Effect of additives on the release of a model protein from PLGA microspheres

Development of PLGA-PEG-COOH and gelatin-based microparticles dual delivery system and E-beam sterilization effects for controlled release of BMP-2 and IGF-1

The purpose of this study was to develop a PLGA-PEG-COOH- and gelatin-based microparticles (MPs) dual delivery system for release of BMP-2 and IGF-1. We made and characterized the delivery system based on its morphology, loading capacity, Encapsulation efficiency and release kinetics. Second, we examined the effects of electron beam (EB) sterilization on BMP-2 and IGF-1 loaded MPs and their biological effects. Third, we evaluated the synergistic effect of a controlled dual release of BMP-2 and IGF-1 on osteogenesis of MSCs. Encapsulation efficiency of growth factors into gelatin and PLGA-PEG-COOH MPs are in the range of 64.78% to 76.11%. E-beam sterilized growth factor delivery systems were effective in significantly promoting osteogenesis of MSCs, although E-beam sterilization decreased the bioactivity of growth factors in MPs by approximately 22%. BMP-2 release behavior from gelatin MPs/PEG hydrogel shows a faster release (52.7%) than that of IGF-1 from the PLGA-PEG-COOH MPs/PEG hydrogel (27.3%). The results demonstrate that the gelatin and PLGA-PEG-COOH MPs based delivery system could realize temporal release of therapeutic biomolecules by incorporating different growth factors into distinct microparticles. EB sterilization was an accessible method for sterilizing growth factors loaded carriers, which could pave the way for implementing growth factor delivery in clinical applications.

Preparation, characterization, and in vivo evaluation of insulin-loaded PLA-PEG microspheres for controlled parenteral drug delivery

AIM

The aim of this study was to prepare insulin-loaded poly(lactic acid)-polyethylene glycol microspheres that could control insulin release at least for 1 week and evaluate their in vivo performance in a streptozotocin-induced diabetic rat model.

METHODS

The microspheres were prepared using a water-in-oil-in-water double emulsion solvent evaporation technique. Different formulation variables influencing the yield, particle size, entrapment efficiency, and in vitro release profiles were investigated. The pharmacokinetic study of optimized formulation was performed with single dose in comparison with multiple dose of Humulin 30/70 as a reference product in streptozotocin-induced diabetic rats.

RESULTS

The optimized formulation of insulin microspheres was nonporous, smooth-surfaced, and spherical in structure under scanning electron microscope with a mean particle size of 3.07 microm and entrapment efficiency of 42.74% of the theoretical amount incorporated. The in vitro insulin release profiles was characterized by a bimodal behavior with an initial burst release because of the insulin adsorbed on the microsphere surface, followed by slower and continuous release corresponding to the insulin entrapped in polymer matrix.

CONCLUSIONS

The optimized formulation and reference were comparable in the extent of absorption. Consequently, these microspheres can be proposed as new controlled parenteral delivery system.

Alendronate PLGA microspheres with high loading efficiency for dental applications

PURPOSE

Alendronate sodium, used systemically as a bone protective agent, proved to also be effective locally in various dental bone applications. Development of alendronate-loaded microspheres with high loading efficiency for such applications would be greatly challenged by the hydrophilicity and low MW of the drug. The aim of this study was to incorporate alendronate sodium, into poly (lactide-co-glycolide) (PLGA) microspheres (MS) with high loading efficiency.

METHODS

Three multiple emulsion methods: water-in-oil-in-water (W/O/W), water-in-oil-in-oil (W/O(1)/O(2)) and solid-in-oil-in-oil (S/O(1)/O(2)) were tested. In addition to entrapment efficiency, MS were characterized for surface morphology, particle size, in vitro drug release and in vitro degradation of the polymer matrix. Alendronate microspheres with maximum drug loading and good overall in vitro performance were obtained using the W/O(1)/O(2) emulsion technique.

RESULTS

Drug release from the microspheres exhibited a triphasic release pattern over a period of 13 days, the last fast release phase being associated with more rapid degradation of the PLGA matrix.

CONCLUSIONS

Biocompatible, biodegradable PLGA microspheres incorporating alendronate sodium with high loading efficiency obtained in this study may offer promise as a delivery system for bisphosphonates in dental and probably other clinical applications.

Preparation of large porous biodegradable microspheres by using a simple double-emulsion method for capreomycin sulfate pulmonary delivery

The aim of this work was to evaluate if a simple double-emulsion method could be used for developing a new formulation of large porous microspheres (MS) potentially useful for capreomycin sulfate (CS) pulmonary delivery. Poly(DL-lactide-co-glycolide) was used for MS preparation. A simple W/O/W double-emulsion/solvent evaporation preparation method was employed and MS were characterized by UV spectrophotometry, particle size, and scanning electron microscopy. A computer-generated response surface method (RSM) was employed to evaluate % drug content, volume mean diameter (VMD), and span upon variation of two numeric and two categorical factors. MS size distribution was found to be strongly affected by the homogenization method and the type of emulsifier employed. Mean diameters ranged from 1 to 20 microm. The MS presented a proper morphology, with a highly porous interior and a rough surface. Peptide content ranged between 1 and 20%. The region of optimality was referred to as a low VMD and span values, and a high drug content. The best results were found when using a 20% loading, 19.8-3.2 dichloromethane/acetone ratio, ultraturrax mixing, and HPMC as emulsifier. The double-emulsion method allowed the preparation of CS loaded large porous MS having suitable characteristics to match respirability requirements. The use of RSM helped to establish the conditions to obtain formulations potentially useful for a possible CS pulmonary delivery, by using a simple preparation method with a consistent time, cost, and material saving.

Release of albumin from oligoester plastic matrices: effect of magnesium oxide and bivalent stearates

Biodegradable implantable matrices containing bovine serum albumin were prepared from oligoesters by melting, and subsequently tested on in vitro albumin release. The linear poly (DL-lactic acid) and the branched terpolymer of DL-lactic acid, glycolic acid, and mannitol were synthesized. Products were of similar molecular weight and possessed different thermal and swelling characteristics. Oligoesters were loaded with 4% albumin and plasticized by 30% triacetin. Other additives added into the matrices as albumin stabilizers were divalent stearates and magnesium oxide. The influences of oligomer molecules constitution, divalent ion stearates or magnesium oxide addition, and triacetin concentration on the albumin release were quantified. SDS-PAGE revealed protein hydrolysis during the dissolution tests.