Exploring the fundamentals of nanomaterials design for biomolecular sensing and cancer imaging

Pandit, Subhendu

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https://hdl.handle.net/2142/117514 Copy

Description

Title

Exploring the fundamentals of nanomaterials design for biomolecular sensing and cancer imaging

Author(s)

Pandit, Subhendu

Issue Date

2022-08-23

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

Nie, Shuming

Doctoral Committee Chair(s)

Nie, Shuming

Committee Member(s)

• Gruebele, Martin
• Pan, Dipanjan
• Han, Hee-Sun

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Cancer Imaging
• Biomolecular Sensing
• Image Guided Surgery
• Nanomaterials
• Fluorescence
• Carbon Dots
• Semiconductor Polymeric Nanoparticles
• Albumin based probes

Language

eng

Abstract

Over the last few decades despite significant improvements in chemotherapy, radiation therapy, and other traditional drug-based therapies for cancer treatment, surgical resection is still one of the best ways of removing solid cancer tumors. If a cancer tumor can be precisely resected, without leaving any positive cancer margin behind and without unnecessary removal of healthy tissues, it can lead to remission and good quality of life for the patient. Currently, in operating rooms, surgeons primarily rely on their visual and tactile senses to resect a cancer tumor. This often leads to imprecise resection, especially in irregular tumors and non-palpable tumors, leading to multiple follow-up surgeries and often relapse of cancer. Pre-operative imaging modalities like CT/MRI/PET images provide rough guidance for the surgeons to locate cancer tumors but due to deformation of tissues, real-time intra-operative image-guidance guidance is required to perform precision surgeries. Optical fluorescence imaging in the near-infrared window with appropriate contrast agents and imaging devices could be used for real-time image guidance for cancer surgery. Optical fluorescence-based molecular imaging holds the promise to bridge pre-operative imaging with intra-operative reality. Currently, there are only three FDA-approved near-infrared (NIR) fluorescent agents, indocyanine green, methylene blue, and OTL38. Indocyanine green and methylene blue are blood pool agents, which have been repurposed to be used in image-guided surgery because of their FDA approval. OTL38, on the other hand, is a folate-receptor-targeted NIR dye developed specifically for image-guided surgery applications. To push the forefront of optical fluorescence image-guided surgery, new biocompatible NIR-fluorescent contrast agents with desired pharmacokinetic properties need to be developed specifically for image-guided surgery. Here we have explored three nanomaterials, carbon dots, semiconductor polymeric nanoparticles, and albumin-based probes, for their potential application in image-guided surgery. Carbon dots (CDs) are a class of fluorescent nanomaterials that are biocompatible, biodegradable, easy to synthesize, and have bright and stable fluorescence. Most importantly, carbon dots contain no heavy metal, which is a long-term toxicity concern for most inorganic fluorescent nanoparticles. If CDs could be tuned to have NIR emission and can be effectively targeted to be delivered to cancer tumors, CDs could be an excellent contrast agent for image-guided surgery. However, the emission mechanism and electronic structure of CDs are poorly understood. In this thesis, we have explored various surface modifications of CDs to tune their optical properties and understand how those alter their emission behavior. We have shown that crosslinking the surface carboxylic acids of CDs with bisamines leads to a blue shift of fluorescence emission and changes their cellular uptake properties. We have also studied how surface modification of CDs with electron-donating or electron-accepting groups changes their photophysical properties in bulk and at the single-particle level. We also observed a probable near-infrared emitting aggregated state in CDs at very high concentrations and tried to capture the aggregated state with polymeric encapsulation and with lipid nanoparticles but both the approaches did not work. Finally, we have conducted scanning tunneling microscopy (STM) studies on phenylenediamine-derived multi-color CDs to understand the origin of their multi-color emission. We have imaged the ground state electronic band structure of these materials at a sub-single-particle resolution to understand their possible fluorescence mechanism. All these studies provide us with insight into the fluorescence mechanism of CDs to tune them for various biomedical and energy applications. The fluorescence emission of CDs is heavily influenced by the chemical environment around it. The surface defects in CDs are believed to be the main emission center of CDs, and the electronic structure of those groups is influenced by the pH, solvent, and other external factors. CDs change their emission behavior with non-covalent interactions (electrostatic, π-π, H-bonding, hydrophobic interaction, etc.) with the surrounding environment. We used this property of CDs to make multiple array-based sensors for detecting proteins and metal ions. We developed a surface-functionalized CD-array for sensing proteins in the buffer and human serum. We also developed another array-based sensor with the crosslinked CDs to detect proteins. We showed metal ion sensing with the crosslinked CD array and with an associated CD structure array. Next, we have explored a nanoformulation of semiconductor polymeric nanoparticles (SPNs) for their potential use in image-guided surgery. SPNs have emerged as a promising class of nanoparticles that are comprised of optically active semiconducting polymers (SPs). As SPs are organic and biologically inert, SPNs essentially circumvent the issue of heavy metal ion-induced toxicity to living organisms and thereby possess good biocompatibility. We developed a nanoformulation of fluorescent SPNs by coating them with targeting ligand-modified red blood cell membranes (RBCm). With different ligand modifications on RBCm coating (folate and cRGD insertions) we could target different receptors, folate receptors and αVβ3 integrins, on cancer cells. With our biomimetic coating, we could achieve enhanced blood circulation, precise tumor targeting, and reduced macrophage uptake. We also chose two SPNs for our nanoformulations in such a way that both of them can be excited with a single laser excitation but the fluorescence emission signal could be separated. Being able to target two biomarkers together, with multiplexed imaging agents, helps us better image heterogeneous tumors and leads to better resection. The single laser excitation helps further reduce the instrumentation clutter in operating rooms. These nanoformulations provide us with a platform to develop biomimetic nanoparticles, particularly for image-guided surgery applications. Optical fluorescence guidance has been the primary modality for intra-operative imaging, but it suffers from the problem of poor penetration depth. Radio guidance, together with optical fluorescence guidance can address the penetration depth problem of unimodal optical probes. Here we have developed an albumin-based probe for bimodal fluorescence and PET imaging. We have done the synthesis and characterization of the albumin-based probes to understand how albumin can be modified to incorporate two imaging modalities together. We have looked at the cellular uptake of the probes and their in vivo biodistribution to determine the feasibility of clinical translation. The PET images reveal that, unlike the unimodal probes, our bimodal probe gets heavily stuck in the liver like most other nanoparticles and raises the long-term toxicity problem. Our bimodal albumin-based probes could still be useful for IGS because of their ability to target gp60 proteins to actively transcytose into cancer tumors but that needs further careful evaluation for conclusive evidence. In summary, we have studied CDs, biomimetic SPNs, and albumin-based fluorescence-PET probes to determine their potential in clinical translation as an IGS probe. For CDs, we have done mainly fundamental studies to understand their emission properties to be able to eventually tune CDs to have NIR emission for IGS applications. We have shown that we could build array-based sensors with surface-functionalized CDs for biomolecular detection. For biomimetic SPNs, we have done in vitro and in vivo studies to show their enhanced blood circulation, precise tumor targeting, reduced macrophage uptake, and multiplexing ability for targeting multiple biomarkers at the same time for potential application in IGS. We have also developed an albumin-based bi-modal probe for a fluorescence-PET signal for radio guidance along with fluorescence guidance for IGS.

Graduation Semester

2022-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/117514

Copyright and License Information

Copyright 2022 Subhendu Pandit

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