Swelling characteristics of a blend hydrogel made of poly(allylbiguanido-co-allylamine) and poly(vinyl alcohol)

Cryostructuring of Polymeric Systems: 67 Properties and Microstructure of Poly(Vinyl Alcohol) Cryogels Formed in the Presence of Phenol or Bis-Phenols Introduced into the Aqueous Polymeric Solutions Prior to Their Freeze-Thaw Processing

Poly(vinyl alcohol) (PVA) physical cryogels that contained the additives of o-, m-, and p-bis-phenols or phenol were prepared, and their physico-chemical characteristics and macroporous morphology and the solute release dynamics were evaluated. These phenolic additives caused changes in the viscosity of initial PVA solutions before their freeze-thaw processing and facilitated the growth in the rigidity of the resultant cryogels, while their heat endurance decreased. The magnitude of the effects depended on the interposition of phenolic hydroxyls in the molecules of the used additives and was stipulated by their H-bonding with PVA OH-groups. Subsequent rinsing of such "primary" cryogels with pure water led to the lowering of their rigidity. The average size of macropores inside these heterophase gels also depended on the additive type. It was found also that the release of phenolic substances from the additive-containing cryogels occurred via virtually a free diffusion mechanism; therefore, drug delivery systems such as PVA cryogels loaded with either pyrocatechol, resorcinol, hydroquinone, or phenol, upon the in vitro agar diffusion tests, exhibited antibacterial activity typical of these phenols. The promising biomedical potential of the studied nanocomposite gel materials is supposed.

Surface-modified poly(lactide-co-glycolide) nanospheres for targeted bone imaging with enhanced labeling and delivery of radioisotope

Surface-modified nanospheres can be utilized for targeting drugs and diagnostic agents to the bone and bone marrow while extending their circulation time in the blood stream. The surface modification of poly(lactide-co-glycolide) (PLGA) nanospheres by radioisotope carrying poly(ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) triblock copolymers (Poloxamer 407) has been assessed by in vitro characterization and in vivo biodistribution studies after intravenous administration of the nanospheres to the mouse. A hydroxyphenylpropionic acid, a ligand for (125)I and (131)I labeling, was conjugated to the hydroxyl group of the Poloxamer 407 by using dicyclohexyl carbodiimide. The ligand-conjugated Poloxamer 407 was adsorbed onto the surface of PLGA nanospheres. Surface coating was confirmed by measuring both size distribution and the surface charge of the nanospheres. Besides, (125)I-labeling efficiency, radiolabeling stability, whole body imaging, and biodistribution of the radioisotope-labeled nanospheres were examined. Ligand-labeled, surface-modified PLGA nanospheres were in 100-nm size ranges, which may be adequate for long-circulation and further bone imaging. (125)I-labeling efficiency was >90% and was more stable at human serum for 24 h. A noticeable decrease in liver or spleen uptake was obtained by the surface-modified nanospheres. (125)I-labeled nanospheres showed higher blood maintenance and bone uptake compared with stannous colloid with the same size distribution. Therefore, a fully biodegradable, radioisotope-carrying, surface-modified nanosphere system has been developed as a promising tool for targeting bone and bone marrows.

The pH stimulated reversible loading and release of a cationic dye in a layer-by-layer assembled DNA/PAH film

Through the layer-by-layer (LbL) deposition method, DNA was assembled into an ultrathin film with a cationic poly(allylamine hydrochloride) (PAH). The loading and release of a typical cationic dye, 5, 10, 15, 20-tetrakis(4-N-methylpyridyl)porphine-tetra-(p-toluenesulfonate) (TMPyP), in the DNA/PAH films were investigated. It has been found that the LbL-assembled DNA/PAH film was very stable in both acidic and alkaline solutions. Stimulated by the pH change of the dye solution, the dye can be easily loaded into or released from the DNA/PAH film. In an alkaline solution, the dye could be rapidly loaded into the DNA/PAH film at room temperature, while in an acidic solution, the dye could be rapidly released. The mechanism of such pH-stimulated loading and release in the DNA/PAH film was discussed. It was further observed that the loading and release of the dye in the DNA/PAH film was reversible upon pH change and the process could be repeated many times.