresis and suitable for cells smaller than 100¿m, demonstrated by successful trapping of pituitary cells. These devices offer a complete solution for suspended cells in all size spectrums to be prepared up to 10 times faster than manual human preparation. Furthermore, this approach can facilitate high-throughput automatic microrobotic cell injection, for injection applications such as the injection of zebrafish embryos, mouse oocytes/embryos, Drosophila embryos, and other types of suspended cells.

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  • Teaching integrated circuit and semiconductor device design in New Zealand: the University of Canterbury approach

    Blaikie, R.J.; Alkaisi, M.M.; Durbin, S.M.; Cumming, D.R.S. (2002)

    Conference Contributions - Published
    University of Canterbury Library

    Teaching the practical aspects of device and chip design in New Zealand presents many problems, including high manufacturing costs, long lead times, and the lack of local industry strength. Nonetheless, it is possible to overcome these issues. This paper describes the courses in these areas at the University of Canterbury, including a practical IC design project that has been running successfully for the past four years. The IC design project takes final year students through a full custom design using modern design tools and fabrication processes. The design is quite straightforward — a 4-bit arithmetic logic unit — but it emphasises the importance of design, simulation and testing. The final circuits contain a few hundred transistors, so good practice is essential. Twelve designs are integrated on to a single chip to keep costs down, and individual designs are addressed via multiplexers. The designs are fabricated using a 0.5 micron process, accessed through a multi-project vendor (MOSIS). Getting chips back from a manufacturer is significantly more motivating for the students than just performing a paper design.

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  • Surface texturing for silcon solar cells using reactive ion etching technique

    Kumaravelu, G.; Alkaisi, M.M.; Bittar, A. (2002)

    Conference Contributions - Published
    University of Canterbury Library

    Surface texturing is an effective and more lasting technique in reducing reflections and improving light trapping compared to antireflection coatings. A surface texturing technique using Reactive Ion Etching (RIE) method suitable for crystalline and multi crystalline solar cells, which resulted in surfaces with negligible reflection in the visible band is described. Different texturing structures (pillars, holes and black silicon) have been studied and compared in the wavelength range from 250nm-2500nm. It is found that the reflectance of the textured column structures were less than 0.4% at wavelengths from 500nm to 1000nm and showed a minimum of 0.29% at 1000 nm while the reflectivity from black silicon is around 1% and hole structures is around 6.8% in the same wavelength range.

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  • The Fabrication of Metallic Nanotransistors

    Cheng, H.H.; Siaw, J.K.; Alkaisi, M.M. (2005)

    Conference Contributions - Published
    University of Canterbury Library

    IEEE Press

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  • Bioimprinted polymer platforms for cell culture using soft lithography

    Murray, L.M.; Nock, V.; Evans, J.J.; Alkaisi, M.M. (2014)

    Journal Articles
    University of Canterbury Library

    It is becoming recognised that traditional methods of culture in vitro on flat substrates do not replicate physiological conditions well, and a number of studies have indicated that the physical environment is crucial to the directed functioning of cells in vivo. In this paper we report the development of a platform with cell-like features that is suitable for in vitro investigation of cell activity. Biological cells were imprinted in hard methacrylate copolymer using soft lithography. The cell structures were replicated at high nanometre scale resolution, as confirmed by atomic force microscopy. Optimisation of the methacrylate-based copolymer mixture for transparency and biocompatibility was performed, and cytotoxicity and chemical stability of the cured polymer in cell culture conditions were evaluated. Cells of an endometrial adenocarcinoma cell line (Ishikawa) were cultured on bioimprinted substrates. The cells exhibited differential attachment on the bioimprint substrate surface compared to those on areas of flat surface and preferentially followed the pattern of the original cell footprint. The results revealed for the first time that the cancer cells distinguished between behavioural cues from surfaces that had features reminiscent of themselves and that of flat areas. Therefore the imprinted platform will lend itself to detailed studies of relevant physical substrate environments on cell behaviour. The material is not degraded and its permanency allows reuse of the same substrate in multiple experimental runs. It is simple and does not require expensive or specialised equipment. In this work cancer cells were studied, and the growth behaviour of the tumour-derived cells was modified by alterations of the cells’ physical environment. Implications are also clear for studies in other crucial areas of health, such as wound healing and artificial tissues.

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  • The characteristics of Ishikawa endometrial cancer cells are modified by substrate topography with cell-like features and the polymer surface

    Tan, L.H.; Sykes, P.H.; Alkaisi, M.M.; Evans, J.J. (2015)

    Journal Articles
    University of Canterbury Library

    Conventional in vitro culture studies on flat surfaces do not reproduce tissue environments, which have inherent topographical mechanical signals. To understand the impact of these mechanical signals better, we use a cell imprinting technique to replicate cell features onto hard polymer culture surfaces as an alternative platform for investigating biomechanical effects on cells; the high-resolution replication of cells offers the micro- and nanotopography experienced in typical cell–cell interactions. We call this platform a Bioimprint. Cells of an endometrial adenocarcinoma cell line, Ishikawa, were cultured on a bioimprinted substrate, in which Ishikawa cells were replicated on polymethacrylate (pMA) and polystyrene (pST), and compared to cells cultured on flat surfaces. Characteristics of cells, incorporating morphology and cell responses, including expression of adhesion-associated molecules and cell proliferation, were studied. In this project, we fabricated two different topographies for the cells to grow on: a negative imprint that creates cell-shaped hollows and a positive imprint that recreates the raised surface topography of a cell layer. We used two different substrate materials, pMA and pST. We observed that cells on imprinted substrates of both polymers, compared to cells on flat surfaces, exhibited higher expression of β1-integrin, focal adhesion kinase, and cytokeratin-18. Compared to cells on flat surfaces, cells were larger on imprinted pMA and more in number, whereas on pST-imprinted surfaces, cells were smaller and fewer than those on a flat pST surface. This method, which provided substrates in vitro with cell-like features, enabled the study of effects of topographies that are similar to those experienced by cells in vivo. The observations establish that such a physical environment has an effect on cancer cell behavior independent of the characteristics of the substrate. The results support the concept that the physical topography of a cell’s environment may modulate crucial oncological signaling pathways; this suggests the possibility of cancer therapies that target pathways associated with the response to mechanical stimuli.

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  • Micro- and Nanopatterning of Freestanding Protein Films

    Hashemi, A.; Tay, D.; Mutreja, I.; Ali, M.A.; Alkaisi, M.M.; Nock, V. (2015)

    Conference Contributions - Other
    University of Canterbury Library

    Biodegradable casein films have significant potential for use as non-supported stand-alone sheeting in orthopaedic implants and tissue engineering substrates. Multi-scale surface patterns can be used to modulate and guide cell interaction by means of an engineered construct. The majority of work on cell-pattern interaction has so far focused on non-degradable materials. In this paper we demonstrate for the first time the fabrication of micro- and nano-scale geometric patterns on the surface of a crosslinked biodegradable casein film. To achieve this we introduce a two-step fabrication procedure based on polydimethylsiloxane (PDMS) soft-lithography. We will show the reproduction of micro- and nano-scale patterns in liquid-cast casein films. We also demonstrate film formation and cross-linking using glutaraldehyde and discuss the use of these films as cell-culture substrates.

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  • Fabrication of free-standing casein Devices with micro- and nanostructured regular and bioimprinted surface features

    Hashemi, A.; Mutreja, I.; Alkaisi, M.M.; Nock, V.; Ali, M.A. (2015)

    Journal Articles
    University of Canterbury Library

    This work introduces a novel process for the fabrication of free-standing biodegradable casein devices with micro- and nanoscale regular and biomimetic surface features. Fabrication of intermediate polydimethylsiloxane (PDMS) moulds from photoresist masters and liquid-casting of casein is used to transfer arbitrary geometrical shapes onto the surface of casein devices. Casein film composition was optimized for mechanical stability and pattern resolution. It was found that 15% casein in 0.2% NaOH solution, mixed with 10% glycerol, and cross-linked by addition of 2% glutaraldehyde produced the best pattern transfer results. Biomimetic cell-like shapes were transferred onto casein by use of bioimprinting of two-dimensional cell-cultures into PDMS. To demonstrate this process, C2C12 mouse myoblasts were cultured on microscope slides, replicated into PDMS and casein using liquid casting and drying. Recessed alignment grids were integrated into the microscope glass slides to facilitate direct comparison of original cells and their bioimprints on PDMS and casein. Optical microscopy and atomic force microscopy confirmed the transfer of micron-scale morphological features, such as cell outlines, nuclei and larger lamellipodia, into the casein surface. Nanoscale feature resolution in casein was found to be limited compared to the PDMS intermediate moulds, which was attributed to limited wetting of the aqueous casein solution. Strategies to increase resolution of the casein transfer step, as well as degradation behavior of the fabricated devices in cell culture media are currently underway. Substrates fabricated with this process have applications in stem cell engineering, regenerative medicine, and implantable devices

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  • Bioimprinted polymer platforms for cell culture using soft lithography

    Murray, L.M.; Nock, V.; Evans, J.J.; Alkaisi, M.M. (2014)

    Journal Articles
    University of Canterbury Library

    Background: It is becoming recognised that traditional methods of culture in vitro on flat substrates do not replicate physiological conditions well, and a number of studies have indicated that the physical environment is crucial to the directed functioning of cells in vivo. In this paper we report the development of a platform with cell-like features that is suitable for in vitro investigation of cell activity. Biological cells were imprinted in hard methacrylate copolymer using soft lithography. The cell structures were replicated at high nanometre scale resolution, as confirmed by atomic force microscopy. Optimisation of the methacrylate-based co-polymer mixture for transparency and biocompatibility was performed, and cytotoxicity and chemical stability of the cured polymer in cell culture conditions were evaluated. Cells of an endometrial adenocarcinoma cell line (Ishikawa) were cultured on bioimprinted substrates. Results: The cells exhibited differential attachment on the bioimprint substrate surface compared to those on areas of flat surface and preferentially followed the pattern of the original cell footprint. Conclusions: The results revealed for the first time that the cancer cells distinguished between behavioural cues from surfaces that had features reminiscent of themselves and that of flat areas. Therefore the imprinted platform will lend itself to detailed studies of relevant physical substrate environments on cell behaviour. The material is not degraded and its permanency allows reuse of the same substrate in multiple experimental runs. It is simple and does not require expensive or specialised equipment. In this work cancer cells were studied, and the growth behaviour of the tumour-derived cells was modified by alterations of the cells’ physical environment. Implications are also clear for studies in other crucial areas of health, such as wound healing and artificial tissues.

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  • Cellular transfer and AFM imaging of cancer cells using Bioimprint

    Muys, J.J.; Alkaisi, M.M.; Melville, D.O.S.; Nagase, J.; Sykes, P.; Parquez, G.M.; Evans, J.J. (2006)

    Journal Articles
    University of Canterbury Library

    A technique for permanently capturing a replica impression of biological cells has been developed to facilitate analysis using nanometer resolution imaging tools, namely the atomic force microscope (AFM). The method, termed Bioimprint™, creates a permanent cell 'footprint' in a nonbiohazardous Poly (dimethylsiloxane) (PDMS) polymer composite. The transfer of nanometer scale biological information is presented as an alternative imaging technique at a resolution beyond that of optical microscopy. By transferring cell topology into a rigid medium more suited for AFM imaging, many of the limitations associated with scanning of biological specimens can be overcome. Potential for this technique is demonstrated by analyzing Bioimprint™ replicas created from human endometrial cancer cells. The high resolution transfer of this process is further detailed by imaging membrane morphological structures consistent with exocytosis. The integration of soft lithography to replicate biological materials presents an enhanced method for the study of biological systems at the nanoscale.

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