Optimising poly(lactic-co-glycolic acid) microparticle fabrication using a Taguchi orthogonal array design-of-experiment approach

© 2019 Mensah et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The objective of this study was to identify, understand and generate a Taguchi orthogonal array model for the formation of 10–50 μm microparticles with applications in topical/ocular controlled drug delivery. Poly(lactic-co-glycolic acid) (PLGA) microparticles were fabricated by the single emulsion oil-in-water method and the particle size was characterized using laser diffraction and scanning electronic microscopy (SEM). Sequential Taguchi L 12 and L 18 orthogonal array (OA) designs were employed to study the influence of ten and eight parameters, respectively, on microparticle size (response). The first optimization step using the L 12 design showed that all parameters significantly influenced the particle size of the prepared PLGA microparticles with exception of the concentration of poly(vinyl alcohol) (PVA) in the hardening bath. The smallest mean particle size obtained from the L 12 design was 54.39 μm. A subsequent L 18 design showed that the molecular weight of PLGA does not significantly affect the particle size. An experimental run comprising of defined parameters including molecular weight of PLGA (89 kDa), concentration of PLGA (20% w/v), concentration of PVA in the emulsion (0.8% w/v), solvent type (ethyl acetate), organic/aqeuous phase ratio (1:1 v/v), vortexing speed (9), vortexing duration (60 seconds), concentration of PVA in hardening bath (0.8% w/v), stirring speed of hardening bath (1200 rpm) and solvent evaporation duration (24 hours) resulted in the lowest mean particle size of 23.51 μm which was predicted and confirmed by the L 18 array. A comparable size was demonstrated during the fabrication of BSA-incorporated microparticles. Taguchi OA design proved to be a valuable tool in determining the combination of process parameters that can provide the optimal condition for microparticle formulation. Taguchi OA design can be used to correctly predict the size of microparticles fabricated by the single emulsion process and can therefore, ultimately, save time and costs during the manufacturing process of drug delivery formulations by minimising experimental runs.Peer reviewedFinal Published versio

Polymers exhibiting lower critical solution temperatures as a route to thermoreversible gelators for healthcare

Funding Information: M.T.C. acknowledges support from the EPSRC (EP/T00813X/1). The University of Hertfordshire are thanked for funding the research project of P.H. Publisher Copyright: © 2020 The Authors. Advanced Functional Materials published by Wiley-VCH GmbHThe ability to trigger changes to material properties with external stimuli, so-called “smart” behavior, has enabled novel technologies for a wide range of healthcare applications. Response to small changes in temperature is particularly attractive, where material transformations may be triggered by contact with the human body. Thermoreversible gelators are materials where warming triggers reversible phase change from low viscosity polymer solution to a gel state. These systems can be generated by the exploitation of macromolecules with lower critical solution temperatures included in their architectures. The resultant materials are attractive for topical and mucosal drug delivery, as well as for injectables. In addition, the materials are attractive for tissue engineering and 3D printing. The fundamental science underpinning these systems is described, along with progress in each class of material and their applications. Significant opportunities exist in the fundamental understanding of how polymer chemistry and nanoscience describe the performance of these systems and guide the rational design of novel systems. Furthermore, barriers to translating technologies must be addressed, for example, rigorous toxicological evaluation is rarely conducted. As such, applications remain tied to narrow fields, and advancements will be made where the existing knowledge in these areas may be applied to novel problems of science.Peer reviewe

Poly(N-isopropyl acrylamide) – poly(ethylene glycol) – poly(N-isopropyl acrylamide) as a thermoreversible gelator for topical administration

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported licence: https://creativecommons.org/licenses/by-nc/3.0/.Poly(N-isopropyl acrylamide) – block– poly(ethylene glycol) – block– poly(N-isopropyl acrylamide) is known to exhibit a thermally-induced solution-to-gel transition in water, which may be exploited for biomedical applications. This “thermoreversible gelator” has great potential for application in topical drug delivery to the surfaces of the body such as the skin, eye, and vagina, but this has not yet been evaluated. This study evaluates PNIPAM98-PEG122-PNIPAM98 as a thermoreversible gelator for vaginal drug delivery, for the first time evaluating the effect of polymer concentration on gelation, studying rheological parameters relevant to topicals, measuring dissolution rates, stability and the phenomemon of mucoadhesion. Two drugs relevant to vaginal administration, progesterone and tenofovir disoproxil fumarate are investigated for use in the thermoreversible gelators, studying both hydrophobic and hydrophilic drug solubilisation and release. Throughout the study, comparison is made with poloxamer 407, the most commonly studied thermoreversible gelator. PNIPAM98-PEG122-PNIPAM98 exhibits several advantages for topical drug delivery, having low viscosity at room temperature to allow easy application, then exhibiting a gelation just below body temperature to form a viscous gel which is resistant to dissolution and relatively mucoadhesive. Drug release is highly dependent on temperature, with elevation to body temperature resulting in a dramatic retardation of progesterone release, which may be used in future medicines to provide sustained delivery of hydrophobic xenobiotics.Peer reviewedFinal Accepted Versio

A Design-of-Experiments Approach to Developing Thermoresponsive Gelators From Complex Polymer Mixtures

© 2020 Royal Society of Chemistry. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1039/D0ME00093K.This study investigated the effects of additives on the properties of poloxamer (P) 407 thermogels, employing a design-of-experiments (DoE) approach. P407 is a thermoresponsive triblock copolymer that exhibits a solution to gel transition at a critical temperature, typically between 15-25 °C, dependant on polymer concentration. This thermoresponsive gelation has made P407 attractive for many applications including drug delivery, cell culture and tissue engineering. However, the gels formed do not have sufficient strength for some applications where the materials will be exposed to shear, such as topical drug delivery. There have been attempts to improve P407 thermogel properties by the addition of other hydrophilic polymers. However, these studies were limited to a small number of polymers, typically in binary mixtures, exploring one variable at a time. In this study, a DoE approach was carried out using a two-level model exploring P407, P188, poly(vinyl alcohol), poly(ethylene glycol), and poly(acrylic acid) as variables, including an exploration of molecular weight of the latter three additives. The variables were given two different levels (concentrations) to generate a total of 16 training formulations. The thermoresponsive gelation of these 16 formulations was studied by rheometry and predictive models built for gel strength (G’) and gelation temperature (Tgel) responses. The model was able to predict the thermoresponsive gelation of complex octonary test blends, significantly streamlining formulation development processes relative to current methods. The model was then able to identify novel thermoresponsive gel formulations with 20 % improved gel strength compared to a standard 20 % P407 solution, which may be used as temperature-responsive materials for advanced healthcare applications.Peer reviewe

A drug-incorporated-microparticle-eggshell-membrane-scaffold (DIMES) dressing: a novel biomaterial for localised wound regeneration

Chronic wounds affect millions of people annually and have emotional and financial Implications in addition to health issues. The current treatment for chronic wounds involves the repeated use of bandages and drugs such as antibiotics over an extended period. A cost-effective and convenient solution for wound healing is the development of drug-incorporated bandages. This study aimed to develop a biocompatible bandage made of drug-incorporated poly (lactic-co-glycolic acid) (PLGA) microparticles (MPs) and eggshell membrane (ESM) for cornea wound healing. ESM has desirable properties for wound healing and can be isolated from eggshells using acetic acid or ethylenediaminetetraacetic acid (EDTA) protocols. Fluorescein isothiocyanate-labelled Bovine Serum Albumin (FITC-BSA) was used as a model drug, and the PLGA MPs were fabricated using a solvent extraction method. The MPs were successfully attached to the fibrous layer of the ESM using NaOH. The surface features of the ESM samples containing MPs were studied using a field emission scanning electron microscope (FESEM) and compared with blank ESM images. The findings indicated that the MPs were attached to the ESM fibres and had similar shapes and sizes as the control MPs. The fibre diameters of the MPs samples were assessed using Fiji-ImageJ software, and no significant changes were observed compared to the blank ESM. The surface roughness, Ra values, of the MPs incorporated ESM samples were evaluated and compared to the blank ESM, and no significant changes were found. Fourier transform infrared (FTIR) spectroscopy was used to analyse the chemical Composition of the bandage, and the spectra showed that the FBM were effectively incorporated into the ESM. The FTIR spectra identified the major peaks of the natural ESM and the PLGA polymer in the bandage. The bandage was transparent but had a reduced visibility in the waterproof test card method. The bandage achieved sustained drug release up to 10 days and was found to be biocompatible and non-toxic in a chorioallantoic membrane (CAM) assay. Overall, the drug-incorporated PLGA MPs-ESM bandage has great potential for treating chronic wounds

Thermoresponsive Triblock‐Copolymers of Polyethylene Oxide and Polymethacrylates: Linking Chemistry, Nanoscale Morphology, and Rheological Properties

© 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, https://creativecommons.org/licenses/by/4.0/Abstract: Thermoreversible gels switch from a free‐flowing liquid state to an elastic gel mesophase upon warming, displaying the reverse transition upon cooling. While this phenomenon makes these advanced materials highly attractive in numerous fields, the generation of optimal materials of tailored rheology and transition temperatures is stifled by the lack of design principles. To address this need, a library of ABA copolymers has been prepared with “A” blocks exhibiting thermoresponsive behavior and “B” blocks of poly(ethylene glycol). This library evaluates the effect of “A” chemistry, probing three polymer classes, and A/B block molecular weight on thermally‐induced phase changes in solutions of the polymers. An exploration by rheometry coupled to Small‐Angle Neutron Scattering (SANS) elucidates temperature‐dependent hierarchical self‐assembly processes occurring on the nanoscale as well as bulk rheology. This process deciphered links between rheology and supracolloidal assemblies (sphere, ellipses, and cylinders) within the gel state with interactions probed further via structure factors. Several design principles are identified to inform the genesis of next‐generation thermoreversible gels, alongside novel materials exhibited thermoresponsive behavior in the solution state for use in applied healthcare technologies.Peer reviewedFinal Published versio

Clearance of human IgG1-sensitised red blood cells in vivo in humans relates to the in vitro properties of antibodies from alternative cell lines.

We previously produced a recombinant version of the human anti-RhD antibody Fog-1 in the rat myeloma cell line, YB2/0. When human, autologous RhD-positive red blood cells (RBC) were sensitised with this IgG1 antibody and re-injected, they were cleared much more rapidly from the circulation than had been seen earlier with the original human-mouse heterohybridoma-produced Fog-1. Since the IgG have the same amino acid sequence, this disparity is likely to be due to alternative glycosylation that results from the rat and mouse cell lines. By comparing the in vitro properties of YB2/0-produced Fog-1 IgG1 and the same antibody produced in the mouse myeloma cell line NS0, we now have a unique opportunity to pinpoint the cause of the difference in ability to clear RBC in vivo. Using transfected cell lines that express single human FcγR, we showed that IgG1 made in YB2/0 and NS0 cell lines bound equally well to receptors of the FcγRI and FcγRII classes but that the YB2/0 antibody was superior in FcγRIII binding. When measuring complexed IgG binding, the difference was 45-fold for FcγRIIIa 158F, 20-fold for FcγRIIIa 158V and approximately 40-fold for FcγRIIIb. The dissimilarity was greater at 100-fold in monomeric IgG binding assays with FcγRIIIa. When used to sensitise RBC, the YB2/0 IgG1 generated 100-fold greater human NK cell antibody-dependent cell-mediated cytotoxicity and had a 103-fold advantage over the NS0 antibody in activating NK cells, as detected by CD54 levels. In assays of monocyte activation and macrophage adherence/phagocytosis, where FcγRI plays major roles, RBC sensitised with the two antibodies produced much more similar results. Thus, the alternative glycosylation profiles of the Fog-1 antibodies affect only FcγRIII binding and FcγRIII-mediated functions. Relating this to the in vivo studies confirms the importance of FcγRIII in RBC clearance.The work was supported by funding from the Department of Pathology, University of Cambridge through income that was derived from commercial exploitation of patented antibodies. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.This is the final published version. It first appeared at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0109463

Influence of ruminal methane on digesta retention and digestive physiology in non-lactating dairy cattle

Enteric methane (CH4) production is a side-effect of herbivore digestion, but it is unknown whether CH4 itself influences digestive physiology. We investigated the effect of adding CH4 to, or reducing it in, the reticulorumen (RR) in a 4 × 4 Latin square experiment with rumen-fistulated, non-lactating cows, with four treatments: (i) control, (ii) insufflation of CH4 (iCH4), (iii) N via rumen fistula, (iv) reduction of CH4 via administration of bromochloromethane (BCM). DM intake (DMI), apparent total tract digestibility, digesta mean retention times (MRT), rumen motility and chewing activity, spot breath CH4 emission (CH4exhal, litre/kg DMI) as well as CH4 dissolved in rumen fluid (CH4RRf, μg/ml) were measured. Data were analysed using mixed models, including treatment (or, alternatively, CH4exhal or CH4RRf) and DMI relative to body mass0·85 (rDMI) as covariates. rDMI was the lowest on the BCM treatment. CH4exhal was highest for iCH4 and lowest for BCM treatments, whereas only BCM affected (reduced) CH4RRf. After adjusting for rDMI, CH4RRf had a negative association with MRT in the gastrointestinal tract but not in the RR, and negative associations with fibre digestibility and measures of rumination activity. Adjusting for rDMI, CH4exhal had additionally a negative association with particle MRT in the RR and a positive association with rumen motility. Thus, higher rumen levels of CH4 (CH4exhal or CH4RRf) were associated with shorter MRT and increased motility. These findings are tentatively interpreted as a feedback mechanism in the ruminant digestive tract that aims at mitigating CH4 losses by shortening MRT at higher CH4

Canadian paediatric neurology workforce survey and consensus statement

Background: Little knowledge exists on the availability of academic and community paediatric neurology positions. This knowledge is crucial for making workforce decisions. Our study aimed to: 1) obtain information regarding the availability of positions for paediatric neurologists in academic centres; 2) survey paediatric neurology trainees regarding their perceptions of employment issues and career plans; 3) survey practicing community paediatric neurologists 4) convene a group of paediatric neurologists to develop consensus regarding how to address these workforce issues. Methods: Surveys addressing workforce issues regarding paediatric neurology in Canada were sent to: 1) all paediatric neurology program directors in Canada (n=9) who then solicited information from division heads and from paediatric neurologists in surrounding areas; 2) paediatric neurology trainees in Canada (n=57) and; 3) community paediatric neurologists (n=27). A meeting was held with relevant stakeholders to develop a consensus on how to approach employment issues. Results: The response rate was 100% from program directors, 57.9% from residents and 44% from community paediatric neurologists. We found that the number of projected positions in academic paediatric neurology is fewer than the number of paediatric neurologists that are being trained over the next five to ten years, despite a clinical need for paediatric neurologists. Paediatric neurology residents are concerned about job availability and desire more career counselling. Conclusions: There is a current and projected clinical demand for paediatric neurologists despite a lack of academic positions. Training programs should focus on community neurology as a viable career option

Inflammatory Biomarkers in Childhood Arterial Ischemic Stroke: Correlates of Stroke Cause and Recurrence.

Background and purposeAmong children with arterial ischemic stroke (AIS), those with arteriopathy have the highest recurrence risk. We hypothesized that arteriopathy progression is an inflammatory process and that inflammatory biomarkers would predict recurrent AIS.MethodsIn an international study of childhood AIS, we selected cases classified into 1 of the 3 most common childhood AIS causes: definite arteriopathic (n=103), cardioembolic (n=55), or idiopathic (n=78). We measured serum concentrations of high-sensitivity C-reactive protein, serum amyloid A, myeloperoxidase, and tumor necrosis factor-α. We used linear regression to compare analyte concentrations across the subtypes and Cox proportional hazards models to determine predictors of recurrent AIS.ResultsMedian age at index stroke was 8.2 years (interquartile range, 3.6-14.3); serum samples were collected at median 5.5 days post stroke (interquartile range, 3-10 days). In adjusted models (including age, infarct volume, and time to sample collection) with idiopathic as the reference, the cardioembolic (but not arteriopathic) group had higher concentrations of high-sensitivity C-reactive protein and myeloperoxidase, whereas both cardioembolic and arteriopathic groups had higher serum amyloid A. In the arteriopathic (but not cardioembolic) group, higher high-sensitivity C-reactive protein and serum amyloid A predicted recurrent AIS. Children with progressive arteriopathies on follow-up imaging had higher recurrence rates, and a trend toward higher high-sensitivity C-reactive protein and serum amyloid A, compared with children with stable or improved arteriopathies.ConclusionsAmong children with AIS, specific inflammatory biomarkers correlate with cause and-in the arteriopathy group-risk of stroke recurrence. Interventions targeting inflammation should be considered for pediatric secondary stroke prevention trials