Patterned and switchable surfaces for biomaterial applications

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DNA (mg/m 2 )1/ DNA (m 2 /mg)1/ DNA (m 2 /mg)Chapter 3 – Comparison of the binding mode of plasmid DNA to allylamine plasma polymer and poly(ethyleneglycol) surfaces(A)32.5ALAPP21.510.5PEG00 200 400 600 800 1000[DNA] (ng/ml)(B)432ALAPP100 10000 20000 300001/[DNA] (ml/mg)(C)25201510PEG500 5000 10000 150001/[DNA] (ml/mg)Figure 3.4. (A) Binding isotherm for DNA adsorption to ALAPP ( ) and PEG ( )and (B) and (C) inverse of DNA surface concentration against the inverse ofthe DNA concentration determined on (B) an ALAPP film and (C) PEGgrafted onto ALAPP, in 0.01 M phosphate buffer, pH 7.4, [NaCl] 0.5 Mobtained from measurements of the depletion of solution fluorescence. Alinear correlation fit is shown; (B) R 2 = 0.954, (C) R 2 = 0.908.3-116
Andrew Hook – Patterned and switchable surfaces for biomaterial applicationsThe DNA on PEG was found to be significantly lower than for ALAPP over thebulk DNA concentration range studied (Figure 3.4A) confirming that, as expected,PEG resists adsorption of DNA as compared with the ALAPP film. By applying theLangmuir model to the data sets shown in Figure 3.4, the s and K for DNAadsorption to PEG were found to be 1.75 mg/m 2 and 680 ml/mg respectively, whichis significantly lower than the equivalent values of 4.96 mg/m 2 and 1600 ml/mgmeasured for ALAPP. The small amount of DNA adsorption observed on the PEGfilms is presumably due to weak Van der Waals interactions or hydrogen bonding.At pH 7.4 a more negative -potential was measured for ALAPP than for PEG. Assuch, electrostatic interactions with the ALAPP film should be less favourable thanfor the PEG film. Significantly, a contact angle difference of 57° was measured forthe two films, with the PEG film being more hydrophilic, an important disparitybetween these two films at a pH of 7.4. Thus, rather than the stabilisation of a DNAon an ALAPP film being predominantly due to electrostatic interactions,hydrophobic effects between the hydrophobic nucleobases and hydrophobicfunctionalities within the ALAPP film were suspected to contribute significantly [18,19]. It is suspected that the brush character of the PEG film, as discussed previously,also contributes to the low DNA seen on the PEG films.To further investigate how DNA interacts with ALAPP surfaces, a series ofexperiments monitoring DNA adsorption in various solvents of varying pH, ionconcentration and hydrophobicity were conducted. The results are shown in Figure3.5-Figure 3.8. Entropically, the adsorption of DNA is driven by surface dehydration,that is, the removal of water molecules from the surface [20]. However, in order forthis thermodynamically favourable process to occur, the DNA molecules mustdiffuse close enough to the surface to displace water molecules at the solid/liquid3-117
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Patterned andswitchable surfacesfor
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TABLE OF CONTENTSTABLE OF CONTENTS
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CHAPTER 1.INTRODUCTION1The content
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Chapter 1 - Introductionconsiderabl
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Chapter 1 - Introductioninteraction
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Chapter 1 - IntroductionIn general,
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Chapter 1 - IntroductionFor some ap
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Chapter 1 - Introductionangles rang
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Chapter 1 - Introductionof understa
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Chapter 1 - IntroductionSeveral str
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Chapter 1 - Introductioncues to con
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Chapter 1 - Introductionby controll
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Chapter 1 - Introduction1.2.2. Soft
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Chapter 1 - Introductionsubstrate.
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Chapter 1 - Introduction(A)(B)Figur
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Chapter 1 - Introduction(A)(B)(C)(C
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Chapter 1 - Introductioncomplex gen
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Chapter 1 - Introductionmorphology
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Chapter 1 - Introduction(A)(B)(C)(D
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Chapter 1 - Introductionthe LCST, a
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Chapter 1 - IntroductionHyun et al.
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Chapter 1 - Introductionmicelles. T
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Chapter 1 - Introduction1.4.1. DNA
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Chapter 1 - IntroductionA major pro
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Chapter 1 - Introductionattached to
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Chapter 1 - IntroductionTable 1.1.
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Chapter 1 - Introductionefficiencie
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Chapter 1 - Introductionachieved by
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Chapter 1 - IntroductionTable 1.2.
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Chapter 1 - IntroductionOnce releas
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Chapter 1 - Introductionimaging not
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Chapter 1 - IntroductionA number of
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CHAPTER 2.SPATIALLY CONTROLLED ELEC
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SPR signal intensity (counts)Andrew
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Reflectivity (%) Reflectivity (%)An
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Thickness (nm)Thickness (nm)Thickne
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CHAPTER 6.OVERALL CONCLUSIONS6.6An
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Force (nN)Force (nN)Force (nN)Force
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