Surfaces microparticles

Consumer care Oral hygiene, shampoo, antibacterial surfaces Microparticles + +... 

Fig. 6. Concentration profiles through an idealized biporous adsorbent particle showing some of the possible regimes. (1) + (a) rapid mass transfer, equihbrium throughout particle (1) + (b) micropore diffusion control with no significant macropore or external resistance (1) + (c) controlling resistance at the surface of the microparticles (2) + (a) macropore diffusion control with some external resistance and no resistance within the microparticle (2) + (b) all three resistances (micropore, macropore, and film) significant (2) + (c) diffusional resistance within the macroparticle and resistance at the surface of the...

Technologies to purify cells from white cell concentrates are in the research stage. Principles used include antibodies covalently bound to a surface, antibody-coated microbeads in a column, magnetic microparticles that have been coated with antibodies, and hoUow fibers that have been coated with antibodies. 

In principle, there is no upper bound in measurements of particle velocity (or stress) using laser velocity interferometry. In practice, very high-pressure shock fronts can cause copious jetting of microparticles from the free surface (Asay et al., 1976), obscuring the surface from the laser beam. To alleviate this, optically transparent materials can be bonded to the specimen, and particle velocity measurements are then made at the specimen/window interface. This has the added advantage of simulating in situ particle velocity... 

As mentioned earlier, the contact-mechanics-based experimental studies of interfacial adhesion primarily include (1) direct measurements of surface and interfacial energies of polymers and self-assembled monolayers (2) quantitative studies on the role of interfacial coupling agents in the adhesion of elastomers (3) adhesion of microparticles on surfaces and (4) adhesion of viscoelastic polymer particles. In these studies, a variety of experimental tools have been employed by different researchers. Each one of these tools offers certain advantages over the others. These experimental studies are reviewed in Section 4. 

Chitosan microparticles were prepared with tripolyphosphate by ionic cross-hnking, starting from chitosan acetate 1% and oil as an emulsion in the presence of the surfactant Tween-80 2% the o/w 1 10 emulsion was introduced into tripolyphosphate solution by a spray gun. The microparticles were then washed their sizes were in the 500-710 jim range. As the pH of tripolyphosphate solution decreased and the molecular weight of chitosan increased, the microparticles had a more spherical shape and smoother surface [98]. 

A large variety of drug delivery systems are described in the literature, such as liposomes (Torchilin, 2006), micro and nanoparticles (Kumar, 2000), polymeric micelles (Torchilin, 2006), nanocrystals (Muller et al., 2011), among others. Microparticles are usually classified as microcapsules or microspheres (Figure 8). Microspheres are matrix spherical microparticles where the drug may be located on the surface or dissolved into the matrix. Microcapsules are characterized as spherical particles more than Ipm containing a core substance (aqueous or lipid), normally lipid, and are used to deliver poor soluble molecules... 

It is clearly visible from Figure 28.24 that initial moduli of nanocomposites are higher than those of microcomposites at any loading, given that the surface activity and surface area between nanoparticles and microparticles are different. 

Figure 7.3 shows the two-beam photon-force measurement system using a coaxial illumination photon force measurement system. Two microparticles dispersed in a liquid are optically trapped by two focused near-infrared beams ( 1 pm spot size) of a CW Nd YAG laser under an optical microscope (1064 nm, 1.2 MWcm , lOOX oil-immersion objective, NA = 1.4). The particles are positioned sufficiently far from the surface of a glass slide in order to neglect the interaction between the particles and the substrate. Green and red beams from a green LD laser (532 nm, 21 kWcm ) and a He-Ne laser (632.8 nm, 21 kW cm ) are introduced coaxially into the microscope and slightly focused onto each microparticle as an illumination light (the irradiated area was about 3 pm in diameter). The sizes of the illumination areas for the green and red beams are almost the same as the diameter of the microparticles (see Figure 7.4). The back scattered light from the surface of each microparticle is...

F Koosha, RH Muller, SS Davis, MC Davies. The surface chemical structure of poly (/J-hydroxybutyrate) microparticles produced by solvent evaporation process. J Control Rel 9 149, 1989. 

Morales, M.E., Ruiz, M.A., Oliva, I., Oliva, M. and Gallardo, V. (2007) Chemical characterization with XP S of the surface of polymer microparticles loaded with morphine. International Journal of Pharmaceutics, 333, 162—166. 

Recently, the LbL technique has been extended from conventional nonporous substrates to macroporous substrates, such as 3DOM materials [58,59], macroporous membranes [60-63], and porous calcium carbonate microparticles [64,65], to prepare porous PE-based materials. LbL-assembly of polyelectrolytes can also be performed on the surface of MS particles preloaded with enzymes [66,67] or small molecule drugs [68], and, under appropriate solution conditions, within the pores of MS particles to generate polymer-based nanoporous spheres following removal of the silica template [69]. 

The pore size and distribution in the porous particles play essential roles in NPS synthesis. For example, only hollow capsules are obtained when MS spheres with only small mesopores (<3 nm) are used as the templates [69]. This suggests that the PE has difficulty infiltrating mesopores in this size range, and is primarily restricted to the surface of the spheres. The density and homogeneity of the pores in the sacrificial particles is also important to prepare intact NPSs. In a separate study, employing CaC03 microparticles with radial channel-like pore structures (surface area 8.8 m2 g 1) as sacrificial templates resulted in PE microcapsules that collapse when dried, which is in stark contrast to the free-standing NPSs described above [64]. 

Jilek S, Ulrich M, Merkle HP et al (2004) Composition and surface charge of DNA-loaded microparticles determine maturation and cytokine secretion in human dendritic cells. Pharm Res 21 1240-1247... 

Caputo A, Spamacci K, Ensoli B et al (2008) Functional polymeric nano/microparticles for surface adsorption and delivery of protein and DNA vaccines. Curr Drug Deliv 5 230-242... 

SIAB and sulfo-SIAB have been used to make a high-capacity RNA affinity column for the purification of human IRP1 and IRP2 (Allerson et al., 2003), to couple antibodies or Fab fragments to amine-modified microparticles (Harma et al., 2000), and in the attachment of oligonucleotides to surfaces for detection arrays (Adessi et al., 2000). 

The reactions used for coupling affinity ligands to nanoparticles or microparticles basically are the same as those used for bioconjugation of molecules or for immobilization of ligands onto surfaces or chromatography supports. However, with particles, size can be a major factor in how a reaction is performed and in its resultant reaction kinetics. Since particle types can vary from the low nanometer diameter to the micron size, there are dramatic differences in how such particles behave in solution and how the density of reactive groups or functional groups affects reactions. 

---