Co-delivery of paclitaxel and α-tocopherol succinate by novel chitosan-based polymeric micelles for improving micellar stability and efficacious combination therapy

The aim of this study was to develop chitosan derivative polymeric micelles for co-delivery of paclitaxel (PTX) and α-tocopherol succinate (α-TS) to the cancer cells to improve the therapeutic efficiency and reduce side effects of PTX. In this study, amphiphilic tocopheryl succinate-grafted chitosan oligosaccharide was synthesized and physically loaded by PTX and α-TS with entrapment efficiency of 67.9% and 73.2%, respectively. Physical incorporation of α-TS into the micelles increased the hydrophobic interaction between PTX and the micelles core, which improved micelle stability, reduced the micelle size and also sustained the PTX release from the micelles. The mean particle size and zeta potential of αTS/PTX-loaded micelles were about 133?nm and +25.2?mV, respectively, and PTX release was completed during 6–9?d from the micelles. Furthermore, the cytotoxicity of α-TS/PTX-loaded micelles against human ovarian cancer cell line cancer cell in vitro was higher than that of PTX-loaded micelles and the free drug solution. Half maximal inhibitory concentration values of PTX after 48-h exposure of the cells to the PTX-loaded micelles modified and unmodified with α-TS were 110 and 188?ng/ml, respectively.     

Semi-automatic measurement of rigid gas-permeable contact lens movement in keratoconus patients using blinking images

Purpose

To introduce a method for estimation of the rigid gas-permeable contact lens (RGP) movement.

On the mechanical behavior of a functionally graded micro-beam subjected to a thermal moment and nonlinear electrostatic pressure

In the present work, mechanical behavior of a functionally graded cantilever micro-beam subjected to a nonlinear electrostatic pressure and temperature changes has been studied. It has been assumed that the top surface is made of pure metal and the bottom surface from a metal–ceramic mixture. The ceramic constituent percent of the bottom surface varies from 0% to 100%. In addition to the Volume Fractional Rule of material, exponential function has been used for representation of continuous gradation of the material properties through micro-beam thickness. Attention being paid to the ceramic constituent percent of the bottom surface, five different types of FGM micro-beams have been investigated. Nonlinear integro-differential thermo-electro mechanical equation based on Euler–Bernoulli beam theory has been derived and solved using Step-by-Step Linearization Method and Finite Difference Method. The effects of temperature changes and the electrostatic pressure on the deflection and stability of FGM micro-beams having various amounts of the ceramic constituent have been studied and normal stress distributions in the cross section along the beam thickness have been given and compared with a classic metal beam.     

Nonlinear behavior of capacitive micro-beams based on strain gradient theory

This paper studies the size dependent behavior of materials in MEMS structures. This behavior becomes noticeable for a structure when the characteristic size such as thickness or diameter is close to its internal length-scale parameter and is insignificant for the high ratio of the characteristic size to the length-scale parameter, which is the case of the silicon base micro-beams. However, in some types of micro-beams like gold or nickel bases, the size dependent effect cannot be overlooked. In such cases, ignoring this behavior in modeling will lead to incorrect results. Some previous researchers have applied classic beam theory on their models and imposed a considerable hypothetical value of residual stress to match their theoretical results with the experimental ones. The equilibrium positions or fixed points of the gold and nickel micro-beams are obtained and shown that for a given DC voltage, there is a considerable difference between the obtained fixed points using classic beam theory, modified couple stress theory, and modified strain gradient theory. In addition, it is shown that the calculated static and dynamic pull-in voltages using higher order theories are much closer to the experimental results and are higher several times than those obtained by classic beam theory.     

Damage induced in p-GaAs due to RIE in CH/sub 4//H/sub 2/ mixture

Damaged induced in p-GaAs due to RIE in pure H/sub 2/ and a mixture of CH/sub 4//H/sub 2/ has been investigated by I-V and C-V measurements on Au/p-GaAs Schottky diodes fabricated following the RIE process. The ideality factor, barrier height, depletion width and carrier concentration of the etched samples were compared with those of a control sample. Considerable eradication of induced damage was observed for the sample which was etched in CH/sub 4//H/sub 2/ mixture and was annealed prior to diode fabrication.<>     

The Application of Surface Response Methodology to the Pretreatment of WC Substrates Prior to Diamond Coating

High cobalt (Co) content greater than 10% in tungsten carbide is desirable because Co improves the toughness of the cutting tool. However, the additional Co poses a huge challenge in surface preparation given that the Co content must be reduced to less than 1% on the substrate surface prior to applying a diamond coating. The excessive presence of Co on the substrate surface during coating suppresses diamond nucleation and causes the deterioration of diamond film adhesion. Many attempts have been made to overcome this issue, including the use of chemical etching, mechanical blasting, and heat treatment, but the successful pretreatment of WC-12%Co is still very limited. In this paper, a single-step chemical pretreatment using a mixture of sulfuric acid and hydrogen peroxide solutions was carried out on WC-12%Co. Two independent variables, i.e., etching time and acid temperature, were varied in the experiments to reduce Co contents as well as to roughen the substrate surface. The experimental plan was based on a central composite design. Variance analysis was employed to verify the precision of the mathematical models and their relative parameters. The predicted models generated by the response surface methodology (RSM) were compared with the experimental results, and close agreement was observed. The models demonstrated the significance of both factors, namely, acid temperature and etching time, in reducing Co contents to less than 1% as well as a roughening of the substrate surface within the desirable range.     

Mechanical and structural properties of polylactide/chitosan scaffolds reinforced with nano-calcium phosphate

In this study, chitosan/polylactide scaffolds reinforced with nano-calcium phosphate (average crystallite size of 16.5?nm) (CP) were fabricated to create a material with excellent properties for bone tissue engineering applications via freeze-casting method. The structural and mechanical properties of nanocomposite scaffolds were studied by increasing amount of chitosan/poly lactide ratio and nano-CP content in both dry and hydrate states, which reflected the exact status of scaffolds in a real biomechanical environment. The morphologies of the nanocomposite scaffolds were viewed using scanning electron microscopy (SEM) and all the scaffolds exhibited a high porosity (up to 92?%) with open pores of 38?C387???m average diameters, which decreased with increased chitosan/polylactide ratio and nano-CP content. Also, SEM photograph of the cross-sectional area of the scaffold showed nano-CP was dispersed all over the polymer matrix thoroughly. The results of mechanical tests showed that the compressive modulus (E) and compressive stress (??) enhanced, when chitosan and nano-CP increased. X-ray diffraction analysis indicated typical chitosan, polylactic acid and nano-CP peaks and showed that the increase in nano-CP weight percentage increased its peak intensities. In addition, the effect of pore-size distributions of the scaffolds with the same composition was studied in relation to mechanical properties. The results showed substantial differences in the pore-size distributions of scaffolds with the same composition prepared, which have no effect on their dry states.     

Nitrogen mineralization in two calcareous soils treated with raw organic amendments

This study examined the mineralization of nitrogen (N) in two calcareous soils (sandy loam and clay soil) treated with the main types of raw amendments, using a laboratory incubation procedure over 40 weeks. At the end of the incubation time, mineralized N in treated soils ranged from 165 to 1,005 mg kg^?1 with sandy loam and from 85 to 1,105 mg kg^?1 with clay soil. The results indicated that poultry manure induced the highest level of N mineralization. In general, the doses of amendments that were applied appeared to present an environment risk of nitrate ( $ {{\text{NO}}_{3}}^{ - } $ -N) leaching, with the exception of the municipal waste compost. In contrast, N immobilization occurred in the two soils amended with wheat and sunflower residues. The N availability characteristics of wheat and sunflower indicated that the accumulation of large concentrations of $ {{\text{NO}}_{3}}^{ - } $ -N in soil was unlikely to arise from the agricultural use of these materials. The amount of N released from other amendments was high, which indicates that application rates should be reduced, or alternative amendments used, so as to minimize leaching losses in regions where groundwater quality is of concern. The amendments were ranked based on the inorganic N they supplied in the following order: poultry manure > sewage sludge > potato > sheep manure > municipal waste compost. Simple exponential and power models were fitted to all experimental data. These models can be used in describing N mineralization, predicting the amounts of N mineralized over time and in reducing N leaching.     

Evidence that iron-overload promotes 7,12-dimethylbenz(a)anthracene- induced skin tumorigenesis in mice

Iron overload is known to occur in West European and American populations due to the consumption of an iron-rich diet. There are also genetic disorders which lead to body iron overload. It has been shown that iron overload predisposes humans to an increased risk of cancer. In experimental animals, iron overload is known to enhance intestinal, colon, hepatic, pulmonary and mammary carcinogenesis. However, the mechanism by which iron overload enhances chemically-induced carcinogenesis is not known. In this study, we show that iron overload acts as a mild tumor promoter in mouse skin. Female albino swiss mice were given 1 mg iron/mouse parenterally for 2 weeks to induce iron overload. These animals showed a three-fold increase in cutaneous iron concentration as compared to normal mice. Tumors were initiated by topically applying 7,12-dimethylbenz(a)anthracene (DMBA). Appearance of the first tumor (latency period), percent tumor incidence and number of tumors/mouse were recorded. When compared to the control group, iron overload mice showed an increased incidence of tumors, from 25%-55% by week 20, and tumors appeared 4 weeks earlier. The number of tumors per mouse was four-fold higher in the iron overload group. The induction of cutaneous ornithine decarboxylase (ODC) activity and [3H]thymidine incorporation in cutaneous DNA were higher in iron overload groups as compared to normal control animals. Similar to other oxidant tumor promoters, iron overload enhanced cutaneous lipid peroxidation and xanthine oxidase activity and decreased catalase activity. Our results indicate that iron overload exerts a mild tumor promoting activity in mouse skin. Our data also show that oxidative stress generated by iron overload plays an important role in the augmentation of cutaneous tumorigenesis. These data may also have implications for the enhanced risk of cancer-induction following UVB exposure of human populations with iron overload.     

User preferences for adaptive user interfaces in health information systems

An adaptive user interface requires identification of user requirements. Interface designers and engineers must understand end-user interaction with the system to improve user interface design. A combination of interviews and observations is applied for user requirement analysis in health information systems (HIS). Then, user preferences are categorized in this paper as either data entry, language and vocabulary, information presentation, or help, warning and feedback. The user preferences in these categories were evaluated using the focus group method. Focus group sessions with different types of HIS users comprising medical staff (with and without computer skills) and system administrators identified each user group’s preference for the initial adaptation of the HIS user interface. User needs and requirements must be identified to adapt the interface to users during data entry into the system. System designers must understand user interactions with the system to identify their needs and preferences. Without this, interface design cannot be adapted to users and users will not be comfortable using the system and eventually abandon its use.