Acid–Base Characteristics of Bromophenol Blue–Citrate Buffer Systems in the Amorphous State

Li, Jinjiang; Chatterjee, Koustuv; Medek, A; Shalaev, Evgenyi; Zografi, George

doi:10.1002/jps.10580

Cited by 43 publications

(39 citation statements)

References 27 publications

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“…All four types of coated ZnO nanoparticles showed δ 11 (COO -) and δ 22 (COO -) peaks, and these were attributed to the carboxylates in citrate and L-serine. 27,28 In the citrate-coated ZnO nanoparticles, the characteristic peak of the quaternary 30 40 2θ ( carbon (C q ) of citrate was found at 76.6 ppm, and C 1 , C 2 , C 3 , C 4 , and C 5 peaks originating from HEPES were observed in the range of 50-60 ppm ( Figure 4A-C). 29 On the other hand, the nuclear magnetic resonance spectra for the L-serine-coated ZnO samples showed peaks at 63.2 ppm and 56.1 ppm, corresponding to the C β and C α carbons in the amino acids.…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

Kim

Choi

Lee

et al. 2014

IJN

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In this study, four types of standardized ZnO nanoparticles were prepared for assessment of their potential biological risk. Powder-phased ZnO nanoparticles with different particle sizes (20 nm and 100 nm) were coated with citrate or L-serine to induce a negative or positive surface charge, respectively. The four types of coated ZnO nanoparticles were subjected to physicochemical evaluation according to the guidelines published by the Organisation for Economic Cooperation and Development. All four samples had a well crystallized Wurtzite phase, with particle sizes of ∼30 nm and ∼70 nm after coating with organic molecules. The coating agents were determined to have attached to the ZnO surfaces through either electrostatic interaction or partial coordination bonding. Electrokinetic measurements showed that the surface charges of the ZnO nanoparticles were successfully modified to be negative (about −40 mV) or positive (about +25 mV). Although all the four types of ZnO nanoparticles showed some agglomeration when suspended in water according to dynamic light scattering analysis, they had clearly distinguishable particle size and surface charge parameters and well defined physicochemical properties.

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Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

Kim

Choi

Lee

et al. 2014

IJN

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“…2.31 13 C Nuclear Magnetic Resonance ( 13 C NMR)-Both solution and solid-state NMR (ssNMR) have been used to estimate the pH and effective 'pH' of solid and semi-solid systems based upon the chemical shift changes of an ionizable functional group [17,18]. NMR is especially useful for establishing the protonation state and pKa of a functional group in either an organic solvent or in the solid-state [17,18].…”

Section: Sample Analysismentioning

confidence: 99%

“…NMR is especially useful for establishing the protonation state and pKa of a functional group in either an organic solvent or in the solid-state [17,18]. Here, 13 C NMR was employed because carbon NMR typically provides a chemical shift difference on the order of several ppm upon protonation [18], compared to shifts < 1 ppm for proton NMR [19]. Fumaric acid was selected as a pH probe because the solution pKa's of its two carboxylic acids (3.0 and 4.5) [20] fall within the range of pH values previously reported for PLGA matrices [10].…”

Section: Sample Analysismentioning

confidence: 99%

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

Houchin

Neuenswander

Topp

2007

Journal of Controlled Release

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The effect of pH modifying excipients on the chemical stability of a model peptide (VYPNGA) and the degradation of poly(DL-lactide-co-glycolide)(PLGA) was studied in PLGA films under accelerated storage conditions. pH modifiers included a basic amine (proton sponge), a basic salt (magnesium hydroxide) and two pH buffers (ammonium acetate and magnesium acetate). Changes in film pH were monitored using 13 C NMR, peptide degradation products were quantified by LC/ MS/MS and PLGA degradation was analyzed by TGA, DSC and SEC. Inclusion of pH modifiers had little impact on PLGA degradation. The proton sponge affected an initial decrease in pH but reduced peptide deamidation and chain cleavage relative to an unbuffered control. Magnesium hydroxide produced an initial increase in pH but also showed increased peptide deamidation. Ammonium acetate decreased pH and increased peptide chain cleavage, presumably due to increased PLGA hydrolysis. Magnesium acetate buffer increased the initial pH but resulted in increased peptide loss. The extent of peptide acylation increased in all formulations, most notably in the proton sponge modified films. The effectiveness of pH modifiers in PLGA formulations under storage conditions is dependant on both the mechanism of pH alteration and the peptide degradation reaction of interest.

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“…13) Some organic acid and inorganic cation combinations (e.g., sodium citrates) also form high glass transition temperature amorphous solids. 14) Various functional groups (e.g., amino, carboxyl, hydroxyl) in the constituting molecules contributes significantly to form the glass-state amorphous salt solids. 15) Producing glass-state amorphous solids by freeze-drying of amino acid and organic acid combinations, and their application in pharmaceutical formulations are interesting topics to explore.…”

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confidence: 99%

Freeze-Drying of Proteins in Glass Solids Formed by Basic Amino Acids and Dicarboxylic Acids

Izutsu¹,

Kadoya

Yomota³

et al. 2009

Chem. Pharm. Bull.

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43Freeze-drying is a popular method of ensuring the stability of proteins that are not stable enough in aqueous solutions during the period required for storage and distribution. 1,2) Various freeze-dried protein formulations contain excipients (e.g., sugars, polymers, and amino acids) that protect proteins from physical and chemical changes. Disaccharides (e.g., sucrose, trehalose) are the most popular among them because they stabilize proteins both thermodynamically and kinetically in aqueous solutions and freeze-dried solids. [3][4][5] The development of freeze-dried protein formulations containing amino acids is often more challenging than the development of formulations with saccharides because of the varied physical and chemical properties (e.g., crystallinity, glass transition temperature) of the freeze-dried amino acids, as well as their tendency to form complexes with other ingredients. 6) Many amino acids are considered to protect proteins basically in similar mechanisms with disaccharides. They thermodynamically stabilize protein conformation in aqueous solutions and probably in frozen solutions by being preferentially excluded from the immediate surface of proteins. 7) Glass-state amorphous solids formed by freeze-drying of the disaccharides or some amino acids protect proteins from structural changes thermodynamically by substituting surrounding water molecules. 8) They also reduce chemical degradation of freeze-dried proteins kinetically by reducing the molecular mobility. 2,8) In addition, some amino acids (e.g., L-arginine) also prevent protein aggregation in aqueous solutions prior to the drying process and after reconstitution. 9) Choosing appropriate counterions that form glass-state solid should be one of the key factors in designing amino acid-based amorphous freeze-dried formulations. 10,11) For example, glass transition temperatures (T g ) of freeze-dried Lhistidine salts depend largely on the counterions. 12) Colyophilization of L-arginine and multivalent inorganic acids (e.g., H 3 PO 4 , H 2 SO 4 ) results in glass-state amorphous solids that protect proteins during the process and storage (e.g., tissue plasminogen activator formulation, PDR 2003). 13) Some organic acid and inorganic cation combinations (e.g., sodium citrates) also form high glass transition temperature amorphous solids. 14) Various functional groups (e.g., amino, carboxyl, hydroxyl) in the constituting molecules contributes significantly to form the glass-state amorphous salt solids. 15) Producing glass-state amorphous solids by freeze-drying of amino acid and organic acid combinations, and their application in pharmaceutical formulations are interesting topics to explore. 15) The purpose of this study was to produce stable amorphous solids that protect proteins by freeze-drying combinations of amino acids and organic acids. The physical properties of frozen solutions and freeze-dried solids containing the popular excipients and model chemicals were studied. The effect of the excipient combinations on the freeze-drying ...

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Acid–Base Characteristics of Bromophenol Blue–Citrate Buffer Systems in the Amorphous State

Cited by 43 publications

References 27 publications

Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

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

Freeze-Drying of Proteins in Glass Solids Formed by Basic Amino Acids and Dicarboxylic Acids

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