nanoquebec 2006-11-16 04:09
纳米结构材料的表面物理和化学
[背景]了解纳米结构的表面物理化学性质对于纳米结构材料的认识和应用具有很重要的影响(据说生物材料的结构实际上是纳米结构体的表面物理化学在起关键的作用).有必要全面的了解纳米结构的表面物理化学.希望这一专题有助于认识纳米结构的物理化学性质
nanoquebec 2006-11-16 04:10
[b]An atomic force microscopy study of the effect of nanoscale contact geometry and surface chemistry on the adhesion of pharmaceutical particles.[/b]
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* Hooton JC, * German CS, * Allen S, * Davies MC, * Roberts CJ, * Tendler SJ,
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Pharm Res. 2004 Jun;21(6):953-61.
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Laboratory of Biophysics and Surface Analysis, School of Pharmacy, University of Nottingham, NG7 2RD, United Kingdom. I U)u t B Tv8I
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PURPOSE: To understand differences in particle adhesion observed with increasing humidity between samples of salbutamol sulfate prepared by two different methods. METHODS: Atomic force microscopy (AFM) force measurements were performed as a function of humidity (<10% to 65% RH) using two systems. The first system used clean AFM tips against compressed disks of micronized and solution enhanced dispersion by supercritical fluid (SEDS) salbutamol. The second system involved particles of both salbutamol samples mounted onto the apexes of AFM cantilevers, and force measurements being performed against a highly orientated pyrolytic graphite (HOPG) substrate. Following these measurements, the contact asperities of the tips were characterized. RESULTS: The first system showed a maximum in the observed adhesion at 22% relative humidity (RH) for the SEDS salbutamol compared to 44% RH for the micronized salbutamol. The second system showed a mix of peaks and continual increases in adhesion with humidity. The predicted Johnson-Kendall-Roberts forces were calculated and divided by the actual forces in order to produce a ratio. CONCLUSIONS: By relating the nature of the asperities to the force measurements, we propose a model in which adhesion scenarios range from single asperity nanometer-scale contact in which peaks in the adhesion were observed, to multiasperity contact where a continuous increase in adhesion was seen with humidity.
nanoquebec 2006-11-16 04:13
[b]Characterization of particle-interactions by atomic force microscopy: effect of contact area.[/b]
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Pharm Res. 2003 Mar;20(3):508-14d M4U)g ^
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* Hooton JC, * German CS, * Allen S, * Davies MC, * Roberts CJ, * Tendler SJ, * Williams P.3`;@}O ~Iq
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Laboratory of Biophysics and Surface Analysis, School of Pharmaceutical Sciences, University of Nottingham, NG7 2RD, United Kingdom. i;F-m I8F$c
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PURPOSE: The purpose of this work was to compare adhesion forces, contact area, and work of adhesion of salbutamol sulphate particles produced using micronization and a supercritical fluid technique (solution-enhanced dispersion by supercritical fluids--SEDS) using atomic force microscopy (AFM). METHODS: Adhesion forces of individual particles of micronized and SEDS salbutamol against a highly orientated pyrolytic graphite surface were acquired in a liquid environment consistent with that of a pressurized metered dose inhaler. The forces were then related to contact area and work of adhesion. RESULTS: The raw adhesion force data for the micronized and SEDS material were 14.1 nN (SD 2.5 nN) and 4.2 nN (SD 0.8 nN), respectively. After correction for contact area, the forces per unit area were 13 mN/microm2 (SD 2.3 mN/microm2) and 3 mN/microm2 (SD 0.6 mN/microm2). The average work of adhesion was calculated using the Johnson-Kendall-Roberts theory and was found to be 19 mJm(-2) (SD 3.4 mJm(-2)) for the micronized particle and 4 mJm(-2) (SD 0.8 mJm(-2)) for the SEDS particle. CONCLUSIONS: It is possible to produce a three-dimensional representation of the contact area involved in the interaction and make quantitative comparisons between different particles. There was a lower force per unit area and work of adhesion observed for the SEDS material, possibly because of its lower surface free energy.BI R6P{%| C!aL
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[b]nvestigation into the effect of humidity on drug-drug interactions using the atomic force microscope.[/b]-r6i1M(Im
J Pharm Sci. 2003 Apr;92(4):815-22.] eo ?#["S
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* Young PM, * Price R, * Tobyn MJ, * Buttrum M, * Dey F. M8M'Z4QO rR D2c
Pharmaceutical Technology Research Group, Department of Pharmacy and Pharmacology, University of Bath, BA2 7AY, UK. [email]prspmy@bath.ac.uk[/email]
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The atomic force microscope (AFM) has been used to characterize the cohesive nature of a micronized pharmaceutical powder used for inhalation therapy. Salbutamol sulfate (also referred to as albuterol sulfate), a therapeutic drug commonly delivered from dry powder inhalers (DPI), was chosen as a model system because the cohesion and subsequent de-agglomeration during inhalation are critical aspects to the efficacy of such a delivery system. Salbutamol sulfate drug particulates were mounted on V-shaped AFM cantilevers using a novel micromanipulation technique. Force-distance curves obtained from the measurements between cantilever drug probes and model compacts of salbutamol sulfate were integrated to determine separation energies. The effect of humidity (15-75% RH) on the energy required to separate a drug particle from model drug surface was determined using a custom-built perfusion apparatus attached to the AFM. Separation energy measurements over 10 x 10-microm areas of the compact surface (n = 4096) exhibited log normal distributions (apparent linear regression, R(2) >or= 0.97). Significant increases in the median separation energies (p < 0.05) between the salbutamol sulfate drug probes and salbutamol sulfate model surfaces were observed as humidity was increased. This result is most likely attributed to capillary interactions becoming more dominant at higher humidities. This investigation has shown the AFM to be a powerful technique for quantification of the separation energies between micronized drug particulates, highlighting the potential of the AFM as a rapid preformulation tool.