pH-responsive hydrogel membranes based on modified chitosan: water transport and kinetics of swelling

Advances and opportunities of hydrogel-based artificial olfactory colorimetric systems for food safety detection: A review

BACKGROUND

Food safety has attracted increasing attention in recent years. Harmful gases often produced during food storage have devastating effects on human health and ecosystems, and identifying and detecting them is essential. To date, many traditional methods have been used to monitor the freshness of food products. These methods have high precision and sensitivity, but their application to daily life is limited because they are time-consuming and require complex instruments. Therefore, the development of simple, rapid, and low-cost methods for evaluating food freshness is essential.

RESULTS

Hydrogel-based colorimetric artificial olfactory systems have attracted a great deal of attention and have been widely applied in the field of food safety testing in recent years. The system has the advantages of a low detection limit, portability, onsite monitoring, high precision and rapid detection. This superiority makes the colorimetric hydrogel gas sensor a strong contender for improving food safety detection. This paper reviews the application of a hydrogel-based colorimetric artificial olfactory system for detecting hazardous gases for food safety purposes. The main sections of this review succinctly discuss the construction principles and operational mechanisms of the colorimetric artificial olfactory system. Additionally, it delves into the selection and preparation methodologies of hydrogel materials. This paper focuses on advancements in hydrogel-based colorimetric artificial olfactory systems for detecting gases, such as ammonia, biogenic amines, and H2S that are relevant to food safety. Furthermore, this work outlines the challenges encountered by this artificial olfactory system and proposes potential solutions to overcome them.

SIGNIFICANCE AND NOVELTY

The study presented in this paper demonstrates the potential application of a hydrogel-based colorimetric artificial olfactory system for food safety detection, and complements the previous review of colorimetric hydrogel gas sensors for the detection of spoilage gases in food products and serves as a reference for further advanced research and applications in this field.

Development, characterization, and comparison of chitosan microparticles as a carrier system for black bean protein hydrolysates with antioxidant capacity

Peptides in black bean protein hydrolysates (BPHs) exert antioxidant capacity. However, peptides are prone to degradation during processing and digestion. Chitosan (Ch) can protect them and provide a delayed release. This work develops and compares two drying methods producing porous structured Ch microparticles (MPs) as carriers for antioxidant BPH. Ch gels were obtained by ionic gelation and dried by supercritical CO2 solvent displacement or fast-freeze-drying methods. The resulting aerogels and fast-freeze-dried MPs were structurally characterized, and their swelling and release profiles were obtained at pH 1.2 and 7.4. The antioxidant capacity of systems was determined by 2,2'-azino-bis(3-ethyl-benzthiazoline-6-sulphonic acid) (ABTS) and superoxide radical assays. The results showed BPH-Ch best complexation conditions occurring at a pH of 4.5 and a 4:1 BPH/Ch ratio. The particle size of the complex was 1047.6 nm, and the entrapment efficiency and loading capacity were 28.2% and 54.3%, respectively. At pH 1.2 and 7.4, the release rate of BPH was lower in aerogel than in fast-freeze-dried MPs. Besides, entrapment BPH in Ch significantly reduced the ABTS antioxidant activity IC50 from 35.1 µM Trolox equivalents (TE)/mg to 250.7 and 406.2 µM TE/mg for Ch fast-freeze-dried and aerogels, respectively. Superoxide radical inhibition IC50 ranged from 74.6 to 92.9 mM ascorbic acid equivalents/mg in the different samples. BPH-loaded aerogels presented lower specific surface area (94.7 vs. 138.6 m2/g, p < 0.05) and higher average pore size (26.4 vs. 19.8 nm) than Ch aerogels. Ch aerogel is a promising carrier for delaying the release of common bean antioxidant peptides useful for developing functional foods. PRACTICAL APPLICATION: This novel system could act as an ingredient to incorporate antioxidant compounds in different formats to develop delayed-release nutraceuticals and functional foods, such as bakery, dairy products, or beverages. Along, antioxidant peptide-loaded aerogels could be used as a slow-release system for compounds acting as natural preserving antioxidants for food applications such as raw meat products or high-fat foods.

Inclusion of Reduced Graphene Oxide to Silk Fibroin Hydrogels Improve the Conductive, Swelling and Wound Healing Capacity

Developing dressing for wound dressings represents a significant challenge for the scientific community. In this study, a conductive hydrogel was synthesized to promote the wound‐healing process. This hydrogel is composed of silk fibroin (SF), reduced graphene oxide (rGO), and glycerol (G). The impact of modifying the SF:rGO ratio, and the G content (%), on the physicochemical and biological properties. The hydrogels were characterized using FT‐IR, SEM, XRD, TGA, swelling, mechanical resistance, and conductivity. The cytotoxicity of the materials and their wound‐healing capacity in human fibroblasts were also determined. Chemical analysis revealed that the gelation of SF occurs due to the formation of β sheet structures, which was confirmed by the shift from amide I to amide II. An Increase in the SF:rGO ratio favored swelling behavior, although increasing G reduced this effect. The swelling of the hydrogel followed a Fick diffusion mechanism. Furthermore, the increase in the SF:rGO ratio and the percentage G improved the conductivity of the materials. The hydrogels were found to be non‐cytotoxic to human fibroblasts, and those containing rGO exhibited superior wound healing capacity compared to the positive control cell culture medium. Therefore, SF:rGO hydrogels could be considered promising candidates for wound dressing.

pH-responsive membranes: Mechanisms, fabrications, and applications

Understanding the mechanisms of pH-responsiveness allows researchers to design and fabricate membranes with specific functionalities for various applications. The pH-responsive membranes (PRMs) are particular categories of membranes that have an amazing aptitude to change their properties such as permeability, selectivity and surface charge in response to changes in pH levels. This review provides a brief introduction to mechanisms of pH-responsiveness in polymers and categorizes the applied polymers and functional groups. After that, different techniques for fabricating pH-responsive membranes such as grafting, the blending of pH-responsive polymers/microgels/nanomaterials, novel polymers and graphene-layered PRMs are discussed. The application of PRMs in different processes such as filtration membranes, reverse osmosis, drug delivery, gas separation, pervaporation and self-cleaning/antifouling properties with perspective to the challenges and future progress are reviewed. Lastly, the development and limitations of PRM fabrications and applications are compared to provide inclusive information for the advancement of next-generation PRMs with improved separation and filtration performance.

Poly(acrylic acid)-Sodium Alginate Superabsorbent Hydrogels Synthesized by Electron-Beam Irradiation-Part II: Swelling Kinetics and Absorption Behavior in Various Swelling Media

Hybrid hydrogels with superabsorbent properties based on acrylic acid (20%), sodium alginate (0.5%) and poly(ethylene oxide) (0.1%) were obtained by electron-beam irradiation between 5 and 20 kGy, and are characterized by different physical and chemical methods; the first results reported showed gel fractions over 87%, cross-link densities under 9.9 × 103 mol/cm3 and swelling degrees of 400 g/g. Two types of hydrogels (without and with 0.1% initiator potassium persulfate) have been subjected to swelling and deswelling experiments in different swelling media with different pHs, chosen in accordance with the purpose for which these superabsorbent materials were obtained, i.e., water and nutrients carriers for agricultural purposes: 6.05 (distilled water), 7.66 (tap water), 5.40 (synthetic nutrient solution) and 7.45 (organic nutrient solution). Swelling kinetics and swelling dynamics have been also studied in order to investigate the influence of swelling media type and pH on the absorption phenomenon. The swelling and deswelling behaviors were influenced by the hydrogel characteristics and pH of the swelling media. Both the polymeric chain relaxation (non-Fickian diffusion) and macromolecular relaxation (super case II) phenomenon were highlighted as a function of swelling media type.

Antimicrobial Hydrogels Based on Cationic Curdlan Derivatives for Biomedical Applications

Hydrogels based on biocompatible polysaccharides with biological activity that can slowly release an active principle at the wound site represent promising alternatives to traditional wound dressing materials. In this respect, new hydrogels based on curdlan derivative with 2-hydroxypropyl dimethyl octyl ammonium groups (QCurd) and native curdlan (Curd) were obtained at room temperature by covalent cross-linking using a diepoxy cross-linking agent. The chemical structure of the QCurd/Curd hydrogels was investigated by Fourier transform infrared spectroscopy (FTIR) spectroscopy. Scanning electron microscopy (SEM) revealed well-defined regulated pores with an average diameter between 50 and 75 μm, and hydrophobic micro-domains of about 5 μm on the pore walls. The high swelling rate (21-24 gwater/ghydrogel) and low elastic modulus values (7-14 kPa) make them ideal for medical applications as wound dressings. To evaluate the possible use of the curdlan-based hydrogels as active dressings, the loading capacity and release kinetics of diclofenac, taken as a model drug, were studied under simulated physiological skin conditions. Several mathematical models have been applied to evaluate drug transport processes and to calculate the diffusion coefficients. The prepared QCurd/Curd hydrogels were found to have good antibacterial properties, showing a bacteriostatic effect after 48 h against S. aureus, MRSA, E. coli, and P. aeruginosa. The retarded drug delivery and antimicrobial properties of the new hydrogels support our hypothesis that they are candidates for the manufacture of wound dressings.

Chitosan-based hydrogels: From preparation to applications, a review

Chitosan, derived from the deacetylation of chitin, is an abundant natural biopolymer on earth. Chitosan and its derivatives have become promising biological materials because of their unique molecular structure and excellent biological activities. The reactive functional groups of chitosan such as the amino and hydroxyl groups play a crucial role in facilitating the synthesis of three-dimensional hydrogel. Chitosan-based hydrogels have been widely used in medical, pharmaceutical, and environmental fields for years. Nowadays, chitosan-based hydrogels have been found in a wide range of applications in the food industry such as food sensors, dye adsorbents and nutrient carriers. In this review, recently developed methods for the preparation of chitosan-based hydrogels were given, and the biological activities of chitosan-based hydrogels were systematically introduced. Additionally, the recent progress in food sensors, packaging, dye adsorbents, and nutrient carriers was discussed. Finally, the challenges and prospects for the future development of chitosan-based hydrogels were discussed.

Advances in Membrane Separation for Biomaterial Dewatering

Biomaterials often contain large quantities of water (50-98%), and with the current transition to a more biobased economy, drying these materials will become increasingly important. Contrary to the standard, thermodynamically inefficient chemical and thermal drying methods, dewatering by membrane separation will provide a sustainable and efficient alternative. However, biomaterials can easily foul membrane surfaces, which is detrimental to the performance of current membrane separations. Improving the antifouling properties of such membranes is a key challenge. Other recent research has been dedicated to enhancing the permeate flux and selectivity. In this review, we present a comprehensive overview of the design requirements for and recent advances in dewatering of biomaterials using membranes. These recent developments offer a viable solution to the challenges of fouling and suboptimal performances. We focus on two emerging development strategies, which are the use of electric-field-assisted dewatering and surface functionalizations, in particular with hydrogels. Our overview concludes with a critical mention of the remaining challenges and possible research directions within these subfields.

Exploring modified chitosan-based gene delivery technologies for therapeutic advancements

One of the critical steps in gene therapy is the successful delivery of the genes. Immunogenicity and toxicity are major issues for viral gene delivery systems. Thus, non-viral vectors are explored. A cationic polysaccharide like chitosan could be used as a nonviral gene delivery vector owing to its significant interaction with negatively charged nucleic acid and biomembrane, providing effective cellular uptake. However, the native chitosan has issues of targetability, unpacking ability, and solubility along with poor buffer capability, hence requiring modifications for effective use in gene delivery. Modified chitosan has shown that the "proton sponge effect" involved in buffering the endosomal pH results in osmotic swelling owing to the accumulation of a greater amount of proton and chloride along with water. The major challenges include limited exploration of chitosan as a gene carrier, the availability of high-purity chitosan for toxicity reduction, and its immunogenicity. The genetic drugs are in their infancy phase and require further exploration for effective delivery of nucleic acid molecules as FDA-approved marketed formulations soon.

Wetting and swelling behaviour of N-acetylated thin chitosan coatings in aqueous media

Chitosan nanocoatings (thickness range of 120-540 nm) were produced on glass, zinc and silicon substrates with dip-coating and spin coating techniques to study their pH-dependent wetting and swelling behaviour. The coatings were N-acetylated with the methanolic solution of acetic anhydride to increase the degree of acetylation from 36 % to 100 % (according to ATR-FTIR studies). The measured contact angles of Britton-Robinson (BR) buffer solutions (pH 6.0, 7.4 and 9.0) were lower on the acetylated surfaces (ca. 50°), than that of their native counterparts (ca. 70°) and does not depend on the pH. Contrary, contact angles on the native coating deteriorated 10°-15° with increasing the pH. In addition, for native coatings, the decrease of the contact angles over time also showed a pH dependence: at pH 9.0 the contact angle decreased by 7° in 10 min, while at pH 6.0 it decreased by 13° and at a much faster rate. The constraint swelling of the coatings in BR puffer solutions was studied in situ by scanning angle reflectometry. The swelling degree of the native coatings increased significantly with decreasing pH (from 250 % to 500 %) due to the increased number of protonated amino groups, while the swelling degree of acetylated coatings was ca. 160 % regardless of the pH. The barrier properties of the coatings were studied by electrochemical tests on zinc substrates. The analysis of polarization curves showed the more permeable character of the acetylated coatings despite the non-polar character of the bulk coating matrix. It can be concluded that in the case of native coatings, 49 % of the absorbed water is in bound form, which does not assist ion transport, while in the case of acetylated coatings, this value is only 33 %.

Polyelectrolyte-based solid dispersions for enhanced dissolution and pH-Independent controlled release of sildenafil citrate

The aim of this study was to design a novel matrix tablet with enhanced dissolution and pH-independent controlled release of sildenafil citrate (SIL), a drug with pH-dependent solubility, by using solid dispersions (SDs) and polyelectrostatic interactions. SIL-loaded SDs were prepared using various polymeric carriers such as poloxamer 188, poloxamer 407, Soluplus®, polyvinylpyrrolidone (PVP) K 12, and PVP K 17 by the solvent evaporation method. Among these polymers, Soluplus® was found to be the most effective in SDs for enhancing the drug dissolution over 6 h in pH 6.8 intestinal fluid. SIL was well dispersed in Soluplus®-based SDs in an amorphous form. When the Soluplus®-based SDs were added in the tablet containing positively charged chitosan and negatively charged Eudragit® L100, the drug release rate was further modulated in a controlled manner. The charge density of the tablet was higher at pH 6.8 than at pH 1.2 due to the polyelectrostatic interaction between chitosan and Eudragit® L100. This interaction could provide a pH-independent controlled release of SIL. Our study demonstrates that a combinatory approach of Soluplus®-based SDs and polyelectrostatic interactions can improve the dissolution and pH-independent release performance of SIL. This approach could be a promising pharmaceutical strategy to design a matrix tablet of poorly water-soluble drugs for the enhanced bioavailability.

Magnetic Hydrogel Microrobots as Insecticide Carriers for In Vivo Insect Pest Control in Plants

The cost of insect pests to human society exceeds USD70 billion per year worldwide in goods, livestock, and healthcare services. Therefore, pesticides are needed to prevent insect damage despite the secondary effects of these chemical agents on non-target organisms. Chemicals encapsulation into carriers is a promising strategy to improve their specificity. Hydrogel-based microrobots show enormous potential as chemical carriers. Herein, hydrogel chitosan magnetic microrobots encapsulating ethyl parathion (EP)-CHI@Fe3 O4 are used to efficiently kill mealworm larvae (Tenebrio molitor). The mechanism takes advantage of pH-responsive chitosan degradation at Tenebrio molitor midgut pH to efficiently deliver pesticide into the mealworm intestinal tract in just 2 h. It is observed that under a transversal rotating magnetic field, mealworm populations show higher mortality after 30 min compared to free pesticide. This example of active pesticide carriers based on soft microrobots opens new avenues for microrobots applications in the agrochemical field as active chemical carriers.

Nano-residronate loaded κ-carrageenan-based injectable hydrogels for bone tissue regeneration

Bone tissue possesses intrinsic regenerative capabilities to address deformities; however, its ability to repair defects caused by severe fractures, tumor resections, osteoporosis, joint arthroplasties, and surgical reconsiderations can be hindered. To address this limitation, bone tissue engineering has emerged as a promising approach for bone repair and regeneration, particularly for large-scale bone defects. In this study, an injectable hydrogel based on kappa-carrageenan-co-N-isopropyl acrylamide (κC-co-NIPAAM) was synthesized using free radical polymerization and the antisolvent evaporation technique. The κC-co-NIPAAM hydrogel's cross-linked structure was confirmed using Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance (1H NMR). The hydrogel's thermal stability and morphological behavior were assessed using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively. Swelling and in vitro drug release studies were conducted at varying pH and temperatures, with minimal swelling and release observed at low pH (1.2) and 25 °C, while maximum swelling and release occurred at pH 7.4 and 37oC. Cytocompatibility analysis revealed that the κC-co-NIPAAM hydrogels were biocompatible, and hematoxylin and eosin (H&E) staining demonstrated their potential for tissue regeneration and enhanced bone repair compared to other experimental groups. Notably, digital x-ray examination using an in vivo bone defect model showed that the κC-co-NIPAAM hydrogel significantly improved bone regeneration, making it a promising candidate for bone defects.

A nanofluidic sensing platform based on robust and flexible graphene oxide/chitosan nanochannel membranes for glucose and urea detection

We present the development of a health-monitoring nanofluidic membrane utilizing biocompatible and biodegradable graphene oxide, chitosan, and graphene quantum dots. The nanoconfinement provided by graphene oxide nanolayers encapsulates chitosan molecules, allowing for their conformational changes and switchable hydrophobic-hydrophilic behavior in response to pH variations. This low-dimensional membrane operates as an array of nanofluidic channels that can release quantum dots upon pH change. The photoluminescence emission from quantum dots enables rapid and reliable optical visualization of pH changes, facilitating efficient human health monitoring. To ensure fouling prevention and enable multiple usages, we adopt a design approach that avoids direct contact between biomarkers and the nanochannels. This design strategy, coupled with good mechanical properties (Young's modulus of 5.5 ± 0.7 GPa), preserves the integrity and functionality of the sensors for repeated sensing cycles. Furthermore, leveraging the memory effect, our sensors can be reloaded with graphene quantum dots multiple times without significant loss of selectivity, achieving reusability. The wide-ranging capabilities of 2D materials and stimuli-responsive polymers empower our sustainable approach to designing low-dimensional, robust, and flexible sensing materials. This approach allows for the integration of various biorecognition elements and signal transduction modes, expanding the versatility and applications of the designed materials.

pH-responsive chitosan/acrylamide/gold/nanocomposite supported with silver nanoparticles for controlled release of anticancer drug

In this study, we prepared a pH-responsive nanocomposite hydrogel based on chitosan grafted with acrylamide monomer and gold nanoparticles using gamma irradiation method (Cs-g-PAAm/AuNPs). The nanocomposite was enhanced with a layer coating of silver nanoparticles to improve the controlled release of the anticancer drug fluorouracil while increasing antimicrobial activity and decreasing the cytotoxicity of silver nanoparticles in nanocomposite hydrogel by combining with gold nanoparticles to enhance the ability to kill a high number of liver cancer cells. The structure of the nanocomposite materials was studied using FTIR spectroscopy and XRD patterns, which demonstrated the entrapment of gold and silver nanoparticles within the prepared polymer matrix. Dynamic light scattering data revealed the presence of gold and silver in the nanoscale with the polydispersity indexes in the mid-range values, indicating that distribution systems work best. Swelling experiments at various pH levels revealed that the prepared Cs-g-PAAm/Au-Ag-NPs nanocomposite hydrogels were highly responsive to pH changes. Bimetallic pH-responsive Cs-g-PAAm/Au-Ag-NPs nanocomposites exhibit strong antimicrobial activity. The presence of AuNPs reduced the cytotoxicity of AgNPs while increasing their ability to kill a high number of liver cancer cells.Cs-g-PAAm/Au-Ag-NPs has a high amount of fluorouracil drug loaded at pH 7.4 reaching 95 mg/g with a maximum drug release of 97% within 300 min. Cs-g-PAAm/Au-Ag-NPs have been recommended to use as oral delivery of anticancer drugs because they secure the encapsulated drug in the acidic medium of the stomach and release it in the intestinal pH.

Chitosan/snail slime films as multifunctional platforms for potential biomedical and cosmetic applications: physical and chemical characterization

Due to the pollution problem, the use of more sustainable materials with a reduced environmental impact, spanning across biocompatible and biodegradable polymers, is growing worldwide in many different fields, particularly when referring to applications in Life Sciences. Accordingly, with the aim of developing multifunctional materials for potential cosmetic/biomedical purposes, this work reports the physical and chemical characterization of chitosan-based films blended with snail slime, exhibiting antioxidant and sunscreen features. A suitable formulation for preparing free-standing chitosan platforms, mixing low molecular weight chitosan, lactic acid, glycerol, and snail slime into an appropriate ratio, is thus described. The results obtained by morphological analysis and ATR-FTIR spectroscopy, XRD, swelling analysis (also when varying pH, ionic strength, and temperature), and WVTR measurements evidence a uniform distribution of snail slime inside the chitosan network, forming more compacted structures. At first, the UV-Vis analysis is used to investigate the theoretical Sun Protection Factor, finding that these innovative platforms can be used for preventing sunburn. Then, the antioxidant features are investigated using the ABTS assay, displaying a snail slime-mediated and dose-dependent boosted activity.

3D Matrices for Enhanced Encapsulation and Controlled Release of Anti-Inflammatory Bioactive Compounds in Wound Healing

Current trends in the development of wound dressings are oriented towards the use of biopolymer-based materials, due to their unique properties such as non-toxicity, hydrophilicity, biocompatibility and biodegradability, properties that have advantageous therapeutic characteristics. In this regard, the present study aims to develop hydrogels based on cellulose and dextran (CD) and to reveal their anti-inflammatory performance. This purpose is achieved by incorporating plant bioactive polyphenols (PFs) in CD hydrogels. The assessments include establishing the structural characteristics using attenuated total reflection Fourier transformed infrared (ATR-FTIR) spectroscopy, the morphology by scanning electron microscopy (SEM), the swelling degree of hydrogels, the PFs incorporation/release kinetics and the hydrogels' cytotoxicity, together with evaluation of the anti-inflammatory properties of PFs-loaded hydrogels. The results show that the presence of dextran has a positive impact on the hydrogel's structure by decreasing the pore size at the same time as increasing the uniformity and interconnectivity of the pores. In addition, there is an increased degree of swelling and of the encapsulation capacity of PFs, with the increase of the dextran content in hydrogels. The kinetics of PFs released by hydrogels was studied according to the Korsmeyer-Peppas model, and it was observed that the transport mechanisms depend on hydrogels' composition and morphology. Furthermore, CD hydrogels have been shown to promote cell proliferation without cytotoxicity, by successfully culturing fibroblasts and endothelial cells on CD hydrogels (over 80% viability). The anti-inflammatory tests performed in the presence of lipopolysaccharides demonstrate the anti-inflammatory properties of the PFs-loaded hydrogels. All these results provide conclusive evidence on the acceleration of wound healing by inhibiting the inflammation process and support the use of these hydrogels encapsulated with PFs in wound healing applications.

Chitosan Based Materials in Cosmetic Applications: A Review

This review provides a report on the properties and recent advances in the application of chitosan and chitosan-based materials in cosmetics. Chitosan is a polysaccharide that can be obtained from chitin via the deacetylation process. Chitin most commonly is extracted from cell walls in fungi and the exoskeletons of arthropods, such as crustaceans and insects. Chitosan has attracted significant academic interest, as well as the attention of the cosmetic industry, due to its interesting properties, which include being a natural humectant and moisturizer for the skin and a rheology modifier. This review paper covers the structure of chitosan, the sources of chitosan used in the cosmetic industry, and the role played by this polysaccharide in cosmetics. Future aspects regarding applications of chitosan-based materials in cosmetics are also mentioned.

Soft Magnetic Microrobots for Photoactive Pollutant Removal

"Soft" robotics based on hydrogels appears as an alternative to the traditional technology of "hard" robotics. Soft microrobots are employed for drug delivery and cell manipulation. This work develops magnetic hydrogel-based microrobots using chitosan (CHI) as the body of the micromotor and Fe₃ O₄ nanoparticles to allow for its magnetic actuation. In addition, ZnO nanoparticles are incorporated inside the CHI body of the microrobot to act as an active component for pollutants photodegradation. CHI@Fe₃ O₄ -ZnO microrobots are used for the efficient photodegradation of persistent organic pollutants (POPs). The high absorption of CHI hydrogel enhances the POP photodegradation, degrading it 75% in just 30 min. The adsorption-degradation and magnetic properties of CHI@Fe₃ O₄ -ZnO microrobots are used in five cycles while maintaining up to 60% photodegradation efficiency. The proof-of-concept present in this work represents a simple way to obtain soft microrobots with magnetic actuation and photodegradation functionalities for several water purification applications.

Influence of Gel Stage from Cellulose Dissolution in NaOH-Water System on the Performances of Cellulose Allomorphs-Based Hydrogels

Novel hydrogels were prepared starting from different cellulose allomorphs (cellulose I, II, and III), through a swelling stage in 8.5% NaOH aqueous solution, followed by freezing at low temperature (−30 °C), for 24 h. After thawing at room temperature, the obtained gels were chemical cross-linked with epichlorohydrin (ECH), at 85 °C. The swelling degrees of the hydrogels were investigated, and a complex dependence on the type of the cellulose allomorph was found. Moreover, the gel stage has been shown to play a key role in the design of hydrogels with different performances, following the series: H-CII > H-CI > H-CIII. The correlations between the allomorph type and the morphological characteristics of hydrogels were established by scanning electron microscopy (SEM). The hydrogel H-CII showed the biggest homogeneous pores, while H-CIII had the most compacted pores network, with small interconnected pores. The rheological studies were performed in similar shear regimes, and a close correlation between the strength of the gel structure and the size of the gel fragments was observed. In the case of hydrogels, it has been shown that H-CII is softer, with a lower resistance of the hydrogel (G′) above the oscillation frequencies tested, but it maintains its stable structure, while H-CIII has the highest modulus of storage and loss compared to H-CI and H-CII, having a stronger and more rigid structure. The X-ray diffraction (XRD) method showed that the crystalline organization of each type of allomorph possesses a distinctive diffraction pattern, and, in addition, the chemically cross-linking reaction has been proved by a strong decrease of the crystallinity. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy provided clear evidence of the chemical cross-linking of cellulose allomorphs with ECH, by the alteration of the crystal structure of cellulose allomorphs and by the formation of new ether bands.

Synthesis and characterization of photosensitive gelatin-based hydrogels for photodynamic therapy in HeLa-CCL2 cell line

BACKGROUND

Hydrogel systems are increasingly gaining visibility involving biomedicine, tissue engineering, environmental treatments, and drug delivery systems. These systems have a three-dimensional network composition and high-water absorption capacity, are biocompatible, allowing them to become an option as photosensitizer carriers (PS) for applications in Photodynamic Therapy (PDT) protocols.

METHODS

A nanohydrogel system (NAHI), encapsulated with chloroaluminium phthalocyanine (ClAlPc) was synthesized for drug delivery.. NAHI was synthesized using gelatin as based polymer by the chemical cross-linking technique. The drug was encapsulated by immersing the hydrogel in a 1.0 mg.mL^-1 ClAlPc solution. The external morphology of NAHI was examined by scanning electron microscopy (SEM). The degree of swelling of the synthesized system was evaluated to determine the water absorption potential. The produced nanohydrogel system was characterized by photochemical, photophysical and photobiologial studies.

RESULTS

The images from the SEM analysis showed the presence of three-dimensional networks in the formulation. The swelling test demonstrated that the nanohydrogel freeze-drying process increases its water holding capacity. All spectroscopic results showed excellent photophysical parameters of the drug studied when served in the NAHI system. The incorporation efficiency was 70%. The results of trypan blue exclusion test have shown significant reduction (p < 0.05) in the cell viability for all groups treated with PDT, in all concentrations tested. In HeLa cells, PDT mediated by 0,5 mg.mL^-1 ClAlPc encapsulated in NAHI showed a decrease in survival close to 95%. In the internalization cell study was possible to observe the internalization of phthalocyanine after one hour of incubation, at 37 °C, with the the accumulation of PS in the cytoplasm and inside the nucleus at both concentrations tested.

CONCLUSIONS

Given the peculiar performance of the selected system, the resulting nanohydrogel is a versatile platform and display potential applications as controlled delivery systems of photosensitizer for photodynamic therapy application.

Imination of Microporous Chitosan Fibers-A Route to Biomaterials with "On Demand" Antimicrobial Activity and Biodegradation for Wound Dressings

Microporous chitosan nanofibers functionalized with different amounts of an antimicrobial agent via imine linkage were prepared by a three-step procedure including the electrospinning of a chitosan/PEO blend, PEO removal and acid condensation reaction in a heterogeneous system with 2-formylphenylboronic acid. The fibers’ characterization was undertaken keeping in mind their application to wound healing. Thus, by FTIR and ¹H-NMR spectroscopy, it was confirmed the successful imination of the fibers and the conversion degree of the amine groups of chitosan into imine units. The fiber morphology in terms of fiber diameter, crystallinity, inter- and intra-fiber porosity and strength of intermolecular forces was investigated using scanning electron microscopy, polarized light microscopy, water vapor sorption and thermogravimetric analysis. The swelling ability was estimated in water and phosphate buffer by calculating the mass equilibrium swelling. The fiber biodegradation was explored in five media of different pH, corresponding to different stages of wound healing and the antimicrobial activity against the opportunistic pathogens inflicting wound infection was investigated according to standard tests. The biocompatibility and bioadhesivity were studied on normal human dermal fibroblast cells by direct contact procedure. The dynamic character of the imine linkage of the functionalized fibers was monitored by UV-vis spectroscopy. The results showed that the functionalization of the chitosan microporous nanofibers with antimicrobial agents via imine linkage is a great route towards bio-absorbable wound dressings with “on demand” antimicrobial properties and biodegradation rate matching the healing stages.

β-cyclodextrin chitosan-based hydrogels with tunable pH-responsive properties for controlled release of acyclovir: design, characterization, safety, and pharmacokinetic evaluation

In this work, series of pH-responsive hydrogels (FMA1-FMA9) were synthesized, characterized, and evaluated as potential carrier for oral delivery of an antiviral drug, acyclovir (ACV). Different proportions of β-cyclodextrin (β-CD), chitosan (CS), methacrylic acid (MAA) and N' N'-methylenebis-acrylamide (MBA) were used to fabricate hydrogels via free radical polymerization technique. Fourier transform infrared spectroscopy confirmed fabrication of new polymeric network, with successful incorporation of ACV. Scanning electron microscopy (SEM) indicated presence of slightly porous structure. Thermal analysis indicated enhanced thermal stability of polymeric network. Swelling studies were carried out at 37 °C in simulated gastric and intestinal fluids. The drug release data was found best fit to zero-order kinetics. The preliminary investigation of developed hydrogels showed a pH-dependent swelling behavior and drug release pattern. Acute oral toxicity study indicated no significant changes in behavioral, clinical, or histopathological parameters of Wistar rats. Pharmacokinetic study indicated that developed hydrogels caused a significant increase in oral bioavailability of ACV in rabbit plasma as compared to oral suspension when both were administered at a single oral dose of 20 mg kg-1 bodyweight. Hence, developed hydrogel formulation could be used as potential candidate for controlled drug delivery of an antiviral drug acyclovir.

Development of Antibacterial, Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels' crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker-Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R2 = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.

Entrapment of Hydrophilic and Hydrophobic Molecules in Beads Prepared from Isolated Denatured Whey Protein

The oral route of administration is by far the most convenient route, especially in the treatment of chronic conditions. However, many therapeutics present formulation difficulties which make them unsuitable for oral delivery. Recently, we synthesized a denatured whey protein isolate (dWPI) bead entrapped with insulin. Our present goal was to assess the suitability of this delivery system to the delivery of other potential molecules, both hydrophilic and hydrophobic. Beads of 1.2–1.5 mm in diameter were entrapped with four payloads representing a range of solubilities. The water-soluble payloads were sodium fluorescein (SF) and FITC dextran 4000 Da (FD4), while the hydrophobic ones were Fast Green and curcumin. Encapsulation efficiency (EE) was 73%, 84%, 70%, and 83% for SF, FD4, Fast Green, and curcumin-loaded beads, respectively. The corresponding loading capacity for each bead was 0.07%, 1.1%, 0.75%, and 1.1%, respectively. Each payload produced different release profiles in simulated gastric fluid (SGF) and simulated intestinal fluids (SIF). SF released steadily in both SGF and SIF. FD4 and curcumin release was not substantial in any buffers, while Fast Green release was low in SGF and high in SIF. The differences in release behaviour were likely due to the varying properties of the payloads. The effect of proteolysis on beads suggested that enzymatic degradation of the whey bead may promote payload release. The beads swelled rapidly in SGF compared to SIF, which likely contributed to the release from the beads, which was largely governed by solvent diffusion and polymer relaxation. Our results offer a systematic examination of the behaviour of hydrophilic and hydrophobic payloads in a dWPI delivery system. These beads may be further designed to orally deliver poorly permeable macromolecules and poorly soluble small molecules of pharmaceutical interest.

Gamma radiation synthesis of a novel amphiphilic terpolymer hydrogel pH-responsive based chitosan for colon cancer drug delivery

Particularly, chitosan (Cs) loaded with drug cannot pass through the colonic region, often leading in the bursting drug release in the stomach due to its solubility in gastric contents. The novelty of the current article is to solve this limitation by performing gamma irradiation cross-linking of Cs with two anionic polymers of (acrylic acid)-co-(2-acrylamido-2-methylpropane-sulfonic acid) (AAc/AMPS) to give amphiphilic hydrogel. The shifted in the characteristic FTIR peaks of Cs in the (Cs/AAc/AMPS) confirm the exits of inter-molecular interactions that make Cs and (AAc/AMPS) are miscible. Swelling experiments under different pH indicated that the (Cs/AAc/AMPS) hydrogels were significantly sensitive to pH change. The results give the possibility to use the obtained (Cs/AAc/AMPS) hydrogel on drug delivery system. The in vitro Fluorouracil (5-FU) releasing from (Cs/AAc/AMPS) matrix was examined under the influence of pH1 and pH7.The results confirmed the hydrogels capability to release 96 % of 5-FU drug at pH 7 after 7 h.

Chitosan/alginate/hyaluronic acid polyelectrolyte composite sponges crosslinked with genipin for wound dressing application

Wound dressing composed of polyelectrolyte complexes (PECs), based on chitosan/alginate/hyaluronic acid (CS/ALG/HYA) crosslinked by genipin, was prepared by freeze-dried molding. Genipin as excellent natural biological crosslinker was chose for high biocompatibility and improving mechanical properties of materials. The CS/ALG/HYA sponges (CAHSs) were characterized by FTIR, XRD, DSC and SEM. Porosity, swelling behavior and mechanical properties and in vitro degradation of CAHSs were investigated. The cytotoxicity assay was carried out on HUVEC cells in vitro and the result proves the good biocompatibility of CAHSs. Hemolysis tests indicated that the prepared CAHSs were non-hemolytic material (hemolysis ratio < 5%, no cytotoxicity). PT and aPPT coagulation tests demonstrated that CAHS2 and CAHS3 could both activate the extrinsic and intrinsic coagulation pathway and thus accelerated blood coagulation. Further, in a rat full-thickness wounds model, the CAHS2 sponge significantly facilitates wound closure compared to other groups. CAHSs exhibited adjustable physical, mechanical and biological properties. Thus, the chitosan-based polyelectrolyte composite sponges exhibit great potential as promising wound dressings.

Examining the Impact of Squaric Acid as a Crosslinking Agent on the Properties of Chitosan-Based Films

Hydrogels based on chitosan are very versatile materials which can be used for tissue engineering as well as in controlled drug delivery systems. One of the methods for obtaining a chitosan-based hydrogel is crosslinking by applying different components. The objective of the present study was to obtain a series of new crosslinked chitosan-based films by means of solvent casting method. Squaric acid-3,4-dihydroxy-3-cyclobutene-1,2-dione-was used as a safe crosslinking agent. The effect of the squaric acid on the structural, mechanical, thermal, and swelling properties of the formed films was determined. It was established that the addition of the squaric acid significantly improved Young's modulus, tensile strength, and thermal stability of the obtained materials. Moreover, it should be stressed that the samples consisting of chitosan and squaric acid were characterized by a higher swelling than pure chitosan. The detailed characterization proved that squaric acid could be used as a new effective crosslinking agent.

Structural characterization and developability assessment of sustained release hydrogels for rapid implementation during preclinical studies

Sustained-release formulations are important tools to convert efficacious molecules into therapeutic products. Hydrogels enable the rapid assessment of sustained-release strategies, which are important during preclinical development where drug quantities are limited and fast turnaround times are the norm. Most research in hydrogel-based drug delivery has focused around synthesizing new materials and polymers, with limited focus on structural characterization, technology developability and implementation. Two commercially available thermosensitive hydrogel systems, comprised of block copolymers of poly(lactic-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) (PLGA) and poly(lactide-co-caprolactone)-b-poly(ethyleneglycol)-b-poly(lactide-co-caprolactone) (PLCL), were evaluated during this study. The two block copolymers described in the study were successfully formulated to form hydrogels which delayed the release of lysozyme (> 20 days) in vitro. Characterization of formulation attributes of the hydrogels like T_sol-gel temperature, complex viscosity and injection force showed that these systems are amenable to rapid implementation in preclinical studies. Understanding the structure of the gel network is critical to determine the factors controlling the release of therapeutics out of these gels. The structures were characterized via the gel mesh sizes, which were estimated using two orthogonal techniques: small angle X-ray scattering (SAXS) and rheology. The mesh sizes of these hydrogels were larger than the hydrodynamic radius (size) of lysozyme (drug), indicating that release through these gels is expected to be diffusive at all time scales rather than sub-diffusive. In vitro drug release experiments confirm that diffusion is the dominating mechanism for lysozyme release; with no contribution from degradation, erosion, relaxation, swelling of the polymer network or drug-polymer interactions. PLGA hydrogel was found to have a much higher complex viscosity than PLCL hydrogel, which correlates with the slower diffusivity and release of lysozyme seen from the PLGA hydrogel as compared to PLCL hydrogel. This is due to the increased frictional drag experienced by the lysozyme molecule in the PLGA hydrogel network, as described by the hydrodynamic theory.

Synthesis and characterization of Schiff base containing bovine serum albumin-gum arabic aldehyde hybrid nanogels via inverse miniemulsion for delivery of anticancer drug

The periodate modified gum arabic was used as a natural-based, non-toxic cross-linker to synthesize hybrid bovine serum albumin-gum arabic aldehyde (BSA-GAA) nanogels by Schiff base reaction through the inverse miniemulsion method for the first time. The synthesis process was performed in the absence of toxic organic solvents using fractionated coconut oil as the continuous phase. The particle size of the nanogels was managed by tweaking the concentration of the surfactants (Span 80/Tween 80) and the total volume of the aqueous phase. Based on the bicinchoninic acid method, the cross-linking efficiency of BSA and GAA was estimated at 98%. 5-fluorouracil (5-FU) was selected as the sample drug. The 5-FU-loaded hybrid nanogels showed a spherical morphology with an average diameter of 231.33 ±12.74 nm and a zeta potential of -31.6 mV. The encapsulation and loading efficiency of the nanogels were calculated at 42 ± 4.52% and 2.37 ± 0.59%, respectively. The properties of the hybrid nanogels were analyzed by dynamic light scattering (DLS), Fourier transform infrared microscopy (FTIR) analysis, field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). The pH sensitivity of the hybrid nanogels was confirmed by the in vitro release profiles of 5-FU in different buffers. Hemolysis assay revealed the in vitro hemocompatibility of the hybrid nanogels which inhibited the growth of MCF-7 cells with an IC50 value of 16.21 μM. The present study suggested that these biobased hybrid nanogels could have a great potential in drug delivery and other biomedical applications.

Dual ionic liquid-based crosslinked chitosan for fine-tuning of antifouling, water throughput, and denitrification performance of polysulfone membrane

This study aimed to design a facile and efficient protocol for upgrading the performance indices of polysulfone (PS) membrane (porosity, hydrophilicity, pure water flux (PWF), surface charge, and fouling-resistance) by blending with newly synthesized poly(ionic) crosslinked chitosan Schiff bases (PICCSBs). The PS-PICCSBs mixed-matrix membranes (MMMs) have successfully fabricated and characterized based on spectral and microscopic analyses, porosity, zeta potential, water contact angle, and water uptake (wettability) measurements. The PWF, fouling-resistance against bovine serum albumin (BSA), as well as ion exchange capacity (IEC) against nitrate anion were studied. The wettability, hydrophilicity and overall porosity of new MMMs have greatly increased, in comparison to a pristine PS membrane (M₀). In addition, blending of PS with PICCSBs resulted in switching its surface from negatively- to positively-charged. The PWF of MMMs has increased to reach a maximum value of 238.6 L/m² h for MMM₁ (9.3-fold higher than M₀). Meanwhile, BSA rejection has declined from 96.62% for M₀ to 41.9% for MMM₁. The fouling parameters results of MMMs indicated their low fouling propensity. The IEC of nitrate anions revealed that the nitrate uptake by MMM₁ is higher than that for M₀ and MMM₂ by 34% and 14%, respectively.

Development of curcumin-loaded chitosan/pluronic membranes for wound healing applications

The emergence of new materials with improved antibacterial, anti-inflammatory and healing properties compared to conventional wound dressings has both social and economic appeal. In this study, novel chitosan-based (CTS) membranes containing curcumin (CUR) incorporated in Pluronic (PLU) copolymers were developed and characterized to obtain suitable properties for applications as a wound healing dressing. The mechanical, thermal, swelling, wettability, release and permeation properties were evaluated by DSC, TGA, water contact angle measurements, FTIR, fluorescence and microscopic techniques. Membranes containing PLU and CUR presented wettability close to the ideal range for interaction with cellular components (contact angle ~40-70°), improved mechanical properties, higher thermal stability, high swelling degree (>800%) and CUR release (~60%) compared to samples without PLU addition. A higher retention of CUR in the epidermis than in the dermis layer was observed, which also was confirmed by confocal microscopy. Furthermore, the CTS-PLU membranes loaded with CUR showed to be active against Staphylococcus aureus and Pseudomonas aeruginosa (MIC = 25 and 100 mg mL^-1, respectively), the microbial species most present in chronic wounds. Overall, the CTS-PLU-CUR membranes presented suitable properties to act as a new wound healing dressing formulation and in vivo studies should be performed to confirm these benefits.

Hydrogel membranes: A review

Hydrogel membranes (HMs) are defined and applied as hydrated porous media constructed of hydrophilic polymers for a broad range of applications. Fascinating physiochemical properties, unique porous architecture, water-swollen features, biocompatibility, and special water content dependent transport phenomena in semi-permeable HMs make them appealing constructs for various applications from wastewater treatment to biomedical fields. Water absorption, mechanical properties, and viscoelastic features of three-dimensional (3D) HM networks evoke the extracellular matrix (ECM). On the other hand, the porous structure with controlled/uniform pore-size distribution, permeability/selectivity features, and structural/chemical tunability of HMs recall membrane separation processes such as desalination, wastewater treatment, and gas separation. Furthermore, supreme physiochemical stability and high ion conductivity make them promising to be utilised in the structure of accumulators such as batteries and supercapacitors. In this review, after summarising the general concepts and production processes for HMs, a comprehensive overview of their applications in medicine, environmental engineering, sensing usage, and energy storage/conservation is well-featured. The present review concludes with existing restrictions, possible potentials, and future directions of HMs.

Structure-property of crosslinked chitosan/silica composite films modified by genipin and glutaraldehyde under alkaline conditions

In this study, genipin and glutaraldehyde in varied concentrations were utilized in chitosan crosslinking under alkaline condition. A UV/Vis analysis was used to investigate the molecular structure of genipin and glutaraldehyde in an aqueous alkaline solution. The results showed the formation of glutaraldehyde dimer and polymerized genipin. The FTIR-ATR, SEM, DSC, XRD, mechanical properties, crosslinking degree and swelling ratio of chitosan based films crosslinked by genipin and glutaraldehyde were determined. The results indicated that the hydrogen bonds formed between genipin and chitosan enabled the films crosslinked by genipin (1 and 5 mmol/L) to have a higher degree of crosslinking, but a lower swelling ratio than glutaraldehyde (1 and 5 mmol/L). Genipin enabled the chitosan-based film to possess better mechanical properties and crystallinity than glutaraldehyde. The polymerization of genipin had a substantial effect on the network structure and swelling behavior of chitosan-based films crosslinked by genipin.

Switchable Hydrogel-Gated Organic Field-Effect Transistors

Stimuli-responsive hydrogels represent a class of materials capable of reversibly switching their morphological and physicochemical characteristics. An ultrathin poly(acrylic acid) film (ca. 6 nm) grafted onto the gate of a p-type EGOFET is studied, and the correlation between the swelling state of the hydrogel and the transistor output characteristics is presented. The hydrogel-related swelling process occurring in basic medium causes an increase in threshold voltage due to the abrupt and intense increase of the negative charge density on the gate electrode. The variation of the drain current during the in situ modification of the pH electrolyte allows a quantitative analysis of the hydrogel switching kinetics. This work shows not only the relevance of EGOFET as an analytical tool in the broad sense, i.e., able to follow in real time phase transition processes of stimuli-responsive materials, but also the relevance of using a hydrogel for field-effect-based (bio)detection according to the ability of such material to overcome the well-known Debye length problematics.