A covalently cross-linked hyaluronic acid/bacterial cellulose composite hydrogel for potential biological applications

Effect of the ex situ physical and in situ chemical modification of bacterial nanocellulose on mechanical properties in the context of its potential applications in heart valve design

Bacterial nanocellulose (BNC) is a promising material for heart valve prostheses. However, its low strength properties limit its applicability in cardiovascular surgery. To overcome these limitations, the mechanical properties of BNC can be improved through modifications. The aim of the research was to investigate the extent to which the mechanical properties of BNC can be altered by modifying its structure during its production and after synthesis. The study presents the results of various analyses, including tensile tests, nanoindentation tests, X-ray diffraction (XRD) tests, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy, conducted on BNC chemically modified in situ with hyaluronic acid (BNC/HA) and physically modified ex situ through a dehydration/rehydration process (BNC 25DR, BNC105DR, BNC FDR and BNC/HA 25DR, BNC/HA 105DR, BNC/HA FDR). The results demonstrate that both chemical and physical modifications can effectively shape the mechanical properties of BNC. These modifications induce changes in the crystalline structure, pore size and distribution, and residual stresses of BNC. Results show the effect of the crystalline structure of BNC on its mechanical properties. There is correlation between hardness and Young's modulus and Iα/Iβ index for BNC/HA and between creep rate of BNC/HA, and Young's modulus for BNC vs Iα/Iβ index.

Preparation of environmentally friendly, high strength, adhesion and stability hydrogel based on lignocellulose framework

Hydrogels are extensively utilized in the fields of electronic skin, environmental monitoring, biological dressings due to their excellent flexibility and conductivity. However, traditional hydrogel materials possess drawbacks such as environmental toxicity, low strength, poor stability, and water loss deactivation, which limited its frequent applications. Here, a flexible conductive hydrogel called wood-based DES hydrogel (WDH) with high strength, high adhesion, high stability, and high sensitivity was successfully synthesized by using environmentally friendly lignocellulose as skeleton and deep eutectic solvent as matrix. The strength of WDH prepared from lignocellulose framework is approximately 50 times higher than poly deep eutectic solvent hydrogel, and about 4.5 times higher than that prepared from cellulose skeleton. The WDH exhibits stable adhesion to most common materials and demonstrates exceptional dimensional stability. Its conductivity remains unaffected by water, even after prolonged exposure to air, maintaining a value of 0.0245 S/m. The anisotropy inherent in the system results in three distinct linear sensing intervals for WDH, exhibiting a maximum sensitivity of 5.45. This paper verified the advantages of lignocellulose framework in improving the strength and stability of hydrogels, which provided a new strategy for the development of sensor materials.

Functionalization of bacterial cellulose: Exploring diverse applications and biomedical innovations: A review

The demand for the functionalization of additive materials based on bacterial cellulose (BC) is currently high due to their potential applications across various sectors. The preparation of BC-based additive materials typically involves two approaches: in situ and ex situ. In situ modifications entail the incorporation of additive materials, such as soluble and dispersed substances, which are non-toxic and not essential for bacterial cell growth during the production process. However, these materials can impact the yield and self-assembly of BC. In contrast, ex situ modification occurs subsequent to the formation of BC, where the additive materials are not only adsorbed on the surface but also impregnated into the BC pellicle, while the BC slurry was homogenized with other additive materials and gelling agents to create composite films using the casting method. This review will primarily focus on the in situ and ex situ functionalization of BC then sheds light on the pivotal role of functionalized BC in advancing biomedical technologies, wound healing, tissue engineering, drug delivery, bone regeneration, and biosensors.

Yield stress analysis of cellulose nanocrystals (CNCs) in hyaluronic acid suspensions

Due to their biodegradability features, cellulose nanocrystals (CNCs) and hyaluronic acid (HA) have been simultaneously used in the matrix of hydrogels for biomedical applications, such as corneal transplantation, and skin regeneration. Although rheology of these hydrogels may provide useful information for their applications, little to no attention has been paid to rheological characterization. In this study, we analyzed the rheology of HA-CNC suspensions and more specifically their yielding behavior. Through different rheological experiments, known as stress ramp, shear rate ramp and amplitude sweep; it was observed that HA-CNC gels possessed two yield points. Reproducible magnitudes of yield stress were obtained by optimizing the experimental conditions. The rheo-optics characterizations confirmed that the first and second yield points could be attributed to the bond and cage breakage phenomena. Studying the effect of concentration, the second yield stress increased linearly by CNC concentration, whereas the first yield point manifested a power-law dependence on concentration (exponent of 0.5). This power-law relationship was further justified by the evolution of average distance between the CNC individual particles (d), calculated through SAXS analysis.

Hesperidin guided injured spinal cord neural regeneration with a combination of MWCNT-collagen-hyaluronic acid composite: In-vitro analysis

Restoring the lost bioelectrical signal transmission along with the appropriate microenvironment is one of the major clinical challenges in spinal cord regeneration. In the current research, we developed a polysaccharide-based protein composite Multiwalled Carbon Nanotubes (MWCNTs)/ Collagen (Col)/ Hyaluronic acid (HA) composite with Hesperidin (Hes) natural compound to investigate its combined therapeutic effect along with biocompatibility, antioxidant activity, and electrical conductivity. The multifunctional composites were characterized via FT-IR, XRD, SEM, HR-TEM, BET, C.V, and EIS techniques. The electrical conductivity and modulus of the MWCNT-Col-HA-Hes were 0.06 S/cm and 12.3 kPa, similar to the native spinal cord. The in-vitro Cytotoxicity, cell viability, antioxidant property, and cell migration ability of the prepared composites were investigated with a PC-12 cell line. In-vitro studies revealed that the multifunctional composites show higher cell viability, antioxidant, and cell migration properties than the control cells. Reduction of ROS level indicates that the Hes presence in the composite could reduce the cell stress by protecting it from oxidative damage and promoting cell migration towards the lesion site. The developed multifunctional composite can provide the antioxidant microenvironment with compatibility and mimic the native spinal cord by providing appropriate conductivity and mechanical strength for spinal cord tissue regeneration.

A Covalently Cross-Linked Hyaluronic Acid/Carboxymethyl Cellulose Composite Hydrogel as a Potential Filler for Soft Tissue Augmentation

The use of fillers for soft tissue augmentation is an approach to restore the structure in surgically or traumatically created tissue voids. Hyaluronic acid (HA), is one of the main components of the extracellular matrix, and it is widely employed in the design of materials with features similar to human tissues. HA-based fillers already find extensive use in soft tissue applications, but are burdened with inherent drawbacks, such as poor thermal stability. A well-known strategy to improve the HA properties is to reticulate it with 1,4-Butanediol diglycidyl ether (BDDE). The aim of this work was to improve the design of HA hydrogels as fillers, by developing a crosslinking HA method with carboxymethyl cellulose (CMC) by means of BDDE. CMC is a water soluble cellulose ether, whose insertion into the hydrogel can lead to increased thermal stability. HA/CMC hydrogels at different ratios were prepared, and their rheological properties and thermal stability were investigated. The hydrogel with an HA/CMC ratio of 1/1 resulted in the highest values of viscoelastic moduli before and after thermal treatment. The morphology of the hydrogel was examined via SEM. Biocompatibility response, performed with the Alamar blue assay on fibroblast cells, showed a safety percentage of around 90% until 72 h.

Biocompatible and biodegradable Bletilla striata polysaccharides hydrogels crosslinked by BDDE for wound healing through the regulating of macrophage polarization

Bletilla striata polysaccharide (BSP) is a naturally occurring polysaccharide that demonstrates notable biocompatibility and biodegradability. Additionally, BSP possesses therapeutic attributes, including anti-inflammatory and reparative actions. Herein, we report a novel BSP hydrogel prepared using 1,4-butanediol diglycidyl ether (BDDE) as a cross-linking agent. The hydrogel was synthesized via condensation of the hydroxyl group in the BSP molecule with the epoxy group in BDDE. This technique of preparation preserves BSP's natural properties while avoiding any potentially hazardous or adverse effects that may occur during the chemical alteration. Compared with BSP before crosslinking, BSP hydrogel has distinct advantages, such as a three-dimensional network structure, improved water retention, enhanced swelling capacity, greater thermal stability, and superior mechanical properties. Experiments on in vitro cytotoxicity, hemolysis, and degradation revealed that BSP hydrogel had good biocompatibility and biodegradability. Finally, we evaluated the in vivo wound repair effect of BSP hydrogel, and the results showed that BSP hydrogel had a significant wound-healing effect. Furthermore, the BSP hydrogel promoted the polarization of M1-type macrophages towards the M2-type and reduced the inflammatory response during the wound healing phase. Because of its ease of production, safety, efficacy, and environmental friendliness, BSP hydrogel is considered a highly promising material for wound dressings.

Regulating inflammation and apoptosis: A smart microgel gene delivery system for repairing degenerative nucleus pulposus

The progression of intervertebral disc degeneration (IDD) is attributed to the gradual exacerbation of cellular apoptosis and impaired extracellular matrix (ECM) synthesis, both of which are induced by progressive inflammation. Therefore, it is crucial to address the inflammatory microenvironment and rectify the excessive apoptosis of nucleus pulposus cells (NPCs) to achieve intervertebral disc (IVD) regeneration. In this study, we devised a smart microgel gene delivery system that incorporates functionalized gene nanoparticles (NPs) for the purpose of IVD regeneration. siGrem1 was loaded into the NPs to enhance their antiapoptotic ability and protective effects. Furthermore, the encapsulation of HADA further endows the NPs (referred to as HSGN) with targeted delivery and anti-inflammatory effects, as well as reactive oxygen species (ROS) scavenging capacities. To create an microenvironment-responsive microgel system, phenylboronic acid-functionalized microspheres (referred to as M.S.) were fabricated and dynamically loaded with the HSGN. This microgel system (MHSGN), which is highly biocompatible, enables the sustained release of siGrem1, effectively modulating inflammation, scavenging ROS, and alleviating apoptosis in NPCs. These multifunctional capabilities promote the restoration of metabolic homeostasis within the nucleus pulposus ECM, ultimately leading to delayed IDD.

Cellulose Dissolution, Modification, and the Derived Hydrogel: A Review

The cellulose-based hydrogel has occupied a pivotal position in almost all walks of life. However, the native cellulose can not be directly used for preparing hydrogel due to the complex non-covalent interactions. Some literature has discussed the dissolution and modification of cellulose but has yet to address the influence of the pretreatment on the as-prepared hydrogels. Firstly, the "touching" of cellulose by derived and non-derived solvents was introduced, namely, the dissolution of cellulose. Secondly, the "conversion" of functional groups on the cellulose surface by special routes, which is the modification of cellulose. The above-mentioned two parts were intended to explain the changes in physicochemical properties of cellulose by these routes and their influences on the subsequent hydrogel preparation. Finally, the "reinforcement" of cellulose-based hydrogels by physical and chemical techniques was summarized, viz., improving the mechanical properties of cellulose-based hydrogels and the changes in the multi-level structure of the interior of cellulose-based hydrogels.

Bacterial cellulose: Nature's greener tool for industries

Bacteria are considered mini chemical factories that help us in providing a wide range of products for various purposes. These days, bacterial cellulose (BC) is getting attention by researchers due to its quality, eco-friendly nature, and excellent physical-mechanical qualities. It is being used in the fabrication of nanocomposites. Its nanocomposites can be used in various industries, including medicine, food, leather, textiles, environment, electronics, and cosmetics. This area of research is emerging and still in its infancy stage, as new applications are still coming up. Most of the work on BC has been done during the last two decades and serious inputs are required in this direction in order to make the production process commercially viable and ultimately the application part. Biowastes, such as fruits and vegetables wastes, can be used as a cost-effective medium to minimize the cost for large-scale production of BC-based nanocomposites thus will valorize the biowaste material into a valuable product. Using biowaste as media will also aid in better waste management along with reduction in detrimental environmental effects. This review will help the readers to understand the potential applications of BC and its nanocomposites as well as their vital role in our daily lives.

Cell-Laden 3D Hydrogels of Type I Collagen Incorporating Bacterial Nanocellulose Fibers

There is a growing interest in developing natural hydrogel-based scaffolds to culture cells in a three-dimensional (3D) millieu that better mimics the in vivo cells' microenvironment. A promising approach is to use hydrogels from animal tissues, such as decellularized extracellular matrices; however, they usually exhibit suboptimal mechanical properties compared to native tissue and their composition with hundreds of different protein complicates to elucidate which stimulus triggers cell's responses. As simpler scaffolds, type I collagen hydrogels are used to study cell behavior in mechanobiology even though they are also softer than native tissues. In this work, type I collagen is mixed with bacterial nanocellulose fibers (BCf) to develop reinforced scaffolds with mechanical properties suitable for 3D cell culture. BCf were produced from blended pellicles biosynthesized from Komagataeibacter xylinus. Then, BCf were mixed with concentrated collagen from rat-tail tendons to form composite hydrogels. Confocal laser scanning microscopy and scanning electron microscopy images confirmed the homogeneous macro- and microdistribution of both natural polymers. Porosity analysis confirmed that BCf do not disrupt the scaffold structure. Tensile strength and rheology measurements demonstrated the reinforcement action of BCf (43% increased stiffness) compared to the collagen hydrogel while maintaining the same viscoelastic response. Additionally, this reinforcement of collagen hydrogels with BCf offers the possibility to mix cells before gelation and then proceed to the culture of the 3D cell scaffolds. We obtained scaffolds with human bone marrow-derived mesenchymal stromal cells or human fibroblasts within the composite hydrogels, allowing a homogeneous 3D viable culture for at least 7 days. A smaller surface shrinkage in the reinforced hydrogels compared to type I collagen hydrogels confirmed the strengthening of the composite hydrogels. These collagen hydrogels reinforced with BCf might emerge as a promising platform for 3D in vitro organ modeling, tissue-engineering applications, and suitable to conduct fundamental mechanobiology studies.

Recent advances in bacterial cellulose-based antibacterial composites for infected wound therapy

Wound infection arising from pathogenic bacteria brought serious trouble to the patient and medical system. Among various wound dressings that are effective in killing pathogenic bacteria, antimicrobial composites based on bacterial cellulose (BC) are becoming the most popular materials due to their success in eliminating pathogenic bacteria, preventing wound infection, and promoting wound healing. However, as an extracellular natural polymer, BC is not inherently antimicrobial, which means that it must be combined with other antimicrobials to be effective against pathogens. BC has many advantages over other polymers, including nano-structure, significant moisture retention, non-adhesion to the wound surface, which has made it superior to other biopolymers. This review introduces the recent advances in BC-based composites for the treatment of wound infection, including the classification and preparation methods of composites, the mechanism of wound treatment, and commercial application. Moreover, their wound therapy applications include hydrogel dressing, surgical sutures, wound healing bandages, and patches are summarized in detail. Finally, the challenges and future prospects of BC-based antibacterial composites for the treatment of infected wounds are discussed.

In vitro activity of hyaluronic acid and human serum on periodontal biofilm and periodontal ligament fibroblasts

OBJECTIVES

A beneficial effect of cross-linked hyaluronic acid (cHA) on periodontal wound healing and regeneration has recently been demonstrated. The present in vitro study was designed to obtain deeper knowledge on the effect of cHA when applied in the gingival sulcus (serum-rich environment) during non-surgical periodontal therapy.

MATERIALS AND METHODS

The influence of cHA, human serum (HS), and cHA/HS on (i) a 12-species biofilm formation, (ii) the adhesion of periodontal ligament fibroblasts (PDLF) to dentine surface, (iii) the expression and secretion of interleukin-8, and (iv) the expression of receptors of HA in PDLF and gingival fibroblasts (GF) were evaluated.

RESULTS

At 4 h of biofilm formation, cHA and HS in combination (cHA/HS) slightly decreased the colony-forming unit counts in biofilm whereas the metabolic activity of biofilm was reduced in all test groups (cHA, HS, cHA/HS) vs. control. At 24 h, the quantity of biofilm was reduced in all test groups vs. untreated control. The test substances did not affect adhesion of PDLF to dentin. HS increased the expression of IL-8 by PDLF and GF which was partially downregulated by cHA. HS and/or cHA promoted the expression of the HA receptor RHAMM in GF but not in PDLF.

CONCLUSIONS

In summary, the present data indicate that serum neither negatively affect the activity of cHA against periodontal biofilm nor had any unwanted influence on the activity of PDLF.

CLINICAL RELEVANCE

These findings lend additional support for the positive effects of cHA on cells involved in periodontal wound healing, thus pointing to its potential use in non-surgical periodontal therapy.

Synthesis of epoxidized natural rubber grafted with hyaluronic acid for the development of biomaterials

Natural Rubber (NR), extracted from Hevea brasiliensis rubber trees, is a biocompatible biopolymer with properties that support in the tissue repair process. However, its biomedical applications are limited due to the presence of allergenic proteins, hydrophobicity, and unsaturated bonds. To overcome these limitations and contribute to the development of new biomaterials, this study aims to deproteinize, epoxidize, and subject NR to copolymerization by grafting with hyaluronic acid (HA), which is widely recognized for its bioactive properties in the medical field. The deproteinization, epoxidation, and graft copolymerization through the esterification reaction were confirmed by Fourier Transform Infrared Spectroscopy and Hydrogen Nuclear Magnetic Resonance Spectroscopy analysis. Thermogravimetry and Differential Scanning Calorimetry demonstrated that the grafted sample exhibited a lower degradation rate and a higher glass transition temperature, indicating strong intermolecular interactions. Moreover, contact angle measurement revealed that the grafted NR exhibited a high hydrophilic character. The results obtained suggest the formation of a novel material with great potential for application in biomaterials involved in tissue repair processes.

A Microbial Co-Culturing System for Producing Cellulose-Hyaluronic Acid Composites

In this study, a co-culture system combining bacterial cellulose (BC) producers and hyaluronic acid (HA) producers was developed for four different combinations. AAB of the genus Komagataeibacter sp. and LAB of the Lactocaseibacillus genus were used to produce BC and HA, respectively. Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction were used to investigate changes in BC-HA composites chemical and morphological structure. Water absorption, uptake, and antibacterial properties were also tested. Outcomes highlighted a higher bacterial cellulose yield and the incorporation of hyaluronic acid into the composite. The presence of hyaluronic acid increased fiber dimension-nearly doubled for some combinations-which led to a decreased crystallinity of the composites. Different results were observed based on the BC producer and HA producer combination. However, water holding capacity (WHC) in all the samples improved with the presence of HA, while water uptake worsened. A thymol-enriched BC-HA composite showed high antibacterial activity against Escherichia coli DSM 30083^T and Staphylococcus aureus DSM 20231^T. Results could contribute to opening new applications in the cosmetics or pharmaceutical fields.

Bacterial cellulose-based hydrogel with antibacterial activity and vascularization for wound healing

Skin wounds need an appropriate wound dressing to help prevent bacterial infection and accelerate wound closure. Bacterial cellulose (BC) with a three-dimensional (3D) network structure is an important commercial dressing. However, how to effectively load antibacterial agents and balance the antibacterial activity is a lingering issue. Herein, this study aims to develop a functional BC hydrogel containing silver-loaded zeolitic imidazolate framework-8 (ZIF-8) antibacterial agent. The tensile strength of the prepared biopolymer dressing is >1 MPa, the swelling property is over 3000 %, the temperature can reach 50 °C in 5 min with near-infrared (NIR) and the release of Ag⁺ and Zn²⁺ is stable. In vitro investigation shows that the hydrogel displays enhanced antibacterial activity, and the bacteria survival ratios are only 0.85 % and 0.39 % against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In vitro cell experiments present that BC/polydopamine/ZIF-8/Ag (BC/PDA/ZIF-8/Ag) shows satisfactory biocompatibility and promising angiogenic ability. In vivo study, the full-thickness skin defect on rats demonstrates remarkably wound healing ability and accelerated skin re-epithelialization. This work presents a competitive functional dressing with effective antibacterial properties and accelerative angiogenesis activities for wound repair.

Tissue engineering modalities in skeletal muscles: focus on angiogenesis and immunomodulation properties

Muscular diseases and injuries are challenging issues in human medicine, resulting in physical disability. The advent of tissue engineering approaches has paved the way for the restoration and regeneration of injured muscle tissues along with available conventional therapies. Despite recent advances in the fabrication, synthesis, and application of hydrogels in terms of muscle tissue, there is a long way to find appropriate hydrogel types in patients with congenital and/or acquired musculoskeletal injuries. Regarding specific muscular tissue microenvironments, the applied hydrogels should provide a suitable platform for the activation of endogenous reparative mechanisms and concurrently deliver transplanting cells and therapeutics into the injured sites. Here, we aimed to highlight recent advances in muscle tissue engineering with a focus on recent strategies related to the regulation of vascularization and immune system response at the site of injury.

Cytophilic Agarose-Epoxide-Amine Cryogels Engineered with Granulated Microstructures

Inherent cytophobicity of agarose limits its direct use for the growth of anchorage-dependent cells. Here, we report a simple strategy allowing the development of agarose-based hydrogels entailed with both cytophilicity and microstructured morphology. Through the reaction of water-soluble 1,4-butanediol diglycidyl ether (BDDE) with trifunctional polyetheramine Jeffamine T403 in agarose solution followed by cryogelation of the mixtures, a series of macroporous agarose-epoxide-amine cryogels were prepared readily. Results from fluorescent labeling and energy-dispersive X-ray elemental mapping showed the formation of granulated microstructures in the cryogels. Such features closely correlated to the phase separation of BDDE-T403 polymers within the agarose matrix. Cytophilicity of the microstructured cryogels due to the integrated amine moieties was demonstrated through the adhesion of fibroblasts. Functional enrichment of the cryogels was further highlighted by leveraging the granulates as micro-reservoirs for polyphenol proanthocyanidin to enable antioxidation and protection of fibroblasts from H₂O₂-induced cytotoxic effect in vitro.

Preparation and Evaluation of Bacterial Nanocellulose/Hyaluronic Acid Composite Artificial Cornea for Application of Corneal Transplantation

The treatment for corneal damage requires donor corneal transplantation, but there is a serious scarcity of donor corneas worldwide. In this study, we aimed to design a new artificial cornea with good cytocompatibility, excellent optical properties and suture resistance, and great moisturizing properties. A new bacterial nanocellulose (BNC) membrane with anisotropic mechanical properties and high light transmission was produced in a horizontal rotary drum reactor. However, as a potential material for artificial keratoplasty, the transparency and mechanical properties of the new BNC membrane were not satisfactory. Thus, hyaluronic acid (HA) was introduced in the BNC to synthesize the BNC/HA composite membrane by using 1,4-butanediol diglycidyl ether (BDDE) as the chemical cross-linking agent. The micro-morphology, light transmittance, mechanical properties, water content, moisture retention ability, and cytocompatibility of the composite membranes were further evaluated. HA was fixed in the BNC network by the ether bond, and the composite membrane was found to have excellent light transmittance (up to 95.96%). The composite membrane showed excellent mechanical properties, for instance, its tensile strength exceeded the human normal intraocular pressure (IOP) (1.33-2.80 kPa), the maximum burst pressure was about 130 kPa, 46-97 times that of the normal IOP, and its suture force was close to that of the human amniotic membrane (0.1 N). Based on the three-dimensional network scaffold of BNC and the high water absorption characteristics of HA, the artificial cornea had high water content and high moisture retention ability. The rabbit corneal stromal cells cultured in vitro showed that the artificial cornea substitute had excellent cytocompatibility. BDDE is the most frequently used cross-linker in most HA products in the current cosmetic medicine industry owing to its long-term safety records for over 15 years. Therefore, the BNC/HA composite hydrogel cross-linked with BDDE has great potential in artificial keratoplasty or ocular surface repair.

Cell-Derived Vesicles with Increased Stability and On-Demand Functionality by Equipping Their Membrane with a Cross-Linkable Copolymer

Cell-derived vesicles retain the cytoplasm and much of the native cell membrane composition. Therefore, they are attractive for investigations of membrane biophysics, drug delivery systems, and complex molecular factories. However, their fragility and aggregation limit their applications. Here, the mechanical properties and stability of giant plasma membrane vesicles (GPMVs) are enhanced by decorating them with a specifically designed diblock copolymer, cholesteryl-poly[2-aminoethyl methacrylate-b-poly(ethylene glycol) methyl ether acrylate]. When cross-linked, this polymer brush enhances the stability of the GPMVs. Furthermore, the pH-responsiveness of the copolymer layer allows for a controlled cargo loading/release, which may enable various bioapplications. Importantly, the cross-linked-copolymer GPMVs are not cytotoxic and preserve in vitro membrane integrity and functionality. This effective strategy to equip the cell-derived vesicles with stimuli-responsive cross-linkable copolymers is expected to open a new route to the stabilization of natural membrane systems and overcome barriers to biomedical applications.

Exploitation of cantaloupe peels for bacterial cellulose production and functionalization with green synthesized Copper oxide nanoparticles for diverse biological applications

The promising features of most bacterial celluloses (BC) promote the continuous mining for a cost-effective production approach toward wide and sustainable applications. Herein, cantaloupe peels (CP) were successfully implemented for sustainable BC production. Results indicated that the enzymatically hydrolyzed CP supported the maximum BC production of approximately 3.49 g/L when used as a sole fermentation media. The produced BC was fabricated with polyvinyl alcohol (PVA) and chitosan (Ch), and loaded with green synthesized copper oxide nanoparticles (CuO-NPs) to improve its biological activity. The novel composite showed an antimicrobial activity against several human pathogens such as Staphylococcus aureus, Streptococcus mutans, Salmonella typhimurium, Escherichia coli, and Pseudomonas fluorescens. Furthermore, the new composite revealed a significant in vitro anticancer activity against colon (Caco-2), hepatocellular (HepG-2), and breast (MDA) cancer cells, with low IC₅₀ of 0.48, 0.27, and 0.33 mg/mL for the three cell lines, respectively. On the other hand, the new composite was remarkably safe for human skin fibroblast (HSF) with IC₅₀ of 1.08 mg/mL. Interestingly, the composite membranes exhibited lethal effects against all stages of larval instar and pupal stage compared with the control. In this study, we first report the diverse potential applications of BC/PVA/Ch/CuO-NPs composites based on green synthesized CuO-NPs and sustainably produced BC membrane.

Hydrogel-Crosslinked Microneedles Based on Microwave-Assisted Drying Method

We present a method and several applications for the synthesis of hydrogel-crosslinked microneedle arrays utilizing microwave-assisted drying, ensuring a significant reduction in reaction preparation time while maintaining quality. We demonstrate the feasibility of drying hydrogels using microwaves and thus extend to crosslinked microneedle fabrication. Crosslinking was performed using 1,4-butanediol diglycidyl ether (BDDE) as a crosslinking agent. Infrared spectra of the microneedle arrays were measured with attenuated total reflection-Fourier transform infrared (ATR-FTIR). The surface morphology of the microneedle arrays was observed with scanning electron microscopy (SEM). The microneedle arrays were evaluated in terms of mechanical strength, swelling kinetics, rheological properties, degradation rate, and glucose iontophoresis. The results show that this method can shorten the reaction preparation time by 5 hours, and the prepared crosslinked microneedle array has better crosslinking efficiency, swelling effect, and greater mechanical strength than traditional methods.

A decellularized spinal cord extracellular matrix-gel/GelMA hydrogel three-dimensional composite scaffold promotes recovery from spinal cord injury via synergism with human menstrual blood-derived stem cells

Spinal cord injury (SCI), as a serious disabling disease, is still haunted by lacking of effective treatments. We previously found that transplantation of menstrual blood-derived mesenchymal stem cells (MenSCs) promoted axon regeneration in rats with SCI, while the abominable microenvironment after the SCI inhibited the survival of stem cells after transplantation. Biomaterials can support the activity of stem cells and accelerate the functional reconstruction of the injured spinal cord. In this study, we constructed a novel composite scaffold consisting of the decellularized spinal cord extracellular matrix-gel (DSCG) and the GelMA hydrogel, which harbored high water retention, wettability, degradability and soft mechanical property. In vitro, the DSCG/GelMA composite scaffold provided a dual bionic microenvironment with optimized bioactive components and favorable microstructures for the adhesion, proliferation and differentiation of MenSCs. After that, we prepared MenSC-encapsulated DSCG/GelMA composite scaffolds to bridge the 2 mm gap in rats with completely transected SCI. The in vivo results showed that the combined use of the DSCG/GelMA composite scaffold with MenSCs improved the motor function, reduced the inflammatory response, promoted neuronal differentiation, and inhibited the proliferation of reactive astrocytes after spinal cord injury. Altogether, our study provided a promising novel therapeutic option of using bioactive materials synergistic with stem cells for the treatment of SCI.

Microorganism-derived biological macromolecules for tissue engineering

According to literature, certain microorganism productions mediate biological effects. However, their beneficial characteristics remain unclear. Nowadays, scientists concentrate on obtaining natural materials from live creatures as new sources to produce innovative smart biomaterials for increasing tissue reconstruction in tissue engineering and regenerative medicine. The present review aims to introduce microorganism-derived biological macromolecules, such as pullulan, alginate, dextran, curdlan, and hyaluronic acid, and their available sources for tissue engineering. Growing evidence indicates that these materials can be used as biological material in scaffolds to enhance regeneration in damaged tissues and contribute to cosmetic and dermatological applications. These natural-based materials are attractive in pharmaceutical, regenerative medicine, and biomedical applications. This study provides a detailed overview of natural-based biomaterials, their chemical and physical properties, and new directions for future research and therapeutic applications.

Novel Retro-Inverso Peptide Antibiotic Efficiently Released by a Responsive Hydrogel-Based System

Topical antimicrobial treatments are often ineffective on recalcitrant and resistant skin infections. This necessitates the design of antimicrobials that are less susceptible to resistance mechanisms, as well as the development of appropriate delivery systems. These two issues represent a great challenge for researchers in pharmaceutical and drug discovery fields. Here, we defined the therapeutic properties of a novel peptidomimetic inspired by an antimicrobial sequence encrypted in human apolipoprotein B. The peptidomimetic was found to exhibit antimicrobial and anti-biofilm properties at concentration values ranging from 2.5 to 20 µmol L⁻¹, to be biocompatible toward human skin cell lines, and to protect human keratinocytes from bacterial infections being able to induce a reduction of bacterial units by two or even four orders of magnitude with respect to untreated samples. Based on these promising results, a hyaluronic-acid-based hydrogel was devised to encapsulate and to specifically deliver the selected antimicrobial agent to the site of infection. The developed hydrogel-based system represents a promising, effective therapeutic option by combining the mechanical properties of the hyaluronic acid polymer with the anti-infective activity of the antimicrobial peptidomimetic, thus opening novel perspectives in the treatment of skin infections.

Bacterial cellulose as a potential biopolymer in biomedical applications: a state-of-the-art review

Throughout history, natural biomaterials have benefited society. Nevertheless, in recent years, tailoring natural materials for diverse biomedical applications accompanied with sustainability has become the focus. With the progress in the field of materials science, novel approaches for the production, processing, and functionalization of biomaterials to obtain specific architectures have become achievable. This review highlights an immensely adaptable natural biomaterial, bacterial cellulose (BC). BC is an emerging sustainable biopolymer with immense potential in the biomedical field due to its unique physical properties such as flexibility, high porosity, good water holding capacity, and small size; chemical properties such as high crystallinity, foldability, high purity, high polymerization degree, and easy modification; and biological characteristics such as biodegradability, biocompatibility, excellent biological affinity, and non-biotoxicity. The structure of BC consists of glucose monomer units polymerized via cellulose synthase in β-1-4 glucan chains, creating BC nano fibrillar bundles with a uniaxial orientation. BC-based composites have been extensively investigated for diverse biomedical applications due to their similarity to the extracellular matrix structure. The recent progress in nanotechnology allows the further modification of BC, producing novel BC-based biomaterials for various applications. In this review, we strengthen the existing knowledge on the production of BC and BC composites and their unique properties, and highlight the most recent advances, focusing mainly on the delivery of active pharmaceutical compounds, tissue engineering, and wound healing. Further, we endeavor to present the challenges and prospects for BC-associated composites for their application in the biomedical field.

A comparison study of hyaluronic acid hydrogel exquisite micropatterns with photolithography and light-cured inkjet printing methods

The microstructure design of hydrogel materials offers a broad range of practical applications and is extensively used in flexible sensors, polymer microneedles, microfluidic chips, and other biomedical engineering fields. Among the bio-sourced hydrogels, oligomeric hyaluronic acid (HA) possesses wound healing, anti-tumor, and angiogenesis properties. However, micropatterning soft hydrogels, such as HA-relative hydrogels containing 90% water by weight, continue to pose difficulties for both high precision and micro-scale lithography. The purpose of this study was to compare the photolithography and light-cured inkjet printing methods of methacryloyl HA hydrogel (HAMA-gel) to those for synthetic light-curable polymer resins. Photolithography and light-cured inkjet printing methods with designed scale, high resolution, and little processing times were used to effectively prepare micropatterns of HAMA-gel. The well-shaped micropatterns consisted of parallel channels in tens of micrometers and strip/grid lines in the hundreds of micrometers. Human vein endothelial cells cultured on the material’s surface demonstrated that HAMA-gel had good biocompatibility. The width of the flow channel (10 and 20 µm) was regulated on the surface of the microstructure to allow for simultaneous control of cell growth along the flow channel and groove directions.

Preparation and applications of chitosan and cellulose composite materials

Chitosan is a natural fiber, chemically cellulose-like biopolymer, which is processed from chitin. Its use as a natural polymer is getting more attention because it is non-toxic, renewable, and biocompatible. However, its poor mechanical and thermal strength, particle size, and surface area restrict its industrial use. Consequently, to improve these properties, cellulose and/or inorganic nanoparticles have been used. This review discusses the recent progress of chitosan and cellulose composite materials, their preparation, and their applications in different industrial sectors. It also discusses the modification of chitosan and cellulose composite materials to allow their use on a large scale. Finally, the recent development of chitosan composite materials for drug delivery, food packaging, protective coatings, and wastewater treatment are discussed. The challenges and perspectives for future research are also considered. This review suggests that chitosan and cellulose nano-composite are promising, low-cost products for environmental remediation involving a simple production process.

Development of di(2‐ethylhexyl) phthalate‐containing thioglycolic acid immobilized chitosan mucoadhesive gel as an alternative hormone therapy for menopausal syndrome

Menopausal syndrome includes the symptoms that most women experience owing to hormone changes after menopause. Although hormone replacement therapy is a common treatment for menopausal syndrome, there are still many side effects and challenges hindering research. In this study, thioglycolic acid (TGA)‐immobilized chitosan mucoadhesive gel was synthesized by a new method of low concentration of 1,4‐butanediol diglycidyl ether (BDDE) would encapsulate di(2‐ethylhexyl) phthalate (DEHP) as an alternative hormone replacement therapy for menopausal syndrome. The efficacies of the DEHP‐containing TGA‐chitosan gel (CT‐D) were confirmed and evaluated by materials characterization and in vitro study. Results showed that CT‐D was not cytotoxic and had better mucoadhesive ability than chitosan. The animal model was constructed 1 month after bilateral ovariectomy in SD rats. CT‐D was administered intravaginally every 3 days. Bodyweight, wet weight of the uterus and vagina, vaginal smears, histology, blood element analysis, and serological analysis was used to assess the ability of the material to relieve menopausal syndrome. The results indicated that the combination of the sustained release of DEHP and mucoadhesive TGA‐immobilized chitosan allows the developed CT‐D to relieve the menopausal syndrome through low concentrations of DEHP, which falls in the safety level of the tolerable daily intake of DEHP.

An extremely tough and ionic conductive natural-polymer-based double network hydrogel

Hydrogels are widely used in fields such as drug delivery, tissue regeneration, soft robotics and flexible smart electronic devices, yet their application is often limited by unsatisfactory mechanical behaviors. Among the various improvement strategies, double network (DN) hydrogels from synthetic polymers demonstrated impressive mechanical properties, while those from natural polymers were usually inferior. Here, a novel DN hydrogel composed fully of natural polymers exhibiting remarkable mechanical properties and conductivity is prepared by simply soaking a virgin gellan gum/gelatin composite hydrogel in a mixed solution of Na₂SO₄ and (NH₄)₂SO₄. This hydrogel exhibits a tunable Young's modulus (0.08 to 42.6 MPa), good fracture stress (0.05 to 7.5 MPa), good fracture stretch (1.4 to 7.1), high fracture toughness (up to 27.7 kJ m^-2), and high ionic conductivity (up to 11.4 S m^-1 at f = 1 kHz). The improvement in the mechanical properties of the DN gel is attributed to the chain-entanglement crosslinking points introduced by SO₄^2- in the gelatin network and the electrostatic interaction crosslinking points introduced by Na⁺ in the gellan gum network. The high ionic conductivity of the DN gel is attributed to the infiltration of the DN gel in a salt solution of high concentration. The developed gellan gum/gelatin DN hydrogel has shown a new pathway towards strengthening natural-polymer-based DN hydrogels and towards potential applications in biomedical engineering and flexible electronic devices.

Catalyst-Free Crosslinking Modification of Nata-de-Coco-Based Bacterial Cellulose Nanofibres Using Citric Acid for Biomedical Applications

Bacterial cellulose (BC) has gained attention among researchers in materials science and bio-medicine due to its fascinating properties. However, BC’s fibre collapse phenomenon (i.e., its inability to reabsorb water after dehydration) is one of the drawbacks that limit its potential. To overcome this, a catalyst-free thermal crosslinking reaction was employed to modify BC using citric acid (CA) without compromising its biocompatibility. FTIR, XRD, SEM/EDX, TGA, and tensile analysis were carried out to evaluate the properties of the modified BC (MBC). The results confirm the fibre crosslinking phenomenon and the improvement of some properties that could be advantageous for various applications. The modified nanofibre displayed an improved crystallinity and thermal stability with increased water absorption/swelling and tensile modulus. The MBC reported here can be used for wound dressings and tissue scaffolding.

Development of dual crosslinked mumio-based hydrogel dressing for wound healing application: Physico-chemistry and antimicrobial activity

In this study, an antimicrobial mumio-based hydrogel dressing was developed for wound healing application. The mechanism of gel formation was achieved via a double crosslink network formation between gelatin (GT) and polyvinyl alcohol (PVA) using polyethylene glycol diglycidyl ether (PEGDE) and borax as crosslinking agents. To enhance the mechanical integrity of the hydrogel matrix, bacterial cellulose (BC) was integrated into the GT-PVA hydrogel to produce a composite gel dressing. The obtained hydrogel was characterized by FTIR, SEM, TGA, and XRD. Gel fraction, in vitro swelling and degradation as well as compressive modulus properties of the gel dressing were investigated as a function of change in PVA and BC ratios. By increasing the ratios of PVA and BC, the composite dressing showed lower swelling but higher mechanical strength. Comparing to other formulations, the gel with 4 %w/v PVA and 1 %w/v BC demonstrated to be most suitable in terms of stability and mechanical properties. In vitro cell cytotoxicity by MTT assay on human alveolar basal epithelial (A549) cell lines validated the gels as non-toxic. In addition, the mumio-based gel was compared to other formulations containing different bioactive agents of beeswax and cinnamon oil, which were tested for microbial growth inhibition effects against different bacteria (S. aureus and K. pneumoniae) and fungi (C. albicans and A. niger) strains. Results suggested that the gel dressing containing combinations of mumio, beeswax and cinnamon oil possess promising future in the inhibition of microbial infection supporting its application as a suitable dressing for wound healing.

Novel Diabetic Foot Wound Dressing Based on Multifunctional Hydrogels with Extensive Temperature-Tolerant, Durable, Adhesive, and Intrinsic Antibacterial Properties

Diabetic foot ulcers (DFUs) are hard-healing chronic wounds and susceptible to bacterial infection. Conventional hydrogel dressings easily lose water at high temperature or freeze at low temperature, making them unsuitable for long-term use or in extreme environments. Herein, a temperature-tolerant (-20 to 60 °C) antibacterial hydrogel dressing is fabricated by the assembly of polyacrylamide, gelatin, and ε-polylysine. Owing to the water/glycerin (Gly) binary solvent system, the resultant hydrogel (G-PAGL) displayed good heat resistance and antifreezing properties. Within the wide temperature range (-20 to 60 °C), all the desirable features of the hydrogel, including superstretchability (>1400%), enduring water retention, adhesiveness, and persistent antibacterial property, are quite stable. Remarkably, the hydrogel wound dressing displayed lasting and broad antibacterial activity against Gram-positive and Gram-negative bacteria. Satisfactorily, the double-network (DN) G-PAGL hydrogel dressing could effectively promote the healing of DFUs by accelerating collagen deposition, promoting angiogenesis, and inhibiting bacterial breed. As far as we know, this is the first time that the extensive temperature-tolerant DN hydrogel with antibacterial ability is developed to use as DFU wound dressing. The G-PAGL hydrogel provides more choices for DFU wound dressings that could be used in extreme environments.

Incorporation of Bioglass Improved the Mechanical Stability and Bioactivity of Alginate/Carboxymethyl Chitosan Hydrogel Wound Dressing

Recently, hydrogel wound dressings were popular in wound healing because of their advantages over traditional gauze dressings. The alginate/carboxymethyl chitosan (SA/CMCS) hydrogel wound dressing has been widely studied because of its biocompatibility and antibacterial ability. However, the poor mechanical stability and lack of bioactivity limit their applications. Bioglass (BG) has been well acknowledged as a bioactive material, and SA/BG hydrogels have been reported to be able to promote wound healing. Calcium ions released from BG can further cross-link SA, which may enhance the mechanical stability of the SA/CMCS hydrogels. Therefore, in this study, BG was incorporated into SA/CMCS hydrogel in order to obtain a bioactive alginate/CMCS/BG (SA/CMCS/BG) hydrogel wound dressing with improved mechanical stability. Results showed that the Young's modulus of SA/CMCS/BG hydrogel was three times higher than that of SA/CMCS hydrogel. In addition to better antibacterial and coagulation properties, SA/CMCS/BG hydrogels possess stronger bioactivity than SA/CMCS hydrogels as they could accelerate skin wound closure by regulating the host inflammation responses, stimulating angiogenesis, and enhancing collagen deposition in wound sites, which suggests that SA/CMCS/BG hydrogels are good candidates for clinic wound dressings.