The design and analysis of sugar-based carrier systems for the protection of nucleic acids

The overall aim of the work detailed in this thesis was to design and analyse sugar-based (trehalose, raffinose and sucrose) carrier systems for the protection of naked plasmid DNA formulations generated by spray drying. Trehalose exists in multiple crystalline anhydrous and hydrated forms and is thought to exist in two different amorphous forms. Reported thermal transitions of trehalose dihydrate vary with environmental conditions and particle size. The first area of this thesis focused on investigating the inter-conversion properties of trehalose dihydrate to observe if an in-depth understanding of its physical properties will provide an insight into its bio-protective properties. Within this area, two standardised forms of α,α-trehalose dihydrate were generated and characterised by performing a series of thermal, spectroscopic and X-ray diffraction techniques. This resulted in the identification of an intermediary anhydrous form. Within the second area of this thesis the use of the fragility parameter m and the strength parameter D as predictors of amorphous stability of generated co-spray dried sucrose-raffinose and sucrose-trehalose samples was investigated. Results showed addition of both raffinose and trehalose improved predicted amorphous stability, with the greatest effect seen at highest additive concentrations. The third area of the thesis was to evaluate the degree of degradation of plasmid DNA spray dried in the presence of amorphous sugars. Spray-drying can be used to develop biopharmaceutical particles for the pulmonary delivery. However, it runs the risk of loss of biological activity, sample instability as well as thermal degradation of the biopharmaceutical. Results showed that plasmid DNA degradation was reduced when co-spray dried in the presence of raffinose and to a greater extent with trehalose. Co-spray drying of plasmid DNA in the presence of sucrose, sucrose-raffinose and sucrose-trehalose formulations offered less protection than trehalose and raffinose. Overall, two key messages are concluded from the work detailed in this thesis. Firstly, the thermal transitions of trehalose dihydrate can be influenced by environmental factors as well as inter-batch variability. This can affect authenticity of polymorphous and amorphous forms identified. Secondly, addition of raffinose and trehalose to amorphous sucrose formulations improved the predicted amorphous stability of the formulations however; these co-spray dried samples offered less protection compared to plasmid DNA co-spray dried in the presence of trehalose and raffinose alone

Solid microcrystalline dispersion films as a new strategy to improve the dissolution rate of poorly water soluble drugs: a case study using olanzapine

In this study, we evaluate the dissolution rate enhancement of solid microcrystalline dispersion (SMD) films of olanzapine (OLZ) formulated with four water-soluble polymers namely poly(N-vinylpyrrolidone) (PVP), poloxamer 188 (P188), poloxamer 407 (P407) and Soluplus(®) (SLP). Prepared formulations were characterised to determine particle size, morphology, hydrogen bonding interactions, thermal characteristics as well as in vitro dissolution studies conducted under sink conditions (pH 6.8). Particle size of OLZ in all formulations ranged between 42 and 58μm. Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR), Differential Scanning Calorimetry (DSC) and Hot-Stage Microscopy (HSM) studies confirmed OLZ was well maintained in its crystalline state during the formulation process. In vitro dissolution studies showed immediate drug release from all formulation when compared to the drug alone. The greatest increase in in vitro dissolution rate was observed in formulations containing P188 most likely due to its enhanced hydrophilic and surfactant properties compared to the other agents used. Overall, this study successfully generated OLZ loaded SMD films with improved in vitro dissolution rates which is highly likely to result in improved oral bioavailability in vivo

Solubility–spinnability map and model for the preparation of fibres of polyethylene (terephthalate) using gyration and pressure

AbstractThe selection of a solvent or a solvent system is a fundamental and a crucial step in spinning fibres using a selected process. Solvent selection determines the critical minimum polymer concentration and the critical minimum chain entanglement which allows the spinning of nanofibres rather than other hybrid morphologies such as beaded structures. Pressurised gyration, which simultaneously combines the use of gas pressure and rotation, is used as the processing and forming route for spinning fibres in this work. This study investigates 23 different solvents and solvent systems spread on a wide area of a Teas graph and able to dissolve the functional polymer polyethylene (terephthalate) (PET) and spin products by the application of pressurised gyration. The results are mapped on a Teas graph to identify the solubility–spinnability region. Based on this solubility–spinnability region, various solvents and binary solvent systems that allow the making of PET fibres are suggested. Scaling laws for the relationship between polymer concentration and specific viscosity are identified. The structural evolution in the fibres prepared is elucidated. For the first time, a mathematical model to scale fibre diameter with respect to flow properties and processing parameters encountered in pressurised gyration has been successfully developed

pH Alteration in Plant-Mediated Green Synthesis and Its Resultant Impact on Antimicrobial Properties of Silver Nanoparticles (AgNPs)

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)Plant-mediated green synthesis is a cost-effective and eco-friendly process used to synthesize metallic nanoparticles. Experimental pH is of interest due to its ability to influence nanoparticle size and shape; however, little has been explored in comparison to the influence of this parameter on the therapeutic potential of resultant metallic nanoparticles. Our work investigated the influence of pH alternation on antimicrobial properties of plant-mediated green synthesized (using Spinacia oleracea leaf extract) silver nanoparticles. We further investigated if the antimicrobial activity was sustained at 8 weeks (after initial green synthesis). Antimicrobial properties were evaluated against Escherichia coli, Staphylococcus aureus, and Candida albicans. Our work confirmed that experimental pH in plant-mediated green synthesis of silver nanoparticles influenced their resultant antimicrobial properties. Silver nanoparticles generated at experimental pH 4.5, and nine showed activity against E. coli which was sustained at various levels over 8 weeks. No antimicrobial activity was observed against S. aureus, and weak antimicrobial activity against C. albicans. These interesting findings highlight the importance of experimental pH. Further understanding of the role experimental pH plays on resultant metallic nanoparticle properties as it relates to biological and therapeutic impact is required, which will have an impact on wider applications beyond antimicrobial activity.Peer reviewe

Nanofibres in Drug Delivery

In recent years there has been an explosion of interest in the production of nanoscale fibres for drug delivery and tissue engineering. Nanofibres in Drug Delivery aims to outline to new researchers in the field the utility of nanofibres in drug delivery, and to explain to them how to prepare fibres in the laboratory. The book begins with a brief discussion of the main concepts in pharmaceutical science. The authors then introduce the key techniques that can be used for fibre production and explain briefly the theory behind them. They discuss the experimental implementation of fibre production, starting with the simplest possible set-up and then moving on to consider more complex arrangements. As they do so, they offer advice from their own experience of fibre production, and use examples from current literature to show how each particular type of fibre can be applied to drug delivery. They also consider how fibre production could be moved beyond the research laboratory into industry, discussing regulatory and scale-up aspects

Evaluating thermogravimetric analysis for the measurement of drug loading in mesoporous silica nanoparticles (MSNs)

In this study, a thermogravimetric analysis (TGA) method for measuring the drug loading in mesoporous silica nanoparticles (MSNs) has been developed and evaluated in comparison with the drug loading quantification by high-performance liquid chromatography (HPLC). Indapamide was loaded into two different types of MSNs, namely Mobile Crystalline Material (MCM-41, pore size = 1.2 nm) and Santa Barbara Amorphous (SBA-15, pore size = 4.1 nm). Physical mixtures of the drug and silica gave a linear correlation between the observed and expected drug content for both TGA and HPLC, which were used for calibration purposes. The limit of detection (LOD) for the TGA method obtained from the physical mixture calibration curve was 0.77 % (w/w) and the r² value was 0.9936, whereas the HPLC had a LOD of 0.06 % (w/w) and an r² value of 0.9933. The sensitivity of the TGA method was well established using the drug loading studies, as it can detect the low loading of MCM-41 at 2.2 ± 0.21 % (w/w), compared to 5.1 ± 0.12 % (w/w) with the SBA-15. In all samples applied, the multiple comparison analysis showed an insignificant difference between the two methods (p > 0.05). The TGA data presented good evidence for using this technique as a sensitive, cost-effective, and low-variable quantitative analysis in the drug loading determination of the MSNs. TGA is not a selective method of quantification, but optimising the method using the pure and blank samples of MSNs and drug can significantly improve the sensitivity. This work provides a unique approach to apply TGA as a selective and more favourable method to characterise MSNs to do early formulation developments

Thermal Behavior of Benzoic Acid/lsonicotinamide Binary Cocrystals

A comprehensive study of the thermal behavior of the 1:1 and 2:1 benzoic acid/isonicotinamide cocrystals is reported. The 1:1 material shows a simple unit cell expansion followed by melting upon heating. The 2:1 crystal exhibits more complex behavior. Its unit cell first expands upon heating, as a result of C–H···π interactions being lengthened. It then is converted into the 1:1 crystal, as demonstrated by significant changes in its X-ray diffraction pattern. The loss of 1 equiv of benzoic acid is confirmed by thermogravimetric analysis–mass spectrometry. Hot stage microscopy confirms that, as intuitively expected, the transformation begins at the crystal surface. The temperature at which conversion occurs is highly dependent on the sample mass and geometry, being reduced when the sample is under a gas flow or has a greater exposed surface area but increased when the heating rate is elevated

Mucoadhesion of Progesterone-Loaded Drug Delivery Nanofiber Constructs

Mucoadhesive delivery systems have attracted remarkable interest recently, especially for their potential to prolong dosage form resident times at sites of application such as the vagina or nasal cavity, thereby improving convenience and compliance as a result of less frequent dosage. Mucoadhesive capabilities need to be routinely quantified during the development of these systems. This is however logistically challenging due to difficulties in obtaining and preparing viable mucosa tissues for experiments. Utilizing artificial membranes as a suitable alternative for quicker and easier analyses of mucoadhesion of these systems is currently being explored. In this study, the mucoadhesive interactions between progesterone-loaded fibers (with varying carboxymethyl cellulose (CMC) content) and either artificial (cellulose acetate) or mucosa membranes are investigated by texture analysis and results across models are compared. Mucoadhesion to artificial membrane was about 10 times that of mucosa, though statistically significant (p = 0.027) association between the 2 data sets was observed. Furthermore, a hypothesis relating fiber–mucosa interfacial roughness (and unfilled void spaces on mucosa) to mucoadhesion, deduced from some classical mucoadhesion theories, was tested to determine its validity. Points of interaction between the fiber and mucosa membrane were examined using atomic force microscopy (AFM) to determine the depths of interpenetration and unfilled voids/roughness, features crucial to mucoadhesion according to the diffusion and mechanical theories of mucoadhesion. A Kendall’s tau and Goodman–Kruskal’s gamma tests established a monotonic relationship between detaching forces and roughness, significant with p-values of 0.014 and 0.027, respectively. A similar relationship between CMC concentration and interfacial roughness was also confirmed. We conclude that AFM analysis of surface geometry following mucoadhesion can be explored for quantifying mucoadhesion as data from interfacial images correlates significantly with corresponding detaching forces, a well-established function of mucoadhesion