Date of Award

January 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Julia X. Zhao

Abstract

Quantum dots (QDs) are a subset of nanoparticles (NPs) that have several unique optical and electrical properties that make them viable for fluorescent cell labeling applications. However, these QDs in the past were composed of toxic heavy metals such as lead and cadmium, and therefore, graphene-based QDs (GQDs) have been examined as an alternative material for these cell labeling applications for their increased biocompatibility. Furthermore, GQDs can produced singlet oxygen (1O2) for photodynamic therapy (PDT), making them capable of being used as a PS agent for cancer treatment. Additionally, hollow mesoporous silica nanoparticles (hMSNs) are capable of being an alternative treatment to cancer as hMSNs have displayed exceptional drug loading and delivery abilities. The work described in this dissertation will have four primary goals that are all essential for fluorescent cell imaging and cancer treatment using QDs and NPs. The first goal is to investigate current analytical methods for NPs toxicity determination and detection, as well as new protocols for toxicity evaluation. The second goal is to synthesize GQDs using biomass-derived material and hMSNs by a modified Stöber method to improve their biocompatibility and biodegradation. The third is to characterize the newly synthesized GQDs and hMSNs using various analytical methods to better determine their chemical and physical properties. The final goal is to apply the GQDs for fluorescent cell imaging and PDT treatment applications, and the hMSNs for drug loading and delivery into cancer cells. The first project focuses on the investigation of current and advancing analytical methods for nanotoxicity determination and nanoparticle detection. The advancing field of nanoscience has produced lower mass, smaller size, and expanded chemical composition nanoparticles over recent years. These new nanoparticles have challenged traditional analytical methods in terms of qualitative and quantitative analysis. Such advancements of nanoparticles and nanomaterials have captured the attention of toxicologists with concerns regarding the environment and human health impacts. The second project focuses on graphene quantum dots (GQDs), a subset of fluorescent nanomaterials, that have piqued recent interest due to their photoluminescence properties, low toxicity and biocompatibility features for bioanalysis and bioimaging. However, it is still a challenge to prepare highly near-infrared (NIR) fluorescent GQDs using a facile pathway. In this project, NIR GQDs were synthesized from the biomass-derived organic molecule, cis-cyclobutane-1,2-dicarboxylic acid and their applicability for cell-labeling was tested using RAW 264.7 and MCF-7 cells. The third project focuses on red and near infrared emission GQDs, which is a highly desirable feature for fluorescent nanoparticles in biological applications. This is mainly due to longer wavelengths which may penetrate tissues, organs, skin, and other organic components while less autofluorescence interference is produced. Additionally, GQDs that contain unique optical and electrical features have been targeted for their use in cell labeling applications as well as environmental analysis. However, GQDs are frequently reported to have blue-green emission light and not the more advantageous red/NIR emission light. Furthermore, porphyrins are a subgroup of heterocyclic macrocycle organic compounds and have been used previously to synthesize nanomaterials and for nanoparticle doping in order to incorporate the red/NIR emission light property into particles that otherwise do not contain the desired emission light. Meso-tetra(4-carboxyphenyl)porphine (TCPP) is one type of porphyrin with a large conjugated π-electron system and four carboxyl groups on its exterior benzene rings. These two key characteristics of TCPP makes it ideal for incorporation into GQDs as it would design and synthesize red-emissive material as well as give rise to excellent water solubility. In this work, TCPP is used in tangent with cis-cyclobutane-1,2-dicarboxylic acid (CBDA-2), a biomass derived organic molecule, to synthesize “green” porphyrin-based graphene quantum dots (PGQDs) with red-emission. Their imaging application was tested using HeLa cells via confocal microscopy. In the fourth project, the GQDs used previously were combined with silica-based nanoparticles for fluorescent imaging and dual cancer treatment applications. Nano-based cancer therapeutics have been researched and developed, with some nanomaterials being shown to possess anticancer properties. GQDs are one such class of nanoparticles due to their valuable characteristics such as photoluminescence, biocompatibility, and water solubility. When it comes to cancer treatment, GQDs contain the ability to generate 1O2, a reactive oxidative species (ROS), allowing for the synergistic imaging and photodynamic therapy (PDT) of cancer. However, due to their small particle size, GQDs struggle to remain in the target area for long periods of time in addition to being poor drug carriers. To combat this, hollow mesoporous silica nanoparticles (hMSNs) have been extensively researched for drug delivery applications. hMSNs also contain exceptional biocompatibility in addition to high drug-loading capacities and easy surface functionalization. This project investigates the utilization and combination of GQDs and hMSNs to make GQDs-hMSNs for an enhanced double treatment of cancer; using GQDs for 1O2 generation and fluorescent imaging in vitro that would have biodegradable hMSNs synthesized around them to serve as the drug deliverer into the target cancer cell. RAW 264.7 cells were utilized again for the GQDs-hMSNs biological and medical applicational use.

Download

Share

COinS