Glutaraldehyde cross-linked chitosan microspheres as a long acting biodegradable drug delivery vehicle: studies on the in vitro release of mitoxantrone and in vivo degradation of microspheres in rat muscle

Adsorptive chito-beads for control of membrane fouling

Chitosan has excellent antimicrobial, adsorption, heavy metal removal, and adhesion properties, making it a good substitute for microplastic-based cleaners. Here, chitosan microbeads (chito-beads) of various sizes ranging from 32 μm to 283 μm were prepared via emulsion using a liquid on oil method and the feasibility of using them as an essential constituent in a chemical cleaning solution for a reverse-osmosis (RO) membrane-fouling-control process was assessed. Prior to the assessment the cleaning efficiency of a solution containing chito-beads, the interaction energy between chitosan and a representative organic foulant (humic acid (HA)) in a RO membrane fouling was analyzed using colloidal atomic force microscopy, and the strongest attraction between chitosan and HA was observed in an aqueous solution. When comparing the membrane cleaning efficiency of cleaning solutions with and without chito-beads, smaller chito-beads (32 μm and 70 μm) were found to have higher cleaning efficiency. Applications of chito-beads to the membrane cleaning process can enhance the cleaning efficiency through the physicochemical interaction with organic foulants. This study can widen the use of chito-beads as an additive to membrane chemical cleaning solutions to control membrane fouling in other membrane processes as well.

Multifunctional and theranostic hydrogels for wound healing acceleration: An emphasis on diabetic-related chronic wounds

Hydrogels represent intricate three-dimensional polymeric structures, renowned for their compatibility with living systems and their ability to naturally degrade. These networks stand as promising and viable foundations for a range of biomedical uses. The practical feasibility of employing hydrogels in clinical trials has been well-demonstrated. Among the prevalent biomedical uses of hydrogels, a significant application arises in the context of wound healing. This intricate progression involves distinct phases of inflammation, proliferation, and remodeling, often triggered by trauma, skin injuries, and various diseases. Metabolic conditions like diabetes have the potential to give rise to persistent wounds, leading to delayed healing processes. This current review consolidates a collection of experiments focused on the utilization of hydrogels to expedite the recovery of wounds. Hydrogels have the capacity to improve the inflammatory conditions at the wound site, and they achieve this by diminishing levels of reactive oxygen species (ROS), thereby exhibiting antioxidant effects. Hydrogels have the potential to enhance the growth of fibroblasts and keratinocytes at the wound site. They also possess the capability to inhibit both Gram-positive and Gram-negative bacteria, effectively managing wounds infected by drug-resistant bacteria. Hydrogels can trigger angiogenesis and neovascularization processes, while also promoting the M2 polarization of macrophages, which in turn mitigates inflammation at the wound site. Intelligent and versatile hydrogels, encompassing features such as pH sensitivity, reactivity to reactive oxygen species (ROS), and responsiveness to light and temperature, have proven advantageous in expediting wound healing. Furthermore, hydrogels synthesized using environmentally friendly methods, characterized by high levels of biocompatibility and biodegradability, hold the potential for enhancing the wound healing process. Hydrogels can facilitate the controlled discharge of bioactive substances. More recently, there has been progress in the creation of conductive hydrogels, which, when subjected to electrical stimulation, contribute to the enhancement of wound healing. Diabetes mellitus, a metabolic disorder, leads to a slowdown in the wound healing process, often resulting in the formation of persistent wounds. Hydrogels have the capability to expedite the healing of diabetic wounds, facilitating the transition from the inflammatory phase to the proliferative stage. The current review sheds light on the biological functionalities of hydrogels, encompassing their role in modulating diverse mechanisms and cell types, including inflammation, oxidative stress, macrophages, and bacteriology. Additionally, this review emphasizes the significance of smart hydrogels with responsiveness to external stimuli, as well as conductive hydrogels for promoting wound healing. Lastly, the discussion delves into the advancement of environmentally friendly hydrogels with high biocompatibility, aimed at accelerating the wound healing process.

Rapid Synthesis of Robust Antibacterial and Biodegradable Hydrogels via Frontal Polymerization

Chitosan (CS) is widely used in biomedical hydrogels due to their similarity to extracellular matrix. However, the preparation method of CS-based hydrogel suffers the drawbacks of tedious operation, time-consuming and energy consumption. Thus, there is an urgent need to develop a rapid synthesis pathway towards hydrogels. In this work, we used a modified CS as a cross-linking agent and acrylic acid (AA) as monomer to prepare a hydrogel through frontal polymerization (FP), which facilitates a facile and rapid method achieved in several minutes. The occurrence of pure FP was confirmed via the frontal velocity and temperature profile measurement. In addition, the as-prepared hydrogel shows excellent mechanical strength up to 1.76 MPa, and the Young's modulus (ranging from 0.16 to 0.56 MPa) is comparable to human skin. The degradation mechanism is revealed by the micro-IR images through the distribution of the functional groups, which is attributed to the breakage of the ether bond. Moreover, the hydrogel exhibits excellent degradability, biocompatibility and antibacterial properties, offering great potentials in tissue engineering. We believe this work not only offers a facile and rapid FP method to fabricate a robust degradable hydrogel, but also provides an effective pathway for the investigation of the degradation mechanism at the chemical bond analysis level.

Recent developments in natural biopolymer based drug delivery systems

Targeted delivery of drug molecules to diseased sites is a great challenge in pharmaceutical and biomedical sciences. Fabrication of drug delivery systems (DDS) to target and/or diagnose sick cells is an effective means to achieve good therapeutic results along with a minimal toxicological impact on healthy cells. Biopolymers are becoming an important class of materials owing to their biodegradability, good compatibility, non-toxicity, non-immunogenicity, and long blood circulation time and high drug loading ratio for both macros as well as micro-sized drug molecules. This review summarizes the recent trends in biopolymer-based DDS, forecasting their broad future clinical applications. Cellulose chitosan, starch, silk fibroins, collagen, albumin, gelatin, alginate, agar, proteins and peptides have shown potential applications in DDS. A range of synthetic techniques have been reported to design the DDS and are discussed in the current study which is being successfully employed in ocular, dental, transdermal and intranasal delivery systems. Different formulations of DDS are also overviewed in this review article along with synthesis techniques employed for designing the DDS. The possibility of these biopolymer applications points to a new route for creating unique DDS with enhanced therapeutic qualities for scaling up creative formulations up to the clinical level.

Polysaccharides and lipoproteins as reactants for the synthesis of pharmaceutically important scaffolds: A review

The growing number of diseases in the past decade has once again highlighted the need for extensive research on the development of novel drugs. There has been a major expansion in the number of people suffering from malignant diseases and types of life-threatening microbial infections. The high mortality rates caused by such infections, their associated toxicity, and a growing number of microbes with acquired resistance necessitate the need to further explore and develop the synthesis of pharmaceutically important scaffolds. Chemical entities derived from biological macromolecules like carbohydrates and lipids have been explored and observed to be effective agents in the treatment of microbial infections and diseases. These biological macromolecules offer a variety of chemical properties that have been exploited for the synthesis of pharmaceutically relevant scaffolds. All biological macromolecules are long chains of similar atomic groups which are connected by covalent bonds. By altering the attached groups, the physical and chemical properties can be altered and molded as per the clinical applications and needs, this ring them potential candidates for drug synthesis. The present review establishes the role and significance of biological macromolecules by articulating various reactions and pathways reported in the literature.

Preparation of inhalable N-acetylcysteine-loaded magnetite chitosan microparticles for nitrate adsorption in particulate matter

Airborne particulate matter has been designated as a class 1 carcinogen by the World Health Organization. Nitrate is a toxic substance that accounts for a large proportion of particulate matter, and nitrate toxicity has long been reported. In this study, we aimed to optimize the adsorption and removal of particulate matter containing nitrate for effective elimination by the lungs. To this end, particles were designed to optimize the inhalation and removal efficiencies. These particles were prepared as chitosan-based particles containing N-acetylcysteine by using emulsion diffusion methods. Chitosan adsorbs nitrate, while N-acetylcysteine dissolves mucus. This removal mechanism has been found to occur in various in vitro models that mimic respiratory environments and in vivo models. In particular, the removal of exogenous substances, such as particulate matter, by the motility of respiratory cilia through mucolytic effect was investigated. This new approach for the adsorption and elimination of toxic substances entering the lungs represents an alternative defense mechanism against exposure to nitrates from air pollution.

A Critical Review of Analytical Applications of Chitosan as a Sustainable Chemical with Functions Galore

Biomass and biowastes stand as sustainable and cost-effective environmentally benign alternative feedstock. Chitosan is a biocompatible, bioactive, and biodegradable biopolymer derived from chitin to achieve eight aspects out of the 12 green chemistry principles. Chitosan got significant attention in several fields including chemical analysis, in addition to chemical functionally, which enabled its use as adsorbent and its structural crosslinking using various crosslinkers. The physicochemical, technological, and optical properties of chitosan have been extensively exploited in analysis. Mainly, deacetylation degree and molecular weight are controlling its properties and hence controlling its functions. This review presents a structure, properties, and functions relationships of chitosan. It also aims to provide an overview of the different functions that chitosan can serve in each analytical technique such as supporting matrix, catalyst…etc. The contribution of chitosan in improving the ecological performance is discussed in each technique.

Emerging Fabrication Strategies of Hydrogels and Its Applications

Recently, hydrogels have been investigated for the controlled release of bioactive molecules, such as for living cell encapsulation and matrices. Due to their remote controllability and quick response, hydrogels are widely used for various applications, including drug delivery. The rate and extent to which the drugs reach their targets are highly dependent on the carriers used in drug delivery systems; therefore the demand for biodegradable and intelligent carriers is progressively increasing. The biodegradable nature of hydrogel has created much interest for its use in drug delivery systems. The first part of this review focuses on emerging fabrication strategies of hydrogel, including physical and chemical cross-linking, as well as radiation cross-linking. The second part describes the applications of hydrogels in various fields, including drug delivery systems. In the end, an overview of the application of hydrogels prepared from several natural polymers in drug delivery is presented.

Composition of Piperine with Enteric-Coated Chitosan Microspheres Enhances the Transepithelial Permeation of Curcumin in Sheep Intestinal Mucosa and Caco-2 Cells

Objectives The purpose of this study was to investigate the efficacy of enteric-coated chitosan microspheres with herbal bioenhancer, piperine, as a suitable composition for improving the permeation of curcumin through biological membranes using suitable ex vivo models.

Material and Methods Chitosan microspheres of curcumin and piperine were prepared by an emulsion cross-linking method using glutaraldehydes the cross-linking agent and characterized for size, shape, entrapment efficiency, mucoadhesion, and in vitro release. The effect of piperine on the permeation of curcumin through excised sheep intestinal mucosa and Caco-2-cell monolayer was investigated.

Statistical Analysis The data from permeation studies were analyzed by Student's t-test using Statistical Package for the Social Sciences (SPSS) software (SPSS, Chicago, IL, United States) with p-values <0.05 indicating statistical significance.

Results The formulations showed mucoadhesion for a period of more than 6 hours which was influenced by the chitosan content. The rate of drug release of uncoated formulation followed first-order kinetics, and the mechanism of release was non-Fickian transport. Optimized formulation was coated with a pH-sensitive polymer, Eudragit S-100, by a solvent evaporation technique in different concentrations and evaluated for ex vivo permeation through sheep intestinal mucosa and Caco-2-cell monolayer. Scanning electron microscopy images of the optimized coated formulation showed spherical particles with smooth surfaces. The calculated permeation flux and permeability coefficient of curcumin from microspheres were at least 20% greater in the presence of piperine through the intestinal mucosa and 30% through the Caco-2-cell monolayer model. The permeability coefficient of curcumin from microspheres with piperine was 1.93 × 10 to 5 cm/sec and significantly greater (p < 0.05) than that of microspheres devoid of piperine and from aqueous dispersion (p < 0.005).

Conclusion The study confirmed the contribution of piperine and mucoadhesive microspheres toward improved permeation of curcumin through biological membranes, thereby providing an approach that has the potential of increasing transport through intestinal epithelial cells and possibly enhancing the oral bioavailability of this drug.

Crosslinked chitosan/poly(vinyl alcohol) nanofibers functionalized by ionic liquid for heavy metal ions removal

Nanostructure adsorbents namely nanofibers have been demonstrated to have a high adsorption rate and are efficient to treat wastewater. Herein, chitosan/poly(vinyl alcohol) (PVA) blend nanofiber membranes prepared by electrospinning method were crosslinked using glutaraldehyde and functionalized with 1-allyl-3-methylimidazolium chloride to be used as a potential bio-sorbent for heavy metal ions removal. The chitosan was first hydrolyzed before electrospinning with PVA, followed by crosslinking and further functionalized by ionic liquid to overcome the limitation of chitosan which has low adsorption capacity and unsuitable physical properties for the adsorption process. The morphology and the chemical bond formed were investigated by using field emission scanning electron microscopy with energy dispersive x-ray spectroscopy (FESEM-EDX) and Fourier transform infrared (FTIR) showing that the hydrolyzed chitosan/PVA nanofiber membranes were successfully crosslinked and functionalized. The synthesized adsorbent was evaluated in pure heavy metal ions solutions namely Pb(II), Mn(II), and Cu(II) and shown best performance for Pb(II) ions. The highest adsorption capacity recorded for Pb(II) ions was 166.34 mg/g and are well fitted to the Freundlich isotherm model and pseudo-second-order kinetic model to describe the adsorption equilibrium and kinetic rate of the Pb(II) uptake, respectively. The synthesized adsorbent clearly shows a great capability to remove Pb(II) ions.

Hydrogels Classification According to the Physical or Chemical Interactions and as Stimuli-Sensitive Materials

Hydrogels are attractive biomaterials with favorable characteristics due to their water uptake capacity. However, hydrogel properties are determined by the cross-linking degree and nature, the tacticity, and the crystallinity of the polymer. These biomaterials can be sorted out according to the internal structure and by their response to external factors. In this case, the internal interaction can be reversible when the internal chains are led by physicochemical interactions. These physical hydrogels can be synthesized through several techniques such as crystallization, amphiphilic copolymers, charge interactions, hydrogen bonds, stereo-complexing, and protein interactions. In contrast, the internal interaction can be irreversible through covalent cross-linking. Synthesized hydrogels by chemical interactions present a high cross-linking density and are employed using graft copolymerization, reactive functional groups, and enzymatic methods. Moreover, specific smart hydrogels have also been denoted by their external response, pH, temperature, electric, light, and enzyme. This review deeply details the type of hydrogel, either the internal structure or the external response. Furthermore, we detail some of the main applications of these hydrogels in the biomedicine field, such as drug delivery systems, scaffolds for tissue engineering, actuators, biosensors, and many other applications.

Influence of molecular interactions on structure, controlled release and cytotoxicity of curcumin encapsulated chitosan - Silica nanostructured microspheres

Curcumin possesses numerous medicinal benefits including anti-cancer and anti-viral properties. However, its wide scale use as a drug is often hindered owing to the dearth of suitable drug-delivery systems which can solubilise it for long-term sustained-release and safeguard its beneficial properties. In this work, a fast, one-step method, employing evaporation induced assembly of colloids, has been employed for the synthesis of curcumin encapsulated organic-inorganic hybrid micron-sized spheres. Detailed physical properties of the microspheres, with scaffolds of silica nanoparticles (∼8.5 nm) cross linked by chitosan, are studied to trace the underlying mechanism of structural assembly in such systems, by tuning the polymer matrix with solubilizing agents, DMSO and Tween 20. A systematic modification in the hydrogen bonding network, conformations and interactions between macromolecules is revealed upon tuning the organic matrix. This in turn is found to control the assembly vis-à-vis the granular morphology, drug entrapment and packing fraction of nanoparticles in the microspheres, which have direct influence on the biological properties. Consequently, the microspheres are found to follow a first order drug release kinetics with a tunable rate constant which follows the ordering of packing fraction of silica nanoparticles in the micro-granules. A sustained curcumin release for a period extending up to 24 h has been achieved. Further studies using human lung and cervical cancer cell lines assert good anti-cancer properties of these nanostructured microspheres in cancer cells, while showing no toxicity towards normal cells. Thus, such hybrid organic-inorganic formulations achieved using multi-component colloidal assembly approach, with enhanced stability against degradation, are promising candidates for future clinical applications of water-insoluble drugs.

Comprehensive Review on Hydrogels

The conventional drug delivery systems have a long list of issues of repeated dosing and toxicity arising due to it. The hydrogels are the answer to them and offer a result that minimizes such activities and optimizes therapeutic benefits. The hydrogels proffer tunable properties that can withstand degradation, metabolism, and controlled release moieties. Some of the areas of applications of hydrogels involve wound healing, ocular systems, vaginal gels, scaffolds for tissue, bone engineering, etc. They consist of about 90% of the water that makes them suitable bio-mimic moiety. Here, we present a birds-eye view of various perspectives of hydrogels, along with their applications.

Antibacterial Chitosan Nanofiber Thin Films with Bacitracin Zinc Salt

Chitosan nanofiber has a highly uniform structure of 20–50 nm in diameter and shows high dispersibility in water due to its submicron size and high surface-to-volume ratio. The stacked nanofibers film is useful for breathability because it has a gap with a size of several tens of nm or more. However, the chemical bonds between the nanofibers cannot be broken during use. In this study, the thin films were obtained by filtration of chitosan nanofibers and 3-glycidoxypropyltrimethoxysilane (GPTMS) mixture. The addition of GPTMS changed the wettability, mechanical property and stability in water of the thin films. Bacitracin zinc salt (BZ) has been used for the localized dermatological medicines and loaded in the films. BZ interacted electrostatically with the thin films matrix and the release of BZ was controlled by the amount of GPTMS. A higher released amount of BZ showed higher antibacterial effects toward S. aureus. The film was also tested their toxicity by L929 fibroblasts. The release of less than 11.9 μg of BZ showed antibacterial effects, but were not toxic for fibroblast cells.

The Development, Evaluation, and Antioxidant Activity Analysis of Chitosan Microcapsules Containing Red Ginger Oleoresin with Sodium Tripolyphosphate Prepared by Emulsion Cross-linking Technique

In this study, chitosan-based carrier of red ginger oleoresin was prepared using the emulsion cross-linking technique with sodium tripolyphosphate (TPP) as a cross-linking agent. The effect of chitosan and TPP concentration, as well as pH on the encapsulation efficiency, particle size and characterization of chitosan microcapsule was determined. The antioxidant activity of microcapsules was analyzed. Chitosan microcapsules containing red ginger oleoresin were produced although with non-smooth surfaces.

Leveraging advances in chemistry to design biodegradable polymeric implants using chitosan and other biomaterials

The metamorphosis of biodegradable polymers in biomedical applications is an auspicious myriad of indagation. The utmost challenge in clinical conditions includes trauma, organs failure, soft and hard tissues, infection, cancer and inflammation, congenital disorders which are still not medicated efficiently. To overcome this bone of contention, proliferation in the concatenation of biodegradable materials for clinical applications has emerged as a silver bullet owing to eco-friendly, nontoxicity, exorbitant mechanical properties, cost efficiency, and degradability. Several bioimplants are designed and fabricated in a way to reabsorb or degrade inside the body after performing the specific function rather than eliminating the bioimplants. The objective of this comprehensive is to unfurl the anecdote of emerging biological polymers derived implants including silk, lignin, soy, collagen, gelatin, chitosan, alginate, starch, etc. by explicating the selection, fabrication, properties, and applications. Into the bargain, emphasis on the significant characteristics of current discernment and purview of nanotechnology integrated biopolymeric implants has also been expounded. This robust contrivance shed light on recent inclinations and evolution in tissue regeneration and targeting organs followed by precedency and fly in the ointment concerning biodegradable implants evolved by employing fringe benefits provided by 3D printing technology for building tissues or organs construct for implantation.

Marine-Derived Polymeric Materials and Biomimetics: An Overview

The review covers recent literature on the ocean as both a source of biotechnological tools and as a source of bio-inspired materials. The emphasis is on marine biomacromolecules namely hyaluronic acid, chitin and chitosan, peptides, collagen, enzymes, polysaccharides from algae, and secondary metabolites like mycosporines. Their specific biological, physicochemical and structural properties together with relevant applications in biocomposite materials have been included. Additionally, it refers to the marine organisms as source of inspiration for the design and development of sustainable and functional (bio)materials. Marine biological functions that mimic reef fish mucus, marine adhesives and structural colouration are explained.

Temperature-dependent mucosal permeation kinetics of stigmasterol microspheres: In vivo mice model antioral candidiasis study

Evaluation of mucosal permeation of stigmasterol from the glutaraldehyde cross linked chitosan microspheres at increasing experimental temperatures was performed. The activation energy of permeation, partition, and diffusion were estimated to understand the permeation kinetic with respect to the temperature. The formulation depicting least activation energy possessed the increased permeation thresholds of drug at the site of application. The encapsulation efficacy and mucoadhesive strength were found to be directly proportional to the polymer-emulsifier ratio. Decreased intensity in crystallography directed the molecular dispersion of microencapsulated drug. The depleted enthalpic phase transition in thermogram affirmed the stigmasterol encapsulation. The sphericity and the size of microspheres were determined by scanning electron photo micrograph. The in vivo quantification of oral Candida infection with different statistical approach and histopathological observation of infected tongue of mice on treatment with the stigmasterol encapsulated microspheres showed significant anti oral candidiasis activity by reduction of fungal colony count and recovery of papillae, reorganization of basal cell layer and newly formed papillae during 21-28 days of treatment.

Effects of chitin and chitosan from cricket and shrimp on growth and carcass performance of broiler chickens

Majority of the studies on the effect of chitin and chitosan on growth and carcass characteristics of broiler chickens has concentrated more on shrimp chitin and shrimp chitosan, and often with contradictory results. Therefore, the objective of this present study is to evaluate and compare the effect of dietary chitin and chitosan from cricket and shrimp on growth performance, carcass, and organ characteristics of broiler chickens. One hundred fifty-day-old male Cobb500 broiler chicks of similar average weight were randomly allotted into one of the five dietary treatments with three replicates. Treatment 1 (T1) chicks were fed basal diet only (control), treatment 2 and 3 (T2 and T3) chicks were given basal diet with 0.5 g/kg diet of cricket chitin and cricket chitosan, respectively, while treatment 4 and 5 (T4 and T5) chicks were served basal diet with 0.5 g/kg diet of shrimp chitin and shrimp chitosan respectively. No significant variation occurred between cricket chitin and shrimp chitin, although data on growth performance were higher in cricket chitin, but growth performance varied significantly between cricket chitosan and shrimp chitosan. This study revealed that cricket chitin at 0.5 g/kg significantly improved growth performance, carcass quality, and organ characteristics of broilers more than chitosan. Birds fed basal diet alone, although gained more weight, also accumulated more fat having the poorest feed conversion ratio (FCR) and the highest mortality. However, carcass of birds fed cricket chitin was the leanest and thus economically beneficial as they consumed the least amount of feed with the best FCR.

Preparation of Chitosan Microcapsules Containing Red Ginger Oleoresin Using Emulsion Crosslinking Method

BACKGROUND:

Encapsulation is one of the methods used to trap active ingredients in the wall material of microparticles.

AIM:

The aim of this study was to evaluate the encapsulation of red ginger oleoresin using an emulsion crosslinking method with chitosan as the wall material.

METHODS:

Emulsions were formed of red ginger oleoresin with chitosan in concentrations of 1%, 2%, 3%, and 4% (w/v), respectively. The emulsions were then mixed with corn oil and stirred for one hour to obtain a second set of emulsions, and glutaraldehyde saturated toluene (GST) was added dropwise in quantities of 20, 10, 6.7, and 5 ml, respectively. This was followed by the addition of 2 ml of 25% glutaraldehyde and the emulsions were stirred for two hours. The resulting microcapsules were washed with petroleum ether followed by hexane and then dried in an oven at 70oC.

RESULTS:

The emulsion crosslinking method used to trap the red ginger oleoresin in chitosan produced microcapsules of good spherical geometry with the mean diameter ranging from 75.61 ± 11.8 µm to 178.65 ± 40.7 µm. The highest yield was 98.93% and encapsulation efficiency was 83.1%. Thermogravimetric and differential thermal analysis showed that the melting point was at a temperature between 120 and 130oC.

CONCLUSION:

Chitosan concentration has little effect on encapsulation yield, whereas the amount of GST tends to strengthen the crosslinking bonds of chitosan and reduces the mean diameter of microspheres.

pH Variation as a Simple and Selective Pathway for Obtaining Nanoparticle or Nanocapsule Polysaccharides

The fabrication of polysaccharides to be nanoparticles or nanocapsules is quite specific due to various parameters and factors. The present work demonstrates a simple pathway to selectively prepare the ionic polysaccharide flakes to be nanoparticles or nanocapsules. The systematic studies on the model cases of cationic polysaccharide (i.e., chitosan) and anionic polysaccharide (i.e., alginate) confirm that p K_a is the key point to tune the polysaccharides to be nanoparticles or nanocapsules. When the ionic polysaccharides were in an oil/water emulsion system, the pH close to p K_a leads to the densely packed polysaccharide chains under the hydrogen bond networks, and as a result the cross-link occurs all through the chains to be nanoparticles. On the other hand, when pH was adjusted to the lower or higher than p K_a depending on the types of ionic polysaccharide, the polysaccharide chains are under charge-charge repulsive force, resulting in the alignment of polysaccharide chains to be hollow nanospheres, and at that time the cross-link initiates the formation of nanocapsules. The present work, for the first time, clarifies that pH variation is the key to selectively prepare nanoparticles or nanocapsules, and this is important for delivery systems, coatings, sensors, and so forth.

Synthesis and Preparation of Chitosan/Clay Microspheres: Effect of Process Parameters and Clay Type

This work aimed to prepare chitosan/clay microspheres, by the precipitation method, for use in drug carrier systems. The influence of the process parameters, particularly two airflows of the drag system (2.5 and 10 L·min-1) on the microspheres physical dimensions and properties, such as microstructure, degree of swelling and porosity were evaluated. The samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Water absorption and porosity tests were also performed. The results showed that the process parameters affected the size of the microspheres. The diameter, volume and surface area of the chitosan/clay microspheres decreased when they were prepared with the higher airflow of the drag system. The microspheres presented a porous microstructure, being the pore size, percentage of porosity and degree of swelling affected not only by the process parameters but also by the type of clay. Hybrids (chitosan/clay) with intercalated morphology were obtained and the hybrid prepared with montmorillonite clay at higher airflows of the drag system presented the greatest interlayer spacing and a more disordered morphology. Thus, it is certain that the chitosan/clay nanocomposite microspheres prepared with montmorillonite (CL clay) at higher airflows of the drag system can have good drug-controlled release properties.

Protein Based Nanostructures for Drug Delivery

The key role of protein based nanostructures has recently revolutionized the nanomedicine era. Protein nanoparticles have turned out to be the major grounds for the transformation of different properties of many conventional materials by virtue of their size and greater surface area which instigates them to be more reactive to some other molecules. Protein nanoparticles have better biocompatibilities and biodegradability and also have the possibilities for surface modifications. These nanostructures can be synthesized by using protein like albumin, gelatin, whey protein, gliadin, legumin, elastin, zein, soy protein, and milk protein. The techniques for their fabrication include emulsification, desolvation, complex coacervation, and electrospray. The characterization parameters of protein nanoparticles comprise particle size, particle morphology, surface charge, drug loading, determination of drug entrapment, and particle structure and in vitro drug release. A plethora of protein nanoparticles applications via different routes of administration are explored and reported by eminent researchers which are highlighted in the present review along with the patents granted for protein nanoparticles as drug delivery carriers.

Characterization of gelatin and chitosan scaffolds cross-linked by addition of dialdehyde starch

In this study the influence of the addition of dialdehyde starch on the properties of scaffolds based on gelatin and chitosan obtained by the freeze-drying method was investigated. In addition, the adhesion and proliferation of human osteosarcoma SaOS-2 cells on the obtained scaffolds was examined. Chitosan and gelatin were mixed in different weight ratios (75/25, 50/50, 25/75) with 1, 2 and 5 wt% addition of dialdehyde starch. The obtained scaffolds were subjected to mechanical testing, infrared spectroscopy, swelling measurements, low-pressure porosimetry and zeta potential measurement. Internal material structures were observed by scanning electron microscopy. The results showed that the cross-linking process occurred after the addition of dialdehyde starch and resulted in increased mechanical strength, swelling properties, zeta potential and porosity of studied materials. The attachment of SaOS-2 cells to all modified materials was better compared to an unmodified control and the proliferation of these cells was markedly increased on modified scaffolds.

Understanding the anticorrosive protective mechanisms of modified epoxy coatings with improved barrier, active and self-healing functionalities: EIS and spectroscopic techniques

The present investigation adopted long-term in-situ electrochemical and spectroscopic approaches to study the combined active, self-healing and passive protective mechanisms of a new class of innovative anti-corrosive coatings based on epoxy doped with clay nanotubes impregnated with active species for the protection of carbon steel in 3.5% NaCl solution. The suitability of the as-received clay nanotubes to encapsulate the active agents was confirmed by different spectroscopic measurements. Tube end stopper with Ferric ion and polymer encapsulation with chitosan cross-linked with glutaraldehyde were adopted to tunnel the release of the active agents loaded into the nanotubes. The improved passive barrier performances of the various innovative coatings were revealed by the electrochemical impedance spectroscopic, while their active feedback and self-healing abilities were revealed by the optical and spectroscopic techniques. The optical/spectroscopic techniques revealed the degree of pit formation at the steel/coating interface and the iron rust formation around the artificially marked defects, including the ability of the marked defects to self-heal over exposure times. Adhesion and impacts tests were adopted to compare the physical/mechanical properties of the various coatings. The results afforded insights into the effects of exposure time on the protective and failure behaviours of both the reference and modified coatings.

Effectiveness of tissue engineered based platelet gel embedded chitosan scaffold on experimentally induced critical sized segmental bone defect model in rat

BACKGROUND

Healing and regeneration of large bone defects are a challenging problem for reconstructive orthopedic surgeons.

PURPOSE

This study investigated the effectiveness of chitosan scaffold (CS), platelet gel (PG) and their combination (CS-PG) on healing process of an experimentally induced critical sized segmental bone defect model in rat.

METHODS

Fifty bilateral defects were created in the mid diaphysis of the radial bones of 25 Sprague-Dawley rats. The animals were randomly divided into five equal groups. The bone defects were either left untreated or treated with corticomedullary autograft, CS, PG or CS-PG. Plain radiographs were provided from the radial bones on weeks 2, 5, and 8 after injury. In addition, clinical examinations were done for the healing radial bones. The animals were euthanized after 8 weeks of injury, and their harvested samples were evaluated by gross morphology, histopathology, scanning electron microscopy, CT-scan, and biomechanical testing.

RESULTS

Compared with the defect group, the PG and autograft treated bone defects had significantly superior radiological scored values, bone volume and biomechanical performance which had positive correlation with their superior gross pathological, histopathological and ultra-structural features. Compared with the untreated defects, the PG and CS-PG treated defects showed significantly superior structural and functional properties so that PG had the highest value. In addition, CS had low value in bone regeneration. Although combination of CS and PG improved the healing efficacy of the CS, this strategy reduced the ability of PG to increase osteoconduction and osteoinduction during bone regeneration.

CONCLUSION

Application of PG alone enhanced bone healing and can be regarded as a promising option for bone tissue engineering in clinical settings. Chitosan was not effective in bone reconstruction surgery and further investigations should be conducted to find a suitable carrier for PG.

Magnetic stimuli-responsive chitosan-based drug delivery biocomposite for multiple triggered release

Stimuli-responsive biomaterials offer a unique advantage over traditional local drug delivery systems in that the drug elution rate can be controllably increased to combat developing symptomology or maintain high local elution levels for disease treatment. In this study, superparamagnetic Fe₃O₄ nanoparticles and the antibiotic vancomycin were loaded into chitosan microbeads cross-linked with varying lengths of polyethylene glycol dimethacrylate. Beads were characterized using degradation, biocompatibility, and elution studies with successive magnetic stimulations at multiple field strengths and frequencies. Thirty-minute magnetic stimulation induced a temporary increase in daily elution rate of up to 45% that was dependent on field strength, field frequency and cross-linker length. Beads degraded by up to 70% after 3 days in accelerated lysozyme degradation tests, but continued to elute antibiotic for up to 8 days. No cytotoxic effects were observed in vitro compared to controls. These promising preliminary results indicate clinical potential for use in stimuli-controlled drug delivery.

MRI traceability of superparamagnetic iron oxide nanoparticle-embedded chitosan microspheres as an embolic material in rabbit uterus

PURPOSE

We aimed to compare polyvinyl alcohol (PVA) particles with calibrated superparamagnetic iron oxide (SPIO) nanoparticle-loaded chitosan microspheres in a rabbit model, specifically regarding the relative distribution of embolic agents within the uterus based on magnetic resonance imaging (MRI) and pathological evaluation.

METHODS

Twelve New Zealand white rabbits underwent uterine artery embolization using either standard PVA particles (45-150 µm or 350-500 µm) or calibrated SPIO-embedded chitosan microspheres (45-150 µm or 300-500 µm). MRI and histopathological findings were compared one week after embolization.

RESULTS

Calibrated SPIO-loaded chitosan microspheres 45-150 µm in size were detected on T2-weighted images. On histological analysis, calibrated SPIO-embedded chitosan microspheres were found in both myometrium and endometrium, whereas PVA particles were found only in the perimyometrium or extrauterine fat pads. A proportional relationship was noted between the calibrated SPIO-embedded chitosan microsphere size and the size of the occluded artery.

CONCLUSION

Calibrated SPIO-embedded chitosan microspheres induced greater segmental arterial occlusion than PVA particles and showed great potential as a new embolic material. SPIO-embedded chitosan microspheres can be used to follow distribution of embolic particles through MRI studies.

Fabrication and evaluation of chitosan/NaYF4:Yb3+/Tm3+ upconversion nanoparticles composite beads based on the gelling of Pickering emulsion droplets

The rare earth ion doped upconversion nanoparticles (UCNPs) synthesized by hydrophobic organic ligands possess poor solubility and low fluorescence quantum yield in aqueous media. To conquer this issue, NaYF₄:Yb³⁺/Tm³⁺ UCNPs, synthesized by a hydrothermal method, were coated with F127 and then assembled with chitosan to fabricate the chitosan/NaYF₄:Yb³⁺/Tm³⁺ composite beads (CS/NaYF₄:Yb³⁺/Tm³⁺ CBs) by Pickering emulsion system. The characterization results revealed that the as-synthesized NaYF₄:Yb³⁺/Tm³⁺ UCNPs with an average size of 20nm exhibited spherical morphology, high crystallinity and characteristic emission upconversion fluorescence with an overall blue color output. The NaYF₄:Yb³⁺/Tm³⁺ UCNPs were successfully conjugated on the surface of chitosan beads by the gelling of emulsion droplets. The resultant CS/NaYF₄:Yb³⁺/Tm³⁺ CBs showed good upconversion luminescent property, drug-loading capacity, release performance and excellent biocompatibility, exhibiting great potentials in targeted drug delivery and tissue engineering with potential tracking capability and lasting release performance.

Perspectives on: Chitosan Drug Delivery Systems Based on their Geometries

Chitosan is a natural polymer that has many physicochemical (polycationic, reactive OH and NH2 groups) and biological (bioactive, biocompatible, biodegradable) properties. These unique properties make chitosan an excellent material for the development of new biomedical applications. One of the most well known biomedical chitosan applications is in drug delivery systems. Chitosans have been used in the design of many different types of drug carriers for various administration routes such as oral, bucal, nasal, transdermal, parenteral, vaginal, cervical, intrauterine and rectal. Chitosan can be engineered into different shapes and geometries such as nanoparticles, microspheres, membranes, sponges and rods. This paper is a perspective on the preparation of the chitosan drug delivery systems based on different structural geometries. In this respect, special preparation techniques are used to prepare chitosan drug carriers by altering such parameters as crosslinker concentration, chitosan molecular weight, drug/polymer ratio and processing conditions all of which affect the morphology of chitosan drug carriers and release rate of the loaded drug.

Macroporous Scaffolds Based on Chitosan and Bioactive Molecules†

Chitosan-based macroporous scaffolds for tissue engineering applications are developed by cryogelation in aqueous media. The cryogels obtained are modified using a new RGD-containing peptide developed in this laboratory. A RGD-containing peptide is chemically attached to the surface of the cryogels to improve cell adhesion to the 3D-structure chitosan-based scaffolds. The synthesis, physico-chemical, and biological evaluations of the system are described, and the optimization of the formulations is carried out by varying the reaction parameters. Fibroblasts and endothelial cells are used in cell cultures to determine cell behavior and the cytocompatibility of the macroporous cryogels. Cell spreading and actin cytoskeleton organization process are assessed by confocal microscopy. Cells colonize the porous structure of the chitosan-based cryogel and are observed to be growing inside the pores.

Effects of Chemical Conjugation of l-Leucine to Chitosan on Dispersibility and Controlled Release of Drug from a Nanoparticulate Dry Powder Inhaler Formulation

This study investigated l-leucine-conjugated chitosan as a drug delivery vehicle in terms of dispersibility and controlled release from a nanoparticulate dry powder inhaler (DPI) formulation for pulmonary delivery using diltiazem hydrochloride (DH) as the model drug. DH-loaded nanoparticles of chitosan and conjugate were prepared by water-in-oil emulsification followed by glutaraldehyde cross-linking. Nanoparticles were characterized by dynamic light scattering for particle size, X-ray photoelectron spectroscopy for surface composition, and twin stage impinger for drug dispersibility. The controlled release of DH was studied in phosphate-buffered saline (pH 7.3 ± 0.2, 37 °C) using UV spectrophotometry. The fine particle fractions of conjugated chitosan with and without drug were higher than those of nonconjugated chitosan nanoparticles. The conjugate nanoparticles were superior to those of unmodified chitosan in drug loading, entrapment efficiency, and controlled release profile. The higher dispersibility was attributed to the amphiphilic environment of the l-leucine conjugate and hydrophobic cross-links, and the release profile reflects the greater swelling. The conjugated chitosan nanoparticles could be useful, after appropriate testing for biodegradability and toxicity, as an alternative carrier for lung drug delivery with enhanced aerosolization and prolonged drug release from nanoparticulate DPI formulations.

Enzymatic Degradation of Polysaccharide-Based Layer-by-Layer Structures

The lack of knowledge on the degradation of layer-by-layer structures is one of the causes hindering its translation to preclinical assays. The enzymatic degradation of chitosan/hyaluronic acid films in the form of ultrathin films, freestanding membranes, and microcapsules was studied resorting to hyaluronidase. The reduction of the thickness of ultrathin films was dependent on the hyaluronidase concentration, leading to thickness and topography variations. Freestanding membranes exhibited accelerated weight loss up to 120 h in the presence of the enzyme, achieving complete degradation. Microcapsules with around 5 μm loaded simultaneously with FITC-BSA and hyaluronidase showed that the coencapsulation of such enzyme and protein mixture led to a FITC-BSA release four times higher than in the absence of hyaluronidase. The results suggest that the degradation of LbL devices may be tuned via embedded enzymes, namely, in the controlled release of active agents in biomedical applications.

Probing the electrochemical properties of biopolymer modified EMD nanoflakes through electrodeposition for high performance alkaline batteries

In the present work, a novel biopolymer approach has been made to electrodeposit manganese dioxide from manganese sulphate in a sulphuric acid bath containing chitosan in the absence and presence of glutaraldehyde as a cross-linking agent. Galvanostatically synthesised electrolytic manganese dioxide (EMD) nanoflakes were used as electrode materials and their electrochemical properties with the influence of biopolymer chitosan were systematically characterized. The structural determination, surface morphology and porosity of nanostructured EMD were evaluated using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and nitrogen adsorption-desorption techniques. The results obtained were compared with that of blank EMD (polymer free). The results indicated that the EMD having chitosan cross-linked with glutaraldehyde possesses a reduced particle size and more porous structure than the blank and EMDs synthesized in the presence of chitosan but without glutaraldehyde. The results revealed that chitosan was unable to play any significant role on its own but chitosan in the presence of glutaraldehyde forms a cross-linking structure, which in turn influences the nucleation and growth of the EMDs during electrodeposition. EMDs obtained in the presence of chitosan (1 g dm(-3)) and glutaraldehyde (1% glutaraldehyde) exhibited a reversible and better discharge capacity upon cycling than the blank which showed its typical capacity fading behaviour with cycling. In addition, EMD synthesized in the presence of 1 g dm(-3) chitosan and 2% glutaraldehyde exhibited a superior electrochemical performance than the blank and lower amounts (1%; 1.5%) of glutaraldehyde, showing a stable discharge capacity of 60 mA h g(-1) recorded up to 40 cycles in alkaline KOH electrolyte for a Zn-MnO2 system. Our results demonstrate the potential of using polymer modified EMDs as a new generation of alkaline battery materials. The XPS data show that a surface functional moiety arising from the cross-linked chitosan enhances the electrochemical properties of the Zn-MnO2 system.

Biomimetic polysaccharide/bioactive glass nanoparticles multilayer membranes for guided tissue regeneration

Freestanding multilayered membranes, produced with chitosan, hyaluronic acid and bioactive glass nanoparticles, were shown to behave differently based on composition.

Impact of chitosan composites and chitosan nanoparticle composites on various drug delivery systems: A review

Chitosan is a promising biopolymer for drug delivery systems. Because of its beneficial properties, chitosan is widely used in biomedical and pharmaceutical fields. In this review, we summarize the physicochemical and drug delivery properties of chitosan, selected studies on utilization of chitosan and chitosan-based nanoparticle composites in various drug delivery systems, and selected studies on the application of chitosan films in both drug delivery and wound healing. Chitosan is considered the most important polysaccharide for various drug delivery purposes because of its cationic character and primary amino groups, which are responsible for its many properties such as mucoadhesion, controlled drug release, transfection, in situ gelation, and efflux pump inhibitory properties and permeation enhancement. This review can enhance our understanding of drug delivery systems particularly in cases where chitosan drug-loaded nanoparticles are applied.

Synthesis, characterization and antibacterial studies of ruthenium(III) complexes derived from chitosan schiff base

Chitosan can be modified chemically by condensation reaction of deacetylated chitosan with aldehyde in homogeneous phase. This condensation is carried by primary amine (NH2) with aldehyde (CHO) to form corresponding schiff base. The chitosan biopolymer schiff base derivatives are synthesized with substituted aldehydes namely 4-hydroxy-3-methoxy benzaldehyde, 2-hydroxy benzaldehyde, and 2-hydroxy-3-methoxy benzaldehyde, becomes a complexing agent or ligand. The Ruthenium(III) complexes were obtained by complexation of Ruthenium with schiff base ligands and this product exhibits as an excellent solubility and more biocompatibility. The novel series of schiff base Ruthenium(III) complexes are characterized by Elemental analysis, FT-IR spectroscopy, and Thermo-gravimetric analysis (TGA). The synthesized complexes have been subjected to antibacterial study. The antibacterial results indicated that the antibacterial activity of the complexes were more effective against Gram positive and Gram negative pathogenic bacteria. These findings are giving suitable support for developing new antibacterial agent and expand our scope for applications.

Chitosan in Molecularly-Imprinted Polymers: Current and Future Prospects

Chitosan is widely used in molecular imprinting technology (MIT) as a functional monomer or supporting matrix because of its low cost and high contents of amino and hydroxyl functional groups. The various excellent properties of chitosan, which include nontoxicity, biodegradability, biocompatibility, and attractive physical and mechanical performances, make chitosan a promising alternative to conventional functional monomers. Recently, chitosan molecularly-imprinted polymers have gained considerable attention and showed significant potential in many fields, such as curbing environmental pollution, medicine, protein separation and identification, and chiral-compound separation. These extensive applications are due to the polymers' desired selectivity, physical robustness, and thermal stability, as well as their low cost and easy preparation. Cross-linkers, which fix the functional groups of chitosan around imprinted molecules, play an important role in chitosan molecularly-imprinted polymers. This review summarizes the important cross-linkers of chitosan molecularly-imprinted polymers and illustrates the cross-linking mechanism of chitosan and cross-linkers based on the two glucosamine units. Finally, some significant attempts to further develop the application of chitosan in MIT are proposed.