Cryo-Induced Cellulose-Based Nanogel from Elaeis guineensis for Antibiotic Delivery Platform

Cryo-induced hydrogel from cellulose is a new class of biomaterials for drug delivery, cell delivery, bone and skin tissue engineering for cell proliferation and regeneration applications. This research aimed to synthesize cryo-induced hydrogel from cellulose and carboxymethyl cellulose (CMC) produced from empty bunch's cell wall of Elaeis guineensis. First, the experiment was to produce cellulose-rich material using hot-compressed water extraction followed by alkaline delignification and bleaching with H₂O₂. The obtained bleached EFB cellulose was used as the substrate for CMC, and the optimal condition with the highest degree of carboxyl substitution (DS) of 0.75 was achieved when varying NaOH and monochloroacetic acid concentration as well as etherification temperature using fractional factorial design. For cryogelation study, hydrogels were synthesized from cellulose, CMC and beta-cyclodextrin (β-CD) by dissolving cellulose-based matrix in a NaOH/urea system, and the cellulose (CEL) solution was frozen spontaneously at -40 °C followed by high speed mixing to loosen cellulose fibrils. Epichlorohydrin (ECH) and Polyethylene glycol diglycidyl ether (PEGDE) were used as a cross-linker. First, the ratio of cellulose and CMC with different amounts of ECH was investigated, and subsequently the proper ratio was further studied by adding different crosslinkers and matrices, i.e., CMC and β-CD. From the result, the ECH crosslinked CMC-CEL (E-CMC-CEL) gel had the highest swelling properties of 5105% with the average pore size of lyophilized hydrogel of 300 µm. In addition, E-CMC-CEL gel had the highest loading and release capability of tetracycline in buffer solution at pH 7.4 and 3.2. At pH 7.4, tetracycline loading and release properties of E-CMC-CEL gel were 65.85 mg g^-1 dry hydrogel and 46.48 mg g^-1 dry hydrogel (70.6% cumulative release), respectively. However, at pH 3.2, the loading and release capabilities of Tetracycline were moderately lower at 16.25 mg g^-1 dry hydrogel and 5.06 mg g^-1 dry hydrogel, respectively. The findings presented that E-CMC-CEL hydrogel was a suitable material for antibiotic tetracycline drug carrying platform providing successful inhibitory effect on Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, respectively.

Clay-Based Nanocomposite Hydrogels for Biomedical Applications: A Review

In recent decades, new and improved materials have been developed with a significant interest in three-dimensional (3D) scaffolds that can cope with the diverse needs of the expanding biomedical field and promote the required biological response in multiple applications. Due to their biocompatibility, ability to encapsulate and deliver drugs, and capacity to mimic the extracellular matrix (ECM), typical hydrogels have been extensively investigated in the biomedical and biotechnological fields. The major limitations of hydrogels include poor mechanical integrity and limited cell interaction, restricting their broad applicability. To overcome these limitations, an emerging approach, aimed at the generation of hybrid materials with synergistic effects, is focused on incorporating nanoparticles (NPs) within polymeric gels to achieve nanocomposites with tailored functionality and improved properties. This review focuses on the unique contributions of clay nanoparticles, regarding the recent developments of clay-based nanocomposite hydrogels, with an emphasis on biomedical applications.

Fabrication of adhesive hydrogels based on poly (acrylic acid) and modified hyaluronic acid

Hydrogel wound dressings with good flexibility and adhesiveness to resist deformation during wound movement are urgently needed in clinical application. In this work, the hydrogels based on poly (acrylic acid) and N-hydroxysuccinimide grafted hyaluronic acid (PAA/HA_-NHS) with good elasticity and adhesiveness were prepared by chemical cross-linking and hydrogen bonding. The elastic and adhesive properties within the PAA hydrogels could reach a balance by adjusting the concentration of potassium persulfate (KPS) and N, N'-methylenebisacrylamide (MBA). Subsequently, HA_-NHS was incorporated into the PAA hydrogel system. The mechanical test revealed that the elongation at break and interfacial toughness of the PAA/HA_-NHS hydrogels could reach 265.79 ± 21.93% and 52.88 ± 3.51 J/m², respectively. In addition, the hydrogels possess a connected porous network and well water absorption ability (with porosity of 51.90 ± 0.11% and swelling ratio in wet state of 122.17 ± 2.78%). In vitro experiment demonstrates that the PAA/HA_-NHS hydrogels exhibit nontoxic and cell in-adhesive properties. The PAA/HA_-NHS hydrogels could cover the wound spots directly, stretch with the skin movement and gently remove from the wound tissue due to the suitable adhesiveness and poor cell adhesion. In conclusion, the PAA/HA_-NHS hydrogels show great application value in the field of wound dressing.

Fabrication and Characterization of Hydrogels Based on Gelatinised Collagen with Potential Application in Tissue Engineering

Regenerative medicine is increasingly focused on the development of biomaterials that facilitate cell adhesion and proliferation through the use of natural polymers, which have better biocompatibility and biodegradability. In this way, the use of hydrogels has been considered as a potential option for tissue engineering due to their physical and chemical characteristics. However, few studies associate the raw materials properties and processing conditions with the final characteristics of hydrogels, which could condition their use as scaffolds for tissue engineering. In this context, the main objective of this work was the evaluation of type I collagen as raw material for the elaboration of hydrogels. In addition, gelation time, pH and temperature were evaluated as the most influential variables in the hydrogel processing method by rheological (time, strain and frequency sweep tests) and microstructural (Cryo-SEM) measurements. The results indicate that it is possible to obtain collagen hydrogels with adequate rheological and microstructural characteristics by selecting optimal processing conditions. However, further studies are necessary to assess their suitability for cell accommodation and growth.

Periodate-Modified Gum Arabic Cross-linked PVA Hydrogels: A Promising Approach toward Photoprotection and Sustained Delivery of Folic Acid

The chemically oxidized gum arabic was prepared and used as a naturally derived nontoxic and pH-responsive cross-linker to develop smart polyvinyl alcohol (PVA)-based hydrogels for the first time. The formulated hydrogels exhibited high mechanical properties, good porosity, and pH sensitivity, which facilitated their application as promising biomaterials for sustained delivery of folic acid. Further, the synthesized cross-linked PVA hydrogels displayed no cytotoxicity toward the human embryonic kidney cell line and exhibited higher blood compatibility. The hydrolytic degradation study confirmed their biodegradable nature. While the sustained delivery along with photoprotective properties of these hydrogels confirmed their multifunctional characteristics, these results suggest that these hydrogels may act as an efficient photoprotective material and find their application in the field of drug delivery.

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.

Carboxymethyl Cellulose-Xylan Hydrogel: Synthesis, Characterization, and in Vitro Release of Vitamin B12

The current work reports the synthesis of carboxymethyl cellulose (CMC) and xylan-based homopolymerized as well as copolymerized hydrogels using an ethylene glycol diglycidyl ether cross-linker in alkaline medium. The hydrogels are physically characterized by the swelling ratio and gel fraction. The morphological observation of hydrogels reveals the porous structure for the copolymerized gels. The rheological behavior of the gels elaborates that the copolymerized CMC-xylan gel synthesized in a 1:1 molar ratio has superior strain-bearing ability and possesses the shortest gelation temperature and time. Vitamin B₁₂ here is used as the model vitamin to be loaded in the hydrogels and subsequent studies involving the in vitro release in artificial gastric fluid (AGF, pH = 1.2), artificial intestinal fluid (AIF, pH = 6.8), and phosphate-buffered saline (PBS, pH = 7.4). The synthesized gels show a cumulative release of 19-28% in AGF, 80-88% in AIF, and 93-98% in PBS, independently. Further, the highest cumulative release of 93-99% is recorded for all gels when in vitro release is performed in successive buffers, that is, first in AGF, followed by AIF and PBS.

Characterization of CMC–LDH beads and their application in the removal of Cr(vi) from aqueous solution

In this study, CMC–LDH beads were prepared and characterized using SEM, FTIR and TG analysis. The beads were applied for the removal of Cr(vi) from aqueous solution. The effects of adsorbent dosage, initial pH and initial concentration of Cr(vi) solution on Cr(vi) uptake were investigated in detail. Moreover, adsorption isotherms and adsorption kinetic models were employed to analyze the adsorption process, and a preliminary study of the reusability of the adsorbent was performed. The experimental results showed that the CMC–LDH beads could remove Cr(vi) from aqueous solution efficiently. When the initial concentration of the Cr(vi) solution was 100 mg L⁻¹ and the adsorbent dosage was 12 g L⁻¹, the removal efficiency of Cr(vi) reached 96.2%. After the CMC–LDH beads were reused 10 times, the removal efficiency of Cr(vi) still remained at 89.6%.

CMC–LDH beads were prepared, characterized and applied for the removal of heavy metal ions in this study.

Transforming inorganic layered montmorillonite into inorganic–organic hybrid materials for various applications: a brief overview

The effects of various reaction parameters on the synthesis of silylated montmorillonites and several applications of these inorganic–organic layered materials are briefly overviewed in this review.

The states of sulfate groups affect the mechanical and separation properties of carboxymethyl cellulose/chitosan complex membranes

Two states of sulfate groups were dissected to affect mechanical and separation performances of PECMs prepared from CS and CMC.

Drug release profile and reduction in the in vitro burst release from pectin/HEMA hydrogel nanocomposites crosslinked with titania

Hydrogel nanocomposites of pectin, HEMA and titania for Vit-B₁₂ controlled release with reduced initial release burst were prepared. A reduction of up to ca. 60% was observed.

Synthesis of a self-healable and pH responsive hydrogel based on an ionic polymer/clay nanocomposite

This investigation reports the preparation of a pH responsive self-healing nanocomposite hydrogel based on ionic polymer and organically modified montmorillonite (OMMT) clay.

Recent advances in clay mineral-containing nanocomposite hydrogels

Clay mineral-containing nanocomposite hydrogels have been proven to have exceptional composition, properties, and applications, and consequently have attracted a significant amount of research effort over the past few years. The objective of this paper is to summarize and evaluate scientific advances in clay mineral-containing nanocomposite hydrogels in terms of their specific preparation, formation mechanisms, properties, and applications, and to identify the prevailing challenges and future directions in the field. The state-of-the-art of existing technologies and insights into the exfoliation of layered clay minerals, in particular montmorillonite and LAPONITE®, are discussed first. The formation and structural characteristics of polymer/clay nanocomposite hydrogels made from in situ free radical polymerization, supramolecular assembly, and freezing-thawing cycles are then examined. Studies indicate that additional hydrogen bonding, electrostatic interactions, coordination bonds, hydrophobic interaction, and even covalent bonds could occur between the clay mineral nanoplatelets and polymer chains, thereby leading to the formation of unique three-dimensional networks. Accordingly, the hydrogels exhibit exceptional optical and mechanical properties, swelling-deswelling behavior, and stimuli-responsiveness, reflecting the remarkable effects of clay minerals. With the pivotal roles of clay minerals in clay mineral-containing nanocomposite hydrogels, the nanocomposite hydrogels possess great potential as superabsorbents, drug vehicles, tissue scaffolds, wound dressing, and biosensors. Future studies should lay emphasis on the formation mechanisms with in-depth insights into interfacial interactions, the tactical functionalization of clay minerals and polymers for desired properties, and expanding of their applications.

Preparation and characterization of a novel pH-sensitive Salecan-g-poly(acrylic acid) hydrogel for controlled release of doxorubicin

Salecan is a novel water-soluble extracellular β-glucan produced by a salt-tolerant strain Agrobacterium sp. ZX09. Salecan is suitable for the fabrication of hydrogels for biomedical applications due to its excellent physicochemical and biological properties. In this paper, a series of pH-sensitive hydrogels were prepared in aqueous solution by the graft copolymerization of Salecan and acrylic acid (AA) using N,N'-methylene diacrylamide as a crosslinker for controlled drug delivery. The structure and thermal stability of the resulting hydrogels were characterized by FT-IR, XRD and TGA. By SEM analysis, freeze-dried hydrogels displayed an interconnected porous structure with tunable pore size in the range of 23.2-90.3 μm. The swelling behavior of the hydrogels was shown to be highly dependent on the environmental pH, salt type and concentration, as well as the contents of Salecan and BAAm. They are almost unswellable at pH 1.2 and swollen extensively at pH 6.86. Meanwhile, the increase in the content of hydrophilic Salecan could enhance the swelling ratio, whereas the presence of more BAAm reduced the swelling capacity but promoted the water retention to some extent. Rheological tests revealed that storage modulus G' was strongly influenced by the crosslink density of the obtained hydrogel network. Especially, doxorubicin (DOX) as a model anti-cancer drug was very efficiently loaded into the negatively charged hydrogels (up to 69.4 wt%) through electrostatic interactions. More importantly, the release of DOX from this intelligent system exhibited pH-responsive behavior and a sustained release pattern. For SPA2, the cumulative release profile showed a low level of drug release (about 12.3 wt% in 24 h) at pH 7.4, and was significantly accelerated at pH 4.0 (over 40 wt% in 6 h). Cytotoxicity experiments confirmed that all blank hydrogels were non-toxic to A549 cells, while DOX released from the drug-loaded hydrogels remained biologically active and had the capability to kill cancer cells. The preliminary results clearly suggested that the Salecan-g-PAA hydrogels may be promising carriers for controlled drug delivery.

Modified biopolymer-dextrin based crosslinked hydrogels: application in controlled drug delivery

This review describes hydrogels and their classifications along with the synthesis and properties of biopolymer-dextrin based crosslinked hydrogels towards potential application in controlled drug delivery.

Hybrid polypeptide hydrogels produced via native chemical ligation

The NCL crosslinked hybrid hydrogels composed of poly(γ-glutamic acid) and ε-poly-lysine have good biocompatibility and tunable properties.