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Cairns M.-L.,Queens University of Belfast | Sykes A.,Queens University of Belfast | Dickson G.R.,Queens University of Belfast | Orr J.F.,Queens University of Belfast | And 3 more authors.
Acta Biomaterialia | Year: 2011

Predicable and controlled degradation is not only central to the accurate delivery of bioactive agents and drugs, it also plays a vital role in key aspects of bone tissue engineering. The work addressed in this paper investigates the utilisation of e-beam irradiation in order to achieve a controlled (surface) degradation profile. This study focuses on the modification of commercially and clinically relevant materials, namely poly(l-lactic acid) (PLLA), poly(l-lactide-hydroxyapatite) (PLLA-HA), poly(l-lactide-glycolide) co-polymer (PLG) and poly(l-lactide-dl-lactide) co-polymer (PLDL). Samples were subjected to irradiation treatments using a 0.5 MeV electron beam with delivered surface doses of 150 and 500 kGy. In addition, an acrylic attenuation shield was used for selected samples to control the penetration of the e-beam. E-beam irradiation induced chain scission in all polymers, as characterized by reduced molecular weights and glass transition temperatures (Tg). Irradiation not only produced changes in the physical properties of the polymers but also had associated effects on surface erosion of the materials during hydrolytic degradation. Moreover, the extent to which both mechanical and hydrolytic degradation was observed is synonymous with the estimated penetration of the beam (as controlled by the employment of an attenuation shield). © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Khan I.M.,University of Cardiff | Gonzalez L.G.,University of Cardiff | Francis L.,University of Swansea | Conlan R.S.,University of Swansea | And 6 more authors.
European Cells and Materials | Year: 2011

The failure of cartilages to fuse, particularly in the case of articular cartilage under conditions of repair is due to morphological and structural constraints of the tissue. Factors that impede integration include, non-vascularisation, low cellularity, and proteoglycan in the surrounding extracellular matrix acting as a natural barrier to cellular migration. We hypothesised that brief activation of a catabolic cascade by cytokines followed by culture under anabolic conditions would promote tissue fusion in a ring-disk model of cartilage integration. Our results show that transient exposure to 10 ng mL-1 interleukin-1β, followed by two weeks post-culture under anabolic conditions, enhanced cartilage-cartilage integration compared to untreated explants. Quantitative PCR analysis of catabolism-related genes ADAMTS4 and MMP13 showed both were transiently upregulated and these findings correlated with evidence of extracellular matrix remodelling. At the level of histology, we observed chondrocytes readily populated the interfacial matrix between fused explants in interleukin-1β treated explants, whereas in control explants this region was relatively acellular in comparison. Catabolic cytokine treated explants exhibited 29-fold greater adhesive strength (0.859 MPa versus 0.028 MPa, P < 0.05) than untreated counterparts. Collectively, our results demonstrate that a single short catabolic pulse followed by an anabolic response is sufficient to generate mechanically robust, integrative cartilage repair. Source

Cairns M.-L.,Queens University of Belfast | Dickson G.R.,Queens University of Belfast | Orr J.F.,Queens University of Belfast | Farrar D.,Smith and Nephew Group Research Center | And 2 more authors.
Polymer Degradation and Stability | Year: 2011

Bioresorbable polymers such as polylactide (PLA) and polylactide-co- glycolide (PLGA) have been used successfully as biomaterials in a wide range of medical applications. However, their slow degradation rates and propensity to lose strength before mass have caused problems. A central challenge for the development of these materials is the assurance of consistent and predictable in vivo degradation. Previous work has illustrated the potential to influence polymer degradation using electron beam (e-beam) radiation. The work addressed in this paper investigates further the utilisation of e-beam radiation in order to achieve a more surface specific effect. Variation of e-beam energy was studied as a means to control the effective penetrative depth in poly-l-lactide (PLLA). PLLA samples were exposed to e-beam radiation at individual energies of 0.5 MeV, 0.75 MeV and 1.5 MeV. The near-surface region of the PLLA samples was shown to be affected by e-beam irradiation with induced changes in molecular weight, morphology, flexural strength and degradation profile. Moreover, the depth to which the physical properties of the polymer were affected is dependent on the beam energy used. Computer modelling of the transmission of each e-beam energy level used corresponded well with these findings. © 2010 Elsevier Ltd. All rights reserved. Source

Cairns M.-L.,Queens University of Belfast | Dickson G.R.,Queens University of Belfast | Orr J.F.,Queens University of Belfast | Farrar D.,Smith and Nephew Group Research Center | And 5 more authors.
Journal of Biomedical Materials Research - Part A | Year: 2012

Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment. Copyright © 2012 Wiley Periodicals, Inc. Source

Gurkan I.,U.S. National Institute on Aging | Ranganathan A.,U.S. National Institute on Aging | Yang X.,Hospital for Special Surgery | Todman M.,Smith and Nephew Group Research Center | And 3 more authors.
Osteoarthritis and Cartilage | Year: 2010

Objective: The Hartley guinea pig develops articular cartilage degeneration similar to that seen in idiopathic human osteoarthritis (OA). We investigated whether the application of pulsed low-intensity ultrasound (PLIUS) to the Hartley guinea pig joint would prevent or attenuate the progression of this degenerative process. Methods: Treatment of male Hartley guinea pigs was initiated at the onset of degeneration (8 weeks of age) to assess the ability of PLIUS to prevent OA, or at a later age (12 months) to assess the degree to which PLIUS acted to attenuate the progression of established disease. PLIUS (30mW/cm2) was applied to stifle joints for 20min/day over periods ranging from 3 to 10 months, with contralateral limbs serving as controls. Joint cartilage histology was graded according to a modified Mankin scale to evaluate treatment effect. Immunohistochemical staining for interleukin-1 receptor antagonist (IL-1ra), matrix metalloproteinase (MMP)-3, MMP-13, and transforming growth factor (TGF)-β1 was performed on the cartilage to evaluate patterns of expression of these proteins. Results: PLIUS did not fully prevent cartilage degeneration in the prevention groups, but diminished the severity of the disease, with the treated joints showing markedly decreased surface irregularities and a much smaller degree of loss of matrix staining as compared to controls. PLIUS also attenuated disease progression in the groups with established disease, although to a somewhat lesser extent as compared to the prevention groups. Immunohistochemical staining demonstrated a markedly decreased degree of TGF-β1 production in the PLIUS-treated joints. This indicates less active endogenous repair, consistent with the marked reduction in cartilage degradation. Conclusions: PLIUS exhibits the ability to attenuate the progression of cartilage degeneration in an animal model of idiopathic human OA. The effect was greater in the treatment of early, rather than established, degeneration. © 2010. Source

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