Synthesis And Properties Study Of Amino Acids-based Poly (Ester Amide)s And Their Block Copolymers

Aliphatic polyesters, such as polyglycolide, polylactide, poly(ε-caprolactone)and their copolymers, are well-known among biodegradable polymers. They arewidely applied not only in biomedical applications but also in packaging, and manyother items of short-term use. However, the relatively unchangeable polyesterbackbone, which could otherwise be used for tuning physicochemical properties andintroducing bioactive units, limits their further biomedical applications. Furthermore,the level of in vivo inflammation induced by the absorbable polyesters duringabsorption is still relatively high. Polyamides have excellent mechanical andprocessing properties in comparison with polyesters, and moreover, they could beeasily modified. Therefore, the combination of these two classes of polymers wouldproduce a new family of polymeric materials, poly(ester amide)s (PEAs). PEAs haveboth ester and amide blocks on their backbones and are regarded as promisingbiodegradable materials, as they combined good mechanical, thermal and processingproperties of polyamides and the biodegradability of polyesters. Based on abovereasons, we studied PEA and its derivatives in this work:1. Novel alternating multiblock copolymers (PEA-b-AP) based on poly(esteramide)(PEA)/aniline pentamer (AP) were prepared by a two-stage active solutionpolycondensation. The new synthesis approach proceeded smoothly and thecomplicated purification step for separating the intermediate products was eliminated.The length of PEA blocks was regulated by a variation of nucleophilic/electrophilicmonomer ratios. The properties of products can be adjusted, such as mechanicalproperties, biodegradability, solubility, in vivo and in vitro cell and tissue complability,electrobility, and so on. The chemical structures of copolymers were confirmed byNMR and FTIR. The UV-visible spectroscopy analysis has shown that the copolymerswere electroactive. The study of thermal and mechanical properties was demonstratedthat the new copolymers may have potential application as a tissue engineeringscaffold materials. We also primarily investigated the degradability and biocompatibility of the copolymers, and proved that the PEA-b-AP copolymers weredegradable and facilitated the RSC96cells attachment and proliferation. Future workwill focus on exploiting the effect of electrical stimulation on cell function, andcarrying out in vivo tests for assessment of tissue compatibility.2. Amphiphilic triblock copolymer mPEG-b-PEA-b-mPEG based on aminoacid-based functional poly(ester amide)(PEA)/mPEG-NH2were prepared by acoupling reaction. The structure and properties of the copolymers were characterizedby NMR, GPC and FTIR. Self-assembly of the block copolymer,mPEG-b-PEA-b-mPEG, was investigated in phosphate buffer at pH7.4. Micelleformation was characterized by dynamic light scattering (DLS). Transmission electronmicroscopy confirmed a spherical morphology in phosphate buffer. The loading of ananthracycline anticancer drug, Doxorubicin (DOX), into micelles was demonstratedwith loadings as high as10.25%wt of DOX per wt of mPEG-b-PEA-b-mPEG inphosphate buffer. Drug-loaded micelles exhibited enhanced cellular uptake ofdoxorubicin compared to free doxorubicin solution in Henrietta Lacks’s cells line andshowed a better cytotoxicity of doxorubicin at equivalent dose in drug-loadedmicelles. The in vitro release behaviors could be adjusted by content of hydrophobicpolyester and pH of the release medium. The results suggested that the self-assemblysystem based on amphiphilic triblock copolymer mPEG-b-PEA-b-mPEG hadpotential application in tumor tissular and intracellular targeting drug delivery systemsin vivo.