Glutaraldehyde and glyoxal cross-linked chitosan microspheres for controlled delivery of centchroman

New biobased chitosan-modified peach kernel shell composites and examining their behavior in different environmental conditions

Bisphenol A-type epoxy (ER) is a versatile synthetic polymer preferred for composite materials but non-biodegradability raises challenges for composites recycling in particular. The present study first investigated the potential usability of peach kernel shells (PKSh) waste as fillers in ER to decrease the cost of composite materials and increase their bio-based content. Different chemical modifications were performed to increase the poor compatibility between the hydrophilic lignocellulosic filler and the hydrophobic polymer matrix. The modified PKShs were obtained by alkali treatment (NaOH-PKSh), coating with biopolymer chitosan (CTS-PKSh), and cross-linking of CTS with glutaraldehyde (GA@CTS-PKSh). The aging of composites is a highly topical subject given the increasing use of composites in structural applications in many industries. The composites' thermal stability and dynamic-mechanical properties in different aging environments (water, seawater, and hydrothermal) were examined. The order of the aging conditions in terms of their effects on the composite properties was: hydrothermal > water > seawater. The ER/GA@CTS-PKSh composite was the most resistant to all environmental conditions. The tensile strength of epoxy matrix (ER) increased max. by 7.78 %, 21.11 %, 42.22 %, and 45.46 % in the case of raw, NaOH-PKSh, CTS-PKSh, and GA@CTS-PKSh fillers, respectively. Composites showed higher absorption in both UV and visible regions.

Glyoxal crosslinking of electro-responsive alginate-based hydrogels: Effects on the properties

To improve the features of alginate-based hydrogels in physiological conditions, Ca2+-crosslinked semi-interpenetrated hydrogels formed by poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid and alginate (PEDOT/Alg) were subjected to a treatment with glyoxal to form a dual ionic/covalent network. The covalent network density was systematically varied by considering different glyoxalization times (tG). The content of Ca2+ was significantly higher for the untreated hydrogel than for the glyoxalized ones, while the properties of the hydrogels were found to largely depend on tG. The porosity and swelling capacity decreased with increasing tG, while the stiffness and electrical conductance retention capacity increased with tG. The potentiodynamic response of the hydrogels notably depended on the amount of conformational restraints introduced by the glyoxal, which is a very short crosslinker. Thus, the re-accommodation of the polymer chains during the cyclic potential scans became more difficult with increasing number of covalent crosslinks. This information was used to improve the performance of untreated PEDOT/Alg as electrochemical sensor of hydrogen peroxide by simply applying a tG of 5 min. Overall, the control of the properties of glyoxalized hydrogels through tG is very advantageous and can be used as an on-demand strategy to improve the performance of such materials depending on the application.

Ozonated Sunflower Oil Embedded within Spray-Dried Chitosan Microspheres Cross-Linked with Azelaic Acid as a Multicomponent Solid Form for Broad-Spectrum and Long-Lasting Antimicrobial Activity

Multicomponent solid forms for the combined delivery of antimicrobials can improve formulation performance, especially for poorly soluble drugs, by enabling the modified release of the active ingredients to better meet therapeutic needs. Chitosan microspheres incorporating ozonated sunflower oil were prepared by a spray-drying method and using azelaic acid as a biocompatible cross-linker to improve the long time frame. Two methods were used to incorporate ozonated oil into microspheres during the atomization process: one based on the use of a surfactant to emulsify the oil and another using mesoporous silica as an oil absorbent. The encapsulation efficiency of the ozonated oil was evaluated by measuring the peroxide value in the microspheres, which showed an efficiency of 75.5-82.1%. The morphological aspects; particle size distribution; zeta potential; swelling; degradation time; and thermal, crystallographic and spectroscopic properties of the microspheres were analyzed. Azelaic acid release and peroxide formation over time were followed in in vitro analyses, which showed that ozonated oil embedded within chitosan microspheres cross-linked with azelaic acid is a valid system to obtain a sustained release of antimicrobials. In vitro tests showed that the microspheres exhibit synergistic antimicrobial activity against P. aeruginosa, E. coli, S. aureus, C. albicans and A. brasiliensis. This makes them ideal for use in the development of biomedical devices that require broad-spectrum and prolonged antimicrobial activity.

Exploring the current landscape of chitosan-based hybrid nanoplatforms as cancer theragnostic

In the last decade, investigators have put significant efforts to develop several diagnostic and therapeutic strategies against cancer. Many novel nanoplatforms, including lipidic, metallic, and inorganic nanocarriers, have shown massive potential at preclinical and clinical stages for cancer diagnosis and treatment. Each of these nano-systems is distinct with its own benefits and limitations. The need to overcome the limitations of single-component nano-systems, improve their morphological and biological features, and achieve multiple functionalities has resulted in the emergence of hybrid nanoparticles (HNPs). These HNPs integrate multicomponent nano-systems with diagnostic and therapeutic functions into a single nano-system serving as promising nanotools for cancer theragnostic applications. Chitosan (CS) being a mucoadhesive, biodegradable, and biocompatible biopolymer, has emerged as an essential element for the development of HNPs offering several advantages over conventional nanoparticles including pH-dependent drug delivery, sustained drug release, and enhanced nanoparticle stability. In addition, the free protonable amino groups in the CS backbone offer flexibility to its structure, making it easy for the modification and functionalization of CS, resulting in better drug targetability and cell uptake. This review discusses in detail the existing different oncology-directed CS-based HNPs including their morphological characteristics, in-vitro/in-vivo outcomes, toxicity concerns, hurdles in clinical translation, and future prospects.

A self-healable and bioadhesive acacia gum polysaccharide-based injectable hydrogel for wound healing acceleration

The present study aimed at developing an injectable hydrogel based on acacia gum (AG) for wound healing acceleration. The hydrogels were synthetized through metal-ligand coordination mediated by Fe3+ and characterized in terms of gelation time, gel content, initial water content, swelling capacity, water retention ratio, and porosity. Moreover, FTIR, XRD and TGA analyses were performed for the hydrogels and allantoin (Alla) loaded ones. Furthermore, bioadhessiveness, and self-healing as well as antibacterial, toxicity and wound healing potentials of the hydrogels were evaluated. The hydrogels displayed fast gelation time, high swelling, porosity, and bioadhessiveness, as well as antioxidant, self-healing, antibacterial, blood clotting, and injectability properties. FTIR, XRD and TGA analyses confirmed hydrogel synthesis and drug loading. The Alla-loaded hydrogels accelerated wound healing by decreasing the inflammation and increasing the cell proliferation as well as collagen deposition. Hemocompatibility, cell cytotoxicity, and in vivo toxicity experiments were indicative of a high biocompatibility level for the hydrogels. Given the advantages of fast gelation, injectability and beneficial biological properties, the use of Alla-loaded hydrogels could be considered a new remedy for efficient wound healing.

Superparamagnetic Hybrid Nanospheres Based on Chitosan Obtained by Double Crosslinking in a Reverse Emulsion for Cancer Treatment

Nowadays, the Magnetically Targeted Drug Delivery System (MTDDS) is among the most attractive and promising strategies for delivering drugs to the target site. The present study aimed to obtain a biopolymer-magnetite-drug nanosystem via a double crosslinking (ionic and covalent) technique in reverse emulsion, which ensures the mechanical stability of the polymer support in the form of original hybrid nanospheres (NSMs) loaded with biologically active principles (the 5-Fluorouracil (5-FU)) as a potential treatment for cancer. Obtained NSMs were characterized in terms of structure (FT-IR), size (DLS), morphology (SEM), swelling, and 5-FU entrapment/release properties, which were dependent on the synthesis parameters (polymer concentration, dispersion speed, and amount of ionic crosslinking agent). SEM analysis results revealed that NSMs presented a spherical shape and are homogeneous and separated. Moreover, NSMs' ability to load/release 5-FU was tested in vitro, the results confirming, as expected, their dependence on the varied synthesis process and NSM swelling ability in physiological liquids. The drug transport mechanism through the polymer matrix of its release is the Fickian type. The morphological, bio-material characteristics and the ability to include and release an antitumor drug highlight the utility of the NSMs obtained for targeting and treating some tumor diseases.

Effects of Surface Morphology and Type of Cross-Linking of Chitosan-Pectin Microspheres on Their Degree of Swelling and Favipiravir Release Behavior

The cross-linked microspheres were prepared and loaded with Favipiravir SARS-CoV-2 antiviral drug, by copolymerization of chitosan (CS) with a polysaccharide extracted from fresh pomegranate peels. Moreover, glutaraldehyde (Glu) has been used as a chemical cross-linker and sodium hexametaphosphate (SHMP) as a physical cross-linker. The extracted polysaccharide was analyzed, and different techniques have been used. The analyses lead to the conclusion that it is pectin. The surface morphology of the prepared microspheres was studied using a scanning electron microscope, where the size and shape factor (S) of the Glu microspheres showed high values (74.27 μm) and (0.852), respectively, meaning their surfaces tend to be rough, whereas the SHMP microspheres showed a smaller size particle (20.47 μm) and a smaller shape factor (0.748), which gives an indication that the SHMP microspheres have smooth surfaces. The swelling studies have shown that Glu microspheres have a higher degree of swelling, which means SHMP microspheres are more compact. The prepared microspheres have shown a higher loading percentage of Favipiravir antiviral drug in SHMP microspheres (37% w/w) in comparison with Glu microspheres (35% w/w), where the electrostatic interaction between the Favipiravir ions and SHMP anions helps for more loading. The microspheres prepared under different types of cross-linking have shown initial burst release of Favipiravir, followed by a step of controlled release for a certain period of time, whose period depends on the pH of the release medium. Both Glu and SHMP cross-linked microspheres have shown high controlled release times in buffered release solutions at pH = 7.4 and for shorter periods at pH = 1.3 and pH = 9.4, which may be related to the type of electrostatic interactions between drug and polymer systems and their reactions with release solution ions.

Chitosan-Based Architectures as an Effective Approach for the Removal of Some Toxic Species from Aqueous Media

Modified uncrosslinked and crosslinked chitosan derivatives were investigated as green sorbents for the removal of copper (Cu²⁺) and lead (Pb²⁺) cations from simulated solutions. In this regard, N, O carboxymethyl chitosan (N, O CMC), chitosan beads (Cs-g-GA), chitosan crosslinked with glutaraldehyde/methylene bisacrylamide (Cs/GA/MBA), and chitosan crosslinked with GA/epichlorohydrin (Cs/GA/ECH) were prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy analyses. Atomic force microscopy investigation was carried out to compare the surface topography of the prepared samples before and after the metal uptake. The kinetics of the removal process were investigated by pseudo-first-order and -second-order models. Moreover, the adsorption isotherms were carefully studied by applying Langmuir and Freundlich models. The data reveal that upon adsorption of copper(II) metal ions, all chitosan-modified products followed the Langmuir isotherm except for Cs/GA/ECH which followed the Freundlich isotherms, and the highest adsorption capacity (q _e) was obtained for Cs/GA/MBA due to the formation of stable chelate structures between the metal cation and the functional groups present on the modified chitosan product. The order of metal uptake at the optimum pH value is as follows: Cs/GA/MBA (Cu: 95.7 mg/g, Pb: 99.15 mg/g), Cs/GA/ECH (Cu: 80.4 mg/g, Pb: 93.14 mg/g), Cs-g-GA (Cu: 77 mg/g, Pb: 88.4 mg/g), and N, O CMCh (Cu: 30.2 mg/g, Pb: 44.8 mg/g). The AFM data confirmed the metal uptake process by comparing the roughness and height measurements of the free sorbents and the metal-loaded sorbents.

Are Natural Compounds a Promising Alternative to Synthetic Cross-Linking Agents in the Preparation of Hydrogels?

The main aim of this review is to assess the potential use of natural cross-linking agents, such as genipin, citric acid, tannic acid, epigallocatechin gallate, and vanillin in preparing chemically cross-linked hydrogels for the biomedical, pharmaceutical, and cosmetic industries. Chemical cross-linking is one of the most important methods that is commonly used to form mechanically strong hydrogels based on biopolymers, such as alginates, chitosan, hyaluronic acid, collagen, gelatin, and fibroin. Moreover, the properties of natural cross-linking agents and their advantages and disadvantages are compared relative to their commonly known synthetic cross-linking counterparts. Nowadays, advanced technologies can facilitate the acquisition of high-purity biomaterials from unreacted components with no additional purification steps. However, while planning and designing a chemical process, energy and water consumption should be limited in order to reduce the risks associated with global warming. However, many synthetic cross-linking agents, such as N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, poly (ethylene glycol) diacrylates, epichlorohydrin, and glutaraldehyde, are harmful to both humans and the environment. One solution to this problem could be the use of bio-cross-linking agents obtained from natural resources, which would eliminate their toxic effects and ensure the safety for humans and the environment.

Polysaccharides-Based Injectable Hydrogels: Preparation, Characteristics, and Biomedical Applications

Polysaccharides-based injectable hydrogels are a unique group of biodegradable and biocompatible materials that have shown great potential in the different biomedical fields. The biomolecules or cells can be simply blended with the hydrogel precursors with a high loading capacity by homogenous mixing. The different physical and chemical crosslinking approaches for preparing polysaccharide-based injectable hydrogels are reviewed. Additionally, the review highlights the recent work using polysaccharides-based injectable hydrogels as stimuli-responsive delivery vehicles for the controlled release of different therapeutic agents and viscoelastic matrix for cell encapsulation. Moreover, the application of polysaccharides-based injectable hydrogel in regenerative medicine as tissue scaffold and wound healing dressing is covered.

Physicochemical, Thermal, and Morphological Properties of Chitosan Nanoparticles Produced by Ionic Gelation

Chitosan nanoparticles (CSNPs) can be widely used in the food, pharmaceutical, and cosmetic sectors due to their high performance, unique properties, and high surface area. In this research, CSNPs were produced by the ionic gelation method and using sodium tripolyphosphate (STPP) as an appropriate technique compared to the conventional methods. To evaluate the effects of various factors on the size, zeta potential (ZP), and optimal synthesis conditions, different concentrations of CS (1, 3, and 5 mg/mL), STPP (0.5, 0.75, and 1 mg/mL), and CS to STPP ratio (1:1, 3:1, and 5:1) were applied and optimized using the response surface methodology. The size of CSNPs was increased by using higher concentrations of CS, STPP, and CS/STPP ratios. The value of ZP was determined positive and it increased with increasing CS concentrations and CS/STPP ratios. ATR-FTIR spectra revealed interactions between CS and STPP. The DSC thermogram of CSNPs showed a double sharp endothermic peak at about 74.5 °C (ΔH = 122.00 J/g); further, the TGA thermograms indicated the total weight loss of STPP, CS, and CSNPs as nearly 3.30%, 63.60%, and 52.00%, respectively. The XRD data also revealed a greater chain alignment in the CSNPs. Optimized, the CSNPs can be used as promising carriers for bioactive compounds where they also act as efficient stabilizers in Pickering emulsions.

Curcumin Sustained Release with a Hybrid Chitosan-Silk Fibroin Nanofiber Containing Silver Nanoparticles as a Novel Highly Efficient Antibacterial Wound Dressing

Drug loading in electrospun nanofibers has gained a lot of attention as a novel method for direct drug release in an injury site to accelerate wound healing. The present study deals with the fabrication of silk fibroin (SF)-chitosan (CS)-silver (Ag)-curcumin (CUR) nanofibers using the electrospinning method, which facilitates the pH-responsive release of CUR, accelerates wound healing, and improves mechanical properties. Response surface methodology (RSM) was used to investigate the effect of the solution parameters on the nanofiber diameter and morphology. The nanofibers were characterized via Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), zeta potential, and Dynamic Light Scattering (DLS). CS concentration plays a crucial role in the physical and mechanical properties of the nanofibers. Drug loading and entrapment efficiencies improved from 13 to 44% and 43 to 82%, respectively, after the incorporation of Ag nanoparticles. The application of CS hydrogel enabled a pH-responsive release of CUR under acid conditions. The Minimum Inhibitory Concentration (MIC) assay on E. coli and S. aureus bacteria showed that nanofibers with lower CS concentration cause stronger inhibitory effects on bacterial growth. The nanofibers do not have any toxic effect on cell culture, as revealed by in vitro wound healing test on NIH 3T3 fibroblasts.

Synthesis and Characterization of Functionalized Chitosan Nanoparticles with Pyrimidine Derivative for Enhancing Ion Sorption and Application for Removal of Contaminants

Modified chitosan has been widely used for heavy metals removal during the last few decades. In this research, the study was focused on the effect of modified chitosan particles after grafting with heterocyclic constituent for enhancing the sorption of Cr(VI) ions. Chitosan was functionalized by 2-thioxodihydropyrimidine-4,6(1H,5H)-dione, in which the synthesized composite considered as a nanoscale size with average 5–7 nm. This explains the fast kinetics of sorption with large surface area. The prepared sorbent was characterized by Fourier-transform infrared (FTIR), elemental analysis (EA), Brunauer–Emmett–Teller (BET surface area) theory, thermogravimetric analysis (TGA), mass spectroscopy, and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) analyses. The experimental part of this work involved the application of the synthesized sorbent for the removal of Cr(VI) ions from highly contaminated tannery effluents that are characterized by a high concentration toward chromate ions with other associated toxic elements, i.e., Pb(II) and Cd (II) ions, which underscore the importance of this treatment. Under the selected conditions (K₂Cr₂O₇ salt, C_o: 100 mg L⁻¹ and pH: 4), the sorption diagram shows high Cr(VI) sorption and fast uptake kinetics. The sorption was enhanced by functionalization to 5.7 mmol Cr g⁻¹ as well as fast uptake kinetics; 30 min is sufficient for total sorption compared with 1.97 mmol Cr g⁻¹ and 60 min for the non-grafted sorbent. The Langmuir and Sips equations were fitted for the sorption isotherms, while the pseudo-first order rate equation (PFORE) was fitted for the uptake kinetics.

The role of aldehyde-functionalized crosslinkers on the property of chitosan hydrogels

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Degradation-Dependent Controlled Delivery of Doxorubicin by Glyoxal Cross-Linked Magnetic and Porous Chitosan Microspheres

Glyoxal cross-linked porous magnetic chitosan microspheres, GMS (∼170 μm size), with a tunable degradation profile were synthesized by a water-in-oil emulsion technique to accomplish controlled delivery of doxorubicin (DOX), a chemotherapeutic drug, to ensure prolonged chemotherapeutic effects. The GMS exhibit superparamagnetism with saturation magnetization, M s = 7.2 emu g-1. The in vitro swelling and degradation results demonstrate that a swelling plateau of GMS is reached at 24 h, while degradation can be modulated to begin at 96-120 h by formulating the cross-linked network using glyoxal. MTT assay, live/dead staining, and F-actin staining (actin/DAPI) validated the cytocompatibility of GMS, which further assured good drug loading capacity (35.8%). The release mechanism has two stages, initiated by diffusion-inspired release of DOX through the swollen polymer network (72 h), which is followed by a disintegration-tuned release profile (>96 h) conferring GMS a potential candidate for DOX delivery.

Super absorbent chitosan-based hydrogel sponges as carriers for caspofungin antifungal drug

Novel chitosan copolymers (CS-g-SBMA) grafted with [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) in various molar ratio 1.5:1, 5:1, 11.5:1 and 20:1, were synthesized in the present study. SBMA was selected as zwitterion molecule showing promising antibacterial properties. Grafted chitosan derivatives were fully characterized for their successful synthesis by NMR and FT-IR, for their crystallinity by XRD showing reduced crystallinity compared to CS alone. Furthermore, swelling studies were conducted with the grafted derivatives showing extensive swelling capacity (maximum degree of swelling up to 1800%) and water absorption was studied with differential scanning calorimetry and equilibrium water adsorption/desorption isotherms were analyzed. Caspofungin, a novel antifungal drug, was used to prepare a double-acting system, with both antibacterial and antifungal properties, proper for topical use. Drug loaded hydrogels were prepared with 10, 20 and 30 wt% drug content and the loaded hydrogels were fully characterized while antimicrobial studies showed enhanced properties. Caspofungin in vitro release showed an initial burst effect followed by a diffusion process while data analysis verified the initial burst release followed by a quasi Fickian diffusion-driven sustained release. Enhance antimicrobial properties was also observed in caspofungin-loaded hydrogels showing the successful fulfill of our scope; an amphiphilic system having great potential for the development of patches with inherent antimicrobial properties and prolonged antifungal properties.

Oxi-HA/ADH Hydrogels: A Novel Approach in Tissue Engineering and Regenerative Medicine

Hyaluronic acid (HA) is a natural polyelectrolyte abundant in mammalian connective tissues, such as cartilage and skin. Both endogenous and exogenous HA produced by fermentation have similar physicochemical, rheological, and biological properties, leading to medical and dermo-cosmetic products. Chemical modifications such as cross-linking or conjugation in target groups of the HA molecule improve its properties and in vivo stability, expanding its applications. Currently, HA-based scaffolds and matrices are of great interest in tissue engineering and regenerative medicine. However, the partial oxidation of the proximal hydroxyl groups in HA to electrophilic aldehydes mediated by periodate is still rarely investigated. The introduced aldehyde groups in the HA backbone allow spontaneous cross-linking with adipic dihydrazide (ADH), thermosensitivity, and noncytotoxicity to the hydrogels, which are advantageous for medical applications. This review provides an overview of the physicochemical properties of HA and its usual chemical modifications to better understand oxi-HA/ADH hydrogels, their functional properties modulated by the oxidation degree and ADH concentration, and the current clinical research. Finally, it discusses the development of biomaterials based on oxi-HA/ADH as a novel approach in tissue engineering and regenerative medicine.

The Preparation and Characterization of Chitosan-Based Hydrogels Cross-Linked by Glyoxal

In this study, hydrogels based on chitosan cross-linked by glyoxal have been investigated for potential medical applications. Hydrogels were loaded with tannic acid at different concentrations. The thermal stability and the polyphenol-releasing rate were determined. For a preliminary assessment of the clinical usefulness of the hydrogels, they were examined for blood compatibility and in the culture of human dental pulp cells (hDPC). The results showed that after immersion in a polyphenol solution, chitosan/glyoxal hydrogels remain nonhemolytic for erythrocytes, and we also did not observe the cytotoxic effect of hydrogels immersed in tannic acid (TA) solutions with different concentration. Tannic acid was successfully released from hydrogels, and its addition improved material thermal stability. Thus, the current findings open the possibility to consider such hydrogels in clinics.

Development of Chitosan Microspheres through a Green Dual Crosslinking Strategy Based on Tripolyphosphate and Vanillin

Microencapsulation procedures have recently focused attention on designing novel microspheres via green synthesis strategies. The use of chitosan (CS) as an encapsulating material has increased interest due to its unique bioactive properties and the various crosslinking possibilities offered by their functional groups. The consolidation of the microspheres by physical crosslinking using sodium tripolyphosphate (TPP) combined with chemical crosslinking using vanillin (VA) open new opportunities in the framework of green dual crosslinking strategies. The developed strategy, a straightforward technique based on an aqueous medium avoiding complex separation/washing steps, offers advantages over the processes based on VA, mostly using water-in-oil emulsion approaches. Thus, in this work, the combination of TPP crosslinking (3, 5, and 10 wt.%) via spray-coagulation technique with two VA crosslinking methods (in situ and post-treatment using 1 wt.% VA) were employed in the preparation of microspheres. The microspheres were characterized concerning morphology, particle size, physicochemical properties, thermal stability, and swelling behavior. Results revealed that the combination of 5 wt.% TPP with in situ VA crosslinking led to microspheres with promising properties, being an attractive alternative for natural bioactives encapsulation due to the green connotations associated with the process.

Chitosan modifications for adsorption of pollutants - A review

In recent times, research interest into the development of biodegradable, cost-effective and environmental friendly adsorbents with favourable properties for adsorption of pollutants is a challenge. Modification of chitosan via different physical and chemical methods have gained attention as a promising approach for removing organic (such as dyes and pharmaceuticals) and inorganic (such as metal/metal ions) pollutants from aqueous medium. In this regard, researchers have reported grafting and cross-linking approach among others as a potentially useful method for chitosan's modification for improved adsorption efficiency with respect to pollutant uptake. This article reviews the trend in chitosan modification, with regards to the summary of some recently published works on modification of chitosan and their adsorption application in pollutants (metal ion, dyes and pharmaceuticals) removal from aqueous medium. The review uniquely highlights some common cross-linkers and grafting procedures for chitosan modification, their influence on structure and adsorption capacity of modified-chitosan with respect to pollutants removal. Findings revealed that the performance of modified chitosan for adsorption of pollutants depends largely on the modification method adopted, materials used for the modification and adsorption experimental conditions. Cross-linking is commonly utilized for improving the chemical and mechanical stabilities of chitosan but usually decreases adsorption capacity of chitosan/modified-chitosan for adsorption of pollutants. However, literature survey revealed that adsorption capacity of cross-linked chitosan based materials have been enhanced in recently published works either by grafting, incorporation of solid adsorbents (e.g metals, clays and activated carbon) or combination of both prior to cross-linking.

Microstructures of encapsulates and their relations with encapsulation efficiency and controlled release of bioactive constituents: A review

Vitamins, peptides, essential oils, and probiotics are examples of health beneficial constituents, which are nevertheless heat-sensitive and possess poor chemical stability. Various encapsulation methods have been applied to protect these constituents against thermal and chemical degradations. Encapsulates prepared by different methods and/or at different conditions exhibit different microstructures, which in turn differently influence the encapsulation efficiency as well as retention of encapsulated core materials. This review provides a summary of various microstructures resulted from the use of selected encapsulation methods or systems, namely, spray coating; co-extrusion; emulsion-, micelle-, and liposome-based; coacervation; and ionic gelation encapsulation, at different conditions. Subsequent effects of the different microstructures on encapsulation efficiency and retention of encapsulated core materials are mentioned and discussed. Encapsulates having compact microstructures resulted from the use of low-surface tension and low-viscosity encapsulants, high-stability encapsulation systems, lower loads of core materials to total solids of encapsulants and appropriate solidification conditions have proved to exhibit higher encapsulation efficiencies and better retention of encapsulated core materials. Encapsulates with hollow, dent, shrunken microstructures or thinner walls resulted from inappropriate solidification conditions and higher loads of core materials, on the other hand, possess lower encapsulation efficiencies and protection capabilities. Encapsulates having crack, blow-hole or porous microstructures resulted from the use of high-viscosity encapsulants and inappropriate solidification conditions exhibit the lowest encapsulation efficiencies and poorest protection capabilities. Compact microstructures and structures formed between ionic biopolymers could be used to regulate the release of encapsulated cores.

Preliminary Evaluation of 3D Printed Chitosan/Pectin Constructs for Biomedical Applications

In the present study, chitosan (CS) and pectin (PEC) were utilized for the preparation of 3D printable inks through pneumatic extrusion for biomedical applications. CS is a polysaccharide with beneficial properties; however, its printing behavior is not satisfying, rendering the addition of a thickening agent necessary, i.e., PEC. The influence of PEC in the prepared inks was assessed through rheological measurements, altering the viscosity of the inks to be suitable for 3D printing. 3D printing conditions were optimized and the effect of different drying procedures, along with the presence or absence of a gelating agent on the CS-PEC printed scaffolds were assessed. The mean pore size along with the average filament diameter were measured through SEM micrographs. Interactions among the characteristic groups of the two polymers were evident through FTIR spectra. Swelling and hydrolysis measurements confirmed the influence of gelation and drying procedure on the subsequent behavior of the scaffolds. Ascribed to the beneficial pore size and swelling behavior, fibroblasts were able to survive upon exposure to the ungelated scaffolds.

Silk Fibroin/Collagen/Chitosan Scaffolds Cross-Linked by a Glyoxal Solution as Biomaterials toward Bone Tissue Regeneration

In this study, three-dimensional materials based on blends of silk fibroin (SF), collagen (Coll), and chitosan (CTS) cross-linked by glyoxal solution were prepared and the properties of the new materials were studied. The structure of the composites and the interactions between scaffold components were studied using FTIR spectroscopy. The microstructure was observed using a scanning electron microscope. The following properties of the materials were measured: density and porosity, moisture content, and swelling degree. Mechanical properties of the 3D materials under compression were studied. Additionally, the metabolic activity of MG-63 osteoblast-like cells on materials was examined. It was found that the materials were characterized by a high swelling degree (up to 3000% after 1 h of immersion) and good porosity (in the range of 80–90%), which can be suitable for tissue engineering applications. None of the materials showed cytotoxicity toward MG-63 cells.

Pluronic Polymer-Based Ormeloxifene Nanoformulations Induce Superior Anticancer Effects in Pancreatic Cancer Cells

Utilization of safe cytotoxic agents with precise anticancer activity is considered as the prime focus of cancer therapeutics research. A greater incentive for such agents arises from the molecules/drugs that are already being used for other indications. Ormeloxifene (ORM) is a nonsteroidal, nonhormonal selective estrogen receptor modulator (SERM), which has been in human use for contraception purposes. Although in the recent past, many reports have suggested its emerging role as an anticancer agent, no significant attention was paid toward generating simple and safe nanoformulation(s) for improved therapeutic activity and tumor cell-specific delivery. Our aim is to develop nanoformulation(s) of ormeloxifene to improve its targeted delivery in tumor cells. We developed ormeloxifene nanoformulation(s) by utilizing various biocompatible polymers. The optimized formulations with pluronic polymers F127 and F68 show improved nanoparticle characteristics. These formulations show enhanced cellular uptake that allows ormeloxifene's intracellular availability. We further evaluated its improved anticancer activity by performing cell proliferation, flow cytometry, and immunoblotting assays. Overall, this study confirms possible novel nanoformulation(s) of ormeloxifene to be evolved as a new therapeutic modality for cancer treatment.

Preparation of Chitosan Molecularly Imprinted Polymers and the Recognition Mechanism for Adsorption of Alpha-Lipoic Acid

Two effective molecularly imprinted polymers for the adsorption of alpha-lipoic acid (ALA) were synthesized by the cross-linking of chitosan with epichlorohydrin (ECH) and glutaraldehyde (GLU), respectively, in the presence of ALA as template molecules. Investigations on the molar ratios of ALA and chitosan (–NH₂) in the preparation of chitosan molecularly imprinted polymers (MIPs) were carried out with a factor of ALA rebinding capabilities. The surface morphology and chemical properties of the polymers were characterized. The optimized MIPs crosslinked by ECH (MIPs–ECH) and MIPs crosslinked by GLU (MIPs–GLU) had adsorption capabilities of 12.09 mg/g and 19.72 mg/g for ALA, respectively. The adsorption behaviors of two kinds of chitosan MIPs including adsorption kinetics and isotherms were investigated in detail. Adsorption and kinetic binding experiments showed that the prepared MIPs–ECH and MIPs–GLU had selective adsorption and excellent affinity for ALA. In addition, the possible binding models between ALA and chitosan oligosaccharide were predicted by molecular dynamics simulation.

Controllable Wrinkling Patterns on Chitosan Microspheres Generated from Self-Assembling Metal Nanoparticles

Materials with surface wrinkles at a micro/nanoscale possess extraordinary fascinating properties, and various techniques have been employed to create controllable wrinkles. Herein, natural polysaccharide was used to construct the surface wrinkled microsphere with controllable wrinkling patterns. A robust microsphere with an average size of about 55 μm fabricated from chitosan in alkali/urea aqueous solution was swelled and then coated orderly by introducing rigid silver nanoparticles (Ag NPs) with an average size of about 5 nm as the shell onto the surface through electrostatic layer-by-layer (LBL) self-assembly followed by deswelling, resulting in a surface wrinkled microsphere. The significant difference in the swelling behaviors between the stiff Ag shell and swelled chitosan microsphere could generate enough driving forces to form 3D micro- and nanoscale wrinkling surface topography. The surface wrinkled microspheres exhibited the hierarchically porous structure and hydrophobicity, and the topographical patterns could be adjusted by controlling the thickness of the Ag NP layer to achieve the sizes of wrinkling ranging from 60 to 300 nm. It was demonstrated that the wrinkled microspheres were superior as 3D surface-enhanced Raman spectroscopy (SERS) substrates, in which the wrinkled structure with spatial periodicity was proved to be effective for enhancing the SERS signal. The microsphere with controllable wrinkled surface topography could be applied to be a miniature 3D device, which promises potential technological applications in various areas.

Mathematical Modeling of Release Kinetics from Supramolecular Drug Delivery Systems

Embedding of active substances in supramolecular systems has as the main goal to ensure the controlled release of the active ingredients. Whatever the final architecture or entrapment mechanism, modeling of release is challenging due to the moving boundary conditions and complex initial conditions. Despite huge diversity of formulations, diffusion phenomena are involved in practically all release processes. The approach in this paper starts, therefore, from mathematical methods for solving the diffusion equation in initial and boundary conditions, which are further connected with phenomenological conditions, simplified and idealized in order to lead to problems which can be analytically solved. Consequently, the release models are classified starting from the geometry of diffusion domain, initial conditions, and conditions on frontiers. Taking into account that practically all solutions of the models use the separation of variables method and integral transformation method, two specific applications of these methods are included. This paper suggests that "good modeling practice" of release kinetics consists essentially of identifying the most appropriate mathematical conditions corresponding to implied physicochemical phenomena. However, in most of the cases, models can be written but analytical solutions for these models cannot be obtained. Consequently, empiric models remain the first choice, and they receive an important place in the review.

Enhancing hydrophobicity, strength and UV shielding capacity of starch film via novel co-cross-linking in neutral conditions

Starch films are developed as the biodegradable packaging materials to replace the petroleum-based materials in recent years. Thus, it is extremely beneficial to improve the hydrophobicity and mechanical strength of starch films, through a novel approach of co-cross-linking in neutral conditions, with glyoxal and AZC. In this work, systematic studies have been conducted to assess the performance of the co-cross-linked starch along with the control starch and starch cross-linked by glyoxal or AZC alone. Results showed that the co-cross-linked starch films exhibited significantly improved hydrophobicity and strength and the wet stress reached 1.53 MPa, compared to the control, glyoxal or AZC cross-linked starch films. More interestingly, the co-cross-linked film also demonstrated excellent UV shielding capacity and transmittance at visible wavelength range. The reaction mechanism was revealed based on the findings from UV, FT-IR and NMR spectra. This work established an innovative approach to improving the performance of starch film in neutral conditions for packaging applications.

Injectable Gel Constructs with Regenerative and Anti-Infective Dual Effects Based on Assembled Chitosan Microspheres

There is increasing demand for biomaterials that both assist with bone regeneration and have anti-infection qualities in clinical applications. To achieve this goal, chitosan microspheres with either positive or negative charges were fabricated and then assembled as a gel for bone healing. The positively charged chitosan microspheres (CSM; ∼35.5 μm) and negatively charged O-carboxymethyl chitosan microspheres (CMCSM; ∼13.5 μm) were loaded, respectively, with bone morphogenetic protein (BMP-2) and berberine (Bbr) via swollen encapsulation and physical adsorption without a significant change in the electric charges. The release kinetics of BMP-2 and Bbr from the microspheres were also studied in vitro. The results showed that the Bbr/CMCSM microsphere group possessed high antibacterial activity against Staphylococcus aureus; the BMP-2/CSM microsphere group also had excellent cytocompatibility and improved osteoinductivity with the assistance of BMP-2. The assembled gel group consisting of Bbr/CMCSM and BMP-2/CSM had a porous structure that allowed biological signal transfer and tissue infiltration and exhibited significantly enhanced bone reconstruction compared with that of the respective microsphere groups, which should result from the osteoconductivity of the porous structure and the osteoinduction of the BMP-2 growth factor. The oppositely charged microspheres and their assembled gel provide a promising prospect for making injectable tissue-engineered constructs with regenerative and anti-infective dual effects for biomedical applications.