Requirements in structure for chiral recognition of chitosan derivatives

In order to investigate the influence of a minor variation in structure of N-acyl chitosan derivatives on enantioseparation, chiral selectors (CSs) of chitosan 3,6-bis(phenylcarbamate)-2-(phenylacetamide)s and chitosan 3,6-bis(phenylcarbamate)-2-(cyclohexylacetamide)s were synthesized. The corresponding chiral stationary phases (N-PhAc CSPs and N-cHeAc CSPs) were also prepared, respectively, with the two series of CSs. Enantioseparation results revealed that the N-PhAc CSPs were better than the N-cHeAc ones in enantioseparation. Thus, benzyl group (Bn) at C₂ should be more preferable to enantioseparation than cyclohexylmethyl (cyclohexyl-CH₂-) at the same position. Because N-PhAc CSPs exhibited higher enantioseparation capability than chitosan 3,6-bis(phenylcarbamate)-2-(benzamide) based CSPs (N-Bz CSPs), the Bn should also be more beneficial to enantioseparation than phenyl group (Ph) at C₂ in N-Bz CSPs. In addition, it was found that, the cyclohexyl group at C₂ in chitosan 3,6-bis(phenylcarbamate)-2-(cyclohexylformamide) CSPs was better than cyclohexyl-CH₂- in N-cHeAc CSPs to enantioseparation. In a word, a minor variation at C₂ of chitosan derivatives significantly affected enantioseparation. After the prepared CSPs were stood for six months, their enantioseparation capabilities were changed obviously, and the changes were probably related to nature, position and number of a substituent on Ph connected to carbamates at C₃ and C₆ of the CSs.

Spray freeze dried niclosamide nanocrystals embedded dry powder for high dose pulmonary delivery

Based on the drug repositioning strategy, niclosamide (NCL) has shown potential applications for treating COVID-19. However, the development of new formulations for effective NCL delivery is still challenging. Herein, NCL-embedded dry powder for inhalation (NeDPI) was fabricated by a novel spray freeze drying technology. The addition of Tween-80 together with 1,2-Distearoyl-sn-glycero-3-phosphocholine showed the synergistic effects on improving both the dispersibility of primary NCL nanocrystals suspended in the feed liquid and the spherical structure integrity of the spray freeze dried (SFD) microparticle. The SFD microparticle size, morphology, crystal properties, flowability and aerosol performance were systematically investigated by regulating the feed liquid composition and freezing temperature. The addition of leucine as the aerosol enhancer promoted the microparticle sphericity with greatly improved flowability. The optimal sample (SF_{- 80}D-N₂₀L₂D₂T₁) showed the highest fine particle fraction of ∼47.83%, equivalently over 3.8 mg NCL that could reach the deep lung when inhaling 10 mg dry powders.

Influence of pyrolysis atmosphere and temperature co-regulation on the sorption of tetracycline onto biochar: structure-performance relationship variation

Presently, as the prevalent pyrolysis atmospheres, N₂ is widely used, while air-limitation and CO₂ are rarely considered, to produce biochar to adsorb tetracycline. This study thus used N₂, CO₂, and air-limitation to produce various biochars at 300 ∼ 750 °C, and explored their structure-performance relationship for tetracycline sorption. The maximum sorption capacities of biochars produced in CO₂ and air-limitation were 55.36 mg/g and 71.11 mg/g (at 750 °C), respectively, being 2.34 and 3.01 times that of biochars produced in N₂ (23.60 mg/g at 750 °C). Interestingly, except for high pore volume and specific surface area supported pore filling and sites providing effect, ash (containing metal cations, P-O, and S=O) induced complexing effect was the primary mechanism for tetracycline sorption, rather than hydrophobic effect, π-π interaction, and hydrogen bond caused by C composition. This study provides important information about adjusting the pyrolysis atmosphere to improve the sorption performance of biochar toward tetracycline.

Dendritic porous silica nanoparticles with high-curvature structures for a dual-mode DNA sensor based on fluorometer and person glucose meter

A dual-mode DNA sensor was constructed to detect nucleic acid sensitively and selectively. Based on dendritic porous silica nanoparticles (DPSNs) and hybridization chain reaction (HCR) amplification strategy, the fabricated DNA sensor showed good sensitivity with low detection limits down to 2.18 pM and 4.02 pM by fluorescence (excited at 488 nm and emitted at 508 nm) and personal glucose meter (PGM) assays, respectively. This dual-mode detection of DNA offered superior reliability and accuracy and could meet the requirements of different testing environments, including laboratory confirmation and portable detection. Moreover, the impact of nanoparticles morphology on detection performance was also discussed. Due to the center-radial pores, DPSNs had high curvature morphology, which improved the coverage capacity, footprint, and deflection angle of probes. This work fabricated a dual-mode DNA sensor and revealed the relationship between morphology and detection performance, which brought new insights in novel biosensor development.

Boosting oxygen reduction activity of spinel CoFe2O4 by strong interaction with hierarchical nitrogen-doped carbon nanocages

The unique hierarchical nitrogen-doped carbon nanocages (hNCNC) are used as a new support to homogeneously immobilize spinel CoFe₂O₄ nanoparticles by a facile solvothermal method. The so-constructed hierarchical CoFe₂O₄/hNCNC catalyst exhibits a high oxygen reduction activity with an onset potential of 0.966V and half-wave potential of 0.819V versus reversible hydrogen electrode, far superior to the corresponding 0.846 and 0.742V for its counterpart of CoFe₂O₄/hCNC with undoped hierarchical carbon nanocages (hCNC) as the support, which locates at the top level for spinel-based catalysts to date. Consequently, the CoFe₂O₄/hNCNC displays the superior performance to the CoFe₂O₄/hCNC, when used as the cathode catalysts in the home-made Al-air batteries. X-ray photoelectron spectroscopy characterizations reveal the more charge transfer from CoFe₂O₄ to hNCNC than to hCNC, indicating the stronger interaction between CoFe₂O₄ and hNCNC due to the nitrogen participation. The enhanced interaction and hierarchical morphology favor the high dispersion and modification of electronic states for the active species as well as the mass transport during the oxygen reduction process, which plays a significant role in boosting the electrocatalytic performances. In addition, we noticed the high sensitivity of O 1s spectrum to the particle size and chemical environment for spinel oxides, which is used as an indicator to understand the evolution of ORR activities for all the CoFe₂O₄-related contrast catalysts. Accordingly, the well-defined structure-performance relationship is demonstrated by the combination of experimental characterizations with theoretical calculations. This study provides a promising strategy to develop efficient, inexpensive and durable oxygen reduction electrocatalysts by tuning the interaction between spinel metal oxides and the carbon-based supports.