Micelles biocompatibility

To determine the photophysical and photochemical properties of unsubstituted phthalocyanines (MPc, M = Mg, Al, ZrL, SiClj, V=0, 2H) in their aggregates su-pramolecular systems have been developed on the basis of protein (albumin), micelles, biocompatible hydrophihc polymers, and nanoscale silica. The ability of MPc in supramolecular systems to form aggregates of different types depends on the nature of the central metal ion and microenvironment. The dependence of the type of MPc photoactivity method on aggregation was shown. H-aggregates exhibit selective photoactivity in electron transfer to Oj to form ROS (triplet-triplet energy transfer and fluorescence are impossible). Monomers and J-aggregates of MPc fluoresce and may also participate in the triplet-triplet energy transfer with the formation of O. Spectral properties of J-correspond to the requirements of the photosensitizer. 

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

Lomejad-Schafer, MR, Lambert, C, Breithaupt, DE, Biesalski, HK, and Frank, J, 2007. Solubility, uptake and biocompatibility of lutein and zeaxanthin delivered to cultured human retinal pigment epithelial cells in tween40 micelles. Eur JNutr 46, 79-86. 

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]. 

See also Luminescent dendrimers antibacterial, 26 799 biocompatibility studies of, 26 800-801 in catalysis, 26 805-806 in cell targeting, 26 797-798 as chelators, 26 806-807 core and interior shells of, 26 789 cytotoxicity of, 26 800-801 in drug delivery, 26 792-795 in gene transfection, 26 791-792 as imaging agents, 26 795-797 luminescent, 26 801-804 medical applications of, 26 791-801 micelle-mimetic behavior of, 26 789 multiphoton applications of, 26 803-804... 

Fan HY, Leve HY, Scullin C, Gabaldon J, TallantD, Bimge S, Boyle T, Wilson MC, Brinker CJ (2005) Surfactant-assisted synthesis of water-soluble and biocompatible semiconductor quantum dot micelles. Nano Lett 5 645-648... 

As with normal hydrocarbon-based surfactants, polymeric micelles have a core-shell structure in aqueous systems (Jones and Leroux, 1999). The shell is responsible for micelle stabilization and interactions with plasma proteins and cell membranes. It usually consists of chains of hydrophilic nonbiodegradable, biocompatible polymers such as PEO. The biodistribution of the carrier is mainly dictated by the nature of the hydrophilic shell (Yokoyama, 1998). PEO forms a dense brush around the micelle core preventing interaction between the micelle and proteins, for example, opsonins, which promote rapid circulatory clearance by the mononuclear phagocyte system (MPS) (Papisov, 1995). Other polymers such as pdty(sopropylacrylamide) (PNIPA) (Cammas etal., 1997 Chung etal., 1999) and poly(alkylacrylicacid) (Chen etal., 1995 Kwon and Kataoka, 1995 Kohorietal., 1998) can impart additional temperature or pH-sensitivity to the micelles, and may eventually be used to confer bioadhesive properties (Inoue et al., 1998). 

Soo, P. L., L. Luo, D. Maysinger, andA. Eisenberg. 2002. Incorporation and release of hydrophobic probes in biocompatible polycaprolactone-block-poly(ethylene oxide) micelles implications for drug delivery. Langmuir18 996-10004. 

As previously mentioned, degradable microspheres have gained attention as promising delivery vehicles for steroids in postmenopausal therapy. Copolymers of CL and d,l-LA were used to prepare microspheres for prolonged release of progesterone and [5-estradiol. The system offered a constant release for up to 40 days in vitro and 70 days in vivo [226]. Similarly, PCL copolymers have been considered useful for androgen replacement therapy in the treatment of aging men with a testosterone deficiency. Micelles of PCL-block-poly(ethylene oxide) released dihydrotestosterone in a controlled fashion over 30 days. The biocompatibility was confirmed in vitro in a HeLa cell culture [227]. 

Polymeric micelles are expected to self-assemble when block copolymers are used for their preparation [28]. Micelles of biocompatible copolymer, viz., PEO with PLA or with PBLA, have been reported in the literature [29,30]. The synthesis of such nanospheres with functional groups on their surface is shown in Fig. 2. 

In addition to their traditional applications as surfactants, dispersants, etc., amphiphilic polymers have recently been attracting active interest in terms of their behavior at liquid-liquid, solid-liquid, and other interfaces (micellization, segmental conformation, etc.), along with their biocompatibility. In this section, amphiphilic block copolymers alone are briefly discussed. Graft and multiarmed polymers with amphiphilic arms will be treated later in this chapter (Section VI). 

Hydrophobically modified polymers can associate in aqueous media to form micelle-like structures above their critical association concentrations (CACs). The nanosized self-aggregates were prepared using modified natural polysaccharides such as pullulan, curdlan, and glycol chitosan. The modified polysaccharides provide excellent biocompatibility, biodegradability, low immunogenicity, and biological activities. 

The choice of solubilization method will depend upon how efficiently the drug can be solubilized, stability in the system, and upon the biocompatibility of the vehicle for a given delivery route. For solid dosage forms, it may be possible to alter the solid phase to enhance dissolution. For parenterals, the four most commonly used techniques for solubilization are pH adjustment cosolvent addition micelle inclusion through surfactant addition and complexation. The following chapter is designed to summarize the theoretical as well as practical use of each of the above techniques. More extensive discussion on techniques for drug solubilization can be found in books dedicated to the subject. ... 

The effect of the lactose ligand was reconfirmed in the micelle system composed of the PEG-siRNA conjugate where the various functions developed so far were integrated [136]. As shown in Fig. 16a, the lactose was installed in the a end of the biocompatible PEG segment. An siRNA was directly conjugated via an acid labile /3-thiopropionate linkage at the co end of the a-lactosylated PEG, which was readily cleaved at the pFl corresponding to that of the intra-... 

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