비뇨기계 치료용 이동 제어형 마이크로/나노 모터의 미세유체 기반 제조

Abstract

A drug delivery system (DDS) is a technology that improves the drug bio-lifetime and effectively delivers pharmaceutical compounds to a specific target in the body by encapsulating a drug in the carrier such as synthetic particles, lipids, micelles, and nanoparticles. The DDS has led to minimizing the side effects of native drugs and maximizing the therapeutic effect, resulting in significant progress in the medical field for many years. Despite many advances in drug delivery systems, these limitations are still a major challenge for the used clinical stage of DDS due to low penetration and accumulation effects by biological barriers such as the phagocytic system and blood capillary wall resistance, To overcome these limitations, micro/nano-motors have been developed as a DDS to improve treatment effects with self-propelled mobility. These micro/nano-motors in the blood circulation improve tissue permeability and promote cell absorption through the enhanced accumulation of therapeutic drugs by strong movement. In addition, using the targeting ligand decorated micro/nano-motor has an excellent synergistic effect of disease targeting ability. In general, micro/nano-motors require an asymmetric structure such as a Janus structure for an asymmetric gradient force to induce active motion in a fluid environment. To fabricate Janus structures of micro/nano-motors, thin film deposition, template sacrifice, and assembly methods such as layer-by-layer (LBL), self-assembly have been developed. Membrane deposition and template sacrifice methods include the multi-steps such as evaporation of the target material, transport of vapor to the substrate surface in a vacuum or partial vacuum environment, cooling and thin film formation, and removal from the template, resulting in high cost, reproducibility, non-uniform size, low yield, and multi-step processes. In addition, the methods focused on the fabrication of chemically propelled motors rather than the production of bio-catalytic micro/nano-motors. Then, the methods of fabricating micro/nano-motors using a Pickering emulsion and the self-assembly method were proposed to overcome high cost, multi-step process, elaborate operation, and low productivity. The traditional PVD method produces micro/nano-motors on a 2D plane. However, the Pickering emulsion and self-assembly method using a 3D environment is one of the potential scalable methods. In addition, these methods can produce various bio-catalytic the propellants based the micro/nano-motors. However, Pickering emulsion and self-assembly processes produced in flasks directly affect the Janus structure by the mixing speed/time of the agitator and also affect the reproducibility of the propellant of the motor due to the non-uniform shear force in the flask. Recently, microfluidic technology has been proposed as an alternative to traditional flask synthesis of micro/nano-carriers. A microfluidic device with a microscale has minimized dead volume by mixing in a small channel, and it is possible to form different flows with reproducibility by enabling rapid mixing and flexible control of the flow regime. The microfluidic platform typically has three types of flow through the control of the fluid: laminar flow, turbulent flow, and segmental flow, and offers new features related to space-time control. Laminar flow can control the concentration of reactants by molecular diffusion without mixing, while turbulent flow can induce rapid mixing within milliseconds. Furthermore, it is possible to reproducibly generate droplets or clumps of uniform size using immiscible heterogeneous solutions and segmental flow. The synthesis of micro/nano-motors in a microfluidic system demonstrates the possibility of quantitative/qualitative fabrication of nano/micro-motors through the reproducible and continuous fabrication of different motor types using different types of fluid flows. Meanwhile, the urinary system, including the kidney, urethra, bladder, and urethra, excrete various waste products to maintain homeostasis. Various urological diseases such as bladder cancer, hydronephrosis, urolithiasis, and renal failure can occur in this system. Representative urological diseases include bladder cancer and urolithiasis. Chronic irritation and inflammation associated with urolithiasis cause changes in the local environment and consequently lead to malignant neoplasms such as urinary tract epithelial hyperplasia and bladder cancer, both of which need to be addressed. Procedures to address these problems generally require surgical approaches such as endoscopic, percutaneous, and open access, and incisional surgery or retrograde ureteral catheterization is performed to reduce recurrence and progression. However, non-selective/invasive injection methods cause side effects such as severe pain, mucosal bleeding, and sepsis, and a differentiated and non-invasive method is needed for clinical application. Due to the relatively high concentration of urea in the urinary system and the large space filled with the solution, urea-used micro-nano motors have recently become a promising approach to treating urinary tract diseases. Micro/nano-motors synthesized with urease can induce asymmetric self-propelled mobility due to urea and urea and induce effortless mobility due to a wide space without obstacles, which can induce other organs such as the liver, intestines, and eyes to pay more attention. Although the currently developed micro/nano-motors show higher efficacy than traditional drug delivery systems, motors have a limitation of low reproducibility of therapeutic effect due to the low homogeneous size /reproducibility of the motors. In this Ph.D. thesis, the various types of motion-controlled micro/nano-motors synthesized in microfluidics for urological disease medication are introduced. The high-quality micro/nano-motors were reproducibly manufactured using the single Pickering emulsion, laminar flow, and double emulsion by controlling the different fluid-type microfluidic devices. The traditional manufacturing approaches of micro/nano-motors have the limitation of reproducibility, inhomogeneous size, and low productivity. However, microfluidics has the advantages of continuous flow, reproducible flow control, and homogeneous mixing, resulting in a homogeneous carrier size, reproducible carrier structure, and scalable production of micro/nano-motor. In addition, microfluidic manufactured high-quality micro/nano-motor have a potential therapeutic effect on urological diseases such as bladder cancer and Urolithiasis. In Chapter 1, for the explanation of the necessity of our approach, a general introduction of micro/nano-motor as a drug delivery system (DDS) for urological diseases was summarized such as the limitation of traditional urological disease treatment, advantages of micro/nano-motor prepared in microfluidics, and micro/nano-motor for urological disease treatment. In Chapter 2, to prove potentially scalable nano-motor, an integrated flow synthesis of triple-responsive (thermophoretic, chemical and magnetic movement) nano-motors by a droplet microfluidic based Pickering emulsification approach, and subsequent two steps for anisotropic surface modification of the bound nanoparticles in a scalable manner are presented. In general, Janus structure is required for mobility of micro/nano-motor. Conventionally, for the manufacturing method of Janus motor, the electric vapor deposition method which is mainly applied particles to membrane as a single layer and deposited a metal. However, the traditional method have limitation such as discontinuous/multi-step process, difficulty of single layer dispersion of particles, and the only production of metal-based motor. To overcome these problems, the microfluidics Pickering emulsion method was used. The droplet microfluidics platform contributed to in-situ generate the monodisperse size (600 µm) of photoresin droplet with equal curvature that allowed uniform Pickering emulsification by fast adsorption of colloidal m-SiO2/Fe3O4 particles (400 nm) with controlled amphiphilicity onto the droplet interface within a close proximity. Under the optimal conditions, superior Pickering efficiency with high reproducibility to the batch process led to produce Janus nanoparticles (m-SiO2/Fe3O4-Pdop/Pt) with 0.7 g hr−1 of high throughput functioned as triple-responsive nano-motors via site-selective Pdop and Pt decoration in a serial flow. Eventually, catalytic and thermophoretic swimming motions of the nano-motor exhibited 14.2 µm s−1 at H2O2 10 wt% solution, 3.8 µm s−1 at NIR light, 16.4 µm s−1 at H2O2 10 wt% with NIR-on condition, which are relatively better or compatible to the reported speeds, while it showed a magnetically actuated motion with velocity of 4.5 µm s−1. Note that a polydopamine based nano-motor is unique with the first non-metallic thermophoretic motion. In the Chapter 3, the protection of bio-catalyst (urease) and substrate (polydopamine: Pdop) by core@shell technique for prevention of the decreasing the therapeutic efficacy and movement is described. The enzyme-propelled nano-motor (Pdop@urease@aZIF-8) was synthesized for enhanced bio-catalytic motion and protection of substrates (Pdop as a core) and enzymes (urease and proteinase K) by an amorphous ZIF-8 shell. A capillary flow reactor connected with three- and two-way 3D-printed channels generated a stable triple laminar flow that enabled the controlled diffusion mixing of Zn2+ and 2-MIM precursors. A specific growth of amorphous aZIF-8 on the surface of Pdop NPs was examined (200 nm). The Pdop@urease@aZIF-8 (A-motor) exhibited satisfactory bio-compatibility and excellent enhanced movements in a urea-presenting basic aqueous (pH at 9.5) environment. When strong NIR was additionally applied, excellent photothermal (>60 °C) behavior along with successful urease enzyme protection (>90%) occurred and were maintained for 5 days. In addition, the nano-motor successfully crossed the endothelial tissue layer (>80%) with satisfactory adsorption into the bladder cancer tissue. With NIR exposure (808 nm, 2 W cm−2), successful elimination of cancer cells was observed within 10 min, and was supported by the temperature increase of the adsorbed A-motor. In the Chapter 4, the a novel urolithiasis treatment by delivering the chelating solution encapsulated PLGA-based microcapsules to urolithiasis, followed by US-responsive dissolution of the stones approach is proposed. The double-droplet microfluidics method and post-evaporation allowed the production of microcapsule of homogenous size (319±14 μm) through the encapsulation of HMP chelating solution and Fe3O4 NPs within a PLGA polymer shell (thickness <15 μm). The obtained microcapsules exhibited high magnetic collection efficiency (>99%) and US-responsive release in two different solutions: PBS (< 2 min) and gelatin (< 14 min). Moreover, in a customized Ψ-shaped flow chip, the selective HMP delivery of microcapsules with high magnetic delivery efficiency (> 90%) resulted in effective removal efficacy (>95 %, 7 repeated cycles) of artificial calcium oxalate (5 mm) via a chelating effect. Eventually, the potential urolithiasis treatment of microcapsule approach in humans was tested in a PDMS-based kidney-imitated chip where a human kidney stone (CaOx 100%, size range: 5–7 mm) was located in the minor calyx under artificial urine flow. A group of 500 microcapsules (HMP conc. 100 mM) was magnetically transported to the stone and successfully removed more than 50% of the stone after 10 repeated treatment cycles over a treatment time of 1 hour. Therefore, the selective delivery of chelator-encapsulated microcapsules to the urinary system via magnetic field and/or catheter-guidance offer a perspective for urolithiasis treatment compared with conventional approaches such as surgery and systemic dissolution. This doctoral dissertation has academic/industrial significance by suggesting potential solutions for urological disease treatment by various type of micro/nano-motor with improved productivity and long-term use, which are the limitations of clinical application of current medical motors, using various fluid flows in microfluidics. In addition, by showing the potential treatment of bladder cancer and kidney stones using various therapeutic micro/nano-motor, it is expected to be the alternative approaches to the existing surgical and systemic drug treatment of urological diseases and to become the basis for a new approach using therapeutic nano/micro-motors.