[Show abstract][Hide abstract] ABSTRACT: This research explores the photofermentation of glycerol to hydrogen by Rhodopseudomonas palustris, with the objective to maximise hydrogen production. Two piecewise models are designed to simulate the entire growth phase of R. palustris; a challenge that few dynamic models can accomplish. The parameters in both models were fitted by the present batch experiments through the solution of the underlying optimal control problems by means of stable and accurate discretisation techniques. It was found that an initial glutamate to glycerol ratio of 0.25 was optimal and was independent of the initial biomass concentration. The glycerol conversion efficiency was found to depend on initial biomass concentration and its computational peak is 64.4%. By optimising a 30-day industrially relevant batch process, the hydrogen productivity was improved to be 37.7 mL g biomass−1 h−1 and the glycerol conversion efficiency was maintained at 58%. The models can then be applied as the connection to transfer biohydrogen production from laboratory scale into industrial scale.
Chemical Engineering Science 07/2015; 130:68-78. DOI:10.1016/j.ces.2015.02.045 · 2.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Few infant drug delivery methods are tailored for dosing and administering oral medications to breastfeeding infants, especially in resource-limited settings. The infant annual mortality rate exceeds 4.8 million annually, and many leading causes of child mortality are largely preventable with safe and easy to administer medications. Therefore, there is a need for development of novel infant drug delivery and dosing methods. In response to this need, we are developing the nipple shield delivery system (NSDS) and a method of testing the device in vitro. The NSDS, when worn by a mother during breastfeeding, releases medications or nutrients from a tablet it contains, into milk consumed by the infant, simultaneously dosing and delivering the active pharmaceutical ingredients. To test this device in vitro, a breastfeeding simulation apparatus is needed to mimic the process of maternal lactation and infant behaviours during breastfeeding. We have developed a simulation apparatus with functionalities for mimicking lactation flow rates through a physiologically accurate breast mimic and for monitoring and mimicking infant suckling behaviours including sucking rate and imparted pressures. The current aim of our research is to increase the physiological accuracy of the apparatus, by developing a method to also test the potential impact of infant tongue use on the NSDS during breastfeeding. An infant tongue mimic was constructed based on modifications to a peristaltic pump. A metal plate was attached to mimic an infant upper palate, and a piezoresistive sensor was placed in the system to measure the pressure exerted by the tongue mimic and palate mimic on tablets contained in tubing placed in between. The mimic, through peristaltic motion and by applying a range of pressures potentially imparted by an infant tongue, is then used to test the impact of infant tongue movements on release rates of material which could be contained in an NSDS under flow conditions similar to those during breastfeeding. The release of the model compound sulphorhodamine b from a potential NSDS tablet formulation was quantified from the tongue mimic system at various tongue mimic speeds and applied pressures. Greater than 76% percent release occurred within 600 seconds, well within the 16.6 minute length of an average breastfeed, for tongue mimic contact rates of 0-240 contacts per minute into water flowing at the average expression rate of 6 mL/min. Preliminary results indicate the tongue mimic system can impart pressures and mimic contact rates in the ranges of those of an infant tongue on potential tablets which are being developed and screened for use in the NSDS. This tongue mimic system will improve the accuracy of our breastfeeding simulation apparatus for further in vitro testing of the NSDS as we continue developing this method for oral delivery of medications to infants.
[Show abstract][Hide abstract] ABSTRACT: Opportunities exist in preparative chromatography for alternative chromatography media that possess high binding capacity and throughput, but are also economically feasible for single use disposability and avoid column packing. An ion-exchange functionalised, microporous walled micro-capillary film (MMCF), has been developed as a module for cation-exchange separation of proteins. A MMCF module has been operated on a standard AKTA chromatography system at pressures up to 1.5 MPa and superficial flow velocities up to 54,000 cm h−1. The dynamic binding capacity of the MMCF module at 10% breakthrough was 13.8 mg lysozyme/ml adsorbent volume, which is comparable to the capacity of current commercial adsorbents. Frontal analysis studies using a mixture of lysozyme and bovine serum albumin (BSA) have shown that lysozyme can be isolated free of BSA to the limit of detection of the SDS gel assay used. 98.8% of the total sample eluted was the target protein lysozyme with only 1.2% BSA impurity. MMCF may thus be a viable chromatographic medium for preparative protein chromatography.
[Show abstract][Hide abstract] ABSTRACT: The ability of an anion exchange membrane to purify a γ-retrovirus was assessed and optimised with respect to different loading and wash buffers. Recoveries of infectious virus greater than 50% were consistently obtained, while specific titre was increased up to one thousand fold when compared to the material loaded. Specific proteins removed and retained by this optimised process were identified by mass spectrometry. It was possible to successfully bind and elute the equivalent of 1.27×10(8)Ifu/ml of ion exchange membrane. This could then be highly concentrated, with infectious virus concentrated to a maximum of 420-fold compared to the load.
Journal of Chromatography A 03/2014; 1340(100). DOI:10.1016/j.chroma.2014.03.023 · 4.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aqueous core colloidosomes encapsulating the enzyme amylase were manufactured with a shell comprising polymer latex particles of diameter 153 nm. The colloidosomes were sealed with calcium carbonate by precipitation between an inner phase of Na2CO3 and an outer phase of CaCl2. This seal allowed the retention of small molecules, such as dyes, as well as larger enzyme molecules, for several months. The encapsulated material could be released by dissolution of the CaCO3 with acid, upon a large dilution in water, or by applying a sufficient shear. The degree of release could be controlled since the greater the mass of CaCO3 precipitated onto the colloidosome shell, the greater the dilution or shear required to achieve release. The calcium carbonate seal protected encapsulated amylase from the detrimental effects of components in a liquid laundry detergent for several months so that, on triggered release, the enzyme retained its high activity.
[Show abstract][Hide abstract] ABSTRACT: Enteric coated oral tablets or capsules can deliver dried live cells directly into the intestine. Previously, we found that a live attenuated bacterial vaccine acquired sensitivity to intestinal bile when dried, raising the possibility that although gastric acid can be bypassed, significant loss of viability might occur on release from an enteric coated oral formulations. Here we demonstrate that some food-grade lyophilised preparations of Lactobacillus casei and Lactobacillus salivarius also show temporary bile sensitivity that can be rapidly reversed by rehydration. To protect dried cells from temporary bile sensitivity, we propose using bile acid adsorbing resins, such as cholestyramine, which are bile acid binding agents, historically used to lower cholesterol levels. Vcaps™ HPMC capsules alone provided up to 830-fold protection from bile. The inclusion of 50% w/w cholestyramine in Vcaps™ HPMC capsules resulted in release of up to 1700-fold more live Lactobacillus casei into simulated intestinal fluid containing 1% bile, when compared to dried cells added directly to bile. We conclude that delivery of dried live probiotic organisms to the intestine may be improved by providing protection from bile by addition of bile adsorbing resins and the use of HPMC capsules.
New Biotechnology 09/2013; 31(1). DOI:10.1016/j.nbt.2013.09.001 · 2.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: For stem cell therapy to become a routine reality, one of the major challenges to overcome is their storage and transportation. Currently this is achieved by cryopreserving cells utilising the cryoprotectant dimethyl sulfoxide (Me2SO). Me2SO is toxic to cells, leads to loss of cell functionality, and can produce severe side effects in patients. Potentially, cells could be frozen using the cryoprotectant trehalose if it could be delivered into the cells at a sufficient concentration. The novel amphipathic membrane permeabilising agent PP-50 has previously been shown to enhance trehalose uptake by erythrocytes, resulting in increased cryosurvival. Here, this work was extended to the nucleated human cell line SAOS-2. Using the optimum PP-50 concentration and media osmolarity, cell viability post-thaw was 60 ± 2%. In addition, the number of metabolically active cells 24 h post-thaw, normalised to that before freezing, was found to be between 103 ± 4% and 91 ± 5%. This was found to be comparable to cells frozen using Me2SO. Although reduced (by 22 ± 2%, p = 0.09), the doubling time was found not to be statistically different to the non-frozen control. This was in contrast to cells frozen using Me2SO, where the doubling time was significantly reduced (by 41 ± 4%, p = 0.004). PP-50 mediated trehalose delivery into cells could represent an alternative cryopreservation protocol, suitable for research and therapeutic applications.
[Show abstract][Hide abstract] ABSTRACT: The use of small interfering RNAs (siRNAs) to down-regulate the expression of disease-associated proteins carries significant promise for the treatment of a variety of clinical disorders. One of the main barriers to the widespread clinical use of siRNAs, however, is their entrapment and degradation within the endolysosomal pathway of target cells. Here we report the trafficking and function of PP75, a non-toxic, biodegradable, lipid membrane disruptive anionic polymer composed of phenylalanine derivatized poly(L-lysine iso-phthalamide). PP75 is readily endocytosed by cells, safely permeabilizes endolysosomes in a pH dependent manner and facilitates the transfer of co-endocytosed materials directly into the cytoplasm. The covalent attachment of siRNAs to PP75 using disulfide linkages generates conjugates that effectively traffic siRNAs to the cytoplasm of target cells both in vitro and in vivo. In a subcutaneous malignant glioma tumor model, a locally delivered PP75-stathmin siRNA conjugate decreases stathmin expression in tumor cells and, in combination with the nitrosourea chemotherapy carmustine, is highly effective at inhibiting tumor growth. PP75 may be clinically useful for the local delivery of siRNAs, in particular for the treatment of solid tumors.
[Show abstract][Hide abstract] ABSTRACT: Polymeric colloidosomes encapsulating viable lactic acid bacteria were prepared. An aqueous suspension of 153 nm poly(methyl methacrylate-co-butylacrylate) latex particles plus Lactobacillus crispatus was emulsified in a continuous phase of sunflower oil. By adding a small amount of ethanol and salt to the oil phase the latex particles at the surface of the emulsion droplets aggregate to form the colloidosome shells. The colloidosomes have been examined using optical, confocal and scanning electron microscopies. The viability of the bacteria was tested using fluorescent molecular probes. The encapsulated lactic acid bacteria were able to metabolize glucose from solution and produce acid albeit at a slower rate compared to unencapsulated microbes. This demonstrates transport limitation through the colloidosome shell and restriction of the cellular metabolism due to encapsulation. Protection of the bacteria by encapsulation in colloidosomes was also demonstrated; a significantly larger number of encapsulated bacteria maintained viability in simulated stomach conditions compared to unencapsulated microbes.
[Show abstract][Hide abstract] ABSTRACT: A new disposable adsorbent material for fast anion-exchange capture of nano-complexes without prefiltering, clarification or pre-processing of samples was developed based on plastic microcapillary films (MCFs). An MCF containing 19 parallel microcapillaries, each with a mean internal diameter of 142 ± 10 μm, was prepared using a melt extrusion process from an ethylene-vinyl alcohol copolymer (EVOH). The MCF internal surfaces were functionalised using branched chain chemistries to attach quaternary amine groups producing an anion-exchange adsorbent. The purification of nano-complexes using this newly fabricated MCF-EVOH-Q was successfully demonstrated with the capture of lentivirus from pre-filtered culture harvest. This 5m chromatographic substrate was found to bind and elute ∼40% of bound lentivirus or 2.5 × 10(6)infectious units (ifu). The unique properties of this chromatographic substrate that allow the passage of large particulates was further demonstrated with the capture of lentiviral particles from unfiltered un-processed culture media containing cells and cell debris. Using this approach, 56% or 1 × 10(7)ifu of captured lentivirus was eluted. A device based on this new material might be used at an early stage in clinical lentiviral production to harvest lentiviral particles, directly from bioreactors.
Journal of Chromatography A 06/2012; 1251:236-9. DOI:10.1016/j.chroma.2012.06.072 · 4.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new drug delivery method for infants is presented which incorporates an active pharmaceutical ingredient (API)-loaded insert into a nipple shield delivery system (NSDS). The API is released directly into milk during breastfeeding. This study investigates the feasibility of using the NSDS to deliver the microbicide sodium dodecyl sulfate (SDS), with the goal of preventing mother-to-child transmission (MTCT) of HIV during breastfeeding in low-resource settings, when there is no safer alternative for the infant but to breastfeed. SDS has been previously shown to effectively inactivate HIV in human milk. An apparatus was developed to simulate milk flow through and drug release from a NSDS. Using this apparatus milk was pulsed through a prototype device containing a non-woven fiber insert impregnated with SDS and the microbicide was rapidly released. The total SDS release from inserts ranged from 70 to 100% of the average 0.07 g load within 50 ml (the volume of a typical breastfeed). Human milk spiked with H9/HIV(IIIB) cells was also passed through the same set-up. Greater than 99% reduction of cell-associated HIV infectivity was achieved in the first 10 ml of milk. This proof of concept study demonstrates efficient drug delivery to breastfeeding infants is achievable using the NSDS.
International Journal of Pharmaceutics 05/2012; 434(1-2):224-34. DOI:10.1016/j.ijpharm.2012.05.035 · 3.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Under dehydration conditions, amphipathic late embryogenesis abundant proteins fold spontaneously from a random conformation into α-helical structures, and this transition is promoted by the presence of membranes. To gain insight into the thermodynamics of membrane association, we model the resulting α-helical structures as infinite rigid cylinders patterned with hydrophobic and hydrophilic stripes oriented parallel to their axis. Statistical thermodynamic calculations using single chain mean field theory show that the relative thickness of the stripes controls the free energy of interaction of the α-helices with a phospholipid bilayer, as does the bilayer structure and the depth of the equilibrium penetration of the cylinders into the bilayer. The results may suggest the optimal thickness of the stripes to mimic the association of such protein with membranes.
[Show abstract][Hide abstract] ABSTRACT: In this work a novel microfluidic device was constructed in situ containing the smallest microscopic co-polymeric immobilised metal affinity (IMA) adsorbent yet documented. This device has for the first time allowed the microlitre scale chromatographic assay of histidine-tagged proteins in a biological sample. To enable this approach, rather than using a high capacity commercial packed bed column which requires large sample volumes and would be susceptible to occlusion by cell debris, a microgram capacity co-polymeric chromatographic substrate suitable for analytical applications was fabricated within a microfluidic channel. This porous co-polymeric IMA micro-chromatographic element, only 27μl in volume, was assessed for the analytical capture of two different histidine-tagged recombinant fusion proteins. The micro-chromatographic adsorber was fabricated in situ by photo-polymerising an iminodiacetic acid (IDA) functionalised polymer matrix around a template of fused 100μm diameter NH(4)Cl particles entirely within the microfluidic channel and then etching away the salt with water to form a network of interconnected voids. The surface of the micro-chromatographic adsorber was chemically functionalised with a chelating agent and loaded with Cu(2+) ions. FTIR and NMR analysis verified the presence of the chelating agent on the adsorbent surface and its Cu(2+) ion binding capacity was determined to be 2.4μmol Cu(2+) (ml of adsorbent)(-1). Micro-scale equilibrium adsorption studies using the two different histidine-tagged proteins, LacI-His(6)-GFP and α-Synuclein-His(8)-YFP, were carried out and the protein binding capacity of the adsorbent was determined to be 0.370 and 0.802mg(g of adsorbent)(-1), respectively. The dynamic binding capacity was determined at four different flow rates and found to be comparable to the equilibrium binding capacity at low flow rates. The sensing platform was also used to adsorb LacI-His(6)-GFP protein from crude cell lysate. During adsorption, laser scanning confocal microscopy identified locations within the adsorbent where protein adsorption and desorption occurred. The findings indicate that minimal channelling, selective product capture and near quantitative elution of the captured (adsorbed) product could be achieved, supporting the application of this new device as a high-throughput process analytical tool (PAT) for the in-process monitoring of histidine-tagged proteins in manufacturing.
New Biotechnology 01/2012; 29(4):494-501. DOI:10.1016/j.nbt.2012.01.002 · 2.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a simple device for multiplex quantitative enzyme-linked immunosorbant assays (ELISA) made from a novel melt-extruded microcapillary film (MCF) containing a parallel array of 200 μm capillaries along its length. To make ELISA devices different protein antigens or antibodies were immobilised inside individual microcapillaries within long reels of MCF extruded from fluorinated ethylene propylene (FEP). Short pieces of coated film were cut and interfaced with a pipette, allowing sequential uptake of samples and detection solutions into all capillaries from a reagent well. As well as being simple to produce, these FEP MCF devices have excellent light transmittance allowing direct optical interrogation of the capillaries for simple signal quantification. Proof of concept experiments demonstrate both quantitative and multiplex assays in FEP MCF devices using a standard direct ELISA procedure and read using a flatbed scanner. This new multiplex immunoassay platform should find applications ranging from lab detection to point-of-care and field diagnostics.
Lab on a Chip 12/2011; 11(24):4267-73. DOI:10.1039/c0lc00357c · 5.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polymeric colloidosomes encapsulating viable Baker's yeast cells were prepared. To make the capsules, an aqueous suspension of 153 nm poly(methyl methacrylate-co-butyl acrylate) latex particles plus yeast cells is emulsified in a continuous phase of sunflower oil. By adding a small amount of ethanol to the oil phase, the latex particles at the surface of the emulsion droplets aggregate, forming the colloidosome shells. The microcapsules have been examined using optical, confocal, and scanning electron microscopies. The viability of the yeast cells was tested using fluorescent molecular probes. The encapsulated Baker's yeast cells were able to metabolize glucose from solution, although at a slower rate compared to nonencapsulated yeast. This demonstrates diffusion limitation through the colloidosome shell. The diffusive resistance could be increased by manufacturing colloidosomes with a double latex shell.