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This study demonstrates the applicability of terahertz time-domain spectroscopy (THz-TDS) in evaluating the solid-state of the drug in selective laser sintering-based 3D printed dosage forms. Selective laser sintering is a powder bed-based 3D printing platform, which has recently demonstrated applicability in manufacturing amorphous solid dispersions (ASDs) through a layer-by-layer fusion process. When formulating ASDs, it is critical to confirm the final solid state of the drug as residual crystallinity can alter the performance of the formulation. Moreover, SLS 3D printing does not involve the mixing of the components during the process, which can lead to partially amorphous systems causing reproducibility and storage stability problems along with possibilities of unwanted polymorphism. In this study, a previously investigated SLS 3D printed ASD was characterized using THz-TDS and compared with traditionally used solid-state characterization techniques, including differential scanning calorimetry (DSC) and powder X-ray diffractometry (pXRD). THz-TDS provided deeper insights into the solid state of the dosage forms and their properties. Moreover, THz-TDS was able to detect residual crystallinity in granules prepared using twin-screw granulation for the 3D printing process, which was undetectable by the DSC and XRD. THz-TDS can prove to be a useful tool in gaining deeper insights into the solid-state properties and further aid in predicting the stability of amorphous solid dispersions.

We seek to further addresss the questions posed by Moseson et al. regarding whether any residual crystal level, size, or characteristic is acceptable in an amorphous solid dispersion (ASD) such that its stability, enhanced dissolution, and increased bioavailability are not compromised. To address this highly relevant question, we study an interesting heat- and shear-labile drug in development, LY3009120. To study the effects of residual crystallinity and degradation in ASDs, we prepared three compositionally identical formulations (57–1, 59–4, and 59–5) using the KinetiSol process under various processing conditions to obtain samples with various levels of crystallinity (2.3%, 0.9%, and 0.1%, respectively) and degradation products (0.74%, 1.97%, and 3.12%, respectively). Samples with less than 1% crystallinity were placed on stability, and we observed no measurable change in the drug's crystallinity, dissolution profile or purity in the 59–4 and 59–5 formulations over four months of storage under closed conditions at 25 °C and 60% humidity. For formulations 57–1, 59–4, and 59–5, bioavailability studies in rats reveal a 44-fold, 55-fold, and 62-fold increase in mean AUC, respectively, compared to the physical mixture. This suggests that the presence of some residual crystals after processing can be acceptable and will not change the properties of the ASD over time.

The ever-growing use of inorganic nanoparticles (NPs) in biomedicine provides an exciting approach to develop novel imaging and drug delivery systems, owing to the ease with which these NPs can be functionalized to cater to various applications. In cancer therapeutics, nanomedicine generally relies on the enhanced permeability and retention (EPR) effect observed in tumour vasculature to deliver anti-cancer drugs across the endothelium. However, such a phenomenon is dependent on the tumour microenvironment and is not consistently observed in all tumour types, thereby limiting drug transport to the tumour site. On the other hand, there is a rise in utilizing inorganic NPs to intentionally induce endothelial leakiness, creating a window of opportunity to control drug delivery across the endothelium. While this active targeting approach creates a similar phenomenon compared to the EPR effect arising from tumour tissues, its drug delivery applications extend beyond cancer therapeutics and into other vascular-related diseases. In this review, we summarize the current findings of the EPR effect and assess its limitations in the context of anti-cancer drug delivery systems. While the EPR effect offers a possible route for drug passage, we further explore alternative uses of NPs to create controllable endothelial leakiness within short exposures, a phenomenon we coined as nanomaterial-induced endothelial leakiness (NanoEL). Furthermore, we discuss the main mechanistic features of the NanoEL effect that make it unique from conventionally established endothelial leakiness in homeostatic and pathologic conditions, as well as examine its potential applicability in vascular-related diseases, particularly cancer. Therefore, this new paradigm changes the way inorganic NPs are currently being used for biomedical applications.