Preparation, Characterization, and Pharmacodynamics of Exenatide-Loaded Poly(DL-lactic-co-glycolic acid) Microspheres

Abstract

ExperimentalMaterials Exenatide was synthesized in our laboratory by Peptide Synthesizer (PS3 Model, Protein Technologies Inc., U.S.A.) using the FMOC solid-phase peptide synthesis approach, and purified by reverse phase (RP)-HPLC to Ͼ95% purity. PLGA and poly lactic acid (PLA) were purchased from Birmingham Polymers (Birmingham, AL, U.S.A.). The micro-bicinchoninic acid (BCA) Assay Kit was supplied by Pierce. Polyvinyl alcohol (PVA) and STZ were purchased from Sigma. All other chemicals were of analytical grade.Animals Kun Ming (KM) mice with the body weight of 18-20 g were Exenatide (synthetic exendin-4), a 39-amino acid peptide, was encapsulated in poly(DL-lactic-co-glycolic acid) (PLGA) microspheres as a sustained release delivery system for the therapy of type 2 diabetes mellitus. The microspheres were prepared by a double-emulsion solvent evaporation method and the particle size, surface morphology, drug encapsulation efficiency, in vitro release profiles and in vivo hypoglycemic activity were evaluated. The results indicated that the morphology of the exenatide PLGA microspheres presented as a spherical shape with smooth surface, and the particle sizes distributed from 5.8 to 13.6 mm. The drug encapsulation efficiency tested by micro-bicinchoninic acid (BCA) assay was influenced by certain parameters such as inner and outer aqueous phase volume, PLGA concentration in oil phase, polyvinyl alcohol (PVA) concentrations in outer aqueous phase. Moreover, in vitro release behaviors were also affected by some parameters such as polymer type, PLGA molecular, internal aqueous phase volume, PLGA concentration. The pharmacodynamics in streptozotocin (STZ)-induced diabetic mice suggested that, exenatide microspheres have a significant hypoglycemic activity within one month, and its controlling of plasma glucose was similar to that of exenatide solution injected twice daily with identical exenatide amount. In conclusion, this microsphere could be a well sustained delivery system for exenatide to treat type 2 diabetes mellitus.

Glucagon‐Like Peptide‐1 (GLP‐1)‐Based Therapeutics: Current Status and Future Opportunities beyond Type 2 Diabetes

“…[11] Analysis of GLP-1 using 2D-NMR revealed that the first seven amino acid residues (7-13)a tt he N-terminusf orm ar andom coil structure,w hich is thought to be responsible for interactions with the main bindingp ortion of the GLP-1R ( Figure 2). [12] This is followed by ah elical region (14)(15)(16)(17)(18)(19)(20), al inker region (21)(22)(23) and as econd helical region (24-35) ( Figure 2). [12] Alanine scanningo fe ach GLP-1 residue further revealed that residues 7, 10, 12, 13, 15, 28 and 29 ( Figure 2) are important for binding to, and activation of the GLP-1R, with mutations at these positions reducing GLP-1Ra ffinity by 132-425-fold and potency by 12-3900-fold.…”

“…In this formulation, the exendin‐4 peptide is noncovalently entrapped within a biodegradable poly( d,l ‐lactide‐co‐glycolide) (PLG) polymer to form 60 μm microspheres . This results in slow release of exendin‐4 from the polymeric matrix by diffusion and hydrolysis of the microspheres, prolonging its half‐life to 5–6 days in humans, which enables more convenient once‐weekly subcutaneous injection and potentially once‐monthly dosing in the future . Despite these advantages, PLG depot formulations can display irregular drug release and instability of their peptide cargos following hydration and administration, which may have adverse clinical outcomes (e.g., the potential for nausea and vomiting due to an initial burst release, followed by a subsequent “lag‐phase”, which may decrease efficacy) .…”

Novel drug delivery system: an immense hope for diabetics

“…Literature unfolds various types of traditional liposomes, such as uni-lamellar (ULV) or multi-lamellar vesicular systems (MLV) (Ye et al, 2000;Karathanasis et al, 2006). Drugs/actives like cytotoxic, antidiabetics, anti-cancerous, proteinaceous and genetic material have been encapsulated in liposomal systems and it has been (Liu et al, 2010;Ryan et al, 2013;Qi et al, 2013;Xuan et al, 2013) …”

Novel AGLP-1 albumin fusion protein as a long-lasting agent for type 2 diabetes

“…The conjugation of long-chain palmitic acid (PAA, C16 to GLP-1 increased the in vivo duration of GLP-1 substantially (10). The encapsulation of another GLP-1 analog, exendin-4 from the lizard salivary gland peptide also showed sustained circulation of the peptide in the body (11). However, it may be necessary to design the long-acting technology for a GLP-1 analog for the effective delivery of this important therapeutic peptide in order to improve the patient compliance significantly.…”