In vitro drug release rule of basic fibroblast growth factor-poly(lactic-co-glycolic-acid) copolymer microspheres:Promotion of the venous flap survival in rabbits?

Hongju XIE; Ming LI; Ying DENG; Nian CHEN

ABSTRACT

BACKGROUND:

Compared with normal physiological flap,main advantage of venous skin flap is that it throws off the limitation of arterial vascular territory on donor site and recipient site of traditional axial skin flap.However,its survival rate is unstable.

OBJECTIVE:

To explore effects of basic fibroblast growth factor (bFGF)-[poly(lactic-co-glycolic-acid)] (PLGA)-sustained release microspheres on the survival of rabbit venous flaps.DESIGN,TIME AND

SETTING:

A randomized controlled animal study was performed at the University of South China from May to October 2008.MATERIALSA total of 24 healthy New Zealand rabbits were equally randomly assigned to bFGF-PLGA sustained release microsphere,blank microsphere and blank control groups.

METHODS:

The formulation of bFGF microspheres was optimized by orthogonal design.bFGF-PLGA microspheres were prepared by optimized method.Lateral abdominal wall skin flap was created in rabbits from 3 groups.Five days before operation,28.85 g/L bFGF-PLGA microspheres 3 mL (containing bFGF 20 ?g) was intradermally injected into rabbits from the bFGF-PLGA sustained release microsphere group.An equal volume of blank microsphere + bFGF was injected in the rabbits of the blank microsphere group.Rabbits from the blank control group were infused with the same volume of saline.MAIN OUTCOME

MEASURES:

Morphology and particle distribution of bFGF-PLGA microspheres,drug loading volume,encapsulation efficiency,in vitro drug release characteristics were measured.After seven days,the survival area of skin was determined.Rabbit skin samples received CD34+ immunohistochemical staining to detect the expression of CD34+ and average number of blood vessels.

RESULTS:

The bFGF microsphere prepared based on optimized formulation exhibited well-defined properties,with the even and uniform sphere in appearance,regular particles without adhesion,about 98% of particles with a size distribution between 12.50 to 43.49 ?m,with a mean particle size of 26.93 ?m and size span of (0.611 ? 6.60).The drug loading volume and encapsulation efficiency of bFGF microsphere reached [(23.11?0.44)?10-3]% and (86.51?0.83)%,respectively.In the burst release phase,the rate of in vitro drug release amounted to 27.78%,but rose to 81.56% accumulatively 30 days later.The in vitro drug release of bFGF microsphere corresponded with Higuichi equation (r=0.997).The sustained-release microspheres,blank microspheres and normal saline group,the average survival of the flap and the average number of blood vessels were similar (P=0.597,P=0.336),but still significantly lower than the bFGF-PLGA sustained release microsphere group (P=0.000).Results of immunohistochemical staining revealed that bFGF-PLGA promoted blood supple between flap and surroundings,improved flap survival and abundant CD34+ expression.

CONCLUSION:

bFGF microsphere with good morphology,high drug loading volume and encapsulation efficiency can be obtained using W/O/W multiple emulsion evaporation method.The bFGF microsphere can promote the survival of rabbit venous flaps through a long period due to sustained release of bFGF.