Agilent Measurement Journal - Issue 3 - 2007 - (Page 22)

13% 25% Figure 5 is a series of AFM images of a lactose crystal surface under increasing humidity, from 13 to 96 percent. The crystals are used as an inhaled drug carrier. Surface structures appear to “melt” at about 80 percent humidity. In situ AFM monitoring of the swelling effects of biological materials and polymer membranes in H2O can assist researchers in the recognition of hydrophilic surface locations. This type of observation can be performed at the single-macromolecule level. Figure 6 shows the swelling of a block copolymer based on n-butyl methacrylate (BMA) and poly (ethylene glycol) methyl ether methacrylate (PEGMA) using multifunctional macro initiator (Klok, H.-A., et al. 2006. Macromolecules, 39: 4507). Macromolecules of multi-arm star block copolymer extend their arms toward a mica substrate from the lipophilic molecular core. Upon humidity increase, the hydrophilic arms swell and the macromolecules adopt a spherical shape. Contrast of the phase images suggests the macromolecule core is harder than the core formed by the swelled hydrophilic arms. Such macromolecules are suggested as unimolecular drug containers. In situ AFM monitoring of uptake and release of drugs will be essential for proving this capability. 41% 66% 76% 81% 86% 96% Figure 5. MAC Mode AFM images of a lactose crystal surface under increasing humidity. Scan size = 5 µm x 5 µm. Sample courtesy of Drs. Gary Ward and Mike Maniaci of Dura Pharmaceuticals. (6a) (6b) (6c) 0 100 200 300 400 nm 0 100 200 300 400 500 nm 0 100 200 300 400 500 nm Figure 6. AFM images of BMA/PEGMA macromolecules of multi-arm star block copolymer. Scan size = 400 nm. (6a) Topography image of the single macromolecules on mica at 20 percent humidity; (6b and 6c) Topography and phase images of the macromolecules at 98 percent humidity. 22 Agilent Measurement Journal

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 3 - 2007

Applying Ingenuity to the Measurement of Emerging Technologies Contents Emerging Innovations Department Delivering Bigger Benefits by Optimizing Customer Workflows Measuring Material Properties at the Nanoscale Utilizing In Situ Atomic Force Microscopy in Life Science, Pharmaceutical and other Bio-Related Applications WiMAX™: Plotting a New Path to Global Mobility Addressing the Triple Complexity of Triple-Play Networks What Next for Mobile Telephony? Exploring the Inner Workings of Tire-Pressure Monitoring Systems Developing, Assessing and Applying a High-Resolution Thin-Film Magnetic Probe Making Accurate Settling-Time Measurements Using a Vector Network Analyzer Applying Metabolomics Methods to the Study of Bacterial Leaf Blight in Rice Plants Measuring Stream Dynamics with Fiber Optics survey

Agilent Measurement Journal - Issue 3 - 2007

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