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Mode Atomic Force Microscopy (mode + atomic_force_microscopy)
Selected AbstractsInfluence of hydroxyvalerate composition of polyhydroxy butyrate valerate (PHBV) copolymer on bone cell viability and in vitro degradationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Hui Liu Abstract The objective of this study was to elucidate the role of hydroxyvalerate (HV) composition in polyhydroxy butyrate valerate (PHBV) copolymer film on the degradation of copolymer and osteoblastic cell activity. Degradation was studied by monitoring time-dependent changes in mass and chemical composition of the macroporous films. The mass loss of PHBV film upon 19 weeks of exposure to pH 7.4 phosphate buffer medium was found to range from 2.8% to 9.2% with a strong dependence on the original composition of the copolyester film and morphology. Tapping mode atomic force microscopy (TMAFM) was used to examine the roughness change of polyester films due to exposure to buffer medium. Chemical analysis of the degraded film was carried out using NMR to aid in the interpretation of the mass loss and TMAFM data. The NMR results showed a significant decrease in the mol % of HV content in the degraded PHBV film. Additionally, we established that UMR-106 cell proliferation on macroporous PHBV matrix is minimally enhanced by the HV content of PHBV copolymer. Information provided by this study can be used in the selection of appropriate PHBV copolymer for clinical use where the biopolymer needs to remain physically intact and chemically unchanged during the intended period of biomedical application. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] A study of phase separation in peptide-loaded HPMC films using Tzero -modulated temperature DSC, atomic force microscopy, and scanning electron microscopyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2004Samana Hussain Abstract Despite the widespread use of drug-loaded polymeric systems, there is still considerable uncertainty with regard to the nature of the distribution of the drug within the polymer matrix. The aim of this investigation was to develop thermal and microscopic techniques whereby the miscibility and spatial distribution of a model peptide, cyclosporin A (CyA), in hydroxypropyl methylcellulose (HPMC) films may be studied. The new technique of Tzero -modulated temperature differential scanning calorimetry (Tzero MTDSC), scanning electron microscopy (SEM), and pulse force mode atomic force microscopy (PFM-AFM) were used in conjunction to study films prepared using a solvent evaporation process, with a solvent extraction study performed to elucidate the nature of the observed phases. Tzero MTDSC studies showed glass transitions for both the HPMC and CycA, with the Tg for the HPMC and CycA seen for the mixed systems. SEM showed two spherical phases of differing electron density. PFM-AFM also showed spheres of differing adhesion that increased in size on addition of drug. Pixel intensity analysis indicated that the smaller spheres corresponded to CycA. Exposure of the films to dichloromethane, in which CycA is soluble but HPMC is not, resulted in the presence of voids that corresponded well to the spheres suggested to correspond to the drug. It was concluded that the system had undergone extensive or complete phase separation, and that the thermal and microscopic techniques outlined above are an effective means by which this issue may be studied. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1672,1681, 2004 [source] Persistence Length of Cartilage Aggrecan Macromolecules Measured via Atomic Force MicroscopyMACROMOLECULAR SYMPOSIA, Issue 1 2004Laurel Ng Abstract Tapping mode atomic force microscopy (TMAFM) was employed to directly calculate the persistence length of individual fetal bovine epiphyseal and mature nasal cartilage aggrecan monomers, as well as their constituent chondroitin sulfate glycosaminoglycan chains. [source] Metastable and stable states of xanthan polyelectrolyte complexes studied by atomic force microscopyBIOPOLYMERS, Issue 3 2004Gjertrud Maurstad Abstract The compaction of the semiflexible polysaccharide xanthan with selected multi- and polyvalent cations was studied. Polyelectrolyte complexes prepared at concentrations of 1,2 ,g/ml were observed by tapping mode atomic force microscopy. High-molecular-weight xanthan compacted with chitosan yields a blend of mainly toroidal and metastable structures and a small fraction of rod-like species. Polyelectrolyte complexes of xanthan with polyethylenimine and trivalent chromium yielded similar structures or alternatively less well packed species. Racquet-type morphologies were identified as kinetically trapped states occurring on the folding path toward the energetically stable state of the toroids. Thermal annealing yielded a shift of the distribution of xanthan,chitosan morphologies toward this stable state. Ensembles of toroidal and rod-like morphologies of the xanthan,chitosan structures, collected using an asphericity index, were analyzed. The mean height of the toroids increased upon heating, with a selective increase in the height range above 2 nm. It is suggested that the observed metastable structures are formed from the high-molecular-weight fraction of xanthan and that these are driven toward the toroidal state, being a low-energy state, following annealing. Considered a model system for condensation of semiflexible polymers, the compaction of xanthan by chitosan captures the system at various stages in the folding toward a low-energy state and thus allows experimental analyses of these intermediates and their evolution. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source] Image Contrast Inversion of a Solvent Cast SEBS FilmCHINESE JOURNAL OF CHEMISTRY, Issue 1 2006Xia Han Abstract The image contrast inversion was investigated in detail when soft polymeric materials were imaged with tapping mode atomic force microscopy (TM-AFM). Solvent cast film of polystyrene- block -poly(ethylene/butylene)- block -polystyrene (SEBS) triblock copolymers was used as a model system in this study, which showed phase separation domains with a size of several tens of nanometers. AFM contrast reversal process, through positive image, to an intermediary and till negative image, could be clearly seen in height images of the soft block copolymer using different tapping force. The higher tapping force would lead to not only contrast inversion, but also the different size of the microdomains and different roughness of the images. Moreover, contrast inversion was explained on the basis of attractive and repulsive contributions to the tip-sample interaction and indentation of the soft domains. [source] | |||||||||||||