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OBJECTIVES: Moringa oleifera is an edible tropical plant with the potential to alleviate micronutrient deficiencies in low and middle income nations. This study addresses two barriers for the consumption of M. oleifera leaves: (1) inconsistencies between the actual nutritional value and common nutritional claims and (2) its bitterness. It was hypothesized that the reduction of bitterness in M. oleifera-fortified foods would increase their acceptability. METHODS: The micronutrient content of M. oleifera leaves from India and Nigeria was determined in this study and compiled along with literature values. Data on M. oleifera were compared against spinach and carrot for minerals and carotenoids respectively. The effectiveness of acid soaking and addition of sweetness (aspartame) as debittering treatments was examined using a full factorial design. A sensory evaluation (randomized complete block, 9-point hedonic scale) with 50 assessors examined the preference and bitterness in 7 fortified instant soup mix formulations with varying levels of debittered M. oleifera leaf powder. RESULTS: Results of this study do not support nutritional claims asserting that M. oleifera contains 25 times more iron than spinach and 10 times more vitamin A than carrots. M. oleifera contains, at most, 3.4 times more iron than dried spinach. The equivalent vitamin A content in M. oleifera was found to be 55% lower than that in dried carrots. These inconsistencies may be a result of nutritional comparisons made between inequivalent moisture contents, as dried M. oleifera leaves have 18 times more iron than fresh spinach by weight. The control (no fortification) formulation was most preferred, followed by formulations with 50% replacement by M. oleifera. The addition of sweetness significantly reduced bitterness and increased acceptance of fortified soup mix formulations. CONCLUSIONS: M. oleifera's nutritional content is lower than that asserted by common nutritional claims, but its abundance in food insecure regions and wide range of nutrients maintain its potential as a nutritious food source for populations low and middle income nations. It is recommended that M. oleifera-fortified food products include a sweet excipient to reduce bitterness to increase acceptability. FUNDING SOURCES: This research was funded by the Centre for Global Engineering (University of Toronto) and Mitacs Canada. SUPPORTING TABLES, IMAGES AND/OR GRAPHS

Polydimethylsiloxane-poly(methacrylic acid—hydroxyethyl methacrylate) interpenetrating polymer networks (PDMS-P(MAA–HEMA) IPN) were formulated and polymerized simultaneously from bicontinuous microemulsion templates. Microemulsions containing reactive silicone oils and MAA/HEMA in aqueous solution were stabilized with silicone surfactants, and were then reacted at 50 °C for 3 h under an N2 atmosphere. The formation of bicontinuous morphology was confirmed by laser scanning confocal microscopy, reversible swelling behavior, differential scanning calorimetry, texture analysis, and permeability to vitamin B12 in aqueous solution. Incorporating polymerizable surfactants into the microemulsion aided in stabilizing the initial microemulsion structure during polymerization, yielding a more uniform IPN morphology with domain sizes of

In this work, for the first time, the Hydrophilic-Lipophilic Difference (HLD) framework for microemulsion formulation has been applied to silicone oils and silicone alkyl polyether surfactants. Based on the HLD equations and recently introduced mixing rules, we have quantified the hydrophobicity of the oils according to the equivalent alkane carbon number (EACN). We have found that, in a reference system containing sodium dihexyl sulfosuccinate (SDHS) as the surfactant, 0.65 centistoke (cSt) and 3.0 cSt silicone oils behave like n-dodecane and n-pentadecane, respectively. Silicone alkyl polyether surfactants were found to have characteristic curvatures ranging 3.4-18.9, exceeding that of most non-ionic surfactants. The introduction of methacrylic acid (MAA) and hydroxyethyl methacrylate (HEMA) to the aqueous phase caused a significant negative shift in HLD, indicative of an aqueous phase that is less hydrophilic than pure water. The more hydrophobic surfactants (largest positive curvatures) were used in order to compensate for this effect. These findings have led to the formulation of bicontinuous microemulsions (μEs) containing silicone oil, silicone alkyl polyether and reactive monomers in aqueous solution. Ternary phase diagrams of these systems revealed the potential for silicone-containing polymer composites with bicontinuous morphologies. These findings have also helped to explain the phase behavior of formulations previously reported in literature, and could help in providing a systematic, consistent approach to future silicone oil based microemulsion formulation.

Quartz crystal microbalance (QCM) was used to study the self-assembly of per-6-thio-β-cyclodextrin (t7-βCD) on gold surfaces, and the subsequent inclusion interactions of immobilized βCD with adamantane-poly(ethylene glycol) (5,000 MW, AD-PEG), 1-adamantanecarboxylic acid (AD-C) and 1-adamantylamine (AD-A). From a 50 μM solution of t7-βCD in 60:40 DMSO:H2O, a t7-βCD layer was formed on gold with surface density of 71.7 ± 2.7 pmol/cm2, corresponding to 80 ± 3% of close-packed monolayer coverage. Gold sensors with immobilized t7-βCD were then exposed alternately to six different concentrations of AD-PEG, 500 μM AD-C or 500 μM AD-A aqueous solutions for association, and water for dissociation. Association of AD-PEG conformed to a Langmuir isotherm, with a best fit equilibrium constant K = 125,000 ± 18,000 M−1. For AD-C and AD-A, association (k a ) and dissociation (k d ) rate constants were extracted from kinetic profiles by fitting to the Langmuir model, and equilibrium constants were calculated. The parameters for AD-C were found to be: k a = 100 ± 5 M−1 s−1, k d = 110 (±18) × 10−4 s−1, and K = 9,400 ± 1,700 M−1. For AD-A, k a = 58 ± 6 M−1 s−1, k d = 154 (±7) × 10−4 s−1, and K = 3,800 ± 400 M−1. The results demonstrate the utility of QCM as a tool for studying small molecule surface adsorption and guest–host interactions on surfaces. More specifically, the kinetic and thermodynamic data of AD-C, AD-A, and AD-PEG inclusion with immobilized t7-βCD form a basis for further surface association studies of AD-X conjugates to advance surface sensory and coupling applications.

In this study, the silica-based organic-inorganic hybrid nanocomposites have been developed for applications as the hard coating on the PET substrate surface. The inorganic material was functional polysiloxane with polyheral oligomeric silsesquioxanes (POSS)-like nanostructures, prepared by sol-gel method using 3-(Methacryloyloxy)-propyltrimethoxysilane (MAPTMS) in the presence of an acidic catalyst. The polymer matrix used was the UV-curing polyurethane acrylate resin. The surface functional groups and the sizes of nanoparticles were controlled to ensure strong interaction between the nanoparticles and the polymer matrix, resulting in high transparency and abrasion-resistant nanocomposite coatings, as the organic-inorganic nanocomposite coatings exhibit great performance in hardness and visible light transmittance on the PET substrate. With good optical, mechanical and physical performance, the multifunctional transparent nanocomposite coatings are suitable for the applications in automotive, optoelectronics and electronics industries, etc.

We report the encapsulation of MIN6 cells, a pancreatic β-cell line, using thermally induced gelable materials. This strategy uses aqueous solvent and mild temperatures during encapsulation, thereby minimizing adverse effects on cell function and viability. Using a 2:1 mixture of PNIPAAm-PEG-PNIPAAm tri-block copolymer and PNIPAAm homopolymer that exhibit reversible sol-to-gel transition at ∼30°C, gels were formed that exhibit mechanical integrity, and are stable in H2O, PBS and complete DMEM with negligible mass loss at 37°C for 60 days. MTT assays showed undetectable cytotoxicity of the polymers towards MIN6 cells. A simple microencapsulation process was developed using vertical co-extrusion and a 37°C capsule collection bath containing a paraffin layer above DMEM. Spherical capsules with diameters ranging from 500 to 900 µm were formed. SEM images of freeze-dried capsules with PBS as the core solution showed homogenous gel capsule membranes. Confocal microscopy revealed that the encapsulated cells tended to form small aggregates over 5 days, and staining for live and dead cells showed high viability post-encapsulation. A static glucose challenge with day-5 cultured microencapsulated cells exhibited glucose-dependent insulin secretion comparable to controls of free MIN6 cells grown in monolayers. These results demonstrate the potential use of these thermo-responsive polymers as cell encapsulation membranes. Biotechnol. Bioeng. 2007;96: 146–155. © 2006 Wiley Periodicals, Inc.

The objectives of this study are to probe the pH responsiveness of polydimethyl siloxane (PDMS)/polymethacrylic acid (PMAA) interpenetrating polymer networks (IPNs), and to relate pH-dependent changes in permeation to morphological changes. PDMS/PMAA IPNs of 70:30 mass ratio on a dry basis were prepared using a monomer immersion method [Macromolecules 33 (10) (2000) 3714]. IPNs made by this method have previously been shown to exhibit a bicontinuous morphology at pH 7 with PMAA structural features of 10–200 nm in dimension [Macromolecules 36 (6) (2003) 1962]. Equilibrium hydration, morphology and diffusion characteristics of the IPNs were investigated at different pH. Equilibrium hydration was gravimetrically determined to be in the range of 0.77–0.9 at pH 7 and 0.42–0.5 at pH 3, corresponding to average hydrations of 0.93 and 0.74 of the PMAA component, respectively. Morphology imaged using laser scanning confocal microscopy (LSCM) showed that the area fraction of fluorescein isothiocyanate labelled dextran (FITC-dextran) accessible regions decreased from pH 7 to 3, consistent with hydration data. Additionally at pH 3, the hydrogel domain appeared to be disconnected. Vitamin B12 (VB12) permeability through the IPN was found to be 1.7 × 10−7 cm2/s at pH 7, and below detection (

We report the development of a new gelation mechanism and a new family of polymers that self-assembles to form gels in a thermoreversible fashion. The polymers are block or star copolymers with a central hydrophilic poly(ethylene glycol) (PEG) segment (A) and temperature responsive poly(N-isopropylacrylamide) (PNIPAAm) terminal segments (B). Copolymers of various architectures, AB, A(B)2, A(B)4, and A(B)8, were synthesized to investigate the structures and properties relationship. At 5 °C, the viscosities of 20 wt % solutions were between 700 and 950 cP, and they could be easily injected through a 25 G needle. Upon warming to body temperature, A(B)2, A(B)4, and A(B)8 formed a strong associative network gel with aggregates of PNIPAAm segments acting as physical cross-links, whereas AB formed a weaker gel by micellar packing and entanglement. The values of elastic modulus, loss tangent, and yield strength were 1000−2500 Pa, 0.24−0.62, and 200−860 Pa, respectively. The gelation kinetic was fast; a typical ge...

A monomer immersion sequential method for preparing PDMS−PMAA interpenetrating polymer networks (IPNs) was developed. Immersion of pre-IPN films in the guest monomer throughout synthesis ensured an even monomer concentration profile and produced a uniform bicontinuous morphology throughout the IPN indicative of phase separation by spinodal decomposition. Such IPNs were permeable to water-soluble compounds. Laser scanning confocal microscopy (LSCM) of the swollen IPNs allowed direct visualization of the morphology. PDMS−PMAA sequential IPNs synthesized while in contact with surfaces were also examined. Contact with glass or air during synthesis resulted in spatially varying morphology ranging from dispersed hydrogel domains near the surface to a bicontinuous morphology some distance below the surface. The morphology spectrum was attributed to a monomer concentration gradient created by monomer evaporation during handling of the pre-IPN film, as well as to substrate-dependent surface thermodynamic effects. ...

Grafting a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), onto porous polyethylene (PE) membranes by UV irradiation was investigated. A wide range of graft yields (5–449%) was achieved by varying irradiation time (20–240 min) and monomer concentration (1.2–3.6 wt %). Characterization by XPS and SEM shows that the graft polymers are located both on the external surfaces as well as inside the pores of the membranes. Diffusional permeation experiments show that two distinct types of temperature responses were observed, depending on the graft yield; permeability increases with temperature in low graft yield membranes, while permeability decreases with temperature in high graft yield membranes. A mechanism explaining the dual valve functions of the graft membrane is proposed based on the location of the graft polymers on the membrane. It was also observed the permeability response exhibits a maximum with permeant molecular weight. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2133–2142, 1998

The exact analytical solution and an approximate solution based on the variational formulation method have been obtained for the release kinetics of a solute from a spherical polymeric matrix in which the initial solute loading A is above the solubility limit Cs. Comparisons between these new solutions and previously reported approximate solutions based on either pseudo-steady state assumptions or the refined integral method indicate that the approximate solutions are very accurate when ACs is much larger than unity. However, as drug loading decreases, deviations between the approximate solutions and the exact solution increase so that the approximate solutions are least accurate in the limit ACs → 1.

50:50 Poly(d/-lactide-co-glycolide) (50:50 PLGA) was used to investigate the effects of polymer degradation on drug release from bulk degradable polymers. 5-Fluorouracil (5-FU) and Cyclosporin A (CyA) were used as model drugs. Using scanning electron microscopy, it was observed that initially non-porous 50:50 PLGA underwent significant morphological changes, becoming increasingly porous, as degradation proceeded. Concomitant increases in the transport parameters permeability and diffusivity of the model drugs through degrading 50:50 PLGA membranes were observed. Sharp transitions were observed in the relationship between the transport parameters and the residual polymer molecular weight and porosity—at values of molecular weight and porosity of about 5000–6000, and 70–80°, respectively. These transitions suggest that a shift in transport mechanism occurs with polymer degradation: the initial dominant transport pathway through degrading PLGA is the dense polymer phase, but as degradation progresses, the increase in porosity results in an increasingly connected pore structure such that, at some point in time, the pore network becomes the dominant pathway. By comparing experimentally measured 5-FU release profiles from PLGA matrices with release profiles calculated from experimentally measured permeability through degrading PLGA membranes containing no drug, it was shown that the shift in transport mechanism is the likely cause for the onset of the rapid final release stage of typical tri-modal release profiles from bulk-degradable polymer matrices.

The fortification of salt with iron may greatly reduce the prevalence of iron deficiency globally, but fortification is complicated by iron-iodine interactions. To minimize this interaction, a spray dry microencapsulation system was developed. This study evaluates the creation and use of this system, producing engineered iron premixes for integration into coarse iodized salt. Bioavailable ferrous fumarate powders were encapsulated via spray-drying to produce particles which are too small to be detected visually (

Side chain liquid crystalline polysiloxane was synthesized and the effects of the DC electric field strength and the AC electric field frequency of an applied transmembrane field on membrane permeability were investigated. In this paper, the synthesis method of poly(methyl p-propyloxyphenyl, p-methoxy benzoate siloxane) and permeation data of p-aminoacetophenone through this polymer at 5°C are presented. Membrane permeability was observed to increase with increasing field strength and decrease with increasing frequency. Utilizing DC electric field, 28-fold increase in membrane permeability was obtained with a field strength of 4,200 V/cm. At a field strength of 4,900 V/cm, a 26-fold range in permeation rate was obtained between 0.001 Hz and 10 KHz. The response times required to achieve new steady state fluxes after changing frequency at 4,900 V/cm were observed to be nearly instantaneous in contrast to those observed on changing the DC electric field strength.

OBJECTIVE: To develop a temperature-responsive polymer membrane that is permeable to drug only at temperatures above 42oC. A triggerable implant that releases drug only when heated can be made by encapsulating a drug reservoir with such a thermoresponsive membrane. Such an implant can be applied in clinical situations in which it is desirable to release drug only on demand, such as erectile dysfunction. METHODS: A porous polyethylene (PE) membrane was modified by fillings its pores with either docosane or a docosane:eicosane mixture. The melting transition of the alkanes corresponds to a diffusional switch, thus, the alkane melting point corresponds to the membrane release trigger temperature. The onset of melting for each alkane and the alkane mixture was measured by differential scanning calorimetry. Using a diffusion cell, the permeability of propranolol hydrochloride (PRO) through the thermoresponsive membrane was measured. RESULTS: PRO permeation through the docosane-absorbed PE membrane at 37oC and 45oC was reversible, and was reproducible after five cycles of temperature oscillation. From an aqueous solution reservoir, the ratio of PRO permeability through the docosane-absorbed PE membrane at 45oC versus 37oC was 378±65. Similarly, the ratio of PRO permeability through the docosane:eicosane (90:10) PE membrane at 42.5oC and at 37oC was 235±56. CONCLUSIONS: The high on/off permeability ratio achieved with PRO provides promise for the development of a thermoresponsive implant by using this membrane and a suitable drug. Local heating of the implant may be achieved by external power sources such as ultrasonic or microwave heaters.

Three of the five hypervariable domains (V1-V3) of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 have previously been shown to be dispensable for antigenic epitopes recognized by broadly neutralizing monoclonal antibodies. In this study, the influence of the V4 and V5 domains on an epitope recognized by a broadly neutralizing human monoclonal antibody, 1.5e, was investigated. In contrast with the V1, V2, and V3 domains of gp120, the V4 and V5 domains were found to be critical for binding to both CD4 and 1.5e. Our results suggest that V4 and V5 are in structurally less flexible regions of gp120 than V1, V2, and V3 and raises the question of whether variable domains V4 and V5 are also indispensable for other broadly neutralizing antibodies in the same class as 1.5e.

Human monoclonal antibody 2.3a was previously shown to enhance human immunodeficiency virus type 1 (HIV-1) infection in vitro. This enhancing antibody recognizes a conserved epitope of envelope glycoprotein gp120. We report here that binding of the 2.3a antibody to gp120 is significantly affected by deletions of certain N- or C-terminal residues of gp120. However, not all such deletions affect the epitope recognized by a broadly neutralizing human monoclonal antibody, 1.5e. These findings suggest the feasibility of designing a gp120 antigen that is free of 2.3a epitope while retaining the conformation of the 1.5e epitope.

Total internal reflection fluorescence (TIRF) is a technique that may be used to examine the interaction of macromolecules with solid surfaces. In this report, a TIRF apparatus and its application to the adsorption of proteins from flowing solutions on polymer films are described. Bovine serum albumin (BSA)/crosslinked polydimethylsiloxane (silicone rubber) is the protein/surface pair considered herein. To relate TIRF fluorescence signals to actual surface concentrations, a calibration technique using BSA labeled with both tritium and fluorescein isothiocyanate (FITC) was developed. Unambiguous calibration results require a linear relationship between observed fluorescence intensity and protein surface concentration, reproducible evanescent field intensities, and constant fluorescence quantum efficiencies. The contribution of bulk solution fluorescence to the total TIRF signal must be ascertained to ensure accurate quantitative interpretation of TIRF data. There are two sources of solution fluorescence: one arising from excitation of fluorescent solution protein by scattered light, the second from solution protein within the evanescent field. Solution protein within the evanescent field is distinguished from reversibly adsorbed proteins by comparing its exchange dynamics with that of nonadsorbing FITC-dextran together with the predictions of a hydrodynamic model. By removing the solution protein contributions to the total TIRF signal, surface-adsorbed protein fluorescence, and thus the amount of protein adsorbed, can be obtained. Bulk solution contribution to the total TIRF signal increases with solution concentration. Experiments were conducted at solution concentrations of 2 and 200 mg%, both corresponding to an equilibrium surface concentration of 0.14 μg/cm 2 , the saturated surface concentrations for BSA adsorbing on silicone rubber. Proteins in the 2 mg% solution contributed negligibly to the total fluorescence, while fluorescence from the 200 mg% solution constituted a significant fraction of the total TIRF signal.

Total internal reflection fluorescence is used to examine the initial adsorption, desorption, and exchange kinetics of the protein bovine serum albumin (BSA) on six polymer surfaces with widely varying surface properties and functionalities. The six surfaces studied are polydimethylsiloxane (PDMS), polydiphenylsiloxane (PDϕS), polycyanopropylmethylsiloxane (PCPMS), polymethyl methacrylate (PMMA), polystyrene sulfonate (PSS), and polyethylene oxide (PEO). The results show that the initial adsorption of BSA on the surfaces PDMS, PDϕS, and PCPMS is diffusion limited up to wall shear rates of 4000 s −1 . The initial adsorption of BSA on PSS is diffusion limited at shear rates below about 70 s −1 but becomes kinetically controlled at higher shear rates. BSA adsorption on PMMA is kinetically controlled, and the adsorption of BSA on PEO is too slow to be detected under the conditions used. Studies on the kinetically limited BSA adsorption onto PMMA show that the adsorption process can be described by a kinetic rate expression that is first order in protein concentration. The initial desorption of BSA adsorbed onto each surface (except PEO) is shown to be kinetically limited. The rate-limiting step for the exchange of BSA adsorbed onto PDMS is shown to be the desorption of adsorbed BSA.