Amine-decorated nanocrystalline cellulose surfaces: Synthesis, characterization, and surface properties

In this present work, terminal amino-functionalized nanocrystalline cellulose derivatives were prepared using a simple two-step protecting group-free protocol under aqueous reaction conditions at room temperature. Carboxylate groups were first introduced onto the surface of nanocrystalline cellulose (NCC) via a TEMPO-mediated oxidation. Then, reaction of surface-carboxylated NCC with bifunctional amines of small alkyl chain length by EDC/NHS-mediated coupling furnished the desired aminated NCC via an amide linkage. Surface covalent functionalization was confirmed by Fourier transform infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy. Size, surface charge, morphology, and thermal properties were obtained by various techniques. STEM images revealed no change in structure and morphology of the materials after TEMPO-mediated oxidation but a slight agglomeration was observed after surface covalent functionalization with diamines. While amide linkage confers stability, terminal primary amine groups on the surface of NCC represent a versatile reactive functional group for bioconjugation with other biomolecules for potential biomedical applications. \ua9 2013 Published by NRC Research Press.Peer reviewed: YesNRC publication: Ye

Structure of poly(N-isopropylacrylamide) brushes and steric stability of their grafted cellulose nanocrystal dispersions

Thermo-responsive poly (N-isopropylacrylamide) (poly(NIPAAm)) brushes were grafted from the surface of cellulose nanocrystals (CNC) via living radical polymerization (LRP) using different initiator and monomer concentrations. The dry film thickness of the poly(NIPAAm) layer around CNC was calculated based on Scanning Electron Microscopy (SEM) and dynamic light scattering (DLS) measurements. The wet film thicknesses of grafted poly(NIPAAm) brushes in water were calculated to be 15 and 9. nm for NIPAAm-CNC-1 and NIPAAm-CNC-2, respectively. Grafted chain densities and wet film thicknesses at below and above the critical temperature (T= 34. \ub0C) of polyNIPAAm were calculated by applying mean-field analytical theory. The non-ionic poly(NIPAAm) brushes screened the surface charges of CNC particles, leading to a significant decrease in the absolute zeta potential values for the poly(NIPAAm) grafted CNCs compared to the unmodified and initiator modified CNC samples. Nevertheless, the colloidal stability of poly(NIPAAm) grafted CNC particles were still maintained by steric stabilization below the critical temperature On the other side, hydrophobic attractions among poly(NIPAAm) grafted CNC rods above 34. \ub0C lead to coagulation and phase separation. While both poly(NIPAAm) grafted CNC samples showed thermo-responsive behavior, the reversibility of this temperature triggered property was dependent on grafting density. \ua9 2014 Elsevier Inc.Peer reviewed: YesNRC publication: Ye

Cellulose nanocrystal cationic derivative induces NLRP3 inflammasome-dependent IL-1\u3b2 secretion associated with mitochondrial ROS production

Crystalline cellulose nanocrystals (CNCs) have emerged as novel materials for a wide variety of important applications such as nanofillers, nanocomposites, surface coatings, regenerative medicine and potential drug delivery. CNCs have a needle-like structure with sizes in the range of 100-200. nm long and 5-20. nm wide and a mean aspect ratio 10-100. Despite the great potential applicability of CNCs, very little is known about their potential immunogenicity. Needle-like materials have been known to evoke an immune response in particular to activate the (NOD-. like receptor, pyrin domain-containing 3)-inflammasome/IL-1\u3b2 (Interleukin 1\u3b2) pathway. In this study we evaluated the capacity of unmodified CNC and its cationic derivatives CNC-AEM (aminoethylmethacrylate)1, CNC-AEM2, CNC-AEMA(aminoethylmethacrylamide)1 and CNC-AEMA2 to stimulate NLRP3-inflammasome/IL-1\u3b2 pathway and enhance the production of mitochondrial reactive oxygen species (ROS). Mouse macrophage cell line (J774A.1) was stimulated for 24. h with 50. \u3bcg/mL with unmodified CNC and its cationic derivatives. Alternatively, J774A1 or PBMCs (peripheral blood mononuclear cells) were stimulated with CNC-AEMA2 in presence or absence of LPS (lipopolysaccharide). IL-1\u3b2 secretion was analyzed by ELISA, mitochondrial function by JC-1 staining and ATP content. Intracellular and mitochondrial reactive oxygen species (ROS) were assessed by DCF-DA (2',7'-dichlorodihydrofluorescein diacetate) and MitoSOX, respectively. Mitochondrial ROS and extracellular ATP were significantly increased in cells treated with CNC-AEMA2, which correlates with the strongest effects on IL-1\u3b2 secretion in non-primed cells. CNC-AEMA2 also induced IL-1\u3b2secretion in LPS-primed and non-primed PBMCs. Our data suggest that the increases in mitochondrial ROS and ATP release induced by CNC-AEMA2 may be associated with its capability to evoke immune response. We demonstrate the first evidence that newly synthesized cationic cellulose nanocrystal derivative, CNC-AEMA2, has immunogenic properties, which may lead to the development of a potential non-toxic and safe nanomaterial to be used as a novel adjuvant for vaccines.Peer reviewed: YesNRC publication: Ye