Thermogelling polymers

Bromberg LE, Ron ES. Temperature-responsive gels and thermogelling polymer matrices for protein and peptide delivery. Advanced Drug Delivery Reviews. 1998 31(3) 197-221. 

Poly(N-(2-hydroxyproyl) methacrylamide (HPMAm)-oligolactate) (MW = 10-20 K Daltons) was linked to PEG (MW = 10 K Daltons) to show thermogelling polymer aqueous solution (Fig. 13.10). The gel modulus eould be controlled by the molecular weight of the poly(HPMAm-oligolactate) (Fig. 

In this chapter, biodegradable IP systems that can form hydrogels after injection into the body are introduced. Especially, recent progress in biodegradable copolymer systems exhibiting temperature-responsive sol-gel transition (thermogelling polymer) is mainly introduced from the viewpoint of polymer nanoarchitectonics. 

Table 4.1 Overview of the main thermosensitive thermogelling polymers described in Section 4.2.4. Reproduced from [113].

Ron, E.S. Smart gel a new thermogelling polymer mixture for drug delivery. Proceedings in international symposium of Controlled Rel Bioactive Materials. 23,23-24 (1996)... 

Changes in modulus of thermogelling polymer aqueous solutions can be determined by dynamic rheometry (Fig. 11). 

Reverse thermogelling polymers used to act as an effective injectable thermogel usually possess block architectures and a balanced structure of hydrophobicity and hydrophilicity. As temperature increases, the association of the polymers occurs due to increased hydrophobic interactions to show a temperature-sensitive sol-to-gel transition at a critical temperature, namely, lower critical solution temperature (LCST). Typical reverse thermogelling polymers include poly(N-substimted acrylamide)-based block copolymers [7-11], poly(vinyl ether)-based block copolymers, poly(ethylene oxide) (PEO)/poly(propylene oxide) (PPO)-based block copolymers [12-17] and PEG/polyester block copolymers [18-23], The representative structures of each class are shown in Fig. 1. In most cases, PEG was used as a hydrophilic block. All the themogelling hydrogels formed from the amphiphilic block copolymers mentioned above exhibit a sol-gel phase-transition in the physiological conditions in a tunable manner and have been intensively studied in recent years. 

Besides chitosan, naturally derived polymers such as hyaluronic acid can be chanically modified to form thermogels. For example, copolymers of NlPAAm and aCTylic add N-hydroxysuccinimide were first synthesized via free radical polymerization and then bonded to amine-functionalized hyaluronic acid (HA) to form a thermogelling polymer [53]. Other types of naturally derived polymers such as methyl cellulose have well-documented thermogelUng effect as well [54]. 

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