Pharmacokinetic and pharmacodynamic profiles of recombinant human erythropoietin-loaded poly(lactic-co-glycolic acid) microspheres in rats.

AIM: To characterize the pharmacokinetic and pharmacodynamic profiles of the recombinant human erythropoietin (rhEPO)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres in rats. METHODS: The rhEPO-loaded microspheres were prepared using a solid-in-oil-in-water emulsion method. Pharmacokinetics and pharmacodynamics of the rhEPO-loaded microspheres were evaluated in male Sprague-Dawley rats. The serum rhEPO level was determined with ELISA. The level of anti-rhEPO antibody in the serum was measured to assess the immunogenicity of rhEPO released from the microspheres. RESULTS: rhEPO was almost completely released from the PLGA microspheres in vitro, following zero-order release kinetics over approximately 30 d. After intramuscular injection (10,000 or 30,000 IU rhEPO/kg) in the rats, the serum rhEPO concentration reached maximum levels on d 1, then decreased gradually and was maintained at nearly steady levels for approximately 4 weeks. Furthermore, the release of rhEPO from the PLGA microspheres was found to be controlled mainly by a dissolution/diffusion mechanism. A good linear correlation (R(2)=0.98) was obtained between the in vitro and in vivo release data. A single intramuscular injection of the rhEPO-loaded PLGA microspheres (10,000 or 30,000 IU rhEPO/kg) in the rats resulted in elevated hemoglobin and red blood cell concentrations for more than 28 d. Moreover, the immunogenicity of rhEPO released from the PLGA microspheres was comparable with that of the unencapsulated rhEPO. CONCLUSION: The results prove the feasibility of using the PLGA-based microspheres to deliver rhEPO for approximately 1 month.

Sustained release of low molecular weight heparin from PLGA microspheres prepared by a solid-in-oil-in-water emulsion method.

Biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres for the sustained release of low molecular weight heparin (LMWH) were prepared by a soild-in-oil-in-water (s/o/w) emulsion method. Prior to encapsulation, the LMWH micro-particles were fabricated by a modified freezing-induced phase separation method. The micro-particles were subsequently encapsulated into PLGA microspheres. Process optimization revealed that the NaCl concentration in the outer phase of s/o/w emulsion played a critical role in determining the properties of the microspheres. When the NaCl concentration increased from 0% to 5%, the encapsulation efficiency significantly increased from 51.5% to 76.8%. The initial burst release also decreased from 37.3% to 12.4%. In vitro release tests showed that LMWH released from PLGA microspheres in a sustained manner for about 14 days. Single injection of LMWH-loaded PLGA microspheres into rabbits resulted in an elevation of an anti-factor Xa activity for about 6 days. Furthermore, the integrity of the encapsulated LMWH was preserved during encapsulation process.

[Effect of NaCl in outer water phase on the characteristics of BSA-loaded PLGA sustained-release microspheres fabricated by a solid-in-oil-in-water emulsion technique].

The aim of this study is to investigate the critical factor affecting the properties of PLGA microspheres fabricated by a solid-in-oil-in-water (S/O/W) emulsion technique with BSA as a model protein. Prior to encapsulation, the BSA microparticles were fabricated by a modified freezing-induced phase separation method. The microparticles were subsequently encapsulated into PLGA microspheres by S/O/W emulsion method, then Motic BA200 biological microscope, confocal laser scanning microscope, scanning electron microscope were used to observe the structure of S/O/W emulsion and PLGA microspheres. The protein content extracted or released from BSA microspheres was measured by Bradford protein assay method. It was found that NaCl added in the outer aqueous phase effectively suppressed material exchange between the inner and outer phase of S/O/W emulsion. Then, the structure and permeability of obtained microspheres were influenced. As a result, with the increase of NaCl concentration in the outer aqueous phase, the encapsulation efficiency of microspheres significantly increased from 60% to more than 85%, the burst release of microspheres reduced from 70% to 20%, and the particle size decreased from 103 microm to 62 microm. Furthermore, the rehydration of encapsulated protein was also retarded and then integrity of BSA was successfully protected during encapsulation process. In vitro release test showed that BSA released from PLGA microspheres in a sustained manner for more than 30 days.

Stabilization and encapsulation of recombinant human erythropoietin into PLGA microspheres using human serum albumin as a stabilizer.

The aim of this study was to prepare recombinant human erythropoietin (rhEPO) loaded poly(lactic-co-glycolic acid) (PLGA) microspheres using human serum albumin (HSA) as a stabilizer. Prior to encapsulation, the rhEPO-HSA mixture microparticles were fabricated using a modified freezing-induced phase separation method. The microparticles were subsequently encapsulated into PLGA microspheres. Process optimization revealed that the polymer concentration in the organic phase and the sodium chloride (NaCl) concentration in the outer water phase of the s/o/w emulsion played critical roles in determining the properties of the resultant microspheres. An in vitro release test showed that rhEPO was released from PLGA microspheres in a sustained manner up to 30 days. A single injection of rhEPO-loaded PLGA microspheres in Sprague-Dawley rats resulted in elevated hemoglobin and red blood cell concentrations for about 33 days. The stability of the rhEPO within the PLGA microspheres was systematically investigated by size-exclusion high-performance liquid chromatography (SEC-HPLC), SDS-PAGE, western blot and in vivo biological activity assay. The stability of rhEPO released from rhEPO-loaded microspheres was also examined by western blot. The results suggested that the integrity of rhEPO was successfully protected during the encapsulation process and the release period from polymeric matrices.