Drug delivery systems thermoresponsive polymer system

Development research on the DDS that uses phase transition of gels has been actively performed with thermoresponsive gels. Significant results have been reported for the development of base gel materials and the drug delivery system that use these gels. Although in vitro research is now underway, actual applications will become possible in the future. Polyacrylamide type polymers are thermoresponsive. As shown in Table 2, polymers that possess wide transition temperatures have been discovered. Under phase transition temperature the polymers will swell and above the transition they will shrink. 

Kavanagh, C. A., Rochev, Y. A., Gallagher, W. M., et al. (2004) Local drug delivery in restenosis injury thermoresponsive co-polymers as potenhal drug dehvery systems. Pharmacology Therapeutics, 102, 1-15. 

Kavanagha CA, Rochevb YA, Gallaghera WM, Dawsonc KA, Keenan AK. Local drug delivery in restenosis injury Thermoresponsive co-polymers as potential drug delivery systems. Pharmacol. Then 2004 102 1-15. 

Sakai, H., Okano, T., Yamada, N., Sakurai, Y. (1996). Thermoresponsive polymer surface for cell culture analysis of the surface and control of the cell attachment/detachment. In N. Ogata, S. Kim, J. Feijen, T. Okano (Eds.), Advanced biomaterials in biomedical engineering and drug delivery systems. Tokyo Springer. 

Dual-responsive polymer-based drug delivery vehicles offer even more versatility. Both temperature and enzyme-responsive micelles were formed from block polymers. While the thermoresponsive properties of the material allow it to be injected and subsequently form a reservoir in the body from where micelles enter the blood stream, the enzyme-responsive component allows triggered degradation of the micelles and release of the drug at the location of the diseased tissue (Garripelli et fl/.,2011). A doubly enzyme-responsive system can be obtained, for example, by designing polymer capsules with a shell that contains two layers. The two layers are degraded by different enzymes thus, proteins entrapped in the outer layer itself can be released upon exposure to the first enzyme, whereas the second enzyme destroys the capsule completely and liberates the proteins entrapped in the cavity of the vehicle (Itoh et al, 2008). 

Hollow silica gels were prepared using PNlPAAm by Liu et al. Rhodamine B was taken as the model drug, it was observed that the LCST of the PNlPAAm was increased to 40.6°C, which indicates a good performance of temperature-dependent phase transition. To further confirm the temperature responsiveness of the system, the release study was carried out at 25°C and 40°C. it was observed that 82.5% of the RHB was released for 12 h at 25°C while 86.5% was released at 40°C in 12 h. Thus, this indicates the prepared microgels achieve thermoresponsive controlled release behavior and were also found to be biocompatible [36]. Some of the applications of thermoresponsive polymers in drug delivery are summarised in Table 20.1. 

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