Towards Designer Microparticles: Simultaneous Control of Anisotropy, Shape, and Size

Biodegradable, compositionally anisotropic microparticles with two distinct compartments that exhibit controlled shapes and sizes are fabricated. These multifunctional particles are prepared by electrohydrodynamic co-jetting of poly(lactide-co-glycolide) polymer solutions. By varying different solution and process parameters, namely, concentration and flow rate, a variety of non-equilibrium bicompartmental shapes, such as discoid and rod-shaped microparticles are produced in high yields. Optimization of jetting parameters, combined with filtration, results in near-perfect, bicompartmental spherical particles in the size range of 3–5 µm. Simultaneous control over anisotropy, size, shape, and surface structure provides an opportunity to create truly multifunctional microparticles for a variety of biological applications, such as drug delivery, diagnostic assays, and theranostics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65050/1/404_ftp.pd

Cooperative Switching in Large‐Area Assemblies of Magnetic Janus Particles

Magnetic Janus particles (MJPs) have received considerable attention for their rich assembly behavior and their potential technological role in applications ranging from simple magnetophoretic displays to smart cloaking devices. However, further progress is hampered by the lack of predictive understanding of the cooperative self‐assembly behavior of MJPs and appropriate dynamic control mechanisms. In this paper, a detailed experimental and theoretical investigation into the magnetically directed spatiotemporal self‐assembly and switching of MJPs is presented. For this purpose, a novel type of MJPs with defined hemispherical compartments carrying superparamagnetic iron oxide nanoparticles as well as a novel simulation model to describe their cooperative switching behavior is established. Combination of the theoretical and experimental work culminates in a simple method to direct assemblies of MJPs, even at high particle concentrations. In addition, a magnetophoretic display with switchable MJPs is developed on the basis of the theoretical findings to demonstrate the potential usefulness of controlled large‐area assemblies of magnetic Janus particles.Anisotropic particles that have one hemisphere selectively loaded with magnetite nanoparticles rotate in response to magnetic fields as indicated by visually observable color changes.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155896/1/adfm201907865-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155896/2/adfm201907865.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155896/3/adfm201907865_am.pd

Multicompartmental Biomaterials via Electrohydrodynamic Co-jetting.

The synthesis and theranostic applications of biodegradable anisotropic materials are described in this dissertation. Precise nano- and micro-scale control of the architecture of biodegradable polymeric materials is highly desirable for improved versatility and performance of biomedical devices such as drug release systems, biomedical coatings and multiplexed bioassays. Along with traditional attributes such as size, shape and chemical structure of polymeric micro-objects, control over material distribution, or selective compartmentalization has been shown to be increasingly important for maximizing functionality and efficacy. The simplest example of a compartmentalized micro-structure is a ‘Janus’ sphere, comprising of two distinct hemispheres made of different materials. Such novel particle geometries enable independent control of key parameters, such as chemical composition, surface functionalization, biological loading, shape, and size for each compartment, thereby effectively mimicking many of nature’s complex architectures. In this dissertation, the fabrication of multicompartmental architectures made from biodegradable polymers, specifically poly(lactide-co-glycolide) (PLGA) is demonstrated. To accomplish this, we employed ‘electrohydrodynamic co-jetting’, whereby the interface between two or more polymer solutions is sustained as they are flown through a side-by-side capillary system. Application of an electric field results in the formation of an electrospray, and solvent evaporation results in particle (or fiber) formation. By controlling over solution and process parameters, a vast repertoire of shapes and sizes of anisotropic objects such as spheres, fibers, discs, rods, and cylinders was formulated. Compositional anisotropy is also introduced in particles and fibers by means of incorporation of functional materials such as magnetite nanoparticles, and stimuli responsive hydrogels, these are shown to act as displays and agents for delivery of therapeutic payloads. Spatioselective control over surface chemistry is demonstrated via introduction of free acetylene groups in selected volumes, and their surface modification via “click chemistry”. We then utilize the surface anisotropy of these microstructures to self assemble them into larger architectures in case of particles, and to form unique cell-guiding scaffolds in case of fibers. Enabling the design of particles with multiple and distinct surface patterns or nano-compartments would help spur the development of the next generation of high throughput biomedical devices.Ph.D.Macromolecular Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/84428/1/sbhaskar_1.pd

Micropatterned Fiber Scaffolds for Spatially Controlled Cell Adhesion

Because the local microstructure plays a pivotal role for many biological functions, a wide range of methods have been developed to design precisely engineered substrates for both fundamental biological studies and biotechnological applications. However, these techniques have been by-and-large limited to flat surfaces. Herein, we use electrohydrodynamic co-spinning to prepare biodegradable three-dimensional fiber scaffolds with precisely engineered, micrometre-scale patterns, wherein each fiber is comprised of two distinguishable compartments. When bicompartmental fiber scaffolds are modified via spatially controlled peptide immobilization, highly selective cell guidance at spatial resolutions (<10 µm), so far exclusively reserved for flat substrates, is achieved. Microstructured fiber scaffolds may have utility for a range of biotechnological applications including tissue engineering or cell-based assays.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64103/1/1638_ftp.pd

Macromol. Rapid Commun. 19/2009

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64100/1/1597_ftp.pd

Inside Cover: Multicompartmental Microcylinders (Angew. Chem. Int. Ed. 25/2009)

Multicompartmental microcylinders can be produced by a combination of electrohydrodynamic co-spinning and microsectioning, as described by J. Lahann et 14al. in their Communication on page 144589 14ff. The number of individual compartments, relative compartment orientation, chemical composition and functionality, and aspect ratio can be precisely tuned. Each color in the longitudinal and cross-sectional micrograph images depicts an individual compartment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63047/1/4452_ftp.pd

Innentitelbild: Multicompartmental Microcylinders (Angew. Chem. 25/2009)

Mikrozylinder mit mehreren Kompartimenten lassen sich mit einer Kombination aus elektrohydrodynamischem Spinnen und Mikroabtrennen herstellen, wie J. Lahann et 14al. in der Zuschrift auf S. 144659 14ff. beschreiben. Die Zahl der einzelnen Kompartimente, ihre relative Orientierung, chemische Zusammensetzung und FunktionalitÄt sowie das SeitenverhÄltnis kÖnnen maßgeschneidert eingestellt werden. Jede Farbe in den LÄngs- und Querschnitt-Mikrographen entspricht einem individuellen Kompartiment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63035/1/4520_ftp.pd

Microparticles: Small 3/2010

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65038/1/329_ftp.pd

Macromol. Rapid Commun. 5/2011

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83198/1/22220_ftp.pd

Biocompatible Polymers: Structurally Controlled Bio-hybrid Materials Based on Unidirectional Association of Anisotropic Microparticles with Human Endothelial Cells (Adv. Mater. 48/2009)

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/64541/1/4873_ftp.pd