Microwave-assisted graft copolymerization of ε-caprolactone onto chitosan via the phthaloyl protection method

Trends in "green" and novel methods of pectin modification - A review

Modification of hydrocolloids to alter their functional properties using chemical methods is well documented in the literature. There has been a recent trend of adopting eco-friendly and "green" methods for modification. Pectin, being a very important hydrocolloid finds its use in various food applications due to its gelling, emulsifying, and stabilizing properties. The adoption of various "green" methods can alter the properties of pectin and make it more suitable for incorporation in food products. The novel approaches such as microwave and pulsed electric field can also be utilized for solvent-free modification, making it desirable from the perspective of sustainability, as it reduces the consumption of organic chemicals. Pectic oligosaccharides (POSs) produced via novel approaches are being explored for their biological properties and incorporation in various functional foods. The review can help to set the perspective of potential scale-up and adoption by the food industry for modification of pectin.

Grafting of Natural Polymers and Gums for Drug Delivery Applications: A Perspective Review

Natural polymers have received more attention because of their advantages over synthetic polymers such as abundant availability, low cost, biodegradability and non-toxicity. However, natural polymers suffer some limitations such as drop-in viscosity upon storage, uncontrolled hydration, solubility, inability to perform under high temperature and pressure (thermal stability), etc. In many instances above mentioned drawbacks of natural polymers limits their applications in drug delivery systems. Grafting of natural polymer leads to improved properties and characteristics of backbones of macromolecules such as improvement in gel strength, swelling index, mucoadhesion, drug targeting and drug release profile. Therefore, in recent decades grafting of the natural polymer has gained immense importance for the development of drug delivery systems. In addition to the pharmaceutical applications graft copolymers are extensively utilized in diversified fields. The present review is an attempt to define the grafting, various methods of polymer grafting and their application in drug delivery.

Chitosan grafted/cross-linked with biodegradable polymers: A review

Public perception of polymers has been drastically changed with the improved plastic management at the end of their life. However, it is widely recognised the need of developing biodegradable polymers, as an alternative to traditional petrochemical polymers. Chitosan (CH), a biodegradable biopolymer with excellent physiological and structural properties, together with its immunostimulatory and antibacterial activity, is a good candidate to replace other polymers, mainly in biomedical applications. However, CH has also several drawbacks, which can be solved by chemical modifications to improve some of its characteristics such as solubility, biological activity, and mechanical properties. Many chemical modifications have been studied in the last decade to improve the properties of CH. This review focussed on a critical analysis of the state of the art of chemical modifications by cross-linking and graft polymerization, between CH or CH derivatives and other biodegradable polymers (polysaccharides or proteins, obtained from microorganisms, synthetized from biomonomers, or from petrochemical products). Both techniques offer the option of including a wide variety of functional groups into the CH chain. Thus, enhanced and new properties can be obtained in accordance with the requirements for different applications, such as the release of drugs, the improvement of antimicrobial properties of fabrics, the removal of dyes, or as scaffolds to develop bone tissues.

In vivo approach of simply constructed pyrazinamide conjugated chitosan-g-polycaprolactone micelles for methicillin resistance Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an extensive origin of nosocomial infections that are very much challenging as well as complicated to eradicate mostly due to their strong resistance against all existing antibiotic therapies. Here the chitosan-grafted-polycaprolactone/maleic anhydride-pyrazinamide (CS-g-PCL/MA-PZA) polymeric drug carrier constructed via dialysis for anti-MRSA drugs like rifampicin (RF) and pyrazinamide (PZA) delivery. Nearly 200 nm size of the spherical particle with -20.04 mV of zeta potential observed. The cumulative PZA and RF releases from the carrier were observed 83.25% and 76.54% respectively in pH 5.5, and the in vitro drug release profile demonstrates that the fabricated micelle was pH-responsive. For the intestinal colonization, an in vivo assay performed using C. elegans, and the CS-g-PCL/MA-PZA/RF micelles treated worms generally belong to the weakly colonized category. Therefore, the study revealed that CS-g-PCL/MA-PZA/RF micelle could be a promising approach for therapeutic applications to achieve efficient anti-MRSA drug delivery.

Galactosylated chitosan-polycaprolactone nanoparticles for hepatocyte-targeted delivery of curcumin

Galactosylated chitosan-polycaprolactone (Gal-CH-PCL) copolymers with a galactosylation degree of around 10% and varied PCL percentages less than 40 wt% were synthesized and used to produce nanoparticles for delivering curcumin. Some nanoparticles with encapsulation efficiency of 70% or higher and sizes changing from 100 to 250 nm were able to deliver curcumin in a controlled manner. PCL content in Gal-CH-PCLs was found to be a key factor for governing the release behavior of nanoparticles. Hepatocyte-targeted characteristic of nanoparticles was confirmed using human hepatocellular carcinoma (HepG2) cells. In comparison to free curcumin, curcumin-loaded Gal-CH-PCL nanoparticles well retained its anticancer activity. At an equivalent curcumin-dose of around 20 μg/mL that was found to be relatively safe to human normal liver cells, the results obtained from flow-cytometry revealed that some optimized Gal-CH-PCL nanoparticles showed more than 6-fold increasing abilities to induce the apoptosis and necrosis of HepG2 cells during 72 h treatment compared to free curcumin.

Interaction of bovine serum albumin with self-assembled nanoparticles of 6-O-cholesterol modified chitosan

In order to understand the nanomedicine and nanotoxicological effects of self-assembled nanoparticles of 6-O-cholesterol modified chitosan (O-CHCS NPs) as a carrier for drug delivery systems, the interaction between O-CHCS NPs and bovine serum albumin (BSA) was studied by spectroscopy and calorimetric methods. The morphology of the complex between O-CHCS NPs and BSA observed by transmission electron microscope (TEM) was almost spherical shape. The size and the zeta potential of the complex increased with the concentration of O-CHCS NPs increasing. The fluorescence spectroscopy indicated that the micro-environment around the tryptophan (Trp) residues in BSA had slight change due to only partially exposure of the Trp residues to water in the interaction process. Compared with free BSA, the addition of O-CHCS NPs led to the decrease of α-helical content of BSA and the increase of β-strand content. Isothermal titration calorimeter (ITC) results showed that the binding reaction between O-CHCS NPs and BSA was exothermic and enthalpically driven. Therefore, it could be concluded that hydrogen bonding, hydrophobic and electrostatic interactions played a key role in the complex formation, and the formation mechanism was proposed accordingly. In addition, cytotoxicity assay implied that O-CHCS NPs were non-cytotoxic and biocompatible up to 200 μg mL(-1). These data demonstrated the potential application of O-CHCS NPs for drug delivery.

Rapid Synthesis of Acrylamide onto Xanthan Gum Based Hydrogels under Microwave Radiations for Enhanced Thermal and Chemical Modifications

The main objective of this research work is to synthesize crosslinked hydrogel from xanthan gum and acrylamide under the influence of microwave radiations by graft polymerization technique in presence of potassium persulphate-N,N'-methylene-bis-acrylamide as initiator-crosslinker system. Different reaction parameters such as reaction time, pH, solvent and initiator concentration were optimized a function of percentage grafting. Monomer and cross-linker concentrations were optimized as a function of percentage swelling for getting the polymer with maximum water absorption capacity. The superabsorbent was characterized using different characterization techniques like, FTIR, TGA / DTA / TDG and X-ray diffraction. The candidate polymer was found to be thermally more stable than the xanthan gum.

Recent Advances in Microwave-Assisted Polymer Synthesis

In the past few years the use of microwave irradiation in polymer science has become a well-established technique to drive and promote chemical reactions. The main advantages of microwave heating are a strong reduction in reaction time and a high potential to contribute to green and sustainable chemistry. This article provides a short review of recent examples in the field of microwave-assisted polymer synthesis with special emphasis on radical polymerizations, step-growth polymerizations, ring-opening polymerizations, and polymer modifications.