Browsing by Author "Hackl, E. V."
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Item Open Access Application of Texture Analysis technique in formulation development of lyophilized orally disintegrating tablets containing mannitol, polyvinylpyrrolidone and amino acids(Springer, 2019-01-10) Hackl, E. V.; Ermolina, I.Orally disintegrating tablets (ODTs) attract a great attention as this easy swallowing dosage form often improves patient compliance. In the current work, orally disintegrating tablets comprising mannitol, polyvinylpyrrolidone (PVP) and an amino acid (alanine, glycine or serine) with various PVP-to-amino acid ratios were formulated. The combination of mannitol and an amino acid was aimed to use the advantages of mannitol, the matrix-supporting and disintegration agent, and to reduce the total amount of sugar/polyol in tablets. Tablets were manufactured by freeze-drying and their properties (appearance, internal structure, disintegration, mechanical and texture properties, moisture uptake, shrinkage, thermal properties) were assessed. In the work, great emphasis was placed on illustrating the applicability of the Texture Analysis of the freeze-dried cakes directly in vials in formulation development. The results show that the appearance, mechanical properties, disintegration and shrinkage of the freeze-dried ODTs depend significantly on the excipient composition with PVP playing the leading role. Partial mannitol replacement with an amino acid has a limited impact on the tablet properties. The presence of an amino acid also has no impact on the PVP-mannitol interaction. The mechanical and texture properties of freeze-dried ODTs depend non-linearly on the PVP content. The transition between the different types of textures occurs in a narrow range of PVP concentrations regardless of the type of amino acid in a formulation. The non-linear effect of PVP on various tablet properties should be taken into account when designing ODT formulations as it can compromise the robustness of the manufacturing process.Item Open Access Effect of acidic and basic pH on Thioflavin T absorbance and fluorescence(Springer, 2015-03-22) Hackl, E. V.; Darkwah, Joseph; Smith, Geoff; Ermolina, I.Thioflavin T (ThT) is a fluorescent dye able to enhance significantly its fluorescence quantum yield upon binding to protein amyloids. ThT assay is widely used to detect and quantify amyloids in a variety of conditions, including solutions with different pH levels. In the present work, the effect of acidic and basic pH on the conformation of the ThT molecule and its absorption and fluorescence properties was studied. The results show that both acidic and basic pH decrease significantly the intensity of ThT absorption in the visible region and fluorescence emission intensity. Low pHs induce an immediate “all-or-nothing” decrease in the ThT signal, while in alkaline solutions the ThT signal decreases gradually over time. pH-induced signal quenching is less in the presence of glycerol or protein aggregates. Two different mechanisms are responsible for the ThT signal quenching—the ThT hydroxylation at basic pH and protonation of the nitrogen atom of the dimethylamino group at acidic pH. ThT assays should be carefully carried out at basic or acidic pH as strong pH dependence of ThT could be responsible for misinterpretation and false positive/negative experimental results. The potential unsuitability of ThT as a probe in solutions with high pH (>9) has been shown. © 2015, European Biophysical Societies' Association.Item Open Access Effect of arginine on the aggregation of protein in freeze-dried formulations containing sugars and polyol. 1. Formulation development(Springer, 2017-10-18) Hackl, E. V.; Darkwah, Joseph; Smith, Geoff; Ermolina, I.L-arginine was introduced into protein-based freeze-dried formulations to study the ability of arginine to reduce / prevent from protein aggregation during manufacturing, storage and reconstitution of lyophilized protein-based pharmaceuticals. As L-arginine is known to be very hygroscopic, additional excipients which could provide a moisture buffering capacity need to be introduced into the formulation. In the first part of our study – excipient formulation development – the screening of a number of sugars/polyols has been done in order to select the best combination of excipients that, in a complex with L-arginine, can i) produce freeze-dried cakes with elegant appearance, adequate mechanical properties and reconstitution times, and ii) resist/minimize the moisture sorption. Various freeze-dried cakes containing L-arginine in combination with mannitol, trehalose, lactose, and sucrose were produced and analyzed by TGA, DSC, texture analysis, moisture sorption, cake shrinkage, TVIM and SEM. The non-linear dependencies of the physicochemical properties of the freeze-dried cakes on the sugar-to-mannitol ratios were found. The best combinations of excipients (L-arginine, mannitol and trehalose) were selected to be used in the second part of this work, in which the impact of each selected formulation will be studied in relation to the aggregation of a protein.Item Open Access Effect of Arginine on the Aggregation of Protein in Freeze-Dried Formulations Containing Sugars and Polyol: II. BSA Reconstitution and Aggregation(Springer, 2018-07-06) Hackl, E. V.; Darkwah, Joseph; Smith, Geoff; Ermolina, I.The current paper continues our study on the ability of L-arginine to prevent/reduce the aggregation of proteins that results from the various stresses during the lyophilisation and/or storage of lyophilized protein-based products. The first part of our study, i.e. formulation development, was devoted to the rational design and optimization of an L-arginine containing lyophilized formulation which can resist the natural tendency of L-arginine to absorb atmosphere moisture. Mannitol and trehalose were chosen among other excipients to be included in the protein-based formulation, as mannitol in a combination with L-arginine has been shown to reduce moisture sorption while trehalose provides a degree of lyoprotection. In the present study, a number of formulations, which comprised bovine serum albumin (BSA) with and without L-arginine, and with five different ratios of trehalose-to-mannitol (from 30:70 to 80:20) were lyophilised and assessed. The internal structures and the moisture sorption/retention of the lyophilized formulations were characterised. To study the effect of L-arginine on BSA solid-phase stability, the lyophilized powder was exposed to accelerated storage conditions (high moisture (75% RH) and temperature (22 or 45 °C)) for up to 24 h. The lyophilized BSA formulations were then reconstituted and solution-state protein aggregation assessed by turbidimetry at 360 nm and fluorescence spectroscopy using the thioflavin T assay. It was demonstrated that L-arginine can be used in protein-based freeze-dried formulations to significantly reduce the aggregation of protein during the manufacturing, storage and subsequent reconstitution. The results also revealed the importance of a sufficient amount of mannitol in the arginine-containing formulations.Item Open Access Evaluation of water properties in HEA-HEMA hydrogels swollen in aqueous-PEG solutions using thermoanalytical techniques(Springer, 2015-02-17) Hackl, E. V.; Khutoryanskiy, Vitaliy V.; Tiguman, Gustavo M. B.; Ermolina, I.Abstract Hydrogels are polymeric materials used in many pharmaceutical and biomedical applications due to their ability to form 3D hydrophilic polymeric networks, which can absorb large amounts of water. In the present work, polyethylene glycols (PEG) were introduced into the hydrogel liquid phase in order to improve the mechanical properties of hydrogels composed of 2-hydroxyethylacrylate and 2-hydroxyethylmethacrylate (HEA–HEMA) synthesized with different co-monomer compositions and equilibrated in water or in 20 % water–PEG 400 and 600 solutions. The thermoanalytical techniques [differential scanning calorimetry (DSC) and thermogravimetry (TG)] were used to evaluate the amount and properties of free and bound water in HEA–HEMA hydrogels. The internal structure and the mechanical properties of hydrogels were studied using scanning electron microscopy and friability assay. TG ‘‘loss-on-drying’’ experiments were applied to study the water-retention properties of hydrogels, whereas the combination of TG and DSC allowed estimating the total amount of freezable and non-freezing water in hydrogels. The results show that the addition of viscous cosolvent (PEG) to the liquid medium results in significant improvement of the mechanical properties of HEA–HEMA hydrogels and also slightly retards the water loss from the hydrogels. A redistribution of free and bound water in the hydrogels equilibrated in mixed solutions containing 20 vol% of PEGs takes place.Item Open Access Hydrogels based on copolymers of 2-hydroxyethylmethacrylate and 2-hydroxyethylacrylate as a delivery system for proteins: interactions with lysozyme(Wiley, 2017-01-28) Hackl, E. V.; Khutoryanskiy, Vitaliy V.; Ermolina, I.Hydrogels have attracted considerable attention due to numerous applications, in particular as contact lenses and carriers for sustained drug delivery. The aim of the present work is to characterize the interactions of copolymer hydrogels consisted of 2-hydroxyethylmethacrylate (HEMA) and 2-hydroxyethylacrylate (HEA) with a small protein (lysozyme) and to assess the potential applications of these hydrogels as a drug delivery system for sustained release of protein-based therapeutics. Physicochemical properties of protein-loaded hydrogels, as well as lysozyme in vitro loading and release and the conformation of the protein released from hydrogels were studied. The effect of copolymer composition on the protein deposition on hydrogels and protein aggregation in the presence of hydrogels was also assessed. The results show that introduction of HEA into the copolymeric hydrogels enhances their suitability as a delivery system for proteins. Copolymerisation of HEMA and HEA allows controlling the physicochemical properties of hydrogels and the protein release rate.Item Embargo Inclusion by design: Embedding inclusive teaching practice into design and preparation of laboratory classes(Elsevier, 2019-11-02) Ermolina, I.; Hackl, E. V.Introduction: Creation of an inclusive learning environment and provision of individual adjustments are duties of higher education providers. However, laboratory practical teaching is not always inclusive beyond general university requirements. Lab classes can present many barriers to disabled learners. Proactive adjustments embedded into the design and preparation of laboratory classes can make lab-based teaching as inclusive and accessible as possible. Perspective: The main challenges, difficulties, and barriers experienced by students with disabilities during laboratory classes were identified and analysed. A review of a large number of sources was conducted, and the best available evidence of inclusive practice in science and medicine laboratories (including those already implemented in the Reading School of Pharmacy and Leicester School of Pharmacy) were retrieved, critically appraised, and summarized. Recommendations on embedding inclusive practices into the design and preparation of laboratory classes were developed, including methods for making the following accessible: (1) printed materials, such as handouts, instructions, notes, etc.; (2) video files; and (3) colours. Additionally, the use of a range of pedagogic techniques and assistive technologies in inclusive teaching is discussed. Implications: We have developed general accessibility guides and provided laboratory teaching staff with examples of good inclusive teaching practice. Active implementation of the inclusiveby- design approach, in contrast to inclusive-on-request, can be beneficial for both learners and teaching staff since inclusion-by-design helps to establish a lasting inclusive culture in teaching laboratories.Item Metadata only Interaction of polypeptide antibiotic gramicidin S with platelets(Wiley, 2012) Hackl, E. V.; Berest, V. P.; Gatash, S. V.Item Open Access Using Texture Analysis technique to assess the freeze-dried cakes in vials.(Elsevier, 2016-06-09) Hackl, E. V.; Ermolina, I.A freeze-dried (FD) cake should possess, among others properties, a sufficient dryness and strength to prevent cracking or powdering during transportation and storage. In the present work the application of a standard Texture Analysis (TA) technique to study the mechanical properties of the FD cakes directly in glass vials used for freeze-drying has been demonstrated. Examining the FD cakes in glass vials has many advantages as it allows studying the intact FD cakes minimizing the bias from texture distortion during samples preparation, and reducing the moisture uptake. A procedure allowing quantitative assessment of the strength, fracturability and elastic properties of the FD cakes using Texture Analysis has been developed. The results show that the TA method is sensitive to the variations in cake materials, storage conditions (temperature, excessive moisture) and cake quality. The results also show that TA can also be applied for optimization / improvement of the freeze-drying protocols and rapid disintegrating tablet formulation development. The simplicity of the Texture Analysis technique and a number of different probes available on the market allow using the TA for the routine reliable and robust tests of freeze-dried solids providing valuable information on the strength and texture of the cakes.