On the characterization of sodium alginate/gelatine-based hydrogels for wound dressing

Three-dimensional bioprinting of tissue-engineered skin: Biomaterials, fabrication techniques, challenging difficulties, and future directions: A review

As an emerging new manufacturing technology, Three-dimensional (3D) bioprinting provides the potential for the biomimetic construction of multifaceted and intricate architectures of functional integument, particularly functional biomimetic dermal structures inclusive of cutaneous appendages. Although the tissue-engineered skin with complete biological activity and physiological functions is still cannot be manufactured, it is believed that with the advances in matrix materials, molding process, and biotechnology, a new generation of physiologically active skin will be born in the future. In pursuit of furnishing readers and researchers involved in relevant research to have a systematic and comprehensive understanding of 3D printed tissue-engineered skin, this paper furnishes an exegesis on the prevailing research landscape, formidable obstacles, and forthcoming trajectories within the sphere of tissue-engineered skin, including: (1) the prevalent biomaterials (collagen, chitosan, agarose, alginate, etc.) routinely employed in tissue-engineered skin, and a discerning analysis and comparison of their respective merits, demerits, and inherent characteristics; (2) the underlying principles and distinguishing attributes of various current printing methodologies utilized in tissue-engineered skin fabrication; (3) the present research status and progression in the realm of tissue-engineered biomimetic skin; (4) meticulous scrutiny and summation of the extant research underpinning tissue-engineered skin inform the identification of prevailing challenges and issues.

Construction of gelatin/alginate hydrogels doped hemicyanine derivatives for photodynamic antibacterial application

Hydrogel systems based on natural polymer materials have provided alternative opportunities for preparing antimicrobial dressings. A composite antibacterial hydrogel system containing gelatin (Gel), alginate (Alg) and hemicyanine derivatives with different chain lengths (C3, C6 and C10) was constructed. The composite hydrogels have excellent swelling ability and low degradability due to the classical three-dimensional network structure. Because of the photosensitization ability of C3, C6 and C10, hydrogels containing these molecules can also effectively produce reactive oxygen species (ROS) under light. Importantly, the hydrogel containing C3 molecules that have higher spatial extension structure and shorter alkyl chain than C6 and C10 shows better photo-responsive antibacterial effect against drug-resistant Escherichia coli. The bacterial killing activity of the composite hydrogel system could be regulated by changing the alkyl chain length of the photosensitizers. This effective and photo-responsive composite hydrogel system is expected to be used for bacteria-infected wound repair and promoting wound healing.

Emerging horizons and prospects of polysaccharide-constructed gels in the realm of wound healing

Polysaccharides, with the abundant availability, biodegradability, and inherent safety, offer a vast array of promising applications. Leveraging the remarkable attributes of polysaccharides, biomimetic and multifunctional hydrogels have emerged as a compelling avenue for efficacious wound dressing. The gels emulate the innate extracellular biomatrix as well as foster cellular proliferation. The distinctive structural compositions and profusion of functional groups within polysaccharides confer excellent physical/chemical traits as well as distinct restorative involvements. Gels crafted from polysaccharide matrixes serve as a robust defense against bacterial threats, effectively shielding wounds from harm. This comprehensive review delves into wound physiology, accentuating the significance of numerous polysaccharide-based gels in the wound healing context. The discourse encompasses an exploration of polysaccharide hydrogels tailored for diverse wound types, along with an examination of various therapeutic agents encapsulated within hydrogels to facilitate wound repair, incorporating recent patent developments. Within the scope of this manuscript, the perspective of these captivating gels for promoting optimal healing of wounds is vividly depicted. Nevertheless, the pursuit of knowledge remains ongoing, as further research is warranted to bioengineer progressive polysaccharide gels imbued with adaptable features. Such endeavors hold the promise of unlocking substantial potential within the realm of wound healing, propelling us toward multifaceted and sophisticated solutions.

Marine-derived polysaccharides and their therapeutic potential in wound healing application - A review

Polysaccharides originating from marine sources have been studied as potential material for use in wound dressings because of their desirable characteristics of biocompatibility, biodegradability, and low toxicity. Marine-derived polysaccharides used as wound dressing, provide several benefits such as promoting wound healing by providing a moist environment that facilitates cell migration and proliferation. They can also act as a barrier against external contaminants and provide a protective layer to prevent further damage to the wound. Research studies have shown that marine-derived polysaccharides can be used to develop different types of wound dressings such as hydrogels, films, and fibres. These dressings can be personalised to meet specific requirements based on the type and severity of the wound. For instance, hydrogels can be used for deep wounds to provide a moist environment, while films can be used for superficial wounds to provide a protective barrier. Additionally, these polysaccharides can be modified to improve their properties, such as enhancing their mechanical strength or increasing their ability to release bioactive molecules that can promote wound healing. Overall, marine-derived polysaccharides show great promise for developing effective and safe wound dressings for various wound types.

Adsorptive removal of Safranine T dye from aqueous solutions using sodium alginate-Festuca arundinacea seeds bio-composite microbeads

In this study, composite microbeads were prepared using Festuca arundinacea seeds and sodium alginate biopolymer at different ratios and utilized as sorbents for the sorption of Safranine T from wastewater. The sorbents were characterized by FTIR, SEM, XRD, and BET analysis. According to BET analysis, the specific surface area of the adsorbents was calculated to be 10.99 m2/g and the surface was found to be mesoporous. The optimum conditions for adsorption studies including initial pH (2-12), concentration (10-50 mg/L), contact time (0-150 min), and adsorbent mass (0.05 g/50 mL-0.25 g/50 mL) were determined at 25 °C. The raw data obtained from sorption tests were applied to Freundlich, Langmuir-1, Langmuir-2, Langmuir-3, Langmuir-4, Temkin, Toth, and Koble-Corrigan isotherm models. The best results were obtained from the Langmuir-2 and accordingly the qm values were calculated as 454.54, 833.33, and 625.00 mg/g for FA, FA-SA-20, and FA-SA-30 at 25 °C, respectively. Adsorption kinetic data illustrated that the process followed the PSO model. Reusability and desorption studies were performed for composite microbeads. Additionally, the thermodynamic studies were performed at 25, 35 and 45 °C. Considering all these results, it was seen that the FA-SA-20 composite had the highest adsorption capacity and the best desorption efficiency.

Development and Characterization of Bio-Based Composite Films for Food Packing Applications Using Boiled Rice Water and Pistacia vera Shells

Customer demand for natural packaging materials in the food industry has increased. Biocomposite films developed using boiled rice water could be an eco-friendly and cost-effective packaging product in the future. This study reports the development of bio-based films using waste materials, such as boiled rice water (matrix) and Pistacia vera shells (reinforcement material), using an adapted solution casting method. Several film combinations were developed using various concentrations of plasticizing agent (sorbitol), thickening agent (oil and agar), and stabilizing agents (Arabic gum, corn starch, and Pistacia vera shell powder). Various packaging properties of the film were analyzed and examined to select the best bio-based film for food packaging applications. The film fabricated with Pistacia vera shell powder in the biocomposite film exhibited a reduced water solubility, swelling index, and moisture content, as compared to polyethene packaging material, whereas the biocomposite film exhibited poor antimicrobial properties, high vapor transmission rate, and high biodegradability rate. The packaging properties and characterization of the film indicated that the boiled rice water film with Pistacia vera shell powder was suitable for packaging material applications.

Composite material consisting of microporous beta-TCP ceramic and alginate-dialdehyde-gelatin for controlled dual release of clindamycin and bone morphogenetic protein 2

The aim of this study was to produce a composite of microporous β-TCP filled with alginate-gelatin crosslinked hydrogel, clindamycin and bone morphogenetic protein (BMP-2) to prolong the drug-release behaviour for up to 28 days. The most promising alginate-di-aldehyde(ADA)-gelatin gel for drug release from microcapsules was used to fill microporous β-TCP ceramics under directional flow in a special loading chamber. Dual release of clindamycin and BMP-2 was measured on days 1, 2, 3, 6, 9, 14, 21 and 28 by high performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA). After release, the microbial efficacy of the clindamycin was checked and the biocompatibility of the composite was tested in cell culture. Clindamycin and the model substance FITC-protein A were released from microcapsules over 28 days. The clindamycin burst release was 43 ± 1%. For the loaded ceramics, a clindamycin release above the minimal inhibitory concentration (MIC) until day 9 and a burst release of 90.56 ± 2.96% were detected. BMP-2 was released from the loaded ceramics in low concentrations over 28 days. The release of active substances from β-TCP and hydrogel have already been extensively studied. Directional flow loading is a special procedure in which the ceramic could act as a stabilizer in the bone and, as a biodegradable system, enables a single-stage surgical procedure. Whether ADA-gelatin gel is suitable for this procedure as a more biodegradable alternative to pure alginate or whether a dual release is possible in this composite has not yet been investigated.

A Review of Metal Nanoparticles Embedded in Hydrogel Scaffolds for Wound Healing In Vivo

An evolving field, nanotechnology has made its mark in the fields of nanoscience, nanoparticles, nanomaterials, and nanomedicine. Specifically, metal nanoparticles have garnered attention for their diverse use and applicability to dressings for wound healing due to their antimicrobial properties. Given their convenient integration into wound dressings, there has been increasing focus dedicated to investigating the physical, mechanical, and biological characteristics of these nanoparticles as well as their incorporation into biocomposite materials, such as hydrogel scaffolds for use in lieu of antibiotics as well as to accelerate and ameliorate healing. Though rigorously tested and applied in both medical and non-medical applications, further investigations have not been carried out to bring metal nanoparticle-hydrogel composites into clinical practice. In this review, we provide an up-to-date, comprehensive review of advancements in the field, with emphasis on implications on wound healing in in vivo experiments.

Mechanical Properties of Alginate Hydrogels Cross-Linked with Multivalent Cations

Ionically, cross-linked alginate gels have a potential to be used in a wide range of biomedical, environmental and catalytic applications. The study deals with preparation of alginate hydrogels cross-linked with various cations and the analysis of their equilibrium swelling and mechanical properties. It is shown that the type of cations used in the cross-linking process affects the elastic moduli and the equilibrium degree of swelling of the gels. The experimental data in small-amplitude oscillatory tests are fitted with a model that involves two material parameters: the elastic modulus of a polymer network and a measure of its inhomogeneity. The influence of cations on these quantities is studied numerically. It is revealed that the dependence of the elastic modulus of ionically cross-linked alginate gels on their equilibrium degree of swelling differs from that predicted by the conventional theory for covalently cross-linked gels.

Moisture-Adaptive Contractile Biopolymer-Derived Fibers for Wound Healing Promotion

The advancement in thermosensitive active hydrogels has opened promising opportunities to dynamic full-thickness skin wound healing. However, conventional hydrogels lack breathability to avoid wound infection and cannot adapt to wounds with different shapes due to the isotropic contraction. Herein, a moisture-adaptive fiber that rapidly absorbs wound tissue fluid and produces a large lengthwise contractile force during the drying process is reported. The incorporation of hydroxyl-rich silica nanoparticles in the sodium alginate/gelatin composite fiber greatly improves the hydrophilicity, toughness, and axial contraction performance of the fiber. This fiber exhibits a dynamic contractile behavior as a function of humidity, generating ≈15% maximum contraction strain or ≈24 MPa maximum isometric contractile stress. The textile knitted by the fibers features excellent breathability and generates adaptive contraction in the target direction during the natural desorption of tissue fluid from the wounds. In vivo animal experiments further demonstrate the advantages of the textiles over traditional dressings in accelerating wound healing.

Alginate-Based Hydrogels and Scaffolds for Biomedical Applications

Alginate is a natural polymer of marine origin and, due to its exceptional properties, has great importance as an essential component for the preparation of hydrogels and scaffolds for biomedical applications. The design of biologically interactive hydrogels and scaffolds with advanced, expected and required properties are one of the key issues for successful outcomes in the healing of injured tissues. This review paper presents the multifunctional biomedical applications of alginate-based hydrogels and scaffolds in selected areas, highlighting the key effect of alginate and its influence on the essential properties of the selected biomedical applications. The first part covers scientific achievements for alginate in dermal tissue regeneration, drug delivery systems, cancer treatment, and antimicrobials. The second part is dedicated to our scientific results obtained for the research opus of hydrogel materials for scaffolds based on alginate in synergy with different materials (polymers and bioactive agents). Alginate has proved to be an exceptional polymer for combining with other naturally occurring and synthetic polymers, as well as loading bioactive therapeutic agents to achieve dermal, controlled drug delivery, cancer treatment, and antimicrobial purposes. Our research was based on combinations of alginate with gelatin, 2-hydroxyethyl methacrylate, apatite, graphene oxide and iron(III) oxide, as well as curcumin and resveratrol as bioactive agents. Important features of the prepared scaffolds, such as morphology, porosity, absorption capacity, hydrophilicity, mechanical properties, in vitro degradation, and in vitro and in vivo biocompatibility, have shown favorable properties for the aforementioned applications, and alginate has been an important link in achieving these properties. Alginate, as a component of these systems, proved to be an indispensable factor and played an excellent “role” in the optimal adjustment of the tested properties. This study provides valuable data and information for researchers and demonstrates the importance of the role of alginate as a biomaterial in the design of hydrogels and scaffolds that are powerful medical “tools” for biomedical applications.

Nanofibrous Vildagliptin/PLGA Membranes Accelerate Diabetic Wound Healing by Angiogenesis

The inhibition of dipeptidyl peptidase-4 (DPP4) significantly enhances the wound closure rate in diabetic patients with chronic foot ulcers. DPP4 inhibitors are only prescribed for enteral, but topical administration, if feasible, to a wound would have more encouraging outcomes. Nanofibrous drug-eluting poly-D-L-lactide-glycolide (PLGA) membranes that sustainably release a high concentration of vildagliptin were prepared to accelerate wound healing in diabetes. Solutions of vildagliptin and PLGA in hexafluoroisopropanol were electrospun into nanofibrous biodegradable membranes. The concentration of the drug released in vitro from the vildagliptin-eluting PLGA membranes was evaluated, and it was found that effective bioactivity of vildagliptin can be discharged from the nanofibrous vildagliptin-eluting membranes for 30 days. Additionally, the electrospun nanofibrous PLGA membranes modified by blending with vildagliptin had smaller fiber diameters (336.0 ± 69.1 nm vs. 743.6 ± 334.3 nm, p < 0.001) and pore areas (3405 ± 1437 nm2 vs. 8826 ± 4906 nm2, p < 0.001), as well as a higher hydrophilicity value (95.2 ± 2.2° vs. 113.9 ± 4.9°, p = 0.004), and showed a better water-retention ability within 24 h compared with PLGA membranes. The vildagliptin-eluting PLGA membrane also enhanced the diabetic wound closure rate for two weeks (11.4 ± 3.0 vs. 18.7 ± 2.6 %, p < 0.001) and the level of the angiogenesis using CD31 expression (1.73 ± 0.39 vs. 0.45 ± 0.17 p = 0.006 for Western blot; 2.2 ± 0.5 vs. 0.7 ± 0.1, p < 0.001 for immunofluorescence). These results demonstrate that nanofibrous drug-eluting PLGA membranes loaded with vildagliptin are an effective agent for sustained drug release and, therefore, for accelerating cutaneous wound healing in the management of diabetic wounds.

Preparation of Ion2+-COS/SA Multifunctional Gel Films for Skin Wound Healing by an In Situ Spray Method

The rapid preparation of safe and efficient wound dressings that meet the needs of the entire repair process remains a major challenge for effective therapeutic wound healing. Natural, sprayable Ion²⁺-COS/SA multifunctional dual-network gel films created by the in situ coordination of chitooligosaccharide (COS), metal ions and sodium alginate (SA) using casting and an in-situ spray method were synthesized. The gel films exhibited excellent physicochemical properties such as swelling, porosity and plasticity at a COS mass fraction of 3%. Furthermore, at this mass fraction, the addition of bimetallic ions led to the display of multifunctional properties, including significant antioxidant, antibacterial and cytocompatibility properties. In addition, experiments in a total skin defect model showed that this multifunctional gel film accelerates wound healing and promotes skin regeneration. These results suggest that the sprayable Ion²⁺-COS/SA multifunctional pro-healing gel film may be a promising candidate for the clinical treatment of allodermic wounds.

Effects of poly(vinyl alcohol) blending with Ag/alginate solutions to form nanocomposite fibres for potential use as antibacterial wound dressings

In this work, nanocomposite fibres and microfibres based on alginate and poly(vinyl alcohol) (PVA) with silver nanoparticles (AgNPs) were produced and characterized for potential application as antibacterial wound dressings. PVA/Ag/Na-alginate colloid solution was used for the preparation of the fibres by a simple extrusion technique followed by freezing-thawing cycles. UV-Visible spectroscopy confirmed successful preservation of AgNPs in fibres while Fourier transform infrared spectroscopy has shown a balanced combined effect on the Ca-alginate spatial arrangement with the addition of both AgNPs and PVA. The presence of PVA in fibres induced an increase in the swelling degree as compared with that of Ag/Ca-alginate fibres (approx. 28 versus approx. 14). Still, the initially produced PVA/Ca-alginate fibres were mechanically weaker than Ca-alginate fibres, but after drying and rehydration exhibited better mechanical properties. Also, the obtained fibres released AgNPs and/or silver ions at the concentration of approximately 2.6 µg cm^-3 leading to bacteriostatic effects against Staphylococcus aureus and Escherichia coli. These results are relevant for practical utilization of the fibres, which could be stored and applied in the dry form with preserved mechanical stability, sorption capacity and antibacterial activity.

Evaluation of the Performance of a ZnO-Nanoparticle-Coated Hydrocolloid Patch in Wound Healing

Hydrocolloid dressings are an important method for accelerating wound healing. A combination of a hydrocolloid and nanoparticles (NPs), such as gold (Au), improves the wound healing rate, but Au-NPs are expensive and unable to block ultraviolet (UV) light. Herein, we combined zinc oxide nanoparticles (ZnO-NPs) with hydrocolloids for a less expensive and more effective UV-blocking treatment of wounds. Using Sprague-Dawley rat models, we showed that, during 10-day treatment, a hydrocolloid patch covered with ZnO-NPs (ZnO-NPs-HC) macroscopically and microscopically stimulated the wound healing rate and improved wound healing in the inflammation phase as shown by reducing of pro-inflammatory cytokines (CD68, IL-8, TNF-α, MCP-1, IL-6, IL-1β, and M1) up to 50%. The results from the in vitro models (RAW264.7 cells) also supported these in vivo results: ZnO-NPs-HCs improved wound healing in the inflammation phase by expressing a similar level of pro-inflammatory mediators (TNF-α and IL-6) as the negative control group. ZnO-NPs-HCs also encouraged the proliferation phase of the healing process, which was displayed by increasing expression of fibroblast biomarkers (α-SMA, TGF-β3, vimentin, collagen, and M2) up to 60%. This study provides a comprehensive analysis of wound healing by measuring the biomarkers in each phase and suggests a cheaper method for wound dressing.

SA/G hydrogel containing NRF2-engineered HEK-293-derived CM improves wound healing efficacy of WJ-MSCs in a rat model of excision injury

AIM OF THE STUDY

Skin wounds are a major public health issue due to the lack of real effective remedies. Mesenchymal stem cells (MSCs) are considered as a promising therapeutic strategy for wound injuries; however, low survival rate following transplantation limited their application. In an attempt to introduce a novel potential wound dressing and improve wound healing properties, the current study was conducted.

MATERIAL AND METHODS

we prepared conditioned medium (CM) harvested from HEK-293 cells overexpressing nuclear factor erythroid 2-related factor 2 (NRF2), a master regulator of antioxidant genes expression. Then, the CM was loaded in a biodegradable hydrogel. Next, in an animal model of full-thickness excision wound, wharton's jelly derived-mesenchymal stem cells (WJ-MSCs) were transplanted at the margins of the wound followed by application of the hydrogel on injury site. Finally, wound healing characteristics were evaluated by proper methods.

RESULTS

Our findings revealed that, the NRF2-CM protected the WJ-MSCs against H₂O₂-induced toxicity in vitro. Furthermore, in vivo results showed that, SA/G hydrogel containing NRF2-CM significantly (P < 0.01) promoted WJ-MSCs survival, increased angiogenesis, accelerated wound contraction, and promoted wound healing compared to other groups.

CONCLUSION

Though further preclinical and clinical studies regarding mechanisms behind the protection and also safety of the strategy are needed, our findings strongly suggest that the prepared wound dressing enhanced the efficacy of therapeutic potential of WJ-MSCs by providing an enriched/antioxidant niche support.

Methotrexate-Loaded Gelatin and Polyvinyl Alcohol (Gel/PVA) Hydrogel as a pH-Sensitive Matrix

The aim was to formulate and evaluate Gel/PVA hydrogels as a pH-sensitive matrix to deliver methotrexate (MTX) to colon. The primed Gel/PVA hydrogels were subjected to evaluation for swelling behavior, diffusion coefficient, sol-gel characteristic and porosity using an acidic (pH 1.2) and phosphate buffer (PBS) (pH 6.8 & pH 7.4) media. Fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA) were performed to evaluate the chemical compatibility of the Gel/PVA hydrogel. The shape alteration and release of Gel/PVA hydrogel was conducted at pH 1.2, pH 6.8 and pH 7.4. The drug release kinetic mechanism was determined using various kinetic equations. The physicochemical evaluation tests and drug release profile results were found to be significant (p < 0.01). However, it was dependent on the polymers' concentration, the pH of the release media and the amount of the cross-linking agent. Hydrogels containing the maximum amount of gel showed a dynamic equilibrium of 10.09 ± 0.18 and drug release of 93.75 ± 0.13% at pH 1.2. The kinetic models showed the release of MTX from the Gel/PVA hydrogel was non-Fickian. The results confirmed that the newly formed Gel/PVA hydrogels are potential drug delivery systems for a controlled delivery of MTX to the colon.

Freeze vs. Spray Drying for Dry Wild Thyme (Thymus serpyllum L.) Extract Formulations: The Impact of Gelatin as a Coating Material

Freeze drying was compared with spray drying regarding feasibility to process wild thyme drugs in order to obtain dry formulations at laboratory scale starting from liquid extracts produced by different extraction methods: maceration and heat-, ultrasound-, and microwave-assisted extractions. Higher total powder yield (based on the dry weight prior to extraction) was achieved by freeze than spray drying and lower loss of total polyphenol content (TPC) and total flavonoid content (TFC) due to the drying process. Gelatin as a coating agent (5% w/w) provided better TPC recovery by 70% in case of lyophilization and higher total powder yield in case of spray drying by diminishing material deposition on the wall of the drying chamber. The resulting gelatin-free and gelatin-containing powders carried polyphenols in amount ~190 and 53–75 mg gallic acid equivalents GAE/g of powder, respectively. Microwave-assisted extract formulation was distinguished from the others by a higher content of polyphenols, proteins and sugars, higher bulk density and lower solubility. The type of the drying process mainly affected the position of the gelatin-derived -OH and amide bands in FTIR spectra. Spray-dried formulations compared to freeze-dried expressed higher thermal stability as confirmed by differential scanning calorimetry analysis and a higher diffusion coefficient; the last feature can be associated with the lower specific surface area of irregularly shaped freeze-dried particles (151–223 µm) compared to small microspheres (~8 µm) in spray-dried powder.

Highly absorbent hydrogels comprised from interpenetrated networks of alginate-polyurethane for biomedical applications

Developing new approaches to improve the swelling, degradation rate, and mechanical properties of alginate hydrogels without compromising their biocompatibility for biomedical applications represents a potential area of research. In this work, the generation of interpenetrated networks (IPN) comprised from alginate-polyurethane in an aqueous medium is proposed to design hydrogels with tailored properties for biomedical applications. Aqueous polyurethane (PU) dispersions can crosslink and interpenetrate alginate chains, forming amide bonds that allow the structure and water absorption capacity of these novel hydrogels to be regulated. In this sense, this work focuses on studying the relation of the PU concentration on the properties of these hydrogels. The results indicate that the crosslinking of the alginate with PU generates IPN hydrogels with a crystalline structure characterized by a homogeneous smooth surface with high capacity to absorb water, tailoring the degradation rate, thermal decomposition, and storage module, not altering the native biocompatibility of alginate, providing character to inhibit the growth of E. coli and increasing also its hemocompatibility. The IPN hydrogels that include 20 wt.% of PU exhibit a reticulation index of 46 ± 4%, swelling capacity of 545 ± 13% at 7 days of incubation at physiological pH, resistance to both acidic and neutral hydrolytic degradation, mechanical improvement of 91 ± 1%, and no cytotoxicity for monocytes and fibroblasts growing for up to 72 h of incubation. These results indicate that these novel hydrogels can be used for successful biomedical applications in the design of wound healing dressings.

Alginate and its application to tissue engineering

Alginate is a polysaccharide of natural origin, which shows outstanding properties of biocompatibility, gel forming ability, non-toxicity, biodegradability and easy to process. Due to these excellent properties of alginate, sodium alginate, a hydrogel form of alginate, oxidized alginate and other alginate based materials are used in various biomedical fields, especially in drug delivery, wound healing and tissue engineering. Alginate can be easily processed as the 3D scaffolding materials which includes hydrogels, microcapsules, microspheres, foams, sponges, and fibers and these alginate based bio-polymeric materials have particularly used in tissue healing, healing of bone injuries, scars, wound, cartilage repair and treatment, new bone regeneration, scaffolds for the cell growth. Alginate can be easily modified and blended by adopting some physical and chemical processes and the new alginate derivative materials obtained have new different structures, functions, and properties having improved mechanical strength, cell affinity and property of gelation. This can be attained due to combination with other different biomaterials, chemical and physical crosslinking, and immobilization of definite ligands (sugar and peptide molecules). Hence alginate, its modified forms, derivative and composite materials are found to be more attractive towards tissue engineering. This article provides a comprehensive outline of properties, structural aspects, and application in tissue engineering.

Marine Algae Polysaccharides as Basis for Wound Dressings, Drug Delivery, and Tissue Engineering: A Review

The present review considers the physicochemical and biological properties of polysaccharides (PS) from brown, red, and green algae (alginates, fucoidans, carrageenans, and ulvans) used in the latest technologies of regenerative medicine (tissue engineering, modulation of the drug delivery system, and the design of wound dressing materials). Information on various types of modern biodegradable and biocompatible PS-based wound dressings (membranes, foams, hydrogels, nanofibers, and sponges) is provided; the results of experimental and clinical trials of some dressing materials in the treatment of wounds of various origins are analyzed. Special attention is paid to the ability of PS to form hydrogels, as hydrogel dressings meet the basic requirements set out for a perfect wound dressing. The current trends in the development of new-generation PS-based materials for designing drug delivery systems and various tissue-engineering scaffolds, which makes it possible to create human-specific tissues and develop target-oriented and personalized regenerative medicine products, are also discussed.

Alginate-based hydrogels as drug delivery vehicles in cancer treatment and their applications in wound dressing and 3D bioprinting

Hydrogels are a three-dimensional and crosslinked network of hydrophilic polymers. They can absorb a large amount of water or biological fluids, which leads to their swelling while maintaining their 3D structure without dissolving (Zhu and Marchant, Expert Rev Med Devices 8:607-626, 2011). Among the numerous polymers which have been utilized for the preparation of the hydrogels, polysaccharides have gained more attention in the area of pharmaceutics; Sodium alginate is a non-toxic, biocompatible, and biodegradable polysaccharide with several unique physicochemical properties for which has used as delivery vehicles for drugs (Kumar Giri et al., Curr Drug Deliv 9:539-555, 2012). Owing to their high-water content and resembling the natural soft tissue, hydrogels were studied a lot as a scaffold. The formation of hydrogels can occur by interactions of the anionic alginates with multivalent inorganic cations through a typical ionotropic gelation method. However, those applications require the control of some properties such as mechanical stiffness, swelling, degradation, cell attachment, and binding or release of bioactive molecules by using the chemical or physical modifications of the alginate hydrogel. In the current review, an overview of alginate hydrogels and their properties will be presented as well as the methods of producing alginate hydrogels. In the next section of the present review paper, the application of the alginate hydrogels will be defined as drug delivery vehicles for chemotherapeutic agents. The recent advances in the application of the alginate-based hydrogels will be describe later as a wound dressing and bioink in 3D bioprinting.

Formulation of alginate based hydrogel from brown seaweed, Turbinaria conoides for biomedical applications

Sodium Alginate (SA) is an excellent carrier in various drug delivery systems. In this study, SA was synthesized from brown seaweed, Turbinaria conoides with a yield of 31.3 ± 0.86%. The analysis of physicochemical properties of extracted alginate (ALG) determined its purity. The structural confirmations of ALG were studied through FTIR, XRD and SEM analysis. Formulation of ALG with collagen (COL) as a wound healing microfilm showed potential anti-inflammatory properties (81.3 ± 1.77%) and sustained drug release. Likewise, the ALG microbead encapsulated with an anticancer drug, Tamoxifen indicated an in vitro sustained release in the range of 62 ± 0.70% - 91 ± 0.56%. The overall swelling behavior of both the hydrogels, microfilm and microbead provides new opportunities for development of natural ALG in this therapeutic era.

Recent Advances in the Use of Algal Polysaccharides for Skin Wound Healing

BACKGROUND

Chronic skin wounds and pressure ulcers represent major health care problems in diabetic individuals, as well as patients who suffered a spinal cord injury. Current treatment methods are only partially effective and such wounds exhibit a high recurrence rate. Open wounds are at high risk of invasive wound infections, which can lead to amputation and further disability. An interdisciplinary approach is needed to develop new and more effective therapies.

METHODS

The purpose of this work is to review recent studies focusing on the use of algal polysaccharides in commercially available as well as experimental wound dressings. Studies that discuss wound dressings based on algal polysaccharides, some of which also contain growth factors and even living cells, were identified and included in this review.

RESULTS AND CONCLUSION

Algal polysaccharides possess mechanical and physical properties, along with excellent biocompatibility and biodegradability that make them suitable for a variety of applications as wound dressings. Furthermore, algal polysaccharides have been used for a dual purpose, namely as wound covering, but also as a vehicle for drug delivery to the wound site.

Recent advancements in biopolymer and metal nanoparticle-based materials in diabetic wound healing management

Currently, diabetes mellitus (DM) accelerated diabetic foot ulcer (DFU) remains vivacious health problem related with delayed healing and high amputation rates which leads to enormous clinical obligation. Keeping in view of the foregoing, researchers have been made in their efforts to develop novel materials which accelerate delayed wound healing in the diabetic patient and reduce the adversative influences of DFUs. The most prominent materials used for the wound healing application have biocompatibility, low cytotoxicity, excellent biodegradable properties, and antimicrobial activity properties. Utilization of nanoparticles has emerged as a protruding scientific and technological revolution in controlling DFUs. Biopolymers in combination with bioactive nanoparticles having antimicrobial, antibacterial, and anti-inflammatory properties have great potential in wound care to enhance the healing process of diabetic wound infectious. Combination of antibacterial nanoparticles like silver nanoparticles (AgNPs), gold nanoparticles (AuNPs), copper nanoparticles (CuNPs) etc. with polymeric matrix could efficiently inhibit bacterial growth and at the same time fastens the healing process of a wound. This review briefed the recent development of different natural polymers and antibacterial nanoparticles to mitigate the diabetes mellitus based DFU.

Wet electrospun alginate/gelatin hydrogel nanofibers for 3D cell culture

Convergence of biological and biofabrication approaches is necessary to progress new biomaterials promoting three-dimensional (3D) cell growth and maturation towards tissue regeneration and integration. Here, we have developed a novel approach to fabricate 3D macroporous, alginate/gelatin hydrogel nanofibers (Alg/GelF-MA), which provide superior cell adhesion, motility, proliferation and maturation. The electrospinning process greatly depends on the ionic strength and viscoelastic behavior of the solution. The polyelectrolyte nature of alginate favors intramolecular bundles over intermolecular entanglement, which hinders its electrospinnability. Electrospinning of alginate was achieved by the aid of a supporting polymer, polyethylene oxide and a surfactant, Pluronic®F127. Furthermore, the Ca²⁺-mediated coagulation process of alginate was realized in situ during wet electrospinning, where the rapid physical crosslink-ability of alginate was applied in conjunction with the jet entrance into the wet electrospinning collector, a coagulation bath. Consequently, the rapid formation of Ca²⁺-alginate complex stabilized the nanofiber morphology. The low surface tension of the non-solvent ethanol used in the bath prevented fibers from dense packing, thus allowing the generation of 3D macroporous structure favoring cell motility. The subsequent UV-mediated chemical crosslinking further stabilized the gelatin content in the Alg/GelF-MA hydrogel nanofibers. It is demonstrated that the Alg/GelF-MA nanofibers with low cytotoxicity (below 10%) supported an over 8-fold proliferation of mesenchymal stem cells over 5 weeks and supported the maturation of human iPSC-derived ventricular cardiomyocytes, which significantly outperform the cell encapsulated bulk GelF-MA hydrogel. The work provides an insight for rational design and development of 3D cell culture matrix for advancement of stem cell therapy and tissue regeneration.

Alginate-based hydrogels functionalised at the nanoscale using layer-by-layer assembly for potential cartilage repair

Injuries to articular cartilage are frequently difficult to repair, in part because of the poor regenerative capacity of this tissue. To date, no successful system for complete regeneration of the most challenging cartilage defects has been demonstrated. The aim of this work was to develop functionalised hydrogels at the nanoscale by Layer-by-Layer (LbL) assembly to promote cartilage healing. Hydrogels, based on sodium alginate (NaAlg) and gelatin (G), were prepared by an external gelation method consisting of CaCl₂ diffusion and genipin addition for G crosslinking. Successively, hydrogels were coated with G to obtain a positive charge on the surface, then functionalised by LbL assembly to create 16 nanolayers, based on poly(styrene sulfonate)/poly(allyl amine) (PSS/PAH), including a specific peptide sequence (CTATVHL) and transforming growth factors β1 (TGF-β1). Physico-chemical properties were evaluated by XPS, ATR-FTIR and rheological analyses while in vitro cytocompatibility was studied using bovine articular chondrocytes (BAC). XPS spectra showed N_1s and S_2p peaks, indicating that PAH and PSS have been introduced with success. ATR-FTIR indicated the specific PAH and PSS absorption peaks. Finally, the biomolecule incorporation influenced positively the processes of BAC adhesion and proliferation, and glycosamynoglycan secretion. The functionalised alginate-based hydrogels described here are ideally suited to chondral regeneration in terms of their integrity, stability, and cytocompatibility.

Alginate in Wound Dressings

Alginate is a biopolymer used in a variety of biomedical applications due to its favourable properties, such as biocompatibility and non-toxicity. It has been particularly attractive in wound healing applications to date. It can be tailored to materials with properties suitable for wound healing. Alginate has been used to prepare different forms of materials for wound dressings, such as hydrogels, films, wafers, foams, nanofibres, and in topical formulations. The wound dressings prepared from alginate are able to absorb excess wound fluid, maintain a physiologically moist environment, and minimize bacterial infections at the wound site. The therapeutic efficacy of these wound dressings is influenced by the ratio of other polymers used in combination with alginate, the nature of cross linkers used, the time of crosslinking, nature of excipients used, the incorporation of nanoparticles, and antibacterial agents. This review provides a comprehensive overview of the different forms of wound dressings containing alginate, in vitro, and in vivo results.