Rizwan Ullah Khan

Recent progress in chemical modification of starch and its applications

Starch has received much attention as a promising natural material both in biomedical fields and waste water treatment due to its unique biological and adsorptive properties. Recently, the modification of starch is rapidly developed along with its growing applications. This review focuses on the ways of chemical modification of starch including cross-linking, grafting, esterification, etherification, dual modification and so on, and presents the applications of the modified starch in fields like drug delivery, tissue engineering and heavy metal and dye removal.

Chemical modification of starch and its application as an adsorbent material

Starch is a biopolymer of plant origin which is cheap abundant and has many applications in food and non-food industries. However, in the native form, its applications are limited due to shortcomings, such as loss of viscosity and thickening power upon cooking and storage, retrogradation characteristics and absence of certain groups responsible for a particular function, etc. So, in order to reduce its limitations and improve its applications, modification of starch is necessary. It can be modified by several ways like chemical modification, physical modification and genetic modification but the most important one is the chemical modification. In this review, we selected the published data related to the chemical modification like grafting, cross-linking, esterification, etherification and dual modification of starch and application of modified starch for the adsorption of organic dyes and heavy metals from water.

Synthesis of polyphosphazenes with different side groups and various tactics for drug delivery

Polyphosphazenes (PPZs) are hybrid polymers comprising a main chain containing nitrogen and phosphorous linked through interchanging single and double bonds, and side chains. The two chlorine atoms attached to the phosphorous of polydichlorophosphazene, which is produced by thermal ring-opening and living-cationic polymerization, are significant in the importance of polyphosphazene, as they can be easily replaced by an uncountable number of nucleophiles, resulting in hundreds of different PPZs with different properties ranging from hydrophobic to hydrophilic, fast to slow degradation, and burst to sustained drug release. More than seven hundred types of PPZs are synthesized as a result of different combinations of side groups. For applications in drug delivery, PPZs can be treated in various ways and converted into different vehicles of nano/micro size to load and release drugs. This review covers the synthesis of PPZs and their different modifications, especially focusing on the side groups and different vehicles, including microspheres, micelles, films and hydrogels, that are involved in drug-delivery applications.

Synthesis of carboxymethyl starch- g -polyvinylpyrolidones and their properties for the adsorption of Rhodamine 6G and ammonia

Carboxymethyl starch-g-polyvinylpyrolidones (CMS-g-PVPs) were prepared by grafting of carboxymethyl starch (CMS) with N-vinylpyrolidone (NVP) using different initiators. The grafting percentage of all the modified starches was determined and the modified starch (CMS-g-PVP-5) with maximum grafting percentage was characterized by elemental analysis, 1H NMR and FT-IR spectroscopy. Crystallinity and thermal properties of CMS-g-PVP-5 were analysed by XRD and TGA, respectively. CMS-g-PVP-5 was then utilized for the adsorption of Rhodamine 6G (dye) from water under different pH, temperature, adsorbate doze and adsorbent concentration. This modified starch showed good adsorption ability towards Rhodamine 6G. CMS-g-PVP-5 was also applied for the adsorption of ammonia gas and proved an exciting adsorbent for ammonia.

Synthesis of ferrocene-based saccharides and their anti-migration and burning rate catalytic properties

In the search for ferrocene-based burning rate catalysts (BRCs) with good burning rate catalytic properties and low migration, we synthesized four ferrocene-based saccharides (S-Fcs). The synthesis of S-Fcs was confirmed by energy-dispersive X-ray (EDX), nuclear magnetic resonance (1H NMR), Fourier transform infra-red (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy. The electrochemical behavior of ferrocene-based BRCs is important to investigate the electron transfer burning rate catalytic mechanism. Therefore, the electrochemical behavior of the S-Fcs was investigated by cyclic voltammetry. The burning rate catalytic properties of the S-Fcs on thermal disintegration of ammonium perchlorate (AP) were determined by TG and DTG techniques. Thermal analysis results showed that the S-Fcs were thermally stable and showed good burning rate catalytic effects on thermal disintegration of AP. The S-Fcs were also analyzed in anti-migration studies in comparison with the most commonly used ferrocene-based burning rate catalyst (catocene) and ferrocene. It was found that S-Fcs showed excellent anti-migration behavior in AP-based propellant as compared to catocene and ferrocene.

Recent progress in the electron paramagnetic resonance study of polymers

This review article provides an overview of the contemporary research based on a tailor-made technique to understand the paramagnetic behavior of different polymer classes. The ubiquity of free radicals, including biradicals, triplet states, and point defects in polymer systems, has made EPR spectroscopy an indispensable tool in polymer science among other mainstream analytical techniques. The scope of EPR spectroscopy has broadened particularly due to the growing impulse to produce polymers with enhanced stability, to follow the charge transfer process in conducting polymers, to decipher the complex nanoscale dynamics of polymers, to fathom out the reaction mechanisms and kinetics of complex polymer reactions in a more facile way, and to carry out comprehensive structural and conformational analyses. Recent studies have hinted at the effectiveness of EPR spectroscopy in collecting data with sub-nanometer spatial resolution to decipher intrinsic intricacies, while keeping the pristine geometry unperturbed, a task yet not achievable with other conventional techniques. EPR spectroscopy is being applied in polymer science in multifarious ways, including, but not limited to, exploring the structure, conformation, and dynamics of polymer chain segments, degradation or defect studies, charge transfer properties, kinetics and reaction mechanisms especially of free radical polymerization reactions, and EPR imaging of the polymer matrix. A recent surge in its applications indicates that EPR spectroscopy is going to make a profound impact in the field of polymer science in upcoming years.

Synthesis of hydrogel-bearing phenylboronic acid moieties and their applications in glucose sensing and insulin delivery

In past few years, phenylboronic acids (PBAs) have attracted researchers attention due to their unique responsiveness towards diol-containing molecules such as glucose. This property allows hydrogel-bearing PBAs potentially to serve as an alternative for glucose-sensing and insulin-delivery systems. This review provides an outlook on the binding mechanism of PBA moieties with diols and the approaches to increase their binding selectivity and response for glucose molecules. The preparation methods and strategies of hydrogel-bearing PBA moieties along with their properties are discussed. In the last section, their applications in glucose-sensing and insulin-regulatory systems are described.

Preparation, properties and challenges of the microneedles-based insulin delivery system

Microneedle technology relates to pharmacy, polymer chemistry and micromachining. Microneedle can effectively deliver insulin into systemic circulation across the skin. This process does not affect the activity of insulin. Compared to subcutaneous injection, microneedles cause less pain for their special structure. This review thoroughly discusses the preparation technologies of the microneedles-based insulin delivery system including solid, hollow, dissolving, phase transition, glucose-responsive microneedle patches. In the meantime, the properties, challenges and clinical/commercial status of the microneedles-based insulin delivery system are also discussed in this review.

Recent progress in synthesis of antifogging agents and their application to agricultural films: a review

Antifogging agents are very important for use on agricultural films. Fogging reduces crop yield and causes other negative effects. To overcome fogging problems on agricultural films, several approaches including surface coating and reactive extrusion methods have been used. To date, researchers have designed a variety of agents to prepare antifogging films. The mechanism and rules for the composition of such agents have also been reported. However, reported antifogging films do not exhibit satisfactory results. Therefore, antifogging methods require further improvement. In this review, different preparation methods for antifogging agents and films are summarized, along with the advantages and disadvantages of each method. Moreover, test methods for antifogging performance are introduced.