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Ferritin immobilization on patterned poly(2-hydroxyethyl methacrylate) brushes on silicon surfaces from colloid system.

Chen TY, Chen JK - Colloid Polym Sci (2011)

Bottom Line: The interaction between PHEMA and ferritin protein sheaths in MeOH and n-hexane (good and poor solvent for PHEMA, respectively) was used to capture and release ferritins from fluidic system.The "tentacles" behaver for PHEMA brushes was found through various solvents in fluidic system.Using high-resolution scanning electron microscopy, we observed patterned ferritin Fe cores on the Si surface after pyrolysis of the patterned PHEMA brushes and ferritin protein sheaths, which verify the "tentacles" behaver for PHEMA brushes.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Taiwan University of Science and Technology, 43, Sec 4, Keelung Rd, Taipei, 106 Taiwan Republic of China.

ABSTRACT
In this paper, we describe a graft polymerization/solvent immersion method for generating poly(2-hydroxyethyl methacrylate) (PHEMA) brushes in various patterns. We used a novel fabrication process, involving very-large-scale integration and oxygen plasma treatment, to generate well-defined patterns of polymerized PHEMA on patterned Si(100) surfaces. We observed brush- and mushroom-like regions for the PHEMA brushes, with various pattern resolutions, after immersing wafers presenting lines of these polymers in MeOH and n-hexane, respectively. The interaction between PHEMA and ferritin protein sheaths in MeOH and n-hexane (good and poor solvent for PHEMA, respectively) was used to capture and release ferritins from fluidic system. The "tentacles" behaver for PHEMA brushes was found through various solvents in fluidic system. Using high-resolution scanning electron microscopy, we observed patterned ferritin Fe cores on the Si surface after pyrolysis of the patterned PHEMA brushes and ferritin protein sheaths, which verify the "tentacles" behaver for PHEMA brushes.

No MeSH data available.


Related in: MedlinePlus

a SEM image of a trench, having a resolution of 750 nm, obtained through electron beam lithography. b–d AFM images of PHEMA brushes grafted from b, c 750-nm-resolution lines, obtained after polymerization for 24 h and immersion in bn-hexane and c MeOH and d 2-μm holes, after polymerization for 24 h and immersion in MeOH. e Relationship between the height of the patterned PHEMA brushes and the resolution of lines (filled triangles) and dots (empty squares) on the Si-BPOTS surfaces after MeOH immersion
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Fig6: a SEM image of a trench, having a resolution of 750 nm, obtained through electron beam lithography. b–d AFM images of PHEMA brushes grafted from b, c 750-nm-resolution lines, obtained after polymerization for 24 h and immersion in bn-hexane and c MeOH and d 2-μm holes, after polymerization for 24 h and immersion in MeOH. e Relationship between the height of the patterned PHEMA brushes and the resolution of lines (filled triangles) and dots (empty squares) on the Si-BPOTS surfaces after MeOH immersion

Mentions: The final step in our strategy was the surface-initiated polymerization of HEMA onto the functionalized areas of a patterned SAM. The presence of reactive OH groups after OPT allowed their direct use in the polymerization step. We used lithography processes with positive photoresists to fabricate trenches and holes having resolutions ranging from 200 nm to 10 μm. Figure 6a displays an SEM image of a trench, patterned using e-beam lithography, having a resolution of 750 nm on the Si wafer. The PHEMA brushes were grafted onto the 750-nm-resolution trenches through ATRP for 24 h. We used AFM to visualize the topographies of the resulting PHEMA brushes after their subsequent immersion in n-hexane and MeOH. We grafted PHEMA brushes from the Si-BPOTS surfaces of the trenches and holes to form lines of PHEMA brushes. Figures 6b, c reveals that the HEMA polymer chains grafted for 24 h on the Si surface existed as distinctive overlayers after immersion in n-hexane and MeOH, respectively. The patterned lines of the PHEMA brushes grafted for 24 h onto the 750-nm-resolution trenches were then immersed in solvent. Because of the presence of the mushroom- and brush-like regimes, the widths of the lines functionalized with PHEMA brushes had different resolutions after they had been immersed in n-hexane and MeOH. Using this strategy, the limit of resolution of the PHEMA brushes patterned in lines approached 750 nm. We observed imperfect line patterns for the PHEMA brushes when the trenches had dimensions of less than 750 nm prior to graft polymerization. The AFM images in Fig. 6b, c confirm the chemical amplification of the patterned OH-functionalized SAM, forming spatially localized polymer brushes after immersion in n-hexane and MeOH, respectively. The line pattern of the PHEMA brushes after immersion in MeOH displayed a more irregular overlayer on the surface because of the brush-like structure of the PHEMA units. After immersion in n-hexane, a regular line pattern formed because of inter-polymer hydrogen bonding within the mushroom-like PHEMA structures. The surface possessed its mushroom-like structure because of isotropic or nematic collapse of the PHEMA brushes in the presence of the poor solvent [39]. The line patterns of these PHEMA structures had different heights after treatment in MeOH and n-hexane because of the presence of the brush- and mushroom-like regimes, respectively. Again, these results confirm that the thickness of the polymer brushes changed after immersion in the good and poor solvents; furthermore, the grafting density and surface coverage varied accordingly, suggesting that they are suitable alternative parameters for calculating the thickness. Figure 6d reveals that the dot pattern of PHEMA brushes grafted for 24 h on the Si surface existed as a distinctive overlayer after immersion in MeOH. The patterned dots of PHEMA brushes were grafted for 24 h from holes having a resolution of 2 μm, and then the samples were immersed in solvent. Using this strategy, the limit of resolution of the patterned PHEMA brushes approached 750 nm for dot patterns. We observed imperfect line patterns for the PHEMA brushes when the holes had dimensions of less than 2 μm prior to graft polymerization. Our observations suggest that the trenches were a richer grafting site than the dots for the BPOTS treatment and OPT. Figure 6e presents the heights of the grafted PHEMA brushes, plotted with respect to the resolutions of the lines and dots onto the Si-BPOTS surfaces, after MeOH immersion. We observe approximately linear increases in the heights of the grafted PHEMA layer on the Si-BPOTS surface within the trenches upon increasing the resolution. The heights reached a plateau, indicating saturation of the grafting sites for ATPR, when the resolution was greater than 4 μm. In contrast, the height of the PHEMA brushes grafted from the holes increased upon increasing the resolution. The dot-patterned PHEMA brushes provided a more irregular overlayer on the surface because of the presence of unsaturated grafting sites on the Si-BPOTS surface. The considerable inaccuracy from measurement in Fig. 6e resulted from the ill-defined edges of the PHEMA brushes. SEM imaging revealed (Fig. 7a) the mushroom-like structure of this PHEMA thin film, where the formation of islands having radii of approximately 100 nm presumably resulted from the mushroom-like regime of the PHEMA brushes after they had been grafted for 24 h under vacuum in the SEM chamber. Figure 7b presents SEM images of the patterned lines of PHEMA brushes grafted for 24 h from trenches having a resolution of 2 μm. The PHEMA brushes possessed collapsed structures in the vacuum of the SEM chamber; the mushroom-like structures on the surfaces of the patterned PHEMA brushes led to expansion of the PHEMA brush resolution to greater than 2 μm. The mushroom-like structures that formed on the PHEMA brush layers had radii ranging from 100 to 300 nm, due to entanglement of the polymer chains under vacuum. This observation suggests that the PHEMA brushes possessed different structures when observed under atmospheric pressure (AFM) or vacuum (SEM).Fig. 6


Ferritin immobilization on patterned poly(2-hydroxyethyl methacrylate) brushes on silicon surfaces from colloid system.

Chen TY, Chen JK - Colloid Polym Sci (2011)

a SEM image of a trench, having a resolution of 750 nm, obtained through electron beam lithography. b–d AFM images of PHEMA brushes grafted from b, c 750-nm-resolution lines, obtained after polymerization for 24 h and immersion in bn-hexane and c MeOH and d 2-μm holes, after polymerization for 24 h and immersion in MeOH. e Relationship between the height of the patterned PHEMA brushes and the resolution of lines (filled triangles) and dots (empty squares) on the Si-BPOTS surfaces after MeOH immersion
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Related In: Results  -  Collection

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Fig6: a SEM image of a trench, having a resolution of 750 nm, obtained through electron beam lithography. b–d AFM images of PHEMA brushes grafted from b, c 750-nm-resolution lines, obtained after polymerization for 24 h and immersion in bn-hexane and c MeOH and d 2-μm holes, after polymerization for 24 h and immersion in MeOH. e Relationship between the height of the patterned PHEMA brushes and the resolution of lines (filled triangles) and dots (empty squares) on the Si-BPOTS surfaces after MeOH immersion
Mentions: The final step in our strategy was the surface-initiated polymerization of HEMA onto the functionalized areas of a patterned SAM. The presence of reactive OH groups after OPT allowed their direct use in the polymerization step. We used lithography processes with positive photoresists to fabricate trenches and holes having resolutions ranging from 200 nm to 10 μm. Figure 6a displays an SEM image of a trench, patterned using e-beam lithography, having a resolution of 750 nm on the Si wafer. The PHEMA brushes were grafted onto the 750-nm-resolution trenches through ATRP for 24 h. We used AFM to visualize the topographies of the resulting PHEMA brushes after their subsequent immersion in n-hexane and MeOH. We grafted PHEMA brushes from the Si-BPOTS surfaces of the trenches and holes to form lines of PHEMA brushes. Figures 6b, c reveals that the HEMA polymer chains grafted for 24 h on the Si surface existed as distinctive overlayers after immersion in n-hexane and MeOH, respectively. The patterned lines of the PHEMA brushes grafted for 24 h onto the 750-nm-resolution trenches were then immersed in solvent. Because of the presence of the mushroom- and brush-like regimes, the widths of the lines functionalized with PHEMA brushes had different resolutions after they had been immersed in n-hexane and MeOH. Using this strategy, the limit of resolution of the PHEMA brushes patterned in lines approached 750 nm. We observed imperfect line patterns for the PHEMA brushes when the trenches had dimensions of less than 750 nm prior to graft polymerization. The AFM images in Fig. 6b, c confirm the chemical amplification of the patterned OH-functionalized SAM, forming spatially localized polymer brushes after immersion in n-hexane and MeOH, respectively. The line pattern of the PHEMA brushes after immersion in MeOH displayed a more irregular overlayer on the surface because of the brush-like structure of the PHEMA units. After immersion in n-hexane, a regular line pattern formed because of inter-polymer hydrogen bonding within the mushroom-like PHEMA structures. The surface possessed its mushroom-like structure because of isotropic or nematic collapse of the PHEMA brushes in the presence of the poor solvent [39]. The line patterns of these PHEMA structures had different heights after treatment in MeOH and n-hexane because of the presence of the brush- and mushroom-like regimes, respectively. Again, these results confirm that the thickness of the polymer brushes changed after immersion in the good and poor solvents; furthermore, the grafting density and surface coverage varied accordingly, suggesting that they are suitable alternative parameters for calculating the thickness. Figure 6d reveals that the dot pattern of PHEMA brushes grafted for 24 h on the Si surface existed as a distinctive overlayer after immersion in MeOH. The patterned dots of PHEMA brushes were grafted for 24 h from holes having a resolution of 2 μm, and then the samples were immersed in solvent. Using this strategy, the limit of resolution of the patterned PHEMA brushes approached 750 nm for dot patterns. We observed imperfect line patterns for the PHEMA brushes when the holes had dimensions of less than 2 μm prior to graft polymerization. Our observations suggest that the trenches were a richer grafting site than the dots for the BPOTS treatment and OPT. Figure 6e presents the heights of the grafted PHEMA brushes, plotted with respect to the resolutions of the lines and dots onto the Si-BPOTS surfaces, after MeOH immersion. We observe approximately linear increases in the heights of the grafted PHEMA layer on the Si-BPOTS surface within the trenches upon increasing the resolution. The heights reached a plateau, indicating saturation of the grafting sites for ATPR, when the resolution was greater than 4 μm. In contrast, the height of the PHEMA brushes grafted from the holes increased upon increasing the resolution. The dot-patterned PHEMA brushes provided a more irregular overlayer on the surface because of the presence of unsaturated grafting sites on the Si-BPOTS surface. The considerable inaccuracy from measurement in Fig. 6e resulted from the ill-defined edges of the PHEMA brushes. SEM imaging revealed (Fig. 7a) the mushroom-like structure of this PHEMA thin film, where the formation of islands having radii of approximately 100 nm presumably resulted from the mushroom-like regime of the PHEMA brushes after they had been grafted for 24 h under vacuum in the SEM chamber. Figure 7b presents SEM images of the patterned lines of PHEMA brushes grafted for 24 h from trenches having a resolution of 2 μm. The PHEMA brushes possessed collapsed structures in the vacuum of the SEM chamber; the mushroom-like structures on the surfaces of the patterned PHEMA brushes led to expansion of the PHEMA brush resolution to greater than 2 μm. The mushroom-like structures that formed on the PHEMA brush layers had radii ranging from 100 to 300 nm, due to entanglement of the polymer chains under vacuum. This observation suggests that the PHEMA brushes possessed different structures when observed under atmospheric pressure (AFM) or vacuum (SEM).Fig. 6

Bottom Line: The interaction between PHEMA and ferritin protein sheaths in MeOH and n-hexane (good and poor solvent for PHEMA, respectively) was used to capture and release ferritins from fluidic system.The "tentacles" behaver for PHEMA brushes was found through various solvents in fluidic system.Using high-resolution scanning electron microscopy, we observed patterned ferritin Fe cores on the Si surface after pyrolysis of the patterned PHEMA brushes and ferritin protein sheaths, which verify the "tentacles" behaver for PHEMA brushes.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Taiwan University of Science and Technology, 43, Sec 4, Keelung Rd, Taipei, 106 Taiwan Republic of China.

ABSTRACT
In this paper, we describe a graft polymerization/solvent immersion method for generating poly(2-hydroxyethyl methacrylate) (PHEMA) brushes in various patterns. We used a novel fabrication process, involving very-large-scale integration and oxygen plasma treatment, to generate well-defined patterns of polymerized PHEMA on patterned Si(100) surfaces. We observed brush- and mushroom-like regions for the PHEMA brushes, with various pattern resolutions, after immersing wafers presenting lines of these polymers in MeOH and n-hexane, respectively. The interaction between PHEMA and ferritin protein sheaths in MeOH and n-hexane (good and poor solvent for PHEMA, respectively) was used to capture and release ferritins from fluidic system. The "tentacles" behaver for PHEMA brushes was found through various solvents in fluidic system. Using high-resolution scanning electron microscopy, we observed patterned ferritin Fe cores on the Si surface after pyrolysis of the patterned PHEMA brushes and ferritin protein sheaths, which verify the "tentacles" behaver for PHEMA brushes.

No MeSH data available.


Related in: MedlinePlus