Quantum dots (QDs) CdS and CdSe were synthesized in three different media including reverse micelles, aqueous solution, and trioctylphosphine oxide/trioctylphosphine (TOPO/TOP). Transmission electron microscope (TEM), X-ray diffraction (XRD), UV-VIS, fluorescence spectroscopy and microscopy were used to characterize the QDs and their nanoassemblies. CdS QDs synthesized in reverse micelles showed broad emission spectra. CdSe-CdS QDs with core shell structure synthesized in aqueous solution showed more than 30% emission quantum yield. CdSe-CdS QDs of different emission colors were prepared. CdSe and CdSe-ZnS QDs were also synthesized in TOPO/TOP media. This synthesis route produced highly luminescent CdSe QDs with over 50% emission quantum yield. The application of QDs as ions probes and methods to encapsulate QDs in nanospheres including micelles, glyconanospheres and silica nanospheres and the use of these nanospheres in bioassays are described. CdS QDs capped with different ligands such as thioglycerol, cysteine and polyphosphate showed different responses to biological relevant ions. The emission intensity of polyphosphate capped CdS QDs was affected by all the tested ions and did not show a selective response. On the other hand, the emission of thioglycerol capped CdS QDs was selectively quenched by copper ions while the emission of cysteine capped CdS QDs was selectively enhanced by zinc ions. Stern-Volmer equation was applied to correlate the emission intensity of the CdS QDs and the copper ion concentration. A Lagmuir isotherm binding equation was used to describe the relation between the emission intensity of cysteine capped CdS QDs and zinc ion concentration. The possible mechanism to explain the effects of capping ligands on CdS QDs responses to ions is also discussed. CdSe QDs synthesized in TOPO/TOP media were encapsulated in nanospheres for bioassay applications. The glyconanospheres contained a large number of glucose residues on their surface and showed high binding activity towards the lectinic protein Concanavalin A (Con A). Silica nanospheres containing hundreds of CdSe QDs were functionalized with thiol groups to enable the conjugation of streptavidin to the nanospheres. The streptavidin modified silica nanospheres were used as luminescent indicators in a sandwich immunoassay for the detection of antiprotein A antibody. The advantages and disadvantages of the nanospheres based bioassay are discussed.

In recent decades, a variety of nanoparticle drug delivery systems (NP DDS) – nanometer-scaled materials physically or covalently interacting with therapeutics – has been developed to overcome biological barriers, improve the half-life, reduce toxicity, and improve the efficacy of conventional drug delivery. However, many NP DDS fail to translate to the clinic. While this is in part due to immense heterogeneity within many disease types across individuals, the conflicting size and surface chemistries required in the “drug delivery pathway” (i.e. to avoid the clearance mechanisms and unintended tissues in the body, then to reach and specifically enter target tissues) also pose a significant challenge. Recent advances in the field of drug delivery have created size- and surface-switching nanoparticles that overcome biological barriers. For example, large (100 – 200 nm) NPs are adequate at evading corporeal defense mechanisms, while small (< 50 nm) NPs can actively enter cancerous tissue. Further, release profiles of drug-loaded NP DDS must be tailored to stay within a narrow therapeutic window to prevent toxic effects. This thesis highlights the synthesis of “nanoassemblies”, an NP DDS that contains small, drug-loaded starch nanoparticles (SNPs) within a larger nanogel matrix. Nanoassemblies are chemically tuned to reach specific targets via different administration routes (notably, cancerous tissues via systemic administration and brain tissue via intranasal administration). Furthermore, therapeutic-loaded SNPs are released under endogenous (pH, redox) or exogenous (ultrasound) stimuli for disease-specific release kinetics, allowing for deeper penetration into tumor cores or through the nose-to-brain pathway as required. Both the physicochemical characterization of these nanoassemblies as well as in vitro and in vivo experiments have been performed to assess the efficacy of nanoassemblies in biological systems and how they may provide performance improvements over non-assembled SNPs. As such, nanoassemblies show great promise in overcoming complex biological barriers to ultimately improve drug delivery in clinical applications. / Thesis / Doctor of Philosophy (PhD) / Using drugs to treat diseases is not always effective: the drug often does not work or comes with many side effects. A combination of factors prevents promising drugs from working. Most often the drug is either (partially or fully) removed from the body before it reaches the disease, or it improperly enters healthy tissue to cause undesirable responses. Previous research has shown that if drugs are put into nanoparticles, the nanoparticles can better deliver the drug to the correct target. However, conflicting sizes are needed to travel through different parts of the body, making nanoparticle-based drug delivery only of limited effectiveness in humans. This thesis aims to address these issues by creating “nanoassemblies” – nanoparticles with smaller, drug-containing nanoparticles inside of them – that overcome the typical issues with drug delivery. Nanoassemblies are able to switch their size to better reach the target tissue, ultimately leading to more effective and safe treatments.

<p>This thesis has exploited the use of gold nanoparticles (AuNPs)/DNA conjugates towards 1) the development of simple colorimetric assays to monitor DNA functions and relevant biological processes, and 2) the control the nanoassembly of AuNPs using biomolecules and biological processes.</p> <p>DNA has a number of attractive functions including specific biorecognition, catalysis and being manipulated by protein enzymes, etc. These characteristics were exploited to permit nanoassembly to be responsive to a specific stimulus and also ensure the specificity and precision in the construction of well-defined 3D nanostructures. Meanwhile, the assembly or disassembly of AuNPs, which results in distinct color changes due to the localized surface plasmon resonance, provides an excellent platform for the colorimetrically monitoring the DNA functions and the relevant biological processes.</p> <p>We have specifically investigated how the surface charges, the length and conformations of surface-tethered DNA polymers affect the assembly of AuNPs. We found that the colloidal stability of AuNPs can be well-tuned by nucleotides (small charged molecules) with various binding affinity to AuNP surface and/or different number of negatively-charged phosphate groups. This relies on the fact that nucleotides can bind to AuNP surface via nucleobase-Au interaction, and negatively charged phosphates stabilize AuNPs via electrostatic repulsion. This investigation allowed us to monitor protein enzymatic reactions where nucleotides are modified by alkaline phosphatase and to control the growth of AuNPs using nucleotides as capping ligands.</p> <p>We then investigated the effect of the length of DNA polymers on AuNP surface on AuNP colloidal stability. DNA-modified AuNPs are stabilized electrosterically at a relatively high salt concentration; the removal (or shortening) of the DNA molecules by enzymatic cleavage or the dissociation of DNA aptamers from AuNP surface upon binding to their target destabilizes AuNPs and results in AuNP aggregation. We attribute this to the loss of negatively-charged polymeric DNA molecules that initially served as colloidal stabilizers. This has been applied to the monitoring of enzyme (both protein enzyme and DNA enzyme) cleavage of DNA molecules, and DNA aptamer binding event to its target, respectively.</p> <p> We also studied how DNA polymer conformational changes influence AuNP colloidal stability, which has been employed to monitor DNA aptamer folding events on the AuNP surfaces. We found that AuNPs to which folded aptamer/target complexes are attached are more stable towards salt induced aggregation than those tethered to unfolded aptamers. Experimental results suggested that the folded aptamers were more extended on the surface than the unfolded (but largely collapsed) aptamers in salt solution. The folded aptamers therefore provide higher stabilization effect on AuNPs from both the electrostatic and steric stabilization points of view.</p><p> Finally, we demonstrated the well-defined assembly of AuNPs using long (hundred nanometers to microns) single-stranded (ss) DNA molecules as template in a three-dimensional (3D) fashion. Specifically, these long ssDNA containing repeating units are generated by protein enzymatic reaction (DNA extension through rolling circle amplification) on AuNP surface. The resultant product provides a 3D-like scaffold that can be subsequently used for periodical assembly of complementary DNA-attached nanospecies. </p> <p> We also expect that the facile colorimetric biosensing assays developed in this thesis work provide an attractive means to study biomolecular behaviors (e.g, biorecognition and conformational changes) on the surface, and to investigate other common DNA (or RNA) structural (e.g., triplex, G-quadruplex, hairpin, i-motif) and protein structural transitions.</p> <p> Finally, this thesis work provides some novel and general strategies for the control of nanoassemblies by tuning surface charges and surface-tethered polymers. We expect these principles can also be applied in other AuNP-based sensing platforms that exploit interparticle interactions and in the construction of well-defined nanostructures which involves other types of nano-scaled materials (e.g., quantum dots, nanotubes, nanowires, etc).</p> / Thesis / Doctor of Philosophy (PhD)

The present thesis titled “Molecular Modulation of Material Properties: Stud- ies on Nanoparticles, Nanoassemblies and Low Molecular Mass Gelator” deals with the preparation, characterization, and investigations into the properties of gold nanoparticles coated with novel thiols. The coverage of nanoparticle surfaces with these thiols renders them with special characteristics that will be of interest in biological and sensor applications. Also, a novel low molecular mass tetrameric sugar-based hydrogelator was synthesized and its gelation properties were studied in detail. Chapter 1 gives a general introduction and an overview about Nanomaterials, with emphasis towards nanoparticles of gold, which form the basis of this work. It delves with the history of research in noble metal nanoparticles, their interesting electronic and optical properties, the present methods of synthesis of high quality nanoparticles of noble metals, numerous potential applications of these novel materials, as well as the challenges in their real-life applications, and ends with the future outlook of this field of research. Chapter 2 describes the synthesis and characterization of three cationic lipid-like disulfides whose molecular structures are shown in Fig. 2.1. Gold nanoparticles capped with these molecules were then synthesized in small size dispersion by a simple one-phase protocol. These particles exhibited remarkably different solubility properties that were dictated by the molecular structure of the capping agent. The nanoparticles were characterized by a variety of techniques like UV-visible spec- troscopy, Transmission Electron Microscopy (TEM), proton Nuclear Magnetic Resonance (1H NMR), Fourier Transform Infra-red (FTIR) spectroscopy, and Zeta Potential measurements. These nanoparticles were then examined for their interactions (structural formula) Figure 1: Chemical Structures of the cationic lipid-like thiols used for nanoparticle preparation with dipalmitoyl phosphatidyl choline (DPPC) vesicles as model biological membranes. TEM, UV-vis, and Differential Scanning Calorimetry (DSC) were employed to probe the interactions. It was found that the capping agent of the nanoparticle had a strong bearing upon the interactions of the nanoparticles with DPPC vesicles. Chapter 3 describes the assembly of hydrophilic cationic nanoparticles upon elec- trostatic interaction with a variety of anionic surfactants. The chemical structures of some of the anions employed in the study, as well as a schematic of cationic nanopar- ticle are shown in Fig. 2. Upon ion pairing with long-chain anionic surfactants, the hydrophilic cationic nanoparticles were completely hydrophobized. They could then be phase-transferred to organic layer. TEM showed that nanoparticles assemble in to a variety of mesostructures upon ion-pairing with anions. The aggregate formation was found to depend critically upon length of the hydrophobic alkyl chain as well as the head-group of the anion. Isothermal Titration Calorimetry (ITC) was employed to probe the interactions of these nanoparticles with anions. It was found that the anions that resulted in nanoparticle precipitation displayed exothermic interactions with the nanoparticle. Chapter 4 deals with the synthesis of -thiolated metal chelator derivatives whose structures are shown in Fig. 3. The molecules are based on well-known chelators viz. iminodiacetic acid and bis-(2-pyridylmethyl)amine. While the first one is carboxylic acid-based chelator, the second one is pyridine-based. Nanoparticles coated with these chelators were synthesized in a size-controlled manner. These nanoparticles exhibited pH-controlled reversible assembly. However, while S-IDA based nanoparticles aggregated at low pH values, the S-BPA based nanoparticles aggregated in high pH regimes. Mixed monolayer protected gold nanoparticles were synthesized by employing S-BPA and C12H25SH as capping agents. It resulted in the formation of nanoparticles in low size-dispersion. These nanoparticles were characterized by 1H NMR spectroscopy to infer the ratio of the two capping agents on the nanoparticle surface. These nanoparticles demonstrated metal-ion induced aggregation. It was found that the nanoparticles could differentiate Cu2+ ions from other ions, and immediately formed aggregates in presence of Cu2+ ions. Chapter 5 describes the synthesis of novel mono-thiolated “Gemini” surfactants for nanoparticle synthesis. Gemini surfactants with different spacers were prepared. These surfactants had a 12-n-12 kind of molecular structure as shown in the Fig. 4. Upon preparation of nanoparticles with these thiols, the resulting material was soluble in water in the case of rigid thiols like D2S and DBPS Chapter 6 deals with the synthesis and hydrogelation properties of a low molecular mass hydrogelator based on an azobenzene based tetrameric sugar derivative (Fig. 5). The pKa of carboxylic acids in the molecule were determined using 13C NMR. The trans-to-cis isomerization of the compound was probed by time-dependent UV-vis studies. The sugar derivative exhibited pronounced hydrogelation capacity, gelling water at micromolar concentration. The gel formed was characterized extensively (structural formula) Figure 2: Schematic of cationic nanoparticles and molecular structures of the anions employed for nanoparticle assembly (structural formula) Figure 3: Chemical structures of metal-chelator containing thiols employed for the pH-controlled and metal-ion mediated nanoparticle assembly (structural formula) Figure 4: Schematic of cationic nanoparticles and molecular structures of the anions employed for nanoparticle assembly (structural formula) Figure 5: Chemical Structure of azobenzene-based tetrameric sugar derivative exhibit- ing pronounced hydrogelation using melting temperature analysis, UV-vis, FT-IR, circular dichroism spectroscopy and scanning electron microscopy. The resultant gel exhibited impressive tolerance to the pH variation of the aqueous phase and gelated water in the pH range of 4 to 10. While UV-vis and CD spectroscopy indicated that pronounced aggregation of the azobenzene chromophores in the gelator was responsible for gelation, FT-IR studies showed that hydrogen bonding is also a contributing factor in the gelation process. The melting of gel was found to depend upon the pH of the aqueous medium in which gel was formed. The gel showed considerable photostability to UV irradiation indicating tight intermolecular packing inside gelated state that render azobenzene groups in the resultant aggregate refractory to photoisomerization. The electron micrographs of the aqueous gels thus formed showed the existence of spongy globular aggregates in such gelated materials. Addition of salts to the aqueous medium led to a delay in the gelation process and also caused remarkable morphological changes in the microstructure of the gel. Appendix A describes the employment of ligand-free palladium nanoparticles towards efficient catalysis of Heck and Suzuki reactions in aqueous medium. Hexadecyl trimethylammonium bromide was employed as the surfactant to achieve solubilization of organic compounds in aqueous medium. UV-vis and TEM investigations into the formation of nanoparticles in the reaction media were undertaken. These studies indicate that the nanoparticles were formed by reduction of potassium tetrachloropalladinate by methyl acrylate used as one of the reactants. TEM investigation indicated the formation of nanoparticle assemblies upon solvent drying. Efficient and catalytic synthesis of a number of organic compounds could be achieved in high yield.

siRNA therapy is an emerging technique that reduces protein expression in cells by degrading their mRNAs via the RNA interference pathway (RNAi). Diseases such as cancer often proliferate due to increased protein expression and siRNA therapy offers a new method of treatment for those diseases. Although siRNA therapy has shown success in vitro, it often fails in vivo due to instability in the blood stream. To overcome this limitation, delivery vehicles are necessary for successful transfection of siRNA into target cells and cationic polymers have been widely studied for this purpose. However, complexes between siRNA and delivery vehicles made from cationic polymers exhibit stability issues in the blood stream which results in toxicity and low transfection. This work hypothesizes that improvement of vehicle/siRNA complex stability will improve siRNA transfection efficiency. To test this, the contributions and outcomes of poly(ethylene glycol) [PEG] shell and hydrophobic core modification to a polyethylenimine (PEI) based tethered nanoassemblies (TNAs) were examined. Initially, hydrophobic modification of palmitate (PAL) to the core of the TNA yielded improved transfection efficiency due to an enhanced endosomal escape capability. However, this modification also reduced the TNA/siRNA complex stability. This indicated that the core hydrophobicity must be balanced in order increase stability while increasing transfection efficiency. Additionally, TNAs made from PEG and PEI did not cause transfection in our initial study. The PEG shell density was found to be too great and thereby reduced transfection efficiency. Reducing the PEG density by lowering PEG molecular weight, reducing attachment percentage, and removing small PEI impurities from the synthesis stock increased overall transfection efficiency and unimolecularity of the TNA complexes. This indicated that the shell composition of the TNA must be tuned in order to improve particle design. Further study of the hydrophobically modification to TNAs yielded unintended effects on the transfection efficiency evaluation assay. These particles exhibited an siRNA independent reduction in the reporter protein used to observe transfection, or a false positive effect, that was not previously observed. It was found that this false positive was influence mainly by the hydrophobic group rather than the cationic polymer backbone. Cellular stress was observed in cells dosed with the hydrophobically modified TNAs which lead to over ubiquitination and rapid degradation of the luciferase protein. This demonstrated that core components of TNAs could cause cellular stress and influence interaction outside of the TNA. Overall, this work demonstrates that hydrophobic core and PEG shell modification require balancing and consideration to improve properties of future cationic polymer based siRNA delivery vehicle design.

Over the last few decades, a vast research is going on, to study the optical properties of the nano particles i.e., metal and semiconductors thoroughly. Till date most of the optical studies are based on single particle measurement of a quantum dot (QD) or a chromophore under the influence of an external plasmonic field stimulus. In this the-sis, we tried to address the energy transfer at non local level on a layer of compact, monolayer QD assemblies over micro meter range. The energy transfer occurs in the presence of external field of metal particles or nanorods leads to the enhancement or quenching the emission from a layer of QDs. Chapter 1 is introduction to the basic theoretical aspects of excitons in semiconductor (QDs) and its optical properties under strong confinement regime. The discussion is followed with the optical properties of gold nanoparticles and rods, describing size and shape dependent variation of absorption properties, based on Mie and Mie-Gans theory. Theoretical background of collective effects in QD assemblies based on exciton-plasmonic interactions at single particle level as well as polarization based plasmo-nenhanced fluorescence has been subjected. Experimental techniques are explained in chapter 2 which contains the details of the synthesis of polymer capped nanoparticles with the respective characterization. A discussion on the synthesis methods for cadmium selenide QDs, gold nano particles and the rods with different polymer cap-ping legends and the related capping exchange methods. The thin film preparation of QD monolayers as well as hybrid nano assemblies using several techniques, i.e., Langmuir-Blodgett (LB), dip coat methods are provided. Further the details of surface morphology of the prepared thin films has been studied by different microscopic techniques i.e., atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The details of the PL emission measurements of these hybrid arrays using confocal, Raman and polarization based near field scanning optical microscope (NSOM) modes followed with the life time measurements. In third chapter, the substantial strong coupling and collective emission regime is engineered in the QD monolayer films embedded with tiny gold nano particles keeping the QD density same. Tuning the photoluminescence (PL) of semiconducting QD assemblies using small Au NPs in different ratio, different packing density and extent of spectral overlap between QD photoluminescence and the metal nanoparticle absorbance has been discussed. We provided possible experimental and theoretical evidence for the plasmon-mediated emergence of collective emission and enhanced quantum efficiency in these QD films with the consolidation of multiple emitters and multiple NPs. The quantum efficiency of these hybrid assemblies is further explored with different material as well as the size effect of metal nano particles. Chapter 4 comprises the experiment results of the self-assembled compact and partially aligned gold nano rod (GNR) arrays on QD monolayer films. We experimentally demonstrated the quantum efficiency of these QD hybrid assemblies is gaining max-imum when the longitudinal surface plasmon resonance (LSPR) absorption maxima of GNR arrays is resonant with the QD monolayer PL maxima and is always non-existent for the off resonant case. Further, we reported the variability in the size and morphology of these GNR domains leads to the maximum achieved enhancement as well as anisotropy value in comparison with isolated rods and the explored conditions to further enhance the efficiency in these QD hybrid assemblies.

This research is divided into three major parts. In part I, the critical supersaturations required for the homogeneous nucleation of 2,2,2-trifluorothanol (TFE) vapor have been measured over a temperature range (266-296 K) using an upward thermal diffusion cloud chamber (DCC). The measured supersaturations are in agreement with the predictions of both the classical and the scaled theory of nucleation. Moreover, the condensation of supersaturated TFE vapor on laser-vaporized magnesium nanoparticles has been studied under different experimental conditions, such as the supersaturation, the pressure and the electric field. In part II, the laser vaporization controlled condensation (LVCC) technique was used to prepare Au-Ag alloy nanoparticles in the vapor phase using designed targets of compressed Au and Ag micron-sized powder mixtures of selected composition. The results showed that the optical properties of these nanoparticles could be tuned depending on the alloy composition and the laser wavelength. Different intermetallic nanoparticles (FeAl and NiAl) from the vapor phase has also been prepared, using the same approach.In this work, the fraction of the charged particles generated during the laser vaporization process was used to prepare a new class of nanoparticle assemblies in the LVCC chamber under the influence of an electric field. The results showed that the electric field required to induce the formation of these nanoassemblies is material and field dependent. By coupling the LVCC chamber with the differential mobility analyzer, size-selected nanoparticles have been prepared in the vapor phase. The prepared nanoparticles were characterized by different techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy. In part III, new methods were developed to prepare nanoparticle-polymer composites from the vapor phase. In the first method, the LVCC method was used to prepare a carbonaceous cross-linked resin, with different nanoparticles (Ni, Pt and FeAl) embedded inside. In the second method, free radical-thermally initiated polymerization was used to polymerize a monomer vapor of styrene on the surfaces of activated Ni nanoparticles.

Theranostics is an emerging treatment approach that combines diagnostics with therapy in order to personalize treatment regimens for individual patients and decrease cancer mortality. Previously, nanoparticles entrapping conventional fluorescent dyes were developed for cancer theranostics, but fluorescent nanoparticles did not allow clinicians to significantly improve cancer treatments. The use of fluorescent dyes that are sensitive to solvent acidity (halo-fluorochromism) and polarity (solvato-fluorochromism) may overcome the limitations of fluorescent nanoparticles and improve cancer therapy by enabling researchers to detect chemical properties within the nanoparticle core environment. The model halo- and solvato-fluorochromic dye Nile blue was attached to the core of nanoscale drug delivery systems called polymer nanoassemblies (PNAs), which were created by tethering hydrophilic polymers and hydrophobic groups to a cationic polymer scaffold. The fluorescence of empty PNAs increased by 100% at pH 5.0 compared to pH 7.4, and the fluorescence of drug-loaded PNAs increased up to 300% compared to empty PNAs. A comparison of the fluorochromic properties between PNAs with various core properties indicated that both hydrophobic pendant groups and scaffold amines contributed to the fluorochromism of PNAs. The halo-fluorochromism of PNAs allowed investigators to minimize the detection of fluorescence signals in healthy organs such as the liver. Fluorescence imaging of halo-fluorochromic PNAs diffused into tissue mimics indicated that fluorescence of PNAs in tissues increased by 100% at pH 7.0 compared to pH 7.4. In addition, halo-fluorochromic PNAs identified the acidic perimeter surrounding metastatic tumors in orthotopic metastatic tumor models. Computational simulations of metastatic lesions verified that some halo-fluorochromic PNAs accumulate in the hypoxic/acidic regions of metastatic tumors following intravenous administration. These simulations also indicated that the accumulation of PNAs in the hypoxic regions of tumors doubles at 12 hours post-treatment compared to 1.8 hours post-treatment. The solvato-fluorochromism of PNAs enabled the fluorescence-based measurement of drug release from the nanoassembly core during dialysis-based drug release measurements. Solvato-fluorochromic methods indicated faster drug release rates than HPLC-based methods. Mechanistic modeling of drug release indicated that solvato-fluorochromic methods were unaffected by released drugs that interfered with HPLC-based methods. However, mechanistic modeling also indicated that drug rebinding and diffusion did not account for all of the differences between drug release rates determined by solvato-fluorochromic- and HPLC-based methods. Based on this evidence, it was hypothesized that solvato-fluorochromic drug release methods measure drug diffusion from near the scaffold of PNAs in a small region of the nanoassembly core, and that this process contributes to overall drug release but does not indicate apparent drug release rates for PNAs. In order to develop PNAs for potential clinical applications, ionizable amines were removed from the polymer scaffold to increase drug loading and sustain the release of model drugs carfilzomib and docetaxel. The removal of primary amines decreased drug diffusivity in the core of PNAs (D from 3.9*10-18 cm2/s to 0.1*10-19 cm2/s) and increased the drug release half-life (t1/2 from 4 to 26 hours). The controlled release of carfilzomib from PNAs reduced drug metabolism by 60% for up to one hour and sustained proteasome inhibition in cancer cells at 72 h post-treatment compared to free drug. Overall, this work provides insight into the design of theranostic nanoparticles with beneficial properties for improving cancer treatment.

L’idée directrice de ce travail de thèse était d’introduire au sein de mésophases lipidiques des molécules de β-cyclodextrine (βCD) amphiphiles obtenue par bio-estérification afin d’obtenir des nano-assemblages plurimoléculaires et multi-compartimentés combinant trois fonctions essentielles pour le transport ou la vectorisation de molécules thérapeutiques : (i) la capacité d’incorporer une substance d’intérêt par formation de complexe d’inclusion avec la cyclodextrine ; (ii) être biocompatibles et aptes à passer facilement les barrières biologiques ; (iii) pouvoir co-incorporer une seconde substance d’intérêt, hydrophile ou hydrophobe, dont l’action biologique soit différente de celle assurée par la première substance. L’ensemble des travaux ont porté sur le dérivé βCD-C10 polysubstitué en face secondaire par des chaînes hydrocarbonées en C10 avec un degré moyen de substitution de 7,5. L’association de ce dérivé avec trois catégories de lipides a été envisagée : des tensioactifs micellaires non-ioniques (Brij 98, Polysorbate 80, n-dodécyl-β-D-maltoside), un lipide lyotrope non lamellaire formant des mésophases de type cubique bicontinue (monooléine), un phospholipide s’auto-organisant en bicouches propices à l’obtention de vésicules (dimyristoyl phosphatidylcholine). Selon une démarche principalement physico-chimique, différentes techniques ont été mises en œuvre pour caractériser les systèmes mixtes lipide/βCD-C10 aux échelles moléculaire et supramoléculaire : diffusion-diffraction des rayons X, calorimétrie différentielle, spectrophotométrie d’absorption UV-visible, spectroscopie de fluorescence, diffusion de la lumière statique (turbidimétrie) ou quasi-élastique, microscopie optique et microscopie électronique par cryo-transmission. L’ensemble des résultats démontrent que le dérivé βCD-C10 forme spontanément ou selon un protocole très simple, des assemblages plurimoléculaires mixtes avec les trois catégories de lipides, assemblages dont la topologie dépend de la structure chimique du lipide et du taux de cyclodextrine amphiphile incorporé (tubules, vésicules uni- ou oligolamellaires, cubosomes). Ces assemblages sont stables et capables d’incorporer une substance hôte hydrophobe, notamment les vésicules mixtes tensioactif non-ionique/ βCD-C10 et les cubosomes mixtes monooléine/P80/ βCD-C10. / The key idea of this Ph.D. thesis is to introduce amphiphilic β-cyclodextrin molecules (βCD), obtained by bio-transesterification, within lipid mesophases in order to obtain multi-compartment plurimolecular nano-assemblies, which combine three essential functions for transport or delivery of therapeutic molecules: (i) capacity to incorporate a substance of interest through formation of inclusion complexes with the modified cyclodextrin; (i) biocompatibility and ability to easily pass the biological barriers; and (iii) possibility for co-encapsulation of a second substance of interest, a hydrophilic or a hydrophobic one, whose biological action is different from that provided by the first substance. The performed Ph. D. work focused on the β-cyclodextrin derivative βCD-C10 with an average degree of substitution of 7.5 of the secondary face of the macrocycle by hydrocarbon chains C10. The association of this derivative with three classes of amphiphiles was studied: (i) nonionic micellar surfactants (Brij 98, Polysorbate 80, n-dodecyl β-D-maltoside), (ii) a lyotropic nonlamellar lipid forming bicontinuous cubic mesophases (monoolein), and (iii) a phospholipid (dimyristoyl phosphatidylcholine), which self-ssembles into bilayer membranes permitting the production of vesicles.The employed physical-chemical approach involved different techniques for characterization of the mixed βCD-C10/lipid systems at molecular and supramolecular levels: cryo-transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, UV-visible absorption spectroscopy, fluorescence spectroscopy, turbidimetry, and quasi-elastic light scattering.The obtained results indicated that the βCD-C10 derivative forms spontaneously (or via a very simple preparation protocol) plurimolecular mixed nano-assemblies with the three types of lipids. The topologies of the resulting nano-assemblies essentially depend on the chemical structures of the lipids and the degree of incorporation of the amphiphilic cyclodextrin (tubules, unilamellar or oligolamellar vesicles, and cubosomes). These assemblies, namely the mixed vesicles of nonionic surfactant/βCD-C10 and the cubosomes of mixed monoolein/P80/βCD-C10 compositions, are stable and capable of incorporation of hydrophobic guest substances.

Existing methods for pathogen/pollutant detection or wound infection monitoring employ high-cost instruments that could only be operated by trained personnel, and costly device-based detection requires a time-consuming field-to-lab process. This expensive process with multiple prerequisites prolongs the time that patients must wait for a diagnosis. Therefore, improved methods for point-of-care biosensing are necessary. In this study, we aimed to develop a direct, easy-to-use, portable, low cost, highly sensitive and selective sensor platform with the goal of pollutant detection and wound infection/cancer migration monitoring. This study has two main parts, including microfluidic, electrical, and optical sensing platforms. The first part, including chapters 2, 3, and 4, focuses on Bisphenol A (BPA) lateral flow assay (LFA) detection; the second part, including chapter 5 focuses on the electrical sensing platform fabrication for one of the markers of inflammation, matrix metalloproteinases-9 (MMP-9), monitoring/detection. In chapters 2, 3, and 4, we found that the few lateral flow assays (LFAs) established for detecting the endocrine-disrupting chemical BPA have employed citrate-stabilized gold nanoparticles (GNPs), which have inevitable limitations and instability issues. To address these limitations, in chapter 2, a more stable and more sensitive biosensor is developed by designing strategies for modifying the surfaces of GNPs with polyethylene glycol and then testing their effectiveness and sensitivity toward BPA in an LFA. In chapter 3, we describe the development of a new range-extended bisphenol A (BPA) detection method that uses a surface enhanced Raman scattering lateral flow assay (SERS-LFA) binary system. In chapter 4, we examine advanced bisphenol A (BPA) lateral flow assays (LFAs) that use multiple nanosystems. The assays include three nanosystems, namely, gold nanostars, gold nanocubes, and gold nanorods, which are rarely applied in LFAs, compared with general gold nanoparticles. The developed LFAs show different performances in the detection of BPA. In chapter 5, a stable electrical sensing platform is developed for MMP-9 detection.