Hasan Sadeghifar

Photobactericidal Porphyrin-Cellulose Nanocrystals: Synthesis, Characterization, and Antimicrobial Properties

Adherence and survival of pathogenic bacteria on surfaces leading to concomitant transmission to new hosts significantly contributes to the proliferation of pathogens, which in turn considerably increases the threat to human health, particularly by antibiotic-resistant bacteria. Consequently, more research into effective surface disinfection and alternative materials (fabrics, plastics, or coatings) with antimicrobial and other bioactive characteristics is desirable. This report describes the synthesis and characterization of cellulose nanocrystals that were surface-modified with a cationic porphyrin. The porphyrin was appended onto the cellulose surface via the Cu(I)-catalyzed Huisgen-Meldal-Sharpless 1,3-dipolar cycloaddition having occurred between azide groups on the cellulosic surface and porphyrinic alkynes. The resulting, generally insoluble, crystalline material, CNC-Por (5), was characterized by infrared and diffusion (1)H NMR spectroscopies, gel permeation chromatography, and thermogravimetric analysis. Although only suspended, and not dissolved, in an aqueous system, CNC-Por (5) showed excellent efficacy toward the photodynamic inactivation of Mycobacterium smegmatis and Staphylococcus aureus , albeit only slight activity against Escherichia coli . The synthesis, properties, and activity of CNC-Por (5) described herein serve as a benchmark toward our overall objectives of developing novel, potent, bioactive, photobactericidal materials that are effective against a range of bacteria, with potential utilization in the health care and food preparation industries.

Porphyrin‐Cellulose Nanocrystals: A Photobactericidal Material that Exhibits Broad Spectrum Antimicrobial Activity†

Towards our overall objectives of developing potent antimicrobial materials to combat the escalating threat to human health posed by the transmission of surface‐adhering pathogenic bacteria, we have investigated the photobactericidal activity of cellulose nanocrystals that have been modified with a porphyrin‐derived photosensitizer (PS). The ability of these previously synthesized porphyrin‐cellulose‐nanocrystals (CNC‐Por (1)) to mediate bacterial photodynamic inactivation was investigated as a function of bacterial strain, incubation time and illumination time. Despite forming an insoluble suspension, CNC‐Por (1) showed excellent efficacy toward the photodynamic inactivation of Acinetobacter baumannii, multidrug‐resistant Acinetobacter baumannii (MDRAB) and methicillin‐resistant Staphylococcus aureus (MRSA), with the best results achieving 5–6 log units reduction in colony forming units (CFUs) upon illumination with visible light (400–700 nm; 118 J cm−2). CNC‐Por (1) mediated the inactivation of Pseudomonas aeruginosa, although at reduced activity (2–3 log units reduction). Confocal laser scanning microscopy of CNC‐Por (1) after incubation with A. baumannii or S. aureus suggested a lack of internalization of the PS. Research into alternative materials such as CNC‐Por (1) may lead to their application in hospitals and healthcare‐related industries wherein novel materials with the capability of reducing the rates of transmission of a wide range of bacteria, particularly antibiotic resistant strains, are desired.

Kraft Lignin Chain Extension Chemistry via Propargylation, Oxidative Coupling, and Claisen Rearrangement

Despite its aromatic and polymeric nature, the heterogeneous, stochastic, and reactive characteristics of softwood kraft lignin seriously limit its potential for thermoplastic applications. Our continuing efforts toward creating thermoplastic lignin polymers are now focused at exploring propargylation derivatization chemistry and its potential as a versatile novel route for the eventual utilization of technical lignins with a significant amount of molecular control. To do this, we initially report the systematic propargylation of softwood kraft lignin. The synthesized derivatives were extensively characterized with thermal methods (DSC, TGA), (1)H, (13)C, and quantitative (31)P NMR and IR spectroscopies. Further on, we explore the versatile nature of the lignin pendant propargyl groups by demonstrating two distinct chain extension chemistries; the solution-based, copper-mediated, oxidative coupling and the thermally induced, solid-state, Claissen rearrangement polymerization chemistries. Overall, we show that it is possible to modulate the reactivity of softwood kraft lignin via a combination of methylation and chain extension providing a rational means for the creation of higher molecular weight polymers with the potential for thermoplastic materials and carbon fibers with the desired control of structure-property relations.

Photoresponsive Cellulose Nanocrystals

In this communication a method for the creation of fluorescent cellulose nanoparticles using click chemistry and subsequent photodimerization of the installed side-chains is demonstrated. In the fi...

Synthesis, Characterization, and Antimicrobial Efficacy of Photomicrobicidal Cellulose Paper.

Toward our goal of scalable, antimicrobial materials based on photodynamic inactivation, paper sheets comprised of photosensitizer-conjugated cellulose fibers were prepared using porphyrin and BODIPY photosensitizers, and characterized by spectroscopic (infrared, UV-vis diffuse reflectance, inductively coupled plasma optical emission) and physical (gel permeation chromatography, elemental, and thermal gravimetric analyses) methods. Antibacterial efficacy was evaluated against Staphylococcus aureus (ATCC-2913), vancomycin-resistant Enterococcus faecium (ATCC-2320), Acinetobacter baumannii (ATCC-19606), Pseudomonas aeruginosa (ATCC-9027), and Klebsiella pneumoniae (ATCC-2146). Our best results were achieved with a cationic porphyrin-paper conjugate, Por((+))-paper, with inactivation upon illumination (30 min, 65 ± 5 mW/cm(2), 400-700 nm) of all bacterial strains studied by 99.99+% (4 log units), regardless of taxonomic classification. Por((+))-paper also inactivated dengue-1 virus (>99.995%), influenza A (∼ 99.5%), and human adenovirus-5 (∼ 99%). These results demonstrate the potential of cellulose materials to serve as scalable scaffolds for anti-infective or self-sterilizing materials against both bacteria and viruses when employing a photodynamic inactivation mode of action.

Quantitative 31P NMR analysis of solid wood offers an insight into the acetylation of its components

As a solid substrate, wood and its components are almost invariably examined via spectroscopic or indirect methods of analysis. Unlike earlier approaches, in this effort we dissolve pulverized wood in ionic liquid and then directly derive its functional group contents by quantitative (31)P NMR. As such, this novel analytical methodology is thoroughly examined and an insight into the detailed way acetylation proceeds on solid wood and its components is provided as a function of wood density and within its various anatomical features. As anticipated, the efficiency of acetylation was found to be greater within low density wood than in high density wood. The lignin, the cellulose and the hemicelluloses of the low density wood was found to be acetylated nearly twice as fast with remarkable differences in their quantitative degree of acetylation amongst them. This direct analytical data validates the applied methodology and confirms, for the first time, that the order of acetylation in solid wood is lignin>hemicellulose>cellulose and no reactivity differences exist between early wood and late wood.

Chemical composition of the essential oils from leaves, flowers, stem and root of Centaurea zuvandica Sosn.

Abstract The essential oils obtained from the dried leaves, flowers, stem and root of Centaurea zuvandica Sosn. (Compositae) were analyzed using GC and GC/MS. Twenty components were identified in the oil of leaves with spathulenol (28.1%), α-pinene (21.3%) and caryophyllene oxide (9.7%) as main constituents. Fifteen compounds were identified in the oil of flowers with spathulenol (32.3%), α-pinene (25.8%) and limonene (8.2%) as main components. Eighteen compounds were characterized in the oil of stem with spathulenol (37.1%), α-terpineol (12.8%), caryophyllene oxide (8.2%) as main constituents. In the oil of root, germacrene D (35.2%), spathulenol (15.7%) and α-terpineol (11.6%) were found as main constituents. All oils consisted of monoterpene and sesquiterpene components.

Morphological and interfacial properties of chemically-modified tropical hardwood

Chemical modification of wood with acetic anhydride is an environmentally friendly process to sustain and improve wood properties over a longer term than naturally allowed. Such an approach offers many potential and attractive product avenues for the wood industry. In this study, obeche tropical hardwood (Triplochiton scleroxylon) was acetylated with acetic anhydride to improve its mechanical and interfacial properties relative to unmodified wood; specifically, dimensional stability in terms of anti-swelling efficiency (ASE), water repellent efficiency (WRE), and hydrophobicity were the target properties of interest. The chemical modification was carried out at 120 °C with five varying reaction times (1–5 h) to optimize the reaction based on weight percent gain (WPG). It was found that as the reaction time increased, the WGP and hydrophobicity increased, but the percentage of water absorption and volumetric swelling diminished. In total, acetylation provided the hardwood with good dimensional stability. The chemically-modified wood was characterized by Fourier transform-infrared (FT-IR), dynamic contact angle, and an Owens–Wendt surface energy analysis.

Coacervated liposoluble fructan-based host–guest microspheres as unique drug delivery materials

A fundamental requirement in drug delivery design is the development of robust, target-specific, biocompatible, and pharmocokinetically-active cargo carriers. The use of natural polysaccharides for drug delivery has been a subject of long standing interest because they display many of the necessary aforementioned attributes. Herein, the current research details a new approach to a drug release system composed of microspheres derived from unique acetylated Agave tequilana Weber var. Azul fructans. The driving force and novelty behind this approach is that these fructans are liposoluble while still being able to be metabolized by bifidobacteria (lower GI, native colon bacteria). Modification of fructan solubility through acetylation supported the preparation of microspheres by precipitation–coacervation, thus providing a new synthetic approach for polysaccharides-based cargo carriers to facilitate the encapsulation of liposoluble cargo molecules such as ibuprofen. It was found that the enzymatic activity of B. animalis, a representative bacteria found in the human colon, was reduced, albeit, but not at the expense of providing a very compellingly favorable drug release profile.