Hot-melt extrusion promotes dissolution,extends“spring-parachute”process and inhibits crystallization in supersaturating microparticle systems

Despite the potential advantages of amorphism-induced supersaturation,the merit of new amorphiza-tion formation methods on the properties of the amorphous drug including the stability of the amor-phous state,dissolution/solubility,supersaturation,and"spring-parachute"process is still poorly understood,particularly for certain amorphous supersaturating drug delivery systems(aSDDS).The present work aimed to explore the detailed merit of current attractive amorphization manufacturing methods(i.g.,hot-melt extrusion(HME)technique)on the property improvement of aSDDS in form of amorphous solid dispersion microparticles by employing a model Bcs II drug nitrendipine and a polyvinylpyrrolidone-based model polymer copovidone.Many asDDS systems were developed by various methods,and their physicochemical properties were characterized by SEM,PXRD and DSC.HME-triggered amorphization induced superior supersaturation by the observation of the highest dissolution and solubility.HME induced the optimal supersaturation duration by the observed greatest extension of"spring-parachute"process(e.g,maximum AUCspring-parachute).HME technique is comparable with other techniques for the stabilization of amorphous state during storage.All aSDDS systems by HME and other methods showed improved long-term stability of the amorphous state in comparison to the pure amorphous drug.Fourier transformation infrared spectroscopy,Noyes-Whitney equation,nucleation theory and Gibbs free energy of transfer(△G)were used to analyze the underlying mechanisms.Mo-lecular mechanism studies indicated that HME caused a stronger crystallization inhibition effect in the asDDS systems than other methods,but molecular interaction is not a dominant mechanism for property enhancement caused by HME.For the mechanism associated with the polymer itself(PVPVA64),it could inhibit the drug recrystallization,solubilize the drug spontaneously and cause the improved molecular interactions in all aSDDS systems.This study provided a deep insight into detailed advantage of HME-triggered supersaturation/amorphization and facilitated the applications of the technique both in the field of particuology and in pharmaceutical industry.

Theoretical insights into influence of additives on sulfamethoxazole crystal growth kinetics and mechanisms

In this work,the influence of the initial chemical potential gradient,stirring speed,and polymer type on sulfamethoxazole(SMX)crystal growth kinetics was systematically investigated through density functional theory(DFT)calculations,experimental measurements and the two-step chemical potential gradient model.To investigate the influence of different conditions on the thermodynamic driving force of SMX crystal growth,SMX solubilities in different polymer solutions were studied.Four model polymers effectively improved SMX solubility.It was further found that polyvinylpyrrolidone(PVP)and hydroxypropyl methyl cellulose(HPMC)played a crucial role in inhibiting SMX crystal growth.However,polyethylene glycol(PEG)promoted SMX crystal growth.The effect of the polymer on the crystal growth mechanisms of SMX was further analyzed by the two-step chemical potential gradient model.In the system containing PEG 6000,crystal growth is dominated by the surface reaction.However,in the system containing PEG 20000,crystal growth is dominated by both the surface reaction and diffusion.In addition,DFT calculations results showed that HPMC and PVP could form strong and stable binding energies with SMX,indicating that PVP and HPMC had the potential ability to inhibit SMX crystal growth.