Preparation Of Amphiphilic Star Block Coplymers Based On PCL And PEG And Their Encapsulation Behavior On Quercetin

Amphiphilic star coplymers based on poly(ε-caprolactone) andpolyethylene glycol are of particular interest because they possess bothbiocompatibility and biodegradablility. These coplymer micelles havepotential applications in encapsulation of drug and gene. Quercetin is anhydrophobic anticancer drug which is abundantly present in citrus fruits,vegetables and herbs. However, its poor solubility in water restricts itsmedicinal value. In this thesis, a series of amphiphilic star-shapedcopolymers based on PCL and PEG were prepared and theirencapsulation behaviors on Quercetin was also investigated.This thesis was divided into four parts:(1) Based on different ratios of ε-CL and PER, initiated by PER aseries of4sPCL with different lengths were prepared through ringopening polymerization of ε-caprolactone using Sn(Oct)2as the catalyst.Monomethoxy-terminated PEG was then converted into thecorresponding carboxylic acid MPEG-COOH. Finally, amphiphilic starcoplymers4s(PCL-b-PEG) with low polydispersity index (PDI<1.2) wassynthesized via an esterification reaction between MPEG-COOH andhydroxyl-terminated PCL.(2) A series of nsPCL with low polydispersity index (PDI≈1.1)was synthesized through ring opening polymerization of ε-caprolactoneinitiated by monohydric alcohols or polyhydric alcohols, such asneopentyl alcohol, ethylene glycol, tri(hydroxymethyl)propane,dipentaerythrito et al. Amphiphilic star coplymers ns(PCL-b-PEG) withdifferent arms and low polydispersity index (PDI<1.2) was obtained bythe reaction of nsPCL and MPEG-COOH. (3) The self-assembly behavior and biocompatibility of micellsthe amphiphilic star shaped coplymers formed in aqueous solution wasinvestigated. In aqueous solution, these amphiphilic star-shapedcoplymers can form polymeric micelles with hydrophobic segment PCLas the core and the hydrophilic segment PEG as the shell. This type ofmicelle almost have no damage to normal cells and has goodbiocompatibility.(4) Encapsulation behavior on Quercetin of the copolymermicelles was investigated. Drug loading (DL) was estimated by themeasurement of UV–visible spectrophotometer and the effect of thelength of core PCL on DL was also considered. With degree ofpolymerization for PCL in4s(PCLm-b-PEG) increacing, the DL was firstincreased then decreased.4s(PCL46-b-PEG47) showed the highest DL.When the ratio of Drug/Polymer was1/10, DL was up to9.02%. Inaddition, the effect of the number of the copolymers’ arms on DL wasalso studied. It was found that DL of ns(PCL-b-PEG) decreased while thenumber of the copolymers’ arms increased when both the length of PCLand PEG chain was basically identical.