Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2007. / Committee Chair: Degertekin, Levent; Committee Co-Chair: Whiteman, Wayne; Committee Member: Hesketh, Peter.

Thesis (Ph. D.)--Brigham Young University. Dept. of Physics and Astronomy, 2004. / Includes bibliographical references (p. 71-75).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 113-116). Also available in electronic version.

Atomic Force Microscopy (AFM) is a powerful technique that has evolved from being a purely imaging tool to a one capable of providing multifunctional information, offering exciting new possibilities for nano-biotechnology. The project focuses on the use of the AFM in order to morphologically and mechanically characterise cells and biomaterials demonstrating how versatile this instrument can be. The project is divided in the following parts:Part 1: establishment of AFM protocols for the nano-scale morphological and mechanical characterisation of soft and hard macroscopic substrates and of objects such as adsorbed nanoparticles. In particular, these techniques were tested on:Hyaluronic acid (HA)/poly(ethylene glycol) (PEG)-based hydrogels, which provide an artificial model for the mechanical behaviour of some biological tissues and organs. The elastic modulus, measured via AFM nanoindentation, of these hydrogels increased by decreasing the concentration and the molecular weight (MW) of HA in the hydrogels. We have then verified a clear relation between the mechanical properties of the hydrogels and the proliferation of cells cultured on them. Chitosan nanoparticle (popular carriers for the delivery of negatively charged macromolecular payloads, e.g. nucleic acids) cross-linked with triphosphate (TPP) and then coated with HA. We focussed on the influence of chitosan molecular weight (Mw) on nanoparticle properties. HA was able to penetrate into the more porous nanoparticles (high MW chitosan), whereas it formed a corona around the more cross-linked ones (low MW chitosan). AFM imaging was used to highlight the presence of this corona and also to estimate its apparent thickness to about 20-30 nm (in dry state).Silicone substrates modified with amphiphilic triblock copolymer (Sil-GMMA) layers. Extensive AFM (imaging and nanoindentation) provided evidence that silicone substrates are prevalently coated with Sil-GMMA thin layers that exhibit negligible hydrophobic recovery during drying and change the surface from more to less cell-adhesive. Part 2: AFM mechanical characterisation of fibroblast-to-myofibroblast differentiation process. Fibroblasts were stimulated to differentiate into myofibroblasts by Transforming Grow Factor β1 (TGFβ1) on hard substrate. AFM force maps performed both on fibroblasts (untreated cells) and myofibroblasts (TGFβ1-treated cells) revealed a significant increase in the elastic modulus in treated cells. Part 3: preparation and AFM characterisation of poly(ethylene glycol) diacrylate/acrylate (PEGDA/A) hydrogels. Since the mechanical properties of the substrate plays a pivotal role in fibroblast-to-myofibroblast differentiation process, hydrogels were prepared and characterised at the macro/nanoscale with AFM indentation, providing us with cell-adhesive substrates that cover a wide range of elastic modulus. These substrates are optimal candidates for future investigations to better understand and possibly control the differentiation process.

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Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Student: Veronika Ščuryová Supervisor: doc. RNDr. Pavel Doležal, CSc. Title of thesis: AFM in Pharmaceutical Technology 3 The theoretical part deals first with the construction of AFM microscope, the principle of the method, determining the surface topography and regimes which can be used. Described therein are distinct advantages over previous traditional methods but also its pitfalls. Next, I compare the results of measurements using AFM and declared size and devote also determine the shape of the particles. Experimental part is focused first on the detailed description of sample preparation for AFM measurement of nanoparticles. This procedure was followed by practical use to characterize the magnitude of the four types of commercially available nanoparticles Chromeonov (Sigma-Aldrich) using atomic force microscopy. The laboratory prepared Ag- nanoparticles could not be evaluated due to of technical and methodological reasons. The magnitude of the measured results nanoparticles were processed in histograms, which provide a description of the distribution of the measured values of the nanoparticle size. I found that compared to the size of the nanoparticles declared by the manufacturer are...

The theoretical part deals with topics related to the formation of nanofibers and nanomembranes by different ways of electrospinning. The literary search focused on "medicated nanofibrous membrane" gives recent information on nanomembranes containing drugs and also shows the perspective of the use of nanofibers in this area. The experimental part deals with AFM parameters needed for characterisation of the samples of six selected polymer nanomembranes with the content of naproxen, folic acid and diosmin. The appearance and thickness of the nanofibers was examined. The set up parameters of the AFM measurements allowed to observe the distribution of the drug in non- crystalline state within the nanofibers, regular fibrous shapes of crystal-like nanofibers as well as distinguished nanoingots of the polymers. The captured scans are stored and available for further analysis. Keywords: electrospinning, nanomembrane, naproxen, AFM, drug-loaded nanofibers

The necessity to explore nanoscopic systems is ever increasing in the world of science and technology. This evolving need to study such physically small systems demands new experimental techniques and methodologies. Atomic force microscopy (AFM) is a versatile technique that can overcome many nanoscopic size limitations. AFM has been utilized in the world of nanotechnology to study physiochemical properties of particles, materials, and biomolecules through characterization of morphology, electrical and mechanical properties, binding interactions, and surface tension, among others. The work discussed herein is largely a report of several novel AFM methodologies that were developed to allow new characterization techniques of individual submicrometer particles and single biomolecular interactions. The effects of atmospheric aerosols on the radiative budget of the earth and climate are largely unknown. For this reason, characterizing the physiochemical properties of aerosols is vital. Since the particles that have relatively long lifetimes in the atmosphere are smaller than one micrometer in size, high resolution microscopy techniques are required to study them. AFM is a suitable technique for single particle studies because it has nanometer spatial resolution, can perform experiments under ambient pressure and variable relative humidity and temperature. These advantages were utilized here and AFM was used to study morphology, organic volume fraction, water uptake, and surface tension of nascent sea spray aerosol (SSA) particles as well as laboratory generated aerosols composed of relevant chemical model systems. The morphology of SSA was found, often times, to be composed of core-shell structure. With complementary microscopy techniques, the composition of the core and the shell was found to be inorganic and organic in nature, respectively. Novel methodology to measure water uptake and surface tension of single substrate deposited particles with AFM was established using chemical model systems. Furthermore, these methodologies were employed on nascent chemically complex SSA particles collected from a biologically active oceanic waveflume experiment. Finally, phase imaging was used to measure organic volume fraction on a single particle basis and was correlated with biological activity. Overall, this suite of single (submicrometer) particle AFM analysis techniques have been established, allowing future systematic studies of increasing complexity aimed at bridging the gap between the simplicity of laboratory generated particles and the complexity of nature. Another nanotechnology topic of interest is studying single biomolecular interactions. Virtually every biological process involves some amount of minute forces that are required for the biomolecular system to function properly. For example, there are picoNewton forces associated with enzymatic motions that are important for enzyme catalysis. The AFM studies reported here use a model enzyme/drug system to measure the forces associated with single molecule adhesion events. Escherichia Dihydrofolate Reductase (DHFR) is a target of cancer therapeutic studies because it can be inhibited by drugs like methotrexate (MTX) that are structurally similar to the natural folate binder but have much higher binding affinity. One of the obstacles of single molecular recognition force spectroscopy (MRFS) studies is the contribution of non-specific forces that create a source of uncertainty. In this study, DHFR and MTX are bound to the surface and the AFM tip, respectively, using several different linking molecules. These linking molecules included polyethylene glycol (PEG) and double stranded DNA (dsDNA) and the distribution of forces was compared to scenarios were a linker was not employed. We discovered that dsDNA and PEG both allow identification and removal of non-specific interaction forces from specific forces of interest, which increases the accuracy of the measurement compared to directly bound constructs. Traditionally, the linker of choice in the MRFS community is PEG. Here, we introduce dsDNA as a viable linker that offers more rigidity than PEG, which may be desirable in future molecular constructs. The majority of the work and data presented in this dissertation supports the establishment of new AFM methodologies that can be used to better explore single biomolecular interactions and individual submicrometer particles on the nanoscale.