Nature provides fascinating examples of functional materials with hierarchical structures. Nano and microscale materials have been prepared by synthetic approaches via the self-assembly of discrete building blocks with the aim to mimic nature’s materials in complexity and size. The solution-state self-assembly of block copolymers (BCPs) with crystallizable core-forming blocks has enabled access to low curvature morphologies such as 1D and 2D micelles via a spontaneous nucleation method termed crystallization-driven self-assembly (CDSA). Via a seeded growth method known as living CDSA, 1D and 2D micelles of controlled dimensions and low dispersity can easily be prepared. However, due to the challenges associated with the synthesis of high aspect ratio nanoparticles and the low number of noncytotoxic polymers known to undergo CDSA, their use for biomedical applications has been limited. The aim of the work described in this thesis is to develop nanofibers of precise dimensions, with nontoxic materials, for potential biomedical applications such as drug delivery, tissue engineering and materials reinforcement. Chapter 1 describes how nature makes superb functional hierarchical materials that serve as inspiration for the development of synthetic methods for the preparation of nano and microstructures. The principles regarding the solution-state self-assembly of BCPs with amorphous or crystalline core-forming blocks are discussed. The preparation of length-controlled nanostructures, segmented micelles, and supermicelles via living CDSA and micelle self-assembly are presented. An introduction to nanoparticle drug delivery, materials reinforcement, and tissue engineering with emphasis on the development and advantages of high aspect ratio nanofibers is given. Finally, a brief perspective on the development of nanofiber-based therapeutics is provided. Chapter 2 discusses the preparation of coaxial-core core nanofibers from the self-assembly of triBCPs. The nanofiber structure is comprised of a crystalline inner core, an amorphous hydrophobic outer core, and a water-soluble corona-forming block. Encapsulation of a model hydrophobic molecule was achieved by the outer amorphous core. This represents the first example of water-soluble, length-controlled, and low length-dispersity (Ð) nanofibers loaded via non-covalent interactions. In Chapter 2, preliminary studies suggested cargo uptake by diBCP nanofibers may be possible. Chapter 3 focusses on investigating the non-covalent loading of length controlled diBCP nanofibers with a hydrophobic cargo. The effect of the chemical identity and the length of the corona-forming blocks was also studied. Chapter 4 describes the self-assembly of B-A-B triBCPs with crystallizable hydrophobic ‘B’ terminal segments to yield fiber-like micelle networks and their potential applications. Conditions for the preparation of discrete crystalline core flower-like micelles and intermicellar fiber-like networks of crystalline core nanofibers were investigated. For the first time, crystalline core nanofiber networks are reported. Chapter 5 focuses on the proof-of-concept development of water-soluble length-controlled nanofibers with corona-forming blocks capable of targeting specific cancer tissue. Additionally, segmented nanofibers for drug delivery applications were prepared. Finally, the association of curcumin with the nanofiber corona-forming block was briefly investigated. Chapter 6 summarizes the work presented in this thesis which contributes towards the development of length-tunable nanofibers for biomedical applications and outlines future research directions of the work presented. / Graduate / 2023-04-20

Interest within the healthcare profession in transdermal delivery of pharmaceuticals through passive, mechanical (phonophoresis) or electromotive (iontophoresis) forces has increased significantly throughout the past decade. The current review will examine the histology and cellular biology of the integument system as related to regulation of transcutaneous delivery of pharmaceutics, and examine currently accepted mechanism(s) of iontophoretic delivery. Additionally, a survey of current iontophoretic devices and electrodes available within the U.S. market, and the limitations of current technology will be presented. Experimental research supporting the use of iontophoresis for local delivery of pharmaceuticals will also be presented in conjunction with the outcomes of clinical investigations where iontophoresis was utilized for the local delivery of these pharmaceuticals. Topic areas to be covered within this section include iontophoresis of antibiotics into integument wounds, local anesthetics, and steroidal and nonsteroidal anti- inflammatory drugs. Finally, an examination of the benefits of combining various forces to enhance transcutaneous drug delivery and future direction(s) of research within this field will be discussed. The purpose of the present review is to provide both researchers and clinical practitioners with an objective basis for the current use of iontophoresis in rehabilitation medicine.

Background and Purpose. Iontophoresis is a process that uses bipolar electric fields to propel molecules across intact skin and into underlying tissue. The purpose of this study was to describe and experimentally examine an iontophoresis drug delivery model. Subjects and Methods. A mechanistic model describing delivery was studied in vitro using agarose gels and was further tested in vivo by evaluation of cutaneous vasoconstriction following iontophoresis in human volunteers. Results. In vitro cathodic iontophoresis at 4 mA and 0.1 mA each delivered dexamethasone/dexamethasone phosphate (DEX/DEX-P) from a 4-mg/mL donor solution to a depth of 12 mm following a 40 mA·minute stimulation dosage. Delivery of DEX/DEX-P to at least the depths of the vasculature in humans was confirmed by observation of cutaneous vasoconstriction. This cutaneous vasoconstriction was longer lasting and greater in magnitude when using low-current, long-duration (∼0.1 mA) iontophoresis compared with equivalent dosages delivered by higher-current, shorter-duration (1.5-4.0 mA) iontophoresis. Discussion and Conclusion. From data gathered with the gel model, the authors developed a model of a potential mechanism of drug depot formation following iontophoresis. The authors believe this drug depot formation to be due to exchange of drug ions for chloride ions as the ionic current carriers. Furthermore, diffusion, not magnitude of current, appears to govern the depth of drug penetration. Although the authors did not address the efficacy of the drug delivered, the results of human experiments suggest that current magnitude and duration should be considered as factors in treating musculoskeletal dysfunctions with iontophoresis using DEX/DEX-P at a concentration of 4 mg/mL. [Anderson CR, Morris RL, Boeh SD, et al. Effects of iontophoresis current magnitude and duration on dexamethasone deposition and localized drug retention.

Two types of (polymer-imaging agent-drug) complexes were prepared and characterized. These included block and graft copolymer complexes with magnetite nanoparticles and manganese ions. Magnetite block ionomer complexes (MBICs) were formed through binding of a portion of the anionic segment of poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA) block copolymers with the magnetite nanoparticle surfaces. The remainder of the carboxylic acids were utilized to bind with high concentrations of the cationic antibiotic gentamicin (31 wt%). A near zero-order release of gentamicin (pH 7.4 in PBS) that reached ~35 wt% of the initial gentamicin within 10 hours was observed, and this was followed by slower release of another 7 % by 18 hours. These nanoparticles were efficiently taken up by macrophages and appeared to enhance intracellular antimicrobial activities of gentamicin. To increase the complex sizes and NMR T2 relaxivities, amine functional MBICs (MBICs-NH2) were first assembled by adsorbing the polyacrylate block of an aminofunctional poly(ethylene oxide)-b-poly(acrylic acid)) (H2N-PEO-b-PAA) copolymer onto magnetite nanoparticles. Amines at the tips of the H2N-PEO corona were then linked through reaction with a PEO diacrylate oligomer to yield MBIClusters where the metal oxides in the precursor nanoparticles were distinctly separated by the hydrophilic polymer. These MBIClusters with hydrophilic intra-cluster space had transverse relaxivities (r2's) that increased from 190 to 604 s-1 mM Fe-1 measured at 1.4 T and 37°C as their average sizes increased. The clusters were loaded with up to ~38 wt% of the multi-cationic drug gentamicin. MRI scans focused on the livers of mice demonstrated that these MBIClusters are very sensitive contrast agents. These results indicate that these complexes could be potential theranostic agents for dual imaging and drug delivery. Manganese graft ionomer complexes (MaGICs) comprised of Mn ions and a novel polyaminobisphosphonate-g-PEO copolymer were developed for use as T1 weighted MRI positive contrast agents. The graft copolymers were prepared by free radical copolymerization of ammonium bisphosphonate methacrylate monomers with PEO-acrylate macromonomers. The complexes exhibited good colloidal stability without release of free manganese and did not show any in vitro toxicity against mouse hepatocytes. The T1 relaxivities of the MaGICs were 2-10 times higher than that of a commercial manganese based contrast agent MnDPDP. These MaGICs with encapsulated anticancer drugs including doxorubicin, cisplatin and carboplatin have encapsulation efficiencies of 80-100 %. Drug release was sustained and depended on environmental pH, drug structure and drug concentration in the MaGICs. Moreover, these drug-loaded complexes exhibited high anticancer efficacy against MCF-7 breast cancer cells. The prominent MRI relaxivities and high anticancer efficacy suggest that these MaGICs have potential as effective dual imaging and chemotherapeutic agents. / Ph. D.

Interest within the healthcare profession in transdermal delivery of pharmaceuticals through passive, mechanical (phonophoresis) or electromotive (iontophoresis) forces has increased significantly throughout the past decade. The current review will examine the histology and cellular biology of the integument system as related to regulation of transcutaneous delivery of pharmaceutics, and examine currently accepted mechanism(s) of iontophoretic delivery. Additionally, a survey of current iontophoretic devices and electrodes available within the U.S. market, and the limitations of current technology will be presented. Experimental research supporting the use of iontophoresis for local delivery of pharmaceuticals will also be presented in conjunction with the outcomes of clinical investigations where iontophoresis was utilized for the local delivery of these pharmaceuticals. Topic areas to be covered within this section include iontophoresis of antibiotics into integument wounds, local anesthetics, and steroidal and nonsteroidal anti-inflammatory drugs. Finally, an examination of the benefits of combining various forces to enhance transcutaneous drug delivery and future direction(s) of research within this field will be discussed. The purpose of the present review is to provide both researchers and clinical practitioners with an objective basis for the current use of iontophoresis in rehabilitation medicine.

Drug delivery via skin is a non-invasive, patient compliant, and effective method for circulatory or skin-targeted therapeutic treatment. Based on its mechanism of action, a topical system employing cromolyn sodium (CS) poses as a cheaper, safer alternative to current treatments for atopic dermatitis, an allergic skin disease. Clinical studies have successfully treated atopic dermatitis with CS emulsions; however, semisolid CS gels have not been investigated and no commercial formula is available to date. Additionally, clinical doses of CS do not passively permeate skin, although different chemical enhancers can be incorporated into formulation to enhance cutaneous drug absorption. This study aimed to investigate salcaprozate sodium (SNAC) as a chemical enhancer for optimized drug delivery to the dermis for potential remedial effects of CS gels. Gels were prepared weight-to-weight by combining 4% CS, 1% hydroxypropyl cellulose as gelling agent, and respective amounts of propylene glycol as base. For SNAC gels, contents included 2.5%, 4.5%, and 9% SNAC, and amount of propylene glycol was adjusted accordingly. CS gel (4%) containing no SNAC was used as a control. After overnight shaking, gels were sonicated for 30 min to use in in vitro permeation studies. Porcine ear skin was mounted on Franz diffusion cells maintained at 37°C, and permeation studies were performed over 24 h for each formulated gel to determine their effect on CS permeation across skin. Donor compartment contained 100 μL gel while the receptor held phosphate buffered saline (PBS). At predetermined timepoints, 300 μL of receptor solution was sampled, replaced with fresh PBS, and analyzed using HPLC with CS detection at 236 nm. Following 24 h, remaining gel was removed, and skin surface was cleaned. Skin layers were manually separated, minced, and left to shake for 4 h to extract permeated drug using methanol. These samples were vacuum dried overnight and reconstituted with PBS to be analyzed using HPLC. Efficiency of skin extraction methods was evaluated by assessing amount of drug recovered from skin compared to amount of drug absorbed where results were plotted, and subsequent equations were used to correct skin data. Student’s T test with Welch’s correction was applied to confirm statistical significance between gels. Passive delivery of the 4% CS control gel to the dermis was 0 μg/cm2. The SNAC containing gels demonstrated significantly improved drug delivery to the dermis when compared to control for 2.5% (36.26 ± 13.05, p=0.05), 4.5% (11.64 ± 1.45, p=0.001), and 9% (35.87 ± 2.23, p=0.004) SNAC groups. No significant differences were observed between any SNAC gel group and the control gel regarding drug delivered to the epidermis or receptor over 24 h. This study observed the greatest delivery of CS to the dermis with the 2.5% SNAC gel, posing as a promising option for a commercially available topical CS gel for the skin-targeted treatment of atopic dermatitis.

Background: Spinal cord injury (SCI) is a devastating condition for which current treatment strategies provide no cure. Delivery of growth factors at the injury site may stimulate endogenous stem cells for nerve regeneration. Biocellulose (BC) was reported to be biocompatible, abundant and have adjustable mechanical properties. However, BC has not been tested for the treatment of SCI. Hypothesis: Composite microsphere loaded BC tubes can have a sustained protein release profile with high encapsulation efficiency and low initial burst rendering it suitable for spinal cord regeneration. Methods: Bovine serum albumin loaded poly (lactic-co-glycolic acid) microspheres were fabricated and characterized while studying the effect of different process parameters on encapsulation efficiency, release profile and morphology. Microspheres were loaded to BC tubes and were characterized morphologically and mechanically. Results: Inner phase volume and the drug:polymer ratio are the main factors impacting microsphere protein encapsulation. Furthermore, presence of different osmotic agent concentrations in the aqueous phase produced a smooth morphology while eliminating the initial burst. Finally, the composite BC tubes were fabricated, and mechanical properties were suitable for SCI applications. Contexte : Les lésions de la moelle épinière sont une maladie dévastatrice que les stratégies de traitement actuelles ne permettent pas de guérir. L'administration de facteurs de croissance sur le site de la lésion peut stimuler les cellules souches endogènes pour la régénération des nerfs. La biocellulose est biocompatible, abondante et possède des propriétés mécaniques ajustables. Cependant, la biocellulose n'a pas été testée pour le traitement des lésions de la moelle épinière. Hypothèse : Les microsphères en composite situées dans les tubes de biocellulose peuvent avoir un profil de libération soutenue de protéines avec une grande efficacité d'encapsulation ainsi qu’un faible taux de libération initial, ce qui les rend appropriés pour la régénération de la moelle épinière. Méthodes : Des microsphères de poly (acide lactique-co-glycolique) chargées d’albumine de sérum bovin ont été fabriquées et caractérisées tout en étudiant l'effet de différents paramètres du processus sur l'efficacité de l'encapsulation, le profil de libération et la morphologie. Les microsphères ont été mises dans des tubes de biocellulose et ont été entièrement caractérisées. Résultats : Le volume de la phase interne et le ratio médicament : polymère sont les principaux facteurs qui influent sur l'encapsulation des protéines en microsphères. De plus, la présence de différentes concentrations de sel dans la phase aqueuse a produit une morphologie lisse tout en éliminant la libération initiale. Enfin, les tubes de biocellulose en composite ont été fabriqués et les propriétés mécaniques étaient adaptées pour l’application sur des lésions de la moelle épinière.

Highly integrated and customizable systems have been a principal focus of development for parenteral and oral drug administration. Extensive work has been done to optimize drug efficacy via localized delivery and dosage control providing new ways for accomplishing targeted therapeutic effects. However, many challenges and opportunities for advancement remain. One promising research path is introducing novel microfabrication methods or engineering discoveries in concept realization, making devices more versatile and effective. Firstly, this dissertation focuses on designing and fabricating a miniaturized, 3D printed, wirelessly powered drug delivery system for biomedical applications. The drug delivery system is composed of an electrolytic micropump integrated into a 3D printed reservoir equipped with hollow microneedles. The electrolytic pump is composed of interdigitated electrodes and a bellows membrane. A simple and customizable manufacturing process is developed to fabricate miniaturized bellows membranes. To improve the integration of microneedles in microelectromechanical devices, a high-resolution 3D printing technique is implemented to produce a reservoir equipped with an array of hollow microneedles. Penetration tests of microneedles into a skin-like material confirm sufficient stability of microneedles. Furthermore, the microneedle arrays are used to pierce and deliver into mouse skin successfully. The assembled system (electrolytic micropump integrated into the 3D printed reservoir equipped with hollow microneedles) is actuated using inductive wireless powering. Secondly, this dissertation tackles one of the most challenging diseases, Coronary Artery Disease. Delivering a therapeutic agent directly to the inner wall of affected blood vessels can be a transformative step toward a better treatment option. To open the door for such an approach, a catheter delivery system is developed based on a conventional balloon catheter where a fluidic channel and microneedles are integrated on top of it. This enables precise and localized delivery of therapeutics directly into vessel walls. Ex vivo tests on rabbit aorta confirm the microneedles-upgraded balloon catheter’s performance on real tissue. This study shows that microneedles-upgraded balloon catheter is capable of localized and targeted drug delivery into artery walls. The fabrication process ensures a highly customizable solution that can be tailored to patient-specific requirements.

京都大学 / 0048 / 新制・課程博士 / 博士(薬科学) / 甲第19973号 / 薬科博第64号 / 新制||薬科||7(附属図書館) / 33069 / 京都大学大学院薬学研究科薬科学専攻 / (主査)教授 橋田 充, 教授 佐治 英郎, 教授 髙倉 喜信 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20574号 / 工博第4354号 / 新制||工||1677(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 今堀 博, 教授 秋吉 一成, 教授 白川 昌宏 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM