Synthesis and catalytic performance of wood cellulose nanofibers grafted with polylactic acid in rare-earth complexes based on tetrazole carboxylic acids.

Stannous octanoate [Sn(Oct)2] and 4-dimethylamino pyridine (DMAP) were used to catalyze the synthesis of amphiphilic cellulose-based graft copolymers, but the acute toxicity of tin ions and DMAP prompts the need for the application of less harmful catalysts. Herein, green catalyst complexes 1-3 [M(H0.5L)2(H2O)5]·2(H2O) (M = Sm, 1; M = Nd, 2; M = Eu, 3; H2L = 4-(3-(tetrazol-5-yl)pyridin-5-yl)benzoic acid) were synthesized, and their properties were systematically investigated. Single-crystal X-ray diffraction showed that the complexes possessed a zero-dimensional structure, while the thermogravimetry and scanning electron microscopy results confirmed their stability after heating at 110 °C for 10 h. Using complexes 1-3 and DMAP as the catalysts, CNFs were grafted with l-lactide via homogeneous ring-opening polymerization to form wood cellulose nanofibers grafted with l-lactide (WGLAs), and the effects of the ratio of wood cellulose nanofibers (WCNFs) to l-lactide ([AGU]/[LA]) and catalyst dosage were studied. The polymerization followed the coordination-insertion mechanism. Under comparable reaction conditions, the grafting ratio of WGLA-1 reached 84.7 %, and the grafting ratio of complex 1 was found to be higher than those achieved using DMAP. WGLAs demonstrated good thermal stability without cytotoxicity, and the residual catalysts in the WGLAs exhibited fluorescence characteristics. Overall, amphiphilic cellulose-based materials with fluorescence emission offered a promising modification strategy to prepare high-performance polymer composites for agriculture and biomedical application.

Wood Cellulose Nanofibers Grafted with Poly(ε-caprolactone) Catalyzed by ZnEu-MOF for Functionalization and Surface Modification of PCL Films.

Renewable cellulose nanofiber (CNF)-reinforced biodegradable polymers (such as polycaprolactone (PCL)) are used in agriculture, food packaging, and sustained drug release. However, the interfacial incompatibility between hydrophilic CNFs and hydrophobic PCL has limited further application as high-performance biomaterials. In this work, using a novel ZnEu-MOF as the catalyst, graft copolymers (GCL) with CNFs were grafted with poly(ε-caprolactone) (ε-CL) via homogeneous ring-opening polymerization (ROP), and used as strengthening/toughening nanofillers for PCL to fabricate light composite films (LCFs). The results showed that the ZnEu-MOF ([ZnEu(L)2(HL)(H2O)0.39(CH3OH)0.61]·H2O, H2L is 5-(1H-imidazol-1-yl)-1,3-benzenedicarboxylic acids) was an efficient catalyst, with low toxicity, good stability, and fluorescence emissions, and the GCL could efficiently promote the dispersion of CNFs and improve the compatibility of the CNFs and PCL. Due to the synergistic effect of the ZnEu-MOF and CNFs, considerable improvements in the mechanical properties and high-intensity fluorescence were obtained in the LCFs. The 4 wt% GCL provided the LCF with the highest strength and elastic modulus, which increased by 247.75% and 109.94% compared to CNF/PCL, respectively, showing the best elongation at break of 917%, which was 33-fold higher than CNF/PCL. Therefore, the ZnEu-MOF represented a novel bifunctional material for ROP reactions and offered a promising modification strategy for preparing high-performance polymer composites for agriculture and biomedical applications.

Porous and Stable Zn-Series Metal-Organic Frameworks as Efficient Catalysts for Grafting Wood Nanofibers with Polycaprolactone via a Copolymerization Approach.

A hydrothermal method was used to synthesize two highly stable Zn(II) metal-organic frameworks (MOFs), namely, [Zn2(L)2(HIPA)]n (1) and [Zn9(L)6(BTEC)3(H2O)4·6H2O]n (2) (HL = 3-amino-1H-1,2,4-triazole, H2HIPA = 5-hydroxyisophthalic acid, H4BTEC = benzene-1,2,4,5-tetracarboxylic acid). The physicochemical properties of 1 and 2 were characterized using a range of analytical techniques. The scanning electron microscopy images confirmed the stability of the MOFs under heating at 120 °C for 12 h. Following their preparation, the two MOFs were used as catalysts in the grafting of poly(ε-caprolactone) on wood nanofibers (WNFs) by means of a homogeneous ring-opening polymerization protocol in an ionic liquid. The grafting ratio achieved using catalyst 1 was higher than that achieved for catalyst 2, wherein a maximum of 92.43% was obtained using the former. Under comparable reaction conditions, the grafting ratio of 1 was found to be significantly higher than those achieved using 4-dimethylamino pyridine, Sn(Oct)2, and UiO-67 catalysts. In addition, fluorescence emission was detected from the residual catalysts present in the products. The calculated electrostatic potentials and average local ionization energies indicated that the grafting of ε-caprolactone on the WNFs follows a "coordination-insertion" mechanism. Overall, these two new and efficient MOF catalysts have the potential to replace highly toxic traditional catalysts in polymerization reactions. The grafted cellulose material with fluorescence emission may also be suitable for use in biomedical applications.

Synthesis and catalytic performance of banana cellulose nanofibres grafted with poly(ε-caprolactone) in a novel two-dimensional zinc(II) metal-organic framework.

In this study, banana cellulose nanofibres (BNCFs) were prepared using waste banana stems. A novel two-dimensional (2D) Zn-MOF was synthesized using 5-(1-hydro-imidazolyl) isophthalic acid as the ligand. The results of the X-ray diffraction, thermogravimetry, and scanning electron microscopy analyses confirmed the stability of Zn-MOF. Thus, Zn-MOF was used to catalyze BNCFs grafted with poly(ε-caprolactone) (ε-CL) (BGCL) by homogeneous ring-opening polymerization in ionic liquid. The grafting ratio of the BGCL prepared by Zn-MOF reached 84.12 %, which was 10.03% higher than that catalyzed by 4-dimethylamino pyridine which was the state-of-the-art catalyst for this reaction. The banana cellulose nanofibres grafted with ε-CL reactions followed the coordination-insertion mechanism, which was confirmed by the theoretical calculations using the Materials Studio software. The cytotoxicity results indicated that BGCL was not only non-toxic to Hela cells but also promoted Hela cell growth within a certain concentration range. Therefore, this study demonstrated the promising potential of BGCL for biomedical applications, and the high efficiency, non-toxicity, and stability of Zn-MOF as the catalyst. Further, this will provide a theoretical basis for the application of MOFs as catalysts in polymerization reactions.

Establishment and Application of Multiplex PCR for Simultaneously Detecting Escherichia coli, Salmonella, Klebsiella pneumoniae, and Staphylococcus aureus in Minks.

To establish a multiplex PCR for simultaneous detection of Escherichia coli (E. coli), Salmonella, Klebsiella pneumoniae (K. pneumoniae), and Staphylococcus aureus (S. aureus), four pairs of specific primers were designed according to the conservative regions of phoA gene for E. coli, invA gene for Salmonella, khe gene for K. pneumoniae, nuc gene for S. aureus. The quadruple PCR system was established through optimization of multiplex PCR and detection of specificity, sensitivity, and stability. The results showed that target gene bands of E. coli (622 bp), Salmonella (801 bp), K. pneumoniae (303 bp), and S. aureus (464 bp) could be amplified by this method specifically and simultaneously from the same sample containing the four pathogens, with a detection sensitivity of 100 pg/µL. Meanwhile, no bands of common clinical bacteria, including Clostridium perfringens, Pseudomonas aeruginosa, Pasteurella multocida, Streptococcus pneumoniae, Streptococcus pneumoniae, Proteus mirabilis, Staphylococcus sciuri, Staphylococcus pseudintermedius, Acinetobacter baumannii, Enterococcus faecalis, and Bacillus subtilis were amplified. In addition, 380 tissue samples were detected by multiplex and single PCR established in current study, respectively. Among the 368 carcass samples, positive detection rates of E. coli, K. pneumoniae, Salmonella, and S. aureus were 33.7, 12.0, 10.6, and 13.9%. Among the 12 visceral tissue samples, positive detection rates of E. coli, K. pneumoniae, Salmonella, and S. aureus were 41.7, 25.0, 16.7, and 8.3%, respectively. Positive detection rates of multiplex PCR were consistent with that of single PCR. Compared with single PCR, the multiplex PCR method had the advantages of time-saving, high specificity and high sensitivity. The results showed that the minks in these farms had mixed infection of these four pathogens, and the method established in this study could be applied to the rapid and accurate detection and identification of these four bacteria. In conclusion, the multiplex PCR method has stable detection results, good repeatability, and short detection time. It is suitable for the rapid and accurate detection of four kinds of bacteria above the carcass of fur animals, which could be suitable in microbial epidemiology investigation. It can provide a reliable technical reference for rapid clinical diagnosis and detection.

Metal-free oxidative isocyanides insertion with aromatic aldehydes to aroylated N-heterocycles.

A metal-free, mild and efficient protocol for the construction of aroylated N-heterocycles via radical cascade aroylation of phenyl or vinyl isocyanides with aromatic aldehydes has been developed. Both phenanthridine and isoquinoline derivatives are delivered quickly in moderate to good yields with high regioselectivity.