Processing and Properties of Nanofibrous Bacterial Cellulose-Containing Polymer Composites: A Review of Recent Advances for Biomedical Applications

Abstract

Bacterial cellulose (BC) is an extracellular natural polymer produced by many microorganisms and its properties could be tailored via specific fabrication methods and culture conditions. There is a growing interest in BC derived materials due to the main features of BC such as porous fibrous structure, high crystallinity, impressive physico-mechanical properties, and high water content. However, pristine BC lacks some features, limiting its practical use in varied applications. Thus, fabrication of BC composites has been attempted to overcome these constraints. This review article overviews most recent advance in the development of BC composites and their potential in biomedicine including wound dressing, tissue engineering scaffolds, and drug delivery. Special emphasis is placed on the fabrication and applications of BC-containing nanofibrous composites for biomedical usage. It summarizes electrospinning of BC-based nanofibers and their surface modification with an outline on challenges and future perspective.     

HPTLC Procedure for Determination of Levonorgestrel in the Drug-Release Media of an In-situ-Forming Delivery System

JPC – Journal of Planar Chromatography – Modern TLC -     

Application of chromium‐doped fullerene as a carrier for thymine and uracil nucleotides: Comprehensive density functional theory calculations

The interactions of the nucleobases thymine (C₅H₆N₂O₂) and uracil (C₄H₄N₂O₂) with Cr‐doped C₂₀ fullerene (C₁₉Cr) are investigated by performing density functional theory calculations. The adsorption of these nucleobases on C₁₉Cr leads to two distinct geometries (P1 and P2) differing in the orientation of the nucleobases. The interaction of the nucleobases with the C₁₉Cr nanocluster is highly exothermic, revealing that they are chemically adsorbed on C₁₉Cr. The results show that the binding energy of the thymine–C₁₉Cr complex is slightly higher than that of the uracil–C₁₉Cr complex. In addition, the P2 geometry is more stable compared to P1 due to the higher binding energy in the former configuration. However, based on the results of natural bond orbital and frontier molecular orbitals analyses, the C₁₉Cr nanocage has higher reactivity with the nucleobases in P1 geometry in comparison with P2 due to the larger charge transfer and orbital hybridization in the former geometry. Moreover, the band gap of the C₁₉Cr nanocage decreases after interaction with the nucleobases, and interestingly the impact is more pronounced for P1 geometry, confirming the higher sensitivity of C₁₉Cr to the nucleobases in P1 geometry. Our findings reveal the promising potential of C₁₉Cr as an organometallic carrier for nucleobases thymine and uracil.     

Synthesis of Poly (methyl methacrylate)/Zinc Oxide Nanocomposite with Core-Shell Morphology by Atom Transfer Radical Polymerization

A method to prepare zinc oxide (ZnO) nanoparticles with a covalently bonded poly(methyl methacrylate) (PMMA) shell by surface initiated atom transfer radical polymerization (ATRP) was reported. First, the initiator for ATRP was covalently bonded onto the surface of zinc oxide nanoparticles through our novel method. Firstly, the surface of ZnO nanoparticle was treated with 3-aminopropyl triethoxysilane, a silane coupling agent, and then this functionalization nanoparticle was reacted with α-chloro phenyl acetyl chloride to prepare atom transfer radical polymerization macroinitiator. The metal-catalyzed radical polymerization of MMA with ZnOmacroinitiator was performed using a copper catalyst system to give the ZnO-based nanoparticles hybrids linking PMMA segments (poly (methyl methacrylate)/zinc oxide nanocomposite). These hybrid nanoparticles had an exceptionally good dispersability in organic solvents and were subjected to detailed characterization using FTIR, TEM and TGA and DSC analyzed.     

Investigating the nature of intermolecular and intramolecular bonds in noble gas containing molecules

This article presents a theoretical study on a number of selected noble gas containing systems of the general formula FNgR and NgR (Ng = He, Ne, Ar, Kr, Xe and R = CH₃, CN, CCH, BO, BNH, H, BeO, and AuF). The principal structures, bond energies, spectroscopic, and electronic properties of 28 noble gas containing molecules were investigated using density functional theory at the BMK level. Quantum theory of atoms in molecules, natural bond orbital, and several other analysis methods have been used to provide more insight into the nature of noble gas bonds. Although both F? Ng and Ng? R bonds in the investigated molecules are assigned to have partially covalent and partially electrostatic nature, the covalent character is dominant in Ng? R bonds. In the second part, the intermolecular interactions between FNgR molecules and hydrogen fluoride are overviewed with emphasis on the hydrogen bonding through the fluorine side of noble gas molecule with hydrogen of HF. The calculated interaction energies were found to decrease in magnitude going down the noble gas series. For all noble gases, the strongest hydrogen bond has been observed in the case R=CH₃. On the contrary, using R=CN in the FNgR moiety weakens the interaction strength. © 2014 Wiley Periodicals, Inc.     

A polyaniline-magnetite nanocomposite as an anion exchange sorbent for solid-phase extraction of chromium(VI) ions

This work describes a novel polyaniline-magnetite nanocomposite and its application to the preconcentration of Cr(VI) anions. The material was obtained by oxidative polymerization of aniline in the presence of magnetite nanoparticles. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Extraction time, amount of magnetic sorbent and pH value were selected as the main factors affecting sorption. The sorption capacity of the sorbent for Cr(VI) is 54 mg g⁻¹. The type, volume and concentration of the eluents, and the elution time were selected as main factors in the optimization study of the elution step. Following sorption and elution, the Cr(VI) ions were reacted with diphenylcarbazide, and the resulting dye was quantified by HPLC with optical detection at 546 nm. The limit of detection is 0.1 μg L⁻¹, and all the relative standard deviations are <6.3 %. The nanocomposite was successfully applied to the rapid extraction and determination of trace quantities of Cr(VI) ions in spiked water samples.

A schematic procedure of magnetic solid phase extraction

     

A polyaniline-magnetite nanocomposite as an anion exchange sorbent for solid-phase extraction of chromium(VI) ions

This work describes a novel polyaniline-magnetite nanocomposite and its application to the preconcentration of Cr(VI) anions. The material was obtained by oxidative polymerization of aniline in the presence of magnetite nanoparticles. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Extraction time, amount of magnetic sorbent and pH value were selected as the main factors affecting sorption. The sorption capacity of the sorbent for Cr(VI) is 54 mg g^?1. The type, volume and concentration of the eluents, and the elution time were selected as main factors in the optimization study of the elution step. Following sorption and elution, the Cr(VI) ions were reacted with diphenylcarbazide, and the resulting dye was quantified by HPLC with optical detection at 546 nm. The limit of detection is 0.1 μg L^?1, and all the relative standard deviations are <6.3 %. The nanocomposite was successfully applied to the rapid extraction and determination of trace quantities of Cr(VI) ions in spiked water samples. Figure

A schematic procedure of magnetic solid phase extraction     

Substituent effects in cooperativity of chalcogen bonds

In the present work, substituent effects on cooperativity of S···N chalcogen bonds are studied in XHS···NCHS···4-Z–Py (X = F, Cl; Z = H, F, OH, CH₃, NH₂, NO₂, and CN; and Py = pyridine) complexes using ab initio calculations. An increased attraction or a positive cooperativity is observed on introduction of a third molecule to the XHS···NCHS and NCHS···4-Z–Py binary systems. The shortening of each chalcogen bond distance in the ternary systems is dependent on the substituent Z and is increased in the order Z = NH₂ > OH > CH₃ > H > F > CN > NO₂. The electronic aspects of the complexes are analysed using molecular electrostatic potential, and the parameters derived from the atoms in molecules and natural bond orbital methodologies. According to interaction energy decomposition analysis, the electrostatic energies are important in the interaction energy of S···N bonds and may be regarded as being responsible for the stability of these complexes.