A subset of cancer stem cells termed 'side population' (SP) cells has been identified in several types of solid tumor and is known to be responsible for the failure of chemotherapy and for cancer relapse. In the present study, the oral squamous cell carcinoma (OSCC) cell line SCC‑55 was used for analysis of the SP cells based on Hoechst 33342 exclusion, via the ATP‑binding cassette (ABC) transporter, with and without verapamil using fluorescence activated cell sorting. The results demonstrated that the presence of SP cells in the SCC‑55 cell line was 2.8%, which was reduced to 0.6% in the presence of verapamil, an inhibitor of the ABC transporter. In addition, following exposure to the chemotherapeutic drug 5‑fluorouracil, a high survival rate was observed in the SP cells due to overexpression of the ABCG2 and B‑cell lymphoma 2 proteins. In addition, overexpression of stem cell surface markers, including CD44 and CD147 was observed in the SP cells. Therefore, these findings suggested that OSCC contains SP cells, which share certain characteristics with stem cells. The coexpression of ABC transporters and stem cell surface markers in SP cells may be associated with resistance to chemotherapeutic agents and also supports a role for these cells in tumor recurrence, metastasis and invasion.
This work could help to better understand the solvent effects on crystal habits and aspect ratio changes at the molecular level, which provide some guidance for solvent selection in industrial crystallization processes. With the catechol crystal habits acquired using both experimental and simulation methods in isopropanol, methyl acetate and ethyl acetate, solvent effects on crystal morphology were explored based on the modified attachment energy model. Firstly, morphologically dominant crystal faces were obtained with the predicted crystal habit in vacuum. Then, modified attachment energies were calculated by the molecular dynamics simulation to modify the crystal shapes in a real solvent environment, and the simulation results were in agreement with the experimental ones. Meanwhile, the surface properties such as roughness and the diffusion coefficient were introduced to analyze the solvent adsorption behaviors and the radial distribution function curves were generated to distinguish diverse types of interactions like hydrogen bonds and van der Waals forces. Results show that the catechol crystal habits were affected by the combination of the attachment energy, surface structures and molecular interaction types. Moreover, the changing aspect ratios of catechol crystals are closely related to the existence of hydrogen bonds which contribute to growth inhibition on specific faces.
In industrial crystallization, spherical crystals have gained increasing interest due to their excellent physicochemical properties, such as high bulk density, flowability, stability, etc. However, their formation mechanism is still not well understood and is often oversimplified. In this work, spherical amoxicillin sodium crystals were obtained via a spherulitic growth strategy. It was found that agitation immediately after the addition of crystal seeds was critical for inducing radial noncrystallographic branching and spherulite formation of amoxicillin sodium. Without agitation during the aging period after seed addition, only discrete rodshaped crystals were obtained. The formation mechanism of amoxicillin sodium spherulites was studied using process analytical technology (PAT) tools, including focused beam reflectance measurement (FBRM) and particle video microscope (PVM). The result was indicative of a three-step morphological evolution process: formation of polycrystalline agglomerates, noncrystallographic branching, and spherulite growth. During this process, agitation immediately after seed addition could help to solute diffusion and induce the agglomeration of small crystals that result from secondary nucleation. The polycrystalline agglomerates serve as the cores for further noncrystallographic branching and growth. On this basis, a new spherulitic growth strategy was proposed by the large addition of crystal seeds as the growth substrates of new branching and spherulite growth. High agitation rates during the aging period can increase the mass ratio of spherulites, and high initial supersaturation can promote branching. Compared with the discrete rod-shaped crystals, spherulites self-regulate the final size greatly up to three times and have a higher bulk density as well as much lower hygroscopicity.
Amoxicillin sodium heterosolvates, including SM-M (methanol–methyl acetate solvate), SE-M (ethanol–methyl acetate solvate), and SM-E (methanol–ethyl acetate solvate), were obtained for the first time in this work. The single crystal of...
Cocrystal
engineering is gaining interest across various disciplines
since it can effectively tune the properties of solid substances via
noncovalent synthesis by introducing new components into the lattice.
Mechanochemistry is without a doubt the most valuable tool for the
research of cocrystals, which combines the pursuit of efficient and
sustainable process pathways with the exploration of supramolecular
synthons that cannot be discovered using solution methods. In this
review, concerning the significance of the mechanochemical synthesis
of cocrystals, we begin by outlining the strategies for mechanochemical
preparation of cocrystals. We then elaborate on the theoretical mechanisms
of the mechanochemically induced formation of cocrystals and their
polymorphs. On this foundation, several cross-fields in which mechanochemistry
enhances the application value of cocrystal engineering are shown
to overcome existing limitations, which are difficult or impossible
to access using conventional solution methods. More importantly, we
demonstrate that the introduction of new methods, such as cultivating
single crystals from melt microdroplets, and new techniques, such
as microelectron diffraction (Micro-ED), has harmoniously united the
fields of cocrystal engineering and mechanochemistry. Finally, a brief
conclusion and outlook are presented, including current challenges
and future opportunities for the cooperation of mechanochemistry and
cocrystal engineering.
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