Poly , platelet

Fig. 4.18 Formation ofhexagonal silica platelets with poly-L-lysine helical chains in the presence of monosilicic acid and phosphate. Reprinted with permission from [170], M.M.Tomczaketa/.J. Am. Chem. Soc. 2005, 727, 12577. 2005, American Chemical Society.

Many kinds of nonbiodegradable vinyl-type hydrophilic polymers were also used in combination with aliphatic polyesters to prepare amphiphilic block copolymers. Two typical examples of the vinyl-polymers used are poly(/V-isopropylacrylamide) (PNIPAAm) [149-152] and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) [153]. PNIPAAm is well known as a temperature-responsive polymer and has been used in biomedicine to provide smart materials. Temperature-responsive nanoparticles or polymer micelles could be prepared using PNIPAAm-6-PLA block copolymers [149-152]. PMPC is also a well-known biocompatible polymer that suppresses protein adsorption and platelet adhesion, and has been used as the hydrophilic outer shell of polymer micelles consisting of a block copolymer of PMPC -co-PLA [153]. Many other vinyl-type polymers used for PLA-based amphiphilic block copolymers were also introduced in a recent review [16]. 

In practice, some anticoagulation agents such as heparin or antiplatelet agents, e.g. nitric oxide (NO) are delivered to sensor sites in order to reduce the risk of thrombus formation. Nitric oxide (NO), which is a potent inhibitor of platelet adhesion and activation as well as a promoter of wound healing in tissue, has been incorporated in various polymer metrics including PVC (poly(vinyl-chloride)), PDMS (poly-dimethyl-siloxane) and PU (poly-urethanes). Those NO release polymers have been tested in animals as outer protection coatings and have shown promising effects for the analytical response characteristics of the sensor devices [137],... 

Large domains of oriented single crystals of poly(TCDU) and poly(DMDA) were produced on the alkali halide surface. Figures 1 and 2 show the typical elongated platelet morphology. Selected... 

Non-spherical micelles of poly(ethylene)(PE)-poly(ethylene-propylene)(PEP) in decane are self-assembhng in the form of extended platelets that have a crystalline PE-core and a planar PEP brush on both sides. Due to the large size of the platelets the centre of mass diffusion is extremely slow and allows a clear separation of the density fluctuation in the brush. NSE experiments [301] have been analysed in terms of the model of de Gennes [300]. The friction coefficient and modulus of the brush were found to be similar to those of a typical gel. 

Tumoko and coworkers [485] showed that polymers based on acrylamide, methyl propane sulfonic acid and butyl methacrylate in conjunction with poly(2 methacryloyloxyethyl phosphorylcholine-co-butyl methacrylate) are capable of suppressing platelet adherence. Similar results [486] were found on poly(gamma benzyl 1 glutamate-co-leucine) neutralized with sodium. 

In this connection, it is to be noted that polyamine-modified po y(HEMA) surfaces exhibit surprisingly reduced interaction with blood proteins and cells (e.g. erythrocyte, platelet, lymphocyte etc.), as will be discussed in Sects. 4.3 and 4.4. The present author considers that there are probably closely related mechanisms between the suppressing effect of the poly(DIPAM) or (Methacrol)-modi-fied SPU and that of the polyamine-modified poly(HEMA) surfaces, with regard to their mode of interaction with the biological elements. 

Okano et al. [84] measured changes in cytoplasmic Ca2+ concentrations in platelets adhering to HEMA-STY block copolymer (HSB) surfaces by means of fluorescence microscopy combined with a high performance image processor. Comparative studies were also carried out with the HEMA-STY random (HSR) copolymer of poly HEMA and polystyrene. Their results showed that cytoplasmic free calcium levels in platelets that were in contact with the HEMA-STY... 

A series of polymine-graft copolymers of styrene [92-95] and hydroxyethyl methacrylate [96-98] were found to form a microdomain structure and exhibit unique biomedical behavior at the interface with living cells, such as blood platelets and lymphocytes. The most intensive studies were made with poly(hydroxyethyl methacryIate)-0ra/t-polyamine copolymers (HA) ... 

Another study [114] on the role of protonated amine of HA copolymers in platelet retention showed that minimum retention was again observed on the surface of the copolymer containing N+ in 0.1 0.3 wt%. In other words, cell attachment scarcely takes place on the surface of HA2, in contrast to poly-HEMA, on the surface of which more than 90 percent cell attachment was observed. 

Fig. 9. Retention behavior of blood cells on poly(HEMA co[jV-methyl-/V-(4-vinylphenethyl) ethylenediamine (HAV) (pH 7.2, 23 °C flow rate, 0.4 ml/min flow time, 3,5 min). Open circles, lymphocytes closed squares, platelets open triangles, erythrocytes AVEMA, N-methyl- V-(4-vinyl-phenethyl)ethylenediamine [Ref. 115]...

X-ray diffraction techniques can be used to establish the structure of crystalline polymers. Measurements are typically made on crystalline lamellar platelets grown from dilute solution, fibres or stretched films. Such methods have been applied to several different inorganic polymers. For example, based on measurements on stretched samples of silicone rubber, poly(dimethylsiloxane) (Me2SiO) has been shown to possess a helical conformation (Figure 8.4). ... 

Park, Y. J., Ku, Y., Chung, . P., and Lee, S. J. (1998). Controlled release of platelet-derived growth factor from porous poly(L-lactide) membranes for guided tissue regeneration.. Control. Release 51, 201-211. 

For instance, the modification of silicone rubbers, poly-(tetrafluoroethylene), polyethylene, and segmented polyurethanes by ionic attachment of heparin was shown to result in a decrease of platelet adhesion onto these polymers71 74 75. A similar... 

Effects of Maillard Compounds on Platelet Aggregation Maillard reaction products of lysine-rich proteins prevent platelet aggregation, e.g., poly-L-lysine aggregates platelets, but upon Maillard reaction loses this ability (11). 

Park JH, Bae YH (2002) Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethylsiloxane) synthesis, characterization, in vitro protein adsorption and platelet adhesion. Biomaterials 23 1797-1808... 

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