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bOptimizing atomic force microscopy for characterization of diamond-protein interfaces.

Rezek B, Ukraintsev E, Kromka A - Nanoscale Res Lett (2011)

Bottom Line: We show that both diamond and proteins can be mechanically modified by Si AFM cantilever.We propose how to choose suitable cantilever type, optimize scanning parameters, recognize and minimize various artifacts, and obtain reliable AFM data both in solution and in air to reveal microscopic characteristics of protein-diamond interfaces.We also suggest that monocrystalline diamond is well defined substrate that can be applicable for fundamental studies of molecules on surfaces in general.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 16253 Prague 6, Czech Republic. ukraints@fzu.cz.

ABSTRACT
Atomic force microscopy (AFM) in contact mode and tapping mode is employed for high resolution studies of soft organic molecules (fetal bovine serum proteins) on hard inorganic diamond substrates in solution and air. Various effects in morphology and phase measurements related to the cantilever spring constant, amplitude of tip oscillations, surface approach, tip shape and condition are demonstrated and discussed based on the proposed schematic models. We show that both diamond and proteins can be mechanically modified by Si AFM cantilever. We propose how to choose suitable cantilever type, optimize scanning parameters, recognize and minimize various artifacts, and obtain reliable AFM data both in solution and in air to reveal microscopic characteristics of protein-diamond interfaces. We also suggest that monocrystalline diamond is well defined substrate that can be applicable for fundamental studies of molecules on surfaces in general.

No MeSH data available.


Related in: MedlinePlus

Influence of cantilever spring constant on FBS layer characterization. TM AFM images of fetal bovine serum (FBS) on H/O-terminated monocrystalline diamond (MCD) in solution using cantilevers with different spring constants: (a) by CSG01 cantilever, NT-MDT, k = 0.06 N/m. Central area was scanned in CM (nanoshaving) across H/O-terminated diamond, the position of the boundary was determined using topography data from a large area 135 × 135 μm2 scan, actual scan size is 10 × 10 μm2, A0 ~ 300 nm, energy of cantilever oscillations E ~ kA2/2 ~ 10-15 J; (b) on O-diamond by Multi75Al cantilever, Budget Sensors, k = 3 N/m, scan size 1 × 1 μm2, A0 ~ 50 nm, E ~ 10-14 J; (c) on O-diamond by NaDiaProbes, ADT, k = 120 N/m, scan size 15 × 15 μm2, A0 ~ 50 nm, E ~ 10-13 J, proteins were removed from the central area of 5 × 5 μm2 by CM scan prior to TM.
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Figure 1: Influence of cantilever spring constant on FBS layer characterization. TM AFM images of fetal bovine serum (FBS) on H/O-terminated monocrystalline diamond (MCD) in solution using cantilevers with different spring constants: (a) by CSG01 cantilever, NT-MDT, k = 0.06 N/m. Central area was scanned in CM (nanoshaving) across H/O-terminated diamond, the position of the boundary was determined using topography data from a large area 135 × 135 μm2 scan, actual scan size is 10 × 10 μm2, A0 ~ 300 nm, energy of cantilever oscillations E ~ kA2/2 ~ 10-15 J; (b) on O-diamond by Multi75Al cantilever, Budget Sensors, k = 3 N/m, scan size 1 × 1 μm2, A0 ~ 50 nm, E ~ 10-14 J; (c) on O-diamond by NaDiaProbes, ADT, k = 120 N/m, scan size 15 × 15 μm2, A0 ~ 50 nm, E ~ 10-13 J, proteins were removed from the central area of 5 × 5 μm2 by CM scan prior to TM.

Mentions: Figure 1 shows the results of AFM measurements of FBS on MCD in McCoy's solution using cantilevers with different spring constants, from very soft (k = 0.06 N/m) to very stiff (k = 120 N/m). At first, CM nanoshaving of FBS was performed in the central area of 2 × 2 μm2 on the border between H- and O-terminated surface regions. The position of the boundary was determined using topography data from 135 × 135 μm2 scan. The applied force ranged from 2.5 to 25 nN. The threshold force for protein removal from diamond surface was about 10 nN. This corresponds well to the threshold that has been reported in other experiments [8] and indicates non-covalent adsorption of proteins to the surface [4,28]. The image as shown in Figure 1a was then taken by TM using the low k cantilever at the second harmonic resonance frequency (k = 0.06 N/m, f2 ~ 30 kHz, A0 = 300 nm). Amplitude at the first resonance frequency in solution was extremely low (A0 < 1 nm) even with maximal driving voltage (10 V) and was not usable for measurements. H-terminated MCD surface, where FBS was removed, appears significantly higher (by 10 ± 3 nm) than the original FBS layer. Sometimes steps up to 200 nm in height were observed on H/O- boundary on MCD in solution using CSG01 cantilever at second harmonic resonance frequency. This is artificial as the real height difference between H/O surfaces is <1 nm as obtained using the medium frequency cantilevers both in CM and TM.


bOptimizing atomic force microscopy for characterization of diamond-protein interfaces.

Rezek B, Ukraintsev E, Kromka A - Nanoscale Res Lett (2011)

Influence of cantilever spring constant on FBS layer characterization. TM AFM images of fetal bovine serum (FBS) on H/O-terminated monocrystalline diamond (MCD) in solution using cantilevers with different spring constants: (a) by CSG01 cantilever, NT-MDT, k = 0.06 N/m. Central area was scanned in CM (nanoshaving) across H/O-terminated diamond, the position of the boundary was determined using topography data from a large area 135 × 135 μm2 scan, actual scan size is 10 × 10 μm2, A0 ~ 300 nm, energy of cantilever oscillations E ~ kA2/2 ~ 10-15 J; (b) on O-diamond by Multi75Al cantilever, Budget Sensors, k = 3 N/m, scan size 1 × 1 μm2, A0 ~ 50 nm, E ~ 10-14 J; (c) on O-diamond by NaDiaProbes, ADT, k = 120 N/m, scan size 15 × 15 μm2, A0 ~ 50 nm, E ~ 10-13 J, proteins were removed from the central area of 5 × 5 μm2 by CM scan prior to TM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211425&req=5

Figure 1: Influence of cantilever spring constant on FBS layer characterization. TM AFM images of fetal bovine serum (FBS) on H/O-terminated monocrystalline diamond (MCD) in solution using cantilevers with different spring constants: (a) by CSG01 cantilever, NT-MDT, k = 0.06 N/m. Central area was scanned in CM (nanoshaving) across H/O-terminated diamond, the position of the boundary was determined using topography data from a large area 135 × 135 μm2 scan, actual scan size is 10 × 10 μm2, A0 ~ 300 nm, energy of cantilever oscillations E ~ kA2/2 ~ 10-15 J; (b) on O-diamond by Multi75Al cantilever, Budget Sensors, k = 3 N/m, scan size 1 × 1 μm2, A0 ~ 50 nm, E ~ 10-14 J; (c) on O-diamond by NaDiaProbes, ADT, k = 120 N/m, scan size 15 × 15 μm2, A0 ~ 50 nm, E ~ 10-13 J, proteins were removed from the central area of 5 × 5 μm2 by CM scan prior to TM.
Mentions: Figure 1 shows the results of AFM measurements of FBS on MCD in McCoy's solution using cantilevers with different spring constants, from very soft (k = 0.06 N/m) to very stiff (k = 120 N/m). At first, CM nanoshaving of FBS was performed in the central area of 2 × 2 μm2 on the border between H- and O-terminated surface regions. The position of the boundary was determined using topography data from 135 × 135 μm2 scan. The applied force ranged from 2.5 to 25 nN. The threshold force for protein removal from diamond surface was about 10 nN. This corresponds well to the threshold that has been reported in other experiments [8] and indicates non-covalent adsorption of proteins to the surface [4,28]. The image as shown in Figure 1a was then taken by TM using the low k cantilever at the second harmonic resonance frequency (k = 0.06 N/m, f2 ~ 30 kHz, A0 = 300 nm). Amplitude at the first resonance frequency in solution was extremely low (A0 < 1 nm) even with maximal driving voltage (10 V) and was not usable for measurements. H-terminated MCD surface, where FBS was removed, appears significantly higher (by 10 ± 3 nm) than the original FBS layer. Sometimes steps up to 200 nm in height were observed on H/O- boundary on MCD in solution using CSG01 cantilever at second harmonic resonance frequency. This is artificial as the real height difference between H/O surfaces is <1 nm as obtained using the medium frequency cantilevers both in CM and TM.

Bottom Line: We show that both diamond and proteins can be mechanically modified by Si AFM cantilever.We propose how to choose suitable cantilever type, optimize scanning parameters, recognize and minimize various artifacts, and obtain reliable AFM data both in solution and in air to reveal microscopic characteristics of protein-diamond interfaces.We also suggest that monocrystalline diamond is well defined substrate that can be applicable for fundamental studies of molecules on surfaces in general.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 16253 Prague 6, Czech Republic. ukraints@fzu.cz.

ABSTRACT
Atomic force microscopy (AFM) in contact mode and tapping mode is employed for high resolution studies of soft organic molecules (fetal bovine serum proteins) on hard inorganic diamond substrates in solution and air. Various effects in morphology and phase measurements related to the cantilever spring constant, amplitude of tip oscillations, surface approach, tip shape and condition are demonstrated and discussed based on the proposed schematic models. We show that both diamond and proteins can be mechanically modified by Si AFM cantilever. We propose how to choose suitable cantilever type, optimize scanning parameters, recognize and minimize various artifacts, and obtain reliable AFM data both in solution and in air to reveal microscopic characteristics of protein-diamond interfaces. We also suggest that monocrystalline diamond is well defined substrate that can be applicable for fundamental studies of molecules on surfaces in general.

No MeSH data available.


Related in: MedlinePlus