Synthesis and characterization of new unsaturated esters of Gellan Gum

Recent advances on biomedical applications of gellan gum: A review

Gellan gum (GG) has attracted considerable attention as a versatile biopolymer with numerous potential biological applications, especially in the fields of tissue engineering, wound healing, and cargo delivery. Due to its distinctive characteristics like biocompatibility, biodegradability, nontoxicity, and gel-forming ability, GG is well-suited for these applications. This review focuses on recent research on GG-based hydrogels and biocomposites and their biomedical applications. It discusses the incorporation of GG into hydrogels for controlled drug release, its role in promoting wound healing processes, and its potential in tissue engineering for various tissues including bone, retina, cartilage, vascular, adipose, and cardiac tissue. It provides an in-depth analysis of the latest findings and advancements in these areas, making it a valuable resource for researchers and professionals in these fields.

Mutagenesis enhances gellan gum production by a novel Sphingomonas spp.: upstream optimization, kinetic modeling, and structural and physico-functional evaluation

Gellan gum (GG) has gained tremendous attention owing to its diversified applications. However, its high production and hence market cost are still a bottleneck in its widespread utilization. In the present study, high GG producing mutant of Sphingomonas spp. was developed by random mutagenesis using ethyl methylsulphonate (EMS) for industrial fermentation and identified as Sphingomonas trueperi after 16S rRNA and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) analysis. The fermentation conditions such as pH, temperature, and inoculum ratio were optimized by one factor at a time (OFAT) followed by screening of medium components by the Plackett-Burman statistical design. The most critical nutrients were further optimized by response surface methodology for maximizing GG production. The effect of dissolved oxygen tension in bioreactor on cell growth, substrate consumption, GG production, and batch productivity was elucidated. The highest GG titer (23 ± 2.4 g/L) was attained in optimized medium at 10% inoculum (6.45 ± 0.5 log cfu/mL) under controlled fermentation conditions of pH (7), temperature (30 °C), agitation (300-600 rpm), and aeration (0.5-2.0 SLPM) at 22 ± 2% dissolved oxygen tension in a 10-L bioreactor. Kinetic modeling of optimized batch process revealed that logistic growth model could best explain biomass accumulation, while GG formation and substrate consumption were best explained by Luedeking-Piret and exponential decay model, respectively. Structural and physico-functional features of GG produced by mutant Sphingomonas spp. were characterized by HPLC, FTIR, NMR, DSC, TGA, GPC, SEM, and rheological analysis. The higher productivity (0.51 g/L/h) under optimized fermentation conditions suggests potential consideration of mutant and process for commercial utilization.

Environmentally Stable, Stretchable, Adhesive, and Conductive Organohydrogels with Multiple Dynamic Interactions as High-Performance Strain and Temperature Sensors

Nowadays, with the rapid development of artificial intelligence, conductive hydrogel-based sensors play an increasingly vital role in health monitoring and temperature sensing. However, the perfect integration of the environmental stability and applied performance of the hydrogel has always been a challenging and significant problem. Herein, we report an environmentally tolerant, stretchable, adhesive, self-healing conductive gel through multiple dynamic interactions in the water/glycerol/ionic liquids medium, which can be used as a high-performance strain and temperature sensor. The random copolymer poly(acrylic acid-co-acetoacetoxyethyl methacrylate) interacts with the branched poly(ethylene imine) (PEI) and Zr⁴⁺ ions via the dynamic covalent enamine bonds, coordinations, and electrostatic interactions to improve stretchable (1300%), compressible, fatigue-resistant (1000 cycles at 50% strain), and self-healing performance (95%, 24 h). The combination of water/glycerol/ionic liquids imparts the resulting gel with excellent electrical conductivity, anti-drying, and anti-freezing performance. By means of the above excellent performance, the gel could be used as the flexible strain or pressure sensor with high sensitivity and stability for the detection of the movement, expression, handwriting, pronouncing, and electrocardiogram (ECG) signals in various models. Meanwhile, the resulting gel can be assembled as the temperature sensor to trace the change of temperature accurately and steadily, which has a wide operating window (0 to 100 °C), an ultralow detection limit (0.2 °C), and high sensitivity (2.1% °C^-1). It is believed that the strategy for the multifunction and high-performance gel will blaze a new trail for the smart device in health management, temperature detection, and information transmission under various environmental conditions.

Liposome Loaded Ion/Temperature Dual Responsive Gellan Gum Hydrogel as Potential Nasal-To-Brain Delivery System

Intranasal administration, which can bypass the blood-brain barrier (BBB), is widely recognized as a promising strategy for high-efficiency drug delivery to the brain. Herein, for the purpose of effectively delivering drugs to the brain via intranasal administration, glutathione (GSH)-modified gellan gum (GSH-GG) with ion/temperature dual responsive properties was synthesized and encapsulated on galanthamine hydrobromide (GH)-loaded liposomes (GH-Lipo) for effective GH delivery to the brain (GH-Lipo@GSH-GG). Our results demonstrated that GSH-GG greatly decreased the gelation temperature of GG from 44.0 °C to 22.1 °C without compromising its ion responsiveness. Moreover, GSH-GG had a good protection ability for GH-loaded liposomes without affecting its drug release. Most importantly, the finally obtained GH-Lipo@GSHGG showed acceptable targeted delivery of GH to the brain upon in vivo administration. Therefore, this formulation can be employed as a potential delivery system in nasal-to-brain delivery.

DOE-based synthesis of gellan gum-acrylic acid-based biodegradable hydrogels: screening of significant process variables and in situ field studies

The current study uses the free radical graft copolymerization of acrylic acid as a monomer, N,N-methylene-bis-(acrylamide) as a crosslinker and ammonium persulfate as an initiator to synthesise GG-cl-poly(AA) hydrogels based on gellan gum utilising response surface methodology (RSM). A full factorial design was used to obtain the greatest percent swelling (P_s), and key process variables were determined using the Pareto chart. To make the procedure cost-effective, a multiple regression model employing ANOVA projected a linear model with a maximum percentage swelling of 556 at the lowest concentration of all three studied factors. As a result, the sequential experimental design was successful in obtaining two-fold increases in the percentage swelling in a systematic way. An RSM-based central composite design was used to optimize the percentage swelling of the three most important synthesis parameters: initiator concentration, monomer concentration, and crosslinker concentration. The best process conditions are 7.3 mM L⁻¹ initiator, 44 μM L⁻¹ monomer, and 21.6 mM L⁻¹ crosslinker. The effective synthesis of GG-cl-poly(AA) was validated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, field emission scanning electron microscopy (FE-SEM), and ¹H-nuclear magnetic resonance. The swelling behavior of GG-cl-poly(AA) in water and saline solutions, as well as its water retention capability, was investigated. In comparison to distilled water, the swelling potential of optimized hydrogel was shown to be significantly reduced in saline solutions. The addition of GG-cl-poly(AA) significantly improved the moisture properties of plant growth media (clay, sandy, and clay–soil combination), implying that it has great potential in moisture stress agriculture. GG-cl-poly(AA) biodegradation was studied by soil burial and vermicomposting methods. The composting approach showed 89.95% deterioration after 22 days, while the soil burial method showed 86.71% degradation after 22 days. The synthesized hydrogel may be beneficial for agricultural applications because of its considerable degradation behaviour, strong water retention capacity, low cost, and environmental friendliness.

We use free radical graft copolymerization of acrylic acid as a monomer, N,N-methylene-bis-(acrylamide) as a crosslinker and ammonium persulfate as an initiator to synthesise GG-cl-poly(AA) hydrogels based on gellan gum utilising response surface methodology.

Unsaturated and thiolated derivatives of polysaccharides as functional matrixes for tissue engineering and pharmacology: A review

This review examines investigations into the functionalization of polysaccharides by substituents containing multiple (CC) bonds and thiol (SH) groups that are prone to (co)polymerization in the presence of thermal, redox and photoinitiators or Michael addition reactions. A comparative analysis of the approaches to grafting the mentioned substituents onto the polysaccharide macromolecules was conducted. The use of the modified polysaccharides for the design of the 3D structures, including for the development of the pore bearing matrixes of cells or scaffolds utilized in regenerative medicine was examined. These modified polymers were also examined toward the design of excipient matrixes in pharmacological compositions, including with controllable release of active pharmaceuticals, as wel as of antibacterial and antifungal agents and others. In addition, a few examples of the use of modified derivatives in other areas are given.

Antibacterial and cytotoxic properties from esterified Sterculia gum

Sterculia gums, as karaya and chicha gum, are complex branched and polydisperse heteropolysaccharides which can have their applications extended by improving their characteristics through chemical modifications. The objective of this work was to increase the antimicrobial activity of karaya and chicha gum through chemical modification with maleic anhydride. The incorporation of anhydride in the gum structure was confirmed by the characterization techniques. The derived biopolymers were synthesized and characterized by FTIR, X-ray diffraction, Thermogravimetric analysis and elemental analysis. Antimicrobial activity was evaluated against the Staphylococcus aureus strain (ATCC 25923). Mammalian cytotoxicity assays were also performed by MTT and hemolysis tests. The derivatives showed excellent antibacterial action inhibiting almost 100% of bacterial growth and did not present significant cytotoxicity in mammalian cells. The results showed that the derivatives are promising for biomedical applications aiming the control of infectious diseases caused by S. aureus.

Synthesis and biological evaluation of a bioinspired, tissue-adhesive gellan gum-based hydrogel designed for minimally invasive delivery and retention of chondrogenic cells

A dopamine-modified, bioinspired gellan gum hydrogel (STM-148B) with improved physicochemical and biological characteristics, suitable for minimally invasive cell delivery and retention in the context of cartilage repair, is herein presented. STM-148B's putative game-changing design characteristics include a highly biocompatible, animal-free and chemically defined composition, reproducibility of manufacture and ease of formulation. STM-148B undergoes rapid ionic crossinking by physiologically relevant mono and divalent cations to form stable 3D hydrogels that possess excellent tissue adhesiveness, such that additional fixation aids are rendered superfluous. STM-148B hydrogels maintain viability of mammalian cells and further promote up-regulation of the expression of healthy chondrogenic extracellular matrix markers upon stimulation. STM-148B is currently undergoing pre-clinical safety and efficacy assessment as a medical device for cell delivery and retention focussing on regeneration of hyaline-like cartilage and may represent a valuable addition to the armamentarium of tissue-engineering therapies for treatment of focal cartilage lesions.

New Developments in Medical Applications of Hybrid Hydrogels Containing Natural Polymers

New trends in biomedical applications of the hybrid polymeric hydrogels, obtained by combining natural polymers with synthetic ones, have been reviewed. Homopolysaccharides, heteropolysaccharides, as well as polypeptides, proteins and nucleic acids, are presented from the point of view of their ability to form hydrogels with synthetic polymers, the preparation procedures for polymeric organic hybrid hydrogels, general physico-chemical properties and main biomedical applications (i.e., tissue engineering, wound dressing, drug delivery, etc.).

Sericin-chitosan doped maleate gellan gum nanocomposites for effective cell damage in Mycobacterium tuberculosis

Polysaccharides are increasingly used as biodegradable nanocarrier to selectively deliver therapeutic agents to specific cells. In this study, maleate gellan gum (MA-GG) formed by addition of free radical polymerizable groups, which can be polymerized presence of acetone to design biodegradable three-dimensional networks, were synthesized by esterification. Natural silk sericin was grafted over the maleate gellan gum surface. Maleate Gellan Gum- Silk Sericin-Chitosan (MA-GG-SS-CS) nanocomposites loaded with rifampicin (RF) and pyrazinamide (PZA) to overcome the problems associated with Tuberculosis (TB) therapy. The pH responsive behavior of gellan gum nanocomposites was reposed by silk sericin and exhibited sustained release of 79% RF and 82% PZA for 120 h at pH 4.0. The designed formulations shows higher antimycobacterial activity and rapid delivery of drugs at TB infected macrophage. Nanomaterial effectively aggregated and internalized into the bacterial cells and MH-S cells. Dual drug release inside the cells makes damage in the cell membrane. Green nanocomposites studies pave the way for important use of macromolecules in pulmonary delivery TB drugs.

Tissue engineering with gellan gum

Engineering complex tissues for research and clinical applications relies on high-performance biomaterials that are amenable to biofabrication, maintain mechanical integrity, support specific cell behaviours, and, ultimately, biodegrade. In most cases, complex tissues will need to be fabricated from not one, but many biomaterials, which collectively fulfill these demanding requirements. Gellan gum is an anionic polysaccharide with potential to fill several key roles in engineered tissues, particularly after modification and blending. This review focuses on the present state of research into gellan gum, from its origins, purification and modification, through processing and biofabrication options, to its performance as a cell scaffold for both soft tissue and load bearing applications. Overall, we find gellan gum to be a highly versatile backbone material for tissue engineering research, upon which a broad array of form and functionality can be built.

Recent progress in gellan gum hydrogels provided by functionalization strategies

Gellan gum and its functionalized derivatives present a wide range of applications that open up new possibilities in tissue engineering and regenerative medicine.

Protective effects of reactive functional groups on chondrocytes in photocrosslinkable hydrogel systems

Photocrosslinkable hydrogels are frequently used in cartilage tissue engineering, with crosslinking systems relying on cytotoxic photoinitiators and ultraviolet (UV) light to form permanent hydrogels. These systems are rarely assessed in terms of optimization of photoinitiator or UV dosage, with non-cytotoxic concentrations from literature deemed sufficient. We hypothesized that the number of reactive functional groups present within a hydrogel polymer is highly relevant when crosslinking, affording cytoprotection to chondrocytes by preferentially interacting with the highly reactive radicals that are formed during UV-mediated activation of a photoinitiator. This was tested using two photocrosslinkable hydrogel systems: gelatin methacrylamide (GelMA) and gellan gum methacrylate (GGMA). We further assessed the effects of two different UV dosages on chondrocyte differentiation while subject to a single photoinitiator dosage in the GGMA system. Most notably, we found that a higher ratio of reactive groups to photoinitiator molecules offers cytoprotective effects, and future developments in photocrosslinkable hydrogel technology may involve assessment of such ratios. In contrast, we found there to be no effect of UV on chondrocyte differentiation at the two chosen dosages. Overall the optimization of photocrosslinkable systems is of great value in cartilage tissue engineering and these data provide a groundwork for such concepts to be developed further.

STATEMENT OF SIGNIFICANCE

Photocrosslinkable hydrogels, which use photoinitiators and predominantly ultraviolet light to form stable matrices for cell encapsulation and tissue development, are promising for cartilage tissue engineering. While both photoinitiators and ultraviolet light can damage cells, these systems have generally not been optimized. We propose that the ratio of reactive functional groups within a polymer to photoinitiator molecules is a critical parameter for optimization of photocrosslinkable hydrogels. Using photocrosslinkable gelatin and gellan gum, we found that a higher ratio of reactive groups to photoinitiator molecules protected chondrocytes, but did not affect chondrocyte differentiation. The principle of cytoprotection by functional groups developed in this work will be of great value in optimizing photocrosslinkable hydrogel systems for cartilage and other tissue engineering applications.

Manilkara zapota (Linn.) Seeds: A Potential Source of Natural Gum

Mucilage isolated from seeds of Manilkara zapota (Linn.) P. Royen syn. is a plant growing naturally in the forests of India. This mucilage is yet to be commercially exploited, and characterized as polymer. Various physicochemical methods like particle size analysis, scanning electron microscopy, thermal analysis, gel permeation chromatography, X-ray diffraction spectrometry, zeta potential, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy have been employed to characterize this gum in the present study. Particle size analyses suggest that mucilage has particle size in nanometer. Scanning electron microscopy analysis suggests that the mucilage has irregular particle size. The glass transition temperature of the gum was observed to be 138°C and 136°C by differential scanning calorimetry and differential thermal analysis, respectively. The thermogravimetric analysis suggested that mucilage had good thermal stability. The average molecular weight of mucilage was determined to be 379180, by gel permeation chromatography, while the viscosity of mucilage was observed to be 219.1 cP. The X-ray diffraction spectrometry pattern of the mucilage indicates a completely amorphous structure. Elemental analysis of the gum revealed the contents of carbon, hydrogen, nitrogen, and sulfur to be 80.9 (%), 10.1 (%), 1.58 (%), and 512 (mg/kg), respectively. Mucilage had specific content of calcium, magnesium, potassium, lower concentrations of aluminum, cadmium, cobalt, lead, and nickel. The major functional groups identified from FT-IR spectrum include 3441 cm⁻¹ (–OH), 1660 cm⁻¹ (Alkenyl C–H & C=C Stretch), 1632 cm⁻¹ (–COO–), 1414 cm⁻¹ (–COO–), and 1219 cm⁻¹ (–CH₃CO). Analysis of mucilage by paper chromatography and 1D NMR, indicated the presence of rhamnose, xylose, arabinose, mannose, and fructose.

Aceclofenac-loaded unsaturated esterified alginate/gellan gum microspheres: in vitro and in vivo assessment

Aceclofenac-loaded alginate/gellan gum microspheres for prolonged aceclofenac release were prepared through maleic anhydride-induced unsaturated esterification. The drug entrapment efficiency of these microspheres was found 39.30 ± 1.28% to 98.46 ± 0.40% and their average particle sizes were 270-490 μm. These microspheres were characterized by FTIR, DSC, P-XRD and SEM analysis. The in vitro dissolution indicated prolonged sustained release of aceclofenac over 6h, which also followed the Korsmeyer-Peppas model (R(2)=0.9571-0.9952). The microspheres prepared through 3% (w/v) maleic anhydride-induced esterification exhibited comparatively slower drug-release. Most of the microspheres were followed Fickian diffusion mechanism except the microspheres containing higher gellan gum content, which followed anomalous (non-Fickian) diffusion. The in vivo results showed sustained systemic absorption of aceclofenac in rabbits and excellent anti-inflammatory activity in carrageenan-induced rats after oral administration over prolonged period.

Injectable in situ physically and chemically crosslinkable gellan hydrogel

An injectable, in situ physically and chemically crosslinkable gellan hydrogel is synthesized via gellan thiolation. The thiolation does not alter the gellan's unique 3-D conformation, but leads to a lower phase transition temperature under physiological conditions and stable chemical crosslinking. The synthesis and hydrogels are characterized by (1)H NMR, FT-IR, CD, or rheology measurements. The injectability and the tissue culture cell viability is also tested. The thiolated gellan hydrogel exhibits merits, such as ease for injection, quick gelation, lower gelling temperature, stable structure, and nontoxicity, which make it promising in biomedicine and bioengineering as an injectable hydrogel.

The mechanical properties and cytotoxicity of cell-laden double-network hydrogels based on photocrosslinkable gelatin and gellan gum biomacromolecules

A major goal in the application of hydrogels for tissue engineering scaffolds, especially for load-bearing tissues such as cartilage, is to develop hydrogels with high mechanical strength. In this study, a double-network (DN) strategy was used to engineer strong hydrogels that can encapsulate cells. We improved upon previously studied double-network (DN) hydrogels by using a processing condition compatible with cell survival. The DN hydrogels were created by a two-step photocrosslinking using gellan gum methacrylate (GGMA) for the rigid and brittle first network, and gelatin methacrylamide (GelMA) for the soft and ductile second network. We controlled the degree of methacrylation of each polymer so that they obtain relevant mechanical properties as each network. The DN was formed by photocrosslinking the GGMA, diffusing GelMA into the first network, and photocrosslinking the GelMA to form the second network. The formation of the DN was examined by diffusion tests of the large GelMA molecules into the GGMA network, the resulting enhancement in the mechanical properties, and the difference in mechanical properties between GGMA/GelMA single networks (SN) and DNs. The resulting DN hydrogels exhibited the compressive failure stress of up to 6.9 MPa, which approaches the strength of cartilage. It was found that there is an optimal range of the crosslink density of the second network for high strength of DN hydrogels. DN hydrogels with a higher mass ratio of GelMA to GGMA exhibited higher strength, which shows promise in developing even stronger DN hydrogels in the future. Three dimensional (3D) encapsulation of NIH-3T3 fibroblasts and the following viability test showed the cell-compatibility of the DN formation process. Given the high strength and the ability to encapsulate cells, the DN hydrogels made from photocrosslinkable macromolecules could be useful for the regeneration of load-bearing tissues.

Modified Gellan Gum hydrogels with tunable physical and mechanical properties

Gellan Gum (GG) has been recently proposed for tissue engineering applications. GG hydrogels are produced by physical crosslinking methods induced by temperature variation or by the presence of divalent cations. However, physical crosslinking methods may yield hydrogels that become weaker in physiological conditions due to the exchange of divalent cations by monovalent ones. Hence, this work presents a new class of GG hydrogels crosslinkable by both physical and chemical mechanisms. Methacrylate groups were incorporated in the GG chain, leading to the production of a methacrylated Gellan Gum (MeGG) hydrogel with highly tunable physical and mechanical properties. The chemical modification was confirmed by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR-ATR). The mechanical properties of the developed hydrogel networks, with Young's modulus values between 0.15 and 148 kPa, showed to be tuned by the different crosslinking mechanisms used. The in vitro swelling kinetics and hydrolytic degradation rate were dependent on the crosslinking mechanisms used to form the hydrogels. Three-dimensional (3D) encapsulation of NIH-3T3 fibroblast cells in MeGG networks demonstrated in vitro biocompatibility confirmed by high cell survival. Given the highly tunable mechanical and degradation properties of MeGG, it may be applicable for a wide range of tissue engineering approaches.