Advanced development of chitosan hydrogels has led to new drug delivery systems that can release their active ingredients in response to environmental stimuli. This review considers more recent ...investigation of chitosan hydrogel preparations and the application of these preparations for drug delivery in wound dressings. Applications and structural characteristics of different types of active ingredients, such as growth factors, nanoparticles, nanostructures, and drug loaded chitosan hydrogels are summarized.
•This review presents the application of chitosan as an effective material for biomedical applications.•Various preparation methods of chitosan hydrogels have been reviewed.•Chitosan hydrogels incorporated with growth factors accelerate treating chronic wounds.•Nanostructure drugs as a new growing field have significant effect on wound healing.•Essential oils and other chemical drugs are also reviewed in this paper.
Cyclodextrins (CDs) are a unique class of molecules that are naturally available via degradation of starchy molecules. Their toroidal structure and abundant presence of hydroxyl groups have given ...scientists exceptional leverage resulting in synthesizing novel molecules for applications ranging from food packaging, controlled release of small molecules, antibacterial coating, agriculture, and air and water filtration. With the advent of nanotechnology, CDs have positioned itself in a variety of forms such as their ability to act as capping/reducing agents for metallic nanoparticles, or form stable nanofibers or nanoparticles or nano micelles, which can be subsequently utilized for sophisticated applications. In this review, we summarize researches on the presence of CDs in various aspects of nanotechnology ranging from nanoparticles, nanorods, nanomicelles, to nanofibers. In addition, through this review, we provide state-of-the-art applications that are being carried out using these nanostructures.
Due to the promising properties of chitosan for biomedical engineering applications like biodegradability, biocompatibility, and non-toxicity, it is one of the most interesting biopolymers in this ...field. Therefore, Chitosan and its derivatives have attracted great attention in vast variety of biomedical applications. In the current paper, different types of chitosan-based bioadhesives including passive and active and their different types of external stimuli response structure such as thermo, pH and Light responsive systems are discussed. Different bioadhesives mechanisms with chitosan as an adhesive agent or main polymer component and some examples were also presented. Chitosan based bioadhesives and their potential biomedical applications in drug delivery systems, suture less surgery, wound dressing and hemostatic are also discussed. The results confirmed wound healing, hemostatic and bioadhesion capabilities of the chitosan bioadhesives and its great potential for biomedical applications.
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In honor of Prof. Thorsteinn Loftsson’s 70th birthday, we offer this personal review of our work using cyclodextrins (CDs) complexed with a variety of active ingredients, including ...pharmaceuticals, for the purpose of improving their delivery to polymer materials, e.g., fibers, films, hydrogels, etc. Using the affinity of CDs to host and form non-covalent inclusion complexes (ICs) with guest molecules, including a variety of high molecular weight polymers, it is possible to readily deliver these guest molecules into polymer materials via either melt or solution processing of their crystalline or soluble guest molecule-CD-ICs or -rotaxanes. This provides the following advantages: i. CDs are non-toxic, implantable, and biodegradable and have earned the GRAS rating from the FDA. ii. Guest molecules, even those that are neat liquids, can form solid crystalline CD-ICs that are thermally stable to ~ 200 °C and above. This approach permits facile melt-processing into polymer materials for delivery without migration, loss, or degradation of the active guest ingredient. iii. For guests harmful and toxic to their users and the environment, delivery in the form of crystalline CD-ICs can limit any contact with and release of the included toxic guests before they function and are used. iv. It has been demonstrated that, by simple precipitation methods, neat as-received CDs that adopt cage crystal structures can be readily transformed to their columnar crystal structures containing only water in their channels, which can be easily displaced by small molecule, as well as polymer guests. v. Guest-CD-rotaxanes are water soluble, they protect the threaded guest from sources of degradation, and the CD hydroxyl groups may be modified to direct the guest-CD-rotaxane to specific substrates. For these reasons, here we summarize our contributions to the study of CD inclusion and delivery of a variety of guest molecules, including antibacterials, spermicides, insecticides, flame retardants, and dyes, that can more usefully functionalize polymer materials.
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•pH sensitive polyvinyl alcohol and chitosan hydrogel wound dressings containing cyclodextrin inclusion compounds (CD-ICs) were developed by freeze-thaw method.•The structures of the ...hydrogels were characterized by FTIR, optical and scanning electron microscopy.•The MTT assay indicated low-toxicity of the prepared hydrogels and the in vitro test showed antibacterial activity of all prepared hydrogels against E. coli and S. aurous.•Different mathematical models were applied for evaluating drug release mechanism and kinetic.•The prepared hydrogels might be used as potential wound dressings to improve wound healing.
Hydrogels, based on polysaccharides such as chitosan have found various applications as drug delivery carriers. Three different preparations of pH sensitive chitosan/polyvinyl alcohol hydrogels containing inclusion compounds of thyme oil with methyl-β-, hydroxypropyl-β- and γ-cyclodextrin were developed by using a controlled, bio-compatible and low cost method based on freeze-thaw cycling. The structures and morphology of the hydrogels were characterized by FTIR, optical and scanning electron microscopy. Stable hydrogels of chitosan and polyvinyl alcohol had good mechanical properties and swelling ratios. The water vapor transmission rates of the hydrogels were all in the range of an ideal wound dressing. Encapsulation and release of thyme oil-cyclodextrin inclusion compounds (TM-CD-ICs) in the hydrogels were detected and followed by UV spectroscopy and different mathematical models were applied for evaluating the drug release mechanisms. Hydrogels loaded with TM-CD-ICs had slower and more controlled drug release. The antibacterial activity of the samples was studied by counting the number of surviving both gram-negative and gram-positive bacteria in a broth medium and the results showed antibacterial activity of all prepared hydrogels, especially those containing TM-γCD-ICs. The MTT assay indicated more cell viability of TM-γCD-ICs hydrogels in comparison with those containing β-cyclodextrin inclusion compounds (TM-βCD-ICs hydrogels). Cell attachment study showed great biocompatibility of TM-γCD-ICs hydrogels. Finally, the modified hydrogels can be used in different biomedical applications, such as wound dressings for improving the wound healing process and in drug delivery systems.
Cyclodextrins are oligosaccharides that have truncated cone like structures, making them capable of forming non-covalent bonds with a large variety of molecules (especially hydrophobic molecules). ...Additionally, as the outer rims of their truncated cones are lined with several hydroxyl groups, secondary interactions with and functionalization of these hydroxyl groups are also possible. Current techniques available to analyze and characterize these interactions, although somewhat limited, can be accomplished by judicious selection of analytical tools. However, for emerging applications, the currently utilized techniques summarized in this review may not be sufficient. The purpose of this review is to provide an overview, including their possible limitations, of current techniques commonly employed to investigate such interactions. In view of CD-based materials for emerging applications, wherever possible, analytical tools used for these studies are also discussed.
An alkane-like contaminant was isolated from as-received commercial PMMA by forming a conventional urea inclusion compound during the preparation of a PMMA-urea complex. The contaminant, likely a ...surfactant used in the emulsion polymerization of PMMA, acts as a plasticizer in the commercial PMMA sample. After removing the contaminant, the resultant coalesced-PMMA showed an approximately 30 °C higher glass transition temperature than the as-received PMMA. Forming the PMMA-urea complex and then removing urea and the contaminant together with methanol can purify commercial PMMA and “unmask” its true Tg. Considering the large amount of research performed on PMMA blends, thin films, and nanocomposites, often with inconsistent or conflicting results, we believe the purity of some PMMAs used in past and future studies needs to be examined. Because commercial polystyrene is also obtained by emulsion polymerization and its blends, thin films, and nanocomposites have also been extensively studied, a similar contaminant may be affecting its behavior.
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•An alkane-like contaminant was found in the as-received PMMA samples.•The contaminant acted as a plasticizer and masked the true Tg of PMMA.•A purification method was developed for the contaminant removal.
I summarize work conducted in our laboratories over the past 30 years using small host molecules to restructure polymer materials at the nanometer level. Certain small molecules, such as the cyclic ...starches cyclodextrins (CDs) and urea (U) can form non-covalent crystalline inclusion compounds (ICs) with a range of guest molecules, including many polymers. In polymer-CD- and -U-ICs, guest polymer chains reside in narrow channels created by the host molecule crystals, where they are separated and highly extended. When the host crystalline lattice is carefully removed, the guest polymer chains coalesce into a bulk sample with an organization that is distinct from that normally produced from its melt or from solution. Amorphous regions of such coalesced polymer samples have a greater density, likely with less chain entanglement and more chain alignment. As a consequence, after cooling from their melts, coalesced amorphous polymers show glass-transition temperatures (T
s) that are elevated above those of samples prepared from their solutions or melts. Upon cooling from their melts, coalesced samples of crystallizable polymers show dramatically-increased abilities to crystallize more rapidly and much closer to their melting temperatures (T
s). These unique behaviors of polymers coalesced from their CD- and U-ICs are unexpectedly resistant to extended annealing above their T
s and T
s. Taking advantage of this behavior permits us to create polymer materials with unique and improved properties. Among these are amorphous polymers with elevated T
s and semi-crystalline polymers with finer more uniform morphologies. Improved mechanical properties can be achieved through self-nucleation with small amounts of the same polymer made rapidly crystallizable through coalescence from its CD- or U-IC. This can lead to single polymer composites with as-received polymer matrices and self-nucleated reinforcements. Through simultaneous formation and subsequent coalescence from their common CD-ICs, stable well-mixed blends can be achieved between any two or more polymers, despite their inherent immiscibilities. Such coalesced and well-mixed blends are also resistant to phase segregation when heated for extensive periods well above their T
s and T
s.
Chitosan‐based hydrogels involving γ‐cyclodextrin inclusion compounds of thyme oil were prepared by freeze–thaw cycling method. Clinoptilolite as a natural zeolite was added to investigate its ...effects on the structural, mechanical, and drug release behaviors of the hydrogels. Zeolite compressed the structure and improved mechanical properties, which decreased swelling values. Release of thyme oil in prepared hydrogels were investigated by UV spectroscopy and drug release mechanism was evaluated by applying various mathematical methods. Rates of water vapor transmission of the samples were calculated as 2247–2998 g m−2 day−1 which are all in the range of an ideal wound dressing. Hydrogels with clinoptilolite had slower drug release (from 56% to 24% for hydrogels containing zeolite 1%) in comparison with that of without zeolite. Based on MTT assay, samples were low‐toxic. Obtained results suggest that drug loaded hydrogels can be applied in biomedical field including drug delivery systems and wound dressings.
Chitosan‐based hydrogels involving γ‐cyclodextrin inclusion compounds of thyme oil were prepared by freeze–thaw cycling method. Clinoptilolite as a natural zeolite was added to investigate its effects on the structural, mechanical, and drug release behaviors of the hydrogels. Obtained results suggest that drug loaded hydrogels can be applied in biomedical field including drug delivery systems and wound dressings.
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