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190 6. NANOSCALE ANALySIS Of PHARMACEUTICALS by SCANNINg PRObE MICROSCOPy individual lactose monohydrate crystal within a blend has been studied. The resultant indent due to local melting is apparent in the image (now with nanometre resolution due to the sharper probe). The corresponding cantilever deflection trace reveals the loss of water from the monohydrate and the melt of the anhydrous form at temperatures consistent with previous SThM and bulk analysis [59]. 6.5 CoNCluSIoNS As the barriers to developing new medicines become ever greater owing to new challenges in delivery, greater regulation and the scarcity of ‘easy’ molecules to develop into medicines, the role of probe microscopes in pharmaceuticals development is set to increase. The advantages of nanoscale resolution, minimal sample preparation and the non-invasive imaging capabilities of AFM in particular make this an ideal tool to bring new approaches to the investigation of drug material properties. This chapter has provided an insight into the improved understanding of pharmaceutical drug development available by AFM and thermal versions of AFM. These approaches have in a relatively short period of time provided a series of new insights into drug particle interactions and formulation structure. The capacity of AFM to not only image at the nanoscale but also to investigate interactions and to spatially map surface properties and to operate in a variety of environments consistent with pharmaceutical testing, manufacture and delivery provides great opportunity. ACkNowledgeMeNTS I would like to thank all who have contributed to this research, especially Martyn Davies, Jennifer Hooton, Ardeshir Danesh, Jin Zheng, Jeff James, Matthew Bunker, Michael Davies and Anne Turner. ABBrevIATIoNS ANd SyMBolS DPI dry powder inhaler Es elastic modulus of sample N m�2 K combined elastic modulus of tip and sample N m�2 L load force N
LTA local thermal analysis PTFE polytetrafluoroethylene R radius of probe m SThM scanning thermal microscopy T g glass transition temperature °C v s v t Poisson’s ratio for sample Poisson’s ratio of tip � indentation depth m references AbbREvIATIONS ANd SyMbOLS 191 [1] I. Verweire, E. Schacht, B.P. Qiang, K. Wang, I. De Scheerde, Evaluation of fluorinated polymers as coronary stent coating, J. Mater. Sci. Mater. Med. 11 (2000) 207–212. [2] A.L. Lewis, L.A. Tolhurst, P.W. Stratford, Phosphorylcholine-coated stent, J. Long Term Eff. Med. Implants 12 (2002) 231–250. [3] D. Traini, P. Yong, P. Rogueda, R. Price, The use of AFM and surface energy measurements to investigate drug-canister material interactions in a model pressurized metered dose inhaler formulation, Aerosol Sci. Technol. 40 (2006) 227–236. [4] A. Danesh, M.C. Davies, S. Hinder, C.J. Roberts, S.J.B. Tendler, P.M. Williams, M.J. Wilkins, Surface characterization of aspirin crystal planes by dynamic chemical force microscopy, Anal. Chem. 72 (2000) 3419–3422. [5] A. Danesh, S.D. Connell, M.C. Davies, S.J.B. Tendler, C.J. Roberts, P.M. Williams, M.J. Wilkins, An in situ dissolution study of aspirin crystal planes (100) and (001) by atomic force microscopy, Pharm. Res. 18 (2001) 299–303. [6] M. Davies, A. Brindley, X. Chen, M. Marlow, S.W. Doughty, I. Shrubb, C.J. Roberts, Characterization of drug particle surface energetics and Young’s modulus by atomic force microscopy and inverse gas chromatography, Pharm. Res. 22 (2005) 1158–1166. [7] R.I. Larsen, The adhesion and removal of particles attached to air filter surfaces, Am. Indust. Hyg. J. 19 (1958) 265–270. [8] F. Podczeck, The development of a cascade impactor simulator based on adhesion force measurements to aid the development of dry powder inhalations, Chem. Pharm. Bull. 45 (1997) 911–917. [9] B.C. Hancock, S.D. Clas, K. Christensen, Micro-scale measurement of the mechanical properties of compressed pharmaceutical powders. 1: The elasticity and fracture behavior of microcrystalline cellulose, I. J. Pharm. 209 (2000) 27–35. [10] S. Bin Baie, J.M. Newton, F. Podczeck, The characterization of the mechanical properties of pharmaceutical materials, Eur. J. Pharm. Biopharm. 42 (1996) 138–141. [11] G. Binning, C.F. Quate, Ch. Geber, Atomic force microscope, Phys. Rev. Lett. 56 (1986) 930–933. [12] N. Jalili, K. Laxminarayana, A review of atomic force microscopy imaging systems: application to molecular metrology and biological sciences, Mechatronics 14 (2004) 907–945. [13] N.H. Green, S. Allen, M.C. Davies, C.J. Roberts, S.J.B. Tendler, P.M. Williams, Force sensing and mapping by atomic force microscopy, Trends Analyt. Chem. 21 (2002) 64–73. [14] W.A. Ducker, T.J. Senden, R.M. Pashley, Direct measurement of colloidal forces using an atomic force microscope, Nature 353 (1991) 239–241.
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Butterworth-Heinemann is an imprint
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x Preface in their work. Hence, it
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xii Preface them from hostile condi
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xiv About thE Editors Professor Nid
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xvi List of Contributors Dr Daniel
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2 1. BAsIC PRINCIPLEs OF ATOMIC FOR
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32 2. MEASUREMENT OF PARTICLE ANd S
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82 3. QUANTIFICATION OF PARTICLE-BU
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100 3. QUANTIFICATION OF PARTICLE-B
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C H A P T E R 4 Investigating Membr
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4.2 THE RANgE OF POssIbILITIEs FOR
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4.2 THE RANgE OF POssIbILITIEs FOR
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4.3 CORREsPONdENCE bETwEEN sURFACE
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4.3 CORREsPONdENCE bETwEEN sURFACE
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4.4 IMAgINg IN LIqUId ANd THE dETER
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4.4 IMAgINg IN LIqUId ANd THE dETER
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4.5 EFFECTs OF sURFACE ROUgHNEss ON
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4.6 ‘vIsUALIsATION’ OF THE REjE
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4.7 THE UsE OF AFM IN MEMbRANE dEvE
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Dfractional 0.18 0.16 0.14 0.12 0.1
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4.8 CHARACTERIsATION OF METAL sURFA
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At pH 5.5, dissolution began to occ
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REFERENCEs 137 [4] W.R. Bowen, N. H
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240 8. ATOMIC FORCE MICROSCOPy ANd
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246 9. APPLICATION OF ATOMIC FORCE
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276 10. FuTuRE PRosPECTs most AFM s
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278 10. FuTuRE PRosPECTs targeted d
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A Actin stress fiber, 197 Adhesion,
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Natural organic matter, 140 Negativ
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