Dewetting characteristics of contact lenses coated with wetting agents.

HYPOTHESIS: Although wetting agents have been developed to limit tear film dewetting over contact lenses, systematic analyses correlating wetting agent properties to mechanisms of the tear film destabilization are not readily available. Clarifying destabilization characteristics across key physio-chemical variables will provide a rational basis for identifying optimal wetting agents. EXPERIMENTS: We employ an in-house, in vitro platform to comprehensively evaluate drainage and dewetting dynamics of five wetting agents across seventeen different formulations and two model tear film solutions. We consider the film thickness evolution, film thickness at breakup, dewetted front propagation, and develop correlations to contact angle to compare the samples. FINDINGS: Zwitterionic wetting agents effectively stabilize the tear film by reducing the film thickness at the onset of dewetting, and delaying the propagation of dewetted regions across the lens. Furthermore, tuning wetting agent surface concentrations and utilizing binary mixtures of wetting agents can enhance wetting characteristics. Finally, despite disparities in wetting agent molecular properties, the time to dewet 50% of the lens scales linearly with the product of the receding contact angle and contact angle hysteresis. Hence, we fundamentally establish the importance of minimizing the absolute contact angle and contact angle hysteresis for effective wetting performance.

Determination of the critical hydrophile-lipophile balance of licuri oil from Syagrus coronata: application for topical emulsions and evaluation of its hydrating function

The aims of this study were to determine the critical hydrophile-lipophile balance (HLB) of licuri oil, and to perform a clinical assay to evaluate its hydrating effects. For the determination of the HLB, serial emulsions were prepared with the oil. Regarding the clinical study, 13 human subjects were recruited to evaluate the hydrating power of the emulsified preparation containing licuri oil, and comparing it with the same preparation containing sweet almond oil (SAO). The critical HLB of licuri oil was represented by the zones within the concentrations of 10% for the oil and 15% for the pair of tensoactive agents, with a value of 11.8. Both preparations showed similar hydrating power. We propose that licuri oil can be considered a new lipophilic adjuvant with hydrating characteristics, which can be used in cosmetic preparations, replacing consecrated oils, such as SAO.

O objetivo deste estudo foi determinar o EHL crítico do óleo licuri e realizar um ensaio clínico para avaliar os seus efeitos hidratantes. Para a determinação do EHL foram preparadas emulsões seriadas contendo esse óleo. Em relação ao estudo clínico, avaliamos o poder hidratante de preparação emulsionada com óleo de licuri, comparando-a com a mesma preparação contendo óleo de amêndoas doces (OAD), em 13 voluntários. O EHL crítico do óleo de licuri foi representado pelas zonas dentro das concentrações de 10% para o óleo e 15% para o par de tensoativos, com um valor de 11,8 e ambas as preparações mostraram poder hidratante similar. Desta forma, o óleo de licuri pode ser considerado um novo adjuvante lipofílico com função hidratante, o qual pode ser usado em preparações cosméticas, substituindo óleos de consagrado uso, tais como o OAD.

Comparison of sampling techniques for in-line monitoring using Raman spectroscopy.

Raman spectroscopy is currently of interest as a process monitoring tool for pharmaceutical unit operations. In this study, the performance characteristics of Raman spectrometers with different sampling optics have been investigated in the context of process monitoring, with emphasis being placed on assessing homogeneity in powder blends and following changes in solid-state form during wet granulation. A novel large spot non-contact Raman sampling device was compared with a traditional small spot size non-contact sampling device and an immersion probe. The large spot non-contact optics provided significant advantages over the standard systems both as a result of the enhanced sampling volume and because of the greater robustness of the system to fluctuations in the sampling distance during the wet granulation process.

Improved understanding of factors contributing to quantification of anhydrate/hydrate powder mixtures.

Different spectroscopic approaches have proved to be excellent analytical tools for monitoring process-induced transformations of active pharmaceutical ingredients during pharmaceutical unit operations. In order to use these tools effectively, it is necessary to build calibration models that describe the relationship between the amount of each solid-state form of interest and the spectroscopic signal. In this study, near-infrared (NIR) and Raman spectroscopic methods have been evaluated for the quantification of hydrate and anhydrate forms in pharmaceutical powders. Process type spectrometers were used to collect the data and the role of the sampling procedure was examined. Multivariate regression models were compared with traditional univariate calibrations and special emphasis was placed on data treatment prior to multivariate modeling by partial least squares (PLS). It was found that the measured sample volume greatly affected the performance of the model whereby the calibrations were significantly improved by utilizing a larger sampling area. In addition, multivariate regression did not always improve the predictability of the data compared to univariate analysis. The data treatment prior to multivariate modeling had a significant influence on the quality of predictions with standard normal variate transformation generally proving to be the best preprocessing method. When the appropriate sampling techniques and data analysis methods were utilized, both NIR and Raman spectroscopy were found to be suitable methods for the quantification of anhydrate/hydrate in powder systems, and thus the method of choice will depend on the conditions in the process under investigation.

Fate and effects of polydimethylsiloxane (PDMS) in marine environments.

Polydimethylsiloxanes (PDMS) defoamers are used to improve process efficiency under extreme conditions during gas-oil separation, when other chemicals fail to perform. They are also used to reduce the oil content of process waters discharged to the marine environment, thereby serving an important function in reducing oil pollution. As a consequence of these applications small quantities of PDMS may also be released into the environment. This paper reviews the fate of PDMS in the marine environment and the extensive effect studies that have been conducted. These demonstrate the absence of adverse effects on a wide range of marine species.

Limits of detection of polydimethylsiloxane in (29)Si NMR spectroscopy.

Limits of detection for neat poly(dimethylsiloxane) (PDMS), as detected via (29)Si NMR spectroscopy, were determined by the IUPAC, graphical, and propagation of errors methods from calibration curves obtained using a 7.05 Tesla superconducting magnet equipped with a magic angle spinning (MAS) NMR probe. Under conditions permitting full relaxation of the nuclear spins (recycle time >150 sec), the limit of detection with 128 transients was 1.7, 2.2, and 3.7 mg PDMS (23, 30, and 50 micromoles elemental Si) for the IUPAC, graphical, and propagation of errors methods, respectively. A higher limit of detection results when additional sources of uncertainty are considered. From the strict dependence of the limit of detection on the inverse of the square root of the number of transients signal-averaged, it is possible to extrapolate to a limit of detection of 183 microg PDMS (2.47 micromoles elemental Si) for a 24-hr signal averaging period. This limit of detection is 3 orders of magnitude higher than silicon levels found in human blood.

Exposure to low molecular polyamines during road paving.

Fatty amine wetting agents are used to increase adhesion in bitumen emulsions used in road paving, but commercial fatty amine products are contaminated with low molecular polyamines and alkanol polyamines which are released from the hot bitumen during paving. Polyamines and alkanol polyamines are known to cause eye and respiratory tract irritation and skin sensitization. The exposure of road pavers to ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hydroxyethylethylenediamine, hydroxyethyldiethylenetriamine, monoethanolamine and diethanolamine was studied, since most of these compounds were found in the products used. Personal and static air sampling was performed during road paving. A highly sensitive measurement technique utilizing naphthylisothiocyanate-coated sorbents and filters was used. Exposure was found to be in the range < 0.02-0.5 mg m-3, as total concentration of low molecular polyamines and alkanol polyamines. Since the polyamines and alkanol polyamines in question are highly irritating they may contribute to the symptoms experienced by the road pavers.

What's artificial in artificial tears?

After reviewing tear film physiology, and tear film disorders, the author discusses the ingredients found in artificial tear solutions. Choosing the best artificial tear solution for each patient is often confusing because many solutions are available. Understanding the actions of these preparations will aid the practitioner in prescribing more effectively and efficiently for patients.

Colloid osmotic pressure of artificial tears.

While the total osmolality of the aqueous tears and tear substitutes has received much attention in the past few years, the colloidal osmolality or the oncotic pressure (which includes the Donnan effect), has received practically no attention except for one single foreign publication. The colloidal osmolality of tears is twentyfold less than that of the corneal stroma, which in turn is less than 1% of the total osmolality of an isotonic solution, i.e. the magnitude of the colloidal osmolality is only a few hundreths of a per cent of total osmolality. This may be the reason why its role was thought to be unimportant by many researchers. Despite its relatively small magnitude when compared to total osmotic pressure, the oncotic pressure has been shown to play a major role in the maintenance of the water balance of bodily tissues and has been used as a diagnostic parameter in alveolar edema. The same principle has been used to formulate a collyrium, Dehydrex, or dextran-containing storage media for excised corneas such as the Kaufman-McCarey medium that have a colloidal osmolality at least equal to that of deturgescent corneal stroma. Such formulations are able to dehydrate corneal stroma even in the total absence of epithelium. Dehydrex has been shown to have a beneficial effect on damaged epithelium and is thought to be the drug of choice for the treatment of recurrent epithelial erosion when other treatment modalities have failed. In the present study, the total osmolality and the oncotic pressure of several artificial tear preparations presently marketed was determined and compared with the oncotic pressure of tears and the corneal stroma. We have found that the oncotic pressure of HypoTears is nearly sixty times higher than that of the leading artificial tear, thus it is comparable to the oncotic pressure of Dehydrex. We believe that the favorable patient acceptance of HypoTears is more likely due to this unusually high oncotic pressure than to its hypoosmolality. Such an artificial tear formulation should be effective in ameliorating microcystic epithelial edema and in increasing impaired epithelial adhesion to the underlying tissue in the cornea.