BACKGROUND:Biocompatibility is a key parameter in drug delivery systems. In general, to obtain a proper microparticle carrier, the materials themselves should have excellent biocompatibility. Besides, spherical degree and surface smoothness both have significant influence on biocompatibility.OBJECTIVE: To obtain spherical and smooth poly (lactide-co-glycolide)microparticles, so as to improve the property of biocompatibility.DESIGN: Open experiment.SETTING: Research Laboratory of Biomaterials, Jinan University.MATERIALS: The experiment was conducted in the Research Laboratory of Biomaterials, Jinan University, between June 2004 and January 2005.The materials included poly(lactide-co-glycolide), lysozyme and poly (vinyl alcohol). The other reagents were analytical pure. The instruments included a homogenizer, a mechanical stirrer, an ultrasonic cleaning instrument, a scanning electron microscope and an atomic force microscope.METHODS: ① Preparation of microparticles: Lysozyme was selected as a model protein for encapsulation into poly(lactide-co-glycolide) using a dou-ble emulsion solvent extraction/evaporation method. Three separation methods, namely direct vacuum freeze-drying, filtration and centrifugation,were investigated and compared. ② Observation under the scanning electron microscope: We observed the effect of three separation methods on the shape of microparticles. All the samples were attached to copper mounts and coated with gold, and then were observed with an electron microscope.③ Observation under the atomic force microscope: The morphological structure of the surface was analyzed with atomic force microscope.RESULTS: ① Observation results of scanning electron microscope: Compared with direct vacuum freeze-drying and filtration, centrifugation method was more efficacious in obtaining spherical and smooth microparticles based on the scanning electron microscope pictures. But results also warned us to be more careful when we prepared scanning electron microscope samples using ultrasonic to separate the aggregates. ② Atomic force microscope results indicated that the surface was smooth with the average roughness of 48.55 nm.CONCLUSION: By investigating the influence of different downstream processes, we can obtain spherical and smooth products. Besides, a new one-step method is put forward in constructing some microparticle-combined polymer based scaffolds because the combined scaffolds and microparticles are formed synchronously.

Objective To study the effects of wedelolactone on the expression of P-glycoprotein (P-gp) and to explore the multi-drug resistance reversing mechanism of wedelolactone in K562/A02 cells in vitro.Methods The half maximal inhibitory concentration of ADM in K562/A02 was determined by MTT method.The protein expression level of P-gp was determined by Western blot after wedelolactone pretreatment.Results Wedelolactone remarkably enhanced chemo-sensitivity to ADM of K562/A02 cells.After 0.2, 2, 20 μmol/L different concentration of wedelolactone treatment in 24 h, the relative reversal efficiency of K562/A02 to ADM was 23.5％, 47.1％ and 67.7％, respectively.according to the results of Western blot, wedelolactone was shown to efficiently inhibit the expression of P-gp (P＜0.05).The relative efficiency of K562/A02 to ADM was 25.4％,46％ and 55.6％, respectively.Conclusion Wedelolactone could modulate P-gp expression, and P-gp expression down regulation may be one of the MDR reversal mechanisms in K562/A02 cells by wedelolactone.

The porous foams were prepared by the solvent-casting and particulate-leaching technique using poly(DL-lactide) (PDLLA), poly(DL-lactide)/hydroxyapatite (PDLLA/20wt%HA), and poly(DL-lactide)/beta-tricalcium phosphate(PDLLA/20wt% beta-TCP) respectively. Observations by scanning electron microscopy indicated that the HA and beta-TCP were homogeneously dispersed in the polymer matrix, and the pores of the foams are interconnected, resulting in continuous pore structures. The porosity of PDLLA/HA and PDLLA/beta-TCP foams was lower than that of the pure PDLLA foams, but the compression strength was higher than that of the pure PDLLA foams. The results of the degradation in vitro showed that both HA and beta-TCP had significant inhibitory effects on the degradation of PDLLA, especially the HA. It is expected that the composite foams are of use as scaffolds for bone tissue engineering.
Biocompatible Materials ; chemistry ; Bone Substitutes ; chemical synthesis ; chemistry ; Calcium Phosphates ; chemical synthesis ; chemistry ; Durapatite ; chemical synthesis ; chemistry ; Polyesters ; chemical synthesis ; chemistry ; Polymers ; chemistry ; Porosity ; Tissue Engineering

To prepare poly(lactic acid/glycolic acid/ asparagic acid-co- polyethylene glycol) (PLGA-[ASP-PEG]) and examine the cellular biocompatibility. PLGA-[ASP-PEG] was obtained by bulk ring-opening copolymerization method, examined by infrared spectrometry (IR) and 1H nuclear magnetic resonance spectroscopy (1H NMR). Bone marrow stromal cells(BMSCs) were cultured with PLGA-[ASP-PEG] (experiment gruop) and PLGA (control group) in vitro respectively, and were observed by phase-contrast microscopy and scanning electron microscopy. The resuls showed that PLGA-[ASP-PEG] was obtained and proved by IR and 1H NMR. The BMSCs of the experiment group could well attach to and extend on the surface of the PLGA-[ASP-PEG], and could proliferate and secrete better extracellular matrix, compared with control. The PLGA-[ASP-PEG] has good cellular a biocompatibility. It can be used as a biomaterial for bone tissue engineering.
Aspartic Acid ; chemistry ; Biocompatible Materials ; Bone Matrix ; cytology ; Lactic Acid ; chemistry ; Mesenchymal Stromal Cells ; cytology ; Polyesters ; Polyethylene Glycols ; chemistry ; Polyglycolic Acid ; chemistry ; Polymers ; chemistry ; Tissue Engineering