Biological Preparation of Chitosan-Loaded Silver Nanoparticles: Study of Methylene Blue Adsorption as Well as Antibacterial Properties under Light.

Human beings have made significant progress in the medical field since antibiotics were widely used. However, the consequences caused by antibiotics abuse have gradually shown their negative effects. Antibacterial photodynamic therapy (aPDT) has the ability to resist drug-resistant bacteria without antibiotics, and as it is increasingly recognized that nanoparticles can effectively solve the deficiency problem of singlet oxygen produced by photosensitizers, the application performance and scope of aPDT are gradually being expanded. In this study, we used a biological template method to reduce Ag+ to silver atoms in situ with bovine serum albumin (BSA) rich in various functional groups in a 50 °C water bath. The aggregation of nanomaterials was inhibited by the protein's multistage structure so that the formed nanomaterials have good dispersion and stability. It is unexpected that we used chitosan microspheres (CMs) loaded with silver nanoparticles (AgNPs) to adsorb methylene blue (MB), which is both a pollutant and photosensitive substance. The Langmuir adsorption isothermal curve was used to fit the adsorption capacity. The exceptional multi-bond angle chelating forceps of chitosan make it have a powerful physical adsorption capacity, and dehydrogenated functional groups of proteins with negative charge can also bond to positively charged MB to form a certain amount of ionic bonds. Compared with single bacteriostatic materials, the bacteriostatic capacity of the composite materials adsorbing MB under light was significantly improved. This composite material not only has a strong inhibitory effect on Gram-negative bacteria but also has a good inhibitory effect on the growth of Gram-positive bacteria poorly affected by conventional bacteriostatic agents. In conclusion, the CMs loaded with MB and AgNPs have some possible applications in the purification or treatment of wastewater in the future.

Copper nanocluster-based fluorescence enhanced determination of d-penicillamine.

Taking advantage of the compelling properties of d-penicillamine (d-PA) combined with copper, a method for the sensitive and selective determination of d-PA was established using copper nanocluster (Cu NC)-based fluorescence enhancement. d-PA molecules containing a thiol compound showed a strong tendency to combine with the surface of Cu NCs, causing the re-dispersion of nanoclusters and therefore fluorescence intensity was enhanced. Fluorescence enhancement efficiency of Cu NCs induced by d-PA was linear, with the d-PA concentration varying from 0.6-30 µg ml-1 (R2  = 0.9952) and with a detection limit of 0.54 µg ml-1 . d-PA content in human urine samples was detected with recoveries of 104.8-112.99%. Fluorescence-enhanced determination of d-PA using Cu NCs was established for the first time and this rapid, easy and sensitive method should attract much attention for this application.

Functionalized O6-Corona[6]arenes: Synthesis, Structure, and Fullerene Complexation Property.

The synthesis, structure, and fullerene complexation property of novel and functionalized On-corona[n]arenes were reported. Based on the fragment coupling strategy, ester-containing On-corona[n]arenes (n = 6, 8) were obtained readily starting from 1,4-hydroquinone and diethyl 2,5-difluoroterephthalate. Reduction of esters with LiAlH4 produced almost quantitatively hydroxymethylated On-corona[n]arenes, which underwent etherification with MeI to afford methoxymethyl-substituted On-corona[n]arenes (n = 6, 8) in good yields. The macrocycles adopt unique corona-type conformation with a large cylindroid cavity. They are strong macrocyclic host molecules to form 1:1 complexes with fullerenes C60 and C70 in toluene with an associate constant up to (1.59 ± 0.04) × 10(5) M(-1).

Selective Formylation of Azacalixpyridine Macrocycles and Their Transformation to Molecular Semicages.

The aromatic electrophilic formylation reaction of azacalix[2]arene[2]pyridine and azacalix[4]pyridine were systematically studied. By simply controlling the ratio of reactants and the reaction temperature, the Vilsmeier-Haack reaction selectively afforded mono-, di-, and tetra-formylated azacalix[2]arene[2]pyridines and azacalix[4]pyridines. The preferential and selective functionalization reactions of macrocycles were discussed in terms of their conformational structure and conjugation effect between aromatic subunits and bridging nitrogen atoms. All resulting functionalized azacalix[2]arene[2]pyridines and azacalix[4]pyridines adopted a 1,3-alternate conformation both in the crystalline state and in solution. Taking advantage of the close proximity of aldehyde groups in 1,3-alternate di- and tetra-formylated azacalixpyridine macrocycles, the McMurry reductive coupling reaction of carbonyls was accomplished to yield unique semicage molecules.