Surface Modification of Nanoparticles

The cooperative effect of charges and hydrophobic functions on protein complexation was also investigated in another study using poly 9,9-bis[6 -(ArfiST,N-trimethylammonium)he g l](fluorophenylene) bromide /human serum albumin nanoparticles. In this case, the formation of assemblies with high affinity was the result of a combination of electrostatic interactions between the cationic side chains of the polymer and the negatively charged surface of the protein, in addition to the hydrophobic interactions between the polymer backbone and the hydrophobic patches of the protein. 

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The conjugation of vitamin B12 has been shown to increase oral bioavailability of peptides, proteins, and particles.44 46 62,63 Russsell-Jones and coworkers have attempted to exploit RME of vitamin B12 for the enhanced intestinal uptake of macromolecules such as luteinizing hormone—releasing factor (LHRH), granulocyte colony-stimulating factor, erythropoietin, and a-interferon.44,46,63 Also, they demonstrated that surface modification of nanoparticles with vitamin B12 can increase their intestinal uptake.44,62 The extended applications of this unique transport system, however, appear partially hampered by its limited uptake capacity. In human being, the uptake of vitamin B12 is only 1 nmol per intestinal passage. 

In numerous works dealing with the combination of nanoparticles and FR compounds, surface modifications of nanoparticles were only aimed to promote good dispersion of the nanoparticles into the polymer matrix (with intercalated or exfoliated morphologies for layered silicates as nanoparticles), even in the presence of the usual FRs, for example ammonium polyphosphate (APP) or magnesium hydroxide (MH). The initial aim was to combine the individual effects of each component to achieve strong synergistic effects. 

Moreover, the development of new strategies for surface modifications of nanoparticles with compounds having FR activity could provide a new field of research on FR systems. The use of novel phosphorus-, nitrogen-, or halogen-containing modifiers, instead of alkylammonium ions, for layered silicates seems promising. FR action conferred by the surface modifier can be combined with action due to composite morphology, particularly when the host polymer is a polymer blend instead of a pure polymer. 

Figure 13.15 Schematic representation of synthesis and surface modification of nanoparticles [54]. (Reproduced with permission from W.J. Rieter et al., Surface modification and functionalization of nanoscale metal-organic frameworks for controlled release and luminescence sensing, Journal of the American Chemical Society, 129, 9852-9853, 2007. 2007 American Chemical Society.)...

Tan, J.S. Butterfield, D.E. Voycheck, C.L. Caldwell, K.D. Li, J.T. Surface modification of nanoparticles by PEO/PPO block copolymers to minimize interactions with blood components and prolong blood circulation in rats. Biomaterials 1993,14, 823-833. 

Storm, G. Belliot, S.O. Daemen, T. Lasic, D.D. Surface modification of nanoparticles to oppose uptake by the mononuclear phagocyte system. Adv. Drug Deliv. Rev. 1995, 17, 31-48. 

Surface modification of nanoparticles in some cases allow the formation of stable dispersions in liquid hydrocarbons [57], If molybdenum sulphide nanoparticles are considered as friction-modifying additives for liquid lubricants, then a whole range of new possibilities appears. The action of tribologically active additives as nanoparticles has been proposed as in Fig. 8.6. 

Because the commercially available nanoparticles stick to each other and form large agglomerates, simple addition of these agglomerated nanoparticles into polymers would result in composites with properties even worse than the unfilled version. Therefore, surface modification of nanoparticles has to be made in advance to decrease par tides/par tides interaction and increase particles/polymer matrix interaction. 

The surface modification of nanoparticles to improve their targeting ability ... 

CrystallographicaUy speaking, particle surfaces consist of physical defects that can act as luminescence-quenching sites. Owing to the high specific surface area, nanoparticles tend to have much lower luminescence intensity than micron-sized particles. However, surface modification of nanoparticles can be used to enhance or tailor the luminescence properties of nanoparticles. ... 

Capitalizing on multicomponents, organic-inorganic hybrid nanocomposite materials have exhibited a synergistic effect due to properties generated by individual counterparts that may be useful for various technological applications. The surface modification of nanoparticles by functional monolayers of polymer sheUs provides a means of functionalization of nanocomposites and further tunable surface properties that may allow their covalent attachment, self-assembly, and organization on surfaces. 

For instance, maleic copolymers with different contents of galactose moieties and dodecyl chains were synthesized and used as both a stabilizer and a surface coating for the preparation of poly(s-caprolactone) nanoparticles by the emulsification-diffusion technique. The surface modification of nanoparticles was confirmed by -potential measurements. Nanoparticles were also shown to be recognized by a galactose-specific lectin, demonstrating the presence of galactose units on the particle surface [69]. 

In most cases, in situ suspension polymerization is carried out with nanoparticles dispersed in monomers. The surface modification of nanoparticles is usually required in order to achieve a good dispersion. Since the mechanism of in situ suspension polymerization is similar to that of in situ bulk polymerization, the surface modification used in bulk polymerization, including ion-exchange reaction, surfactant and coupling agent, polymer grafting and acid treatment can also be applied here. 

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