Inhomogeneities in PNIPAM Aqueous Solutions: The Inside View by Spin Probe EPR Spectroscopy

Coil to globule transition in poly(N-isopropylacrylamide) aqueous solutions was studied using spin probe continuous-wave electronic paramagnetic resonance (CW EPR) spectroscopy with an amphiphilic TEMPO radical as a guest molecule. Using Cu(II) ions as the “quencher” for fast-moving radicals in the liquid phase allowed obtaining the individual spectra of TEMPO radicals in polymer globule and observing inhomogeneities in solutions before globule collapsing. EPR spectra simulations confirm the formation of molten globules at the first step with further collapsing and water molecules coming out of the globule, making it denser.

Cellulose Nanofibers/Polycarbonate Nanocomposite

In this study, cellulose nanofiber (CNF) was prepared from carrot residues and further surface modification was carried out using suspension polymerization. Subsequently, these CNFs were added to polycarbonate (PC) to prepare a series CNF reinforced nanocomposites. TEM results show that the average diameter of the fiber after 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) radical oxidation is 4.46 nm, and the average diameter of the TEMPO oxidized nanofiber modified by suspension polymerization is 7.65 nm, which confirms that the carrot fiber has been successfully prepared into nanoscale. The results of FT-IR analysis show that the lignin and impurities on carrot fibers can be removed effectively after alkali treatment. In addition, the absorption peak of the functional group analyzed by FT-IR also confirmed that the TEMPO radical oxidation and suspension polymerization method were successfully carried out. Contact angle analysis results show that the contact angle of the CNF modified by suspension polymerization method was increased, indicating that the hydrophobicity of the fiber has been significantly improved. Moreover, this will lead to the better compatibility between CNF and PC matrix. Mechanical property analysis also shows that the surface modified CNF has a stronger reinforcing effect on PC than the unmodified one. Furthermore, the results show that the dispersion of CNF in the matrix of nanocomposite prepared by dilution of masterbatch was better than that of the one prepared by directly adding of CNFs. The better dispersion of CNFs in the PC matrix led to the better mechanical properties. The increment of tensile strength of the nanocomposite prepared by dilution of masterbatch can reach to 21.75%. In the analysis of transparency, the transmittance of modified CNF containing nanocomposite was larger than that of unmodified CNF containing one. The transmittance of the nanocomposites containing modified CNFs was larger than 70%, which was close to that of pure PC.

Pseudo-Tetrahedral vs Pseudo-Octahedral ErIII Single Molecule Magnets and the 'Disruptive' Role of Coordinated TEMPO Radicals

Erbium(III) complexes are the most interesting candidates for high-performance single molecule magnets (SMMs) just after dysprosium(III). Herein, we thoroughly explore the underrepresented class of neutral pseudo-tetrahedral erbium(III) SMMs and demonstrate their exceptional slow magnetization dynamics controlled by the Raman relaxation mechanism and the molecular magnetic memory effect in the form of a waist-restricted magnetic hysteresis loop. The influence of the coordinated TEMPO radical on the slow magnetization relaxation performance is also demonstrated and discussed.<br>

Pseudo-Tetrahedral vs Pseudo-Octahedral ErIII Single Molecule Magnets and the 'Disruptive' Role of Coordinated TEMPO Radicals

Erbium(III) complexes are the most interesting candidates for high-performance single molecule magnets (SMMs) just after dysprosium(III). Herein, we thoroughly explore the underrepresented class of neutral pseudo-tetrahedral erbium(III) SMMs and demonstrate their exceptional slow magnetization dynamics controlled by the Raman relaxation mechanism and the molecular magnetic memory effect in the form of a waist-restricted magnetic hysteresis loop. The influence of the coordinated TEMPO radical on the slow magnetization relaxation performance is also demonstrated and discussed.<br>

Hemostatic Dressings Made of Oxidized Bacterial Nanocellulose Membranes

Surgicel® (regenerated oxidized cellulose) is a bio-absorbable hemostatic material widely applied to prevent surgery-derived adhesions. Some critical issues have been reported associated with this biomaterial, which we aimed to overcome by producing bacterial nanocellulose (BNC) membranes with hemostatic activity, through electrochemical oxidation using the tetramethylpiperidine-1-oxyl (TEMPO) radical. Samples were characterized by FTIR, NMR, SEM, XRD and their degree of polymerization. The oxidation degree was evaluated by titration of the carboxyl groups and the hemostatic behavior by whole-blood-clotting assays. In vitro and in vivo biodegradability of oxidized BNC membranes were evaluated and compared with that of Surgicel®. The oxidation degree increased from 4% to 7% and up to 15%, corresponding to an applied charge of 400, 700 and 1200 Coulombs, respectively. The oxidized BNC preserved the crystallinity and the 3D nano-fibrillar network, and demonstrated hemostatic activity, although not as effective as that of Surgicel®. In vivo assays demonstrated that the oxidized membranes did not induce an inflammatory response, revealing a good biocompatibility. However, non-degraded oxidized BNC was still detected at the implantation site after 56 days.

Newly Developed Self-Assembling Antioxidants as Potential Therapeutics for the Cancers

Elevated reactive oxygen species (ROS) have been implicated as significant for cancer survival by functioning as oncogene activators and secondary messengers. Hence, the attenuation of ROS-signaling pathways in cancer by antioxidants seems a suitable therapeutic regime for targeting cancers. Low molecular weight (LMW) antioxidants such as 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO), although they are catalytically effective in vitro, exerts off-target effects in vivo due to their size, thus, limiting their clinical use. Here, we discuss the superior impacts of our TEMPO radical-conjugated self-assembling antioxidant nanoparticle (RNP) compared to the LMW counterpart in terms of pharmacokinetics, therapeutic effect, and adverse effects in various cancer models.

B-H and O-H bonds activation via a single electron transfer of frustrated radical pairs

The rare examples of B-H bond activation in frustrated radical pairs regime have been observed by treatment of TEMPO radical with Piers’ borane HB(C6F5)2 or bis-borane, respectively. The resulting concomitant...