Exploring Aromaticity Effects on Electronic Transport in Cyclo[n]carbon Single-Molecule Junctions.

Cyclo[n]carbon (Cn) is one member of the all-carbon allotrope family with potential applications in next-generation electronic devices. By employing first-principles quantum transport calculations, we have investigated the electronic transport properties of single-molecule junctions of Cn, with n = 14, 16, 18, and 20, connected to two bulk gold electrodes, uncovering notable distinctions arising from the varying aromaticities. For the doubly aromatic C14 and C18 molecules, slightly deformed complexes at the singlet state arise after bonding with one Au atom at each side; in contrast, the reduced energy gaps between the highest occupied and the lowest unoccupied molecular orbitals due to the orbital reordering observed in the doubly anti-aromatic C16 and C20 molecules lead to heavily deformed asymmetric complexes at the triplet state. Consequently, spin-unpolarized transmission functions are obtained for the Au-C14/18-Au junctions, while spin-polarized transmission appears in the Au-C16/20-Au junctions. Furthermore, the asymmetric in-plane π-type hybrid molecular orbitals of the Au-C16/20-Au junctions contribute to two broad but low transmission peaks far away from the Fermi level (Ef), while the out-of-plane π-type hybrid molecular orbitals dominate two sharp transmission peaks that are adjacent to Ef, thus resulting in much lower transmission coefficients at Ef compared to those of the Au-C14/18-Au junctions. Our findings are helpful for the design and application of future cyclo[n]carbon-based molecular electronic devices.

Tuning Surface Organic Structures by Small Gas Molecules through Catassembly and Coassembly.

The field of molecular assembly has seen remarkable advancements across various domains, such as materials science, nanotechnology, and biomedicine. Small gas molecules serve as pivotal modulators, capable of altering the architecture of assemblies via tuning a spectrum of intermolecular forces including hydrogen bonding, dipole-dipole interactions, and metal coordination. Surface techniques, notably scanning tunneling microscopy and atomic force microscopy, have proven instrumental in dissecting the structural metamorphosis and characteristic features of these assemblies at an unparalleled single-molecule resolution. Recent research has spotlighted two innovative approaches for modulating surface molecular assemblies with the aid of small gas molecules: "catassembly" and "coassembly". This Perspective delves into these methodologies through the lens of varying molecular interaction types. The strategies discussed here for regulating molecular assembly structures using small gas molecules can aid in understanding various complex assembly processes and structures and provide guidance for the further fabrication of complex surface structures.

Design and optimization of gastro-floating sustained-release tablet of pregabalin: In vitro and in vivo evaluation.

Pregabalin is a promising drug for the treatment of neuropathic pain, a chronic disease affecting a large population needing long-term treatment. However, due to its short half-life, the commercial tablet has to be administered 2-3 times per day, with inconvenience for patient and fluctuations of plasma concentration. In this study, a gastro-floating drug delivery system of pregabalin was developed to prolong the gastric retention of drugs absorbed or act in stomach or upper gastrointestinal tract. First of all, it was proved that the drug was mainly absorbed in stomach and upper gastrointestinal tract. The final formulation was optimized in consideration of buoyancy and drug release profile. The gastro-floating tablet was prepared with hydroxypropyl methylcellulose (HPMC) as sustained-release matrix, lipophilic cetyl alcohol as floating-assistance agent and other excipients to achieve satisfying buoyancy and sustained release performance with mechanisms of diffusion and matrix erosion. Food exhibited significant effect on the pharmacokinetics of gastro-floating tablet and conventional capsule. Compared with conventional capsules, the relative bioavailability of gastro-floating tablet in fasted conditions or in fed conditions was only 62.47 ±â€¯10.80% and 100.98 ±â€¯17.25% respectively, even though the gastro-floating tablet obtained decreased Cmax and prolonged Tmax in fasted and fed conditions. Besides, good in vivo-in vitro correlation of the gastro-floating tablet was established. In summary, a gastro-floating tablet of pregabalin exhibiting desired buoyancy and release profiles was designed, and the tablet expressed significantly sustained-release behavior in fed conditions with good in vivo-in vitro correlation. The designed gastro-floating system is a promising choice for the patients to relieve neuropathic pain.