Functional Cellulose Beads: Preparation, Characterization, and Applications

Encapsulation of Either Hydrophilic or Hydrophobic Substances in Spongy Cellulose Particles

We have reported cellulose particles with a spongy structure that we prepared by the solvent releasing method (SRM) from cellulose droplets composed of cellulose, 1-butyl-3-methylimidazoliumchrolide ([Bmim]Cl), and N,N-dimethylformamide (DMF). The spongy structure collapsed as the medium evaporated, resulting in dense cellulose particles. In this study, we encapsulated the hydrophilic and hydrophobic fluorescent substances in these particles to investigate the use of such particles in potential applications that require encapsulating of substances (e.g., drug delivery). Wet cellulose particles retained their spongy structure in both hydrophobic and hydrophilic media. When the spongy cellulose particles were dispersed in a solution containing nonvolatile solutes, these solutes were driven into the cellulose particles as media evaporated. Subsequently, the cellulose particles collapsed and encapsulated the nonvolatile solutes. Regardless of whether the solute was hydrophilic or hydrophobic, the encapsulation efficiency exceeds 80%. The maximum loading reflected the saturated solubility of solute in solution that filled the cellulose beads. Moreover, the encapsulated solute was released by dispersing the cellulose beads in the solvent, and the rate of release of the encapsulated solute could be controlled by coating the cellulose beads with a conventional polymer.

Renewable hybrid nanocatalyst from magnetite and cellulose for treatment of textile effluents

A hybrid catalyst was prepared using cellulose nanofibrils and magnetite to degrade organic compounds. Cellulose nanofibrils were isolated by mechanical defibrillation producing a suspension used as a matrix for magnetite particles. The solution of nanofibrils and magnetite was dried and milled resulting in a catalyst with a 1:1 ratio of cellulose and magnetite that was chemically and physically characterized using light, scanning electron and transmission electron microscopies, specific surface area analysis, vibrating sample magnetometry, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, catalytic potential and degradation kinetics. Results showed good dispersion of the active phase, magnetite, in the mat of cellulosic nanofibrils. Leaching and re-use tests showed that catalytic activity was not lost over several cycles. The hybrid material produced was tested for degradation of methylene blue dye in Fenton-like reactions resulting in a potential catalyst for use in degradation of organic compounds.

Tailored Fabrication of Transferable and Hollow Weblike Titanium Dioxide Structures

The preparation of weblike titanium dioxide thin films by atomic layer deposition on cellulose biotemplates is reported. The method produces a TiO₂ web, which is flexible and transferable from the deposition substrate to that of the end application. Removal of the cellulose template by calcination converts the amorphous titania to crystalline anatase and gives the structure a hollow morphology. The TiO₂ webs are thoroughly characterized using electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy to give new insight into manufacturing of porous titanium dioxide structures by means of template-based methods. Functionality and integrity of the TiO₂ hollow weblike thin films were successfully confirmed by applying them as electrodes in dye-sensitized solar cells.

Porous Cellulose Beads Fabricated from Regenerated Cellulose as Potential Drug Delivery Carriers

Highly porous cellulose beads (CBs) of various mean sizes were successfully prepared from regenerated cellulose of paper wastes. The drug delivery characteristics of CBs with different mean sizes were investigated using curcumin as the model drug under controlled conditions. The loading capacity and efficiency of curcumin onto CBs were substantially influenced by factors such as their morphological characteristics, curcumin concentration, and duration of loading. The release kinetic profiles of curcumin from CBs of different mean sizes were investigated in media of pH values resembling digestive juices and intestinal fluids. Release kinetic models were used to simulate and elucidate release kinetics and mechanisms of curcumin from CBs under specific conditions. The loading capacity and efficiency of curcumin onto CBs could be enhanced via the optimization of curcumin solution concentration and the morphological characteristics of CBs, whereas the release kinetic profiles of curcumin from CBs could be modulated by varying the mean diameter of CBs. Optimized CBs derived from regenerated cellulose of paper wastes are potentially useful as cost-effective drug delivery carriers.

Orthotropic Piezoelectricity in 2D Nanocellulose

The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V-1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.

Preparation of Porous Cellulose Beads via Introduction of Diamine Spacers

The current work presents a synthesis route based on the reductive amination of 2,3-dialdehyde cellulose beads with diamines to render micrometer-sized beads with increased specific surface area (SSA) and porosity in the mesoporous range. Specifically, the influence of the reductive amination of 2,3-dialdehyde cellulose (DAC) using aliphatic and aromatic tethered mono- and diamines on bead microstructure was investigated. Aliphatic and aromatic tethered monoamines were found to have limited utility for producing porous beads whereas the introduction of diamines provided beads with a porous texture and an SSA increasing from <1 to >30 m(2)/g. Both aliphatic and aromatic diamines were found to be useful in producing porous beads having a pore size distribution range of 10 to 100 nm, as verified by N2 gas adsorption and mercury intrusion porosimetry analyses. The true density of the functionalized DAC beads decreased to an average of about 1.36 g/cm(3) as compared to 1.48 g/cm(3) for the unfunctionalized, fully oxidized DAC beads. The total porosity of the beads was, according to mercury porosimetry, in the range of 54-64%. Reductive amination with 1,7-diaminoheptane provided beads that were stable under alkaline conditions (1 M NaOH). It was concluded that the introduction of tethered diamines into DAC beads is a facile method for producing mesoporous beads.

Construction of biocompatible regenerated cellulose/SPI composite beads using high-voltage electrostatic technique

Regenerated cellulose/SPI composite beads fabricated by a high-voltage electrostatic technique exhibited good cytocompatibility.

Bio-inspired writable multifunctional recycled paper with outer and inner uniform superhydrophobicity

One kind of multifunctional superhydrophobic recycled paper from the secondary use of waste paper has been prepared successfully with wonderful self-cleaning, anti-fouling and oil absorption abilities.

Alginate/magnetite hybrid beads for magnetically stimulated release of dopamine

Hybrid beads composed of magnetite nanoparticles (MNP) and alginate (Alg) were synthesized and coded as Alg-MNP. They were incubated in dopamine (DOPA) solution (5 g/L), at pH 7.4 and 8 °C, during 12 h, promoting the DOPA loaded magnetic beads, coded as Alg-MNP/DOPA. The release of DOPA was further evaluated in the absence and the presence of external magnetic field (EMF) of 0.4 T. The products Alg-MNP and Alg-MNP/DOPA were characterized by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared vibrational spectroscopy (FTIR), UV spectrophotometry, thermogravimetric analyses (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses and superconducting quantum interference device (SQUID) magnetometer. The magnetic and chemical properties of Alg-MNP beads were not affected by DOPA loading. The incorporation of DOPA into the beads depended on the pH and on the negative charge density. At pH 7.4 38% of DOPA were loaded into Alg-MNP beads, whereas at pH 2 or using neat Alg beads (lower charge density than Alg-MNP) the loading efficiency decreased to one third or less. In the absence of EMF, 24% of the loaded DOPA was released from Alg-MNP at pH 7.4 over a period of 26 h. The released amount increased to 33% under the stimulus of EMF. A model was proposed to explain the loading efficiency of charged drugs, as DOPA, into hybrid beads and the role played by EMF on delivery systems, where drug and matrix are oppositely charged. The results suggest that the alginate combined with magnetite nanoparticles is a promising system for release of DOPA in the presence of EMF.

An effective and recyclable adsorbent for the removal of heavy metal ions from aqueous system: Magnetic chitosan/cellulose microspheres

Development of highly cost-effective, highly operation-convenient and highly efficient natural polymer-based adsorbents for their biodegradability and biocompatibility, and supply of safe drinking water are the most threatening problems in water treatment field. To tackle the challenges, a new kind of efficient recyclable magnetic chitosan/cellulose hybrid microspheres was prepared by sol-gel method. By embedding magnetic γ-Fe2O3 nanoparticles in chitosan/cellulose matrix drops in NaOH/urea aqueous solution, it combined renewability and biocompatibility of chitosan and cellulose as well as magnetic properties of γ-Fe2O3 to create a hybrid system in heavy metal ions removal.

Preparation of reactive fibre interfaces using multifunctional cellulose derivatives

Cellulose fibres have poor reactivity and limited potential for surface engineering with advanced chemical functionalization in water. In this work, cellulose fibres were decorated with azide functions by charge-directed self-assembly of a novel water-soluble multifunctional cellulose derivative yielding reactive fibres. Propargylamine and 1-ethynylpyrene were utilized as a proof of concept that alkyne molecules may react with the azide functions of the reactive fibres via copper(I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAc) reaction in mild conditions. Chemical characterization of the fibres was carried out using classical techniques such as Raman-, fluorescence-, and UV-vis spectroscopy. Among other techniques, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray spectroscopy (XPS), two-photon microscopy (TPM), and inductively coupled plasma mass spectrometry (ICP-MS) were useful tools for additional characterization of the fibres decorated with amino- or photoactive groups. The information gathered in this work might contribute to the basis for the preparation of reactive cellulose-based interfaces with potential application in CuAAc reactions.

Cellulose gel dispersion: From pure hydrogel suspensions to encapsulated oil-in-water emulsions

Cellulose hydrogel particles were fabricated from molecularly-dissolved cellulose/IL solutions. The characteristics of the formed hydrogels (cellulose content, particles' size and porosity) were determined as a function of cellulose concentration in the precursor solutions. There is a significant change in the hydrogel structure when the initial cellulose solution concentration increases above about 7-9%wt. These changes include increase of the cellulose content in the hydrogel, and decrease in its pore size. The finest cellulose particle dispersions can be obtained using low concentration cellulose/IL solutions (cellulose concentration in dispersion less than 2%wt.) or hydrogels (concentration less than 1%wt.) in a dispersing medium consisting of IL with no more than 20%wt. water. Stable paraffin oil-in-water emulsions are achieved by mixing oil and water with cellulose/IL solutions. The optimal conditions for obtaining the finest particles (about 20μm in diameter) are attained using cellulose solutions of concentration between 0.7 and 4%wt. at temperature of 70°C and oil/cellulose mass ratios between 1 and 1.5.

The effect of zinc oxide (ZnO) addition on the physical and morphological properties of cellulose aerogel beads

Microsized open porous cellulose aerogel beads were made using mixtures of NaOH and urea and its properties tuned by varying ZnO.

Multifunctional cellulose beads and their interaction with gram positive bacteria

Cellulose beads with ∼3 mm of diameter and high circularity were obtained by dripping cellulose solutions (5, 6, and 7 wt %) dissolved in NaOH7%/urea12%, into HCl 2 M coagulation bath. Carboxylic groups were generated on beads surface through NaClO/NaClO2/TEMPO oxidation method, achieving total charge density of ∼0.77 mmol/g. Pristine (CB) and oxidized (OCB) beads were characterized by means of optical images analyses, scanning electron microscopy (SEM) and compression tests. Both types of beads, CB and OCB, were used as adsorbent for poly(4-vinyl-N-pentylpyridinium) bromide, QPVP-C5, a bactericidal agent. The adsorption of QPVP-C5 on CB and OCB was evaluated by means of FTIR-ATR, UV-vis, CHN elemental analyses, and X-ray photoelectron spectroscopy (XPS). The adsorbed amount of QPVP-C5 was remarkably higher on OCB than on CB due to ionic interactions. Desorption was less than 5%. The interaction between neat OCB or OCB coated and two different amounts of QPVP-C5 and Gram-positive bacteria Micrococcus luteus was assessed by changes in turbidimetry, SEM, and elemental analyses. Bacteria adsorbed on the surface of neat OCB and weakly QPVP-C5 coated OCB due to hydrogen bonding or ion-dipole interaction. Notorious bactericidal action was observed for OCB samples coated with large amount of QPVP-C5.

Cellulose: from biocompatible to bioactive material

The immobilization of biomolecules onto cellulose paper turns this environmentally friendly material into a platform for diagnostic devices.

Ionic liquids--promising but challenging solvents for homogeneous derivatization of cellulose

In the past decade, ionic liquids (ILs) have received enormous interest as solvents for cellulose. They have been studied intensively for fractionation and biorefining of lignocellulosic biomass, for dissolution of the polysaccharide, for preparation of cellulosic fibers, and in particular as reaction media for the homogeneous preparation of highly engineered polysaccharide derivatives. ILs show great potential for application on a commercial scale regarding recyclability, high dissolution power, and their broad structural diversity. However, a critical analysis reveals that these promising features are combined with serious drawbacks that need to be addressed in order to utilize ILs for the efficient synthesis of cellulose derivatives. This review presents a comprehensive overview about chemical modification of cellulose in ILs. Difficulties encountered thereby are discussed critically and current as well as future developments in this field of polysaccharide research are outlined.