Evaluating the Irritant Factors of Silicone and Hydrocolloid Skin Contact Adhesives Using Trans-Epidermal Water Loss, Protein Stripping, Erythema, and Ease of Removal.

A composite silicone skin adhesive material was designed to improve its water vapor permeability to offer advantages to wearer comfort compared to existing skin adhesive dressings available (including perforated silicone and hydrocolloid products). The chemical and mechanical properties of this novel dressing were analyzed to show that it has a high creep compliance, offering anisotropic elasticity that is likely to place less stress on the skin. A participant study was carried out in which 31 participants wore a novel silicone skin adhesive (Sil2) and a hydrocolloid competitor and were monitored for physiological response to the dressings. Trans-epidermal water loss (TEWL) was measured pre- and postwear to determine impairment of skin barrier function. Sil2 exhibited a higher vapor permeability than the hydrocolloid dressings during wear. Peel strength measurements and dye counter staining of the removed dressings showed that the hydrocolloid had a higher adhesion to the participants' skin, resulting in a greater removal of proteins from the stratum corneum and a higher pain rating from participants on removal. Once the dressings were removed, TEWL of the participants skin beneath the Sil2 was close to normal in comparison to the hydrocolloid dressings that showed an increase in skin TEWL, indicating that the skin had been highly occluded. Analysis of the skin immediately after removal showed a higher incidence of erythema following application of hydrocolloid dressings (>60%) compared to Sil2, (<30%). In summary, this modified silicone formulation demonstrates superior skin protection properties compared to hydrocolloid dressings and is more suitable for use as a skin adhesive.

Building the perfect curse word: A psycholinguistic investigation of the form and meaning of taboo words.

Taboo words represent a potent subset of natural language. It has been hypothesized that "tabooness" reflects an emergent property of negative valence and high physiological arousal of word referents. Many taboo words (e.g., dick, shit) are indeed consistent with this claim. Nevertheless, American English is also rife with negatively valenced, highly arousing words the usage of which is not socially condemned (e.g., cancer, abortion, welfare). We evaluated prediction of tabooness of single words and novel taboo compound words from a combination of phonological, lexical, and semantic variables (e.g., semantic category, word length). For single words, physiological arousal and emotional valence strongly predicted tabooness with additional moderating contributions from form (phonology) and meaning (semantic category). In Experiment 2, raters judged plausibility for combinations of common nouns with taboo words to form novel taboo compounds (e.g., shitgibbon). A mixture of formal (e.g., ratio of stop consonants, length) and semantic variables (e.g., ± receptacle, ± profession) predicted the quality of novel taboo compounding. Together, these studies provide complementary evidence for interactions between word form and meaning and an algorithmic prediction of tabooness in American English. We discuss applications for models of taboo word representation.

Mechanism of Hydrogen-Bonded Complex Formation between Ibuprofen and Nanocrystalline Hydroxyapatite.

Nanocrystalline hydroxyapatite (nanoHA) is the main hard component of bone and has the potential to be used to promote osseointegration of implants and to treat bone defects. Here, using active pharmaceutical ingredients (APIs) such as ibuprofen, we report on the prospects of combining nanoHA with biologically active compounds to improve the clinical performance of these treatments. In this study, we designed and investigated the possibility of API attachment to the surface of nanoHA crystals via the formation of a hydrogen-bonded complex. The mechanistic studies of an ibuprofen/nanoHA complex formation have been performed using a holistic approach encompassing spectroscopic (Fourier transform infrared (FTIR) and Raman) and X-ray diffraction techniques, as well as quantum chemistry calculations, while comparing the behavior of the ibuprofen/nanoHA complex with that of a physical mixture of the two components. Whereas ibuprofen exists in dimeric form both in solid and liquid state, our study showed that the formation of the ibuprofen/nanoHA complex most likely occurs via the dissociation of the ibuprofen dimer into monomeric species promoted by ethanol, with subsequent attachment of a monomer to the HA surface. An adsorption mode for this process is proposed; this includes hydrogen bonding of the hydroxyl group of ibuprofen to the hydroxyl group of the apatite, together with the interaction of the ibuprofen carbonyl group to an HA Ca center. Overall, this mechanistic study provides new insights into the molecular interactions between APIs and the surfaces of bioactive inorganic solids and sheds light on the relationship between the noncovalent bonding and drug release properties.

The Effect of Polysialic Acid Expression on Glioma Cell Nano-mechanics.

Polysialic acid (polySia) is an important carbohydrate bio-polymer that is commonly over-expressed on tumours of neuroendocrine origin and plays a key role in tumour progression. polySia exclusively decorates the neural cell adhesion molecule (NCAM) on tumour cell membranes, modulating cell-cell interactions, motility and invasion. In this preliminary study, we examine the nano-mechanical properties of isogenic C6 rat glioma cells-transfected cells engineered to express the enzyme polysialyltransferase ST8SiaII, which synthesises polySia (C6-STX cells) and wild-type cells (C6-WT). We demonstrate that polySia expression leads to reduced elastic and adhesive properties but also more viscoelastic compared to non-expressing wild-type cells. Whilst differences in cell elasticity between healthy and cancer cells are regularly assigned to changes in the cytoskeleton, we show that in this model system, the change in properties at the nano-level is due to the polySia on the transfected cell membrane surface.

Tattoo ink nanoparticles in skin tissue and fibroblasts.

Tattooing has long been practised in various societies all around the world and is becoming increasingly common and widespread in the West. Tattoo ink suspensions unquestionably contain pigments composed of nanoparticles, i.e., particles of sub-100 nm dimensions. It is widely acknowledged that nanoparticles have higher levels of chemical activity than their larger particle equivalents. However, assessment of the toxicity of tattoo inks has been the subject of little research and ink manufacturers are not obliged to disclose the exact composition of their products. This study examines tattoo ink particles in two fundamental skin components at the nanometre level. We use atomic force microscopy and light microscopy to examine cryosections of tattooed skin, exploring the collagen fibril networks in the dermis that contain ink nanoparticles. Further, we culture fibroblasts in diluted tattoo ink to explore both the immediate impact of ink pigment on cell viability and also to observe the interaction between particles and the cells.

Nano-scale observations of tattoo pigments in skin by atomic force microscopy.

In this study, we have shown how particles in carbon black tattoo ink accumulate in the human skin dermis using fine-resolution atomic force microscopy, with which a single ink particle in the collagenous network can be imaged. This information further demonstrates that tattoo inks are nano-particles. Further, we have deposited a commercially available tattoo ink on a glass slide and calculated a range of volumes for single ink particles.

Estimating the mechanical properties of retinal tissue using contact angle measurements of a spreading droplet.

When a drop of liquid is placed on the surface of a soft material, the surface deformation and the rate of spreading of the triple contact point is dependent on the mechanical properties of the substrate. This study seeks to use drop spreading behavior to infer the mechanical properties of soft biological materials. As an illustration of the value of this technique we have compared the spreading behavior of a liquid droplet on two viscoelastic, soft materials, namely, an elastomer and a low concentration agar gel. The ratio of the mechanical properties of these soft materials obtained in this way is confirmed by atomic force microscopy (AFM) nanoindentation. By comparing the spreading behavior of a liquid on the retina with that of the same liquid on each of two viscoelastic materials, we can then estimate the elastic moduli of the retina: an estimate that is extremely difficult to carry out using AFM.

Nano-scale temperature dependent visco-elastic properties of polyethylene terephthalate (PET) using atomic force microscope (AFM).

Visco-elastic behaviour at the nano-level of a commonly used polymer (PET) is characterised using atomic force microscopy (AFM) at a range of temperatures. The modulus, indentation creep and relaxation time of the PET film (thickness=100 µm) is highly sensitive to temperature over an experimental temperature range of 22-175°C. The analysis showed a 40-fold increase in the amount of indentation creep on raising the temperature from 22°C to 100°C, with the most rapid rise occurring above the glass-to-rubber transition temperature (T(g)=77.1°C). At higher temperatures, close to the crystallisation temperature (T(c)=134.7°C), the indentation creep reduced to levels similar to those at temperatures below T(g). The calculated relaxation time showed a similar temperature dependence, rising from 0.6s below T(g) to 1.2s between T(g) and T(c) and falling back to 0.6s above T(c). Whereas, the recorded modulus of the thick polymer film decreases above T(g), subsequently increasing near T(c). These visco-elastic parameters are obtained via mechanical modelling of the creep curves and are correlated to the thermal phase changes that occur in PET, as revealed by differential scanning calorimetry (DSC).

Pseudostatic and dynamic nanomechanics of the tunica adventitia in elastic arteries using atomic force microscopy.

Tunica adventitia, the outer layer of blood vessels, is an important structural feature, predominantly consisting of collagen fibrils. This study uses pseudostatic atomic force microscopy (AFM) nanoindentation at physiological conditions to show that the distribution of indentation modulus and viscous creep for the tunica adventitia of porcine aorta and pulmonary artery are distinct. Dynamic nanoindentation demonstrates that the viscous dissipation of the tunica adventitia of the aorta is greater than the pulmonary artery. We suggest that this mechanical property of the aortic adventitia is functionally advantageous due to the higher blood pressure within this vessel during the cardiac cycle. The effects on pulsatile deformation and dissipative energy losses are discussed.

AFM relative stiffness measurement of the plasticising effect of a non-ionic surfactant on plant leaf wax.

An AFM relative stiffness technique was applied to reconstituted Beta vulgaris L. wax films. Consecutive force arrays (n=100) made on the waxy surface at the same locations showed that there was no relative change in surface elasticity and this information was used as a reference to further experimental measurements. A surfactant solution was subsequently dropped on the waxy surface and the same array of indents was made at the same location as the reference test. The plant wax surface showed a reduction in its surface elasticity properties. The study has demonstrated that the AFM technique could be used to undertake a systematic assessment of the plasticising effects of agrochemicals on native and reconstituted plant wax films.

A comparative study of wire fixation and screw fixation in arthrodesis for the correction of hallux rigidus using an in vitro biomechanical model.

BACKGROUND: Arthrodesis of the great toe metatarsophalangeal joint for osteoarthritis usually involves internal fixation. Ideally, the fixation method should be reproducible, leading to a high rate of fusion and minimal complications. METHODS: This biomechanical study compares circumferential wire and screw fixation methods of arthrodesis. RESULTS: The two arthrodesis models have remarkably similar limits of elastic and plastic deformation. However, in the screw, failure by permanent deformation occurs at a load six times higher than the wire. CONCLUSIONS: The use of circumferential wire fixation for osteoporotic bones in which screw purchase is poor is reasonable and for quality bone, screw fixation may be preferable.

Biphasic surface amorphous layer lubrication of articular cartilage.

The biphasic nature of articular cartilage has been acknowledged for some time and is known to play an important role in many of the biomechanical functions performed by this unique tissue. From the lubrication point of view however, a simple biphasic model is unable to account for the extremely low friction coefficients that have been recorded experimentally, particularly during start-up. In addition, research over the last decade has indicated the presence of a surface amorphous layer on top of articular cartilage. Here, we present results from a finite element model of articular cartilage that includes a thin, soft, biphasic surface amorphous layer (BSAL). The results of this study show that a thin BSAL, with lower elastic modulus, dramatically altered the load sharing between the solid and liquid phases of articular cartilage, particularly in the near-surface regions of the underlying bulk cartilage and within the surface amorphous layer itself where the fluid load support exceeded 85%. By transferring the load from the solid phase to the fluid phase, the biphasic surface layer improves lubrication and reduces friction, whilst also protecting the underlying cartilage surface by 'shielding' the solid phase from elevated stresses. The increase in lubrication effectiveness is shown to be greatest during short duration loading scenarios, such as shock loads.

Functional outcome following bone transport reconstruction of distal tibial defects.

BACKGROUND: Little has been written about the functional outcome of patients treated with bone transport to reconstruct a distal tibial defect. The aim of this study was to investigate the functional capabilities of patients who had undergone reconstruction with distraction osteogenesis for the treatment of a distal tibial defect in one lower limb. METHODS: At least eighteen months after completion of treatment, eight patients who had no pain and were able to walk and climb stairs without difficulty performed isometric ankle plantar flexion maximum voluntary contractions while the electromyographic activity of the tibialis anterior and triceps surae muscles was simultaneously recorded. Seven of the patients also underwent gait analysis. Data for the involved limb were compared with those collected for the contralateral limb. RESULTS: During gait, stance time (p = 0.01), the plantar flexion angular displacement and peak moment developed during the second half of stance (p < 0.046), and the amount of ankle power generated (p = 0.02) were significantly decreased in the involved limb compared with the contralateral limb. Similar decreases were observed in the plantar flexion (p = 0.01) and dorsiflexion (p = 0.01) maximum voluntary contractions and the corresponding electromyographic activity (p = 0.01). CONCLUSIONS: These results suggest that adaptive changes had occurred at the level of the transported muscles, which affected both routine and maximal effort capabilities. These findings contribute to our understanding of the functional limitations of patients who have undergone bone transport with its obligatory shortening of muscle length.