Temperature-sensitive polymers poly

Affinity chromatography of streptavidin was performed on a PET chip. The microchannel was first filled with the dual-modified latex beads (as shown in Figure 6.3). The biotinylated beads were surface-modified with a temperature-sensitive polymer, poly(N-isopropylacrylamide (PNIPAAm, 11 kDa). When the temperature was raised above the lower critical solution temperature (LCST) of PNIPAAm, the beads aggregated and adhered to the channel wall, because of a hydrophilic-to-hydrophobic phase transition. Then streptavidin from a sample solution was captured by these adhered biotinylated beads. Thereafter, when the temperature was reduced below the LCST, the beads dissociated and eluted from the channel wall together with the captured streptavidin [203],... 

Kang, S.l. and Bae, Y.H. (2001) pH/temperature-sensitive polymer poly(N-isopropylacrylamide-co-methacr-yloylated sulfamethoxypyridazine). Macromol. Chem. Symp., 14, 145-155. 

UGU Uguzdogan, E., Camh, T., Kabasakal, O.S., Patir, S., Ozturk, E., Denkbas, E.B., and Tuncel, A., A new temperature-sensitive polymer poly(ethoxypropylacrylamide),... 

Poly(A-isopropyl acrylamide) (PNIPAAm) is the most extensively studied temperature-sensitive polymer [10-20]. Crosslinked PNIPAAm exhibits drastic swelling transition at its lower critical solution temperature... 

Poly(N-isopropylacrylamide) (polyNIPAAM), formed by a free radical polymerization of N-isopropylacrylamide, is a water soluble, temperature sensitive polymer. In aqueous solution, it exhibits a lower critical solution temperature (LCST) in the range of 30-35 C depending on the concentration and the chain length of the polymer. Thus, as the solution temperature is raised above the LCST, the polymer undergoes a reversible phase transition characterized by the separation of a solid phase which redissolves when the solution temperature is lowered below the LCST. Its physicochemical properties have been investigated by several laboratories (1-3). 

Temperature-sensitive polymers are most likely the most investigated environmental stimuli-responsive materials (Qiu and Park 2001), especially for biomedical purposes. One of the well-known thermosensitive polymers is poly(N-isopropylacrylamide), abbreviated as poly(NIPAAm) (Fig. 11.1). This particular polymer has an LCST around 32°C. Below its LCST, NIPAAm is hydrophilic and soluble in aqueous solutions. As temperature is increased above 32°C, the polymer becomes hydrophobic and insoluble, resulting in its collapse into a gel. 

Poly(N-isopropyl acrylamide) (PNIPAAm) is one of the most widely studied temperature sensitive polymers that undergoes clear solution to precipitation. However, its nonbiodegradabihty and concern for residual monomer toxicity limit the biomedical applications. To improve the problems, biodegradable... 

Studies carried out by Yoshida and coworkers have coupled this phenomena with oscillating chemical reactions (such as the Belousov-Zhabotinsky, BZ, reaction) to create conditions where pseudo non-equilibrium systems which maintain rhythmical oscillations can demonstrated, in both quiescent (4) and continuously stirred reactors (5). The ruthenium complex of the BZ reaction was introduced as a functional group into poly(N-isopropyl acrylamide), which is a temperature-sensitive polymer. The ruthenium group plays it s part in the BZ reaction, and the oxidation state of the catalyst changes the collapse temperature of the gel. The result is, at intermediate temperature, a gel whose shape oscillated (by a factor of 2 in volume) in a BZ reaction, providing an elegant demonstration of oscillation in a polymer gel. This system, however, is limited by the concentration of the catalyst which has to remain relatively small, and hence the volume change is small. 

KOJ Kojima, C., Yoshimura, K., Harada, A., Sakaitishi, Y., and Kono, K., Temperature-sensitive hyperbranched poly(glycidol)s with oligo(ethylene glycol) monoethers, J. Polym. Sci. Part A Polym. Chem., 48, 4047, 2010. 

Temperature-sensitive polymers were synthesized based on poly(ethylene glycol) (PEG) and L-lysine ester diisocyanate (LDI) Showed about 25% encapsulation efficiency Release of drug was dependent on transition temperature ofLDI-PEG600 [33]... 

Thermoresponsive control over the display of RGD peptides has been demonstrated by Okano and co-workers (Ebara et al., 2004). A temperature-sensitive copolymer, poly(A-isopropylacrylamide-co-2-carboxyisopropylacrylamide), is grafted on a surface and then decorated with RGD by attachment of the peptide to the carboxylic acid functionalities of the polymer. Cell adhesion is promoted at temperatures above the LCST but reduced below the LCST. This is explained with a modulation of the availability of the peptide at the material surface above the LCST, the polymer is collapsed and the peptide is available at the surface, whereas below the LCST, the polymer becomes soluble and the expanding polymer chains prevent access to the peptide (Figure 3.7(c)). 

Lee J, Joo MR, Kim J, Park JS, Yoon M-Y, Jeong B (2009) Temperature-sensitive biodegradable poly(ethylene glycol). J Biomater Sci Polym Ed 20 957-965... 

Thennosensitive polymers have been developed extensively over the past years l-4. In particular, polymers showing a sol-gel transition by temperature change have been proposed for an injectable drug delivery depot [5,6]. As an example of temperature sensitive polymers, aqueous solutions of commercially available poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO Pluronics (BASF) or Poloxamers (ICI)) demonstrated sol-gel phase transitions with increasing temperature. 

---