Jiwei Liu1, Yan Xu1, Yonglu Wang1, Hao Ren1, Zhengjie Meng2, Kuntang Liu1, Zhe Liu1, He Huang3, Xueming Li4. 1. School of Pharmaceutical Science, Nanjing Tech University, No. 30 Puzhu South Road, Nanjing, 211816, China. 2. School of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30 Puzhu South Road, Nanjing, 211816, China. 3. School of Pharmaceutical Science, Nanjing Tech University, No. 30 Puzhu South Road, Nanjing, 211816, China. huangh@njtech.edu.cn. 4. School of Pharmaceutical Science, Nanjing Tech University, No. 30 Puzhu South Road, Nanjing, 211816, China. xuemingli@njtech.edu.cn.
Abstract
PURPOSE: The purpose of this study was to characterize and detail the mechanism of a smart Ca2+ release depot (Ca3(PO4)2) about its ability for sustainable inhibition on peptide acylation within PLGA microspheres. METHODS: The octreotide acetate release and acylation kinetics were analyzed by RP-HPLC. Changes of Ca2+ concentration and adsorption behavior were determined by a Calcium Colorimetric Assay Kit. The inner pH changes were delineated by a classic pH sensitive probe, Lysosensor yellow/ blue® dextran. Morphological changes of microspheres, adsorption between polymer and additive, transformation of Ca3(PO4)2 were characterized using SEM, FTIR and SSNMR separately. RESULTS: Before and after microspheres formulation, the property and effectiveness of Ca3(PO4)2 were investigated. Compared with a commonly used calcium salt (CaCl2), high encapsulation efficiency (96.56%) of Ca3(PO4)2 guarantees lasting effectiveness. In an increasingly acidic environment that simulated polymer degradation, the poorly water-soluble Ca3(PO4)2 could absorb protons and transform into the more and more soluble CaHPO4 and Ca(H2PO4)2 to produce sufficient Ca2+ according to severity of acylation. The corresponding Ca2+ produce capacity fully met the optimum inhibition requirement since the real-time adsorption sites (water-soluble carboxylic acids) inside the degrading microspheres were rare. A sustained retention of three switchable calcium salts and slow release of Ca2+ were observed during the microsphere incubation. FTIR results confirmed the long-term inhibition effect induced by Ca3(PO4)2 on the adsorption between drug and polymer. CONCLUSIONS: With the presence of the smart Ca2+ depot (Ca3(PO4)2) in the microspheres, a sustainable and long-term inhibition of peptide acylation was achieved.
PURPOSE: The purpose of this study was to characterize and detail the mechanism of a smart Ca2+ release depot (Ca3(PO4)2) about its ability for sustainable inhibition on peptide acylation within PLGA microspheres. METHODS: The octreotide acetate release and acylation kinetics were analyzed by RP-HPLC. Changes of Ca2+ concentration and adsorption behavior were determined by a Calcium Colorimetric Assay Kit. The inner pH changes were delineated by a classic pH sensitive probe, Lysosensor yellow/ blue® dextran. Morphological changes of microspheres, adsorption between polymer and additive, transformation of Ca3(PO4)2 were characterized using SEM, FTIR and SSNMR separately. RESULTS: Before and after microspheres formulation, the property and effectiveness of Ca3(PO4)2 were investigated. Compared with a commonly used calcium salt (CaCl2), high encapsulation efficiency (96.56%) of Ca3(PO4)2 guarantees lasting effectiveness. In an increasingly acidic environment that simulated polymer degradation, the poorly water-soluble Ca3(PO4)2 could absorb protons and transform into the more and more soluble CaHPO4 and Ca(H2PO4)2 to produce sufficient Ca2+ according to severity of acylation. The corresponding Ca2+ produce capacity fully met the optimum inhibition requirement since the real-time adsorption sites (water-soluble carboxylic acids) inside the degrading microspheres were rare. A sustained retention of three switchable calcium salts and slow release of Ca2+ were observed during the microsphere incubation. FTIR results confirmed the long-term inhibition effect induced by Ca3(PO4)2 on the adsorption between drug and polymer. CONCLUSIONS: With the presence of the smart Ca2+ depot (Ca3(PO4)2) in the microspheres, a sustainable and long-term inhibition of peptide acylation was achieved.
Entities:
Keywords:
Ca3(PO4)2; Peptide acylation; high encapsulation; long-term inhibition; smart depot
Authors: Zhigao Niu; Erik Tedesco; Federico Benetti; Aloïse Mabondzo; Isabella Monia Montagner; Ilaria Marigo; David Gonzalez-Touceda; Sulay Tovar; Carlos Diéguez; Manuel J Santander-Ortega; María J Alonso Journal: J Control Release Date: 2017-02-21 Impact factor: 9.776