• Combination of Microstereolithography and Electrospinning to Produce Membranes Equipped with Niches for Corneal Regeneration

      Ortega, Í.; Sefat, Farshid; Deshpande, P.; Paterson, T.; Ramachandran, C.; Ryan, A.J.; MacNeil, S.; Claeyssens, F. (2014)
      We report a technique for the fabrication of micropockets within electrospun membranes in which to study cell behavior. Specifically, we describe a combination of microstereolithography and electrospinning for the production of PLGA (Poly(lactide-co-glycolide)) corneal biomaterial devices equipped with microfeatures.
    • Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

      Heeley, E.L.; Gough, Timothy D.; Hughes, D.J.; Bras, W.; Rieger, J.; Ryan, A.J. (2013-11)
      The in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness (similar to 50 angstrom) and bulk crystallinity (similar to 20%), were low at, for all processing conditions investigated, which is attributed to the significant short-chain branching in the polymer acting as point defects limiting lamellae crystal growth. (C) 2013 Elsevier Ltd. All rights reserved.
    • An “off-the shelf” Synthetic Membrane to Simplify Regeneration of Damaged Corneas

      Sefat, Farshid; Ortega, Í.; McKean, R.; Deshpande, P.; Ramachandran, C.; Hill, C.J.; Tzokov, S.B.; Claeyssens, F.; Sangwan, V.S.; Ryan, A.J.; et al. (2014)
      Our overall aim is to develop a synthetic off-the-shelf alternative to human amniotic membrane which is currently used for delivering cultured limbal stem cells to the cornea in patients who suffer scarring of the cornea because of the loss of limbal stem cells. We have recently reported that both cultured cells and limbal explants grow well on electrospun Poly(D,L-lactide-co-glycolide) (PLGA) (44 kg/mol) with a 50:50 ratio of lactide and glycolide and sterilized with γ-irradiation. Prior to undertaking a clinical study our immediate aim now is to achieve long term storage of the membranes in convenient to use packaging. Membranes were electrospun from Poly(D,L-lactide-co-glycolide) (44 kg/mol) with a 50:50 ratio of lactide and glycolide and sterilized with γ-irradiation and then stored dry (with desiccant) for several months at -80°C and -20°C , Room temperature (UK and India), 37°C and 50°C. We explored the contribution of vacuum sealing and the use of a medical grade bag (PET/Foil/LDPE) to achieve a longer shelf life. Confirmation of membranes being suitable for clinical use was obtained by culturing tissue explants on membranes post storage. When scaffolds were stored dry the rate of breakdown was both temperature and time dependent. At -20°C and -80°C there was no change in fiber diameter over 18 months of storage, and membranes were stable for 12 months at 4°C while at 50°C (above the transition temperature for PLGA) scaffolds lost integrity after several weeks. The use of vacuum packaging and a medical grade bag both improved the storage shelf-life of the scaffolds. The impact of temperature on storage is summarized beneath. We report that this synthetic membrane can be used as an off-the-shelf or-out-of-the freezer alternative to the amniotic membrane for corneal regeneration.
    • Self-motile colloidal particles: from directed propulsion to random walk

      Gough, Timothy D.; Howse, J.R.; Jones, R.A.L.; Ryan, A.J. (2009-07-27)
      The motion of an artificial micro-scale swimmer that uses a chemical reaction catalyzed on its own surface to achieve autonomous propulsion is fully characterized experimentally. It is shown that at short times, it has a substantial component of directed motion, with a velocity that depends on the concentration of fuel molecules. At longer times, the motion reverts to a random walk with a substantially enhanced diffusion coefficient. Our results suggest strategies for designing artificial chemotactic systems.