Recent Progress in the Synthesis and Biomedical Properties of Natural Biopolymer Composites.

BACKGROUND: Natural biopolymers have drawn extensive attention because of their great biocompatibility, biodegradability, renewability, and the availability of various reactive functional groups for modifying and introducing novel components. In the last few years, numerous natural biopolymer composites have been exploited to improve their physical and chemical properties and add new functionalities. METHODS: Herein, we summarize the current progress in three common classes of natural biopolymer-based composites, including alginate, chitosan, and gelatin. RESULTS: The morphology characteristics, preparation methods, and unique functionalities of these biopolymer composites are also analyzed and discussed. CONCLUSION: Finally, the article offers an overview of recent progress in the main biomedical applications such as tissue engineering, wound-healing, and drug delivery, which inspires further progress in biopolymer composites with tailored mechanical property and stable characteristics for pharmaceutical and biomedical applications.

Cellulose-based Nanocarriers as Platforms for Cancer Therapy.

Cellulose is an important environmentally-friendly renewable polymer on the earth. Cellulose has been widely used as feedstocks for the synthesis of biomaterials, biofuels and biochemicals. Recently, cellulose and cellulose derivatives have received intense attention in biomedical applications, such as tissue engineering, scaffold, artificial blood vessel, skin grafts, artificial skin, drug carrier, and chronic skin diseases, many of which are somehow related to cancer therapy. In this mini-review, we focus on the up-to-date development of cellulosebased nanocarriers used for cancer therapy. Various cellulose-based nanocarriers such as bacterial cellulose (BC), cellulose acetate, microcrystalline cellulose, carboxymethyl cellulose, cellulose nanocrystals, cellulose nanofibrills, etc, are reviewed in terms of being used in drug delivery systems for cancer treatment. Different strategies for the synthesis of cellulose-based nanocarriers are summarized. Special attention is paid on the structure and properties of cellulose-based drug carriers for cancer therapy via some representative examples. Finally, the problems and future developments of these promising polymeric nanocarriers are raised and proposed.

Microwave-Assisted Hydrothermal Synthesis of Cellulose/Hydroxyapatite Nanocomposites.

In this paper, we report a facile, rapid, and green strategy for the synthesis of cellulose/hydroxyapatite (HA) nanocomposites using an inorganic phosphorus source (sodium dihydrogen phosphate dihydrate (NaH2PO4·2H2O)), or organic phosphorus sources (adenosine 5'-triphosphate disodium salt (ATP), creatine phosphate disodium salt tetrahydrate (CP), or D-fructose 1,6-bisphosphate trisodium salt octahydrate (FBP)) through the microwave-assisted hydrothermal method. The effects of the phosphorus sources, heating time, and heating temperature on the phase, size, and morphology of the products were systematically investigated. The experimental results revealed that the phosphate sources played a critical role on the phase, size, and morphology of the minerals in the nanocomposites. For example, the pure HA was obtained by using NaH2PO4·2H2O as phosphorus source, while all the ATP, CP, and FBP led to the byproduct, calcite. The HA nanostructures with various morphologies (including nanorods, pseudo-cubic, pseudo-spherical, and nano-spherical particles) were obtained by varying the phosphorus sources or adjusting the reaction parameters. In addition, this strategy is surfactant-free, avoiding the post-treatment procedure and cost for the surfactant removal from the product. We believe that this work can be a guidance for the green synthesis of cellulose/HA nanocomposites in the future.

The microwave-assisted ionic-liquid method: a promising methodology in nanomaterials.

In recent years, the microwave-assisted ionic-liquid method has been accepted as a promising methodology for the preparation of nanomaterials and cellulose-based nanocomposites. Applications of this method in the preparation of cellulose-based nanocomposites comply with the major principles of green chemistry, that is, they use an environmentally friendly method in environmentally preferable solvents to make use of renewable materials. This minireview focuses on the recent development of the synthesis of nanomaterials and cellulose-based nanocomposites by means of the microwave-assisted ionic-liquid method. We first discuss the preparation of nanomaterials including noble metals, metal oxides, complex metal oxides, metal sulfides, and other nanomaterials by means of this method. Then we provide an overview of the synthesis of cellulose-based nanocomposites by using this method. The emphasis is on the synthesis, microstructure, and properties of nanostructured materials obtained through this methodology. Our recent research on nanomaterials and cellulose-based nanocomposites by this rapid method is summarized. In addition, the formation mechanisms involved in the microwave-assisted ionic-liquid synthesis of nanostructured materials are discussed briefly. Finally, the future perspectives of this methodology in the synthesis of nanostructured materials are proposed.

Microwave synthesis of cellulose/CuO nanocomposites in ionic liquid and its thermal transformation to CuO.

The purpose of this study is to develop a green strategy to synthesize the cellulose-based nanocomposites and open a new avenue to the high value-added applications of biomass. Herein, we reported a microwave-assisted ionic liquid route to the preparation of cellulose/CuO nanocomposites, which combined three major green chemistry principles: using environmentally friendly method, greener solvents, and sustainable resources. The influences of the reaction parameters including the heating time and the ratio of cellulose solution to ionic liquid on the products were discussed by X-ray powder diffraction, Fourier transform infrared spectrometry, and scanning electron microscopy. The crystallinity of CuO increased and the CuO shape changed from nanosheets to bundles and to particles with increasing heating time. The ratio of cellulose solution to ionic liquid also affected the shapes of CuO in nanocomposites. Moreover, CuO crystals were obtained by thermal treatment of the cellulose/CuO nanocomposites at 800 °C for 3 h in air.

Isolation and characterization of hemicelluloses extracted by hydrothermal pretreatment.

The dewaxed sample from Triploid of Populus tomentosa Carr. was extracted by using organic alkaline solvent (Dimethylformamide, DMF) via hydrothermal pretreatment. Neutral sugar compositions and molecular weight analysis demonstrated that the hemicellulosic fractions with a higher Uro/Xyl ratio, namely the more branched hemicelluloses, had higher molecular weights. Interestingly, these results were different from the previous report, in which the ratio of Uro/Xyl in the water-soluble hemicellulosic fraction was more than that of the alkali-soluble hemicellulosic fraction. Spectroscopy (FTIR, (1)H NMR, (13)C NMR, and HSQC) analysis indicated that the hemicellulosic fractions were mainly composed of (1→4)-linked α-D-glucan from starch and (1→4)-linked ß-D-xylan attached with minor amounts of branched sugars from hemicelluloses. In addition, thermal analysis implied that linear hemicelluloses showed more thermal stability than the branched ones during pyrolysis.

Nanocomposites of cellulose/iron oxide: influence of synthesis conditions on their morphological behavior and thermal stability.

Nanocomposites of cellulose/iron oxide have been successfully prepared by hydrothermal method using cellulose solution and Fe(NO3)3·9H2O at 180 °C. The cellulose solution was obtained by the dissolution of microcrystalline cellulose in NaOH/urea aqueous solution, which is a good system to dissolve cellulose and favors the synthesis of iron oxide without needing any template or other reagents. The phases, microstructure, and morphologies of nanocomposites were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectra (EDS). The effects of the heating time, heating temperature, cellulose concentration, and ferric nitrate concentration on the morphological behavior of products were investigated. The experimental results indicated that the cellulose concentration played an important role in both the phase and shape of iron oxide in nanocomposites. Moreover, the nanocomposites synthesized by using different cellulose concentrations displayed different thermal stabilities.

Recent progress on fabrication of calcium-based inorganic biodegradable nanomaterials.

Calcium-based inorganic biodegradable nanomaterials (CIBNs) including calcium phosphate, hydroxyapatite (HA), calcium silicate, calcium carbonate, and calcium sulfate, are important materials and have been widely used in biomedical field. Although CIBNs have been intensively studied, there are only a few synthesis methods that showed promising characteristics for practical applications. Here, we intend to review recent progress in the synthesis of the CIBNs including both patents and papers. In addition, the mechanisms of CIBNs are introduced. Finally, the current and future developments are put forward. In summary, we briefly review the patents and the patent-interrelated papers concerning the fabrication, mechanism, and future development of CIBNs in this mini-review. The paper provides an overview about the potential application of nanotechnology in biomedical field.

Recent Progress on Fabrication of Calcium-Based Inorganic Biodegradable Nanomaterials.

Calcium-based inorganic biodegradable nanomaterials (CIBNs) including calcium phosphate, hydroxyapatite (HA), calcium silicate, calcium carbonate, and calcium sulfate, are important materials and have been widely used in biomedical field. Although CIBNs have been intensively studied, there are only a few synthesis methods that showed promising characteristics for practical applications. Here, we intend to review recent progress in synthesis of the CIBNs including both patents and papers. In addition, the mechanisms of CIBNs are introduced. Finally, the current & future developments are put forward. In summary, we briefly review the patents and the patent-interrelated papers concerning the fabrication, mechanism, and future development of CIBNs in this mini-review. The paper provides an overview about the potential application of nanotechnology in biomedical field.

Rapid microwave-assisted synthesis and characterization of cellulose-hydroxyapatite nanocomposites in N,N-dimethylacetamide solvent.

Preparation of nanocomposites was carried out using microcrystalline cellulose, CaCl(2), and NaH(2)PO(4) in N,N-dimethylacetamide (DMAc) solvent by a microwave-assisted method at 150 degrees C. XRD results showed that the nanocomposites consisted of cellulose and hydroxyapatite (HA). The cellulose existed as a matrix in the nanocomposites. SEM and TEM analysis showed that HA nanorods were homogeneously dispersed in the cellulose matrix. The effects of the microwave heating time on the products were investigated. This method has advantages of being simple, rapid, low-cost, and environmentally friendly.

Microwave-assisted one-step synthesis of polyacrylamide-metal (M = Ag, Pt, Cu) nanocomposites in ethylene glycol.

Polyacrylamide-metal (M = Pt, Ag, Cu) nanocomposites with metal nanoparticles homogeneously dispersed in the polymer matrix have been successfully prepared with the corresponding metal salt and acrylamide monomer in ethylene glycol by microwave heating. This method is based on the single-step simultaneous formation of metal nanoparticles and polymerization of the acrylamide monomer, leading to a homogeneous distribution of metal nanoparticles in the polyacrylamide matrix. Ethylene glycol acts as both a reducing reagent and a solvent, thus no additional reductant is needed. Another advantage is that no initiator for AM polymerization and no surfactant for stabilization of metal nanoparticles are necessary. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), ultraviolet visible (UV-vis) absorption spectra, and thermogravimetric (TG) and differential scanning calorimetric analysis (DSC).