Leveraging Framework Instability: A Journey from Energy Storage to Drug Delivery

Amorphous pharmaceuticals often suffer from poor physical stability, which can negate their high solubility, fast dissolution rate, and better oral bioavailability vs. crystalline forms. This represents a major hurdle to processing, storage, and delivery of amorphous pharmaceuticals. Several approaches to addressing these problems have been pursued, but there is still a need for a general method for stabilizing the amorphous form. We describe a novel approach using a water-unstable metal-organic framework as a drug delivery vehicle that demonstrates improved amorphous form stability accompanied by remarkably enhanced solubility and a fast dissolution rate. This research project spanned eleven years from conception to realization and dissemination. With origins in understanding the stability or porous solids for energy storage materials, the work also highlights potential of basic science understanding to illuminate new areas of application.

Importance of Mesoporous Silica Particle Size in the Stabilization of Amorphous Pharmaceuticals—The Case of Simvastatin

In this paper, the role of mesoporous silica (MS) particle size in the stabilization of amorphous simvastatin (SVT) is revealed. For inhibiting recrystallization of the supercooled drug, the two MS materials (Syloid® XDP 3050 and Syloid® 244 FP) were employed. The crystallization tendency of SVT alone and in mixture with the MS materials was investigated by Differential Scanning Calorimetry (DSC) and Broadband Dielectric Spectroscopy (BDS). Neither confinement of the SVT molecules inside the MS pores nor molecular interactions between functional groups of the SVT molecules and the surface of the stabilizing excipient could explain the observed stabilization effect. The stabilization effect might be correlated with diffusion length of the SVT molecules in the MS materials that depended on the particle size. Moreover, MS materials possessing different particle sizes could offer free spaces with different sizes, which might influence crystal growth of SVT. All of these factors must be considered when mesoporous materials are used for stabilizing pharmaceutical glasses.

Structural Characterisation of Amorphous Solid Dispersions via Metropolis Matrix Factorisation of Pair Distribution Function Data

We measure the X-ray pair distribution functions (PDFs) of a series of felodipine:copovidone amorphous solid dispersions. Using a newly-developed Metropolis Matrix Factorisation (MMF) algorithm we extract from these data the PDF of the amorphous felodipine component in isolation. Our MMF analysis allows quantification of the degree of drug crystallinity in each sample, and structural characterisation of the amorphous drug <i>via</i>its PDF. Comparison with atomistic simulations reveals that the (in)accessibility of conformational rotamers distinguishes amorphous and crystalline felodipine, in turn suggesting design routes for stabilising the amorphous form. We discuss the conceptual importance of our results in the context of characterising not only amorphous pharmaceuticals, but complex mixtures in general.

Structural Characterisation of Amorphous Solid Dispersions via Metropolis Matrix Factorisation of Pair Distribution Function Data

We measure the X-ray pair distribution functions (PDFs) of a series of felodipine:copovidone amorphous solid dispersions. Using a newly-developed Metropolis Matrix Factorisation (MMF) algorithm we extract from these data the PDF of the amorphous felodipine component in isolation. Our MMF analysis allows quantification of the degree of drug crystallinity in each sample, and structural characterisation of the amorphous drug <i>via</i>its PDF. Comparison with atomistic simulations reveals that the (in)accessibility of conformational rotamers distinguishes amorphous and crystalline felodipine, in turn suggesting design routes for stabilising the amorphous form. We discuss the conceptual importance of our results in the context of characterising not only amorphous pharmaceuticals, but complex mixtures in general.