Effective delivery of drugs to the anterior segment of the eye is notoriously inefficient due to the anatomical barriers in place. Topical administration is the most common method of drug delivery to the anterior segment. When applied to the ocular surface, topical solutions encounter barriers such as lacrimal drainage, rapid tear turnover, and reflex blinking which result in < 5% of instilled therapeutic reaching the intended tissue. One potential method to evade some of these anatomical barriers and improve the delivery of therapeutics is the use of mucoadhesive nanoparticles. These materials are designed to encapsulate a relevant ocular therapeutic and provide a means of maintaining the vehicle on the ocular surface by adhering to the mucin layer of the tear film. To this end, the work presented herein describes the design, characterization, and testing of a novel mucoadhesive polymeric nano-micelle ocular drug delivery system. The base polymer used was selected from a system that has been previously used in the Sheardown Lab. It was composed of poly(D,L-lactide)-block-poly(methacrylic acid-co-3-(acrylamido)phenylboronic acid) (PLA-b-P(MAA-co-3-AAPBA); LMP-20). The formulation was modified to replace the 3-AAPBA monomer, which contains phenyl boronic acid as the mucoadhesive component, with a preactivated thiol monomer (pyridyl disulfide ethyl methacrylate; PDSMA) to generate a novel polymer (LMS-20) to investigate the potential for drug incorporation and mucoadhesion. Modifications of the polymer were made with small thiol molecules cysteamine (Cys; LMC-20), glutathione (GSH; LMG-20), and N-acetyl cysteine (NAC; LMA-20) with a goal of reducing cytotoxicity associated with the 2-pyridinethione leaving group. Synthesis of the PDSMA monomer, LMS-20 and LMP-20 polymers, and modified polymers LMC-20, LMG-20, and LMA-20 were confirmed by 1H NMR. LMA-20 was chosen for further examination as it contained the most relevant thiol modification for ocular applications and was capable of nanoprecipitation to form aqueous micelles with previously developed methods. Micelles were formed from LMA-20 and LMP-20, with spherical morphology as confirmed by TEM. Effective diameters of 64 ± 5 nm and 72 ± 3 nm are reported for LMA-20 and LMP-20, respectively, as confirmed by DLS. Critical micelle concentration for LMA-20 of 217 mg/L was found via a pyrene fluorescence study, significantly lower than the concentration of intended application. LMA-20 and LMP-20 are predicted to be mucoadhesive based on results of zeta-potential studies. However, oscillatory rheology studies were inconclusive based on a negative rheological synergism. LMA-20 micelles loaded with 0.16% (w/w) Cyclosporine-A were able to provide sustained release of drug up to 3 days in vitro. These results suggest the possible future use of these preactivated thiomer-based materials for the delivery of therapeutics to the anterior segment. / Thesis / Master of Applied Science (MASc)

Eye disorders are on the rise as a result of an ageing population, an increasing obesity problem and a growth in the number of diabetic patients. Conventional ophthalmic formulations do not maintain therapeutic drug concentration in the target tissues for a long duration due to the physiological and anatomical eye barriers. Novel delivery systems such as nanoparticles have been explored to enhance the delivery of therapeutic agents to the eye. These delivery systems have in general been assessed using in-vivo animal models, despite ethical concerns for animal wellbeing. The aims of this thesis were to synthesise and characterise four amphiphilic polymers, subsequently prepare and characterise four nano sized polymeric self-assemblies loaded with triamcinolone acetonide (TA), develop an in-vitro porcine eye model and to evaluate the permeation of nano sized self-assemblies using the developed model. Four comb-shaped amphiphilic polymers (Pa5, Pa5-MPEG, Ch5 and Da10) were synthesised with a high yield (>81%) and good reproducibility. These polymers formed spontaneous positive self-assemblies in aqueous media (114-314 nm). The mean hydrodynamic diameters of the positive spontaneous self-assemblies entrapping TA were in the range of 200–334 nm loading high concentrations (455-1263 μg mL-1) of TA, much greater than the TA inherent aqueous solubility or concentrations achieved using conventional solubilisers. A porcine in-vitro eye model was developed to assess drug permeation through anterior and posterior ocular tissues. The model was partially validated using tritiated water and a series of hydrophilic markers with increasing molecular weights. The integrity of porcine ocular tissue was checked by monitoring the permeation of tritiated water to ensure the membrane intactness. Tritiated water permeation at 15 min was exploited as a potential method to normalise drug flux, as tritiated water percentage permeation at 15 min had an inverse relationship with tissue thickness (R2 = 0.66), to reduce the inherent variability between tissue samples thus increasing the accuracy of the in-vitro eye model. Four markers (fluorescein sodium salt, 4, 10 and 20 kDa FITC-dextran) were used for the purpose of investigating the effect of increasing molecular weight on ocular tissue permeability. The permeability of the markers displayed an inverse relationship and abrupt decline with Mw in terms of the permeability through scleral and corneal tissues of human and porcine and the molecular weight of the markers. The developed porcine in-vitro eye model showed good correlation with the human in-vitro model providing strong evidence it can be used to screen potential formulations before testing in-vivo. The TA loaded self-assemblies and a few chemical enhancers (glutamic acid, tween 80, chitosan, Pa5 and elevate temperature (45 °C)), selected to assist drug delivery via two routes (paracellular and transcellular), were tested using the developed in-vitro eye model. The results showed there was no marker permeation enhancement effect in porcine and human ocular tissues using chemical enhancers. In summary, a porcine in-vitro eye model was developed to assess hydrophobic and hydrophilic penetrant permeation across anterior and posterior ocular tissues. The porcine in-vitro eye model showed good correlation with the human in-vitro model providing strong evidence that the porcine in-vitro eye model can be used to screen potential formulations before testing in-vivo using the porcine model which ultimately might correlate well with the in-vivo human responses. Although TA self-assemblies did not significantly increase drug flux through human or porcine scleral tissues, it might be of interest for ophthalmic topically administered formulations due to their positive charge and small nano size.

No description available.

<p>Sight-threatening diseases, such as age-related macular degeneration (AMD), affect the tissues of the posterior segment of the eye. Though modern classes of biomolecular based drugs are therapeutically useful, drug targeting for prolonged bioavailability to pathological sites within the eye is challenging. Current delivery approaches are invasive and lack control over drug release rates and tissue-specific localization. In this thesis, a device using microneedles embedded in a flexible platform was developed that could potentially overcome these challenges.</p> <p>New methods for microneedle fabrication were developed by co-opting simple chemical etch methods commonly used for optical probe fabrication as an alternative to current complex and expensive photolithographic technologies to produce out-of-plane, high aspect ratio microneedles which are often constrained materially to silicon and metal. Microneedles with repeatable tip and taper sizes were obtained using hydrofluoric acid, an organic phase and fused-silica capillary tubing. Microneedles with 10 um tips were made using single and batch mode methods and were then integrated into poly (dimethylsiloxane) (PDMS) for alignment using low cost micromolding approaches offering the same degree of accuracy provided by conventional photolithography<strong>. </strong></p> <p>Single microneedle-based devices successfully delivered rhodamine intrasclerally, intravitreally, suprachoroidally and to the retina. This is the first demonstration of active delivery to specific spatial regions within the posterior eye at controllable rates using a non-implantable, biocompatible device – with minimal fabrication facilities, equipment and cost. The fabricated device demonstrated a new hybrid approach of coupling a rigid microneedle with a soft and pliable substrate that could conform to biological tissues.</p> / Doctor of Philosophy (PhD)

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20810号 / 医博第4310号 / 新制||医||1025(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 清水 章, 教授 萩原 正敏, 教授 松原 和夫 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

<p>While eye drops are a well-accepted and convenient method for ocular drug delivery, they exhibit significant limitations such as poor drug bioavailability, low ocular residence time, pulsatile delivery profiles in the tear fluid as well as the need for patient compliance. Silicone hydrogel (SH) contact lenses have been proposed as alternative ocular drug delivery systems due to their potential for targeted delivery to the corneal surface and high oxygen permeability. The ability of novel hyaluronic acid (HA)-containing silicone hydrogel materials to release timolol maleate (TM), an antiglaucoma drug, or ketotifen fumarate (KF), an anti-histamine administered for ocular allergies, was examined.</p> <p>The releasable wetting and the therapeutic agent were added to the pre-polymer mixture of the SH during synthesis through direct entrapment, while the reaction was performed by UV induced free-radical. The impact of the wetting agent on the swellability, surface wettability, optical transparency and <em>in vitro </em>drug release was studied.</p> <p>Simultaneous drug and wetting agent incorporation resulted in modified SH materials with slightly increased water content and significantly improved surface wettability. In addition, the optical transparency of these materials was not affected by drug loading. However, direct entrapment of HA decreased their optical clarity. <em>In vitro</em> release showed that TM was released over a 14 day period, whereas KF release lasted up to 36 days. For both therapeutic agents used in the current research, non-covalent entrapment of wetting agent and its MW did not significantly change the release kinetics, however the release rate of TM was slowed and controlled by the release of the HA, due to electrostatic interactions between the protonated TM and the anionic HA.</p> <p>The development of SH materials capable of simultaneously releasing a therapeutic and a wetting agent for an extended period of time and in a sustained manner can have a significant potential as extended drug delivery systems for the treatment of front of the eye diseases while also possibly providing comfort during wear.</p> / Master of Applied Science (MASc)

<p>The use of silicon nanoneedles provides a unique and versatile biointerface for a range of biomedical applications. In this work, we propose a rational design for vertical Si nanoneedles that are printed on a polymer substrate for ocular drug delivery, intracellular recording, and intra-organoid sensing. To enable minimally invasive and long-term sustained delivery of ocular drugs, we integrate vertical Si nanoneedles with a tear-soluble contact lens for ocular drug delivery. We demonstrate the effectiveness of this platform in treating corneal neovascularization in an in vivo rabbit model, surpassing the current gold standard surgical therapy. This platform has the potential to revolutionize the management of various chronic ocular diseases without causing significant side effects.</p> <p>To enable intracellular recording, we present a unique platform consisting of vertical Si nanoneedles coated with a thin, transparent network of Au-Ag nanowires. This platform is held in place and enclosed by a soft, transparent elastomer, providing simultaneous intracellular recording and live imaging with applications in neuroscience, cardiology, muscle physiology, and drug screening. To demonstrate the utility of this platform, we monitored electrical potentials from cardiomyocyte cells and cardiovascular organoids. Additionally, we propose an intra-organoid sensing platform with vertical Si nanoneedles transfer printed into a soft scaffold. This platform can be adjusted and tailored for various organoids and tumor tissues of interest, or used to deliver bioactive molecules of interest into organoids in response to external stimuli.</p> <p>Our proposed designs of vertical Si nanoneedles based platforms demonstrate their significant potential for a broad range of biomedical applications, including ocular drug delivery, intracellular recording, and intraorganoid sensing. These platforms have the potential to revolutionize current approaches and pave the way for future developments in biomedical research and clinical applications, offering new possibilities for the diagnosis and treatment of a wide range of diseases.</p>