Functionalized organosilica nanoparticles for potential application in drug delivery

Abstract

Nanoparticles as drug delivery vehicles are of particular interest due to their potential to enhance therapeutic specificity and reduce toxicity in cancer treatment. Organosilica nanoparticles (SiNPs) are an excellent nanocarrier platform for biomedical applications, as they are inorganic-organic nanoparticles that allow for targeted drug delivery and, potentially, functionalization. Despite this potential, the relationship between surface modification processes, colloidal behavior, and cytotoxicity remains poorly understood. This thesis describes the synthesis of thiolated SiNPs using 3-(mercaptopropyl)trimethoxysilane as a scaffold for targeted peptide delivery to bladder cancer using dynamic light scattering, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, NMR spectroscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A library of five maleimide-functionalized conjugates was prepared, containing two cell-penetrating peptides, TAT and R11, and three target peptides, Bld1KLA, NT4, and CLT1. The molecular weight of the peptide and the conjugation coefficient of the peptide were found to be the main factors influencing the grafting density and colloidal behavior, with higher concentration and molecular weight of the peptide leading to aggregation due to steric and electrostatic interactions. The biosafety of the cell penetrating peptide conjugates was then evaluated in RT112 bladder cancer cells by an MTT assay and it was found that R11 conjugates with high peptide density cross the threshold for cytotoxicity at elevated concentrations, but low-density versions remained non-cytotoxic. The compatibility of the target peptide conjugates was measured with the MTT and Alamar Blue assay, and all three compounds were identified as non-cytotoxic in the examined concentration range. Ex vivo studies in Drosophila melanogaster larval cells showed that SiNP-CLT1 and SiNP-NT4 did not negatively affect cell growth; however, SiNP-Bld1KLA caused a decrease in cell division as a thiolated SiNP, consistent with the pro-apoptotic function of the KLA domain. However, the lack of integrin expression that is relevant to cancer in Drosophila means that the model does not have the capability to evaluate peptide-selective targeting, and disease-relevant model will be necessary. These results reveal the importance of surface functionalization strategy in determining the physicochemical and biological performance of peptide functionalized organosilica nanoparticles and identify the potential for delivery of drug agents for bladder cancer.