Hydrogel-Based Materials for Delivery of Herbal Medicines

The Combination of Bioactive Herbal Compounds with Biomaterials for Regenerative Medicine

Regenerative medicine aims to restore the function of diseased or damaged tissues and organs by cell therapy, gene therapy, and tissue engineering, along with the adjunctive application of bioactive molecules. Traditional bioactive molecules, such as growth factors and cytokines, have shown great potential in the regulation of cellular and tissue behavior, but have the disadvantages of limited source, high cost, short half-life, and side effects. In recent years, herbal compounds extracted from natural plants/herbs have gained increasing attention. This is not only because herbal compounds are easily obtained, inexpensive, mostly safe, and reliable, but also owing to their excellent effects, including anti-inflammatory, antibacterial, antioxidative, proangiogenic behavior and ability to promote stem cell differentiation. Such effects also play important roles in the processes related to tissue regeneration. Furthermore, the moieties of the herbal compounds can form physical or chemical bonds with the scaffolds, which contributes to improved mechanical strength and stability of the scaffolds. Thus, the incorporation of herbal compounds as bioactive molecules in biomaterials is a promising direction for future regenerative medicine applications. Herein, an overview on the use of bioactive herbal compounds combined with different biomaterial scaffolds for regenerative medicine application is presented. We first introduce the classification, structures, and properties of different herbal bioactive components and then provide a comprehensive survey on the use of bioactive herbal compounds to engineer scaffolds for tissue repair/regeneration of skin, cartilage, bone, neural, and heart tissues. Finally, we highlight the challenges and prospects for the future development of herbal scaffolds toward clinical translation. Overall, it is believed that the combination of bioactive herbal compounds with biomaterials could be a promising perspective for the next generation of regenerative medicine.

Platelet rich fibrin and simvastatin-loaded pectin-based 3D printed-electrospun bilayer scaffold for skin tissue regeneration

Designing multifunctional wound dressings is a prerequisite to prevent infection and stimulate healing. In this study, a bilayer scaffold (BS) with a top layer (TL) comprising 3D printed pectin/polyacrylic acid/platelet rich fibrin hydrogel (Pec/PAA/PRF) and a bottom nanofibrous layer (NL) containing Pec/PAA/simvastatin (SIM) was produced. The biodegradable and biocompatible polymers Pec and PAA were cross-linked to form hydrogels via Ca2+ activation through galacturonate linkage and chelation, respectively. PRF as an autologous growth factor (GF) source and SIM together augmented angiogenesis and neovascularization. Because of 3D printing, the BS possessed a uniform distribution of PRF in TL and an average fiber diameter of 96.71 ± 18.14 nm was obtained in NL. The Young's modulus of BS was recorded as 6.02 ± 0.31 MPa and its elongation at break was measured as 30.16 ± 2.70 %. The wound dressing gradually released growth factors over 7 days of investigation. Furthermore, the BS significantly outperformed other groups in increasing cell viability and in vivo wound closure rate (95.80 ± 3.47 % after 14 days). Wounds covered with BS healed faster with more collagen deposition and re-epithelialization. The results demonstrate that the BS can be a potential remedy for skin tissue regeneration.

Alginate based biomaterials for hemostatic applications: Innovations and developments

Development of the efficient hemostatic materials is an essential requirement for the management of hemorrhage caused by the emergency situations to avert most of the casualties. Such injuries require the use of external hemostats to facilitate the immediate blood clotting. A variety of commercially available hemostats are present in the market but most of them are associated with limitations such as exothermic reactions, low biocompatibility, and painful removal. Thus, fabrication of an ideal hemostatic composition for rapid blood clot formation, biocompatibility, and antimicrobial nature presents a real challenge to the bioengineers. Benefiting from their tunable fabrication properties, alginate-based hemostats are gaining importance due to their excellent biocompatibility, with >85 % cell viability, high absorption capacity exceeding 500 %, and cost-effectiveness. Furthermore, studies have estimated that wounds treated with sodium alginate exhibited a blood loss of 0.40 ± 0.05 mL, compared to the control group with 1.15 ± 0.13 mL, indicating its inherent hemostatic activity. This serves as a solid foundation for designing future hemostatic materials. Nevertheless, various combinations have been explored to further enhance the hemostatic potential of sodium alginate. In this review, we have discussed the possible role of alginate based composite hemostats incorporated with different hemostatic agents, such as inorganic materials, polymers, biological agents, herbal agents, and synthetic drugs. This article outlines the challenges which need to be addressed before the clinical trials and give an overview of the future research directions.

Characterization and biological evaluation of a novel flavonoid-collagen antioxidant hydrogel with cytoprotective properties

Reactive oxygen species (ROS) play a critical and important role during wound healing but excess ROS at the wound site can lead to cellular damage and sub-optimal healing. Minimizing oxidative damage to the wound site and any supplemental therapeutic cells can be achieved by delivering exogenous antioxidants. Collagen hydrogels are ideal wound care materials due to their biocompatibility, high water content, and porous, three-dimensional architecture. Yet, they lack the inherent antioxidant activity that could help mitigate excess ROS at a wound site. This work formulates and evaluates the in vitro biocompatibility and antioxidant capabilities of collagen-fibroblast hydrogels combined with the polyphenolic antioxidant luteolin. Collagen solutions mixed with luteolin readily assembled into robust hydrogels with increasing gel strength due to increasing concentrations of luteolin. SEM images confirmed a mean pore size of 2.2 μm and a drastically different macromolecular ultrastructure with extensive fine crosslinking relative to collagen. Adequate cell viability and metabolic activity of dermal fibroblasts cultured within the gels were measured across all formulations, resulting in higher antioxidant activity and more than double the protection to cells from oxidative damage than traditional collagen hydrogels. Given these results, luteolin-collagen hydrogels demonstrate the potential for superior wound-healing properties when compared to collagen alone.

Electrospun Scaffolds as Antimicrobial Herbal Extract Delivery Vehicles for Wound Healing

Herbal extracts have been used in traditional remedies since the earliest myths. They have excellent antimicrobial, anti-inflammatory, and antioxidant activities owing to various bioactive components in their structure. However, due to their inability to reach a target and low biostability, their use with a delivery vehicle has come into prominence. For this purpose, electrospun nanofibrous scaffolds have been widely preferred for the delivery and release of antimicrobial herbal extracts due to the flexibility and operational versatility of the electrospinning technique. Herein, we briefly reviewed the electrospun nanofibrous scaffolds as delivery systems for herbal extracts with a particular focus on the preclinical studies for wound-healing applications that have been published in the last five years. We also discussed the indirect effects of herbal extracts on wound healing by altering the characteristics of electrospun mats.

A self-indicating and antibacterial gelatine-chitosan blended hydrogel enabling real-time quality control and sustained bioactive agent delivery

Hydrogels are one type of materials that are widely exploited for bioactive agent delivery, partly owing to their high biocompatibility and low toxicity. When hydrogels are used as carriers, their performance in agent loading and sustained agent release are predominately determined by the gel structure, which can be largely affected by variations during gel preparation. Till now, effective and easy methods to enable monitoring of such variations in real time have been lacking, making quality control of the generated gel-based carrier technically challenging. To address this technical gap, in this study we take advantage of the clusteroluminogenic properties of gelatine and chitosan to generate a crosslinked blended hydrogel which not only shows intrinsic antibacterial properties and high tunability in delivery performance but also shows a self-indicating capacity to enable quality control during hydrogel preparation. Upon fitting the curves of agent release into different kinetic models, the release profiles of the agent-loaded gels have been found to follow the Higuchi model well, with the non-Fickian mechanism being the major mechanism of the release process. Along with their high efficiency in agent loading, our gels warrant further exploitation for use in bioactive agent delivery and related biomedical applications.

Novel succinoglycan dialdehyde/aminoethylcarbamoyl-β-cyclodextrin hydrogels for pH-responsive delivery of hydrophobic drugs

β-Cyclodextrin cross-linked succinoglycan dialdehyde hydrogels was prepared for hydrophobic drug delivery. Succinoglycan dialdehyde (SGDA) was synthesized from sodium periodate oxidation of succinoglycan isolated from Sinorhizobium meliloti Rm1021. Aminoethylcarbamoyl-β-cyclodextrin (ACD) was crosslinked with SGDA to form a succinoglycan dialdehyde/aminoethylcarbamoyl-β-cyclodextrin (SGDA/ACD) hydrogels. The SGDA/ACD hydrogels exhibited a 65.7 % improvement in storage modulus (G') and a 5.7-fold higher compressive strain than the SGDA/poly(ethylene glycol) diamine (PEG) hydrogels as controls. A hardly soluble drug, baicalein was used for the drug loading and release properties of SGDA/ACD hydrogels. Baicalein was released about 98 % within 48 h at pH 7.4, but not completely released even after 48 h at pH 2.0. In addition, at pH 7.4, only about 56 % of the baicalein loaded on the SGDA/PEG hydrogels was released within 48 h, while about 98 % of the baicalein loaded on the SGDA/ACD hydrogels was released within 48 h. It indicates that ACD significantly improved the solubilization efficacy of the baicalein. In vitro testing of cell viability using HEK-293 cells also showed that the SGDA/ACD hydrogels were suitable for the cells. In conclusion, SGDA/ACD hydrogels significantly enhance the utilization of baicalein and provide potential applications in drug delivery systems for hardly soluble drugs.

In Situ Nanoarchitectonics of a MOF Hydrogel: A Self-Adhesive and pH-Responsive Smart Platform for Phototherapeutic Delivery

Metal-organic frameworks (MOFs) have dramatically changed the fundamentals of drug delivery, catalysis, and gas storage as a result of their porous geometry, controlled architecture, and ease of postsynthetic modification. However, the biomedical applications of MOFs still remain a less explored area due to the constraints associated with handling, utilizing, and site-specific delivery. The major drawbacks associated with the synthesis of nano-MOFs are related to the lack of control over particle size and inhomogeneous dispersion during doping. Therefore, a smart strategy for the in situ growth of a nano-metal-organic framework (nMOF) has been devised to incorporate it into a biocompatible polyacrylamide/starch hydrogel (PSH) composite for therapeutic applications. In this study, the post-treatment of zinc metal ion cross-linked PSH with the ligand solution generated the nZIF-8@PAM/starch composites (nZIF-8, nano-zeolitic imidazolate framework-8). The ZIF-8 nanocrystals thus formed have been found to be evenly dispersed throughout the composites. This newly designed nanoarchitectonics of an MOF hydrogel was found to be self-adhesive, which also exhibited improved mechanical strength, a viscoelastic nature, and a pH-responsive behavior. Taking advantage of these properties, it has been utilized as a sustained-release drug delivery platform for a potential photosensitizer drug (Rose Bengal). The drug was initially diffused into the in situ hydrogel, and then the entire scaffold was analyzed for its potential in photodynamic therapy against bacterial strains such as E. coli and B. megaterium. The Rose Bengal loaded nano-MOF hydrogel composite exhibited remarkable IC₅₀ values within the range of 7.37 ± 0.04 and 0.51 ± 0.05 μg/mL for E. coli and B. megaterium. Further, reactive oxygen species (ROS) directed antimicrobial potential was validated using a fluorescence-based assay. This smart in situ nanoarchitectonics hydrogel platform can also serve as a potential biomaterial for topical treatment including wound healing, lesions, and melanoma.

Cross-linked chitosan/lysozyme hydrogels with inherent antibacterial activity and tuneable drug release properties for cutaneous drug administration

Gels with high drug release sustainability and intrinsic antibacterial properties are of high practical potential for cutaneous drug administration, particularly for wound care and skin disease treatment. This study reports the generation and characterization of gels formed by 1,5-pentanedial-mediated crosslinking between chitosan and lysozyme for cutaneous drug delivery. Structures of the gels are characterized by using scanning electron microscopy, X-ray diffractometry and Fourier-transform infrared spectroscopy. An increase in the mass percentage of lysozyme leads to an increase in the swelling ratio and erosion susceptibility of the resulting gels. The drug delivery performance of the gels can be changed simply by manipulating the chitosan/lysozyme mass-to-mass ratio, with an increase in the mass percentage of lysozyme leading to a decline in the encapsulation efficiency and drug release sustainability of the gels. Not only do all gels tested in this study show negligible toxicity in NIH/3T3 fibroblasts, they also demonstrate intrinsic antibacterial effects against both Gram-negative and Gram-positive bacteria, with the magnitude of the effect being positively related to the mass percentage of lysozyme. All these warrant the gels to be further developed as intrinsically antibacterial carriers for cutaneous drug administration.

Hydrogel for the Controlled Delivery of Bioactive Components from Extracts of Eupatorium glutinosum Lam. Leaves

This research reported a hydrogel loaded with the ethanolic and methanolic extracts of Eupatorium glutinosum Lam. The E. glutinosum extracts were characterized by phytochemical screening, Fourier-transform infrared spectroscopy (FTIR), thin-layer chromatography (TLC), and UV/Vis profile identification. This research also evaluated the pharmacological activity of the extracts using antimicrobial, antioxidant, and anti-inflammatory assays prior to polymeric encapsulation. Results indicate that extracts inhibit the Escherichia colii DH5-α (Gram negative) growth; excellent antioxidant activity was evaluated by the ferric reducing power and total antioxidant activity assays, and extracts showed an anti-hemolytic effect. Moreover, the cotton and microcrystalline cellulose hydrogels demonstrate successful encapsulation based on characterization and kinetics studies such as FTIR, extract release, and swelling degree. Moreover, effective antibacterial activity was registered by the loaded hydrogel. The overall results encourage and show that Eupatorium glutinosum-loaded hydrogel may find a wide range of bandage and wound healing applications in the biomedical area.

Antimicrobial Natural Hydrogels in Biomedicine: Properties, Applications, and Challenges-A Concise Review

Natural hydrogels are widely used as biomedical materials in many areas, including drug delivery, tissue scaffolds, and particularly wound dressings, where they can act as an antimicrobial factor lowering the risk of microbial infections, which are serious health problems, especially with respect to wound healing. In this review article, a number of promising strategies in the development of hydrogels with biocidal properties, particularly those originating from natural polymers, are briefly summarized and concisely discussed. Common strategies to design and fabricate hydrogels with intrinsic or stimuli-triggered antibacterial activity are exemplified, and the mechanisms lying behind these properties are also discussed. Finally, practical antibacterial applications are also considered while discussing the current challenges and perspectives.

Probing Pharmaceutical Strategies to Promote the Skin Delivery of Asiatic Acid from Hydrogels: Enhancement Effects of Organic Amine Counterions, Chemical Enhancers, and Microneedle Pretreatment

Asiatic acid (AA) is a pentacyclic triterpene isolated from Centella asiatica, holding great promise for treating a variety of skin disorders. However, the dermal application of AA is limited by its poor solubility and permeability. This study aimed to identify a hydrogel formulation for AA and improve its skin penetration by various penetration enhancement methods. Four kinds of hydrogel bases were selected to prepare the AA hydrogel, in which different organic amines and chemical enhancers were incorporated in combination with microneedle pretreatment. The results showed that AA had good release profiles in the presence of hyaluronic acid as the hydrogel base and organic amines as the counter-ions. Diethylamine and Span 80 could promote drug penetration into the skin, and pretreatment with microneedles could further increase the drug permeability. In conclusion, the optimized hyaluronic acid hydrogel has great potential for use in the topical delivery of AA, and its penetration via the skin can be further improved by different pharmaceutical approaches.

Plant-derived natural products for drug discovery: current approaches and prospects

Nature has abundant source of drugs that need to be identified/purified for use as essential biologics, either individually or in combination in the modern medical field. These drugs are divided into small bio-molecules, plant-made biologics, and a recently introduced third category known as phytopharmaceutical drugs. The development of phytopharmaceutical medicines is based on the ethnopharmacological approach, which relies on the traditional medicine system. The concept of ‘one-disease one-target drug’ is becoming less popular, and the use of plant extracts, fractions, and molecules is the new paradigm that holds promising scope to formulate appropriate drugs. This led to discovering a new concept known as polypharmacology, where natural products from varying sources can engage with multiple human physiology targets. This article summarizes different approaches for phytopharmaceutical drug development and discusses the progress in systems biology and computational tools for identifying drug targets. We review the existing drug delivery methods to facilitate the efficient delivery of drugs to the targets. In addition, we describe different analytical techniques for the authentication and fingerprinting of plant materials. Finally, we highlight the role of biopharming in developing plant-based biologics.

Utilization of FMOC-3F-PHE hydrogel for encapsulation of Zanthoxylum armatum and Cinnamomum camphora oil for enhancing their antibacterial activity

Objective

While essential oils have many applications in medicine, not many studies have been done in the past to address issues of active targeting, enhancing bioavailability and reducing toxicity at higher concentrations. Herein, we used Fmoc-3F-Phe amino acid hydrogels to address such issues by encapsulating essential oils, Zanthoxylum armatum and Cinnamomum camphora, in its system and allowing sustained-release of these oils onto bacterial assays of E. coli ATCC 25922, P. hauseri NBRC 3851, M. luteus KACC 13377, and B. subtilis ATCC 66333 for probing enhanced antibacterial properties of the oils by prolonging its efficacy through controlled-release mechanism.

Results

We found that while Zanthoxylum oil showed no particular difference in enhancing the antibacterial property against the three fast growing bacteria, however profound variation was observed against slow growing bacteria B. subtilis. The hydrogel encapsulated oil was able to retain its antibacterial property for a longer time while directly applied oil could not for this bacteria. Even for highly volatile camphor oil, the oil itself failed to show any antibacterial property with direct use, however the hydrogel encapsulated oil was able to show excellent antibacterial property for B. subtilis and M. luteus through prohibition of sublimation via encapsulation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-06163-4.

Design and Practical Considerations for Active Polymeric Films in Food Packaging

Polymeric films for active food packaging have been playing an important role in food preservation due to favorable properties including high structural flexibility and high property tunability. Over the years, different polymeric active packaging films have been developed. Many of them have found real applications in food production. This article reviews, using a practical perspective, the principles of designing polymeric active packaging films. Different factors to be considered during materials selection and film generation are delineated. Practical considerations for the use of the generated polymeric films in active food packaging are also discussed. It is hoped that this article cannot only present a snapshot of latest advances in the design and optimization of polymeric active food packaging films, but insights into film development to achieve more effective active food packaging can be attained for future research.

Preparation of thyme oil loaded κ-carrageenan-polyethylene glycol hydrogel membranes as wound care system

The present study is aimed at fabricating thyme oil loaded hydrogel membranes composed of κ-carrageenan (CG) and polyethylene glycol (PEG), which can provide moist environment and prevent infections for rapid wound healing. Membranes were prepared with different amounts of PEG via solvent casting technique under ambient conditions. Physicochemical properties of CG-PEG membranes as a function of the PEG content were investigated. The surface morphology of membranes displayed smoother surfaces with increasing PEG content up to 40%. In addition, the interaction of PEG with CG polymer chains was evaluated in terms of Free and bound PEG fraction within the membrane matrix. Furthermore, thyme oil (TO) was added to enhance the antibacterial properties of CG-PEG membranes. These membranes showed >95% antimicrobial activity against both gram-positive and gram-negative bacteria depending on the TO content. Suggesting the great potential of these membranes as a strong candidate for providing an effective antimicrobial nature in human healthcare.

Study of Several Alginate-Based Hydrogels for In Vitro 3D Cell Cultures

Hydrogel, a special system of polymer solutions, can be obtained through the physical/chemical/enzymic crosslinking of polymer chains in a water-based dispersion medium. Different compositions and crosslinking methods endow hydrogel with diverse physicochemical properties. Those hydrogels with suitable physicochemical properties hold manifold functions in biomedical fields, such as cell transplantation, tissue engineering, organ manufacturing, drug releasing and pathological model analysis. In this study, several alginate-based composite hydrogels, including gelatin/alginate (G-A), gelatin/alginate/agarose (G-A-A), fibrinogen/alginate (F-A), fibrinogen/alginate/agarose (F-A-A) and control alginate (A) and alginate/agarose (A-A), were constructed. We researched the advantages and disadvantages of these hydrogels in terms of their microscopic structure (cell living space), water holding capacity, swelling rate, swelling-erosion ratio, mechanical properties and biocompatibility. Briefly, alginate-based hydrogels can be used for three-dimensional (3D) cell culture alone. However, when mixed with other natural polymers in different proportions, a relatively stable network with a good cytocompatibility, mechanical strength and water holding capacity can be formed. The physical and chemical properties of the hydrogels can be adjusted by changing the composition, proportion and cross-linking methods of the polymers. Conclusively, the G-A-A and F-A-A hydrogels are the best hydrogels for the in vitro 3D cell cultures and pathological model construction.

Use of graphene-based materials as carriers of bioactive agents

Graphene possesses a large specific surface area, a high Young's modulus, high fracture strength, high electrical conductivity, and excellent optical performance. It has been widely studied for biomedical use since its first appearance in the literature. This article offers an overview of the latest advances in the design of graphene-based materials for delivery of bioactive agents. To enhance the translation of these carriers into practical use, the toxicity involved is needed to be examined in future research in more detail. In addition, guidelines for standardizing experimental conditions during the evaluation of the performance of graphene-based materials are required to be established so that candidates showing higher practical potential can be more effectively identified for further development. This can streamline the optimization and use of graphene-based materials in delivery applications.

Enhanced Skin Performance of Emulgel vs. Cream as Systems for Topical Delivery of Herbal Actives (Immortelle Extract and Hemp Oil)

Immortelle, as rich source of chlorogenic acid and the phloroglucinol alpha-pyrone compound arzanol, possesses anti-inflammatory and antioxidant properties, affects cell regeneration, and has positive effect on many skin conditions. Hemp oil, characterized by a favorable omega-6 to omega-3 ratio, as well as an abundance of essential fatty acids and vitamin E, participates in immunoregulation and also act as an anti-inflammatory. In the present study, we examined the effect on the skin of creams and emulgels with immortelle extract and hemp oil, by comparing them to placebo samples and a non-treated control. A long-term in vivo study of biophysical skin characteristics, which lasted for 30 days, was conducted on 25 healthy human volunteers. Measured parameters were electrical capacitance of the stratum corneum, trans-epidermal water loss (TEWL), and skin pH and erythema index. Further, a sensory study was carried out in which the panelists had to choose descriptive terms for sensory attributes in questionnaire. The results showed that application of all preparations led to increase of skin hydration and TEWL reduction, while the skin was not irritated, and its normal pH was not disrupted. This study also showed importance of the carrier. Not only were emulgels described by panelists as preparations with better sensory properties, there was a significant difference between the skin hydration effect of emulgel with immortelle extract and hemp oil compared to the placebo emulgel, which was not the case with creams. Such findings indicated enhanced delivery of herbal active substances from emulgel compared to the cream.

Liquid Crystalline Hydrogel with Thermally Induced Reversible Shape Change and Water-Triggered Shape Memory

Liquid crystalline hydrogel (LCH) is synthesized through simultaneous polymerization of hydrophobic and hydrophilic monomers in an oil-in-water emulsion, resulting in phase-separated liquid crystalline network (LCN) embedded in a hydrogel matrix. This material features some properties and functions of both LCN and hydrogel, displaying stable LC phase over repeated hydration and dehydration cycles of the hydrogel matrix. Using mechanically stretched and photocrosslinked LCH, the thermally induced LC-isotropic phase transition in LCN domains can be translated into reversible macroscopic deformation of the LCH. Moreover, the LCH exhibits water absorption-controlled shape memory effect.

Preparation and characterization of 2-hydroxyethyl starch microparticles for co-delivery of multiple bioactive agents

The present study reports the generation of 2-hydroxyethyl starch microparticles for co-delivery and controlled release of multiple agents. The obtained microparticles are characterized by using Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. By using ofloxacin and ketoprofen as drug models, the release sustainability of the microparticles is examined at pH 1.2, 5.4, and 6.8 at 37 °C, with Fickian diffusion being found to be the major mechanism controlling the kinetics of drug release. Upon being loaded with the drug models, the microparticles show high efficiency in acting against Escherichia coli and Bacillus cereus. The results suggest that our reported microparticles warrant further development for applications in which co-administration of multiple bioactive agents is required.

Antibacterial and clusteroluminogenic hypromellose-graft-chitosan-based polyelectrolyte complex films with high functional flexibility for food packaging

Food packaging can extend the shelf life of food products and enhance the safety and quality of the food. This study reports food-grade polyelectrolyte complex films generated via electrostatic interactions between two cellulose-based agents [viz., hypromellose-graft-chitosan, and carmellose sodium]. At optimal conditions, our films show good barrier properties, high transparency, and high efficiency in post-production agent loading. They also demonstrate intrinsic antibacterial effects against both Gram-negative and Gram-positive bacteria. By using frozen chicken breasts as a model, the films enable real-time monitoring of the status of the frozen food due to the property of clusterisation-triggered emission. Along with their negligible toxicity, our films warrant further development as multi-functional films for effective and self-indicating food packaging.

Alginate and alginate composites for biomedical applications

Alginate is an edible heteropolysaccharide that abundantly available in the brown seaweed and the capsule of bacteria such as Azotobacter sp. and Pseudomonas sp. Owing to alginate gel forming capability, it is widely used in food, textile and paper industries; and to a lesser extent in biomedical applications as biomaterial to promote wound healing and tissue regeneration. This is evident from the rising use of alginate-based dressing for heavily exuding wound and their mass availability in the market nowadays. However, alginate also has limitation. When in contact with physiological environment, alginate could gelate into softer structure, consequently limits its potential in the soft tissue regeneration and becomes inappropriate for the usage related to load bearing body parts. To cater this problem, wide range of materials have been added to alginate structure, producing sturdy composite materials. For instance, the incorporation of adhesive peptide and natural polymer or synthetic polymer to alginate moieties creates an improved composite material, which not only possesses better mechanical properties compared to native alginate, but also grants additional healing capability and promote better tissue regeneration. In addition, drug release kinetic and cell viability can be further improved when alginate composite is used as encapsulating agent. In this review, preparation of alginate and alginate composite in various forms (fibre, bead, hydrogel, and 3D-printed matrices) used for biomedical application is described first, followed by the discussion of latest trend related to alginate composite utilization in wound dressing, drug delivery, and tissue engineering applications.

Tailoring Alginate/Chitosan Microparticles Loaded with Chemical and Biological Agents for Agricultural Application and Production of Value-Added Foods

This work reviews the recent development of biopolymer-based delivery systems for agricultural application. Encapsulation into biopolymer microparticles ensures the protection and targeted delivery of active agents while offering controlled release with higher efficiency and environmental safety for ecological and sustainable plant production. Encapsulation of biological agents provides protection and increases its survivability while providing an environment safe for growth. The application of microparticles loaded with chemical and biological agents presents an innovative way to stimulate plant metabolites synthesis. This enhances plants’ defense against pests and pathogens and results in the production of higher quality food (i.e., higher plant metabolites share). Ionic gelation was presented as a sustainable method in developing biopolymeric microparticles based on the next-generation biopolymers alginate and chitosan. Furthermore, this review highlights the advantages and disadvantages of advanced formulations against conventional ones. The significance of plant metabolites stimulation and their importance in functional food production is also pointed out. This review offers guidelines in developing biopolymeric microparticles loaded with chemical and biological agents and guidelines for the application in plant production, underlining its effect on the plant metabolites synthesis.

Development of Hydrogels with Self-Healing Properties for Delivery of Bioactive Agents

Hydrogels are an important class of soft materials that find use in bioactive agent delivery. Because of their high water content, hydrogels generally show poor mechanical strength. Long-term wear and tear in physiological conditions may lead to damage in the hydrogel structure during the delivery of bioactive agents. This results in burst and uncontrolled agent release. One strategy to solve this problem is to incorporate self-healing properties into a hydrogel so that the hydrogel can heal fractures automatically to restore original mechanical properties. The objectives of this article are to revisit the latest advances in the design of self-healing hydrogel-based carriers and to offer insights into further research to translate these carriers from the laboratory to real applications.

Traditional Chinese Medicine and orthopedic biomaterials: Host of opportunities from herbal extracts

The role of Traditional Chinese Medicine (TCM), especially herbs or herbal extracts, in treating diseases has received increasing attention. This review focuses on the use of herbal extracts as signaling molecules and functional materials in the field of orthopedics, biomaterial science and bone tissue engineering strategies. A literature review using both Chinese and English references on herbs and herbal extracts based on TCM theory used in orthopedics and biomaterial science was performed. We discuss the efficacy of herbs, the active extracts from these herbs, the combination of herbal extracts and biomaterials and, finally, the application of herbal extracts to the biomaterials specific to orthopedics. Only a few studies have confirmed the feasibility of applying herbal extracts to biomaterials to improve the role of biomaterials and/or optimize drug delivery and release in orthopedics. In this context, this review reveals a new and promising direction for herbal extracts, where the use of herbal extracts based on TCM systemic treatment, can change the limited modern medicine view of biomaterials as "only for local treatment" when considering its efficacy.

Development and Study of Nanoemulsions and Nanoemulsion-Based Hydrogels for the Encapsulation of Lipophilic Compounds

Biocompatible nanoemulsions and nanoemulsion-based hydrogels were formulated for the encapsulation and delivery of vitamin D₃ and curcumin. The aforementioned systems were structurally studied applying dynamic light scattering (DLS), electron paramagnetic resonance (EPR) spectroscopy and viscometry. In vitro studies were conducted using Franz diffusion cells to investigate the release of the bioactive compounds from the nanocarriers. The cytotoxicity of the nanoemulsions was investigated using the thiazolyl blue tetrazolium bromide (MTT) cell proliferation assay and RPMI 2650 nasal epithelial cells as in vitro model. DLS measurements showed that vitamin D₃ and curcumin addition in the dispersed phase of the nanoemulsions caused an increase in the size of the oil droplets from 78.6 ± 0.2 nm to 83.6 ± 0.3 nm and from 78.6 ± 0.2 nm to 165.6 ± 1.0 nm, respectively. Loaded nanoemulsions, in both cases, were stable for 60 days of storage at 25 °C. EPR spectroscopy revealed participation of vitamin D₃ and curcumin in the surfactants monolayer. In vitro release rates of both lipophilic compounds from the nanoemulsions were comparable to the corresponding ones from the nanoemulsion-based hydrogels. The developed o/w nanoemulsions did not exhibit cytotoxic effect up to the concentration threshold of 1 mg/mL in the cell culture medium.

Surface Engineered Metal-Organic Frameworks (MOFs) Based Novel Hybrid Systems for Effective Wound Healing: A Review of Recent Developments

Wounds present serious medical complications and their healing requires strategies that promote angiogenesis, deposition of collagen as well as re-epithelialization of wounds. Currently used conventional wound healing strategies have become less effective due to various issues associated with them. Thus, novel strategies are needed to be developed for early and effective healing of wounds. Metal-organic frameworks (MOFs), formed by linking of metal ions through organic bridging ligands, are highly tunable hybrid materials and have attracted more considerable scientific attention due to their charming and prominent properties, such as abundant pore structures and multiple functionalities. Surface engineering of MOFs with unique ligands can overcome issues associated with conventional wound healing methods, thus resulting in early and effective wound healing. This review has been undertaken to elaborate wound healing, and the use of surface engineered MOFs for effective and rapid wound healing. The process of wound healing will be discussed followed by a detailed review of recent literature for summarizing applications of surface engineered MOFs for wound healing. MOFs wound healing will be discussed in terms of their use as antibacterial agents, therapeutic delivery vehicles, and dressing systems in wound healing.

miR-23a-3p-abundant small extracellular vesicles released from Gelma/nanoclay hydrogel for cartilage regeneration

Articular cartilage has limited self-regenerative capacity and the therapeutic methods for cartilage defects are still dissatisfactory in clinic. Recent studies showed that exosomes derived from mesenchymal stem cells promoted chondrogenesis by delivering bioactive substances to the recipient cells, indicating exosomes might be a novel method for repairing cartilage defect. Herein, we investigated the role and mechanism of human umbilical cord mesenchymal stem cells derived small extracellular vesicles (hUC-MSCs-sEVs) on cartilage regeneration. In vitro results showed that hUC-MSCs-sEVs promoted the migration, proliferation and differentiation of chondrocytes and human bone marrow mesenchymal stem cells (hBMSCs). MiRNA microarray showed that miR-23a-3p was the most highly expressed among the various miRNAs contained in hUC-MSCs-sEVs. Our data revealed that hUC-MSCs-sEVs promoted cartilage regeneration by transferring miR-23a-3p to suppress the level of PTEN and elevate expression of AKT. Moreover, we fabricated Gelatin methacrylate (Gelma)/nanoclay hydrogel (Gel-nano) for sustained release of sEVs, which was biocompatible and exhibited excellent mechanical property. In vivo results showed that hUC-MSCs-sEVs containing Gelma/nanoclay hydrogel (Gel-nano-sEVs) effectively promoted cartilage regeneration. These results indicated that Gel-nano-sEVs have a promising capacity to stimulate chondrogenesis and heal cartilage defects, and also provided valuable data for understanding the role and mechanism of hUC-MSCs-sEVs in cartilage regeneration.

Development and characterization of a superabsorbing hydrogel film containing Ulmus davidiana var. Japonica root bark and pullulan for skin wound healing

Ulmus davidiana var. japonica (UD) has widely been used in Korean traditional medicine for the treatment of various types of diseases including inflammation and skin wounds. The UD root bark powders possess gelling activity with an excellent capacity for absorbing water. This distinct property could make the UD root bark powders to be a great material for manufacturing a gel film specifically for the healing of large and highly exudating wounds (e.g., pressure sores and diabetic ulcers). In this research, we separated the UD root bark powder into 4 different samples based on their sizes and then tested their water absorption capacity and flowability. Based on these results, 75-150 μm sized and below 75 μm sized samples of UD root bark powders were chosen, and UD gel films were prepared. The UD gel films showed good thermal stability and mechanically improved properties compared with pullulan only gel film with excellent swelling capacity and favorable skin adhesiveness. Further, in the animal studies with the skin wound mice model, the UD gel films exhibited significant therapeutic effects on accelerating wound closure and dermal regeneration. Overall, this study demonstrated the applicability of UD root bark powders for hydrogel wound dressing materials, and the potential of UD gel films to be superior wound dressings to currently available ones.

Drug Release from Polymer Thin Films and Gel Pellets: Insights from Programmed Microplate Electroanalysis

Robotic electroanalysis in 24-well microplates was used to determine Paracetamol (PCT) release from thin films of chitosan and two pH-sensitive synthetic polymers as well as blends of the polymers with each other and with agarose. Square-wave voltammograms were recorded automatically in a potential window of 0.35 V-0.85 V vs. Ag/AgCl/0.1 M KCl and their evaluation revealed time-dependent PCT release into acidic and basic media. Comparison of the release profiles showed that pure chitosan layers released PCT quickly in a single-phase process while liberation from synthetic polymer thin films was slower with a sigmoidal shape at pH 1.2 and pH 8.0 with a maximum release of PCT after approximately 150 and 140 min, respectively. The release profile from thicker agarose films was between those of the thin films. Agarose blended with chitosan or synthetic polymers formed films with biphasic release behavior. Chitosan linearized the initial section of the release profile in chitosan/polymer blends. The automated procedure for release testing offers the advantage of low-cost, labor-effective and error-free data acquisition. The procedure has been validated as a useful microplate assay option for release profile testing.

An electrospun polyurethane scaffold-reinforced zwitterionic hydrogel as a biocompatible device

An electrospun scaffold-reinforced zwitterionic hydrogel achieved both high tensile strength and mechano-induced self-enhancement while maintaining excellent hemocompatibility.

Identification of Molecular Fluorophore as a Component of Carbon Dots able to Induce Gelation in a Fluorescent Multivalent-Metal-Ion-Free Alginate Hydrogel

We introduce a simple approach to fabricate fluorescent multivalent metal ion-free alginate hydrogels, which can be produced using carbon dots accessible from natural sources (citric acid and L-cysteine). Molecular fluorophore 5-oxo-2,3-dihydro-5H-[1,3]-thiazolo[3,2-a] pyridine-3,7-dicarboxylic acid (TPDCA), which is formed during the synthesis of carbon dots, is identified as a key segment for the crosslinking of hydrogels. The crosslinking happens through dynamic complexation of carboxylic acid groups of TPDCA and alginate cages along with sodium ions. The TPDCA derived hydrogels are investigated regarding to their thermal, rheological and optical properties, and found to exhibit characteristic fluorescence of this aggregated molecular fluorophore. Moreover, gradient hydrogels with tunable mechanical and optical properties and controlled release are obtained upon immersion of the hydrogel reactors in solutions of divalent metal ions (Ca2+, Cu2+, and Ni2+) with a higher affinity to alginate.

Fabrication of Composite Hydrogels Based on Soy Protein Isolate and their Controlled Globular Protein Delivery

Soy protein isolate (SPI) protein/polymer composite hydrogels (PPCGs) are fabricated in a urea solution of SPI using acrylic acid as monomer, ammonium persulphate (APS) as initiator, and N,N-methylenebisacrylamide (BIS) and glutaraldehyde (GA) as cross-linking agents. The scanning electron microscope (SEM) results show that SPI/polyacrylic (PAA) composite hydrogels formed network structure. In particular, in the absence of cross-linking agent (GA), the network structure of composite hydrogels is also formed by BIS cross-linking chains of PAA and the hydrophobic interactions between peptides from SPI and chain of PAA. In addition, composite hydrogels have good water absorption and present excellent pH sensitivity. Composite hydrogels adsorb bovine serum albumin (BSA) with higher adsorption capacity. BSA is the control released in pH 7.4 buffers and the accumulative release ratio achieved is 90%. It will be expected that these protein/polymer composite hydrogels could be applied for drug sustained release materials.

Chitosan Hydrogel Delivery System Containing Herbal Compound Functions as a Potential Antineuroinflammatory Agent

Rhein (4,5-dihydroxyanthraquinone-2-carboxylic acid) is an anthraquinone compound mainly isolated from the herbal medicine rhubarb. It possesses a wide spectrum of pharmacological effects. However, the lack of sustained release properties and the poor bioavailability hinder clinical transformation. Hydrogel-based drug delivery system provides an ideal carrier to improve the release control and the therapeutic efficacy of drugs. Herein, we present a chitosan hydrogel for the delivery of rhein. This rhein-chitosan hydrogel (CS-Rh gel) exhibited superior characteristics including mechanical strength, sustained release, and low toxicity. For medical application, the enzyme-linked immunosorbent assay and Western blot analyses indicated that CS-Rh gel significantly suppressed the production of proinflammatory cytokines including TNF-α and IL-1β in lipopolysaccharide-induced BV2 cells. Additionally, CS-Rh gel blocked the neuroinflammation-related mitogen-activated protein kinase (JNK, ERK, and p38)-signaling pathways. Interestingly, these inhibitory effects at 48 h outperformed the pharmacologic actions at 24 h, showing that the CS-Rh gel exerted optimal sustained antineuroinflammation. This study highlights a novel chitosan hydrogel containing rhein used as a potential antineuroinflammatory agent.

Stretchable and Bioadhesive Supramolecular Hydrogels Activated by a One-Stone-Two-Bird Postgelation Functionalization Method

Resembling soft tissues, stretchable hydrogels are promising biomaterials for many biomedical applications due to their excellent mechanical robustness. However, conventional stretchable hydrogels with a synthetic polymer matrix are usually bioinert. The lack of cell and tissue adhesiveness of such hydrogels limits their applications. An easy but reliable postgelation functionalization method is desirable. Herein, we report the fabrication of stretchable supramolecular hydrogels cross-linked by multivalent host-guest interactions. Such hydrogels containing thiourea ( TU) functionalities can be bioactivated with a catechol-modified peptide (Cat-RGD) via thiourea-catechol ( TU-Cat) coupling reaction. This postgelation bioactivation of the otherwise bioinert hydrogels not only conjugates bioactive ligands for cell attachment but also introduces and preserves the catechol structures for tissue adhesion. This straightforward fabrication and one-stone-two-bird bioactivation of the stretchable hydrogels may find broad applications in developing advanced soft biomaterials for tissue repair, wound dressing, and lesion sealing.

Transdermal Delivery of 5-Aminolevulinic Acid by Nanoethosome Gels for Photodynamic Therapy of Hypertrophic Scars

5-Aminolevulinic acid (ALA)-loaded nanoethosome (ALA-ES) gels are successfully prepared to realize a transdermal delivery of ALA, and they provide a feasible approach for the photodynamic therapy (PDT) of hypertrophic scars (HS). Herein, the morphological and physicochemical features indicate that ALA-ES is stable in gel matrix. In vitro transdermal penetration studies suggest ALA-ES gels can overcome the compact dermal barrier and deliver more ALA into human HS tissue. In vivo delivery studies further reveal that ALA-ES gels can penetrate into rabbit HS tissue to facilitate ALA accumulating in hypertrophic scar fibroblast (HSF) and converting into protoporphyrin IX in the cytoplasm. Utilizing transmission electron microscopy, the visual in vivo penetration process indicates ALA-ES penetrate into HS tissue utilizing its deformable membrane, enters HSF by a pinocytotic-like mechanism, and then releases ALA in the cytoplasm. Subsequently, PDT efficacy is assessed using rabbit HS models. The morphological and histological analysis reveal that ALA-ES gels can improve HS by promoting HSF apoptosis, remodelling collagen fibers and increasing MMP3 expression. The results demonstrate that ALA-ES gels are suitable in clinical treatment of HS and make a substantial progress within the field.

Injectable thermosensitive hydrogel systems based on functional PEG/PCL block polymer for local drug delivery

Injectable in situ thermosensitive hydrogels have potential applications in tissue engineering and drug delivery. The hydrogel formulations exist as aqueous solutions at room temperature but rapidly solidify into gels at 37 °C in situ, making them highly suitable for administering drugs in a minimally invasive manner to the target organ(s). The hydrogel formed with nanoparticles assembled with amphiphilic polymer blocks of polyethyleneglycol (PEG) and biodegradable polycaprolactone (PCL) have been tested as platforms for targeted and sustained drug delivery, and have shown encouraging results. In this review, we summarize the influence of the molecular weight, PEG/PCL ratio and functional structure of hydrophobic PCL blocks on the critical gelation temperature, gelling behavior and drug release kinetics of the hydrogels. The current studies on the biomedical applications of thermosensitive PEG/PCL hydrogels have also been discussed.

Antimicrobial hydrogels: promising materials for medical application

The rapid emergence of antibiotic resistance in pathogenic microbes is becoming an imminent global public health problem. Local application of antibiotics might be a solution. In local application, materials need to act as the drug delivery system. The drug delivery system should be biodegradable and prolonged antibacterial effect should be provided to satisfy clinical demand. Hydrogel is a promising material for local antibacterial application. Hydrogel refers to a kind of biomaterial synthesized by a water-soluble natural polymer or a synthesized polymer, which turns into gel according to the change in different signals such as temperature, ionic strength, pH, ultraviolet exposure etc. Because of its high hydrophilicity, unique three-dimensional network, fine biocompatibility and cell adhesion, hydrogel is one of the suitable biomaterials for drug delivery in antimicrobial areas. In this review, studies from the past 5 years were reviewed, and several types of antimicrobial hydrogels according to different ingredients, different preparations, different antimicrobial mechanisms, different antimicrobial agents they contained and different applications, were summarized. The hydrogels loaded with metal nanoparticles as a potential method to solve antibiotic resistance were highlighted. Finally, future prospects of development and application of antimicrobial hydrogels are suggested.