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The importance of the microstzructure of silicone hydrogels is widely appreciated but is poorly understood and minimally investigated. To ensure comfort and eye health, these materials must simultaneously exhibit both high oxygen and high water permeability. In contrast with most conventional hydrogels, the water content and water structuring within silicone hydrogels cannot be solely used to predict permeability. The materials achieve these opposing requirements based on a composite of nanoscale domains of oxygen-permeable (silicone) and water-permeable hydrophilic components. This study correlated characteristic ion permeation coefficients of a selection of commercially available silicone hydrogel contact lenses with their morphological structure and chemical composition. Differential scanning calorimetry measured the water structuring properties through subdivision of the freezing water component into polymer-associated water (loosely bound to the polymer matrix) and ice-like water (unimpeded with a melting point close to that of pure water). Small-angle x-ray scattering, and environmental scanning electron microscopy techniques were used to investigate the structural morphology of the materials over a range of length scales. Significant, and previously unrecognized, differences in morphology between individual materials at nanometer length scales were determined; this will aid the design and performance of the next generation of ocular biomaterials, capable of maintaining ocular homeostasis.

Ternary-blended, melt-blown films of polylactide (PLA), polycaprolactone (PCL) and cellulose acetate butyrate (CAB) were prepared from preliminary miscibility data using a rapid screening method and optical ternary phase diagram (presented as clear, translucent, and opaque regions) as a guide for the composition selection. The compositions that provided optically clear regions were selected for melt blending. The ternary (PLA/PCL/CAB) blends were first melt-extruded and then melt-blown to form films and characterized for their tensile properties, tensile fractured-surface morphology, miscibility, crystallinity, molecular weight and chemical structure. The results showed that the tensile elongation at the break (%elongation) of the ternary-blended, melt-blown films (85/5/10, 75/10/15, 60/15/25 of PLA/PCL/CAB) was substantially higher (>350%) than pure PLA (ca. 20%). The range of compositions in which a significant increase in %elongation was observed at 55–85% w/w PLA, 5–20% w/w PCL and 10–25% w/w CAB. Films with high %elongation all showed good interfacial interactions between the dispersed phase (PCL and CAB) and matrix (PLA) in FE-SEM and showed improvements in miscibility (higher intermolecular interaction and mixing) and a decrease in the glass transition temperature, when compared to the low %elongation films. The decrease in Mw and Mn and the formation of the new NMR peaks (1H NMR at 3.68–3.73 ppm and 13C NMR at 58.54 ppm) were observed in only the high %elongation films. These are expected to be in situ compatibilizers that are generated during the melt processing, mostly by chain scission. In addition, mathematical modelling was used to study the optimal ratio and cost-effectiveness of blends with optimised mechanical properties. These ternary-blended, melt-blown films have the potential for use in both packaging and medical devices with excellent mechanical performance as well as inherent economic and environmental capabilities.

Understanding the underlying role of microstructural design in polymers allows for the manipulation and control of properties for a wide range of specific applications. As such, this work focuses on the study of microstructure–property relationships in l-lactide/ϵ-caprolactone (LL/CL) copolymers. One-step and two-step bulk ring-opening polymerization (ROP) procedures were employed to synthesize LL/CL copolymers of various compositions and chain microstructures. In the one-step procedure, LL and CL were simultaneously copolymerized to yield P(LL-stat-CL) statistical copolymers. In the two-step procedure, poly(l-lactide) (PLL) and poly(ϵ-caprolactone) (PCL) prepolymers were synthesized in the first step before CL and LL respectively were added in the second step to yield P[LL-b-(CL-stat-LL)-b-LL] and P[CL-b-(LL-stat-CL)-b-CL] block copolymers as the final products. The findings reveal that, in addition to the copolymerization procedure employed, the length and type of the prepolymer play important roles in determining the chain microstructure and thereby the overall properties of the final copolymer. Moreover, control over the degree of crystallinity and the type of crystalline domains, which is controlled during the polymer chemistry process, heavily influences the physical and mechanical properties of the final polymer. In summary, this work describes an interesting approach to the microstructural design of biodegradable copolymers of LL and CL for potential use in biomedical applications.

Regards to the global prevalence of diabetes, clinical management should tackle the awkwardness of continuous glucose monitoring systems (CGMS). Although CGMS are commercially accepted, they are still suffering due to their low sustainability and reusability. One method to circumvent these shortcomings is the immobilization of enzymes onto stable carriers. In this contribution, our aim was to build up a highly stable and reproducible enzyme-based host–guest carrier from maltose-modified hyperbranched poly(ethylene imine) (PEI-Mal-C) and polyelectrolyte multilayers (PEMs) to monitor glucose level. Thus, enzymes, such as glucose oxidase (GOx) and horseradish peroxide (POx), were immobilized in core–shell PEI-Mal-C and highly packaged in carrier-based PEM. Herein, the PEM was created using the layer-by-layer protocol, where a consecutive deposition of polyions was achieved. Therein, the polycation PEI-Mal-C was alternatively deposited with different polyanions, e.g., poly(acrylic acid) and heparin (HE), on a solid substrate. The enzyme immobilization, leaching and enzymatic activity were investigated through different modules, including ultraviolet–visible (UV–Vis) spectrophotometer, rheometer, X-ray spectroscopy, contact angle meter, atomic force microscopy and conductometer. To conclude, our approach enabled the use of immobilized GOx/POx for more than one time with the significantly similarly fitted regression calibration curve. It is implied that this work will be the first step to construct a stable hyperbranched glyconanomaterial-immobilized enzyme based on assembled multilayers, with the potential to be applied in a stable and reusable biosensor.

BackgroundTear film stability is important for healthy visual function, and yet little is known of the ageing mechanisms. The aim of this study was to investigate parallels between biochemical changes and clinical physical parameters, which occur in the tear film of two subject populations differing in age by over 30 years.MethodsTwo distinct age groups were chosen: 11 ‘younger’ (23.7±2.1 years) and 19 ‘older’ (63.0±4.0 years) subjects. A series of clinical tests were performed to access tear volume, tear film stability and general ocular health. Tear protein analyses from extracted Schirmer strips were conducted with the Agilent 2100 Bioanalyzer.ResultsClinical investigations highlighted significant differences between the age groups. For example: McMonnies scores (p=0.009) and bulbar redness (p=0.038) were higher for the older group, whereas tear meniscus height was larger (p=0.018) in the younger group. Similarly, relative plasma-derived albumin levels were higher (17.1%±12.4%) in the tears of the older, compared with the younger (5.0%±9.6%) group. A protein peak at ∼23 kDa was observed in 53% of the older group samples but in only 36% of the samples of the younger subjects (p=0.122).ConclusionsDistinct differences in tear film composition between the two age groups were observed. Parallels in terms of clinical symptoms which reflected a biochemical response (and vice versa) were found, but specific correlations between clinical measurements and biomarkers for individual subjects were not observed.

Ability of poly (styrene-alt-maleic anhydride) (PSMA) to undergo a conformational transition into an amphipathic α-helix coil offers one possible mechanism by which PSMA surface activity can be switched on or off in response to the pH change. This behaviour allows it to be useful in membrane solubilization for extraction technology. Bioactive compounds are recovered from plant tissues for different reasons. One of the most important reasons is due to the increased demand in nutraceuticals market and modern therapeutics. Despite this, aqueous-based extraction of these compounds has been reported to give low extraction yield. A development of new green extraction protocol is still a challenging task for all researchers nowadays. This study demonstrated, for the first time, possible use of PSMA as a lysis agent for plant bioactive compound extraction. To enhance its membrane affinity at physiological pH, the polymer was esterified with methanol. Both PSMA and its derivative (ePSMA) were characterized in terms of their membrane binding affinity through a combined use of both surface characterization and physical techniques. Analysis of the ternary phase diagrams suggested that ePSMA could facilitate stronger hydrophobically-driven interactions with the lipid. This was convinced by the reduced critical PSMA/lipid mass ratio from 7:1 (PSMA) to 1:1 (ePSMA), as observed in the ternary phase diagrams. Last but not the least, the crude extracts of Coffea robusta leaves obtained from ePSMA-based extraction showed a total phenolic content of 20.32±0.75 mg/g sample, significantly higher than that from the PSMA- (14.24±1.27 mg/g sample) and aqueous-based (16.33±1.03 mg/g sample) extractions. A structural manipulation of PSMA is thus a key to tailor its membrane solubilization and so, the extraction efficacy of bioactive compounds from plant cells.

In the quest for commercially relevant block copolymer additives, for which overall average molecular composition is key but molar mass distribution is of little importance, we present a straightforward, sulfur- and metal-free aqueous route to block copolymers using commercially available starting materials. Based on synthetic techniques first described in the 1950s for hydrophobic monomers in organic solvents, we have shown that bromoform (CHBr3) can be used to create block copolymers. Unlike common bromine-containing chain transfer agents such as carbon tetrabromide (CBr4), bromoform is partially water-miscible and relatively inexpensive. Herein, we demonstrate this new aqueous-based technology using N,N-dimethylacrylamide (DMA) and N-isopropylacrylamide (NIPAM) as exemplar monomers to synthesise PDMA-b-PNIPAM block copolymers of varying composition directly in water. This study demonstrates the potential for such a simple, inexpensive route to functional block copolymers where further research to decipher the detailed mechanism and true potential of this technique will be of great value.

The potential of naturally occurring substances as a source of biomedical materials is well-recognised and is being increasingly exploited. Silk fibroin membranes derived from Bombyx mori silk cocoons exemplify this, for example as substrata for the growth of ocular cells with the aim of generating biomaterial-cell constructs for tissue engineering. This study investigated the transport properties of selected silk fibroin membranes under conditions that allowed equilibrium hydration of the membranes to be maintained. The behaviour of natural fibroin membranes was compared with fibroin membranes that have been chemically modified with poly(ethylene glycol). The permeation of the smaller hydrated sodium ion was higher than that of the hydrated calcium ion for all three ethanol treated membranes investigated. The PEG and HRP-modified C membrane, which had the highest water content at 59.6 ± 1.5% exhibited the highest permeation of the three membranes at 95.7 ± 2.8 × 10–8 cm2 s−1 compared with 17.9 ± 0.9 × 10–8 cm2 s−1 and 8.7 ± 1.7 × 10–8 cm2 s−1 for membranes A and B respectively for the NaCl permeant. Poly(ethylene glycol) was used to increase permeability while exploiting the crosslinking capabilities of horseradish peroxidase to increase the compressive strength of the membrane. Importantly, we have established that the permeation behaviour of water-soluble permeants with hydrated radii in the sub-nanometer range is analogous to that of conventional hydrogel polymers.

Denture adhesives are designed to be moisture-sensitive through the inclusion of a blend of polymer salts with varying degrees of water-sensitivity. This enables the adhesive to mix with saliva in vivo and activate its high tack, through the formation of a mucilaginous layer. We report for the first time, the use of differential scanning calorimetry to study a series of hydrophobic and hydrophilic polymeric systems in order to correlate water-structuring behavior with adhesion strength. Adhesive bonding of the more hydrophobic variants was higher than that of a commercial-based control and a more hydrophilic polymer system in both lap shear and tensile configurations. Water-binding data suggested that increasing the hydrophobicity of the maleic acid copolymer substituents led to decreased levels of freezing water. In comparison, increasing the hydrophilic nature of the polymer backbone gave higher levels of freezing water within the hydrated samples. The results of this study emphasize the importance of varying the levels of hydrophobic and hydrophilic components within denture adhesive formulations, alongside the types of water present within the adhesive systems. This phenomenon has shown the potential to fine-tune the adhesive properties and failure mode against poly(methyl methacrylate), surfaces. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1355-1362, 2018.

Biodegradable blends of poly(l-lactide) (PLL) toughened with a polycaprolactone-based thermoplastic polyurethane (TPU) elastomer and compatibilized with a purpose-designed poly(l-lactide-co-caprolactone) (PLLCL) copolymer were prepared. Both 2-component (PLL/TPU) and 3-component (PLL/TPU/PLLCL) blends of various compositions were prepared by melt mixing, hot-pressed into thin films and their properties tested. The results showed that, although the TPU could toughen the PLL, the blends were immiscible leading to phase separation with the TPU domains distributed in the PLL matrix. However, addition of the PLLCL copolymer could partially compatibilize the blend by improving the interfacial adhesion between the two phases. Biodegradability testing showed that the blends were biodegradable and that the PLLCL copolymer could increase the rate of biodegradation under controlled composting conditions. The 3-component blend of composition PLL/TPU/PLLCL = 90/10/10 parts by weight was found to exhibit the best all-round properties.

Purpose: This review summarises the way in which mechanical property measurements combined with clinical perception have influenced the last half century of materials evolution in contact lens development. Methods: Literature concerning the use of . in-vitro testing in assessment of the mechanical behaviour of contact lenses, and the mutual deformation of the lens material and ocular tissue was examined. Tensile measurements of historic and available hydrogel lenses have been collected, in addition to manufacturer-generated figures for the moduli of commercial silicone hydrogel lenses. Results: The three conventional modes of mechanical property testing; compression, tension and shear each represent different perspective in understanding the mutual interaction of the cornea and the contact lens. Tensile testing provides a measure of modulus, together with tensile strength and elongation to break, which all relate to handling and durability. Studies under compression also measure modulus and in particular indicate elastic response to eyelid load. Studies under shear conditions enable dynamic mechanical behaviour of the material to be assessed and the elastic and viscous components of modulus to be determined. These different methods of measurement have contributed to the interpretation of lens behaviour in the ocular environment. An amalgamated frequency distribution of tensile moduli for historic and currently available contact lens materials reveals the modal range to be 0.3-0.6. MPa. Conclusion: Mechanical property measurements of lens materials have enabled calibration of an important aspect of their ocular interaction. This together with clinical feedback has influenced development of new lens materials and assisted clinical rationalisation of in-eye behaviour of different lenses.

The use of styrene maleic acid co-polymer (SMA) for membrane protein extraction and purification has grown in recent years. SMA inserts in the membrane and assembles into small discs of bilayer encircled by polymer, termed SMA lipid particles (SMALPs). This allows purification of membrane proteins whilst maintaining their lipid bilayer environment. SMALPs offer several improvements over conventional detergent approaches, however there are limitations, most notably a sensitivity to low pH and divalent cations. Recently it was shown that the aliphatic diisobutylene-maleic acid (DIBMA) copolymer, was also able to directly solubilise membranes forming DIBMALPs (DIBMA lipid particles), and that this polymer overcame some of the limitations of SMA. In this study the ability of DIBMA to solubilise and purify functional membrane proteins has been compared to SMA. It was found that DIBMA is able to solubilise several different membrane proteins from different expression systems, however for some proteins it gives a lower yield and lower degree of purity than SMA. DIBMA extracted G protein-coupled receptors retain ligand- and G protein-binding. DIBMALPS are larger than SMALPs and display a decreased sensitivity to magnesium. However the stability of DIBMALPs appears to be lower than SMALPs. The lower purity and lower stability are likely linked to the larger size of the DIBMALP particle. However, this also offers a potentially less rigid lipid environment which may be more amenable to protein dynamics. Therefore the optimal choice of polymer will depend on which features of a protein are to be investigated.

The health of the cornea is paramount; the aim of this study was to assess the permeation of essential tear electrolytes through a range of commercial contact lenses. Donor/receiver conductivity measurements were recorded using a dual‐chamber diffusion system which allowed material permeability profiles and coefficients to be calculated. Water structuring properties of the contact lenses were measured by differential scanning calorimetry. Freezing water was subdivided into “ice‐like” water (free, non‐bound and has a melting point close to that of pure water) and polymer‐associated water (free but loosely bound to the polymer matrix). Each material interacts differently with each of the three salts, for example; lotrafilcon B (34% equilibrium water content [EWC]) shows a higher and larger range of receiver concentrations post KCl, NaCl, CaCl2 permeation (76, 59 and 42 mM, respectively) compared with the lower and tighter range exhibited by lotrafilcon A (22% EWC) (36, 22, and 18 mM, respectively). Additionally, in terms of the relationship between permeation and water structure, balafilcon A (34% EWC) has a high KCl permeation (P60 258 × 10−8 cm2/s) and ice‐like water (14%), but narafilcon A (44% EWC) has a low ion permeation (P60 3.9 × 10−8 cm2/s) and significantly less ice‐like water (4%). The permeation trends for the silicone hydrogel materials could not be fully explained by water content and structuring. Composition and, in particular, the microstructure and morphology of these materials must impart a greater influence on permeation capability.

This study identifies and investigates the potential use of in-eye trigger mechanisms to supplement the widely available information on release of ophthalmic drugs from contact lenses under passive release conditions. Ophthalmic dyes and surrogates have been successfully employed to investigate how these factors can be drawn together to make a successful system. The storage of a drug-containing lens in a pH lower than that of the ocular environment can be used to establish an equilibrium that favours retention of the drug in the lens prior to ocular insertion. Although release under passive conditions does not result in complete dye elution, the use of mechanical agitation techniques which mimic the eyelid blink action in conjunction with ocular tear chemistry promotes further release. In this way differentiation between passive and triggered in vitro release characteristics can be established. Investigation of the role of individual tear proteins revealed significant differences in their ability to alter the equilibrium between matrix-held and eluate-held dye or drug. These individual experiments were then investigated in vivo using ophthalmic dyes. Complete elution was found to be achievable in-eye; this demonstrated the importance of that fraction of the drug retained under passive conditions and the triggering effect of in-eye conditions on the release process. Understanding both the structure-property relationship between drug and material and in-eye trigger mechanisms, using ophthalmic dyes as a surrogate, provides the basis of knowledge necessary to design ocular drug delivery vehicles for in-eye release in a controllable manner.

The importance of the microstructure on the permeability of silicone hydrogels is widely appreciated but is poorly understood and minimally investigated. In contrast with most conventional hydrogels, the water content and water structuring within silicone hydrogels cannot be solely used to predict their permeability. To ensure comfort and eye health, these materials must simultaneously exhibit both high oxygen permeability and high water permeability. The materials achieve these opposing requirements based on a composite of nanoscale domains of oxygen-permeable (silicone) and water-permeable hydrophilic components. This study correlated the ion permeation coefficients of a selection of commercially available silicone hydrogel contact lenses with their morphological structure and chemical composition. Donor/receiver conductivity measurements were recorded using a dual-chamber diffusion system, which allowed permeability profiles and coefficients to be calculated. Differential scanning calorimetry was used to measure water structuring properties through subdivision of the freezing water component into polymer-associated water (loosely bound to the polymer matrix) and ice-like water (unimpeded with a melting point close to that of pure water). Small-angle x-ray scattering, and environmental scanning electron microscopy techniques were used to investigate the structural morphology of the material over a range of length scales. Significant, and previously unrecognised, differences in morphology between individual materials at nanometre length scales were determined. These exploratory techniques facilitate the understanding of the effects of the bulk morphology on the permeability behaviour of each silicone material; this will aid the design and performance of the next generation of ocular biomaterials, capable of maintaining enhanced ocular homeostasis.

Native cassava starch (CS) is chemically modified by grafting with 2‐ethylhexyl acrylate (EHA) monomer to make it more hydrophobic for improved blending with poly(lactic acid) (PLA). Grafting is carried out using CS:EHA weight ratios of 2:1, 1:1, 1:2, and 1:3 in a methanol‐water solvent mixture at 45 °C for 48 h. L‐Ascorbic acid and hydrogen peroxide are used as the redox initiating system. Following purification, the poly(2‐ethylhexyl acrylate)‐grafted starch, starch‐g‐PEHA, is obtained either as a finely divided powder or as a slightly tacky solid with % grafting values in the range of 13–26% by weight. The main objective of this chemical modification is to improve the interfacial adhesion between the starch particles and the PLA matrix through the hydrophobic PLA‐PEHA interactions. PLA/starch‐g‐PEHA blends are prepared in the form of solution‐cast films with weight ratios ranging from 100/0 to 60/40. Tensile testing of the films shows a marked increase in extensibility and toughness up to a loading of 10% starch‐g‐PEHA above which the properties deteriorated rapidly due to starch particle aggregation. Thus, for potential use as biodegradable film packaging, the best properties are obtained for the PLA/starch‐g‐PEHA 90/10 blend.

A poly(L-lactide-co-caprolactone) copolymer, P(LL-co-CL), of composition 75:25 mol% was synthesized via the bulk ring-opening copolymerization of L-lactide and e-caprolactone using a novel bis[tin(II) monooctoate] diethylene glycol coordination-insertion initiator, OctSn-OCH2CH2OCH2CH2O-SnOct. The P(LL-co-CL) copolymer obtained was characterized by a combination of analytical techniques, namely nuclear magnetic resonance spectroscopy, gel permeation chromatography, dilute-solution viscometry, differential scanning calorimetry, and thermogravimetric analysis. For processing into a monofilament fiber, the copolymer was melt spun with minimal draw to give a largely amorphous and unoriented as-spun fiber. The fiber's oriented semicrystalline morphology, necessary to give the required balance of mechanical properties, was then developed via a sequence of controlled offline hot-drawing and annealing steps. Depending on the final draw ratio, the fibers obtained had tensile strengths in the region of 200–...

Various lubricating body fluids at tissue interfaces are composed mainly of combinations of phospholipids and amphipathic apoproteins. The challenge in producing synthetic replacements for them is not replacing the phospholipid, which is readily available in synthetic form, but replacing the apoprotein component, more specifically, its unique biophysical properties rather than its chemistry. The potential of amphiphilic reactive hypercoiling behaviour of poly(styrene-alt-maleic acid) (PSMA) was studied in combination with two diacylphosphatidylcholines (PC) of different chain lengths in aqueous solution. The surface properties of the mixtures were characterized by conventional Langmuir-Wilhelmy balance (surface pressure under compression) and the du Nouy tensiometer (surface tension of the non-compressed mixtures). Surface tension values and 31P NMR demonstrated that self-assembly of polymer-phospholipid mixtures were pH and concentration-dependent. Finally, the particle size and zeta potential measurements of this self-assembly showed that it can form negatively charged nanosized structures that might find use as drug or lipids release systems on interfaces such as the tear film or lung interfacial layers. The structural reorganization was sensitive to the alkyl chain length of the PC.

Summary Summary A poly(l-lactide-co-caprolactone), P(LL-co-CL), 75:25 mol % copolymer was synthesized via the bulk ring-opening copolymerization of l-lactide (LL) and ϵ-caprolactone (CL) at 130 °C for 48 hrs. The P(LL-co-CL) copolymer obtained was characterized in terms of its molecular weight (GPC), copolymer composition (1H-NMR), monomer sequencing (13C-NMR) and thermal properties (DSC, TGA). For processing, the P(LL-co-CL) was melt spun into a monofilament fiber with fast cooling and minimal draw in order to produce an as-spun fiber that was largely amorphous and unoriented. This enabled the required oriented semi-crystalline morphology to be gradually built into the as-spun fiber in a series of controlled off-line annealing and hot-drawing steps. The final fiber, which combined sufficient tensile strength with flexibility for use as a suture material, exhibited a stress and strain at break of 344 MPa and 70%, respectively.

Denture adhesives are designed to be moisture-sensitive through the inclusion of a blend of polymer salts with varying degrees of water-sensitivity. This enables the adhesive to mix with saliva in vivo and activate its high tack, through the formation of a mucilaginous layer. We report for the first time, the use of differential scanning calorimetry to study a series of hydrophobic and hydrophilic polymeric systems in order to correlate water-structuring behavior with adhesion strength. Adhesive bonding of the more hydrophobic variants was higher than that of a commercial-based control and a more hydrophilic polymer system in both lap shear and tensile configurations. Water-binding data suggested that increasing the hydrophobicity of the maleic acid copolymer substituents led to decreased levels of freezing water. In comparison, increasing the hydrophilic nature of the polymer backbone gave higher levels of freezing water within the hydrated samples. The results of this study emphasize the importance of varying the levels of hydrophobic and hydrophilic components within denture adhesive formulations, alongside the types of water present within the adhesive systems. This phenomenon has shown the potential to fine-tune the adhesive properties and failure mode against poly(methyl methacrylate), surfaces. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1355-1362, 2018.

Purpose: The aim of this work was to investigate the locus and extent of vitronectin (Vn) deposition on ex vivo contact lenses and to determine the influence of wear modality together with surface and bulk characteristics of the lens material. Methods: The quantity and location of Vn deposition on the surfaces of contact lens materials was investigated using a novel on-lens cell attachment assay technique. Results: Vn mapping showed that deposition resulted from lens-corneal interaction rather than solely from the tear film. Higher cell counts on the posterior surface of the lenses were determined in comparison to the anterior surface. Overall gross Vn deposition was greater for high water content-low modulus materials (117. ±. 4 average cell count per field) than low water content-high modulus materials (88. ±. 6 average cell count per field). Conclusions: The role of Vn in plasmin regulation and upregulation is widely recognised. The findings in this paper suggest that the locus of Vn on the contact lens surface, which is affected by material properties such as modulus, is potentially an important factor in the generation of plasmin in the posterior tear film. Consequently, the potential for materials to affect Vn deposition will influence lens-induced inflammatory processes.

Purpose: The use of the Schirmer strips (SS) as a tool in the characterisation of dry eye disease, depends upon the quantitative assessment of tear production and constituents. The aim of this study was to ascertain the extent to which the properties of commercially available SS can vary and the way in which this baseline information may relate to their comparability in clinical use. Methods: Five SS were analysed: Clement Clarke®, TearFlo®, Bio Schirmer®, Omni Schirmer® and JingMing®. Various aspects of their physical appearance and physicochemical behaviour were measured, including size, weight, and thickness together with surface morphology (assessed by SEM) and aqueous uptake and release behaviour (including the influence of each strip on protein retention and eluent osmolarity). Results: All physical parameters varied between the strips studied for example the Clement Clark was the largest, thickest, and heaviest strip assessed in this study. SEM images showed that each of the SS had unique surface morphologies. Statistically significant differences among the strips were found for uptake (p = 0.001) and release volume (p = 0.014). Clement Clarke absorbed the highest volume over a fixed time period (23.8. ±. 1.6. μl) and Omni the lowest (19.3. ±. 0.5. μl). Clement Clarke showing the highest eluent osmolarity value (5.0. ±. 0.0. mOsm/L) and TearFlo the lowest (2.8. ±. 0.4. mOsm/L). Conclusion: The five strips investigated in this study indicate that there is no standardisation of commercial strips, despite the fact that the need for standardisation was recognised over fifty years ago. This study provides useful baseline information relating to SS comparability in clinical use.

Nature provides many interesting examples of adhesive strategies. Of particular note, the protein glue secreted by marine mussels delivers high adhesion in wet and dynamic environments owing to existence of catechol moieties. As such, this study focuses on denture fixatives, where a non-zinc-containing commercial-based formulation has been judiciously modified by a biomimetic catechol-inspired polymer, poly(3,4-dihydroxystyrene/styrene-alt-maleic acid) in a quest to modulate adhesive performance. In vitro studies, in a lap-shear configuration, revealed that the catechol-modified components were able to enhance adhesion to both the denture base and hydrated, functional oral tissue mimic, with the resulting mode of failure prominently being adhesive rather than cohesive. These characteristics are desirable in prosthodontic fixative applications, for which temporary adhesion must be maintained, with ultimately an adhesive failure from the mucosal tissue surface preferred. These insights provide an experimental platform in the design of future biomimetic adhesive systems. Statement of Significance: Mussel adhesive proteins have proven to be promising biomimetic adhesive candidates for soft tissues and here for the first time we have adapted marine adhesive technology into a denture fixative application. Importantly, we have incorporated a soft tissue mimic in our in vitro adhesion technique that more closely resembles the oral mucosa than previously studied substrates. The novel biomimetic-modified adhesives showed the ability to score the highest adhesive bonding out of all the formulations included in this study, across all moisture levels.This paper will be of major interest to the Acta Biomaterialia readership since the study has illustrated the potential of biomimetic principles in the design of effective prosthodontic tissue adhesives in a series of purpose-designed in vitro experiments in the context of the challenging features of the oral environment.

Poly (L-lactide-co-ε-caprolactone) 75:25 % mol, P(LL-co-CL), was synthesized via bulk ring-opening polymerisation (ROP) using a novel tin (II) alkoxide initiator, [Sn (Oct)]2DEG, at 130°C for 48 hrs. The effectiveness of this initiator was compared withthe well-known conventional tin (II) octoateinitiator, Sn (Oct)2. The P(LL-co-CL) copolymersobtained were characterized using a combination of analytical technique including: nuclear magnetic resonance spectroscopy (NMR), differential scanning calorimetry (DSC), thermogravimetry (TG) and gel permeation chromatography (GPC). The P(LL-co-CL) was melt-spun into monofilament fibres of uniform diameter and smooth surface appearance. Modification of the matrix morphology was then built into the as-spun fibresvia a series of controlled off-line annealing and hot-drawing steps.

Purpose Polyquaternium (PQ) antibacterials, particularly PQ-1, are common components of ophthalmic care solutions. Similarly, the antimicrobial applications of silver in medical devices are well-known. The observation that silver nanoparticles (AgNPs) complexed with PHMB show synergistically enhanced activity led us to investigate the families of novel nanostructures formed through complexation of AgNPs with (initially non-antimicrobial) PQs. Interest centres on synergistic activity and potential ophthalmic applications. Method Silver nanoparticles were synthesised from silver nitrate with sodium borohydride reducing agent and one of the following polyquaterniums: polyquaternium-4 (PQ-4), polyquaternium-10 (PQ-10) and polyquaternium-46 (PQ-46). The filtered nanoparticles were then characterised using dynamic light scattering (DLS) and UV-Visible spectroscopy. Initial studies of antimicrobial activity were carried out with Staphylococcus Aureus, a common ocular pathogen. Results Successful synthesis of silver-PQ nanoparticles was confirmed by UV-Visible spectroscopy, which indicated a surface plasmon resonance (SPR) band of 402 nm ± 1 nm for silver-PQ-10 nanoparticles, a SPR band of 406 nm ± 3 nm for silver-PQ-4 nanoparticles and a SPR band of 447 nm ± 24 nm for silver-PQ-46 nanoparticles. Antimicrobial activity was assessed with zone of inhibition (ZOI) measurements. Silver-PQ-46 nanoparticles displayed a level of antimicrobial activity (12 mm ± 0.5 mm) higher than that of silver nanoparticles synthesised without any polyquaternium (9 mm ± 1 mm) and silver nanoparticles made with PQ-4 and PQ-10 (8 mm ± 1 mm and 7 mm ± 1 mm respectively) exhibited a slightly lower level of activity. None of the polyquaterniums displayed antimicrobial activity alone. Conclusion Novel hybrid antimicrobials, in the form of silver-PQ46 nanoparticles, demonstrated an enhanced level of activity when compared with the unmodified polyquaterniums. This provided an interesting new platform to improve the efficacy of current ocular antimicrobials. These complexes -especially those based on PQs with inherent antimicrobial activity – may have potential for use in ophthalmic devices.

Albumin in tears is used as a diagnostic marker of ocular insult and inflammation, but whether its presence in tears is responsive or part of an adaptive reaction remains unresolved. A review of the literature on tear albumin concentration emphasizes that variables such as collection method, stimulus, assay technique, and disease state influence the quoted values to different extents. Influence of assay technique is negligible in comparison to variation in sampling conditions. Ocular disease increases albumin concentrations but not in a specific manner. The literature review also highlighted that little systematic research has been carried out on the daily cycle of tear albumin levels. In order to remedy this shortcoming, we investigated variations in tear albumin concentration during the waking day. The concentration of albumin in 400 tear samples collected from 13 subjects was assessed at 2-hourly intervals throughout the waking day. Highest daytime albumin concentrations were obtained within 10 minutes of waking, with a mean concentration of >50 ± 22 μg/ml. Albumin levels were at their lowest, but most consistent, 2-6 hours post-waking. This pattern was followed by a progressive increase in albumin concentration during the latter part of the day. Although individual subject-to-subject concentration differences were observed, this distinctive pattern of diurnal variation was found in all subjects. The results presented suggest a regulated, not random, pattern of variation within the period of study.

The application of a rapid screening method for the construction of ternary phase diagrams is described for the first time, providing detailed visualization of phase boundaries in solvent-mediated blends. Our new approach rapidly identifies ternary blend compositions that afford optically clear materials, useful for applications where transparent films are necessary. The use of 96-well plates and a scanning plate reader has enabled rapid optical characterization to be carried out by transmission spectrophotometry (450 nm), whilst the nature and extent of crystallinity was examined subsequently by wide angle X-ray scattering (WAXS). The moderating effect of cellulose acetate butyrate can be visualized as driving the position of the phase boundaries in poly(l-lactic acid)/polycaprolactone (PLLA/PCL) blends. More surprisingly, the boundaries are critically dependent on the molecular weight of the crystallizable PLLA and PCL, with higher molecular weight polymers leading to blends with reduced phase separation. On the other hand, the propensity to crystallize was more evident in shorter chains. WAXS provides a convenient way of characterizing the contribution of the individual blend components to the crystalline regions across the range of blend compositions.

There are two main drivers for the growing interest in bioplastics: the first is the production of plastics materials and the second is their disposal. This chapter is concerned with both bioplastics based on renewable resources—which may or may not degrade in the environment or a biological host—and materials that are fossil based but are classified as “biodegradable.” The greatest importance currently attaches to materials derived from renewable biological resources that are susceptible to biodegradation to benign products—ultimately carbon dioxide and water. Nonetheless, it is important to consider the complete spectrum of bioplastics in the light of technical, economic, and political considerations. Here, both life-cycle analysis and the quantification of that proportion of a material or product actually of biological origin, will increase in significance as the field develops. Against this background, this chapter reviews the key biodegradable bioplastics, polylactic acid, polyhydroxybutyrate and its copolymers, and poly(butylene succinate) together with the blending and modification techniques that are used to “tailor make” products that can compete technically with conventional commodity plastics. This is followed by consideration of the important complementary area of bioplastics—the use of biological feedstocks to produce a palette of raw materials or building blocks that can then be used in conventional polymer syntheses to produce a range of both biodegradable and nonbiodegradable plastics. An important aspect of this approach is the accessibility and emergence of novel monomers such as 2,5-furandicarboxylic acid, which has led to an interesting alternative to polyethylene terephthalate. This chapter concludes with an overview of the important but potentially contentious area of international standards, which are used to define whether a product can be sold as biodegradable in specific jurisdictions around the world.

Since the initial launch of silicone hydrogel lenses, there has been a considerable broadening in the range of available commercial material properties. The very mobile silicon–oxygen bonds convey distinctive surface and mechanical properties on silicone hydrogels, in which advantages of enhanced oxygen permeability, reduced protein deposition, and modest frictional interaction are balanced by increased lipid and elastic response. There are now some 15 silicone hydrogel material variants available to practitioners; arguably, the changes that have taken place have been strongly influenced by feedback based on clinical experience. Water content is one of the most influential properties, and the decade has seen a progressive rise from lotrafilcon-A (24%) to efrofilcon-A (74%). Moduli have decreased over the same period from 1.4 to 0.3 MPa, but not solely as a result of changes in water content. Surface properties do not correlate directly with water content, and ingenious approaches have been used to achieve desirable improvements (e.g., greater lubricity and lower contact angle hysteresis). This is demonstrated by comparing the hysteresis value of the earliest (lotrafilcon-A, >40°) and most recent (delefilcon-A