Biophysical and biological characterisation of collagen/resilin-like protein composite fibres.

Collagen type I, in various physical forms, is widely used in tissue engineering and regenerative medicine. To control the mechanical properties and biodegradability of collagen-based devices, exogenous cross-links are introduced into the 3D supramolecular structure. However, potent cross-linking methods are associated with cytotoxicity, whilst mild cross-linking methods are associated with suboptimal mechanical resilience. Herein, we assessed the influence of resilin, a super-elastic and highly stretchable protein found within structures in arthropods where energy storage and long-range elasticity are needed, on the biophysical and biological properties of mildly cross-linked extruded collagen fibres. The addition of resilin-like protein in the 4-arm poly(ethylene glycol) ether tetrasuccinimidyl glutarate cross-linked collagen fibres resulted in a significant increase of stress and strain at break values and a significant decrease of modulus values. The addition of resilin-like protein did not compromise cell metabolic activity and DNA concentration. All groups are supported parallel to the longitudinal fibre axis cell orientation. Herein we provide evidence that the addition of resilin-like protein in mildly cross-linked collagen fibres improves their biomechanical properties, without jeopardising their biological properties.

Matched optical quality comparison of 3-year results of PRK-MMC and phakic IOL implantation in the correction of high myopia.

AIMS: To compare 3-year results of PRK-MMC and phakic intraocular lens (PIOL) implantation in patients with >8.0 diopters (D) of myopia. METHODS: This study was conducted as a non-randomized clinical trial on 23 eyes treated with PIOL (Artiflex; group A) and 23 eyes treated with PRK-MMC (group B). This report compares 3-year treatment results in these two groups. RESULTS: At 3 years after surgery, uncorrected visual acuity was 0.02±0.06 LogMAR in group A and 0.04±0.07 LogMAR in group B (P=0.639). Mean best corrected visual acuity in group A (0.004±0.02) was better than group B (0.03±0.07 LogMAR) (P=0.035). Mean manifest refraction spherical equivalent was -0.16±0.21 and -0.09±0.20D (P=0.190), respectively. Mesopic contrast sensitivity (CS) in the spatial frequency of three cycle/degree (CS3) significantly decreased in both groups, but the reduction was significantly higher in group B (P=0.024). CS6 decreased significantly only in group B (P=0.019). Changes in CS12 and CS18 showed no significant inter-group difference. In group A, the increase in C6 trefoil (0.16±0.18 µm, P=0.003) and reduction in spherical aberration (SA; 0.16±0.08 µm, P<0.001) were statistically significant. In group B, the reduction in vertical coma (P=0.052), and increases in horizontal coma (P=0.044), coma (P<0.001), SA (P<0.001), and total higher order aberrations (P<0.001) were significant after surgery. CONCLUSION: Based on 3-year results, PIOL implantation is a better choice than PRK-MMC for treating patients with >8.0D myopia. However, for patients with an inadequate aqueous depth, PRK-MMC can be an acceptable treatment option with a potential for decreased quality of vision.

Investigation of the composition of arterial plaques based on arterial waveforms and material properties.

Stroke is mainly caused by a narrowing of the carotid artery from a build-up of plaque. The risk of plaque rupture and subsequent stroke is dependent on plaque composition. Advances in imaging modalities offer a non-invasive means to assess the health of blood vessels and detect damage. However, the current diagnosis fails to identify patients with soft lipid plaque that are more susceptible to fissure, resulting in stroke. The aim of this study was to use waveform analysis to identify plaque composition and the risk of rupture. We have investigated pressure and flow by combining an artificial blood flow circuit with tubing containing different materials, to simulate plaques in a blood vessel. We used fat and bone to model lipid and calcification respectively to determine if the composition of plaques can be identified by arterial waveforms. We demonstrate that the arterial plaque models with different percentages of calcification and fat, results in significantly different arterial waveforms. These findings imply that arterial waveform analysis has the potential for further development to identify the vulnerable plaques prone to rupture. These findings could have implications for improved patient prognosis by speed of detection and a more appropriate treatment strategy.

Comparison of the visual outcomes between PRK-MMC and phakic IOL implantation in high myopic patients.

PURPOSE: To compare the visual outcomes between PRK-MMC and phakic IOL in patients with more than 8 diopter (D) of myopia. METHODS: This comparative study was performed on 23 eyes under treatment with Artiflex (group A) and 23 eyes under treatment with PRK-MMC (group B). Artiflex phakic IOL (Ophtec BV) was used in group A, and the VISX STAR S4 Excimer Laser (Abbott) was used for PRK-MMC in group B. RESULTS: The safety index was 1.11 ± 0.23 and 1.05 ± 0.25 (P = 0.100) and the efficacy index was 1.02 ± 0.11 and 0.98 ± 0.10 (P = 0.266) in group A and B, respectively. At 1 year after surgery, the manifest refraction spherical equivalent was -0.17 ± 1.18 and -0.25 ± 0.18 D in group A and B, respectively (P = 0.471). Mesopic CS showed no significant difference between the two groups in any spatial frequency. Total coma was 0.24 ± 0.17 and 0.67 ± 0.40 µm (P < 0.001), spherical aberration was -0.11 ± 0.11 and 0.41 ± 0.18 µm (P < 0.001), and RMS HOAT was 0.50 ± 0.20 and 0.96 ± 0.45 µm (P<0.001) in group A and B, respectively. CONCLUSION: Phakic IOL implantation was better than PRK-MMC in the correction of high myopia in terms of visual quality, but the two methods had no difference with regard to visual acuity. Therefore, PRK-MMC can be used when the anterior chamber depth is a limiting factor in the implantation of phakic IOLs.

Novel materials for moist wound management: alginate-psyllium hybrid fibres.

OBJECTIVE: To assess the feasibility of producing high absorbing, high gelling hybrid fibres made from alginate and psyllium. METHOD: Three methods of psyllium extraction were attempted: the hot, cold and hydrolysed method. The extracted psyllium was sieved before addition to the alginate dope. To assess feasibility, each dope was in turn extruded on a bench-top extruder and then on a pilot-size wet extruder. Calcium chloride solution was used as the coagulation medium for all the extrusions. The produced fibres were subsequently assessed for their linear density, tensile strength, absorption characteristics and swelling behaviour. Optical microscopy was also used to illustrate hybrid fibre swelling behaviour under different conditions RESULTS: This feasibility study has shown that hybrid fibres can be produced when using different methods of psyllium extraction, proving the feasibility of the proposed methodology. However, based on physical and functional assessment of the fibres, it was found that the cold water extraction method leads to better hybrid fibres with superior tensile properties, liquid absorption and swelling, which would render them most suitable for heavily exudating wounds. CONCLUSION: The cold water route is found to be the most effective way of producing polysaccharide-based hybrid fibres. This method is also the least expensive, both in terms of room temperature preparations and functional effectiveness, using only 0.75% psyllium. This fibre is therefore recommended for wound dressing applications. DECLARATION OF INTEREST: There were no external sources of funding for this study. The authors have no conflicts of interest to declare.

Absorbent alginate fibres modified with hydrolysed chitosan for wound care dressings--II. Pilot scale development.

Fibres have been used extensively in wound dressing applications as they provide a high surface area for absorption, ease of fabrication and softness. It is common practice for commercial wound dressings to be produced from natural materials, such a marine polysaccharides, as they are predominantly biocompatible, non-toxic, and often display bioactive properties, such as inherent antimicrobial activity. In this study hydrolysed chitosans were utilised as a sole coagulant for the production of alginate-chitosan fibres via a one-step, direct wet-spinning extrusion process. The levels of chitosan incorporated into the fibres were analysed quantitatively via elemental analysis and qualitatively by staining using Amido Black 10B. It was estimated that the fibres contained between 4.50 and 5.10% (wt.%) chitosan. The presence of chitosan improved tensile properties such as elongation and tenacity of the base alginate fibres. The increased incorporation of chitosan into the fibres also improved the absorption of the fibres in both saline and distilled water; reaching maximum of >30 g/g and >50 g/g, respectively. This work suggests that the observed hydrolysed chitosan content within the fibre may be optimal for the preparation of a novel fibre for wound care application.

A new carbohydrate-based wound dressing fibre with superior absorption and antimicrobial potency.

Heavily exudating wounds can lead to infection and unnecessary trauma if they are not adequately managed. Manufacturers involved in production and marketing of high absorption silver dressings, besides emphasising high absorptions of their dressings are keen to highlight potent antimicrobial abilities of their products against all kinds of pathogens including MRSA. However, there are little or no credible reports on minimal but potent quantities of silver needed in a dressing to eliminate bacteria spread and growth or how effectively the silver within a dressing is released over time. This paper introduces a new hybrid biomaterial fibre made from polysaccharide-based polymers with inbuilt ability to gel and absorb large quantities of pseudo exudates. Furthermore, it will be reported that the new fibre carries up to six times less silver than it is conventionally used in silver dressings and displays a very slow rate of release whilst maintaining full potency over time against known Gram positive, Gram negative micro-organisms including MRSA. The paper concludes that the developed hybrid fibre has long lasting antimicrobial and gelling properties comparable, if not better, than Acticoat AA and Aquacel Ag, two commercially available silver dressings.

Advanced wound care materials: developing an alginate fibre containing branan ferulate.

OBJECTIVE: This laboratory-based study set out to establish whether branan ferulate--a polysaccharide compound available in gels such as as Sterigel (SSL International, UK)--could be successfully added to the fibre of an alginate dressing to provide a superior wound-care dressing. METHOD: A wet extruder (Howden Engineering Services, UK) was used to produce the fibres. Researchers examined the effect of spinning-bath calcium chloride concentration (used as the coagulant in the fibre-spinning process) on the tensile and absorption properties of alginate fibres containing 25% w/w branan ferulate. Sodium alginate and branan ferulate were separately dissolved in de-ionised water and then stirred together to make up a 5% dope solution. The dope was then forced through a spinneret and into the calcium chloride bath, where fibres were precipitated and then carried over the first set of rollers. The fibres were washed in the next bath and drawn at different rates to enhance their tensile properties. At the 'winding-up' stage the filaments were either passed over a contact heater and into a furnace (dry pick-up) or transferred into acetone baths of increasing concentrations of 50, 80 and 100% aqueous acetate to remove the water (wet pick-up). The moisture content of standard alginate fibres and those with branan ferulate were measured and compared. Breaking load, tenacity and breaking extension, and the quantity of branan ferulate in the fibres were also measured. The process was repeated four times, using different strengths of calcium chloride. Using various draw ratios, the effects of liquid uptake were measured using water, saline and a solution called A (to mimic human blood and exudate-type fluids). RESULTS: Out of the four calcium chloride concentrations used, 1% concentration appeared to give the highest and most conclusive results for fibre-breaking load, tenacity and breaking extension. CONCLUSION: A 1% w/v concentration of calcium chloride provides the optimum conditions for achieving suitably strong fibres with adequate absorption capacity, while allowing the least branan ferulate loss during wash and post-production treatments. In a laboratory setting the product showed promise. Research is now needed in a clinical setting and for comparison with existing wound-care products.