Shaping surface acoustic waves for cardiac tissue engineering

The heart is a non-regenerating organ that gradually suffers a loss of cardiac cells and functionality. Given the scarcity of organ donors and complications in existing medical implantation solutions, it is desired to engineer a three-dimensional architecture to successfully control the cardiac cells in vitro and yield true myocardial structures similar to native heart. This thesis investigates the synthesis of a biocompatible gelatin methacrylate hydrogel to promote growth of cardiac cells using biotechnology methodology: surface acoustic waves, to create cell sheets. Firstly, the synthesis of a photo-crosslinkable gelatin methacrylate (GelMA) hydrogel was investigated with different degree of methacrylation concentration. The porous matrix of the hydrogel should be biocompatible, allow cell-cell interaction and promote cell adhesion for growth through the porous network of matrix. The rheological properties, such as polymer concentration, ultraviolet exposure time, viscosity, elasticity and swelling characteristics of the hydrogel were investigated. In tissue engineering hydrogels have been used for embedding cells to mimic native microenvironments while controlling the mechanical properties. Gelatin methacrylate hydrogels have the advantage of allowing such control of mechanical properties in addition to easy compatibility with Lab-on-a-chip methodologies. Secondly in this thesis, standing surface acoustic waves were used to control the degree of movement of cells in the hydrogel and produce three-dimensional engineered scaffolds to investigate in-vitro studies of cardiac muscle electrophysiology and cardiac tissue engineering therapies for myocardial infarction. The acoustic waves were characterized on a piezoelectric substrate, lithium niobate that was micro-fabricated with slanted-finger interdigitated transducers for to generate waves at multiple wavelengths. This characterization successfully created three-dimensional micro-patterning of cells in the constructs through means of one- and two-dimensional non-invasive forces. The micro-patterning was controlled by tuning different input frequencies that allowed manipulation of the cells spatially without any pre- treatment of cells, hydrogel or substrate. This resulted in a synchronous heartbeat being produced in the hydrogel construct. To complement these mechanical forces, work in dielectrophoresis was conducted centred on a method to pattern micro-particles. Although manipulation of particles were shown, difficulties were encountered concerning the close proximity of particles and hydrogel to the microfabricated electrode arrays, dependence on conductivity of hydrogel and difficult manoeuvrability of scaffold from the surface of electrodes precluded measurements on cardiac cells. In addition, COMSOL Multiphysics software was used to investigate the mechanical and electrical forces theoretically acting on the cells. Thirdly, in this thesis the cardiac electrophysiology was investigated using immunostaining techniques to visualize the growth of sarcomeres and gap junctions that promote cell-cell interaction and excitation-contraction of heart muscles. The physiological response of beating of co-cultured cardiomyocytes and cardiac fibroblasts was observed in a synchronous and simultaneous manner closely mimicking the native cardiac impulses. Further investigations were carried out by mechanically stimulating the cells in the three-dimensional hydrogel using standing surface acoustic waves and comparing with traditional two-dimensional flat surface coated with fibronectin. The electrophysiological responses of the cells under the effect of the mechanical stimulations yielded a higher magnitude of contractility, action potential and calcium transient

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals

Biomimetic Based Applications

The interaction between cells, tissues and biomaterial surfaces are the highlights of the book "Biomimetic Based Applications". In this regard the effect of nanostructures and nanotopographies and their effect on the development of a new generation of biomaterials including advanced multifunctional scaffolds for tissue engineering are discussed. The 2 volumes contain articles that cover a wide spectrum of subject matter such as different aspects of the development of scaffolds and coatings with enhanced performance and bioactivity, including investigations of material surface-cell interactions

Exclusive Papers of the Editorial Board Members (EBMs) of the Materials Chemistry Section of Molecules

The book is intended to collect the recent contributions (either research or review papers) to the development of the “Materials Chemistry” research fields by the Editorial Board Members of the Materials Chemistry Section of Molecules. The aim is to present the recent progress in the fields and to highlight the key role of Materials Chemistry in a multidisciplinary research context

Application of microneedles for the treatment of nodular basal cell carcinoma

Basal cell carcinoma (BCC) is one the most common skin cancer in humans. One of the most efficacious drugs used in treating BCC is imiquimod, which is available as a topical cream, AldaraTM. Nevertheless, the drug has limited cutaneous permeation limiting its use only for the management of superficial BCC. The work presented in this thesis explored the utility of microneedles as a drug delivery platform for the intradermal delivery of imiquimod for the treatment of nodular BCC. This was achieved by first comparing the insertion profiles of two commercial microneedle systems, the DermastampTM and Dermapen®. It was discovered that the oscillating microneedle system, the Dermapen® required less force than the Dermastamp™ to puncture the skin while resulting in deeper insertion in ex vivo skin tissue to a depth needed to treat nodular BCC. Moving forward, the effectiveness of the Dermapen® to improve the delivery of imiquimod into the skin was investigated. It was discovered that post-treatment of the skin with the Dermapen® after AldaraTM application, known as “patch-and-poke”, enhanced the intradermal delivery of imiquimod generating a depot that that persisted for up to 24 hours. However, such enhancement was not achieved when a “poke-and-patch” strategy was adopted, where skin was pre-treated with the Dermapen® prior to cream application. Despite the effectiveness of the “patch-and-poke” strategy in delivering imiquimod intradermally, this approach may not be acceptable by patients owing to the two-step nature of the treatment. In order to overcome this limitation a one-step drug delivery strategy utilising dissolving polymeric microneedles was explored. This was achieved by fabricating a dissolving microneedle system out of the commercial PVPVA polymer, Kollidon® VA 64. The dissolving microneedle system demonstrated the capability of delivering similar quantities of imiquimod but into the deeper layers of the skin, despite a 6-fold lower drug loading, relative to the current clinical dose of Aldara™ cream used in BCC treatment. Furthering this, a series of polymeric microneedles of different designs and polymer chemistries were manufacture from pAMPS, pNAM and pHEAM that were synthesised via free radical polymerisation reactions. Drug release studies into ex vivo porcine skin tissues and ex vivo patient BCC tumours demonstrated that the pNAM obelisk microneedle patches were capable of achieving higher intradermal delivery of imiquimod relative to the commercial cream, AldaraTM. In addition, an in vivo tumour efficacy study using a mouse model for skin tumours highlighted that the microneedle patches were capable of slowing down tumour growth. Lastly, this thesis demonstrated the analytical capability offered by time-of-flight secondary ion mass spectrometry (ToF-SIMS) in evaluating the effectiveness of microneedle-based drug delivery systems. This is exemplified by the ability of the instrument to track the dermal distribution of active (imiquimod) and excipients (polymers and surfactant) from different formulations within biological tissues in a label free fashion. Such unprecedented analysis enabled us to demonstrate active-excipient colocalisation thus expanding our mechanistic insight on how such delivery systems behave upon administration into the skin. Overall, this thesis expanded our knowledge on how some microneedle systems are capable of achieving enhanced intradermal delivery while highlighting the viability of this drug delivery platform for the treatment of nodular BCC in a minimally invasive fashio

Application of microneedles for the treatment of nodular basal cell carcinoma

Basal cell carcinoma (BCC) is one the most common skin cancer in humans. One of the most efficacious drugs used in treating BCC is imiquimod, which is available as a topical cream, AldaraTM. Nevertheless, the drug has limited cutaneous permeation limiting its use only for the management of superficial BCC. The work presented in this thesis explored the utility of microneedles as a drug delivery platform for the intradermal delivery of imiquimod for the treatment of nodular BCC. This was achieved by first comparing the insertion profiles of two commercial microneedle systems, the DermastampTM and Dermapen®. It was discovered that the oscillating microneedle system, the Dermapen® required less force than the Dermastamp™ to puncture the skin while resulting in deeper insertion in ex vivo skin tissue to a depth needed to treat nodular BCC. Moving forward, the effectiveness of the Dermapen® to improve the delivery of imiquimod into the skin was investigated. It was discovered that post-treatment of the skin with the Dermapen® after AldaraTM application, known as “patch-and-poke”, enhanced the intradermal delivery of imiquimod generating a depot that that persisted for up to 24 hours. However, such enhancement was not achieved when a “poke-and-patch” strategy was adopted, where skin was pre-treated with the Dermapen® prior to cream application. Despite the effectiveness of the “patch-and-poke” strategy in delivering imiquimod intradermally, this approach may not be acceptable by patients owing to the two-step nature of the treatment. In order to overcome this limitation a one-step drug delivery strategy utilising dissolving polymeric microneedles was explored. This was achieved by fabricating a dissolving microneedle system out of the commercial PVPVA polymer, Kollidon® VA 64. The dissolving microneedle system demonstrated the capability of delivering similar quantities of imiquimod but into the deeper layers of the skin, despite a 6-fold lower drug loading, relative to the current clinical dose of Aldara™ cream used in BCC treatment. Furthering this, a series of polymeric microneedles of different designs and polymer chemistries were manufacture from pAMPS, pNAM and pHEAM that were synthesised via free radical polymerisation reactions. Drug release studies into ex vivo porcine skin tissues and ex vivo patient BCC tumours demonstrated that the pNAM obelisk microneedle patches were capable of achieving higher intradermal delivery of imiquimod relative to the commercial cream, AldaraTM. In addition, an in vivo tumour efficacy study using a mouse model for skin tumours highlighted that the microneedle patches were capable of slowing down tumour growth. Lastly, this thesis demonstrated the analytical capability offered by time-of-flight secondary ion mass spectrometry (ToF-SIMS) in evaluating the effectiveness of microneedle-based drug delivery systems. This is exemplified by the ability of the instrument to track the dermal distribution of active (imiquimod) and excipients (polymers and surfactant) from different formulations within biological tissues in a label free fashion. Such unprecedented analysis enabled us to demonstrate active-excipient colocalisation thus expanding our mechanistic insight on how such delivery systems behave upon administration into the skin. Overall, this thesis expanded our knowledge on how some microneedle systems are capable of achieving enhanced intradermal delivery while highlighting the viability of this drug delivery platform for the treatment of nodular BCC in a minimally invasive fashio

Ionophoric and aptameric recognition-modulated electroactive polyaniline films for the determination of tetrodotoxin

Philosophiae Doctor - PhDTetrodotoxin (TTX) is a nonpeptidic neurotoxin with a high rate of food poisoning mortality (60%) that has been associated with the consumption of diets from puffer fish and mud snails harbouring TTX-producing bacteria. As this neurotoxin has no known antidote and could not be mitigated by cooking, the only way for safety appears to be the detection of TTX-contaminated fishes at the points of harvest and control. The overall aim of this study was to develop amperometric and impedimetric sensors for TTX based on ionophores and aptamer immobilised on the modified conducting electroactive polyaniline (PANI)/electrode. The undoped polyaniline and poly(4-styrenesulfonic acid) (PSSA) doped electroactive polyanilines were prepared in perchloric acid/acetonitrile and phosphoric acid respectively by electrochemical oxidative polymerisation. Two types of electropolymerisation were applied to prepare the neutral and p-doped PANI−PSSA films composites. The dynamic electroinactivity of TTX was studied which revealed that TTX is not electrochemically active on bare Au, GC, Pt, PG, Ni, Ti and BDD (Boron dopeddiamond) electrodes in acetate buffer pH 4.8. Using ion transfer voltammetry and UV-Vis analysis, the complexation of TTX with two neutral ionophores (sodium ionophore X (NaX) and dibenzo-18-crown6 (B18C6)) was investigated. The cyclic voltammograms (CVs) recorded from ion transfer voltammetry presented no redox peak and no increasing/decreasing current was observed which indicates that no TTX ions transfer from the liquid to the organic phase. In addition, the absorption spectra of the mixture of TTX/NaX and TTX/B18C6 presented the same absorption bands recorded for NaX and B18C6 respectively. Three absorptions bands at 250.4, 278.3, and 370.6 nm for NaX and two at 222.03 and 274.10 nm for B18C6 were observed before and after mixing TTX with NaX and TTX with B18C6 separately. No chemical reaction occurred between the TTX and both ionophores, therefore, sodium ionophore X and dibenzo-18-crown-6 did not form a complex with TTX. Thus, TTX ion sensor cannot be developed based on these two neutral compounds. The electrodynamics of the PANI and PANI−PSSA films electropolymerised on the bare precious metal electrodes were also investigated through various electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies in sodium phosphate (SPB) and acetate (OAc) buffer revealed that both neutral and p-doped films synthesized were thin (thickness L < 5 nm in acetate buffer and L < 10 nm in sodium phosphate buffer) film polymers