Fabrication and characterization of a magnetic bacterial nanocellulose for neurovascular reconstruction of cerebral aneurysms

Arias Suarez, Sandra Liliana

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Description

Title

Fabrication and characterization of a magnetic bacterial nanocellulose for neurovascular reconstruction of cerebral aneurysms

Author(s)

Arias Suarez, Sandra Liliana

Issue Date

2016-04-27

Director of Research (if dissertation) or Advisor (if thesis)

Allain, Jean Paul

Department of Study

Bioengineering

Discipline

Bioengineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• bacterial nanocellulose
• magnetic hydrogel
• cerebral aneurysms

Abstract

A cerebral aneurysm is a condition where a defect protrudes out the arterial wall, and which is formed due among other reasons to abnormal high hemodynamic stresses that contribute to deterioration and dilation of the blood vessel. A desirable treatment of cerebral aneurysms is the complete cut-off of the defect from the parent artery with minimum luminal obstruction. Even though different approaches have shown to exclude the defect from the parent artery, the main shortcoming remains the delayed reconstructive occlusion of the aneurysm, which occurs a period of weeks to months. We hypothesized that a material with magnetic properties can provide the force required to speed up re-endothelization across the aneurysm defect, since it can facilitate high cell density coverage at the damaged site in virtue of its ability to capture and retain magnetically functionalized endothelial cells. The aneurysmal neck is a hostile environment for tissue growth resulting from the blood’s shear stress that precludes cell adhesion and proliferation. Therefore, this strategy looks for designing a magnetic material for rapid endothelial cell take up and retention against hemodynamic forces. This magnetic material is required also to satisfy other important features such as biocompatibility, appropriate mechanical properties (e.g. tensile strength and compliance), and blood compatibility (non-thrombogenic). In the present work, we have used bacterial nanocellulose (BNC) as starting material for the production of a magnetic hydrogel, which we named magnetic bacterial nanocellulose (MBNC). BNC is a natural polymer produced by the bacterial strain Acetobacter xylinum, which is extruded as a pellicle in the interface liquid/air to protect the bacteria from dehydration and UV radiation. BNC possesses a multiple of desirable physical and chemical properties for tissue engineering applications such as biocompatibility, high swell ratio, and high tensile strength. D-glucose chains abundant in hydroxyl groups conform the BNC's chemical structure, which are able to adsorb metallic ions and compounds with functional groups active on hydrogen-bonding formation. A brief review about the BNC and magnetic hydrogels are presented in chapter I. In chapter II, we describe the production of BNC and its purification to subsequently synthesize the MBNC through an in-situ precipitation method, in which superparamagnetic iron oxide nanoparticles (SPION) are formed inside the BNC by using ammonium hydroxide as precipitating agent. Different concentrations of Fe3+ and Fe2+iron salts were used for the synthesis of MBNC, and their effect on BNC permeability, porosity and magnetic saturation were analyzed. The permeability testing was performed using a side-by-side diffusion cell. MBNC porosity was estimated using a mass equation balance. Magnetization testing was performed using vibrating sample magnetometer. Scanning electron microscopy (SEM) and magnetic force microscopy (MFM) were used to reveal the morphology and magnetic domains on MBNC respectively. Chemical characterization of the MBNC was performed via X-ray photoelectron spectroscopy (XPS). Because naked SPION are easily oxidized to Fe2O3 under environmental conditions, dextran was used to coat the SPION embedded into the MBNC. In chapter III, once established the optimal reaction conditions for the MBNC synthesis, MBNC pellicles were tested for biocompatibility and cell capture under dynamic fluid flow conditions. Cell adhesion sites were introduced on the surface of MBNC via collagen-conjugation using CDAP as activating agent. Our results showed a satisfactory MBNC magnetization, which was able to separate magnetically functionalized cells under dynamic flow conditions compare to non-magnetized MBNC.

Graduation Semester

2016-05

Type of Resource

text

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Copyright 2016 Sandra Arias Suarez

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