Chemical and Biomolecular Engineering - Research Publications
Permanent URI for this collection
Search Results
1 - 10 of 1231
-
ItemSeparation of Methane and Nitrogen Using Heavy Reflux Pressure Swing Adsorption: Experiments and Modeling(American Chemical Society, 2023-05-10)Pressure swing adsorption (PSA) is commonly used for the challenging task of separating methane (CH4) and nitrogen (N2) gas mixtures. Previously we used pilot-scale tests and process simulations to demonstrate how PSA cycles can be optimized for methane-nitrogen separations by adjusting the feed flow, cycle step time, and desorption pressure for a given column size. However, to produce a high-value product stream, dilute feeds with <25% CH4 generally require greater enrichment than can be achieved with optimized conventional cycles. In this work, we investigated the effects of including a heavy product reflux/purge step in PSA cycles on the separation of CH4/N2 using ionic liquidic zeolites (ILZs) as adsorbents through both pilot plant tests and process simulations. In the pilot demonstrations, the use of a heavy purge step allowed the enrichment of feed mixtures with 5.6 and 25.1% methane to 27.4 and 85.5% with recoveries of 83 and 96%, respectively, which outperforms most reported studies under similar operational conditions. However, while the refluxes increased from 74 to 80%, the recovery of CH4 dropped from 79 to 75% as CH4 was lost into the light product stream. Optimum separation performance in terms of CH4 purity and recovery occurred at a bed capacity ratio for the purge step of CPU≅0.87, which could help guide future selections of heavy purge flow rates for a given column size and adsorbent material.
-
ItemSupramolecular Assembly of Polyphenols and Nucleic Acids by Thermal Cycling for Immune Cell Activation(American Chemical Society (ACS), 2023)Supramolecular assembly of polyphenols and biomacromolecules (proteins and nucleic acids) has emerged as a versatile and simple strategy to construct nanomaterials with biological activity. Here, we report a strategy to finely control the supramolecular assembly of tannic acid and oligonucleotides into uniform and stable nanoparticles by exploiting the thermal cycling of tannic acid. The equilibrium of complexation is investigated, and individual nanoparticles are resolved with nanoscale resolution by using stochastic optical reconstruction microscopy. The nanoparticles incorporating cytosine phosphoguanine (CpG) oligonucleotides are efficiently taken up by cells and trafficked via endo/lysosomal compartments and induce up to a 7-fold increase in tumor necrosis factor secretion in RAW 264.7 macrophage cells compared with naked CpG oligonucleotides. This work highlights the potential of this simple approach to engineer two-component tannic acid–oligonucleotide nanoparticles for the intracellular delivery of therapeutic nucleic acids.
-
ItemStimuli-Responsive Delivery of Antimicrobial Peptides Using Polyelectrolyte Complexes(WILEY-V C H VERLAG GMBH, 2023-07-14)Antimicrobial peptides (AMPs) are antibiotics with the potential to address antimicrobial resistance. However, their translation to the clinic is hampered by issues such as off-target toxicity and low stability in biological media. Stimuli-responsive delivery from polyelectrolyte complexes offers a simple avenue to address these limitations, wherein delivery is triggered by changes occurring during microbial infection. The review first provides an overview of pH-responsive delivery, which exploits the intrinsic pH-responsive nature of polyelectrolytes as a mechanism to deliver these antimicrobials. The examples included illustrate the challenges faced when developing these systems, in particular balancing antimicrobial efficacy and stability, and the potential of this approach to prepare switchable surfaces or nanoparticles for intracellular delivery. The review subsequently highlights the use of other stimuli associated with microbial infection, such as the expression of degrading enzymes or changes in temperature. Polyelectrolyte complexes with dual stimuli-response based on pH and temperature are also discussed. Finally, the review presents a summary and an outlook of the challenges and opportunities faced by this field. This review is expected to encourage researchers to develop stimuli-responsive polyelectrolyte complexes that increase the stability of AMPs while providing targeted delivery, and thereby facilitate the translation of these antimicrobials.
-
ItemDeveloping the supraparticle technology for round window-mediated drug administration into the cochlea.(Elsevier BV, 2023-09)The semi-permeable round window membrane (RWM) is the gateway to the cochlea. Although the RWM is considered a minimally invasive and clinically accepted route for localised drug delivery to the cochlea, overcoming this barrier is challenging, hindering development of effective therapies for hearing loss. Neurotrophin 3 (NT3) is an emerging treatment option for hearing loss, but its therapeutic effect relies on sustained delivery across the RWM into the cochlea. Silica supraparticles (SPs) are drug delivery carriers capable of providing long-term NT3 delivery, when injected directly into the guinea pig cochlea. However, for clinical translation, a RWM delivery approach is desirable. Here, we aimed to test approaches to improve the longevity and biodistribution of NT3 inside the cochlea after RWM implantation of SPs in guinea pigs and cats. Three approaches were tested (i) coating the SPs to slow drug release (ii) improving the retention of SPs on the RWM using a clinically approved gel formulation and (iii) permeabilising the RWM with hyaluronic acid. A radioactive tracer (iodine 125: 125I) tagged to NT3 (125I NT3) was loaded into the SPs to characterise drug pharmacokinetics in vitro and in vivo. The neurotrophin-loaded SPs were coated using a chitosan and alginate layer-by-layer coating strategy, named as '(Chi/Alg)SPs', to promote long term drug release. The guinea pigs were implanted with 5× 125I NT3 loaded (Chi/Alg) SPs on the RWM, while cats were implanted with 30× (Chi/Alg) SPs. A cohort of animals were also implanted with SPs (controls). We found that the NT3 loaded (Chi/Alg)SPs exhibited a more linear release profile compared to NT3 loaded SPs alone. The 125I NT3 loaded (Chi/Alg)SPs in fibrin sealant had efficient drug loading (~5 μg of NT3 loaded per SP that weights ~50 μg) and elution capacities (~49% over one month) in vitro. Compared to the SPs in fibrin sealant, the (Chi/Alg)SPs in fibrin sealant had a significantly slower 125I NT3 drug release profile over the first 7 days in vitro (~12% for (Chi/Alg) SPs in fibrin sealant vs ~43% for SPs in fibrin sealant). One-month post-implantation of (Chi/Alg) SPs, gamma count measurements revealed an average of 0.3 μg NT3 remained in the guinea pig cochlea, while for the cat, 1.3 μg remained. Histological analysis of cochlear tissue revealed presence of a 125I NT3 signal localised in the basilar membrane of the lower basal turn in some cochleae after 4 weeks in guinea pigs and 8 weeks in cats. Comparatively, and in contrast to the in vitro release data, implantation of the SPs presented better NT3 retention and distribution inside the cochlea in both the guinea pigs and cats. No significant difference in drug entry was observed upon acute treatment of the RWM with hyaluronic acid. Collectively, our findings indicate that SPs and (Chi/Alg)SPs can facilitate drug transfer across the RWM, with detectable levels inside the cat cochlea even after 8 weeks with the intracochlear approach. This is the first study to examine neurotrophin pharmacokinetics in the cochlea for such an extended period of times in these two animal species. Whilst promising, we note that outcomes between animals were variable, and opposing results were found between in vitro and in vivo release studies. These findings have important clinical ramifications, emphasising the need to understand the physical properties and mechanics of this complex barrier in parallel with the development of therapies for hearing loss.
-
ItemThe effect of pH on the fat and protein within cream cheese and their influence on textural and rheological properties(Elsevier BV, 2020-12-01)The effect of variation in acid gel pH during cream cheese production was investigated. The gel microstructure was denser and cheese texture firmer, as the pH decreased from pH 5.0 to pH 4.3, despite the viscoelasticity of these gels remaining similar during heating. Protein hydration and secondary structure appeared to be key factors affecting both cheese microstructure and properties. Proteins within the matrix appeared to swell at pH 5.0, leading to a larger corpuscular structure; greater β-turn structure was also observed by synchrotron-Fourier transform infrared (S-FTIR) microspectroscopy and the cheese was softer. A decrease in pH led to a denser microstructure with increased aggregated β-sheet structure and a firmer cheese. The higher whey protein loss at low pH likely contributed to increased cheese hardness. In summary, controlling the pH of acid gel is important, as this parameter affects proteins in the cheese, their secondary structure and the resulting cream cheese.
-
ItemDesign and characterization of casein-whey protein suspensions via the pH-temperature-route for application in extrusion-based 3D-Printing(Elsevier BV, 2021-03)The current interest in individualized food through additive manufacturing has identified a need for more information on the formulation and printability of potential ingredients. Here, the effect of formulation parameters of casein–whey protein suspensions like the pH (4.8–5.4) as well as the casein content (8.0–12.0% (w/w)) mixed with whey protein (2.0–3.0% (w/w)) and the effect of pre-processing parameters including the denaturation of whey proteins (80 °C, 10 min; adjusted pH 6.55, 6.9 and 7.1) on the gel formation via the pH–temperature (T)-route was studied. Rheological measurements showed that the sol–gel transition temperature (G’ = 1 Pa) decreased and the aggregation rate of the casein–whey protein suspensions increased with increasing heating pH value. The aggregation rate was considered to be a key parameter predicting the printability of formulations. By exceeding a certain aggregation rate (250 Pa/10 K), casein–whey protein suspensions were found to be printable resulting in firm and stable gels.
-
ItemCharacterising the influence of milk fat towards an application for extrusion-based 3D-printing of casein-whey protein suspensions via the pH-temperature-route(ELSEVIER SCI LTD, 2021-04-28)This study presents the design and characterisation of casein−whey protein suspensions (8.0/10.0% (w/w) casein and 2.0/2.5% (w/w) whey protein) mixed with dairy fat (1.0, 2.5 and 5.0% (w/w) total fat) processed via the pH−temperature-route in preparation for 3D-printing. Mechanical treatment was applied to significantly decrease the particle size of the milk fat globules and increase surface area, creating small fat globules (<1 μm) covered with proteins, which could act as pseudo protein particles during gelation. Different proteins covered the fat globule surface after mechanical treatment, as a result of differences in the pH adjusted just prior to heating (6.55, 6.9 or 7.1). The protein-fat suspensions appeared similar by transmission electron cryogenic microscopy and the zeta-potential of all particles was unchanged by the heating pH, with a similar charge to the solution (~−20 mV) occurring after acidification (pH 4.8/5.0) at low temperatures (2 °C). A low heating pH (6.55) resulted in increased sol−gel transition temperatures (G՛ = 1 Pa) and a decreased rate of aggregation for protein−fat suspensions. A higher heating pH (6.9 and 7.1) caused an increased rate of aggregation (aggregation rate ≥ 250 Pa/10 K), resulting in materials more promising for application in extrusion-based printing. 3D-printing of formulations into small rectangles, inclusive of a sol−gel transition in a heated nozzle, was conducted to relate the aggregation rate towards printability.
-
ItemEffects of shredding on the functionality, microstructure and proteolysis of low-moisture mozzarella cheese(ELSEVIER SCI LTD, 2021-02-10)Low-moisture mozzarella cheese (LMMC) is commonly shredded before packaging, however, the effects of shredding are not fully understood. Industrially-produced block and shredded LMMC were studied during 8 weeks of storage at 4 °C. Cheese shredded on 15 d and at 8 weeks of age, coated with microcrystalline cellulose and stored in a modified atmosphere (70% N₂ and 30% CO₂), had an altered microstructure after 8 weeks compared with vacuum-packed block cheese. In the latter case the fat formed a more dispersed phase. Proteolysis was higher in shredded samples and a higher level of two bacterial proteases was detected. Despite these differences, the meltability and stretchability of the block and shredded LMMC were similar. The microstructure and functionality of cheese shredded at 15 d and stored for a further 6 weeks was similar to cheese shredded at 8 weeks, suggesting there is a flexible period for performing cheese shredding processes.
-
ItemStructure and functionality of almond proteins as a function of pH(ELSEVIER, 2021-11-03)Almond proteins have potential utility in a range of food and beverages but it is not clear how pH affects protein structure and function. The behaviour of almond protein isolate was examined under conditions of neutral and acidic pH (pH 7 and 4). The isolate was highly soluble (70–80%) at either pH. An increase in acidity lead to protein unfolding, an increase in random coil structure and the appearance of lower molecular weight proteins due to acidic hydrolysis. These structural changes at pH 4 increased the capacity for foam formation and foam stability, increased viscosity and led to concentration and age dependent thickening. Gels, similar in strength but with distinct microstructures and properties were obtained following heating. At pH 7, a particulate type gel with an interconnected protein network was formed, while the gel at pH 4 had a dense continuous protein matrix. The gels differed in their susceptibility to chemical disruption, suggesting different underlying molecular interactions. The ability to alter protein structure and properties as a function of pH and heating could be used to broaden the application of almond proteins and develop a variety of food products, such as protein supplements and vegan alternatives to traditional products.
-
ItemPilot scale concentration of cheese whey by forward osmosis: A short-cut method for evaluating the effective pressure driving force(Elsevier, 2020-11-01)Cheese whey was concentrated to a concentration factor of 2.7 in a pilot scale forward osmosis filtration system, using a commercial cellulose triacetate membrane in a spiral-wound configuration. The whey was concentrated in a batch mode, using sodium chloride as the draw solution at initial osmotic pressures of 53–75 bar. During the process, flux was shown to reduce due to the simultaneous decrease in the bulk osmotic pressure of the draw solution, increase in the bulk osmotic pressure of the whey and the effect of concentration polarisation on both sides of the membrane. The flux is known to be driven by the effective osmotic pressures of whey and the draw solution on the surface of the membrane active layer. A short-cut approach that requires minimal information in advance about the osmotic pressure of whey and the geometry of the filtration system was implemented, enabling the determination of these effective osmotic pressures. The results obtained were shown to be in agreement with the fundamental forward osmosis flux model. The short-cut approach can be utilised for estimating effective osmotic pressures of other liquid food streams to be concentrated by forward osmosis, without the need of external measurements.