By using atomic-force and scanning electron microscopies (AFM, SEM), wide-angle and small-angle X-ray diffraction (WAXD and SAXS), and thermal and infrared spectroscopy characterization, mechanisms and correlations between lamellar reassembly, phase separation domains, and birefringence patterns in crystallized spherulites in poly(hydroxyl butyrate) (PHB) were probed in detail. Crystallization-induced phase separation in PHB blended with amorphous poly(methyl acrylate) (PMA) produces pebble-like PMA domains, which influence the birefringence types (positive vs negative types) of spherulites in crystallized blends with respect to composition and temperature. Extents of crystallization-induced phase separation were dependent on temperature and composition; for a fixed PHB/PMA (60/40) blend composition the phase separation extent was inversely proportional to temperature of crystallization (T c ). Correspondingly, depending on the extents of phase separation (counted as quantitative ratio of pebble-like PMA domains divided by entire area of the blend samples), the Maltese cross in spherulite patterns of PHB in the blend may rotate from the original positive-type spherulites at T c = 90°C to negative-type spherulites at T c = 60°C. The SAXS analyses showed the thickness variation of PHB lamellae (or PHB + amorphous polymer long periods) with T c was not an influencing factor, but that the formation of grains in the PMA domains from the crystallizationinduced phase separation could majorly influence the optical birefringence. Correlations among the phase domains, lamellae assembly, transitions from positive-type, unusual-type, and negative-types of crystallized spherulites in polymers have been expounded upon.

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This study investigated two new biodegradable polymers as gene controlled-released coatings for gene transfer. Poly(ethylene glycol)-co-poly(D,L-lactic acid) (PELA) and poly(ethylene glycol)-co-poly(lactic acid)-co-poly(glycolic acid) random copolymer (PELGA) were synthesized and used as microspheres matrices with encapsulated plasmid pCH110. The plasmid loading efficiency, cytotoxicity, transfection efficiency and in vitro degradation and release profiles of microsphere complexes were evaluated in details. The biodegradable polymers showed high DNA loading efficiency and low cytotoxicity as gene controlled-released coatings, and the poly(ethylene glycol) (PEG) contents of polymer matrices influenced the diameter, loading efficiency and transfection efficiency of plasmid DNA within the microspheres. The average diameters of PELA and PELGA microspheres were between 0.5 and 1.5 microm, and the plasmid loading efficiency was 62 and 73% for PELA and PELGA microspheres with 10% PEG content, respectively. In vitro testing showed a gradual release profile of DNA from polymeric matrices. The polymers/DNA microspheres had high transfection efficiency and early gene expression and maintenance of gene expression level for up to 96 h, although transfection efficiency were slightly lower than that of liposome in the initial 24 h. The biodegradable polymeric materials possess potential superiority as gene carriers.

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