Surface Hydrophilicity Modifications

Several surface modification techniques have been developed to improve the wetting of PLA surfaces by introducing a variety of polar groups such as hydroxyl, carboxyl, amino and sulfate groups on polymer surfaces. 

Surface alkali hydrolysis treatment is also a convenient mediod to modify PLA poljmier siuTace [42 - 47]. In general, biodegradable aliphatic polyesters, such as PGA and PLA, contain ester bonds. The polymer film or scaffolds are immersed into aqueous NaOH solution. The ester bonds at the surface can be hydrolyzed and results in the generation of carboxylic acid and hydroxyl groups at the polymer surface. 

The hydrophilicity of the polymer is increased by introducing theses carboxyl and hydroxyl groups, which can theoretically lead to better cell adhesion during seeding. Such as, Nam et al. [42] reported that the surface modification of PLGA and poly (D,Z,-lactic acid) in the NaOH solution could moderate the surface of the polymers and promote the adhesion of hepatocytes. Gao et al. [44] stated that the surface hydrolysis of PGA meshes in the NaOH solution could increase the attachment ability of vascular smooth muscle cells. However, strong alkali treatment is accompanied with extended bulk degradation of the polyester, and 

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Yang, P. Deng, J. Y. Yang, W. T. (2003). Confined photo-catalytic oxidation a fast surface hydrophilic modification method for polymeric materials. Polymer, Vol. 44, pp. 7157-7164, ISSN 0032-3861. 

Xiang T, Yue WW, Wang R, Liang S, Sun SD, Zhao CS. Surface hydrophilic modification of polyethersulfone membranes by surface-initiated ATRP with enhanced blood compatibility. Colloids Surf B Biointerfaces 2013 110 15-21. 

In most of these applications, silica has the role of a support material. The popularity of silicon-based supports for multiple modification applications is well summarized by Mottola.1 Chemical modification requires seemingly paradoxal support properties (a) supports need to have a surface hydrophilic in nature but also to be insoluble in aqueous solutions and polar solvents (b) supports are required, in many instances, to be porous but retain mechanical stability and (c) they must be chemically stable but easily derivatized. Silica gel meets all of these requirements. 

Despite of hybridization with biological ligands, the general strategy for optimizing protein adsorption on biomaterial surfaces relies on chemical or physicochemical modulation of surface hydrophilicity [38,39]. The common approach is surface immobilization of hydrophilic polymers like polyethylene glycol [PEG] or polysaccharides. Four categories of surface-modification pathways have been developed ... 

The formation of self-assembled monolayers is a powerful tool for surface modification, and it is useful when we need to control surface hydrophilic-ity or prepare fimctional electrodes, for example. Surface modification with belts composed of monolayers of various hydrophihcities can yield surfaces with hydrophilicity gradients. liquid droplets can move across such surfaces against gravity due to favorable interactions with the monolayer surface (Fig. 4.38). 

Surface Modification is Applied to Make the Surface Hydrophilic... 

Figure 28.16 EIS Bode plots for Parylene C coated sample without pretreatment but with surface modification to make the surface hydrophilic.

Polyvinylidene-difluoride Low non-specific adsorption Dry autoclavable Good solvent compatibility Moderate flow rate and total throughput Hydrophobic base, made hydrophilic by chemical surface treatment may lose hydrophilic modification due to chemical attack High-cost filter material... 

Surface modification Makes hydrophobic surfaces hydrophilic. 

M.-L. Luo, J.-Q. Zhao, W. Tang, and C.-S. Pu. Hydrophilic modification of poly(ether sulfone) ultrafiltralion membrane surface by self-assembly of Ti02 nanoparticles. AppZ. Surf. ScL, 249(l-4) 76-84, August 2005. 

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