Publications by authors named "Ahtasham Raza"

8 Publications

  • Page 1 of 1

A Dinuclear Ruthenium(II) Complex Excited by Near-Infrared Light through Two-Photon Absorption Induces Phototoxicity Deep within Hypoxic Regions of Melanoma Cancer Spheroids.

J Am Chem Soc 2020 03 25;142(10):4639-4647. Epub 2020 Feb 25.

Materials Science & Engineering, University of Sheffield, Mappin St, Sheffield S1 3JD, U.K.

The dinuclear photo-oxidizing Ru complex [{Ru(TAP)}(tpphz)] (TAP = 1,4,5,8- tetraazaphenanthrene, tpphz = tetrapyrido[3,2-:2',3'-:3″,2''-:2‴,3'''-]phenazine), , is readily taken up by live cells localizing in mitochondria and nuclei. In this study, the two-photon absorption cross section of is quantified and its use as a two-photon absorbing phototherapeutic is reported. It was confirmed that the complex is readily photoexcited using near-infrared, NIR, and light through two-photon absorption, TPA. In 2-D cell cultures, irradiation with NIR light at low power results in precisely focused phototoxicity effects in which human melanoma cells were killed after 5 min of light exposure. Similar experiments were then carried out in human cancer spheroids that provide a realistic tumor model for the development of therapeutics and phototherapeutics. Using the characteristic emission of the complex as a probe, its uptake into 280 μm spheroids was investigated and confirmed that the spheroid takes up the complex. Notably TPA excitation results in more intense luminescence being observed throughout the depth of the spheroids, although emission intensity still drops off toward the necrotic core. As can directly photo-oxidize DNA without the mediation of singlet oxygen or other reactive oxygen species, phototoxicity within the deeper, hypoxic layers of the spheroids was also investigated. To quantify the penetration of these phototoxic effects, was photoexcited through TPA at a power of 60 mW, which was progressively focused in 10 μm steps throughout the entire -axis of individual spheroids. These experiments revealed that, in irradiated spheroids treated with , acute and rapid photoinduced cell death was observed throughout their depth, including the hypoxic region.
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http://dx.doi.org/10.1021/jacs.9b11313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7146853PMC
March 2020

Correction: A dinuclear ruthenium(ii) phototherapeutic that targets duplex and quadruplex DNA.

Chem Sci 2020 Feb 13;11(9):2566. Epub 2020 Feb 13.

Department of Chemistry, University of Sheffield Brook Hill Sheffield S3 7HF UK +44 (0)114 222 9325.

[This corrects the article DOI: 10.1039/C8SC05084H.].
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http://dx.doi.org/10.1039/d0sc90032jDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8157496PMC
February 2020

A dinuclear ruthenium(ii) phototherapeutic that targets duplex and quadruplex DNA.

Chem Sci 2019 Mar 18;10(12):3502-3513. Epub 2019 Feb 18.

Department of Chemistry , University of Sheffield , Brook Hill , Sheffield , S3 7HF , UK . Email: ; Tel: +44 (0)114 222 9325.

With the aim of developing a sensitizer for photodynamic therapy, a previously reported luminescent dinuclear complex that functions as a DNA probe in live cells was modified to produce a new iso-structural derivative containing Ru(TAP) fragments (TAP = 1,4,5,8-tetraazaphenanthrene). The structure of the new complex has been confirmed by a variety of techniques including single crystal X-ray analysis. Unlike its parent, the new complex displays Ru → L-based MLCT emission in both MeCN and water. Results from electrochemical studies and emission quenching experiments involving guanosine monophosphate are consistent with an excited state located on a TAP moiety. This hypothesis is further supported by detailed DFT calculations, which take into account solvent effects on excited state dynamics. Cell-free steady-state and time-resolved optical studies on the interaction of the new complex with duplex and quadruplex DNA show that the complex binds with high affinity to both structures and indicate that its photoexcited state is also quenched by DNA, a process that is accompanied by the generation of the guanine radical cation sites as photo-oxidization products. Like the parent complex, this new compound is taken up by live cells where it primarily localizes within the nucleus and displays low cytotoxicity in the absence of light. However, in complete contrast to [{Ru(phen)}(tpphz)], the new complex is therapeutically activated by light to become highly phototoxic toward malignant human melanoma cell lines showing that it is a promising lead for the treatment of this recalcitrant cancer.
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http://dx.doi.org/10.1039/c8sc05084hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6430095PMC
March 2019

Fabrication, in vitro and in vivo studies of bilayer composite membrane for periodontal guided tissue regeneration.

J Biomater Appl 2019 02 3;33(7):967-978. Epub 2018 Dec 3.

1 Interdisciplinary Research Centre in Biomedical Materials, COMSATS University Islamabad, Lahore Campus, Lahore, Pakistan.

Development of a guided occlusive biodegradable membrane with controlled morphology in order to restrict the ingrowth of epithelial cells is still a challenge in dental tissue engineering. A bilayer membrane with a non-porous upper layer (polyurethane) and porous lower layer (polycaprolactone and bioactive glass composite) with thermoelastic properties to sustain surgery treatment was developed by lyophilization. Morphology, porosity, and layers attachment were controlled by using the multi-solvent system. In vitro and in vivo biocompatibility, cell attachment, and cell proliferation were analyzed by immunohistochemistry and histology. The cell proliferation rate and cell attachment results showed good biocompatibility of both surfaces, though cell metabolic activity was better on the polycaprolactone-bioactive glass surface. Furthermore, the cells were viable, adhered, and proliferated well on the lower porous bioactive surface, while non-porous polyurethane surface demonstrated low cell attachment, which was deliberately designed and a pre-requisite for guided tissue regeneration/guided bone regeneration membranes. In addition, in vivo studies performed in a rat model for six weeks revealed good compatibility of membranes. Histological analysis (staining with hematoxylin and eosin) indicated no signs of inflammation or accumulation of host immune cells. These results suggested that the fabricated biocompatible bilayer membrane has the potential for use in periodontal tissue regeneration.
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http://dx.doi.org/10.1177/0885328218814986DOI Listing
February 2019

A methodology for the production of microfabricated electrospun membranes for the creation of new skin regeneration models.

J Tissue Eng 2018 Jan-Dec;9:2041731418799851. Epub 2018 Sep 21.

Biomaterials and Tissue Engineering Group, Department of Materials Science and Engineering, Kroto Research Institute, The University of Sheffield, Sheffield, UK.

The continual renewal of the epidermis is thought to be related to the presence of populations of epidermal stem cells residing in physically protected microenvironments (rete ridges) directly influenced by the presence of mesenchymal fibroblasts. Current skin in vitro models do acknowledge the influence of stromal fibroblasts in skin reorganisation but the study of the effect of the rete ridge-microenvironment on epidermal renewal still remains a rich topic for exploration. We suggest there is a need for the development of new in vitro models in which to study epithelial stem cell behaviour prior to translating these models into the design of new cell-free biomaterial devices for skin reconstruction. In this study, we aimed to develop new prototype epidermal-like layers containing pseudo-rete ridge structures for studying the effect of topographical cues on epithelial cell behaviour. The models were designed using a range of three-dimensional electrospun microfabricated scaffolds. This was achieved via the utilisation of polyethylene glycol diacrylate to produce a reusable template over which poly(3-hydrroxybutyrate--3-hydroxyvalerate) was electrospun. Initial investigations studied the behaviour of keratinocytes cultured on models using plain scaffolds (without the presence of intricate topography) versus keratinocytes cultured on scaffolds containing microfeatures.
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http://dx.doi.org/10.1177/2041731418799851DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6153546PMC
September 2018

An Improved Methodology to Visualise Tumour Induced Changes in Vasculature Using the Chick Chorionic Allantoic Membrane Assay.

In Vivo 2018 May-Jun;32(3):461-472

Department of Materials Science Engineering, Kroto Research Institute, University of Sheffield, Sheffield, U.K.

Background/aim: Decreasing the vascularity of a tumour has proven to be an effective strategy to suppress tumour growth and metastasis. Anti-angiogenic therapies have revolutionized the treatment of advanced-stage cancers, however there is still demand for further improvement. This necessitates new experimental models that will allow researchers to reliably study aspects of angiogenesis. The aim of this study was to demonstrate an in vivo technique in which the highly vascular and accessible chorioallantoic membrane (CAM) of the chick embryo is used to study tumour-induced changes in the macro and microvessels.

Materials And Methods: Two cancer cell lines (human melanoma (C8161) and human prostate cancer (PC3)) were selected as model cells. Human dermal fibroblasts were used as a control. One million cells were labelled with green fluorescent protein and implanted on the CAM of the chick embryo at embryonic development day (EDD) 7 and angiogenesis was evaluated at EDDs 10, 12 and 14. A fluorescently-tagged lectin (lens culinaris agglutinin (LCA)) was injected intravenously into the chick embryo to label endothelial cells. The LCA is known to label the luminal surface of endothelial cells, or dextrans, in the CAM vasculature. Macrovessels were imaged by a hand-held digital microscope and images were processed for quantification. Microvessels were evaluated by confocal microscopy. Tumour invasion was assessed by histological and optical sectioning.

Results: Tumour cells (C8161 and PC3) produced quantifiable increases in the total area covered by blood vessels, compared to fibroblasts when assessed by digital microscopy. Tumour invasion could be demonstrated by both histological and optical sectioning. The most significant changes in tumour vasculature observed were in the microvascular structures adjacent to the tumour cells, which showed an increase in the endothelial cell coverage. Additionally, tumour intravasation and tumour thrombus formation could be detected in the areas adjacent to tumour cells. The fragility of tumour blood vessels could be demonstrated when tumour cells seeded on a synthetic scaffold were grown on CAM.

Conclusion: We report on a modification to a well-studied CAM in vivo assay, which can be effectively used to study tumour induced changes in macro and microvasculature.
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http://dx.doi.org/10.21873/invivo.11262DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6000782PMC
September 2018

Oxygen Mapping of Melanoma Spheroids using Small Molecule Platinum Probe and Phosphorescence Lifetime Imaging Microscopy.

Sci Rep 2017 09 6;7(1):10743. Epub 2017 Sep 6.

Materials Science & Engineering, University of Sheffield, Sheffield, S3 7HQ, UK.

Solid tumours display varied oxygen levels and this characteristic can be exploited to develop new diagnostic tools to determine and exploit these variations. Oxygen is an efficient quencher of emission of many phosphorescent compounds, thus oxygen concentration could in many cases be derived directly from relative emission intensity and lifetime. In this study, we extend our previous work on phosphorescent, low molecular weight platinum(II) complex as an oxygen sensing probe to study the variation in oxygen concentration in a viable multicellular 3D human tumour model. The data shows one of the first examples of non-invasive, real-time oxygen mapping across a melanoma tumour spheroid using one-photon phosphorescence lifetime imaging microscopy (PLIM) and a small molecule oxygen sensitive probe. These measurements were quantitative and enabled real time oxygen mapping with high spatial resolution. This combination presents as a valuable tool for optical detection of both physiological and pathological oxygen levels in a live tissue mass and we suggest has the potential for broader clinical application.
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http://dx.doi.org/10.1038/s41598-017-11153-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5587740PMC
September 2017

Raman spectroscopy detects melanoma and the tissue surrounding melanoma using tissue-engineered melanoma models.

Appl Spectrosc Rev 2016 Apr 5;51(4):243-257. Epub 2016 Feb 5.

Department of Materials Science & Engineering, University of Sheffield , Sheffield , UK.

Invasion of melanoma cells from the primary tumor involves interaction with adjacent tissues and extracellular matrix. The extent of this interaction is not fully understood. In this study Raman spectroscopy was applied to cryo-sections of established 3D models of melanoma in human skin. Principal component analysis was used to investigate differences between the tumor and normal tissue and between the peri-tumor area and the normal skin. Two human melanoma cells lines A375SM and C8161 were investigated and compared in 3D melanoma models. Changes were found in protein conformations and tryptophan configurations across the entire melanoma samples, in tyrosine orientation and in more fluid lipid packing only in tumor dense areas, and in increased glycogen content in the peri-tumor areas of melanoma. Raman spectroscopy revealed changes around the perimeter of a melanoma tumor as well as detecting differences between the tumor and the normal tissue.
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http://dx.doi.org/10.1080/05704928.2015.1126840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854220PMC
April 2016
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