Search

With the rapid development of the Internet and information technology, the problem of zero-trust networks has become increasingly prominent, and secure multi-party computation has become a research hotspot to solve the problem of zero-trust networks. The secure judgment of point and line relationship is an important research branch of secure computing set geometry. However, most of resent secure computing protocols of point and line relationship are designed in the semi-honest model and cannot resist malicious attacks. Therefore, this paper analyzes the possible malicious adversary behaviors and designs a secure protocol in the malicious model. In this paper, the Paillier cryptosystem, zero- knowledge proof, and cut-choose method are used to resist malicious behavior, and the real/ideal model paradigm method is used to prove the security of the protocol. Compared with the existing solutions, the malicious model protocol is still efficient and widely used in real applications. &nbsp

Nanoscale zerovalent iron (Fe0) on carbon materials was successfully synthesized via a simple one-step pyrolysis of coir pith with iron precursor. The Fe0 dispersion over activated carbon (AC) and stability was amended by adding polyethylene glycol (PEG)/carboxymethyl cellulose (CMC). The transmission electron microscopy results reveal the homogeneous distribution of Fe0 (~20 nm) on the surface of AC. In addition, the crystal patterns and valence states of Fe0 nanoparticles were evaluated by X-ray diffraction, and X-ray photoelectron spectroscopy, respectively. Trichloroethylene (TCE), one common pollutant in the groundwater, was used to understand the catalytic ability of Fe/AC. The pseudo-first-order kinetic model was applied for TCE removal rate. Fe/AC shows 80% TCE removal in 24 h reaction time, due to its porous structure and large surface area. PEG-Fe/AC composite demonstrated 90.4% TCE dechlorination efficiency in 45 min (kobs 0.29 min−1). The enhanced dechlorination was recorded due to perfect PEG and Fe0 ratio, in which PEG restricted the arial oxidation of Fe0. The as-synthesized nanocomposite was further evaluated for its high stability and efficacy by consecutive eight successive TCE removal cycles. This study demonstrates that one-pot synthesized PEG-Fe/AC composite can effectively remove chlorinated compounds in water, which can be beneficial to the future research applications.

Moringa oleifera (Lam.) is a nutritious plant species that has the potential to alleviate food insecurity in low- and middle-income regions. However, the bitter taste associated with M. oleifera leaves is a key barrier to its acceptance as food. It was hypothesized that reducing the bitterness in M. oleifera-fortified instant soups would increase their acceptance. Acid soaking and the addition of a sweetener (aspartame) were examined for their effectiveness in the removal of bitter taste in M. oleifera leaves. Fifty assessors rated the acceptance and perceived bitterness in a randomized complete block sensory evaluation. South Indian instant soup samples with 0%, 50% and 100% replacement of vegetable powder with M. oleifera leaf powder were evaluated. Acceptance for M. oleifera-fortified instant soups was higher for samples with lower perceived bitterness. Addition of sweetener was found to be effective in increasing the acceptability and reducing the perceived bitterness at the 50% replacement level, but not at the 100% replacement level. Perceived bitterness did not decrease in formulations with acid-soaked M. oleifera leaves. Undesirable organoleptic properties need to be masked or removed for the acceptance of M. oleifera leaves as a regular food. We recommend that foods fortified with M. oleifera to include a sweet excipient to reduce the bitter tastes. Fortified instant soup samples with reduced perceived bitterness had increased acceptability. Debittered M. oleifera-fortified foods would appeal to consumers, which would increase their consumption and could lead to reduced prevalence of micronutrient deficiencies.

Current ways of managing spent coffee grounds (SCGs) are uneconomical and have significant environmental impacts. Alternative approaches, such as hydrothermal carbonisation (HTC), which can utilise their rich organic matter for energy recovery purposes are essential. Here we present, a response surface methodology (RSM) for understanding the combined interactive effects due to the main HTC operating conditions, i.e. reaction temperature and residence time, as well as optimising them to produce hydrochar from SCGs of maximal yield and calorific value. The fuel properties and combustion behaviours of hydrochar were further evaluated to assess its suitability to replace coals for energy applications. Depending on the operating conditions, the atomic carbon content and calorific values of the hydrochar were significantly improved: by 11.2–30.7% and 15.8–44.7% respectively. The highest hydrochar calorific value recorded, 33.5 MJ kg−1, resembled that of anthracite and dry steam coal, generally used in the UK. At optimal conditions of ∼216 °C and 1hr - guided by the RSM - a maximal hydrochar yield of ∼64% and a calorific value of 31.6 MJ kg−1 are feasible. Using this as a benchmark, the 500,000 tonnes of SCGs generated annually in the UK has the potential of replacing 4.4% of the coal used for electricity generation in the country.

Background and Objective: Although developing countries have been receiving donations of medical equipment for many years, a number of studies have indicated that a high percentage of donated equipment is never put into use. [1,3,4] Many of the reasons for this can be traced back to inadequate donation practices on the part of donor organizations. The objective of this study was to gain an improved understanding of the practices and challenges associated with medical equipment donations by Canadian charitable organizations. Material and Methods: Forty-one organizations (registered and non-registered charities, non-governmental organizations (NGOs), non-profit organizations, medical clinics, and hospitals) completed an online survey, and 16 respondents were interviewed via telephone or in person. In addition, representatives from 28 hospitals in Ghana were interviewed in person to gain an understanding of the recipient experience. Results: We observed that for many Canadian donor organizations there is room for improvement in formalizing procedures, testing to verify equipment functionality before shipping, providing additional support for recipients in the form of manuals, spare parts and training, and long-term monitoring of donated items to measure effectiveness. For recipients, the most common challenges faced were lack of spare parts, and lack of operating or service manuals. Despite these challenges, all of the Ghanaian survey respondents said that donated medical equipment benefited their hospitals. Conclusion: We concluded that because of staffing limitations in smaller donor organizations, and in order to better meet the needs of recipients, it would be beneficial for Canadian organizations to communicate and collaborate with one another to share resources and expertise when planning donations overseas.

Background: Transnational funders provide up to 80% of funds for medical devices in resource-limited settings, yet sustained access to medical devices remains unachievable. The primary goal of this study was to identify what factors hinder access to medical devices through the perspectives of frontline public hospital staff in Ghana involved in the implementation of transnational funding initiatives. Methods: A case study was developed that involved an analysis of semi-structured interviews of 57 frontline technical, clinical and administrative public health care staff at 23 sites in Ghana between March and April 2017; a review of the national guidelines for donations; and images of abandoned medical devices. Results: Six key themes emerged, demonstrating how policy, collaboration, quality, lifetime operating costs, attitudes of health care workers and representational leadership influence access to medical devices. An in-depth assessment of these themes has led to the development of an enterprise-wide comprehensive acquisition and management framework for medical devices in the context of transnational funding initiatives. Conclusion: The findings in this study underscore the importance of incorporating frontline health care staff in developing solutions that are targeted at improving delivery of care. Sustained access to medical devices may be achieved in Ghana through the adoption of a rigorous and comprehensive approach to acquisition, management and technical leadership. Funders and public health policy makers may use the study’s findings to inform policy reform and to ensure that the efforts of transnational funders truly help to facilitate sustainable access to medical devices in Ghana.

Background\ud Oxygen reduces mortality from severe pneumonia and is a vital part of case management, but achieving reliable access to oxygen is challenging in low and middle-income country (LMIC) settings. We developed and field tested two oxygen supply solutions suitable for the realities of LMIC health facilities.\ud \ud Methods\ud A Health Needs Assessment identified a technology gap preventing reliable oxygen supplies in Gambian hospitals. We used simultaneous engineering to develop two solutions: a Mains-Power Storage (Mains-PS) system consisting of an oxygen concentrator and batteries connected to mains power, and a Solar-Power Storage (Solar-PS) system (with batteries charged by photovoltaic panels) and evaluated them in health facilities in The Gambia and Fiji to assess reliability, usability and costs.\ud \ud Results\ud The Mains-PS system delivered the specified ≥85% (±3%) oxygen concentration in 100% of 1-2 weekly measurements over 12 months, which was available to 100% of hypoxaemic patients, and 100% of users rated ease-of-use as at least ‘good’ (90% very good or excellent). The Solar-PS system delivered ≥85% ± 3%) oxygen concentration in 100% of 1-2 weekly measurements, was available to 100% of patients needing oxygen, and 100% of users rated ease-of-use at least very good.\ud \ud Costs for the systems (in US dollars) were: PS$9519, Solar-PS standard version $20 718. The of oxygen for a standardised 30-bed health facility using 1.7 million litres of oxygen per year was: for cylinders 3.2 cents (c)/L in The Gambia and 6.8 c/L in Fiji, for the PS system 1.2 c/L in both countries, and for the Solar-PS system 1.5 c/L in both countries.\ud \ud Conclusions\ud The oxygen systems developed and tested delivered high-quality, reliable, cost-efficient oxygen in LMIC contexts, and were easy to operate. Reliable oxygen supplies are achievable in LMIC health facilities like those in The Gambia and Fiji.

There is a growing interest in decentralized wastewater management (DWWM) as a potential alternative to centralized wastewater management (CWWM) in developing countries. However, the comparative cost of CWWM and DWWM is not well understood. In this study, the cost of cluster-type DWWM is simulated and compared to the cost of CWWM in Alibag, India. A three-step model is built to simulate a broad range of potential DWWM configurations with varying number and layout of cluster subsystems. The considered DWWM scheme consists of cluster subsystems, that each uses simplified sewer and DEWATS (Decentralized Wastewater Treatment Systems). We consider CWWM that uses conventional sewer and an activated sludge plant. The results show that the cost of DWWM can vary significantly with the number and layout of the comprising cluster subsystems. The cost of DWWM increased nonlinearly with increasing number of comprising clusters, mainly due to the loss in the economies of scale for DEWATS. For configurations with the same number of comprising cluster subsystems, the cost of DWWM varied by ±5% around the mean, depending on the layout of the cluster subsystems. In comparison to CWWM, DWWM was of lower cost than CWWM when configured with fewer than 16 clusters in Alibag, with significantly less operation and maintenance requirement, but with higher capital and land requirement for construction. The study demonstrates that cluster-type DWWM using simplified sewer and DEWATS may be a cost-competitive alternative to CWWM, when carefully configured to lower the cost.

Objectives To assess the association of neighborhood sanitation coverage with under-five childrens diarrheal morbidity and to evaluate its exposure-response relationship. Methods We used the Demographic and Health Surveys (DHS) of 29 developing countries in sub-Saharan Africa and South Asia conducted between 2010 and 2014. The primary outcome was 2-week incidence of diarrhea in children under 5 years of age (N=300426). We conducted three-level logistic regression analyses and applied cubic splines to assess the trend between neighborhood-level coverage of improved household sanitation and diarrheal morbidity. Results Asignificant association between neighborhood-level coverage of improved household sanitation and diarrheal morbidity (OR[95%CI] = 0.68[0.62-0.76]) was found. Exposure-relationship analyses results showed improved sanitation coverage threshold at 0.6. We found marginal degree of association (OR[95%CI]=0.82[0.77-0.87]) below the threshold which beyond the threshold sharply increased to OR of 0.44 (95%CI:0.29-0.67) at sanitation coverage of 1 (i.e. neighborhood-wide use of improved household sanitation). Similar exposure-response trends were identified for urban and rural subgroups. Conclusions Our findings suggest that neighborhood sanitation plays a key role in reducing diarrheal diseases and that increase in sanitation coverage may only have minimal impact on diarrheal illness unless sufficiently high coverage is achieved.

This study examined the potential bio-oil production from the smouldering combustion of faeces mixed with sand, through a series of experiments. Surrogate faeces, with demonstrated equivalence to human faeces, were used in order to minimize variability in the composition. The yield of bio-oil was studied as a function of the following experimental parameters: original moisture content of the faeces, airflow rate and sand-to-faeces mass ratio. The amount of bio-oil collected was shown to be dependent on the airflow rate and the relative amount of sand used but independent on the moisture content. The bio-oil obtained was characterized by ultimate analysis, water content and calorific value. Under the experimental conditions studied, up to 70 g of bio-oil per kg of dry faeces (HHV = 27.6 kJ/g) can be produced. Finally, experiments demonstrated that sand can be reused after each experiment. The effect of the ash accumulation in the sand matrix on smouldering was investigated over five successive tests with the same batch of sand. The implementation of this technology to other type of organic waste would contribute to the development of an integrated waste treatment technology, in combination with bio-oil production.

Poor sanitation results in increased spread of diseases and environmental pollution. In many parts of the globe, treatment of feces needs an urgent solution that ensures elimination of pathogens using minimal resources. Self-sustaining smoldering combustion of feces mixed with sand has been has been recently studied as a potential technology. A combination of different experimental parameters is essential to ensure robust operation, where oxidation coexists with pyrolysis and water evaporation. This work presents the results of a series of thirty-two experiments conducted in order to study the sensitivity of the process to the following experimental parameters: moisture content, sand-to-feces ratio, airflow, sand grain size and ignition temperature. It was found that smoldering temperature and velocity are independent on the moisture content and ignition temperature; while are strongly dependent on other parameters, specially the airflow. The information presented is crucial to control the process...

The poor management of human excreta in developing countries is among the most prominent global issues due to its negative impact on public health. This work demonstrates for the first time that self-sustaining smouldering of faeces mixed with sand is a feasible alternative to incineration for rapid destruction of waste. Self-sustaining smouldering requires minimal energy input and pre-drying of faeces compared to incineration. This process ensures the elimination of biological hazards via long residence times (>20 min) at high temperatures (>400 °C). Surrogate faeces which exhibits similar energetic, thermal, and mechanical properties to real faeces are used in this study. The parameters controlling the combustion process including moisture content, airflow rate, and sand-to-faeces ratio are mapped to establish the range of conditions where self-sustaining smouldering of faeces can be achieved. Experiments were conducted within the ranges 0–75% for moisture content, 7–108 g/min for airflow rate and 2.75–11.9 g/g for sand-to-faeces (wet basis) ratio. Preliminary validation of the parameter space is done using real dog faeces. In this work, the parameter space defining the range of conditions where self-sustaining smouldering occurs is mapped. Results show successful self-sustaining smouldering of faeces for moisture contents of up to 60%, airflow ranging from 10 to 100 g/min, and wet sand-to-faeces ratio greater than 3.25. This proof-of-concept for a smouldering reactor to treat human solid waste demonstrates that smouldering of faeces could be the basis for a new, energy efficient waste treatment approach.

Oxygen is an essential medicine for the treatment of pneumonia, the leading cause of death in children under five worldwide. Yet, providing a sufficient and reliable supply of oxygen is a major challenge for many health facilities in the developing world, particularly in paediatric care units. The cost-effectiveness of oxygen concentrators versus compressed gas cylinders as a source of oxygen in low-resource health facilities has been demonstrated, but evidence of their long-term functionality is scarce. The Biomedical Engineering Department at the Medical Research Council Unit in The Gambia manages and maintains 27 oxygen concentrators at several sites across the country, and has kept electronic records of all preventive maintenance checks and repairs on these devices since 2006. Through a retrospective analysis of these maintenance records, the objective of this study was to assess the long-term reliability and maintenance needs of oxygen concentrators in a low-income setting with biomedical engineering technologist support. We found that the majority of concentrator repairs are low-cost and require a low experience level to complete. We estimate that the useful lifespan of oxygen concentrators in low-resource settings could reasonably exceed 7 years provided a system is in place for routine preventive maintenance. We conclude the paper with additional insights on the broader support ecosystem required to manage and maintain oxygen concentrators in low-resource settings.

Sanitation in neighbourhood and household domains can provide primary protection against diarrhea morbidity, yet their distinct health benefits have not been succinctly distinguished and reviewed. We present here the first systematic review and meta-analysis of the distinct effect of neighbourhood and household sanitation conditions on diarrhea morbidity. We identified studies reporting the effect of neighbourhood-level exposure to wastewater or household sanitation facilities on diarrhea, by performing comprehensive search on five databases, namely the Cochrane library, PubMed, Embase, Scopus and Web of Science, from the earliest date available to February 2015. Twenty-one non-randomized studies and one randomized controlled trial met the pre-determined inclusion criteria, consisting of six datasets on neighbourhood sanitation conditions (total 8271 subjects) and 20 datasets on household sanitation (total 20021 subjects). We calculated the pooled effect estimates of neighbourhood and household sanitation conditions on diarrhea morbidity using the inverse variance random-effects model. The pooled effect estimates showed that both neighbourhood sanitation conditions (odds ratio = 0.56, 95%CI: 0.40-0.79) and household sanitation (odds ratio = 0.64, 95%CI: 0.55-0.75) are associated with reduced diarrheal illness, and that the magnitudes of the associations are comparable. Evidence of risk of bias and heterogeneity were found in the included studies. Our findings confirm that both neighbourhood sanitation conditions and household sanitation are associated with considerable reduction in diarrhea morbidity, in spite of a number of methodological shortcomings in the included studies. Furthermore, we find evidence that neighbourhood sanitation conditions is associated with similar magnitude of reduction in diarrhea morbidity as household sanitation. The findings suggest that, in addition to household sanitation provision, dual emphasis on neighbourhood sanitation through public sanitation infrastructure provision and community-wide sanitation adoption is advisable for effective reduction of diarrheal disease burden.

A new approach for the rapid destruction of human waste using smouldering combustion is presented. Recently, self-sustaining smouldering combustion was shown to destroy the organic component of simulated human solid waste and dog faeces resulting in the sanitization of all pathogens using a batch process (Yermán et al., 2015). Here, a continuous smouldering process is demonstrated for the first time, allowing for a much smaller reactor size and much less energy input per mass of waste treated. The self-sustained smouldering of simulated human faeces mixed with sand is evaluated over long periods (more than 16 h) based on a single ignition. The key process of intermittent self-sustained smouldering, in which the reaction is terminated and restarted by only turning the air off and on, is demonstrated. Experiments examine the influence of two key operator controls: airflow rate and set elevation of the quasi-steady-state smouldering front in a 37 cm high reactor. Quasi-steady-state fuel destruction rates from 93 g/h to 12 g/h were achieved by varying the superficial flow velocity from 7.4 cm/s to 0.11 cm/s, the latter with a velocity approximately an order of magnitude lower than possible for a self-sustaining reaction in an equivalent batch system. Excess energy of up to 140 J/g of sand was recovered from the clean sand produced in each cycle, which could be used to further increase the energy efficiency of this novel waste treatment system.

A computational model was developed to simulate drug distribution in the posterior segment of the eye after intravitreal injection and ocular implantation. The effects of important factors in intravitreal injection such as injection time, needle gauge and needle angle on the ocular drug distribution were studied. Also, the influences of the position and the type of implant on the concentration profile in the posterior segment were investigated. Computational Fluid Dynamics (CFD) calculations were conducted to describe the 3D convective-diffusive transport. The geometrical model was constructed based on the human eye dimensions. To simulate intravitreal injection, unlike previous studies which considered the initial shape of the injected drug solution as a sphere or cylinder, the more accurate shape was obtained by level-set method in COMSOL. The results showed that in intravitreal injection the drug concentration profile and its maximum value depended on the injection time, needle gauge and penetration angle of the needle. Considering the actual shape of the injected solution was found necessary to obtain the real concentration profile. In implant insertion, the vitreous cavity received more drugs after intraocular implantation, but this method was more invasive compared to the periocular delivery. Locating the implant in posterior or anterior regions had a significant effect on local drug concentrations. Also, the shape of implant influenced on concentration profile inside the eye. The presented model is useful for optimizing the administration variables to ensure optimum therapeutic benefits. Predicting and quantifying different factors help to reduce the possibility of tissue toxicity and to improve the treatment efficiency.

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

Background Low- and middle-income countries (LMICs) are developing novel approaches to healthcare that may be relevant to high-income countries (HICs). These include products, services, organizational processes, or policies that improve access, cost, or efficiency of healthcare. However, given the challenge of replication, it is difficult to identify innovations that could be successfully adapted to high-income settings. We present a set of criteria for evaluating the potential impact of LMIC innovations in HIC settings. Methods An initial framework was drafted based on a literature review, and revised iteratively by applying it to LMIC examples from the Center for Health Market Innovations (CHMI) program database. The resulting criteria were then reviewed using a modified Delphi process by the Reverse Innovation Working Group, consisting of 31 experts in medicine, engineering, management and political science, as well as representatives from industry and government, all with an expressed interest in reverse innovation. Results The resulting 8 criteria are divided into two steps with a simple scoring system. First, innovations are assessed according to their success within the LMIC context according to metrics of improving accessibility, cost-effectiveness, scalability, and overall effectiveness. Next, they are scored for their potential for spread to HICs, according to their ability to address an HIC healthcare challenge, compatibility with infrastructure and regulatory requirements, degree of novelty, and degree of current collaboration with HICs. We use examples to illustrate where programs which appear initially promising may be unlikely to succeed in a HIC setting due to feasibility concerns. Conclusions This study presents a framework for identifying reverse innovations that may be useful to policymakers and funding agencies interested in identifying novel approaches to addressing cost and access to care in HICs. We solicited expert feedback and consensus on an empirically-derived set of criteria to create a practical tool for funders that can be used directly and tested prospectively using current databases of LMIC programs.

To detect antibody on pen-side is a rapid way to know the avian influenza (AI) infectious status in a chicken flock. The purpose of this study was to develop an immunochromatographic strip (ICS) assay to detect the antibody against the AI virus (AIV) for field applications. The ICS was constructed by fixing an AIV strain A/chicken/Taiwan/2838V/2000 (H6N1) onto a nitrocellulose membrane as the antigen at the test line and goat anti-rabbit IgG antibody at the control line. The colloidal gold conjugated with rabbit anti-chicken IgG was used as the tracer. The present ICS was used to detect antibodies against avian influenza virus in 326 chicken serum samples from the field. Compared with HI, this ICS could detect antibodies against H5 and H6 AIVs. The hemagglutination inhibition (HI) test was used as the standard to evaluate the ICS accuracy. The results showed that the sensitivity and specificity of this ICS reached 95.2% (159/167) and 94.3% (150/159), respectively. The Kappa value of the HI and ICS was 0.896 (P0.001). In conclusion, this ICS could be used as a rapid test to detect antibodies against AIVs in the field.

To determine the outward permeability of retina-choroid-sclera (RCS) layer for different ophthalmic drugs and to develop correlations between drug physicochemical properties and RCS permeability. A finite volume model was developed to simulate pharmacokinetics in the eye following drug administration by intravitreal injection. The RCS permeability was determined for 32 compounds by best fitting the drug concentration-time profile obtained by simulation with previously reported experimental data. Multiple linear regression was then used to develop correlations between best fit RCS permeability and drugs physicochemical properties. The RCS drug permeabilities had values that ranged over 3 × 10−6 m/s. Regression analysis for hydrophilic compounds showed that more than 92% of the variation in permeability values can be explained by correlative models of drug properties that include logarithm of the octanol-water partition coefficient (LogP), protein binding (PB), number of hydrogen bond acceptors (HBA), hydrogen bond donors (HBD), polar surface area (PSA) and dissociation constant (pKa) as independent variables. Regression analysis for lipophilic compounds showed that no significant correlation can be found between just physicochemical properties and RCS permeability. Using the RCS permeability obtained from this study for different drugs, one can predict pharmacokinetics of intravitreal drug delivery systems such as solid implants or colloidal systems. Furthermore, the developed correlations between RCS permeability and physicochemical properties of drugs are useful in early drug development by predicting RCS permeability and drug concentration in the vitreous without experimental data.

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

This article introduces the formulation of alcohol-free, lecithin microemulsion-based gels (MBGs) prepared with gelatin as gelling agent. The influence of oil, water, lecithin and hydrophilic and lipophilic additives (linkers) on the rheological properties and appearance of these gels was systematically explored using ternary phase diagrams. Clear MBGs were obtained in regions of single phase microemulsions (μEs) at room temperature. Increasing the water content in the formulation increased the elastic modulus of the gels, while increasing the oil content had the opposite effect. The hydrophilic additive (PEG-6-caprylic/capric glycerides) was shown to reduce the elastic modulus of gelatin gels, particularly at high temperatures. In contrast to anionic (AOT) μEs, the results suggest that in lecithin (nonionic) μEs, the introduction of gelatin “dehydrates” the μE. Finally, when the transdermal transport of lidocaine formulated in the parent μE and the resulting MBG were compared, only a minor retardation in the loading and release of lidocaine was observed.

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.

Reversible addition-fragmentation chain transfer (RAFT) polymerization was used successfully to synthesize temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm), poly(methacrylic acid) (PMAA), and their temperature-responsive block copolymers. Detailed RAFT polymerization kinetics of the homopolymers was studied. PNIPAAm and PMAA homopolymerization showed living characteristics that include a linear relationship between Mn and conversion, controlled molecular weights, and relatively narrow molecular weight distribution (PDI < 1.3). Furthermore, the homopolymers can be reactivated to produce block copolymers. The RAFT agent, carboxymethyl dithiobenzoate (CMDB), proved to control molecular weight and PDI. As the RAFT agent concentration increases, molecular weight and PDI decreased. However, CMDB showed evidence of having a relatively low chain transfer constant as well as degradation during polymerization. Solution of the block copolymers in phosphate buffered saline displayed temperature reversible characteristics at a lower critical solution temperature (LCST) transition of 31°C. A 5 wt % solution of the block copolymers form thermoreversible gels by a self-assembly mechanism above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1191–1201, 2006

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 previously reported on a novel system termed Lipobead that consists of hydrogel beads encased within an anchored lipid bilayer. The hydrogel particles are formed by inverse suspension polymerization of dimethylacrylamide with N,N'-ethylenebis(acrylamide). During the polymerization stage, the water in oil emulsion is interfacially stabilized by small molecule surfactants as well as a small percentage of lipid functionalized with a vinyl group. The functionalized lipid becomes tethered to the bead surface and promotes the assembly of a lipid bilayer on the surface of the hydrogel beads. The presence of the functionalized lipid during polymerization dramatically alters the yield, average size, and size distribution of beads produced. This paper examines the effect of various chemical and physical processing parameters on the average size and size distribution of beads produced when lipid is a component of the surfactant mixture. Relationships between the processing parameters, average bead size, and size distribution were established. Macroscopic properties of the lipid bilayers of Lipobeads were also evaluated including phase transition temperature as well as permeability to the small polar molecule, adenosine triphosphate. It was established that the presence of functionalized lipid improves the organization of the bilayer on the Lipobead surface.

The overall objective of our work was to make a hydrogel-supported phospholipid bilayer that models a cytoskeleton-supported cell membrane and provides a platform for studying membrane biology. Previously, we demonstrated that a pre-Lipobead, consisting of phospholipids covalently attached to the surface of a hydrogel, could give rise to a Lipobead when incubated with liposomes because the attached phospholipids promote self-assembly of a phospholipid membrane on the pre-Lipobead. We now report the properties of that Lipobead membrane. The lateral diffusion coefficient of fluorescently labeled phosphatidylcholine analogs in the membrane was measured by fluorescence recovery after photobleaching and was found to decrease as the surface anchor density and hydrogel crosslinking density increased. Results from the quenching of phosphatidylcholine analogs suggest that the phospholipid membrane of the Lipobead was composed mostly of a semipermeable lipid bilayer. However, the diffusional barrier properties of the Lipobead membrane were demonstrated by the entrapment of 1.5–3.0K dextran molecules in the hydrogel core after liposome fusion. This hydrogel-supported bilayer membrane preparation shows promise as a new platform for studying membrane biology and for high throughput drug screening.

Direct visualization of IPN morphology formed during polymerization-induced phase separation (PIPS) of PDMS−PMAA IPNs is reported. Laser scanning confocal microscopy (LSCM) and hydrophilic fluorescent probes of varying molecular weights were used to image hydrophilic domains in PDMS−PMAA IPNs. The images reveal complex, superimposed structures of hydrophilic domains of varying sizes and spatial distributions. This morphology is attributed to the phase-separated structures formed and partially arrested at continuously varying quench depths during the PIPS process. These observations contribute to the understanding of morphology development in IPNs.

Oxygen concentrators are an appropriate and low-cost technology for supplying medical oxygen in low-resource settings; however some maintenance and occasional repairs are required to optimise their longevity. Through a skillmapping analysis based on historical concentrator repair logs, we identified 31 basic technician skills that would be sufficient for the repair of over 90% of observed oxygen concentrator failures as well as for routine preventive maintenance. Most of these skills are drawn from the library of Biomedical Technician Assistant skills developed by the Developing World Healthcare Technologies Lab and Engineering World Health. We use this skill-mapping analysis to propose an evidence-based training curriculum specifically tailored to the maintenance of oxygen concentrators in low-resource settings.

We have synthesized a phospholipid−hydrogel conjugate that appears to drive the self-assembly of lipid membranes. A one-step radical polymerization synthesis of the conjugate was devised using lipi...

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...

Poly(methacrylic acid) (PMAA) grafted porous PE membranes (PE-g-PMAA) were studied. It was found that (1) a wide range of graft yields can be achieved by varying irradiation time (20–240 min) and monomer concentration (0.22M–0.66M), (2) the grafted membrane exhibits reversible permeability response, (3) the membrane shows a maximum permeability response at an intermediate permeant molecular weight due to size exclusion effect, and (4) depending on the graft yield, two types of permeability response can be obtained. These observations are consistent with our earlier study on poly(N-isopropylacrylamide) (PNIPAAm)–grafted porous polyethylene membranes. In addition, it was observed that the solvent used during grafting may influence the graft location—presumably due to variations in pore wetting. Specifically, compared to water solvent, methanol can increase grafting inside membrane pores, an observation inferred from membrane swelling, thickness measurement, and SEM characterization. Moreover, preferential grafting inside the membrane pores, as affected by increasing methanol content in the grafting solvent, results in lower membrane permeability and a greater pore graft-controlled type of permeability response. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 778–786, 2000