Injectable chitosan thermogels for sustained and localized delivery of pingyangmycin in vascular malformations

Preparation and evaluation of chitosan-based nanogels/gels for oral delivery of myricetin

“…At approximately 35°C, an abrupt increase in viscosity (transition temperature) was observed, which indicated that the CS/β-GP nanogels possessed a temperature-dependent sol-to-gel transition property. It is worthwhile to note that the transition temperature obtained in the present study was a little lower than the reported temperature of 37°C or 36°C in other studies (Chen et al, 2014;Li et al, 2013). Due to the possible influence of the gelation temperature by the concentration of β-GP and the molecular weight and the degree of deacetylation of CS (Cheng et al, 2010;Chenite et al, 2000), it is reasonable that the rheological properties of CS/β-GP nanogels would be slightly varied.…”

“…and G" is often taken as a sign of gelation, and the crossover-time (approximately 40 s) is defined as the gelation time (Chen et al, 2014;Chenite, 2001;Hsiao et al, 2012). This time is further verified because the mixed CS/β-GP solution could speedily form a gel in 1 min when heated to 35°C (data not shown).…”

“…Obviously, gelation of the CS/β-GP nanogel system occurred with increasing temperature. In general, the sol-gel transition process of this system can be likely attributed to the following multiple interactions among chitosan, β-GP, and water: (a) the increase of chitosan interchain hydrogen bonding as a consequence of the reduction of electrostatic repulsion due to the basic action of β-GP, (b) the chitosan-glycerolphosphate electrostatic attractions via the ammonium and the phosphate groups, and (c) the CS-CS hydrophobic interactions enhanced by the structuring action of glycerol on water (Chenite et al, 2000;Chen et al, 2014;Zhou et al, 2015). As we all know, CS is almost insoluble in neutral or basic aqueous solution (pH > 7.0), but the addition of β-GP maintains CS solubility at a much higher pH (~7.2), and CS retains its positive charge to separate CS chains in solution at low temperatures (Chenite et al, 2000).…”

“…5), implying that both pure Myr and Myr-loaded nanogels/gels exhibited low cytotoxicity and high biocompatibility. It was reported that the inhibitory effect of pingyangmycin (PMY) to EA.hy926 cells was slower and softer when designed as thermogels, which can be ascribed to the sustained release of PMY from CS/β-GP thermogels (Chen et al, 2014). Hence, it can be inferred that CS/β-GP nanogels/gels were not only a safe delivery system but also had the potential to reduce the cytotoxicity of pure drugs.…”

Self-assembled drug delivery system based on low-molecular-weight bis-amide organogelator: synthesis, properties and in vivo evaluation

“…The researchers also reported that tyrosine derivatives produced the strongest gelation ability and the organogel obtained via N-stearoyl-L-tyrosine methyl ester (StyrOCH 3 ) in sanflower oil showed a G 0 value of 100 kPa with 20 kPa for G 00 at 25 C, which was almost the same as MDP at 37 C, indicating a strong mechanical strength of MDP organogel (Bastiat & Leroux, 2009). Comparing to other in situ forming depot for drug delivery, the system formed by the L-lysine derivative showed a typically gel-like character at low concentration (Yang et al, 2012;Chen et al, 2014).…”