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Impact of surface electric properties of carbon-based thin films on platelets activation for nano-medical and nano-sensing applications.

Karagkiozaki V, Logothetidis S, Lousinian S, Giannoglou G - Int J Nanomedicine (2008)

Bottom Line: Platelet-rich plasma drawn from healthy donors was used and semi-contact mode of AFM was applied.Platelets behavior and their correlation with the electric surface properties of the examined a-C:H films by EFM was made for hemocompatibility enhancement and sensing platelets that are less electrical negatively charged and with higher tendency to aggregate and form thrombus.The results are discussed in view of the effect of different deposition conditions of hydrogenated carbon films on their structural and morphological characteristics, surface roughness and electrical properties attributing to different hemocompatibility and sensing aspects.

View Article: PubMed Central - PubMed

Affiliation: Physics Department, Laboratory for Thin Films-Nanosystems and Nanometrology (LTFN), Medical School, AHEPA University General Hospital, 1st Cardiology Department, Aristotle University of Thessaloniki, Greece.

ABSTRACT
Electric surface properties of biomaterials, playing key role to various biointerfacial interactions, were related to hemocompatibility and biosensing phenomena. In this study, the examination of surface electric properties of amorphous hydrogenated carbon thin films (a-C:H) was carried out by means of electrostatic force microscope (EFM) and observation of differences in spatial charge distribution on the surface of the examined films during platelets adhesion was made. The thrombogenic potential of a-C:H thin films developed by magnetron sputtering with approximately 42% sp(3) content and hydrogen partial pressure during deposition was evaluated, by in situ observation with atomic force microscope (AFM) of platelets' activation and their subsequent adhesion. Platelet-rich plasma drawn from healthy donors was used and semi-contact mode of AFM was applied. Platelets behavior and their correlation with the electric surface properties of the examined a-C:H films by EFM was made for hemocompatibility enhancement and sensing platelets that are less electrical negatively charged and with higher tendency to aggregate and form thrombus. The results are discussed in view of the effect of different deposition conditions of hydrogenated carbon films on their structural and morphological characteristics, surface roughness and electrical properties attributing to different hemocompatibility and sensing aspects.

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Electric force microscope image: platelets on a-C:H (Floating) after 1 hour incubation time (scan size 10 μm × 10 μm) (a) MAG*COS. The blue arrows indicate the platelets’ clusters whereas the green square denotes an area free of platelets (b) Phase.
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f6-ijn-3-461: Electric force microscope image: platelets on a-C:H (Floating) after 1 hour incubation time (scan size 10 μm × 10 μm) (a) MAG*COS. The blue arrows indicate the platelets’ clusters whereas the green square denotes an area free of platelets (b) Phase.

Mentions: As blood-clotting is a charge-transferring process, the thrombogenicity of the examined a-C:H thin films was estimated in regards of electrical surface distribution. Figure 6a illustrates the EFM image and especially the MAG*COS signal of platelets adhering onto floating a-C:H thin films. As the applied voltage (BV) between the probe and the sample was (+ )7.5V, when the positively charged tip meets the surface of the sample negative charges, attractive electrostatic forces between the tip and the sample were applied whereas when it meets positive charges, repulsive forces were assessed. By observing the EFM image in Figures 6a and 6b, it can be realized that MAG*COS and phase have negative values, implying that there are attractive forces between platelets and the positively charged tip leading to the conclusion that platelets are electrically negative. More precisely, by performing X-cross section at 4500 nm of the relevant AFM topography image (Figures 7a, 7b) at the lower boundaries of the central platelets’ cluster (black circle) it is obvious (as shown with the red arrow) that the red circle in Figure 7a is indicative of a platelet area with 250 nm height whereas the x-section of the same image (Figure 7c) at 7200 nm which indicates the upper boundaries of the same platelets’ cluster the red circle in Figure 7a shows an area with height of 370 nm. By comparing these two X-sections of the lower and upper boundaries of the central platelets’ cluster respectively, there is a difference in height of approximately 120 nm. By observing the EFM image in Figure 6a it can be seen that the lower boundaries of the examined platelets aggregation are blue implying that they are more electrically negative compared with the areas without platelets (as shown by green square). In contrast the upper boundaries of the same platelets aggregation are yellow and this finding shows that they are more electrically positive compared with the nearby areas free of platelets. It can be deduced that the platelets are electrical negative shown by the blue color of their lower boundaries of their central aggregation in the examined EFM image, whereas their upper boundaries are 120 nm higher compared with the lowest ones. This increase in height is rather too small to be indicative of platelet and may be due to the PRP proteins aggregations such as fibrinogen. It is known that under physiological conditions the overall charge of fibrinogen molecule is negative. However, its αC domains, which act as a pioneer in the surface binding process, are positively charged (Tebbe et al 2007).


Impact of surface electric properties of carbon-based thin films on platelets activation for nano-medical and nano-sensing applications.

Karagkiozaki V, Logothetidis S, Lousinian S, Giannoglou G - Int J Nanomedicine (2008)

Electric force microscope image: platelets on a-C:H (Floating) after 1 hour incubation time (scan size 10 μm × 10 μm) (a) MAG*COS. The blue arrows indicate the platelets’ clusters whereas the green square denotes an area free of platelets (b) Phase.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2636585&req=5

f6-ijn-3-461: Electric force microscope image: platelets on a-C:H (Floating) after 1 hour incubation time (scan size 10 μm × 10 μm) (a) MAG*COS. The blue arrows indicate the platelets’ clusters whereas the green square denotes an area free of platelets (b) Phase.
Mentions: As blood-clotting is a charge-transferring process, the thrombogenicity of the examined a-C:H thin films was estimated in regards of electrical surface distribution. Figure 6a illustrates the EFM image and especially the MAG*COS signal of platelets adhering onto floating a-C:H thin films. As the applied voltage (BV) between the probe and the sample was (+ )7.5V, when the positively charged tip meets the surface of the sample negative charges, attractive electrostatic forces between the tip and the sample were applied whereas when it meets positive charges, repulsive forces were assessed. By observing the EFM image in Figures 6a and 6b, it can be realized that MAG*COS and phase have negative values, implying that there are attractive forces between platelets and the positively charged tip leading to the conclusion that platelets are electrically negative. More precisely, by performing X-cross section at 4500 nm of the relevant AFM topography image (Figures 7a, 7b) at the lower boundaries of the central platelets’ cluster (black circle) it is obvious (as shown with the red arrow) that the red circle in Figure 7a is indicative of a platelet area with 250 nm height whereas the x-section of the same image (Figure 7c) at 7200 nm which indicates the upper boundaries of the same platelets’ cluster the red circle in Figure 7a shows an area with height of 370 nm. By comparing these two X-sections of the lower and upper boundaries of the central platelets’ cluster respectively, there is a difference in height of approximately 120 nm. By observing the EFM image in Figure 6a it can be seen that the lower boundaries of the examined platelets aggregation are blue implying that they are more electrically negative compared with the areas without platelets (as shown by green square). In contrast the upper boundaries of the same platelets aggregation are yellow and this finding shows that they are more electrically positive compared with the nearby areas free of platelets. It can be deduced that the platelets are electrical negative shown by the blue color of their lower boundaries of their central aggregation in the examined EFM image, whereas their upper boundaries are 120 nm higher compared with the lowest ones. This increase in height is rather too small to be indicative of platelet and may be due to the PRP proteins aggregations such as fibrinogen. It is known that under physiological conditions the overall charge of fibrinogen molecule is negative. However, its αC domains, which act as a pioneer in the surface binding process, are positively charged (Tebbe et al 2007).

Bottom Line: Platelet-rich plasma drawn from healthy donors was used and semi-contact mode of AFM was applied.Platelets behavior and their correlation with the electric surface properties of the examined a-C:H films by EFM was made for hemocompatibility enhancement and sensing platelets that are less electrical negatively charged and with higher tendency to aggregate and form thrombus.The results are discussed in view of the effect of different deposition conditions of hydrogenated carbon films on their structural and morphological characteristics, surface roughness and electrical properties attributing to different hemocompatibility and sensing aspects.

View Article: PubMed Central - PubMed

Affiliation: Physics Department, Laboratory for Thin Films-Nanosystems and Nanometrology (LTFN), Medical School, AHEPA University General Hospital, 1st Cardiology Department, Aristotle University of Thessaloniki, Greece.

ABSTRACT
Electric surface properties of biomaterials, playing key role to various biointerfacial interactions, were related to hemocompatibility and biosensing phenomena. In this study, the examination of surface electric properties of amorphous hydrogenated carbon thin films (a-C:H) was carried out by means of electrostatic force microscope (EFM) and observation of differences in spatial charge distribution on the surface of the examined films during platelets adhesion was made. The thrombogenic potential of a-C:H thin films developed by magnetron sputtering with approximately 42% sp(3) content and hydrogen partial pressure during deposition was evaluated, by in situ observation with atomic force microscope (AFM) of platelets' activation and their subsequent adhesion. Platelet-rich plasma drawn from healthy donors was used and semi-contact mode of AFM was applied. Platelets behavior and their correlation with the electric surface properties of the examined a-C:H films by EFM was made for hemocompatibility enhancement and sensing platelets that are less electrical negatively charged and with higher tendency to aggregate and form thrombus. The results are discussed in view of the effect of different deposition conditions of hydrogenated carbon films on their structural and morphological characteristics, surface roughness and electrical properties attributing to different hemocompatibility and sensing aspects.

Show MeSH
Related in: MedlinePlus