Structural and thermodynamic aspects of plasticization and antiplasticization in glassy encapsulation and biostabilization matrices

Antiplasticization of Polymer Materials: Structural Aspects and Effects on Mechanical and Diffusion-Controlled Properties

“…The data for the threshold temperature in Figure 10 (right) show that the cross-over from antiplasticization occurred at a temperature well below the Tg of trehalose (115 • C) even at very low plasticizer concentrations. The data are in good agreement with those reported more recently for the same binary system by Ubbink [137] with respect to the rapid reduction in T A/P at glycerol concentrations greater than 30 wt.%. Similarly, Anopchenko et al [138] have used the relaxation time ratio (τ mix /τ th ) as a measure of the extent of antiplasticization and have obtained similar results described in Figure 10, using the term "critical plasticization" concentration to characterize the cross-over from antiplasticization to plasticization.…”

Molecular Packing, Hydrogen Bonding, and Fast Dynamics in Lysozyme/Trehalose/Glycerol and Trehalose/Glycerol Glasses at Low Hydration

“…Moreover, their results revealed that the antiplasticization of glassy carbohydrate and biopolymer matrices by low-molecular-weight diluents manifests as a strengthening of H-bonding interactions. By means of Fourier-transform infrared (FTIR) spectroscopy, they indeed observed a low-frequency shift of the O-H stretching vibration frequency, ν OH , upon addition of low amounts of water and/or glycerol, 23,26 and found a linear correlation between changes in ν OH and changes in v h , thereby evidencing the interdependence between molecular interactions and molecular packing in these H-bonding systems. 26 Such modifications of structural properties and of H-bonding interactions probably account for the changes in the fast dynamics of glassy carbohydrate matrices described in the literature using various techniques.…”

“…14 Yet, there are still many open questions, in particular on how water, polyols, and sugars interact with each other and/or with proteins in complex glassy mixtures. Low-molecular-weight compounds such as water, glycerol (C 3 H 8 O 3 ), or sorbitol (C 6 H 14 O 6 ), are often regarded as plasticizers of carbohydrate and protein matrices, [15][16][17][18][19][20][21][22][23][24][25][26] since the addition of these small molecules (sometimes referred to as diluents 17,20,21,23,24,[26][27][28][29] ) usually decreases their glass transition temperature, T g , as well as their elastic moduli, and increases the free volume and the water and oxygen permeabilities. However, several studies have demonstrated that they can also act as antiplasticizers, especially at low temperatures and concentrations.…”

Progress in spray-drying of protein pharmaceuticals: Literature analysis of trends in formulation and process attributes

“…[136] However, in resume, the vitrification hypothesis postulates that amorphous carbohydrates kinetically stabilize biomolecules above their glass transition temperature (T g ) by arresting their global molecular mobility (a-relaxation). [137] The water replacement theory proposes that carbohydrates could also thermodynamically stabilize proteins by replacing the hydrogen bonds with water present in the hydrated state and thus, allow the biomolecules to maintain their native conformation. [138] More recently, it has also been shown that carbohydrates are able to retard the local molecular motions of proteins (b-relaxation), thereby providing protein stability in the sub-T g range.…”