Characterization of the nano- and meso-scale hierarchic assembly in biomimetic membranes and living systems

Kambar, Nurila

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https://hdl.handle.net/2142/127386 Copy

Description

Title

Characterization of the nano- and meso-scale hierarchic assembly in biomimetic membranes and living systems

Author(s)

Kambar, Nurila

Issue Date

2024-12-04

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

Leal, Cecilia

Doctoral Committee Chair(s)

Leal, Cecilia

Committee Member(s)

• van der Zande, Arend
• Statt, Antonia
• Chen, Qian
• Pogorelov, Taras V.

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• lipids
• block copolymers
• hybrid membranes
• biomimetic
• characterization
• hierarchic assembly
• phase separation
• cryo-EM
• micropipette aspiration

Abstract

This dissertation investigates the hierarchical assembly of biomimetic membranes and living systems at the nano- and mesoscale, which is essential for understanding both synthetic hybrid systems and natural membranes. The focus is on the structural characterization of hybrid membranes composed of amphiphilic block copolymers and lipids, which mimic architecture and assembly of proteins and lipids in natural biological membranes. These hybrid systems exhibit distinct self-assembly patterns that span across multiple length scales, revealing insights into how molecular interactions give rise to specific structural and functional properties. Building on studies of composition–structure–property–function relationships in biomimetic membranes, I leverage this knowledge to advance the characterization of living bio-membrane systems. Advanced characterization techniques, including X-ray diffraction, cryo-electron microscopy (cryo-EM), confocal microscopy, polarized optical microscopy, and light scattering, were employed to study the self-assembly and evolution of these membranes from the nanoscale to the mesoscale. Particular emphasis is placed on understanding intermediate nanoscale structures, which serve as a bridge between molecular interactions and overall membrane functionality. In the initial stages of this work, the mechanical and structural properties of hybrid membranes were investigated by comparing the crystalline and amorphous behaviors of block copolymers (PCL and PBD blocks, respectively) and their interactions with phospholipids such as DOPC and DPPC, the most abundant lipids in plasma membranes. Inspired by the functional role of membrane proteins (MPs) in biological membranes, which facilitate and enhance elastic deformations while maintaining structural integrity, this study aimed to mimic these behaviors in hybrid systems. To gain insights into how these materials influence membrane elasticity, phase separation, and mechanical stability, techniques such as micropipette aspiration, atomic force microscopy (AFM), and molecular simulations were employed. Specifically, I focused on establishing the micropipette aspiration technique in the lab, as it closely replicates the elastic deformation mechanism by which biological membranes recruit MPs to support functional elastic deformations. The study revealed that polymer crystallinity significantly influences the mechanical behavior of hybrid membranes, with amorphous polymers promoting better integration and flexibility, while crystalline polymers contributing to more rigid structures. The research then delved into nanoscale phenomena, focusing on the persistence of phase separation in hybrid systems at the nanoscale. Biomembranes are known to stabilize small functional domains that can interact and correlate with one another. A key question addressed was: What is the smallest polymer-rich domain morphology, and do these domains exhibit interlayer correlations in stacked configurations, similar to microdomains? High-resolution cryo-EM and molecular dynamics simulations revealed unique phase-separated morphologies in polymer-lipid hybrid membranes, including the discovery of an ”unzipped” structure. In this configuration, hydrophobic polymer nanodomains integrate within bilayer leaflets. This unzipping phenomenon provides critical insights into how hybrid membranes accommodate hydrophobic mismatches, offering a novel perspective on biomembrane morphology and the influence of bulky hydrophobic residues on membrane-protein interactions. Further, a novel deep-learning approach was developed to analyze hybrid polymer–lipid multilamellar vesicles at the nanoscale. By combining cryo-EM with machine learning, this method provides unprecedented accuracy in mapping bilayer thickness and visualizing nanoscale domains, overcoming limitations of traditional image analysis techniques. This advancement enhances the ability to study complex multilamellar systems and their nanoscale architecture. The final part of the chapter applies these structural insights to the development of hybrid multilamellar nanoparticles via microfluidics, designed as carriers for low-solubility drugs. By leveraging the chemical diversity of polymers and the biocompatibility of lipids, these hybrid nanoparticles represent a promising advancement in drug delivery systems. This dissertation concludes by applying the developed characterization techniques to living systems, offering nanoscale insights into processes like host-microbe interactions and cellular organization, thereby bridging the gap between synthetic and biological membrane systems.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127386

Copyright and License Information

Copyright 2024 Nurila Kambar

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