Hydrogels substrate effect

Such a substrate effect is observed in a wide variety of hydrogels prepared from water-soluble vinyl monomers (e.g., the sodium salt of styrene sulfonate, acrylic acid, and acrlyamide), and on various hydrophobic substrates, such as Teflon, polyethylene, polypropylene, PVC, and polymethyl methylacrylate (PMMA) [52]. This template effect is due to retardation of the radical polymerization near the rough and hydrophobic substrates that trap oxygen at the solid surface [82]. 

Kurokawa T, Gong JP, Osada Y (2002) Substrate effect on topographical, elastic, and frictional properties of hydrogels. Macromolecules 35 8161-9166... 

He, X., Ma, J., labbari, E. Effect of grafting RGD and BMP-2 protein-derived peptides to a hydrogel substrate on osteogenic differentiation of marrow stromal cells. Langmuir 24, 12508-12516 (2008)... 

J. P. (2008) Effect of substrate adhesion and hydrophobidty on hydrogel friction. Soft Matter, 4, 1033-1040. 

Another enzyme that was studied extensively in microreactors to determine kinetic parameters is the model enzyme alkaline phosphatase. Many reports have appeared that differ mainly on the types of enzyme immobilization, such as on glass [413], PDMS [393], beads [414] and in hydrogels [415]. Kerby et al. [414], for example, evaluated the difference between mass-transfer effects and reduced effidendes of the immobilized enzyme in a packed bead glass microreactor. In the absence of mass-transfer resistance, the Michaelis-Menten kinetic parameters were shown to be flow-independent and could be appropriately predicted using low substrate conversion data. 

The thin NIPAAm hydrogel layers were covalently attached to the surface, therefore the swelling was confined to one direction perpendicular to the substrate. The degree of anisotropy was calculated from ratio of l/0p and swelling ratio. This ratio was found to be between 1.2-1.3. Such a study describing the effect of hydrophilic comonomer on Tc of PNIPAAm provides an opportunity to formulate thermoresponsive hydrogel layers with desired transition temperature and swelling behavior for various applications. 

In this study, we report a very effective and widely applicable method for fabricating of nanostructures of an inert material for the biomolecular nanoarrays. The stable nanostructures of the PEG and PVA hydrogels were directly fabricated on gold substrates by UV-NIL (Fig. la). The site-selective nanoarray of various biomolecules such as protein and tethered lipid bilayer raft membrane (tLBRM) was constructed from a nanoimprinted inert materials by stepwise molecular self-assembly (Fig. lb and Ic). 

Several assumptions are made to mathematically model the immobilized adsorbent. The small adsorbent particles are assumed to be distributed uniformly inside the hydrogel bead. The external mass transfer resistance due to the boundary layer is assumed to be negligible if the bulk solution is well stirred. This assumption is supported by the experimental observations of Tanaka et al. who studied diffusion of several substrates from well stirred batch solutions into Ca-alginate gel beads (4), However, the boundary conditions can be easily modified to incorporate external diffusion effects if needed. Furthermore product diffusion in both the hydrogel and the porous adsorbent is considered to follow Fickian laws and its diffusivity in each region is assumed to be constant. 

Conditions of polymerization like temperature ( 7°C or 40°C what means below or above the phase transition temperature in pure water), nature of solvent (water or water/ethanol 50/50 mixture to use hydrophilic or more hydrophobic photo initiators), amount of cross-linker and monomer concentration can be varied to investigate the effect of reaction conditions on the swelling behaviour, phase transition temperature and morphology. Photo patterning of hydrogels can be done in the presence of an adhesion promoter on glass substrate (Singh et al. 2006). 

Blakney, A.K., Swartzlander, M.D., Bryant, S.J. The effects of substrate stiffness on the in vitro activation of macrophages and in vivo host response to poly(ethylene glycol)-based hydrogels. J. Biomed. Mater. Res. A 100, 1375-1386 (2012)... 

The use of PDMS was based on pressure-moulding technique of the spin-coated PEG hydrogel on asihcon substrate. The use of PDMS stamp was effective in producing PEG hydrogel micropattems of features lesser than 50-10 o,m. Photopolymerization through the PDMS stamp resulted in the fabrication of PEG hydrogel micropattems of sub-ceUular dimensions (10-40 om) and sharper resolutions. In addition,... 

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