Deamidation, acylation and proteolysis of a model peptide in PLGA films

Effect of excipients on PLGA film degradation and the stability of an incorporated peptide

“…In a previous report, we demonstrated VYPNGA undergoes three types of chemical degradation when encapsulated in PLGA: deamidation, amide bond cleavage and acylation [16]. The products of these reactions were identified by LC/MS/MS and described in detail in the previous report [16].…”

“…Films containing 0.3% w/w VYPNGA in PLGA were prepared as described in a previous publication [16] by dissolving 100 mg/mL polymer and 300 μg/mL peptide in acetone and sonicating for 30 min to enhance dissolution. Either 3% w/w (in relation to polymer) proton sponge (pKa =12.34), 3% w/w Mg(OH) 2 (pKa = 9.5-10.5), or 0.13M NH 4 Ac (pKa = 7.0) was added to the formulation in an attempt to control pH in the degrading films [10].…”

“…For peptide degradation analysis, films were dissolved and filtered as described previously [16]. Solid samples for NMR, DSC, and TGA analysis were removed from the glass coverslips with a razor blade.…”

“…accomplished by precursor and product ion scans, and chromatographic separations were performed using a Waters 2690 HPLC system (Milford, MA) with an Econosphere C18 reversed-phase column (4.6 x 250 mm, 5-μm particle size; Alltech Associates, Inc., Deerfield, IL) as described previously [16]. In short, product quantification was conducted using a gradient RP-HPLC method ranging from 1-30% acetonitrile at a flow rate of 1 mL/min.…”

“…The products of these reactions were identified by LC/MS/MS and described in detail in the previous report [16]. In this study, several types of pH modifiers were investigated for their ability to either stabilize or destabilize a model peptide incorporated in PLGA films: a superbasic amine or proton sponge, a basic salt, a neutral buffer, and a slightly acidic buffer.…”