The objective of this project was to develop new controlled drug delivery systems using nanomeric particles and characterize the delivery of drugs into cells in real time by digital fluorescence imaging microscopy techniques. The project is based on the idea that it could be possible to improve efficacy of drug molecules when encapsulated in nanometer-sized particles. Due to their small dimensions the particles could permeate through cells and tissues and even through the blood brain barrier. The anti-cancer drug Doxorubicin was encapsulated into biodegradable Poly (DL-lactideco- glycolide) (PLGA) nanoparticles by simple nanoprecipitation method. The small size of these particles (<200nm) could be beneficial to realize passive tumor-targeted drug delivery through enhanced permeability and retention (EPR) effects. These drug-containing particles showed a sustained release profile. Fluorescence images indicated that these particles can be internalized by human breast cancer MCF-7 cells by non-specific endocytosis. The bioactivity of the drugs was also tested against cell culture. The results indicated that DXR-loaded PLGA nanoaprticles could be used to deliver Doxorubicin into breast cancer cells.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Lead, nickel and cobalt dithiocarbamates complexes were synthesized using methanol and water as solvents. All complexes were refluxed at 60 °C, cooled at room temperature, washed with methanol to remove the impurities and dried under the fume hood. A combination of Fourier transformer infrared (FTIR), elemental analysis (EA) and thermogravimetric analysis (TGA) were used to characterize these complexes. There was shifting of bands from low to high frequencies of the dithiocarbamates complexes compared to benzimidazole derivatives. The absence of the N-H band and the presence of new C=S bands confirmed that the complexes can be used in the preparation of metal sulphide nanoparticles. Elemental analysis showed that there was a percentage mismatch for the complexes I, III, IV and V. Complexes II and VI calculated percentages were within the limits with the found percentages except for sulphur which was low. The TGA curves decomposed to form a mixture of metal and metal sulphides for complex I, II, III and IV except for complex VI which gave metal sulphide only. All benzimidazole complexes decomposed at higher temperatures and were considered as stable complexes. Lead sulphide (PbS) is an important group IV-VI metal chalcogenide semiconductor. It has a direct narrow band gap of 0.41 eV at 300K and a large excitonic Bohr radius of 18 nm. Lead sulphide absorption band can be tuned to anywhere between near IR to UV (0.4μm) covering the entire visible spectrum, while achieving the quantum confinement region. The synthesis of lead sulphide nanoparticles was conducted by varying the effect of the reaction conditions such as the type of capping agents and temperature. Lead dithiocarbamate complex derived from benzimidazole, [Pb(S2N2C8H5)2] was thermolysed in hexadecylamine (HDA) and trioctylphosphine oxide (TOPO) at different reaction temperatures (140, 160 and 180 °C) to produce HDA and TOPO capped PbS nanoparticles. The nanoparticles were characterized using X-ray diffraction (XRD) for structural analysis, transmission electron microscopy (TEM) for shape and size, Ultraviolet visible (UV/Vis) and Photoluminescence (PL) spectroscopy for optical properties. An increase in temperature gave a decrease in the sizes of the nanoparticles when using the HDA capped lead benzimidazole dithiocarbamate complex. The observed morphology was cubes. TOPO capped lead benzimidazole dithiocarbamate complex gave no specific trend when temperature was varied. A cross-like layer with quasi spherical particles on top was observed at 160 °C. At 180 °C, the cross-like layer decomposed into rods- like materials with quasi spherical particles on top for TOPO capped PbS nanoparticles. For lead 2-methylbenzimidazole [Pb(S2N2C9H7)2] dithiocarbamate complex, TOPO capped PbS produced agglomerated cubic morphology at low temperature but as the temperature was increased agglomerated cylindrical shapes were observed. HDA capped PbS produced polydispersed nanocubes which were increasing in size when the temperature was increased. Nanoparticles displayed a blue shift in band edges with good photoluminescence behaviour which was red shifted from their respective band edges all temperatures and capping agents. XRD confirmed the crystal structure of cubic phase (galena) of PbS at all temperatures except for HDA capped PbS nanoparticles at 140 °C from lead benzimidazole dithiocarbamate complex which confirmed the crystal structure of face-centred cubic phase of PbS nanoparticles. Nickel sulphide has much more complicated phase diagram than cobalt sulfides and iron sulfides. Their chemical composition has many crystalline phases such as α-NiS, β=NiS, NiS2, Ni3S2, Ni3S4, Ni7S6 and Ni9S8. Ni3S2 phase has shown potential as a low-cost counter electrode material in dye sensitised solar cells, while the α-NiS phase has been applied as a cathode Material in lithium-ion batteries. The synthesis of nickel sulphide nanoparticles was done by varying the effect of the reaction conditions such concentration and temperature. Nickel benzimidazole dithiocarbamate [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni (S2N2C9H7)2] dithiocarbamates complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) and precursor concentrations (0.30, 0.35 and 0.40 g) to produce HDA capped NiS nanoparticles. It was observed that increasing both temperature and precursor concentration increased the size of the nanoparticles. Anisotropic particles were observed for both complexes when varying precursor concentration and temperature. Nickel benzimidazole dithiocarbamate complex produced stable shapes (spheres and cubes) of nickel sulphide nanoparticles. Nickel 2-methylbenzimidazole dithiocarbamate complex produced a mixture of spheres, cubes, triangles and rods nickel sulphide nanoparticles at all concentrations. But when varying temperature, it only produced that mixture at 160 °C. The optical measurements supported the presence of smaller particles at all temperatures and concentrations. XRD showed the presence of C7OS8 and pure nickel as impurities. However, the crystal structure of cubic Ni3S4 was observed at low temperatures and an introduction of monoclinic NixS6 at high temperature (180 °C) when varying temperature for both complexes. When varying concentration using nickel benzimidazole dithiocarbamate complex, XRD showed the presence of NiSO4.6H2O impurities at high temperatures. At 160 °C a mixture of hexagonal NiS and cubic Ni3S4 was observed. At low temperatures only nickel as a metal was found as an impurity and the crystal structure of cubic Ni3S4 was observed. When nickel 2-methylbenzimidazole complex was used, C7OS8 and pure nickel were found as impurities but the crystal structure of cubic Ni3S4 was observed. Cobalt sulphide (CoS) belongs to the family of group II-IV compounds with considerable potential for application in electronic devices. They have a complex phase diagram and their chemical composition have many phases such as Co4S3, Co9S8, CoS, Co1-xS, Co3S4, Co2S3 and CoS2. The synthesis of cobalt sulphide nanoparticles was conducted by varying the effect of temperature on size and shape of the nanoparticles. Nickel benzimidazole dithiocarbamate, [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni(S2N2C9H7)2] complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) to produce HDA capped CoS nanoparticles. Cobalt benzimidazole dithiocarbamate complex produced close to spherical shapes nanoparticles at all temperatures. The images showed that as temperature was increased, the size of the particles decreased. All the main reflection peaks were indexed to face-centred cubic Co3S4 and there were some impurities of C7OS8 at all temperatures. The optical measurements supported the presence of smaller particles at all temperatures. Cobalt 2-methylbenzimidazole dithiocarbamate complex produced big and undefined morphology. The optical properties were also featureless and XRD only showed impurities of C7OS8. The impurity is thought to be generated from a side reaction between benzimidazole and carbon disulphide to give this persistent organic moiety.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment for the degree of Master of Science in Chemistry. Johannesburg 2016. / In the current study, different platinum-hollow carbon sphere catalysts were synthesized for use as electrocatalysts in low temperature fuel cells such as proton exchange membrane fuel cells (PEMFCs). The support material was synthesized via a hard templating method using mesoporous silica (synthesized using a modified Stöber method) as a sacrificial template. In fuel cells, one aim is to ensure that as much platinum as possible is present on a given electrode while keeping the entirety of the catalytic layer as thin as possible (i.e. with the minimum amount of carbon). One approach to achieving this was to make the hollow carbon spheres as small as possible, starting of course with the templating material. It was found that tailoring the molar ratios between the two co-solvents (that is water and ethanol) during Stöber synthesis was the key to achieving particles as small as approximately 150 nm with a uniform shape, size, and significant yields of up to 5.00 g. Another focal point in terms of the template material was achieving a silica structure that consisted of a solid core, and a distinctly mesoporous shell. Two different surfactants were explored in order to fabricate these structures; namely octadecyltrimethoxysilane (C18TMS) and cetyltrimethylammonium bromide (CTAB). It was found that of the two, the C18TMS resulted in more distinctly formed mesoporous silica layers with higher measured specific surface areas. Because the type of support material greatly influences the catalytic behaviour of the loaded catalysts, two different carbonization techniques were explored; namely the bubbling method using toluene as a carbon source, and a nanocasting method where resorcinol formaldehyde (RF) was the carbon source. The toluene-synthesized hollow carbon spheres had advantages over their RF-synthesized counterparts in that they were more thermally stable and had a more graphitic crystalline carbon framework. The RF-synthesized carbon, however, possessed a pseudo-capacitance due to surface carbon-oxygen groups, as well as a higher specific surface area, which resulted in the RF-carbon cyclic voltammetry profile spanning a larger current range in microampere per square centimetre. The effect of the size of the support materials was also explored; comparing 350 nm and 150 nm hollow carbon spheres. Besides the type of carbon, the metal precursor used to synthesize the catalyst nanoparticles was also explored, with either platinum(II)chloride (PtCl2) or platinum(II)acetylacetonate [Pt(acac)2] being used as the platinum source. It is also known that achieving high metal yields using conventional methods is quite difficult, and so an easier, quicker and less wasteful method was also explored; comparing the traditional wet-impregnation (WI) method with a chemical vapour deposition (CVD) method. Ultimately, it was found that platinum loaded on top of small-sized toluene-synthesized hollow carbon spheres using the CVD method and Pt(acac)2 as the metal precursor was the better catalyst in terms of oxygen reduction (determined using linear sweep voltammetry measurements); outperforming even commercial Pt/C catalysts as a result of improved mass transfer afforded by the voided cores of the hollow carbon spheres. The ability of a catalyst to withstand the reaction conditions present in a PEM fuel cell (i.e. oxygen-rich environments) was also considered. The stability of the catalysts was tested using chronoamperometry measurements in an oxygen-saturated perchloric acid solution. It was evident that the platinum loaded on the inner shells of the hollow carbon spheres showed far superior stability to those loaded on the outside surface. This was attributed to the qualities bestowed by the carbon shell around the platinum nanoparticles, protecting said platinum against the consequences of support corrosion due to the oxygenated environment; consequences such as metal sintering and interaction with surrounding carbon supports for example. These encapsulated catalysts, however, displayed a decrease in electrocatalytic activity compared to the catalysts with top-loaded platinum. In conclusion, the study of different platinum-carbon catalysts studied in the current work revealed that (a) loading platinum on top of small sized toluene-synthesized hollow carbon spheres using a CVD method and Pt(acac)2 as a metal precursor resulted in a highly active oxygen reduction catalyst, while (b) loading platinum on the inside surface of the hollow carbon spheres under the dame conditions resulted in a more electrocatalytically stable catalyst. / LG2017

Ph. D., Faculty of Science, University of the Witwatersrand, 2011 / Different cadmium, cobalt and zinc complexes of substituted thioureas, dithiocarbamates and thiuram di/monosulfides were synthesized using ethanol or water as solvents. The synthesis of dithiocarbamates complexes were performed at room temperature while the rest were refluxed at 70 oC. The complexes were easy to synthesize, of low cost and stable in air and were obtained in good yields. The complexes were characterized using various instruments, such as infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy, elemental analyzer, thermogravimetric analysis (TGA) and X-ray crystallography. The complexes were found to coordinate the ligands through sulphur atom, instead of nitrogen atom. This was concluded after shifts to higher or lower wavenumbers were observed from the infrared spectra of the complexes as compared to their free ligands. The 1H NMR also depicted formation of the complexes, with complexes peaks shifting to downfield as compared to the free ligands. There were also signs of broad NH peaks especially for substituted thiourea complexes. The crystals grown from complex II (diphenylthiourea cadmium complex) depicted a tetrahedral geometry, with two sulphur and two chlorine atoms binding to the central atom which is cadmium. The easily synthesized complexes were thermolysed in HDA, TOPO or a mixture of the two to form metal sulphide nanoparticles. The role of the above capping agents or ligands was to control particles growth and prevent them from aggregation. A single source precursor route was employed in synthesizing hydrophobic semiconductor nanoparticles, which are also known as (QDs) quantum dots. Various shapes, which are rods (mono-, bi- and tripods), spheres and hexagonal were revealed through transmission electron microscope (TEM). The sizes of these particles ranged from 1 to 12 nm in diameter. Other instruments used for characterising the as-synthesized semiconductor nanoparticles include X-ray diffractometer (XRD), UV-Visible and Photoluminescence spectroscopy. The optical properties of the particles as determined by the UV-Visible spectroscopy revealed some differences as compared to the bulk materials. All the absorption spectra were blue shifted to the bulk materials signifying finite size of the particles. The XRD peaks observed were broad as compared to the bulk ones, which also signified small particles size. Two phases, which are hexagonal and cubic, were revealed from the XRD. viii The hydrophobic semiconductor nanoparticles or quantum dots synthesized were then transferred into water soluble using ligand exchange method. The chloroform and pyridine routes were used to synthesize hydrophilic semiconductor nanoparticles, with pyridine route being preferred. The shape and size of the particles were not influenced by the transfer into water soluble since the experiments were performed at room temperature. This was confirmed by TEM analysis. The capping agents used after displacing water insoluble capping agents were sugars, which were soluble in water. The XRD pattern of the semiconductor nanoparticles/QDs (CdS) capped by sugars after ligand exchange through pyridine yielded multiple peaks which were difficult to assign. The attempt to employ ligand exchange method in transferring hydrophobic CoxSy and ZnS nanoparticles to hydrophilic CoxSy and ZnS nanoparticles proved unsuccessful. When the materials were centrifuged after the sugars were introduced as capping agents, some solid material settled at the bottom, with some floating on top of the solution. This was an indication that the materials were not miscible. The hydrophilic CdS, CoxSy and ZnS nanoparticles were also synthesized using direct method. In this method, the metal sources and capping (sugars) were dissolved in ethylene glycol at 100 oC. The sulphur sources were also dissolved separately in the same solvent. Upon completion, the latter solution was added to the former one. The particles were grown at 160 oC for an hour with ethylene glycol as a solvent. The morphology of the particles dominated through this method was spherical-like in shape. The crystallinity of CdS and ZnS nanoparticles depicted hexagonal and cubic phases depending on the complexes used. The XRD indicated the armophous nature of the cobalt sulphide nanoparticles, irrespective of the precursor used. Due to the toxicity problem of the quantum dots, especially CdS, the water soluble CdS capped by glucuronic acid, glucose and sucrose after ligand exchange were chosen for that study. However, results showed that the CdS used were not toxic. It was measured or deduced by checking the viability which remained above 90%. Add a bit of deductions about toxicity study here, just some of the general trends.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment for the degree of Master of Science in Chemistry. May 2013. / In relation to conventional water treatment methods, membrane separation has acquired a great audience due to its wide applicability, reliability, low cost, low energy demands, and ease of use. However, membrane fouling has been identified as the main downsizing factor in the application of this technology. To address this issue, several studies have suggested the use of inorganic additives for enhancement of the membrane antifouling properties. In this study, silver (Ag) decorated nitrogen doped carbon nanotubes (N-CNTs) dispersed into polyethersulphone (PES) membranes for potential use in water treatment. Firstly, N-CNTs were synthesised using the chemical vapour deposition (CVD) method. The black soot was functionalised and characterised using transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Brunner-Emmett-Teller (BET). The N-CNTs were found to have an average diameter of 15 nm. The functionalised N-CNTs were then decorated with Ag nanoparticles (AgNPs) using the Polyol method. The resultant product was also characterised using TEM, the AgNPs were found to have an average diameter of 6 nm. The N-CNTs and Ag/N-CNTs were then uniformly dispersed into (PES) membranes to form N-CNT/PES and Ag/N-CNT/PES blend membranes, respectively. The membranes were then characterised using several series of techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle analyser and a cross-flow filtration system. The blend membranes were investigated for any improved properties and tested for their efficiency in removing model pollutants (polyethylene glycol, humic acids, and bacteria) from water. The AFM results revealed a reduction in surface roughness from 23.9 nm for the pristine PES to 12.7 nm in the N-CNT/PES blend membranes. The mechanical stability increased from 3.7 MPa for the pristine PES to 4.4 MPa with a small addition of N-CNTs. Furthermore, the performance studies showed a 46% increase in pure water flux and a 13% increase in rejections for N-CNT blend PES membranes as compared to the pristine PES membrane. Antibacterial studies were also performed where Ag modified N-CNTs were found to inactivate Enterohaemorrhagic E. coli by almost twice the initial concentration in the bacterial suspensions. Finally, Ag/N-CNTs were immersed into PES membranes. The Ag/N-CNTs/PES membranes were then tested for their activity towards the bacteria.

No description available.

Chak, Chun Pong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 190-202). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

The use of nano/meso-particles (NP/MP) as constituent of topical formulations of drug and cosmetics has been a topic of considerable interest for the past 20 years. However, the transport mechanism of nanoparticle-associated drug/active following topical application on the skin is still unclear. No general answers have been obtained to such questions as the depth of intact NP penetration into the skin, the skin distribution of active substances, and the fate of the vehicles on/in the skin. The main objective of this thesis, therefore, was to observe the in vitro penetration of fluorescently-labeled nanoparticle vehicle and “active” on/within the skin by using laser scanning confocal microscopy (LSCM). Furthermore, the concentration profile of the “active” in the outermost skin layer, stratum corneum, has been assessed by using tape stripping technique combined with HPLC analysis. The factors, including particle size, hydrophobicity, shell thickness of nanocapsules and surface charge, have been investigated with regard to their abilities to influence the penetration of “active” into the skin. The methods for NP preparation and characterization have also been developed. The results demonstrated that the delivery of “active” into the stratum corneum from NP/MP were influenced by a number a factors, including particle size, hydrophobicity, surface charge and shell thickness of capsules. The “active” delivery (i) is greater from larger vectors; (ii) increases as the hydrophobicity of NP/MP increases; (iii) is favoured by cationic NP; (iv) is favoured from capsules with a smaller shell thickness. NP vehicle and “active” mainly co-localize in skin “furrows” and around hair follicles after topical application. No evidence shows NP penetrate beyond the superficial layer of the skin. In the stratum corneum, the “active” remains in part associated with NP, but the release f the “active” clearly occurs to some extent followed by its penetration into deep layers of the stratum corneum. Overall, through this work, the fate of nanoparticle vehicle and the “active” has been distinguished and the physicochemical properties of the nanoparticles that determine their behaviour once applied to the skin, and the kinetics with which an “active” is released, has also been understood.

The aims of this thesis are to design and synthesize non-viral cationic lipid vectors based on spermine, for the intracellular delivery of siRNA (short interfering RNA) and the subsequent siRNA mediated gene silencing. Two parameters were varied: the type of fatty acid and the cationic head-group. Among the symmetrical spermine conjugates, N4,N9-dierucoyl spermine (DES) resulted in higher siRNA delivery compared to N4,N9-dioleoyl spermine (DOS), while enhanced green fluorescent protein (EGFP) silencing in HeLa cells showed that the unsaturated fatty acid conjugates are more efficient than the saturated fatty acid ones, and cell viability was 75%-85% for conjugates with chain length ≥ 18. Two cationic lipids with guanidine head-groups, N1,N12-diamidino-N4,N9-dioleoylspermine and N1,N12-diamidino-N4-linoleoyl-N9-oleoylspermine, were more efficient in EGFP gene silencing compared to cationic lipids with shorter C12 (lauroyl) and very long C22 (erucoyl) chains, with cell viability (64%-83% for chain length ≥ 18). Changing the cationic headgroup to guanidine did not offer a significant advantage in gene silencing over the conjugates with terminal primary amine groups. The asymmetrical N4-linoleoyl-N9-oleoyl-1,12-diamino-4,9-diazadodecane (LinOS) resulted in the best gene silencing, while LigOS (with one lignoceroyl 24:0 chain) resulted in the best siRNA delivery. Conjugates with two unsaturated fatty chains generally resulted in better EGFP gene silencing, while conjugates with one saturated chain and one unsaturated chain resulted in better siRNA delivery. Increasing the chain length also resulted in increased siRNA delivery (cell viabilities of asymmetrical > 74%, LinOS 88%). siRNA lipoplexes prepared using mixtures of LinOS with either cholesterol or DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) resulted in increased siRNA delivery, and enhanced EGFP silencing, with LinOS/Chol mixture (1:2 molar ratio) resulting in the highest siRNA delivery and the best gene silencing (EGFP reduced to 20%). Temperature studies of intracellular entry showed that the majority of lipoplexes are internalized by endocytosis, however the majority of gene-silencing occurs due to lipoplexes internalized via another mechanism.

Nanoparticle toxicity has become a major topic of interest due to the inevitable exposure of these nanomaterials to both humans and the environment. Nanotechnology is a rapidly growing industry with diverse material resources and an extensive market for commercialization and introduction of nanomaterials into consumer products. The problem with this flourishing technology is that it has far outgrown research based on the safety and toxicity of the nanomaterials, which in bulk are generally nontoxic. The need for research in determining the toxic effects on cells and the implications it may have on the environment have grown but the different techniques, cell systems and nanoparticles employed are generally to diverse and conflicting in overall results that determination toxicity is nearly impossible. The need for a universal technique to study the interaction of nanoparticles with cells and decouple the molecular effects (chemical properties) from the“nanospecific" effects (including size, concentration, surface charge, functionality and polarity) is apparent. It is additionally necessary to determine the mechanisms associated with nanoparticle-induced cytotoxicity in order to better understand the problems posed to both human and environmental health and then develop new safer nanoparticles. Therefore, the focus of this study is to determine the nano-specific (physical) properties, including size and functionalization that cause toxicity, specifically through interaction with a cell membrane. A supported lipid bilayer (SLB) composed of L-α-phosphatidylcholine (egg PC) was used as a model cell membrane to test the effects of 2, 5, 10 and 40 nm gold nanoparticles (AuNPs). Given the imminent exposure of nanoparticles to the environment it is important to determine how nanoparticles would behave in the presence of natural organic matter or polymers which are naturally present in environmental systems. Poly(methacrylic acid) (PMA) can be used to represent the polymers normally found in the environment. AuNPs were diluted in PMA in order to simulate fundamental environmental conditions. Analysis was done using a quartz crystal microbalance with dissipation (QCM-D), which measures the frequency (f) and dissipation (D) changes directly associated with mass and conformation changes of the SLB. Different overtones for f and D allow for theoretical interpretation of changes correlated to different layers of the membrane. The 2 and 5 nm particles were found to interact strongly with the lipid bilayer by adsorbing to and/or partially/completely penetrating into the lipid bilayer presumably due to a hydrophobic coating caused by PMA adsorption to the NP surface. The penetration caused a much more rigid membrane due to higher lipid packing caused by nanoparticle addition. The 10 and 40 nm particles interaction with the bilayer were not affected by the presence of PMA. Both AuNP sizes removed mass from the membrane with losses similar in de-ionized water and PMA solution. Removal of membrane mass (lipids/hydration) caused a more flexible membrane. It was determine that sized is the limiting factor for nanoparticle solubilization into the membrane. It can be concluded from the results that size coupled with natural organic matter affects the cytotoxicity of the nanoparticles to the membrane. A study was done with 12 nm functionalized AuNPs in the presence of humic acid, a well-known and more complex and realistic model for natural organic matter. A PC lipid bilayer was used to simulate a model cell membrane and QCM-D techniques were utilized in the determination of toxicity and mechanistic interaction of nanoparticles with a lipid bilayer. Functionalized AuNPs were shown to decrease the rigidity of the lipid bilayer by increasing the dissipation and decreasing the mass associated with the adsorbed film (SLB). The presence of humic acid stabilized the nanoparticles and provided increased electrostatic repulsion which resulted in decreased mass losses from the membrane and much smaller decreases in membrane rigidity. It was concluded that presence of humic acid reduces the effects of functionalized nanoparticle interaction with a lipid bilayer. These results may mean that natural organic matter has the ability to reduce the cytotoxic effects of nanoparticles released into the environment. Overall, the QCM-D was found to provide valuable information regarding the possible toxic properties and mechanisms in which different gold nanoparticle interact with a supported lipid bilayer under environmental conditions. The information provided by the studies performed has shed much light on the interaction of gold nanoparticles with a supported lipid bilayer in the presence of model natural organic matter. The experiments done in this study are the first steps towards developing an assay with the ability to determine the toxic physical properties and mechanisms by which nanoparticles interact with lipid bilayers will greatly aid in development of non-toxic nano-materials. The technology and techniques used in this study will greatly improve the field by solidifying one technique to use in the quantitative approach studying nanoparticle/cell interactions. The use of AFM techniques in conjunction with the QCM-D would be highly beneficial by facilitating better understanding of the exact mechanisms by which nanoparticles induce cytotoxicity.