Co-milling of various carbamazepine (CBZ) polymorphic forms (form I, III and dihydate) with nicotinamide (NIC) was performed in this study to investigate the formation kinetics of carbamazepine−nicotinamide cocrystals (CBZ−NIC) and to evaluate their physical stability. Milling was carried out at room temperature using an oscillatory ball mill at a 1:1 molar ratio of CBZ and NIC for various times up to 60 min. A freshly prepared sample was used for each milling. In the stability study, the milled samples (4, 10, 15, and 30 min) were stored under four conditions (20 and 40 °C; 33 and 75%RH) for up to four weeks. Samples were analyzed by X-ray powder diffraction (XRPD) and differential scanning calorimetry. XRPD showed that all CBZ forms used in this study formed cocrystals when co-milled with NIC (characteristic XRPD peaks at 6.6, 8.9, 10.1, 20.4, and 26.5 °2θ). Cocrystal formation was qualitatively found to be fastest for CBZ dihydrate (CBZ DH, ∼1 min), followed by CBZ form I (∼6 min), and CBZ form III (∼15 min). Upon storage, cocrystals formed from CBZ DH were found to be physically stable under all conditions studied, regardless of a small amount of impurity. For the two anhydrous forms (CBZ I and III), the physical stability of the co-milled CBZ−NIC samples was dependent on the duration of milling, the relative humidity, and temperature of the storage conditions. Under “mild” storage conditions (i.e., 20 °C/33%RH), either partially or fully formed CBZ−NIC cocrystals were found to revert back to pure CBZ and NIC. Under “moderate” storage conditions (i.e., 20 °C/75%RH and 40 °C/33%RH), CBZ−NIC cocrystals reverting to pure CBZ and NIC would occur initially, followed by cocrystal formation with increasing storage time. On the other hand, “stress” storage conditions (i.e., 40 °C/75%RH) were found to be ideal for cocrystal formation and stability. Moisture has been found to favor cocrystallization. Water molecules appear to have a significant effect on the formation (water molecules from CBZ DH) and the stability (high humidity) of the CBZ−NIC cocrystal. The “purity” of the cocrystal samples (i.e., presence of CBZ and/or NIC seeds) can affect the physical stability of CBZ−NIC cocrystals prepared by mechanical activation.

Cellular blebbing, caused by local alterations in cell-surface tension, has been shown to increase the invasiveness of cancer cells. However, the regulatory mechanisms balancing cell-surface dynamics and bleb formation remain elusive. Here, we show that an acute reduction in cell volume activates clathrin-independent endocytosis. Hence, a decrease in surface tension is buffered by the internalization of the plasma membrane (PM) lipid bilayer. Membrane invagination and endocytosis are driven by the tension-mediated recruitment of the membrane sculpting and GTPase-activating protein GRAF1 (GTPase regulator associated with focal adhesion kinase-1) to the PM. Disruption of this regulation by depleting cells of GRAF1 or mutating key phosphatidylinositol-interacting amino acids in the protein results in increased cellular blebbing and promotes the 3D motility of cancer cells. Our data support a role for clathrin-independent endocytic machinery in balancing membrane tension, which clarifies the previously reported role of GRAF1 as a tumor suppressor.

Caveolae are bulb-shaped invaginations of the plasma membrane (PM) that undergo scission and fusion at the cell surface and are enriched in specific lipids. However, the influence of lipid composition on caveolae surface stability is not well described or understood. Accordingly, we inserted specific lipids into the cell PM via membrane fusion and studied their acute effects on caveolae dynamics. We demonstrate that sphingomyelin stabilizes caveolae to the cell surface, whereas cholesterol and glycosphingolipids drive caveolae scission from the PM. Although all three lipids accumulated specifically in caveolae, cholesterol and sphingomyelin were actively sequestered, whereas glycosphingolipids diffused freely. The ATPase EHD2 restricts lipid diffusion and counteracts lipid-induced scission. We propose that specific lipid accumulation in caveolae generates an intrinsically unstable domain prone to scission if not restrained by EHD2 at the caveolae neck. This work provides a mechanistic link between caveolae and their ability to sense the PM lipid composition.

Gelatine nanoparticles (GNPs) are biodegradable and biocompatible drug delivery systems with excellent clinical performances. A two-step desolvation is commonly used for their preparation, although this methodology has several shortcomings: lack of reproducibility, small scales and low yields. A straightforward and more consistent GNP preparation approach is presented here focusing on the development of a one-step desolvation with the use of a commercially available gelatine type. Controlled stirring conditions and ultrafiltration are used to achieve large-scale production of nanoparticles of up to 2.6 g per batch. Particle size distributions are conserved and comparable to those determined for two-step desolvation on small scale. Additionally, a range of cross-linking agents is examined for their effectiveness in stabilising GNPs as an alternative to glutaraldehyde. Glyceraldehyde demonstrated outstanding properties, which led to high colloidal stability. This approach optimises the manufacturing process and the scale-up of the production capacity, providing a clear potential for future applications.

Caveolae are small Ω-shaped invaginations of the plasma membrane that play important roles in mechanosensing, lipid homeostasis and signaling. Their typical morphology is characterized by a membrane funnel connecting a spherical bulb to the membrane. Membrane funnels (commonly known as necks and pores) are frequently observed as transient states during fusion and fission of membrane vesicles in cells. However, caveolae display atypical dynamics where the membrane funnel can be stabilized over an extended period of time, resulting in cell surface constrained caveolae. In addition, caveolae are also known to undergo flattening as well as short-range cycles of fission and fusion with the membrane, requiring that the membrane funnel closes or opens up, respectively. This mini-review considers the transition between these different states and highlights the role of the protein and lipid components that have been identified to control the balance between surface association and release of caveolae.